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BASIC ENDODONTIC INSTRUMENTS INTRODUCTION HISTORY : After years of relative inactivity, a remarkable upsurge in endodontic instrument design and refinement has recently developed. Historically, very little was done to improve the quality or standardization of instruments until the 1950’s when two research groups started that went into hand instruments. After the introduction of standardized instruments, the only changes made were the universal use of stainless steel rather than the carbon steel, and the addition of smaller (N0. 6 and No. 8) and larger (No.110 to 140) sizes as well as color coding and the re-emergence of power driven instruments. ENDODONTIC INSTRUMENT STANDARDIZATION : Before 1958, endodontic instruments were manufactured without benefit of any established criteria. Beginning in 1955 a serious attempt was made to correct these abuses, and in 1959, a new line of standardized instruments and filling materials was introduced into profession. 1) A formula for the diameter and taper in each size of instrument and filling material was agreed on. 2) A formula for a graduated increment in size from one instrument to the next was developed. 3) A new instrument numbering system based on instrument metric diameter was established. This numbering system, last revised in 2002 using numbers from 5 to 140, was not just arbitrary but was based on the diameter of the instruments in hundredths of a millimeter at the beginning of the tip. In 1959, ingle and Levine using an electron microscope found variations in diameter and taper for same size instruments and suggested a definite increment in diameter as the size progressed while maintaining the constant taper of all blades regardless of size. RECOMMENDATIONS OF INGLE AND LEVINE : 1) Instruments shall be numbered from 10 to 100, then to advance by 5 units from 10 to 60 and then by 10 units to 100 size. 2) Each number shall be representative of the diameter of the instrument in hundredths of millimeter at the tip. Eg: No.10 is

or 0.1 mm diameter at tip.

10 (flutes) shall begin at the tip and extend exactly 16 mm up the shaft. 3) The working blade 100

4) The tip of the blade is designated as “D1”. This D1 represents the number of the instrument. 5) The 16 mm up the shaft from the tip is designated as “D 2”. The diameter at D2 will be 0.32 mm greater than D1. 6) There is a constant increase of the taper from D 1 to D2 by 0.02 mm per mm for every instrument regardless of the size. Eg: No. 20 reamer


D1 is 0.20 mm D2 is 0.20 + 0.32 = 0.52 mm. Other specifications added later : 7) The tip angle of an instrument sizes should be 75 Âą 150 8) Instrument sizes should increase by 0.05 mm at D1 between Nos. 10 and 60 Eg: No. 10, 15, 20, 25 9) Instruments should increase by 0.1 mm from Nos. 60 to 150 Eg: No. 60, 70, 80. 10)

No. 6 and 8 have been added for the increased instrument selection.

11)

Instrument handles have been color coded for easier recognition.

SPECIFICATION OF FILES AND REAMERS : Old number 000 00 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 -

Color code Pink Gray Purple White Yellow Red Blue Green Black White Yellow Red Blue Green Black White Yellow Red Blue Green Black White

New number 6 8 10 15 20 25 30 35 40 45 50 55 60 70 80 90 100 110 120 130 140 150

D1 (mm) 0.06 0.08 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 1.40 1.50

D2 (mm) 0.38 0.40 0.42 0.47 0.52 0.57 0.62 0.67 0.72 0.77 0.82 0.87 0.92 1.02 1.12 1.22 1.32 1.42 1.52 1.62 1.72 1.82


Instruments are available in lengths of 21, 25, 28 and 30 mm. Ordinarily instruments 25 mm long are used, but occasionally, 21 mm instruments are needed for molars, especially when the patient cannot open mouth wide. 28 and 30 mm instruments are necessary for cuspids and other teeth in which 25 mm cannot reach the apical foramen. Reamers are also available in 40 mm lengths for use in preparing root canals for endodontic implants. CLASSIFICATION : I. ISO GROUPING OF INSTRUMENTS : ISO grouping of endodontic instruments makes convenient a classification according to their manufacture, usage, cutting ability, strength and weakness. In due time ISO Federation Dentaire internationale committee grouped RC instruments according to the method of their use. 1. Group I hand use only : a.

Files both K type and H type

b.

Reamers K type

c.

Broaches

d.

Plugger

e.

Spreaders

2. Group II : Engine driven latch type : same design as group I but made to be attached to handpiece. Also included are paste fillers. 3. Group III : Engine driven latch type drills or reamers such as gates glidden (G type); Pesso (P type) as well as host of others – A,D,O,KO,T,M type reamers and Kurer root facer. 4. Group IV : Root canal points Gutta-percha, silver, paper II. ACCORDING TO GROSSMAN: Root canal instrument may be divided into 4 types based on their function. 1.

Explorer : To locate the canal orifice and to determine or assist in obtaining patency of the root canal. Eg : Smooth broaches Endodontic explorers

2.

Instruments used for Debridement: To extirpate the pulp and to remove debris and other foreign material. Eg : Barbed broaches, H file, Rasps


3.

Instruments used for shaping: To shape the root canal laterally and apically. Eg : Reamers and Files

4.

Instruments used for obturating: To cement and pack gutta-percha into the root canal. Eg : Pluggers, spreaders, lentulospirals.

III. HARTY’S CLASSIFICATION : 1.

Instruments for use during access cavity preparations:

2.

a.

Basic instruments pack

b.

Burs

c.

Rubber dam

Instruments for use during root canal preparation: a.

Hand instruments

i.

Barbed broaches

ii.

Reamers

iii.

Files

-

K type

-

K flex

-

Flexofile

-

Flex R

iv.

Hedstrom

v.

S file

3.

Power assisted R C instruments: i.

Reciprocating hand pieces

ii.

Ultrasonic instrumentation

iii.

Sonic instrumentation

iv.

The SET canal finder system

4.

Electronic canal measuring devices

5.

Measuring instruments, gauges and stands

6.

Instruments for the retrieval of broken instruments and posts Masseran kit

7.

Instruments used in filling of root canal i.

Lateral and vertical compaction

ii.

Thermomechanical compaction

iii.

Thermoplasticized injectable gutta-percha

-

Obtura system

-

Ultrafil system

iv.

The endotec thermal endodontic condenser

v.

Spiral root canal fillers.


8.

Equipment for storage and sterilization of instruments.

ISO GROUP I INSTRUMENTS INSTRUMENTS USED FOR EXTRIPATING PULP: BROACHES : Broaches have been used for many years in endodontics and were originally used in canal preparations. Because of its ease of breakage it is confined to removal of soft tissue Broaches are available in two types : 1)

Smooth broaches

2)

Barbed broaches

1)

SMOOTH BROACHES : The smooth broaches had been used as path finder by practioners as an initial instrument to

explore the patency and the walls of the canal. Uses : It is used as the initial instrument to explore the patency of the walls of the canal. Draw backs : This instrument will be placed initially without removing the tissue bulk which may lead to forcing of any inflamed or necrotic tissue through the apex. It is made up of carbon steel and will rust and cannot be left in sodium hypochloride. Most practitioners no longer follow this procedure and is rarely used.

2)

BARBED BROACHES : -

The barbed broaches are short handled instruments used primarily for vital pulp extripation.

-

ISO specification No. 63 sets the standards for barbed broaches.

Manufacturing : -

Barbed broach is a tapered instrument of soft steel that is notched by a shredder to produce sharp barbs.

-

They are manufactured from round wire.

-

The barbs are bent at a right angle from the long axis.


Available as : -

The barbed broaches are available in a variety of sizes from triple extra fine to extra coarse XC.

-

They are numbered in the same way as the reamers or files of their sizes.

-

The smallest barbed broach available has approximately the width of the size 20 instrument

-

The broach has a taper of 0.007 to 0.010 mm/mm

-

The height is longer in the broach. Length of working portion is 10.5 mm out of which 9 mm have barbs.

Mode of use : -

Barbs should be coronally placed.

-

The barbs are used to engage the pulp as the broach is carefully rotated within the canal until it begins to meet resistance against walls of canal.

-

The broach should never be forced into a canal beyond the length where it first begins to bond.

-

Forcing it apically causes the barbs to be compressed by the canal walls.

-

Subsequent efforts to with draw the instrument will embed the barbs in the walls.

Applications : -

The are primarily used to extripation of the vital pulp.

-

They are also used to loosen debris in necrotic canals.

-

They are used to remove paper points or cotton pellets.

Precautions : -

Because of its greater depth of cut the remaining core thickness is much reduced, resulting in a more fragile instrument throughout its entire length.

-

The smallest size broach available has approximately the width of size 20 instrument. So they are not used initially in narrow buccal canals of maxillary molars and mesial canals of mandibular molars.

Draw backs : -

The design is responsible for the frequency of breakage because the notching weakens the shaft by providing a place for fracture if stress or torque is applied.

-

Can not be used in narrow canals.

-

Increased pressure to retrieve the instrument results in breaking of barbs or shaft.

-

The broken instrument embedded in the canal in seldom retrievable

-

Can remove only vital pulp tissue.


INSTRUMENTS USED FOR EXPLORING THE CANAL : Before entering into the canals, the orifice must found in older patients and in calcified canals, finding the canal orifices may be most difficult and time consuming. If the canal orifices are restrictive, they need to be flared. A new addition of finding and enlarging canal orifices is by : 1)

Maellifer micro opener

2)

Micro debrider

3)

DG-16 endodontic explorer

1) MICRO OPENER : -

It is supplied by maellifer

-

It is the instrument with K-type flutes.

-

It is available in 0.02, 0.04 and 0.06 tapers.

-

It is mounted like a spreader.

-

It is used to uncover, enlarge and flare the orifices.

2) MICRO DEBRIDER : -

Micro debrider is a new addition to findings and enlarging canal orifices

-

It is available in ISO 0.02 tapers

-

It is a H-type file

-

It is used to further flare down the canal.

3) DG-16 ENDODONTIC EXPLORER

HAND INSTRUMENTS USED FOR BIOMECHANICAL PREPARATION: First designated as early as 1904 by the Kerr manufacturing company K style files and reamers are the mostly used. Now made universally of nickel titanium and stainless steel rather than carbon steel, K type instruments are produced using one of the two techniques. Manufacturing : 1) The grinding of graduated sizes of round “piano� wire into various shapes such as square, triangular or rhomboid. 2) 2nd grinding operation properly tapers these pieces.


3) To give the instruments the spirals that provide the cutting edges, the square or triangular stock is then grasped by a machine that twists it counter clock wise a programmed no of times. - Tight spirals for files - Loose spirals for reamers 4) The cutting blades produced are sharp edges of either square or triangle. These edges are known as the rake of the blade. The more acute the angle of the rake, the sharper the blade. There are approximately twice the no of spirals on a file than on a reamer. Newer Manufacturing : -

Grind the spirals into the tapered wire rather than twist the wire to produce the cutting blades. Grinding is totally necessary for nickel titanium instruments because of their super elasticity they

cannot be twisted. -

Originally, the cross section of K-files was square and the reamer triangular. Recently, they started using many configurations to achieve better cutting and flexibility.

K-REAMERS : The clinician should understand the importance of differentiating endodontic files and reamers from drills. Drills are used for boring holes in solid materials such as gold. Reamers on the other hand are instruments that ream – specially sharp-edged tool for enlarging or tapering holes. Reamers are originally intra canal instruments, used since the 19 th century for removal of the contents of the pulp canal and for widening and smoothening of the canal walls. They are manufactured by twisting triangular blanks to produce cutting edges. Because each angle of the blank is approximately 600, a sharp knife like edge is available to shave and reduce canal walls. The cross section of the blank is not excessively wide, so the instrument has a high degree of flexibility. Method of use : Reamers are placed towards the apex until some binding is felt and then turning the handle more than a full revolution. This is known as reaming action. Clock wise turning will remove materials from the canal by way of the flutes revolution. The counter clock wise turning will force material apically. The insertion of instrument shaves the dentinal walls. Twisting clock wise one quarter-to one half turn engages their blades onto the dentin and then with drawn. It mainly involves -

Penetration

-

Rotation

-

Retraction The cut is made during retraction. This process is then repeated, penetrating deeper and deeper

into the canal. When working length is reached the next size of instrument is used and so on. In slightly curved canals a reamer should be rotated only one quarter turn. The heavier reamers, however size 50 and above can almost be turned with impunity.


Draw backs : -

Fracture of the instruments

-

When used with rasping action they are less efficient than the files.

K-FILES : -

Files are useful instruments in endodontics for removal of hard tissues. The tighter spiral of a file establishes a cutting angle or rake angle that achieves its primary action on withdrawal, although it will cut in the push motion as well. The reamer was the original endodontic instrument the file was developed by changing some of the principle of design on effort to make a more efficient instrument, one that would remove tooth structure faster.

Manufacturing : A square blank was substituted for the triangular blank and was twisted more to give greater number of cutting edges. Because the Kerr manufacturing company was the first to adopt this method, these files were called K-type for many years. Instrument description : The square blank had angles of 90 degrees which did not cut as well as 600 angle of reamer. The reamers had a half to one flute per millimeter, where as files were given one and a half to two and a half flutes per millimeter and thus they had more cutting edges. The cross sectional area of a file was greater than reamer, making it less susceptible to breakage. However the tighter wind of the file and its greater cross sectional diameter decreased its flexibility. Mode of action : -

The cutting action of the file can be effected in either a filing (rasping) or reaming (drilling) motion.

a) Filing motion : -

In the filing motion, the instrument is placed into the canal at desired length, pressure is exerted against the canal walls, and while this pressure is maintained, the rake of the flutes rasps the wall as the instrument is withdrawn without turning.

-

The file need not contact all walls simultaneously. The entire length and circumference of largediameter canals can be filed by inserting the instrument to the desired working length and filing circumferentially around all of the walls.

b) Reaming motion : -

To use a file in a reaming action, the motion is the same as for a reamer


Penetration

Rotation

Retraction

The file tends to set in the dentin more readily than the reamer and must therefore be treated more gingerly. Withdrawing the file cuts away the engaged dentin. To summarize the action of files it may be stated that it may be used to ream out a round tapered apical cavity but that files are also used as push pull instruments to enlarge by rasping certain curved canals as well as the ovoid portion of the large canals. In addition copious irrigation and constant cleaning of the instrument are necessary to clear the flutes and prevent packing debris at or through the apical foramen. ADVANCES IN K-FILES (MODIFICATION OF K-STYLE) : 1) K-FLEX : -

The k-flex file has a cross section that is rhomboid shaped.

-

The instrument is twisted and has a series of cutting flutes with alternate sharp (<60 0) cutting edges so that it is more flexible.

-

It has obtuse non-cutting edges.

-

The cutting efficiency of k-flex file is greater than many brands of k file.

-

It has increased flexibility.

-

It has ability to remove debris as its alternating blades provide a reservoir for debris.

Cutting edges : -

Cutting edges of high flutes are formed by two acute angles of rhombus and have the increased sharpness and cutting efficiency.

-

Altering low flutes formed by obtuse angles of rhombus are meant to act anger, providing more area for debris removal.

-

Increased contact by instrument and canal walls provide a space reservoir with proper irrigations, further reduces the danger of compacting dentinal fillings in canal.

Disadvantages : The major disadvantage of this type of files is quicker loss of cutting efficiency. 2) FLEXO FILE : -

This instrument is manufactured by maillefer in 1981.

-

This is same as k-file but has a triangular cross section that gives sharper cutting blades.

-

Number of flutes has been increased i.e., 29 spirals and this gives more rooms for the debris than the conventional K-file.

-

The stainless steel is extremely flexible and the instrument resists fracture.

-

The file tip is non cutting.


-

The cutting edge angle is 300 at the tip and 450 at the working end.

3) TRIPLE FLEX FILE : -

This file is introduced by Kerr

-

It has more flutes than reamers but fewer flutes them files.

-

This is manufactured from the triangular cross section and twisted.

-

This is not grounded.

-

It is more flexible and more aggressive.

Advantages of K-files : -

The k-type file is strong and can easily be pre curved to a desired form for filing.

-

K-type design is that often obvious when a file has been stressed to permanent deformation. When this happens the flutes on the working part of the file are wound tighter or opened up wider. This sign is the indication for deformation and must be discarded.

-

They are efficient removers of the tooth structures in any one of three techniques because of multiplicity of the cutting edges.

Draw backs of k-files : -

Increased cross sectional diameter decreases instrument flexibility.

-

The triangular blank used for a reamer has a narrower cross sectional diameter than the square blank used for a file. The reamer has greater flexibility than files in similar sizes.

-

In larger sizes such as 30, 35 and 40 the files lose their flexibility very quickly and alterations of canal shape may be devastating.

-

The k-type and hybrid instruments fracture during clock wise direction after plastic deformation.

-

In counter clockwise direction rotation breakage occurs in half or less rotation required for breakage in the clock wise rotation. In counter clock wise direction little plastic deformation occurs before a brittle fracture occurs.

HEDSTROM FILES H-FILES : The Hedstrom file also called as H-files. The H-files resembles as a wood screw. H-files have the triangular flutes and cross section appears as single helix tear drop shape. Manufacturing : -

H-files are made by cutting the spiraling flutes onto the shaft of a piece of round, tapered stainless steel wire.

-

The machine used is similar to a screw cutting machine. This accounts for the resemblance between H-file and wood screw.


-

This gouges triangular segments out of a round blank shaft.

-

This produces a sharp edge that will cut on the removing stroke only.

-

Several new designs have also been made by gouging, including the U-file and triocut.

Mode of action : •

H-files cut in one direction only.

Retraction

It is used with filing action only, it will successfully plane the dentinal walls much faster than the k-files or reamers.

Advantages : -

It is effective cutting instrument because of sharpness of the flutes.

-

It cuts dentin walls much faster than that of K-files or reamers.

-

Indicated in immature teeth where the walls are irregular and may harbor considerable debris.

-

These instruments are also useful in removing silver points or loose broken instruments from canals.

-

They are strong and aggressive cutters.

-

These files are well suited for performing preflaring or early flaring procedures, widening the orifices of any canals for easier placement of small instruments.

Draw backs : -

It is weakened at each position of gouging during manufacture, resulting in a place for fracture if the flutes bind in dentin and the handle is rotated.

-

If it is handled incorrectly and rotated clockwise after binding in dentin, its screw like configuration may further drive the instrument apically and crack the weakened and stressed root.

-

They are not to be used in torquing action.

MODIFICATION IN CONVENTIONAL INSTRUMENTS : Until 1970’s molar teeth and teeth with curved canals were rarely treated. Grossman stated that the teeth with canal curvatures of 45 0 or greater could not be treated successfully. The reason was most endodontic files used were not flexible. To increase flexibility from past 15 years many new file systems have been evolved. As usual several of these have been very useful and efficious but others are worthless and some are potentially used. Three major areas of development for the new systems are :


1) Modification of the design of the files 2) Modification of materials used 3) Modification of the tip MODIFICATION OF DESIGN OF FILES Mc Spadden was the first to modify the traditional H-files. They are marketed as – -

Unifile

-

Dynatrak

UNIFILE AND DYNATRAK : -

They are designed with two spirals for cutting blades, and a double helix design

-

In cross section, the blades presented ‘S’-shape rather than the single helix teardrop crosssectional shape of true H-file.

-

Studies revealed that the unifile generally failed the torque twisting test based on ISO specification No: 58. They concluded that specification was unfair to H-style files that they should not be twisted more than one quarter turn.

-

Unifiles and dynatraks are no longer being marketed.

HYFLEX FILE : -

The hyflex file is having the similar cross sectional appearance like unifile

-

They appear as ‘S’-shape

-

They are marketed by coltens, whale dent, hygienic, Mahwah.

S – FILE : -

This is supplied by J-S dental, ridge field, Conn.

-

They appear to be a variation of the unifile in its double helix configuration.

-

Reports on this instrument were favourable.

-

Originally developed in Sweden.

-

This instrument has an S-shaped cross section which has been produced by grinding.

-

This results in a stiffer instrument than the conventional heads from file.

-

A millimeter scale is etched on to the shaft of the instrument to facilitate length control.

-

The instrument has good cutting efficiency in either filing or reaming action. The instrument therefore could be classified as hybrid design.

MODIFICATIONS OF THE TIP : Early interest in the cutting ability of endodontic instruments was centered around the sharpness, pitch and rake of the blades. By 1980 interest had also developed in the sharpness of the instrument tip and


tips effect in penetration and cutting as well as its possible deleterious potential for lodging and transportation. The North western university group noted that tip design as much as flute sharpness led to improved cutting efficiency. Powell et al began modifying the tips from tip to first blade. These modified files maintained the original canal curvature better. Powell et al noted that each stainless steel files metallic memory to return to a straight position, increases the tendency to transport or ledge and eventually to perforate curved canals. This action takes place on the outer wall, the convex curvature of the canal. They pointed out that when this tip angle is reduced the file stays centered within original canal and cuts all sides make evenly. This modified tip has been marked as the flex-R-File. Recognizing the popularity of modified tip instruments, other companies have introduced : -

Control safe files (Densply)

-

Anti ledging tip (Brasseler)

-

Safety Hedstrom files (sybron Endo/Kerr) Although the rounded tip is least efficient, they prepared canals more safely and with less

destruction then did the other files. FLEX-R-FILE : The flex-R-file incorporated a triangular file design and modified tip. The triangular file has a cross sectional area that is 37-5% less than a square file of the same size therefore there is increased flexibility. The files placed in curved canals produced concentrated parabolic tip to remove the instruments capability to elastic deformation in a concentrated area and permit distribution of forces over several cutting flutes. This results in reduced canal transportation during canal preparation.

SAFETY H-FILE : (symbron Endo/Kerr, orange, calif) It was designated by Buchanan and was introduced by Kerr manufacturing in 1993. They are marketed in ISO 15 to 40. This has the modified tip and has non cutting side. The spiral of working end of safety H-files is characterized by non-cutting side with smoothened edges to prevent the ledging in curved canals. Depending on the direction of canal curvature, these blunt flutes have to be oriented where material should not be removed more. It is used in linear motion and prepares curved canals with out ledging or excessive material removal on the outer wall. MODIFICATION OF THE MATERIAL USED :


Until 1960, root canal instruments were produced of carbon steel. There were many draw backs in the carbon steel instruments like sterilization of these instrument cause decreases in torque and angular deflection and stainless steel instrument were then introduced. STAINLESS STEEL INSTRUMENTS : As there were many drawbacks in the carbon steel instrument, stainless steel instrument were introduced and exhibits the following advantages over the carbon steel instruments. -

Flexible and hence less likely to fracture when strained.

-

Less susceptible to corrosion usually caused by contact with sodium hypochlorite. For 20 years till 1975 they played a major role in participation. But these instruments lack

flexibility particularly in larger sizes and can sometimes lead to procedural errors. These errors may be partly because of nature and limitations of stainless steel instrument. Further improvements have occurred over years in design of stainless steel by altering its cross section and cutting tips. Drawbacks of Stainless steel files : a)

In vitro study of stainless steel files at Connecticut demonstrated that significant wear and potential loss of efficiency occurred after only one used of 300 strokes.

b)

Study in Brazil concluded that stainless steel instruments in small sizes should be used once and the No: 30 could be used three times.

c)

Webber et al used a linear cutting motion in moist bovine bone and found that there was a wide range of cutting efficiency between each type of instruments, both initially and after successive use.

d)

A group of Margnette university compared K-type files with five recently introduced brands in three different sizes No: 20, 25 and 30. Wear was noticed by all instruments after three successive three minute test periods.

e)

A group in Michigan studied the cutting ability of the K-files and reported a wide variance in the cutting ability of individual files.

f)

Luck has shown that smaller reamers and files may be easily broken by twisting the blades beyond the limits of metal until the metal separated.

g)

Study of 360 degree clock wise rotation (ISO revision of ADA specification No: 28) found only 5-K-files failing of 100 instruments tested. They were sizes 30 to 50 all from one manufacturer.

h)

Researchers at North Western university demonstrated that endodontic files twisted in counter clock wise manner were extremely brittle in comparison to those twisted in clockwise manner. They warned that â&#x20AC;&#x153;dentists should exercise caution when backing off embedded root canal instrumentsâ&#x20AC;?.


To over come problems dike distortion, fracture and precurvature a group at Marquette university suggested that nickel titanium with a very low modulus of elasticity be substituted for stainless steel in the manufacture of endodontic instruments. NICKEL TITANIUM INSTRUMENTS : A new generation of endodontic instruments, made from a remarkable alloy, nickel titanium has added a striking new dimension to the practice of endodontics. The super elasticity of nickel titanium, the property that allows it to return to its shape following significant deformation, differentiates it from other metals such as stainless steel, that sustain deformation and retain permanent shape change. These properties make Ni-Ti endodontic files more flexible and better able to conform to canal curvature; resist fracture and wear less than stainless steel files. As early as 1975 Givjan and associates reported on potential application of Ni-Ti alloys containing nickel 55% by weight (55-Nitinol) and nickel 60% by weight (60-Nitronol). They found that 60-Nitinol is better used in fabrication of tough corrosion-resistant hand and rotary cutting instruments. No.15 files first fabricated from Ni-Ti orthodontic alloys shown two-three times elastic flexibility in bending and torsion as well as superior resistance to torsional fractures compared to stainless steel No: 15 files. In 1992, May, serene introduced new files to students in the college of dental medicine at medical university of South Carolina. Later these files become available to the professional generally. Super elasticity : -

It shows super elasticity, undergo a stress-induced martensitic transformation from a parent structure which is austenite.

-

On release of the stress the structure reverts back to austenite, recovering its original shape.

-

Deformations involving as much as a 10% strains can be completely recovered.

-

Super elasticity also occurs over a limited temperature. Minimal residual deformation occurs at approximately room temperature.

-

A composition consisting of 50% nickel and 50% atomic titanium seems ideal both for instrumentations and manufacture.

Manufacture : Today nickel-titanium instruments are ground into different designs and made in different sizes and shapes. For example K â&#x20AC;&#x201C; Style hedstrom files X â&#x20AC;&#x201C; double flutes files S â&#x20AC;&#x201C; Double flutes files U- Files U and drill designs


Implants Rotary files Canal master etc. Advantages : -

They are effective or better than comparable stainless steel instruments in machining dentin

-

They are more wear resistant.

-

New prototype rotary motors offer improved torque control with automatic reversal that decreases rotary instrument breakage.

-

Files are biocompatible

-

They are having anticorrosive properties

-

Implants are biocompatible and accepted as surgical implant.

-

With the ability to machine flutes new designs such as radial lands have been available. Radial bands allow Ni-Ti files to be used as reamers in a 3600 motion.

-

Converter handle is available that allows the operator to use rotary file as hand instrument.

-

Ni-Ti files like nitiflex and Naviflex are more flexible than stainless steel files.

-

Canal master Ni-Ti values were superior than stainless steel in all aspects. From these it seems that the clinician is changing from high torque instrument such as stainless

steel to low toque instruments such as Ni-Ti instruments which are more efficient and safer when used passively. Drawbacks : -

When testing the resistance to fracture for 21 brands they found that No: 25 stainless steel files had a higher resistance than Ni-Ti files.

-

While studying cyclic fatigue using Ni-Ti light speed instruments, Pruett et al determined that canal curvature and the number of rotations determined file breakage. Separation occurred at the point of maximum curvature of the shaft.

TITANIUM ALUMINIUM INSTRUMENTS : Much more recent development in micro titanium instruments marketed as â&#x20AC;&#x153;Microtitaneâ&#x20AC;? by micro mega France. They are available as reamers, K-files and H-files. Composition : -

These instruments contain â&#x20AC;&#x201C; 90% titanium - 5% aluminium by weight

-

These instruments have same resistance to fracture as flexible stainless steel instrument but have increased flexibility.

-

They have similar cutting efficiency like stainless steel instrument

-

Titanium-aluminium instrument fail to produce superior preparation results in curved canals.

Torsional strength and separation :


-

The clinician switching from stainless Ni-Ti hand instruments should not confuse super elasticity properties with torsional strength.

-

Tepel et al looked at bending and torsional properties of 24 different types of Ni-Ti, Ti-Al, and stainless steel instruments. They found Ni-Ti K files to be most flexible stainless steel and conventional stainless steel.

-

Wolcott and Himel at the university to Tennessee compared torsional properties of stainless steel K-type and Ni-Ti U-type instruments and all stainless steel instruments showed a significant difference between maximum torque and torque at failure. This means time between wind up and fracture in Ni-Ti instrument is extended which could lead to false sense of security.

Nickel titanium precautions and prevention : 1) Too much force should not be applied to the file never force a file 2) The straighter canal should first be enlarged to working length and then the other canal. If not NiTi file may reverse its direction at this juncture, bending back on itself and damaging the instrument. 3) Curved canals that have high degree and small radius of curvature are dangerous. 4) Files should not be over used 5) Instrument fatigue occurs more often during the initial stages of learning curve. 6) Ledges that develop in canal allow space for deflection of a file then instrument may curve back itself. 7) Ni-Ti file should not be used to bypass ledges. 8) Teeth with S-type curves should be approached with caution. Flaring of the coronal third to half of the canal will decrease the problem. 9) Avoid creating canal the same size and taper of the instrument being used. The only exception is in use of Buchanan GT file concept 10)

Avoid cutting with entire length of the file blade

11)

Sudden changes in the direction of instrument must be avoided

12)

Poor access preparation will lead to procedural errors.

13)

Advancing or pushing instrument into canal in too large an increment causes of to act as a drill or piston and greatly increases stress on the metal.

14)

Do not get in a hurry

15)

Prior to insertion and on removal look at the blade

16)

Do not assume that the length of files is always accurate; measure each file. Some files are longer from handle to tip them others. Files may also become longer or shorter if they are unraveled or twisted.

ADVANCES IN HAND INSTRUMENTS :


1) NICKEL – TITANIUM FILE : -

In 1988 the properties of a file manufactured from nickel-titanium alloy was reported.

-

This file demonstrated greater elastic flexibility in bending.

-

This file shows greater resistance to the torsional fracture than stainless steel

-

Now there are several commercial versions.

-

Ni-Ti files have a non cutting tip.

-

It can not be precurved and tend to straighten curved root canal less than stainless steel files.

2) PROFILE – SERIES 29 : -

In the present ISO system of hand instrument sizes, the tip diameter at d1 increases.

-

0.02 mm for size – 6 to 10

-

0.05 mm for sizes – 10 to 60

-

0.1 mm for larger sizes

The percentage differences between tip diameters of Sizes 10 to 15 is 50% 55 to 60 is 9% only. The variable percentage changes appear illogical and support the clinical impression that between ISO size 10 to 35 there insufficient instruments. This is blamed from problems such as ledging that occur during apical preparation of root canals. -

Profile series 29 instruments manufactured in stainless steel, address this problem with new instrument sizes that have a constant increase of 29% in d1 tip diameter.

-

In the critical smaller sizes, the range of maximal use, there are more instruments than in the ISO range, and in the less critical sizes there are fewer instruments.

-

In the profile 29, 13 instruments replace 20 in the ISO series.

-

The new size-1 profile 29 series corresponds to ISO size 10.

-

The first five instruments in the new series are all narrower at d1, than their counter parts in the ISO series.

-

This series of instruments were introduced dry Stephen Buchanan.

-

They were both available in stainless steel and Ni-Ti hand instruments.

-

These resemble original engine driven Ni-Ti “U” files.

-

All of them have a narrow types 0.02 mm

Advantages : -

These instruments are spaced with more instruments at smaller sizes and less instruments at the larger sizes.

-

Transition between sizes is enhanced due to more gradual increase in diameter

-

They come in total 13 instruments instead of ISO 20 instruments


PROFILE GT (greater taper) : -

Dentsply Maillefer has developed a â&#x20AC;&#x153;clean and shapeâ&#x20AC;? kit that contains all of the instruments for cleaning and shaping.

-

Profile GT is available with greater tapers and tapers ranges as 0.06, 0.08, 0.10, 1.12

-

Buchanan pointed out that profile-GT are sized to fit certain sized canals.

Mode of use : -

Buchanan recommends that one should start with 0.10 instrument to flare out the coronal third of the canal. This means that this instrument is an ISO size 20 at the tip; but taper is 0.10 mm/mm. It establishes a wider freedom for those instruments.

-

The instrument is used in a twisting motion first counter clockwise and then clockwise with apical pressure and then retracted.

-

The 0.06 file for instance is recommended for extremely thin or curved roots.

-

The 0.08 file is best for lower anterior, multirooted premolars and the buccal roots of the maxillary molars, single canal premolars, mandibular canines and maxillary anteriors.

-

The 0.12 instrument is used for larger canals.

3) GOLDEN â&#x20AC;&#x201C; MEDIUMS (intermediate files) : -

Maillefer have produced a series of intermediate size instruments to complement ISO standard size instruments.

-

The new instrument roughly correspond in size to half way between standard ISO sizes

-

They are numbered as 12,17,22,27,32 and 37

-

Golden-mediums are part of flexo file range.

Disadvantages : This system addresses the problem of few instruments in the smaller sizes. It does not achieve linear dimensional change at d1. Advantages : A number of procedural errors like ledging, zipping, transportation of apical foramen and perforations are resulted from uncontrolled dentin removal. Smaller instruments are used until the larger size passes in canal without force. The temptation to speed the process by forcing large files canals too early cause ledges, zipping and perforation. To avoid these errors and to provide a smoother progress these files play the important role. 4) CUSTOMIZED INTERMEDIATE FILES :


Use of golden medium files was first described by Weine who suggested trimming 1 mm from tip of file and rounding off sharp edges on diamond nail file. In this way file sizes 10, 15, 20,25 may be converted into 12,17,2 and 27 etc. Advantages : -

We can use smaller instruments when large files cannot pass into canal. Smaller sizes are used until the larger sizes passes in canal with out force.

-

This provides smoother progress

Disadvantages : -

These are disposable

-

Edges may be difficult to smoothen, which therefore creates ledges during filing.

5) MAC FILES AND DOUBLE MAC FILES : -

The MAC files are the newer instruments

-

They are instruments manufactured from Ni-Ti alloys

-

It has a working surface demonstrating dissimilar helical angles with blades that spiral round the shaft at different rates.

-

According to manufacturer this allows the instruments to stay relatively loose within the canal and balances the forces of the file against the canal wall during rotation to prevent canal transportation.

-

Double MAC files have a series of increasing tapers from 0.03 to 0.05 mm/mm length.

6) CANAL MASTER â&#x20AC;&#x201C; U : -

Canal master â&#x20AC;&#x201C; U (CMU) hand instrument was developed in the late 1980s.

-

It has 0.1 mm non cutting pilot tip in order to follow the canal curvature without gauging or ledging.

-

Cutting blade was 1 mm in length

-

It has non cutting parallel shaft with diameter smaller than that of cutting blade.

-

Cutting flutes are machined from circular blanks.

Advantages : -

It is designed to improve debris removal

-

It reduces apical extrusion of the debris

-

It has been reported to create a well centered canal preparation without ledging and transportation.

Draw backs : -

According to Zuola et al, canal master instruments show inconsistencies in the taper and length of the cutting head and are generally predisposed to wear and breakage.

-

When these instruments separate, it tends to be at a point close behind the cutting head and all fractures are sudden.


Improvement : In order to overcome some of the problems described above, the CMU are now made up of Ni-Ti. Ni-Ti CMU hand instrument has produced a better canal preparation than others. 7) FLEXOGATE : -

It is a logical development of the gates-Glidden drill

-

It is similar in design and use to the CMU hand instrument

-

Flexo gates task is enlarging the apical region of the canal

-

Flexo gates demonstrate a non-cutting guiding tip.

-

Debris evacuation zone helps to maintain root canal configuration during instrumentation.

Advantages : -

Briseno has compared flexogates and canal master in vitro and concluded that flexogates is less likely to cause apical transportation.

-

Even though it fractures more easily during torsion than CMU, it has a breakage point 16 mm from the tip, which ensures its retrieval in the event of separation.

-

The bending movements of flexogates and CNU are well below standards specification for files, leading to considerable flexibility on curved canals.

Draw backs : Flexogate can fracture more readily or easily during torsion than the canal master – ‘U’. 8) QUANTEC : -

First designed by Mc Spadden and undergone modifications

-

Quantec instruments are more reamer like than files.

-

The recommended technique for hand instrumentation is divided into three techniqueNegotiation, shaping and apical preparation.

-

The quantec tapers ranges from 0.02, through 0.06 with ISO tip sizing.

-

The quantec flare series with increased tapers of 0.08, 0.10 and 0.12 all with tip sizes of ISO 25 are designed.

Method of hand instrumentation for quantec : It is divided as - Negotiation - Shaping - Apical preparation i) NEGOTIATION : -

First explored with a standard No:10 or No:15 0.02 taper curved stainless steel K-file and working length is determined.

-

Then exploration is followed by quantec No: 25, 0.06 taper Ni-Ti instrument.

-

It is used in reaming action from canal orifice to just short of apical third.


-

Then continued with 0.02 stainless steel No: 10 or 15 and No: 20 and 25 to clean and shape.

ii) SHAPING : -

Quantec instruments all with size No: 25 tip are used.

-

No: 25, 0.06 taper quantec instruments used later with the reaming actions.

-

It is followed by No: 0.05 taper quantec and then 0.04 and 0.03 tapers until apical stop.

iii) QUANTEC APICAL PREPARATION : -

0.02 taper quantec instrument is used and diameter of apical third is enlarged upto No:40,45 or 50 depending on size of canal.

Advantages : -

It has the safe cutting ability

-

It has non cutting tips

-

The radial bands of quantec are slightly relieved to reduce frictional contact with the canal wall and the helix angle is configured to efficiently remove debris.

9) EZ-FILE (safe sided system) / (flute modification) : -

A series of non-circular instruments have a patended non-interrupted flat sides architecture.

-

This allows quick negotiate to apex of any type of canal while applying less force.

Method of use : -

These are usually used in watch winding motion.

-

Never used in push or pull strokes

-

Clock wise direction engages the dentin

-

Anticlock wise direction removes the dentin

Available as : 8, 10 – 0.02 taper → To negotiate apex 15-40 – 0.02 taper → Non circular 30 (Ni-Ti) – 0.04 taper → Orange color 25 (Ni-Ti) – 0.08 taper → Brown color No :2 Pesso reamer. 10) C - FILES DENTSPLY Maillefer, leaders in the field of endodontics, are pleased to announce the launch of their new C+ Files. The C+ Files are for the initial instrumentation of the root canal. C+ Files have stronger buckling resistance compared to K-Files, which makes easier location of the canular orifices and easier access to the apical third. There is also better negotiation of calcifications and a better tactile feel. C+ Files have a depth gauge making it easier to determine working length when working with X-rays. The pyramid shaped tip makes easier insertion during catheterization and the square


section allows better resistance to distortion. The polished surface of the C+File allows better removal of debris as well as smoother insertion of the instrument in the canal. C+ Files are available in three lengths, 18mm, 21mm and 25mm and three sizes 8, 10 and 15.

11) V-TAPER™ GLIDE-PATH SYSTEM The Guidance Glide-Path System is a revolutionary advancement in hand files. The three #10 VTaper™ hand files with a variable taper design form a better shaped and more efficient glide-path, enhancing rotary file performance and far exceeding 02 tapered hand files. #10 V-Taper™ Hand Files Establishes the Glide-path for Small, Medium, and Large Canals Use: 10 (V02) –> 10 (V04) –> 10 (V06) –> repeat to taper of choice

Always use a lubricant: NaOCl with EDTA. Use each file for less than 10 seconds, then move to the next file. Establish apical patency for calcified, tortuous, or difficult canals.


ISO GROUP II AND III INSTRUMENTS (ROTARY) Engine driven instruments can be used in different types of hand pieces. They are : HAND PIECES : 1. CONTRA â&#x20AC;&#x201C; ANGLE HAND PIECE : Contra-angle hand pieces are available in three types. They are : a)

Full rotary hand piece either latch friction grip.

b)

Reciprocating / quarter turn hand piece.

c)

Vertical stroke hand piece

a) FULL ROTARY HAND PIECE : -

Specially designed hand pieces providing a mechanical action to a root canal cutting instrument have been available for 30 years.

-

They are all designed to reduce the time spent in canal preparation.

Applications : -

Full rotary hand piece is used in straight-line drilling or side cutting.

-

It is used to get coronal access to the canal orifice by using round or tapered burs or diamond points.

-

It is used to funnel out the orifices for easier access to clean and shape canals with slow turning Ni-Ti reamer type instruments.

-

It is used to prepare post channel for final restorations.

Draw backs : -

These hand pieces are used as straight time drilling, as instruments do not readily band and they should be limited to the straight canals only.

-

They are often misdirected or forced beyond the limits

-

They cause perforations.

b) REDUCTION GEAR HAND PIECE : The full rotary have many from draw backs due to their speed and as a solution for these problems reduction gear hand piece with low speed has been introduced. -

These motors are specially designed to power the new Ni-Ti instruments in canal preparation.

-

The speeds vary from 300 rpm to 2,000 rpm. 300 rpm is suggested for Ni-Ti profiles and 2000 rpm is suggested for light speed instruments.


-

Newer hand pieces are available in reduction gear where both speed and torque can be controlled.

Examples of reduction gear hand piece : •

Medidenta /Micro mega MM 324 reduction gear hand piece

Quantce ETM (electric torque control motor)

Moyco/union broach sprint EDM (electronic digital motor hand piece)

These electro motors are specially designed to power the new Ni-Ti instruments in canal preparation. The speeds vary from 300 rpm suggested for the Ni-Ti profiles (Tulsa dental) to 2,000 rpm recommended for the light speed instruments. •

Aseptico ITR Motor hand piece

The Nouvag TCM Endo motor

New Endo-pro electric

New pro Torq motor hand piece.

An entirely newer electric hand pieces are available where in not only the speed can be controlled but the torque as well. That is, the speed and torque can be set for a certain size instrument and hand piece will “stall” and reverse if the torque limit is exceeded. •

TRI AUTO ZX : An entirely new wrinkle in rotary hand piece is Morita tri auto ZX -

It is a cordless, battery powered, endodontic slow speed hand piece

-

It has built in apex locater

-

It uses rotary Ni-Ti instrument held by a push button chuck.

Advantages : -

The hand piece automatically starts when the file enters the canal and stops when the file is removed.

-

If too much pressure is applied, the hand piece automatically stops and reverses rotation.

-

It also automatically stops and reverses rotation when the file tip reaches the apical stop as determined by the built-in apex locater.

Applications of reduction gear hand piece : -

Gates Glidden drills, peaso reamers, rotary H type, K-type instruments can be used.

-

Used to flare and prepare cervical and middle portions of the canal with orifice opener.

-

Used in slow speed latch type

-

Canal master rotary instruments can be used

-

Ni-Ti sensor files and Ni-Ti finishing files can be used.

c) RECIPROCATING HAND PIECE :


Specially designed hand pieces providing a mechanical action to root canal cutting instrument have been available for 30 years. They are all designed to reduce the time spent in canal preparation. Reciprocating hand pieces are available as follows : i) GIROMATIC HAND PIECE : -

It is the first machined hand piece, now it is used little by the endodontists.

-

In this device the quarter turn motion is delivered 3,000 times per minute

-

It accepts only latch type instruments

-

It accepts barded-broach-type files (Rispi) and three sided files (Heli files)

-

The continuous rotation of the drives half in the hand piece is transformed into an alternating greater-turn movement of the file.

Draw backs : -

It leads to uneven canal preparations

-

It was not able to accept all the instruments

-

Lack of expertise

ii) M4 SAFETY HAND PIECE : -

It is marketed by sybron-Kerr

-

It has a 30 degree reciprocating motion

-

It has a simplified chuck mechanism activated by the thumb pressure to accommodate a plastichandled root canal instrument.

-

It has a 4:1 gear ratio, which even at full speed demonstrates minimal torquing.

-

The Kerr Company recommended that their safety Hedstrom instrument be used with M4.

-

Zakariasen et al found M4 mounted with safety hedstrom files, to be superior to step back hand preparations and had a shorter time of preparation.

Method of use : The hand piece lets the instrument glide along the walls of the canal by mimicking commonly used hand movements. iii) ENDO â&#x20AC;&#x201C; GRIPPER HAND PIECE : (Reciprocating H.P) -

It is marketed by Moyco/union broach.

-

It is a similar hand piece with a 10:1 gear ratio

-

It has 450 turning motion

-

As like Kerr M4, the Endo Gripper also uses regular hand instruments rather than the contra-angle instruments.


-

Union broach recommends their flex-R and onyx-R files.

iv) CANAL FINDER SYSTEM: -

The canal finder system consists of a contra angle hand piece powered by a micro motor that runs at speed >3000 rpm.

-

It produces a reciprocal screwing action

-

It enables the file to cleave rather than abrade the canal wall

-

It advances along the path of least resistance, maintaining the original pathway.

-

Specially designed files rotate the file slightly when resistance from the canal is met.

-

This system is of benefit in initial preparation of extremely curved and narrow canals.

-

It has a tendency to straighten canals with over instrumentation and widening of the apical foramen.

2) VERTICAL STROKE HANDPIECE : -

These are the special hand pieces that imports a vertical stroke

-

With the added reciprocating quarter turns it cuts in when the instrument is stressed.

-

Levy introduced a hand piece that is driven either by a air or electrically that delivers vertical strokes ranging from 0.3 to 1 mm.

-

The more freely the instrument moves in the canal, the longer the stroke.

Mode of action : -

The hand piece with quarter turn reciprocating motion kicks in along with the vertical stroke, when the canal instrument is under bond in a tight canal.

-

If it is too tight the motion ceases and the operator returns to a smaller file.

-

Developed in France, the canal finder system uses the A file, cleaver variation of H-file.

OTHER CONTRA ANGLE HAND PIECES: RACER : The racer contra angle hand piece uses a standard file and oscillates the file in the root canal The instrument length can be adjusted to the working length using this contra angle. Disadvantage : -

A major disadvantage of this instrument is that debris may be forced ahead of the instrument, with resulting clogging of the canal or pushing of debris into periapical tissue.

-

When engine driven instruments are used access to apical foramen must be made first by hand instrumentation.


-

Ring found that root canals could not be enlarged with the RACER instrument in 13% of cases.

EXCALIBUR : -

This hand pieces works rendering random vibratory movement on endodontic files.

-

It vibrates only laterally and is devoid of vertical movements.

-

The amplitude of movement is 1.5 â&#x20AC;&#x201C;2 mm

-

The oscillation frequency is about 1000-2000/ second

-

This uses specially modified k type files

-

This can be attached to the air motor line in the dental unit

-

The water flow in the air motor line pass through the hand piece and irrigate root canal

-

It runs at 20,000 â&#x20AC;&#x201C; 25,000 rpm.

3) ULTRASONIC HAND PIECE : -

Ultrasonic endodontics is based on a system in which sound as an energy source at (20-25 KHδ) activates an endodontic file resulting in three dimensional activation of the file in the surrounding medium.

-

Instruments used in the hand piece that move near or faster than the speed of sound range from standard K-type files to special broach like instruments.

Mode of action : The main debriding action of ultrasonics was initially thought to be by cavitations, a process by which bubbles formed from the action of the file, become unstable, collapse and cause a vacuum like implosion. A combined shock, shear and vacuum results. -

Richman must be credited with the first use of ultrasonics in endodontics (1957).

-

Martin and Cunningham were the first to develop a device, test it and see it marketed on 1976, and named it as Cavitron endodontic system.

Different ultrasonic devices available are : -

Cavitron endodontic system (Densply)

-

Enac (Osado electric Co)

-

Piezon master 400 (Eletro medical systems) These instruments all delivered an irrigant or coolant usually sodium hypochlorite onto canal

space while cleaning and shaping are carried out by a vibrating K-file. Transient cavitation does not play a role in canal cleaning with cavi Endo unit; however acoustic streaming does appear to be main mechanism involved. Acoustic streaming depends on free


displacement amplitude of file and that the vibrating file is dampened in its action by the restraining walls of canal. CAVITRON ENDODONTIC SYSTEM : -

Cunningham developed and marketed in 1976.

-

It is a modified cavitron

-

It has the magneto stricture power source

-

Its vibrations range around 25,000 KHZ.

-

It generates heat hence require cooling device

-

It is long and narrow

-

It has special tube connections to pump irrigant from reservoir and supply point of compressed air

-

It utilizes K-type files, K-flex files and diamond impregnated files.

PIEZON MASTER 400 : -

It has piezo electric genetor source.

-

The vibrations are in range of 35,000 KHZ.

-

In this system heat is not generated

-

It is short and wide

-

It has built in pump and does not need any special tube connections

-

It is used in location of calcified canals removal of broken instruments and root end preparations

-

They also utilize the K-type files, k-flex and diamond impregnated files.

Advantages : -

The Guyâ&#x20AC;&#x2122;s hospital group found that the smaller files generated acoustic streaming and hence much cleaner canals.

-

These was an enormous difference in clean lines between canals merely needle â&#x20AC;&#x201C; irrigated during preparation and those canals prepared and followed by 3 minutes of ultrasonic instrumentation with a No-15 file and 5.25% sodium hypochlorite.

-

One substitution of sodium hypochlorite (2.5%) for water, all of the bacteria was killed providing once again the importance of using an irrigating solution with bactericidal properties. Using water alone, the ENAC system was more effective but when sodium hypochlorite was used

the cavi endo unit (which has built in tank) was superior. They also reported ultrasonic preparation to be significantly faster. -

The K-flex is more efficient than the regular K-style files.

Draw backs : Greatest displacement amplitude occurs at the unconstricted tip and greatest resistance occurs when instrument is negotiating the apical third of a curved canal. -

Lack of freedom for the tip to move freely to either cut or cause acoustic steaming to cleanse

-

Irrigant could not advance to the apex until the file could freely vibrate.


-

K-files were precurved when used in the curved canals.

-

Ultrasonics alone actually increased the visible counts of bacteria in simulated canals and it may be due to the lack of cavitation and dispersal effects of the bacteria by the acoustic streaming. Cavitro endo system was a disappointment in that it was so slow, blacked and ledged canals, and

fractured files in severely curved canals. Recommendations : -

After canals are fully prepared by what ever means, they recommended returning with a fully oscillating No:15 file for 5 minutes with a free flow of 1% sodium hypochlorite.

-

Guy hospital group found that root canals had to be enlarged to size of No:40 file to permit enough clearance for the free vibration of No:15 files at full amplitude.

4) SONIC HAND PIECES : -

The principal sonic endodontic hand piece available today is the – micro mega 1500 sonic air endo system (or 1400). It is marketed by (Medidenta / micro mega).

-

Like the air rotor hand piece, it attachés to the regular airline at a pressure of 0.4Mpa.

-

The air pressure may be varied with an adjustable ring on the hand piece to gone on oscillatory range of 1,500 to 3,000 cycles /second.

-

Tap water irrigant or coolant is delivered into the preparation from the hand piece.

Mode of action : The sonically powered files in this hand piece oscillate in a large elliptical motion at the tip. When loaded into the canal oscillation motion changes into a longitudinal motion, up and down, a particularly efficient form of vibration for the preparation of root canals. -

The strength of micro mega sonic hand piece lies in the special canal instruments used and ability to control air pressure and hence the oscillatory pattern.

-

The files used in micro mega 1500 are

Rispi sonic files

Shaper sonic files

Trio sonic files

Advantages : -

Miserendino et al found that Ripsi sonic and shaper files were significantly more efficient than the other systems and in all types of root canals.

-

Kielt and Montgomery tested micro mega sonic unit with trisonic files against ultrasonic cavitron endo and enac units with k-files and found trisonic files less effective and Medidenta (micro mega 1500) unit was superior to other endosonic systems.


-

The Zakariasen group at Dalhousie University reported usual success in combining hand instrumentation with sonic enlargements using micro mega 1500.

-

At the University of Minnesota, the ultrasonic units were tested against the sonic unit and found micro mega sonic to be the faster in preparation time and caused the least amount of straightening of the canal.

-

A US army research group tested sonic versus ultrasonic units and concluded that they were all effective in canal preparation but judged the micro mega sonic AIR system, using Rispi and sonic files as best system tested.

Draw backs : Fair bourn et al compared four techniques according to amount of debris extruded from apex. The sonic technique extruded the least and hand instrumentation the most debris. Ultrasonic was half way between. 5) COMPARATIVE CONCLUSION OF AUTOMATED DEVICES : It appears safe to say that no one automated device will answer all needs in canal cleaning and shaping. Hand instrumentation is essential to prepare and cleanse the apical canal, no matter which device, sonic or ultrasonic is used. The sonic unit Micro mega 1500 reportedly enlarged the canal faster when Rispi or files are used where as the canal finder system using A-style files leads in incrementing narrow curved canals. Finally ultrasonic Cavi Endo and Enac units using small k-files and half strength sodium hypochlorite for an extended 3 minutes time to debride canal. No technique with out sodium hypochlorite kills bacteria.

ROTARY INSTRUMENTS : Two of the most historic and popular engine instruments are : i)

Gates â&#x20AC;&#x201C; Glidden drills

ii) Pesso reamers (drills)


GATES-GLIDDEN DRILLS : -

Gates Glidden drills are an internal part of a new instrumentation technique for both initial opening of the canal orifice and deeper penetration in both straight and curved canals.

-

Gates Glidden drills are designed to have a weak spot in the part of the shaft closest to the hand piece so that if the instrument separates the separated part can be easily removed from the canal.

-

They come the sizes 1 through 6 although the sizes are being converted to the ISO instrument sizes and colors.

Applications : -

In the step back preparation, the mid canal area in the region where reshaping can be done with power driven gates glidden drills starting with the smaller drills No:1 and No:2 and gradually increasing in size No:4,5 and 6, proper continuing taper can be developed.

-

Hand powered gates glidden drills or light speed instruments may be used for the final finish.

-

In the crown down technique initially Marshall and Pappin advocated a â&#x20AC;&#x153;Crown-down pressure less preparationâ&#x20AC;? in which gates glidden drills and large files are first used in the coronal one thirds of the canals.

-

To ensure penetration, one may have to enlarge the coronal one third of canal with progressively smaller gates glidden drills.

-

In the modified step down technique following complete access, face off the orifices with an approximately sized gates glidden drills. This creates a smooth guide path to facilitate the placement of subsequent instruments.

-

To accomplish pre enlargement of the canal gates glidden drills are used at approximately 800rpm, serially, passively and like a brush to remove restrictive dentin. Initially one should start with a gates glidden drills No:1 and carry each large instrument short of previous instrument to promote a smooth, following tapered preparation. Frequent irrigation with sodium hypochlorite and recapitulation with a small clearing file to prevent blockage should be done.

Advantages : In a laboratory study, leubke and Brantley tested two brands of gates glidden drills by clamping the head of the drill and then twisting the handles wither clock wise or counter clock wise. There was no specific pattern to their fracture except that source broke at the head which are easy for the removal. -

Increases the access and allows greater control and less chance of zipping near the apical constriction.

Draw backs : Leubke and Brantley repeated the experiment, allowing the drill head to turn as it would in a clinical situation. This time all the drills fractured near the shank which is difficult to remove the fractured instrument.


-

Gates Glidden drills try to screw themselves into the canal, binding and then breaking. So it should be used with greater care.

Recommendation : -

Gates Glidden drills must be used with greater case because they tend to screw themselves into the canal, binding and then breaking. To avoid this, it has been recommended that the larger sizes be run in reverse.

-

A better suggestion is to lubricate the drill heavily with RC-prep or Glyde, which will prevent binding and the rapid advance problem. Lubrication also suspends the chips and allows for a better feel of the cutting as well as the first canal curvature. Used gates glidden drills are also less aggressive then new ones.

PESSO REAMER : -

It is most often used in preparing the coronal portion of the root canal for a post and core.

-

Safe ended pesso drill should be used carefully to prevent lateral perforations.

-

The pesso reamer has long sharp flutes connected to the thick shaft.

-

It cuts laterally and used to removal of gutta percha in the post preparation.

-

They have a safe end.

Recommendation : Pesso reamers should be used at low speed and with extreme caution to prevent over instrumentation and perforations. Advantages : Neagly found that removal of the filling material coronal to the silver point with a pesso reamer caused no leakage. ORIFICE OPENER : -

It is developed by martin

-

It is used to flare and prepare the cervical and middle portions of the body of the canal

-

It has square shaft design

-

The blade is straight and have the vertical blades

-

It is available in ISO sizes from 25 through 70.

-

It is more flexible than gates glidden

-

It is mostly preferred in straight portions of the canal preparations.

-

It is offered in place of gates glidden drills and pesso reamers.

-

It is used with reduction gear hand piece.

Available as : -

The length of orifice opener is 19 mm

-

Cutting length is approximately â&#x20AC;&#x201C; 9 mm


-

ISO tip sizes of 30,40 and 50 are built into these files with tapers of 0.06 and 0.07

Advantages : -

As the cutting length is short, it reduces separation and makes easy to manipulate in difficult access areas.

ROTARY K-TYPE, U-TYPE, H-TYPE AND DRILL TYPE INSTRUMENTS : As previously stated, the same instrument designs described for hand instruments are available as rotary powered instruments. Before a century ago k-style rotary broaches (reamers) made of carbon steel were being used. At that early time, the probability of their breakage was precluded by the very slow speed of the treadle-type, foot powered hand pieces. Today, at speeds that vary from 300 to 2,500 rpm and with the growing use of Ni-ti instruments rotary canal preparation is once again very much is vague. Although the K-style configuration is still widely used the rotary U-style (profile) and drill style (quatec) instruments are proving ever more popular. The rotary instruments like U-style and drill style are as described as follows: -

Profile rotary instruments

-

Protaper rotary instruments

-

Quantec rotary system

-

Light speed endodontic instruments

-

Rapid body shapers, rotary reamers and pow-R rotary files.

PROFILES ROTARY SYSTEMS: 1) PROFILE 0.04 AND 0.06 TAPER ROTARY INSTRUMENTS -

These are marketed by dentspsy

-

They are proportionately sized nickel-titanium “U-shaped” instruments.

-

They are designed for use in a controlled, slow-speed, high torque rotary hand piece

-

The preferred range of speed is 275 to 325 rpm.

Mode of action : -

These tapered instruments are rotated and produce an accelerated step-down preparation, resulting in a funnel form taper from orifice to apex.

-

These “reamers” rotate clock wise to remove pulp tissue and dentinal debris and travel in anticlockwise to back up the shaft. As a result these instruments require periodic removal of “dentin mud” that has filled the “U” portion of the file.

-

Although these tapers have a 90 0 cutting angle the non aggressive radial landed flutes gently plane the walls without gouging and self threading.

Available as : -

The profile variable taper instruments are manufactured in standard ISO sizing as well as series 29 standard i.e. every instrument increases 29% in diameter.


-

The U-blade design is similar in cross section to the light speed.

-

It has flat out edges that cut with a planning action allowing it to remain more centered in canal compared to conventional instruments

-

The profile variable taper has a 600 bullet nose tip that smoothly joins the flat radial lands.

-

Profile instruments are available in either 0.04 (double taper) or 0.06 (triple taper) over the ISO 0.02 taper.

-

They have 900 cutting angle.

-

They are cut deeper to add flexibility and help create a parallel inner core of metal. Thus when the profile taper is rotated, stress become more evenly distributed along the entire instrument in contrast to a nonparallel core or tapered shaft of a conventional instrument in which stress are more concentrated towards the tip of its narrow end.

Applications : -

The 0.04 is more suitable for small canals and apical regions of most canals, including the mesial roots of mandibular motors and buccal roots of maxillary molars.

-

The 0.06 in recommended for the midroot portions of the most canals, distal roots of mandibular molars and palatal roots of maxillary molars.

-

Similar to graduating taper technique of Quentec series the clinician has the option of using alternating tapers within a single canal i.e. combination of 0.04, 0.06 and 0.07 taper profile instruments.

-

Higher tapers are used first then progressively smaller tapers.

Advantages : -

The profile taper has a built in safety feature, in which by patented design, they purportedly unwind and then wind up back ward prior to breaking.

-

When profile is rotated, stresses become more evenly distributed along the entire instrument in contrast to non parallel core or tapered shaft of a conventional instrument in which stresses are more concentrated towards the tip of its narrow end.

-

0.06 tapers improve canal shape.

-

Due to pronounced taper of these instruments, canal is shaped quickly, efficiently working from coronal section towards the apical section.

-

Area of contact with canal walls is small, therefore the contact pressure is high and this gives instrument greater cutting efficiency. In addition the extreme point remaining free allows of to function as a guide.

ORIFICE SHAPERS : -

They are designed to replace gates-Glidden drills

-

They are available in 0.06 and 0.07 tapers

-

They are available with radial lands and U-shaped file design


-

They are used for shaping the coronal portion of canal

-

Because of its U-shaped design the instrument remains centered in the canal while creating a tapering preparation.

-

This preflaring allows for more effective cleaning and shaping of apical half of the canal with the profile series 0.04 tapers.

Canal preparation using profile 0.04 and 0.06 and orifice shaped : Once access canal patency, and an estimated working length have been determined. -

No: 30, 0.06 taper orifice shaper in taken several millimeters into canal thus creating pathway for next instrument

-

No : 50, 0.07 taper orifice shaper is then used to crater more coronal flare followed by No:40, 0.06 taper orifice shaper. This last instrument should be advanced half way down the canal using minimal pressure.

-

Working length taken with stainless steel file.

-

Now 0.04 or 0.06 taper profiles are advanced passively till working length.

-

As the rotary reamer moves close to length, a funnel shape is imparted to the canal walls.

-

If the tapers are not taken to full working length hand files are used to complete the apical 1 to 2 mm.

PROFILE GT ROTARY INSTRUMENTS : -

They are supplied by densply company

-

They are made up of Ni-Ti alloy.

-

They are designed by Dr. Steven Buchanan and are also available as hand files.

Available as : -

Files are manufactured in 0.06, 0.08, 0.10 and 0.12 tapers, all having a constant ISO non cutting tip diameter of 0.20 mm

-

They have variably pitched, radial lands, clockwise cut U-blade flutes that provide reaming like efficiency at the shank with K-file strength at there tips.

-

Open flute angles are present at the shank ends

-

The maximum flute diameter is also set at 1.0 mm safely limiting coronal enlargement.

-

Because the GT files vary by taper but have the same tip diameter maximum flute diameters, the flute length becomes shorter as taper increases.

-

A set of three accessory GT files are available for unusually large canals having diameters greater than 0.3 mm

Applications : -

The 0.06 taper is designed for moderate to severely curved canals in small roots.

-

The 0.08 taper is designed for straight to moderately curved canals in small roots.


-

The 0.10 taper is designed for straight to moderately curved canals in large roots.

-

A set of accessory GT files are available for unusually large root canals having apical diameters greater than 0.03 mm.

Advantages : -

They have a constant ISO non cutting tip diameter of 0.20 mm to ensure maintenance of a small apical preparation.

-

The open flute angles of shank end also tend to reduce the files ability to thread onto the canal, a typical problem that occurs with the rotary designs

-

The maximum flute diameter is also set at 1.0 mm safely limiting coronal enlargement.

-

A set of three accessory GT files are available for unusually large root canals having apical diameters greater than 0.3 mm

ACCESSORY GT FILES : It is available as a set of three instruments -

These instruments have a taper of 0.12 mm per mm.

-

They have a larger maximum flute diameter of 1.5 mm

-

They have tip diameters varying from 0.35, 0.50 and 0.70 mm.

Advantages : They can be used in unusual large root canals having apical diameters greater then 0.03 mm. -

When used in canals with large apical diameters, they are typically able to complete the whole shape with one file.

-

They are designed so that final taper of the preparation is essentially equivalent to the respective GT file used.

Canal preparation using profile GT rotary instrument : Profile GT technique can be broken down into three steps : -

Step down with profile GT

-

step back with profile 0.04 taper files

-

GT file to create final canal shape

-

Step down approach is used once initial negotiation is completed with hand files.

-

GT files 0.12, 0.10, 0.8 and 0.6 tapers are then used in step down manner at 150-300 rpm.

-

Working length is determined once if it has reached two thirds of estimated length.

-

In some cases 0.06 taper will reach full length since the standard GT files all have 0.20 mm tip diameter, the 0.08 and 0.10 taper files should easily go to length of 0.08 or 0.10 taper is desired for that canal.

-

Rather than using GT file to the apical terminus, profile 0.04 taper in sizes 25 to 35 are used in step back manner starting 2 mm short to working length.


-

The standard GT file can then be used to shape apical 2 mm of the canal. If additional coronal flare is needed, GT accessory file can be used.

PROTAPER ROTARY SYSTEM : -

The new instrument system consisting of three shaping and three finishing files was co-developed by Dr. Clifford Ruddle, Tohn west, Pierre Mactou, and Ben Johnson and was designed by Francois Aeby and Gilbert Rota of Dentsply/Maillefer in Switzer land.

Available as : -

The protaper system consists of only six instrument

Sizes – three shaping files Three finishing files i) SHAPING FILES : The shaping files are labelled as S-X S-1 S-2 S-X: -

This auxillary instrument used in canals of teeth with shorter roots or to extend and expand the coronal aspects of the preparation, is similar to use of gates glidden drills or orifice openers.

-

The s – x has a much increased rate or taper from Do (tip diameter) to D 9 (9 mm point on blades) than other shaping protapers (s-1, s-2)

-

At the tip (D0) the S – X shapes has an ISO diameter of 0.19 mm. this rises to 1.1 mm at D 9, which is comparable to tip size of size 110 ISO instrument.

-

After D9 the rate of taper drops off up to D 14 which thins and increases the flexibility of the instrument.

S – 1 SHAPING FILE : -

S – 1 starts at the tip size of 0.17 mm.

-

It gains in taper upto 1.2 mm.

-

Unlike consistent increase on taper per millimeter in ISO instruments, it has increasingly larger taper each mm over 14 mm length of their cutting blades. This makes instrument unique.

-

S – 1 is designed to prepare the coronal one-third of the canal.


-

S – 1 even helps in enlarging apical third of the canal.

S – 2 SHAPING FILE : -

S – 2 file start at tip sizes of 0.20 mm

-

It gains in taper upto 1.2 mm

-

Unlike consistent increase in taper per mm in ISO instrument it has increasingly larger taper each mm over 14 mm length of their cutting blades. This makes instrument unique.

-

S – 2 is designed to prepare the middle third in addition to critical region of the apical third.

ii) FINISHING FILES : -

The three finishing files have been designed to plane away the variations in canal diameter in the apical one third.

-

The finishing files are designated as: F–1 F–2 F–3

FINISHER F – 1 : -

F – 1 have tip diameter D0 of ISO sizes 20.

-

These tapers differ between D0 and D3. They taper at rate of 0.07 mm/mm

-

From D4 to D14 it shows decreased taper that improves its flexibility.

FINISHER F – 2 : -

F – 2 have tip diameter Do of ISO sizes 25.

-

These tapers differ between do and D3. They taper at rate of 0.08 mm/mm

-

From D4 to D14 it shows decreased taper that improves its flexibility.

FINISHER F – 3 : -

F – 3 have tip diameter D0 of 150 sizes 30.

-

There taper differ between Do and D3. They taper at rate of 0.09 mm/mm.

-

From D4 to D14 it shows decreased taper that improves its flexibility.

-

It has been further engineered to increase its flexibility in spite of its size. Generally only one instrument is needed to prepare the apical third to working length, and tip sizes

(0.20, 0.25 and 0.30) will be selected based on the canals curvature and cross sectional diameter.


Although primarily designed to finish the apical third of the canal, finishers do progressively expand the middle third as well. Pro taper benefits : 1)

The progressive (multiple) taper design improves flexibility and “carving” efficiency, an important asset in curved and restrictive canals.

2)

The balanced pitch and helical angles of the instrument optimize cutting action while effectively auguring debris coronally, as well as preventing the instrument from screwing into the canal.

3)

Both the “shapers” and the “finishers” remove the debris and soft tissue from the canal and finish the preparation with a smooth continuous taper.

4)

The triangular cross-section of the instruments increases safety, cutting action, and tactile sense while reducing the lateral contact area between the file and the dentin.

5)

The modified guiding instrument tip can easily follow a prepared glide path without gouging side walls.

Canal preparation : Pro taper system : guidelines for use 1.

Prepare a straight-line access cavity with no restrictions in the entry path into the chamber.

2.

Fill the access cavity brimful with sodium hypochlorite and/or Prolube.

3.

Establish a smooth glide path with No. 10 and No.15 stainless steel hand files.

4.

Use maximum magnification to observe the movement of the rotary instrument. “Seeing” rotary apical movement is safer than simply “feeling” such movement.

5.

Use a torque-and speed-controlled electric motor, powering the handpiece at 200 to 300 rpm.

6.

Be much gentler than with hand instruments. Always treat in a moist canal. Irrigate frequently.

7.

Slow down! Each instrument should do minimal shaping. Only two, three, or four passes may be required for the file to engage restrictive dentin and carve the shape to the proper depth.

8.

Instruments break when flutes become loaded or when instruments are forced. Check the flutes frequently under magnification and clean them. Cyclic fatigue from overuse, or if the glide path is not well established, also leads to breakage.

9.

Pro taper instruments are disposable and, like all endodontic files and reamers, are designed for single-patient use. Sometimes instruments are even changed within the same treatment (e.g., in the case of a four-canal molar).


10.

Irrigate with 17% EDTA or a viscous chelator during the Pro Taper shaping.

Pro taper system : directions for use : 1) Establish proper access and a glide path with No.10 and No.15 stainless steel files to the working length or the apical constriction exit. 2) Floor the canal and chamber with sodium hypochlorite and begin shaping with the shaper S – 1 using multiple, passive-pressure passes. Go no deeper than three-quarters of the estimated canal length. Irrigate and recapitulate with a No.10 hand file, establishing patency to full working length. Now, with S – 1, extend the preparation to full working length. Again irrigate and recapitulate. 3) “Brush” with the Shaper S – X to improve the straight-line access in short teeth or to relocate canal access away from furcations in posterior teeth. 4) Shaping file S – 2 is now used to full working length. irrigate, recapitulate, and re irrigate. 5) Confirm and maintain working length with a hand file. (Remember, as curves are straightened, canals are shortened). 6) With finisher F – 1, passively extend the preparation to within 0.5 mm of the working length. Withdraw after one second! And only one second! The F-1 has a tip size of 0.20 mm, and if a No.20 hand instrument is found to be snug, the preparation is finished. With the instrument in place, radio graphically verify the exact length before final irrigation. 7) If the F – 1 and the No. 20 hand file are loose continue the preparation with the finisher F-2, which is 0.25 mm diameter at the tip. Confirm with a No25 hand instrument and, if snug, confirm the length radiographically, irrigate, and complete. 8) If the F-2 instrument and the No.25 hand file are loose, continue the preparation to just short of the working length with the finisher F – 3 file, which has a 0.30 mm tip diameter and follow with the confirming No. 30 instrument. If the No.30 is found to be snug, the preparation is finished. If this is loose, there are a number of techniques to enlarge the apical third to large sizes. 9) Frequent irrigation and file cleansing are imperative – irrigation and recapitulation. Now that the perfectly tapered preparation is complete, smear layer removal with EDTA and sodium hypochlorite is in order, followed by either medication and/or obturation.

QUANTEC SYSTEM :


-

The quantec series are marketed by sybro endo and analytic.

-

The quantec flare series have increased tapers all with tip sizes of ISO 25 and are designed to quickly and safely shape the coronal third of canal.

Available as : -

Quantec series consists of 10 graduated Ni-Ti tapers from 0.02 through 0.06 through 0.06 with ISO tip sizes.

-

The quantec flare series with increased tapers of 0.08, 0.10 and 0.12 all with tip sizes of ISO 25 are designed.

-

The quantec rotary instruments are uniquely engineered with slightly positive rake or blade angles on each of their flutes, these are designed to shave rather than scrape dentin.

-

Flute design includes a 30 degree helical angle with flute space that becomes progressively larger distal to the cutting blade.

-

More peripheral mass has been added to these files rather than depending on core strength alone as in other rotary systems.

-

Quantec’s wide radial lands are purported to prevent crack formation in the blades and aid in deflecting the instrument around curvature.

-

By recessing the radial lands behind the blade, there is a concomitant reduction in frictional resistance while maintaining canal centering.

-

With respect to tip geometry, the clinician has a choice of two designs. i) Sc – safe cutting tip ii ) LX – Non cutting tip

i) SC – SAFE CUTTING TIP : -

Sc-safe cutting tip is specially designed for small, tight canals, narrow curvatures and calcified canals.

-

This faceted 60-degree tip cuts as it moves apically as the tip approaches a curve, conceptually, a balance takes place between file deflection and cutting.

ii) LX – NON CUTTING TIP : -

It is non faceted bullet nosed tip

-

It acts as a pilot in the canal and deflecting around severe curvatures in less constriction canals.

-

They are recommended for enlarging the body and coronal segments and managing delicate apical regions.


Applications : -

The quantec flare series with increased tapers of 0.08, 0.10 and 0.12 all with tip size of 150 25 are designed to quickly and safely shape the coronal third of the canal.

-

Series of varying tapers are used to prepare a single canal.

-

The instruments are used at 300-350 rpm in a high-torque gear reduction, slow speed handpiece.

Advantages : Proponents of the graduating tapers technique claim that theoretically using a series of files of single taper whether it is a conventional 0.02 taper or greater taper will result in decreased efficiency as large instruments are used, that is more of the file comes into contact with the dentinal walls, making it more difficult to remove dentin as forces are generated over a larger area. Ultimately each instrument will become fully engaged along canal walls, potentially inhibiting proper cleaning and shaping of the apical canal. In contrast and in accordance with the graduating tapers technique, by restricting the surface contact between instrument and wall, an instruments efficiency is increased since the forces used are concentrated on a smaller area. In this technique for example 0.02 taper has shaped the canals, a 0.03 taper with the same apical diameter would engage the canal more coronally, by altering the taper from 0.02 to 0.03 and up the scale to 0.06., the efficiency of canal preparation is maximized by restricting surface contact. Canal preparation : The graduating tapers technique involves a modified step-down sequence, starting with a larger tapered file first and progressing with files of lesser taper until working length is achieved. The technique involves canal negotiation, canal shaping, and, finally, apical preparation. As in all instrumentation techniques, straight-line access to the canal orifices must be made first followed by passive negotiation of the canal using No.10 and No.15 0.02 taper hand files. A Quantec No.25, 0.06 taper, 17 mm in length, is passively used. In most cases, this instrument should approach the apical third of the canal; at this point, the working length must be established. A â&#x20AC;&#x153;Glide pathâ&#x20AC;? is now established for all subsequent quantec files by working No.10 and No.15 0.02 taper hand files along with sodium hypochlorite to the established working length. During the shaping, phase, each Quantec file, progressing sequentially from a 0.12 taper down to a 0.03 taper, is passively carried into the canal as far as possible. In all cases, light apical pressure must be applied, using a light pecking motion and never advancing more than 1 mm per second into the canal. Each instrument should be used for no more than 3 to 5 seconds. The sequence is repeated until a 0.06 or 0.05 taper reaches the working length. The apical preparation can then be deemed complete or further enlarged by using the Quantec standard 0.02 taper No. 40 or No. 45 rotary instruments or hand files. With the Quantec series, the correct amount of apical pressure must be maintained at all times; the continuously rotating instrument should either be inserted or withdrawn from the canal while allowing for


its slow apical progression. The instrument, however, should be withdrawn after the desired depth has been reached and not left in the canal transportation, ledge formation, and instrument separation. Thus, to reduce procedural problems, there should always be a continuous apical/coronal movement of the instrument, and, if the rotating file begins to make a clicking sound (file binding), one should withdraw the file and observe for instrument distortion. LIGHT SPEED ENDODONTIC INSTRUMENTS : The light speed rotary instrumentation system so named because of the light touch needed as the speed of instrumentation is increased, involves the use of specially engineered Ni-Ti Gates Glidden drill like reamers that allow for enhanced tactile control and apical preparations larger than those created via conventional techniques and other Ni-Ti rotary systems. Available as : -

The set of instruments consists of ISO-sized rotary files from size 20 through 100 including nine half sizes ranging from 22.5 through 65. The half size helps reduce stress on both the instruments and root during preparation and decrease the amount of cutting that each instrument must accomplish.

-

It is more flexible with slender and parallel shaft

-

The head has short cutting blades that only bond at its tip.

-

The light speed instruments has a short cutting blade with three flat radial lands which keeps the instrument from screwing onto the canal

-

A non-cutting pilot tip and a small diameter non cutting flexible shaft is smaller than the blade eliminates contact with the canal wall.

-

Laser-etched length control rings on the shaft eliminate the need for silicone stops.

-

The light speed instrument has a cross sectional “U” blade design in which flat radial lands with neutral rake angles enhance planning of the canal walls and centering of the instrument within the canal.

-

The helical blade angle and narrow shaft diameter facilitate debris removal coronally.

Mode of action : -

In most clinical cases about 8 to 14 instruments are needed.

-

They are used in continuous 3600 clockwise rotation with very light apical pressure in a slowspeed handpiece.

-

The recommended rpm is between 750-2000 rpm with preference towards 1,300 – 2,000 range.

Advantages : The clinician can prepare the apical portion of the canal with the head of light speed to a size larger than what could normally be produced using tapered instruments. -

The light speed head with its short cutting blades only binds at the tip, thus increasing the accuracy of the tactile feed back. This results in the rounded and the centered apical preparations.


Canal preparation : Following proper coronal access preflaring with Gates Glidden drills or another method is highly recommended. This working length established with at least No:15 stainless steel K-file. Prior to using the light speed in the hand piece, the clinician should first select and hand fit a No:20 light speed instrument that binds short of the working length. Once fitted, that Light Speed instrument is now inserted in the gearreduction, slow-speed hand piece. The Light Speed must enter and exit the canal at the proper rpm, preferably 1,300 to 2,000 rpm for smoother and faster instrumentation. As with other systems, the rpm must be kept constant to avoid abrupt changes that may result in loss of tactile feedback and instrument breakage. There are two recommended motions with LightSpeed: (1) if no resistance is felt, the LightSpeed is gently advanced to the desired length and withdrawn, or (2) if resistance is felt, a very light apical pecking motion (advance and withdraw motion) should be used until working length is attained. In either case, the instrument should never stay in one place as this increases transportation and enhances separation. This gentle pecking motion prevents blade locking, removes debris carnally, and aids in keeping the blades clean. Increasingly larger LightSpeed instruments are used to the working length, never skipping sizes, including the half-sizes. Irrigation should occur at least once after every three instruments. Once the apical stop has been established, the LightSpeed should never be forced beyond this point. If forced, buckling along the shaft may occur, potentially leading to fatigue and instrument separation The MAR, or Master Apical Rotary (the smallest LightSpeed size to reach the working length, yet large enough to clean the apical part of the canal), becomes the subsequent instrument that first binds 3 to 4 mm short of the working length. This instrument will require 12 to 16 pecks (i.e., 4 pecks per millimeter advancement) to reach the working length. This MAR, typically larger than the size achieved with most other methods, has been shown to clean the sides of the canal while remaining centered and creating a round preparation. The apical 4 mm of the canal is shaped used sequentially larger instruments in step-back sequence with 1 mm intervals. The remainder of the step-back is done by feel. Finally, the last instrument taken to full working length is used for recapitulation. The taper of a canal prepared with LightSpeed is approximately 0.025 mm/mm to preserve tooth structure. To prevent instrument separation from torsional overload or from buckling along the shaft (cyclic or bending fatigue), LightSpeed instruments must always be used with light apical pressure â&#x20AC;&#x201C;never forced. If the blade breaks off, it frequently can be bypassed. RAPID BODY SHAPERS: Rapid Body Shaper (RBS) (Moyco/Union Broach; Bethpage, N.Y.) consists of a series of four nickel-titanium rotary engine reamers. These instruments feature the patented nonledging Roane bullet tip and allow the practitioner to rapidly shape the body of the canal without the problems that occur using Gates-Glidden drills. The RBS instruments develop a parallel-walled canal shape. The RBS series


consists of four instruments: No. 1 (0.61 mm at the tip), No.2 (0.66 mm at the tip), No.3 (0.76 mm at the tip), and No. 4 (0.86 mm at the tip). Canal Preparation: Prior to using RBS, the apical region of the canal must be prepared with a minimum No. 35 ISO instrument to within 0.5 mm of the apex. The No. 1 RBS is then placed in a gear-reduction, slow-speed handpiece at 275 to 300 rpm and allowed to track down the canal 2 to 3 mm. Constant and copious irrigation is necessary at all times. The RBS is removed to clean the fluting and is reinserted to track another 2 to 3 mm down the canal. This sequence is repeated until the No. 1 RBS is within 4 mm of the apex. The No. 2 RBS is then used like the No. 1, also to within 4 mm or shorter form the apex. The No. 3 RBS, followed by the No. 4 RBS, is used to within 7 mm of the apex, completing the body shaping. The No.1 RBS will feel very aggressive, whereas the No. 2 through 4 RBS feel almost passive in comparison. Apical refinement is subsequently completed by hand instruments or via Pow-R nickel-titanium rotary instruments. POW-R NICKEL-TITANIUM ROTARY FILES: Pow-R Nickel-Titanium Rotary Files (Moyco/Union Broach; Bethpage, N.Y.), also with a nonledging Roane bullet tip, are available in both 0.02 and 0.04 tapers and, owing to their taper design, allow the practitioner to clean and shape the middle and apical regions of the canal in a conservative manner. These instruments come in standard ISO instrument sizes as well as in half sizes 17.5, 22.5, 32.5, and 37.5 for more precise apical refinement. They follow standard ISO color codes as well. Canal Preparation: Once Gates-Glidden drills are used to prepare and shape the coronal region of the canal in a stepdown manner, and the canal has been at least partially negotiated with hand files, Pow-R files can be used. The clinician should select a file that binds at its tip in the middle third and begin to gradually move and push that file as it is rotating, slightly withdrawing it every 0.25 mm penetration until no more than 2 mm of depth is achieved or until resistance is felt. Like any other nickel-titanium file, these instruments must be used passively and with a light touch or pecking motion. The working length should now be determined using a hand file. Constant recapitulation with hand files is the rule along with constant irrigation. The next smaller Pow-R file is used to continue shaping an additional 1 to 2 mm deeper. Rotary instrumentation continues, decreasing sizes in sequence until the shaping is about 1.5 mm short of the apical foramen. The remaining portion of the canal can be finished with hand instruments or with Pow-R files. If more flare is needed, particularly if an obturation technique that requires deep condenser penetration is considered, a rotary incremental step-back can be used to generate additional space in the apical and middle portions of the canal.


Both the RBS files and Pow-R instruments are used in high-torque, gear-reduction handpieces with rpm ranging form 300 to 400. HERO-642 : -

This is the newest instrument which has a different design from earlier successful rotary instruments.

-

Hero-642 has a trihelical hedstrom design with rather sharp flutes. There is increased distance between flutes. The change in the helical angle for the flutes there is reduced risk for binding in the root canal.

-

Hero-642 is designed to operate at 500-600 RPM.

-

This instrument is available is ISO sizes of No:20 to No:45.

-

All sizes are available in 0.02 mm/mm taper No:20, No:25 and No:30 also are available in 0.04 and 0.06 mm/mm taper.

-

Hero 642 has a central core that provides extra strength. Despite its design the instrument is easy to operate; with no higher apparent fracture risk than other rotary instruments.

-

A crown down technique is recommended with an apical preparation of atleast size No:30.

RACE (REAMER WITH ALTERNATIVE CUTTING EDGES) : -

It is triangular in cross sectional design

-

It has sharp cutting edges.

-

It has unique alternative cutting edges. This eliminates screwing in and blocking in action to decrease working torque.

-

It has a non-cutting tip

-

Chip dislodgement may be noticed due to its sharp cutting edges.

-

It consists of 16 instruments. 5 are pre race 11 are race

K3 FILE SYSTEM : -

K3 file system is designed by Dr. John and Mc Spadden.

-

They are available as K3 canal shaping files

-

K3 body shaping files.

K3 CANAL SHAPING FILES : -

They are available with a fixed taper of 0.02, 0.04 and 0.06.

-

0.02 taper instruments are available in sizes No:15 through No:45 and 21, 25 and 30 mm lengths.


-

O.04 and 0.06 taper instruments are available in size No:15 through No:60 and 21, 25 and 30 mm lengths.

K3 BODY SHAPING FILES : -

They are available in 0.08, 0.10 and 0.12 tapers

-

They are available as only size No:25.

-

Different lengths available are 17, 21 and 25 mm.

-

Position rake angle provides more effective cutting then the negative rake angle.

-

Variable core diameter enhances flexibility over the length of the instrument.

-

A series of 3 radial lands with a relief between two of the three lands reduces friction on canal wall.

-

The proportion of core diameter to out side diameter is greater at tip where strength is most needed. The proportion then decreases uniformly as fluting moves up the taper resulting in greater flute depth and increased flexibility while maintaining strength.

-

Access handle design shortens file handle by approximately 5 mm with out affecting working length of file.

-

The instrument with variable pitch prevents the screwing in effect.

-

It has safe ended cutting tip.

ENDO SEQUENCES : Endo sequence technology has been designed to generate predictability in obturation through a matching system of laser verified gutta-percha cones, creating synchronicity between a machined preparation and master cone. Available as : BLANK DESIGN : They introduced alternate contact points along the cutting surface of instruments. -

This keeps file in the center of canal

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This limits the engagement and has the decreased torque of the file as it is sharper, less bulky and more flexible.

TIP DESIGN : It uses a precision tip which is non cutting tip that becomes fully engaged at D 1. This results in safety combined with efficiency. Metal treatment : Historically Ni-Ti instruments have been polished in a drum but they are subjected to a process called â&#x20AC;&#x153;electro polishingâ&#x20AC;?. This will remove many of imperfections than can lead to separation. This keeps instrument edge sharper, cleaner and more durable.


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The are available in variable pitch and helical angles which gives more control

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Because of the reamer like design i.e. alternate contact points and sharp edges it is having superior cutting efficiency.

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It is used with rpm of 500-600 rpm.

V-TAPER FILES: The V-Taper™ Rotary System is a set of three variable taper NiTi rotary files. The V-Taper™ Rotary System will allow you to complete most root canals using 2-3 files. This performance-enhanced system is easier, safer, more efficient, and less expensive than any other NiTi rotary file system available. With the V-Taper™ Rotary System, you will perform your best root canals. V-Taper™ Rotary System—3-File Set 30 (V10) —> 25 (V08) —> 20 (V06) Design: -

When the first K-file was introduced nearly 100 years ago, a constant-tapered instrument was the only shape that could be formed with the technology of the time.

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The problem with a constant-tapered instrument is canals do not have a constant taper. Constanttapered instruments “fight” the natural variable taper of the canal (like trying to fit a square peg into a round hole). Due to the inherent design of a constant-tapered instrument, it will always under-prepare the apical 1/3 taper and over-prepare the coronal 2/3 taper, and require too many instruments to complete a case.

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But now with superior grinding machines, CAD-CAM, and instrument design, it is possible to produce a V-Taper™ file that simulates the natural variable taper of the canal. This allows the dentist to complete high-quality cases more safely, easily, quickly, with fewer files, and less expensively than ever thought possible.

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The V-Taper™ Rotary Files will “properly prepare” the shape of the canal.

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This will result in higher-quality cases that are easier to irrigate and obturate, and considerable savings in time and instrument costs to reduce overhead. And this is all done without overpreparing the tooth while maintaining a conservative straight-line access for a successful final restoration.

LIBERATOR FILE Rotary NiTi problems: File Separation, Complicated Techniques Here's why Liberator is the safe, efficient and easy solution: 1. Straight-flute design cannot self-thread 2. Lack of radial land areas reduces friction 3. Higher RPM reduces torque forces 4. Roane safety tip keeps file centered


5. Efficient removal of dentin 6. Manufacturing process eliminates transverse micro-cracks 1. Straight â&#x20AC;&#x201C; flute design cannot self-thread Several studies have shown that self-threading is a precursor to file separation. Since most rotary endodontic instruments are helically-fluted- like a wood screw - they have a natural tendency to selfthread. Liberator rotary NiTi file is a straight-fluted instrument. In a controlled study, Liberator demonstrated 0% self-threading: Self-Thread

study

using

acrylic

blocks

in

controlled

apparatus.

N=20.

Profile and K3 are not trademarks of Miltex, Inc. 2. Lack of radial land areas reduces friction : Radial land areas are required for conventional helically-fluted files because they prevent the file from over-engagement in the canal (see file cross-section at left). If a file becomes suddenly engaged or self-threaded, it may fracture. Radial lands are especially important for files that have positive rake angles. That is, the angle of attack of the cutting blade is similar to a snow plow - which is forced downward toward the surface of the pavement....resulting in friction and sparks! Liberator rotary files have no land areas. The only friction is the file abrading tooth structure. 3. Higher RPM reduces torque forces: Liberator instruments operate at RPMs of 1,000 to 2,000 because they can without self-threading! High RPM offers the benefit of lower torque. Torque is the twisting force that causes file separation. Electric motors offer the horsepower required to drive an endodontic file, which is typically referred to as electric motor load. The most common equation for power based electric motors on torque and rotational speed is: hp = (torque X rpm)/5,250. Here

is

the

same

equation

that

defines

torque:

Torque

=

(HP

X

5252)/RPM

For example, as RPM is increased from 350 to 2,000; torque is decreased by a factor of 5.7! The machine tool industry has advanced the concept of using reamers at high RPM. These instruments are used when placement of pins require a smooth finish at very accurate tolerances.

4. Roane safety tip keeps file centered: Dr. James Roane developed the Roane safety tip that minimizes ledging and transportation. It also helps center the file in canal. This tip design is used on all Liberator NiTi rotary files. Proven: The Roane safety tip has been used for Flex-RÂŽ hand files for the past 15+ years.


5. Efficient removal of dentin : Liberator NiTi rotary files quickly remove dentin because of their sharp cutting blades moving at high velocity. In endodontics, the amount of work required to remove dentin can be expressed as kinetic energy. Using a proven formula for kinetic energy (KE), we can show how Liberator files deliver significantly higher KE: Formula1 KE=1/2 X MV2

Liberator File: 2,000 RPM KE=1/2 X M(2,000)2 or KE=1/2 X M(4,000,000) Liberator delivers 32 times* more KE!

Conventional Rotary: 350 RPM KE=1/2 X M(350)2 or KE=1/2 X M(122,500)

6. Manufacturing process eliminates transverse micro-cracks: Liberator rotary NiTi files are manufactured with a unique patent-pending process using electrochemical grinding (ECG) techniques. This process employs a liquid chemical that decreases the thermal impact of the grinding process. In contrast, high surface temperatures are achieved with conventional processes that result in heat affected zones on the file. These heat affected zones impact the surface hardness (brittleness) and may impact the potential for file separation. The direction of the grinding wheel for Liberator files is parallel with the axis of the file. This compares to conventional files where the grinding wheel is perpendicular to the file axis - resulting in transverse microcracks. These micro-cracks have been attributed to file separation.


Endodontic instruments11/ dental implant courses by Indian dental academy