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MINIMAL INTERVENTION: RECENT MODIFICATIONS IN AMALGAM CAVITY DESIGN 1.

INTRODUCTION

2.

CONCEPT

3.

GOALS

OF

OF

MINIMAL INTERVENTION DENTISTRY.

MINIMAL

• PREVENTION

OF

INTERVENTION.

DC, DEMINERALIZATION,

AND

EARLY

LESIONS.

• REDUCTION

IN CARIOGENIC BACTERIA.

• MINIMUM

SURGICAL INTERVENTION OF CAVITATED LESIONS.

• REPAIR

RATHER

THAN

REPLACEMENT

OF

DEFECTIVE

RESTORATIONS.

4.

MODERN /

CONVENTIONAL CONCEPTS OF CAVITY DESIGN IN

AMALGAM RESTORATIONS.

5.

CONCLUSION. 1


INTRODUCTION: The term minimal intervention dentistry is relatively new in dentistry and has of late been used to suggest to the profession that it is time for a change in the principles we have been following in operative dentistry.

The disease should be treated first, and the surgical

intervention should be a last resort and that too with removal of as little tooth structure as possible. Treatment should begin with identification and elimination of the disease. Restorations by themselves will not and cannot prevent or eliminate further incidence of the disease. Natural enamel and dentin are still the best dental “materials� in existence; therefore, minimally invasive procedures that conserve a greater part of the natural, healthy tooth structure must be considered desirable. Minimally invasive procedures are beneficial from a patient’s standpoint as well.

There is less discomfort and less need for local

anesthesia. There is also a real prospect that the repaired natural tooth will last a lifetime.

The replacement of amalgam restorations leads to

larger restorations that have shorter life spans and the replacement procedures themselves may cause damage to adjacent healthy teeth. In this seminar I shall be discussing about the current concepts, newer materials techniques and instruments that make conservative dentistry practical and ultra conservative dentistry a reality.

Adhesive

restorations eliminate the need for more extensive retentive preparations. CONCEPTS OF MINIMAL INTERVENTION: The concept of minimal intervention dentistry has evolved as a consequence of our increased understanding of the carious process and the development of adhesive restorative materials. 2


It is now recognized that demineralized but not cavitated enamel and dentin can be “healed” and that the surgical approach to the treatment of carious lesion as proposed by G.V.Black is no longer tenable. Principles of minimal intervention are based on: 1. Accurate caries diagnosis. 2. Classification of caries severity using radiograph. 3. Assessment of individual caries risk (high, moderate, low). 4. Arresting active lesions. 5. Remineralizing and monitoring of cavitated arrested lesions. 6. Placement of restoration in teeth with cavitated lesions using minimal cavity designs. 7. Assessing disease management outcomes. GOALS OF MINIMAL INTERVENTION DENTISTRY:  Prevention of caries.  Reduction in cariogenic bacteria.  Remineralization of early lesions.  Minimum surgical intervention of cavitated lesions.  Repair rather than replacement of defective restorations. PREVENTION OF CARIES AND REMINERALIZATION OF EARLY LESIONS:

 Dental caries is an infectious microbiologic disease of the teeth that results in localized dissolution and destruction of the calcified tissues.  Dental caries is infectious disease requiring a susceptible host, cariogenic micro flora and a diet high in refined carbohydrates to sustain that flora.  In the presence of all three factors there may be demineralization of dental hard tissues, particularly in those areas in which there is potential space for the micro flora collect and mature.

3


NEWER CLASSIFICATION OF DENTAL CARIES BY SITE AND SIZE:  At the FDI World Delta Congress held at Kaula Lampur, Malaysia in September 2001, Dr.Graham Mount said that “For the first time in almost a hundred years we are now being released from the cavity classification proposed by Dr.G.V.Black”. He classified cavities as follows by size and site.

SIZE SITE Pit and (1) fissure Contact area (2) Cervical area (3)

Minimal

Moderate

Enlarged

Extensive

(1)

(2)

(3)

(4)

1.1

1.2

1.3

1.4

2.1

2.2

2.3

2.4

3.1

3.2

3.3

3.4

Site (1): Describes all lesions originating in pits, fissures and other defects on otherwise smooth surfaces of the enamel of the crown of a tooth. It includes all lesions described in Black’s class-I classification but also encompasses other smooth surfaces. Site (2): Describes all lesions associated with contact areas and includes both anterior and posterior teeth. This also includes all of Black’s classII, class-III and class-IV lesions. Site (3): Describes all lesions originating close to the gingival margin, in either enamel or dentin, around the full circumference of a tooth. This includes Black’s class-V cavity and also extends to root surface lesions occurring on mesial or distal tooth surfaces following gingival recession. Size: The size description gives guidance for the management of any site. 4


Size (1) (minimal) is a lesion that has progressed to the point where it is just beyond remineralization so that surgical intervention is indicated. Size (2) (moderate) is a larger lesion but there is still sufficient tooth structure

remaining

to

support

the

restoration

without

further

modification of the cavity beyond caries removal. Size (3) (enlarged) is a more extensive lesion that leaves remaining tooth structure at risk of further bulk failure through the development of a split at the base of a cusp or loss of an incisal corner. -

The cavity design will have to be modified and enlarged so that the restoration will take the main occlusal load to protect the remaining tooth structure from undue stress.

Size (4) (extensive) is a lesion in which there has already been serious loss of tooth structure. Such as the loss of a cusp from a posterior tooth or involvement of incisal edge of an anterior tooth. -

The classification is linked with the stage of progression of the lesion and is not related to cavity designs.

CARIES RISK ASSESSMENT: Mouth Mirror Probe Explorer Radiographs

-

Assessment tools.

-

Patient history.

-

Clinical examination.

-

Nutritional analysis.

-

Salivary analysis.

-

Accurate caries diagnostic methodologies.

PATIENT HISTORY: -

Can help identify high-risk patients. 5


-

Factors include age, gender, fluoride, exposure, smoking habits, alcohol consumption, general health and medication, dietary habits, economic and educational status.

-

Children and elderly adults have increased risks and decreased fluoride exposure; lower economic status and lower educational attainment also increase risk.

Clinical examination: -

Inadequate salivary functioning, plaque accumulation, inflammation of soft tissues, poor oral hygiene, cavitated lesions and existing restorations are also indicative of potential for caries development.

Nutritional analysis: -

Frequent

exposure

to

sucrose

increases

likelihood

of

plaque

development with more acidogenic mutants streptococci organisms. Salivary analysis: -

Analyzing saliva may provide important information about secretion rates and buffering capacity as well as the actual numbers of streptococci and lactobacilli.

-

Knowing the high values of CFU (Colony Forming Units) might be helpful in identifying and educating high caries risk patients.

Accurate caries diagnostic methodologies: -

The most widely used methods are visual inspection and bitewing radiographically but the value of both these for accurate caries diagnosis has been questioned.

-

Minute lesions may be quite difficult to diagnose with traditionally accepted techniques.

The shape of pit and fissure lesions tends to

mask the defect when the dentist is using an explorer, as the narrow occlusal opening prevents the entry of the instrument into the lesion. -

Radiographs can detect caries when non are observed clinically, but all too often there are caries present in the tooth that the radiograph will not reveal. This is known as hidden caries. 6


-

The dilemma of diagnosing these small carious lesions at an early stage is a very real problem that cannot easily be solved by existing diagnostic procedures or techniques.

Newer methods that are promisingly sensitive enough and specific enough for current diagnosis are: -

Quantitative light induced fluorescence (QLF).

-

Fiber optic transillumination (FOTI).

-

Light scattering.

-

Laser fluorescence.

-

Ultra-violet illumination.

-

Penetration of dyes.

-

Iodide penetration.

-

Ultrasonic imaging and

-

Improved radiographic imaging technique.

Quantitative light induced fluorescence: Light scattering is a measure of the observed whiteness of carious lesion that can be correlated with degree of mineral loss. Fiber optic transillumination: The basis for fiber optic transillumination is that the decayed tooth material scatters light more strongly and thus has a lower index of light transmission than sound tooth structure. This decrease in transmission is interpreted by the observer, traditionally on an ordinal rating scale. Ultraviolet illumination: Ultraviolet light has been used to increase the optical contrast between the carious region and the surrounding sound tissue. 7


The natural fluorescence of enamel, as seen under ultraviolet illumination, is decreased in areas of less mineral content, such as in caries lesions, artificial demineralization, or developmental defects. The caries lesion appears as a dark spot against a fluorescent background. Electrical conductance measurements (ECM): The theory behind ECM is the observation that sound surfaces should possess limited or no conductivity that will increase with increasing demineralization. Enamel demineralization results in increased porosity and saliva fills the pores and forms conductive pathways for electrical current. With decreasing thickness and increasing porosity, performance of ECM has been reported to be as valid or as better than more traditional means of diagnosing fissure caries. Direct digital radiography: This is done using RVG. Advantage is that contrast enhancement of the gray level of interest can be achieved by filter technique. Digital fibreoptic transillumination: Practical method of imaging teeth. Illumination is delivered by means of fiber optics from a light source. Resultant changes in light distribution as the light transverses the teeth are then recorded as image for analysis. DFOTI can detect incipient and recurring caries before they are visible on radiographs. Pulsed laser caries detector: A recent development is the caries detector based on a low level, pulsed laser.

8


When the incident light meets a change in mineralisation, it stimulates a fluorescent light of different wavelengths, which inturn can be translated into an acoustic signal. The wavelength can also be read as a number readout. This device also has its limitations because the depth of penetration of light is limited to 2 mm. Iodide Penetration (IP) Dye: In a study potassium iodide was applied for a specified period of time to well-defined area of the enamel surface and thereafter the excess was removed. The permeability was estimated by measurement of the quantity of iodide that could be elicited from the test area. Ultrasonic Imaging: Ngo et.al. (1988) For detecting early caries in smooth surfaces. They

conducted

a

double

blind

experiment

where

in

vitro

demineralization of the natural labial surface of enamel was assessed by densitometric tracings of contact micro radiographs and by the ultra sound pulse echo technique. They showed that artificial enamel lesions with less than 57% of the sound enamel mineral content in the body of the lesion could be differentiated acoustically from interact enamel on the basis of amplitude changes of the enamel surface echo and amelodentinal junction echo. Prevention of DC: There is the mistaken belief that drilling out a caries lesion and placing a restoration eliminates the bacteria and thereby stops caries progression. Although traditional restorative work may eliminate the bacteria at the site of the restoration, the remainder of the mouth is left untouched, caries continued unchecked in the remainder of the mouth and recolonization commences. It is logical, therefore; 9


-

To use antibacterial therapy such as treatment with chlorhexidine gluconate rinse as a caries preventive measure.

-

Other modes are by demineralization – remineralization concept.

-

Treatment and management of precavitated and non-cavitated lesions.

-

The initial approach is focused on management of caries as an infectious disease.

The most important principles of preservative

dentistry are to delay operative intervention for as long as possible to assess whether they have progressed through 1/3 or more the thickness of dentin. -

Caries process was once thought to be irreversible and continuous, beginning with enamel demineralization followed by protein (collagen) degradation.

-

It is now recognized that enamel and dentin demineralization is not a continuous

process

and

is

reversible.

Demineralization,

remineralization cycle wherein tooth alternatively loses and gains Ca + and PO4 ions depending on microenvironment is a reality. REDUCTION IN CARIOGENIC BACTERIA: Pathological and Protective factors: Caries progression is opposed by both these factors by maintaining a balance between them. Protective factors: Saliva: essential for the protection of the tooth against dental caries and provides many natural protective factors including calcium, phosphate and antibacterial components and other proteins with various functions.

Bacterial clearance: Adults produce 1 to 1 ½ litre of saliva per day, very little of which occurs during sleep. 10


The flushing effect of this salivary flow itself is adequate to remove virtually all microorganisms not adherent to tooth structure. Direct antibacterial activity: Salivary glands produce an array of antimicrobial products like lactoferrin, lysozyme, lactoperoxidense and agglutinins. Buffers: Volume and buffering capacity of saliva available to tooth surfaces have major role in protection (concentration of bicarbonate ion). Other molecules that are present in saliva that are responsible for an increase in pH are urea and hysine; hydrolysis of either these will lead to formation of ammonia, causing pH to raise. Remineralization: 1. Saliva and plaque fluid are supersaturated with calcium and phosphate ions, which provides a constant opportunity and thus can help protect the teeth in times of cariologic challenge. 2. Extrinsic antibacterial agents such as chlorhexidine also can be considered as protective factors in this balance, as can fluoride from external sources. Prolonged and slightly elevated low concentrations of fluoride in the saliva and plaque fluid decrease the rate of enamel demineralization and enhance the rate of remineralization. Fluoride brings down the pH to 4.5 converting hydroxyapetite to fluorapetite crystals, which makes it resistant to caries attack. Fluoride is mildly bacteriostatic, it also increases surface energy of enamel thus reducing plaque accumulation.

Pathological factors: Include cariogenic bacteria and the frequency of ingestion of fermentable carbohydrates that sustain these bacteria. 11


Genetic factor: Some are genetically immune to caries. Medical management of D.C. includes: Two elements to the biological approach: 1. Alteration of oral environment in order to minimize demineralization. 2. Application of agents such as chlorhexidine and topical fluorides. Alteration of oral environment: General modalities: 1. Reduced frequency of refined carbohydrates intake. 2. Optimum plaque control. 3. Optimum salivary flow. 4. Patient education Identify the micro flora: Modification of the oral micro flora is essential in the initial stages, and relatively simple tests are available to assess the micro flora in the dental office. Simple test tube cultivation takes upto 48 hours to confirm the presence or absence of pathologic levels of infection.

This will provide

visual proof to the patient and assist motivation. Test for salivary flow: Salivary flow testing can often be carried out in conjunction with the test for bacterial flora. Saliva plays a significant role in the health of the oral cavity because it stabilizes the continuing ion exchange with the tooth surface. Prescribe a chlorhexidine mouthwash:

12


Modification and control of the balance of the oral micro flora are essential,

and these

can

best

be

achieved through the

use

of

chlorhexidine as a mouthwash over a short period. Streptococcus mutans is very susceptible to a twice daily rinse with 0.2% chlorhexidine. Prescribe a topical fluoride application: The patient should be given a prescription for daily or weekly home use. Place transitional restorations in all open cavitated lesions: -

It is necessary to eliminate all areas that are not readily accessible to the patient for the control of plaque.

-

A transitional restoration is defined as one that will last a reasonable period of time and as long as it remains in place, completely seal the lesion from further infection and after some degree of biologic activity to help stimulate repair and healing.

-

Logically, it will incorporate the use of adhesive, biometric material that has acceptable physical properties.

Fluorides, antimicrobial agents, Pit and fissure sealants: Although fluoride treatments are effective in preventing smooth surface caries, they are less effective in preventing pits and fissure caries. III. MINIMUM SURGICAL INTERVENTION: Cavitated lesions: -

In case of cavitated lesions as the cavity becomes larger, there is an increasing need to consider protection of remaining cusps because they become seriously weakened by loss of the central core of the crown and therefore become subject to the development of splits at the base.

-

For larger cavities, special consideration needs to be given to the strength of the restorative material (like lamination technique).

-

Amalgam should not be entirely discarded as an option because it has greater strength than both glass ionomer and resin composite and is 13


still useful for the restoration of extensive cavities and for protection and retention of weakened cusps. -

None of the available restorative materials is entirely satisfactory in the long term.

-

Surgical intervention should only follow after a period of observation and education.

-

After the disease has been controlled, it is necessary in the smaller early lesion to eliminate cavitation in the tooth crown so that plaque can no longer accumulate and in the larger lesions, to restore function.

-

Cavity design should be predicated entirely on the extend of the lesion and should not be dictated by a preconceived notion of a geometric pattern.

Infected dentin Vs. affected: -

Restorative dentistry is based on the assumption that bacterial infection of demineralized dentin should prompt operative intervention.

-

A caries detector dye(basic fuchsin dye) can be used as an aid to indicate infected dentin during cavity preparation.

-

Conventional tactile and optical criteria are also found to be satisfactory

in

assessing

the

carious

status

of

tissue

during

excavation. -

Once the lesion has advanced to surface cavitation and the dentin is involved, the contents of the cavity can be roughly divided into two layers.

An infected layer:

14


On the outer surface of the cavity the tooth structure in this layer is completely denatured and laden with microorganism. An affected layer: -

A relatively sterile, softened demineralized inner layer, generally identified, as the affected layer will still contain the original collagen framework that is capable of demineralization.

-

Full control of caries requires elimination of the infected layer and also the cavitation that is allowing bacterial plaque to be retained. In the absence of bacterial plaque demineralization cannot progress.

-

It is now been demonstrated that the affected layer can be remineralized as well, provided it is sealed under a biomimetic restorative material.

Coming to the restoration of the cavitated lesions: 1.

Control of caries is essential prior to placement of restorations, otherwise it will continue and restorations will not last.

2.

Preservation of tooth structure and maintenance of occlusal relationships are essential in the design and construction of all restorations.

3.

The development of restorative materials that are both esthetic and adhesive has opened new possibilities in cavity design. Extension for prevention is no longer a valid concept. Mechanical interlocking designs are required for retention, and

unsupported enamel can often be supported and retain through the sue of adhesive materials. 4.

The combined use of glass ionomer and resin composite in a lamination technique has opened a variety of possibilities in modification of cavity designs. 15


5.

However, a point will be reached where the remaining cusps are so undermined and weakened that it is necessary to sue the restoration to protect them from occlusal load. A modification to a standard cavity design is suggested that will

offer the potential to protect the cusp and at the same time, help to preserve the occlusal height, thus facilitating restoration of the occlusal anatomy at the correct level. 6.

Longevity should always be the ultimate goal of restorative dentistry. Some compromise in esthetics may be justified with the object of retaining as much natural tooth structure as possible for long term wear.

According to G.J.Mount (2000), restoration of occlusal lesions (Site 1, sizes 3 and 4): -

It is suggested that glass ionomer should be used for the transitional restoration following removal of the infected layer of dentin from the surface of a large cavity (site 1, sizes 3 and 4).

-

It will adhere to both enamel and dentin through an ion-exchange mechanism, thus eliminating microleakage.

-

It also helps in remineralization due to the fluoride release. This is because in the presence of water from the positive dentinal fluid flow that follows, there will be calcium, phosphate and fluoride ions exchanged between the GIC and the demineralized dentin.

-

The entire filled GIC can be removed after three months, and the cavity can be inspected and modified as required.

-

If there is no doubt about the integrity of the cavity, then there is a choice between leaving the glass ionomer as the final restoration or laminating it with another material.

This technique is titled under

ART (Atraumatic Restorative Treatment). -

This is the technique of removing infected dentin only and sealing the cavity with GIC is just valid in general practice where normal 16


instrumentation is available and a further review of the restoration can be undertaken relatively simply. Restoration of proximal lesions (site 2, size 3 and 4): -

The principles for this are same as that of occlusal.

-

In gaining access to the affected demineralized dentin, there is no need to remove enamel just because it appears to be unsupported according to old surgical principles.

-

However, walls of the cavity should be cleaned of all infected dentin to allow development of the full ion-exchange adhesion with the GIC.

-

Demineralized dentin can remain on both the axial and pulpal walls on the assumption that it will remineralize under the influence of the glass ionomer.

-

Placement of an additional subliner, such as calcium hydroxide is contra indicated because it will interfere with the development of the ion exchange adhesion, and glass ionomer will not irritate the pulp.

-

The retentive elements should always be developed in the gingival one third of tooth crown and must be designed to encompass the central core of dentin containing the pulp chamber.

-

Ditches and Grooves are preferred to pins, which have a limited life expectancy, often lead to micro cracks and may pose a risk to pulp.

-

They make a very satisfactory base or core for a full or three-quarter crown and if the retentive elements of the amalgam have been properly developed, they will remain in place despite further removal of tooth structure for a more elaborate restoration.

CONCEPT OF BIO-MIMETIC MATERIAL: -

The term bio-mimetic suggests “imitation of nature�.

-

It also implies that the material should be bio-compatible. 17


-

Glass ionomer has been shown to fulfill these requirements not only in the oral environment, but also in relation to osteoid tissues elsewhere in the body.

-

The two most important properties in the context of minimal intervention dentistry are adhesion to tooth structure and release of fluoride and other ions.

-

Adhesion arises a result of an ion-exchange between the tooth structure and the cement.

-

The poly alkenoic acid from the glass ionomer attacks the tooth surface releasing Ca, PO4 and Al ions released from the glass, forming a new material, which unites the two.

-

There will also be a degree of adhesion between the acid carboxylate groups and dentinal collagen.

-

The strength of the union is dependent upon the tensile strength of the cement itself and any failure will be cohesive within the cement.

Other materials are: -

Metal modified GIC.

-

Resin modified GIC (Acid base).

-

Composite resins.

-

Poly acid modified resins (compomers)

-

Combinations (bilayered technique.)

Rotary and non-rotary methods of cavity preparation: Mechanical

Rotary Methods. Non-rotary methods.

Photo ablation – lasers. Mechanical rotary methods include flexible, oscillating diamond coated file in combination with ultrasonics. Mechanical non-rotary includes 18


hand excavators and air abrasion developed in 1940. -

It is the importing of kinetic energy to tiny aluminium oxide particles that are projected by a stream of compressed air or gas and expelled from a small nozzle.

-

The force generated by the relatively hard particles striking a relatively hard surface is sufficient to cut into that surface.

Chemo-mechanical methods: Caridex and carisolv. Photo ablation: LASERS: Er:YAG are used for the inhibition of progression of dental caries by altering the composition of surface enamel or dentin mineral. CAVITY DESIGN FOR MINIMAL INTERVENTION: 1. ART. 2. Preventive resin restoration. 3. Tunnel or “Internal� preparations. 4. Mini box preparations. 1. ART: Caries removed with hand instruments. Cavity / pit and fissures are cleaned with weak acid. A restorative material, which bonds chemically, to tooth is then placed.

2. Preventive resin restoration: In 1923, Hyatt proposed prophylatic odontotomy procedure.

19


Bunocore predicted the potential benefits of using acid etch technique for caries prevention in pit and fissures. Thus resin restoration came into use. Flowable composites, compomers 3. Tunnel preparation: by Jinks (1963) -

The tunnel or “internal” restoration to restore an approximal caries lesion was first described in 1984.

-

The technique allows the operator to conserve the important external anatomical features of the tooth, thereby saving considerable clinical time while leaving relatively little of the material externalized.

-

The development of new generation of glass-ionomer material with higher flexural and compressive strengths appear to satisfy the main objective of carious dentin replacement facilitated by a “key hole” internal preparation.

-

Traditional preparation cause weakening of the cusps and therefore creating a risk of future tooth fracture but the restorations can suffer from poor marginal adaptation.

-

The final restoration is frequently a poor copy of the original anatomy of the tooth and does not replicate the occlusal relationships that previously existed.

-

Concept of tunnel preparation is simple. Better access to larger caries lesions was suggested by extending the access entrance to the shape of a “T” to allow better instrumentation in cleaning peripheral caries or by making a more ovoid access cavity in the bucco-lingual plane.

Mini box preparation: 20


-

Developed to treat caries lesion in approximal surfaces while preserving as much tooth as possible marginal ridge is removed which makes it different from tunnel preparation.

-

Box shaped and saucer shaped preparations have been cited in literature the former has an angled form that the later has a rounded form cavity is filled with resin composite or glass ionomer.

Repair rather than replacement of restorations: -

This continues to be one of the most important problems in dentistry today.

-

Although the longevity of the restorations depends on different factors including the type of the restoration, the materials used, the dentition, the age of the patient, and the operator.

-

Replacement frequency and sec caries should be reduced by the addition of fluoride and other antimicrobials into dental materials, combined with the development of better adhesive systems to reduce microleakage.

-

Development of better diagnostic systems that allow the dentist to detect and monitor these lesions at an early stage might permit the testing of enhanced methods to remineralize or arrest them without having to replace the restoration.

RECENT CONCEPTS: These concepts came into picture due to: 1. Improvement in quality of restorative materials. 2. Decrease in caries incidence in western countries after water fluoridation. 3. Multimedia information the patient gets from audiovisual aids and advertisement. 4. Change in size of burs and bur material (carbide to diamond). Modern design replacing conventional design: 1. Service by newer amalgam is superior. 21


2. Minimizes pulpal irritation since loose tooth structure is removed. 3. Strength of remaining tooth structure is not decreased. 4. Longevity of restoration is increased. 5. It decreases the replacement rate of amalgam restoration. 6. Better understanding of tooth flexure theory. Class – I CONVENTIONAL

MODERN

EXTENSION FOR PREVENTION.

CONSERVATION

NO SWEEPING CURVES.

SWEEPING CURVES.

WIDE AND SHALLOW CAVITIES.

NARROW AND DEEP CAVITIES. INITIALLY CONVERGENCE WAS

OCCLUSAL CONVERGENCE WAS GIVEN M, L, D AND B WALLS.

LIMITED TO B & L WALLS. RECENTLY CONVERGENCE IS GIVEN ONLY TO THE WALLS OF FUNCTIONAL CUSP.

IF THE CAVITIES ARE ON CUSP TIPS, CAVITIES WERE UNITED. SPREAD OF FUTURE DECAY

SEPARATE PITS. AIM IS CONSERVATION OF

WAS GIVEN MORE IMPORTANCE. TOOTH STRUCTURE.

22


Class-II CONVENTIONAL

MODERN

OCCLUSAL CUTTING

MORE CONSERVATIVE

RESEMBLES G.V.BLACK’S.

APPROACH.

CONVENTIONAL DESIGN ACCORDING TO BLACK WAS BILATERAL TRUNCATED APPEARANCE.

INVERTED UNILATERAL APPEARANCE ON THE SIDE OF MARGINAL.

WIDTH OF ISTHMUS WAS 1/3 OF WIDTH OF ISTHMUS SHOULD BE INTERCUSPAL DISTANCE.

¼ OF INTERCUSPAL DISTANCE. SINCE THE CAVITY WIDTH IS LIMITED A UNIVERSAL “S” SHAPED SWEEPING CURVE IS

SWEEPING CURVES ARE LOST.

GIVEN. DONE BECAUSE OF MORE CLINICAL SIGNIFICANCE BULK OF AMALGAM IS INCREASED. PROXIMAL GROOVES ARE MORE

ACCESSORY GROOVES WERE NOT VERY IMPORTANT OR CRITICAL.

OFTENLY GIVEN SINCE OCCLUSAL WIDTH IS LESS. SO THAT THE STRESSES ARE TRANSMITTED PROPERLY TO PEERIODONTAL LIGAMENT

23


CONVENTIONAL

MODERN CYLINDRICAL BURS ARE USED

CROSS CUT BURS WERE USED WHICH USED TO GIVE ROUGH WALLS.

WHICH GIVES SMOOTHER WALLS, WHICH DECREASED MICROLEAKAGE DUE TO CLOSER ADAPTATION OF RESTORATION MATERIALS. ACCORDING TO MCCLEAN

WIDE AND SHALLOW ISTHMUS

NARROW AND DEEPER ISTHMUS

WAS EMPHASIZED.

WITHSTAND BETTER OCCLUSAL FORCES.

IN CASE OF PM WIDE FLARE WAS GIVEN IN THE PROX. BOX.

FLARE IS NOT GIVEN IN UPPER PM AND BOX IS KEPT PARALLEL FOR ESTHETIC PURPOSE. BEVELS IN GINGIVAL SEATS ARE

NO BEVELS IN GINGIVAL SEAT.

GIVEN ACCORDING TO DIRECTION OF ENAMEL RODS.

BIGGER AND WIDER

SMALLER AND NARROW

RESTORATION LED TO # OF

RESTORATION TRANSMITS THE

RESTORATION OR TOOTH. SO

MAST FORCES TO THE TOOTH

REPLACEMENT WAS

RATHER THAN RESTORATION

NECESSARY.

TAKING THE LOAD ITSELF.

IN SOME CASES GINGIVAL SEAT

GINGIVAL SEAT IS ALWAYS

WAS TAKEN BELOW THE

SUPRA GINGIVAL TO AVOID PDL

GINGIVAL.

DAMAGE. 24


LESS DOVE TAIL.

MORE DOVETAIL. REVERSE CURVE IS GIVEN TO PRESERVE THE MARGINAL

NO REVERSE CURVE.

RIDGE, FOR BULK OF RESTORATION AND FOR BUTJOINT.

WHENEVER ONE PROX PORTION IN THE LOWER MOLAR IS

ALONGWITH PROX PORTION ONLY UPTO CENTRAL PIT OF OCCLUSAL PORTION IS

INVOLVED ENTIRE OCCLUSAL

INVOLVED. RETENTION IS

SURFACE CAVITY WAS

INCREASED BY GIVING MORE

PREPARED.

DOVETAILS.

REFERENCES: 1. Minimal

intervention

Dentistry-FDI

Commision

Project

by

G.J.Mount :Int.Dent.Journal,July 2000 2. Minimal intervention; Early lesions:Quint. Inter.2000 3. Te

Evolution

of

Cavity

Shape

for

Minimal

Amalgam

Restoration;Dental Update,March;1998

25


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