Advances in composite resin copy/ dental implant courses by Indian dental academy

ADVANCES IN COMPOSITE RESIN  

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INTRODUCTION PACKABLE COMPOSITE > INTRODUCTION > HISTORICAL DEVELOPMENT > DESIRABLE CHARACTERISTICS > PRIMM > SOLITAIRE > ALERT > SUREFIL FIBER REINFORCED COMPOSITES > INTODUCTION > LABORATORY BASED PREIMPREGNATED FIBER REINFORCED > TARGIS/VECTRIS > SCULPTURE/FIBERKOR > NON IMPREGNATED FIBER SYSTEMS > BELLE GLASS H P/CONNECT > RIBBOND > GLASS PAN LABORATORY COMPOSITE RESIN FOR INDIRECT RESTORATIONS > FIRST GENERATION > SECOND GENERATION > INTERMEDIATE GENERATION POLYACID MODIFIED RESIN COMPOSITES (COMPOMERS) > INTROUCTION > COMPOSITION > DYRACT > DYRACT AP > F-2000 > SETTING REACTION > CLINICAL PROPERTIES > ADHESION > STRENGTH AND WEAR > FLUORIDE RELEASE > OPTICAL PROPERTIES > HANDLING AND MANIPULATION COMPOSITE INSERTS > COMPOSITION > PROPERTIES > MANIPULATION FLOWABLE COMPOSITE > INTRODUCTION > COMPOSITION > PROPERTIES ORMOCER AND SMART COMPOSITE

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CONCLUSION

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REFERENCES

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INTRODUCTION:

People world wide have become increasingly aware of the potential adverse effects on the environment, of pollution control and of toxic effects of food, drugs and biomaterials.

Amalgam and its potential toxic sid effects (still scienctifically

unproven)continue to be discussed with increasing controversy by the media in some countries. Consequently new direct restorative materials are now being explored by dentists, materials scientists and patients who are searching for the so called “amalgam substitute” or “amalgam alternative”. From a critical point of view some of the new direct restorative materials are good with respect to aesthetics, but all material characteristics must be considered, such as mechanical properties, biological effects, and long term clinical behaviour.

Composite resin materials have become the basic restorative materials of the modern aesthetic-oriented practice. However, the application of composite resin in posteriror teeth remains a challenge as a result of its handling characteristics and chairside stratification.

The kintroduction of new packable. Flowable, ormocer,

restorative maerials and the use of indirect or semi direct techniques utilizing ceromers, fiber reinforced system, labouratory composites etc offer enhanced treatment options.

PACKABLE COMPOSITIES: The search for a direct restorative as an amalgam substitute continues. To date, no substitute have been found, but several alternatives are in clinical use.

One

alternative is the new condensable composites. As the word condensable means that the volume of the material deceasese when pressure is applied a more apporitate term to

describe this group would be ‘packable” as material is compacted not condensed.

Material is stiffer and less sticky than traditional composites.

HISTORICAL DEVELOPEMT: It was as early as 1980s that the first packable composite formulations were designed but the first packable composite to be marketed i.e. Solitare wa introduced in 1997.

Desirable Characteristics for Direct Filling Restorative Materials: 

Nonsticky, wets tooth surfaces, easily transferable and packable.



Moisture tolerant



Should not show much elastic recovery (viscoelasticity)



High critical shear strength (to hold the proximal contact of matrix band)



No access problems for cure (uses bulk cure, chemical cure, or has excellent visible light depth of cure)



Cures rapidly to final hardness but with minimal residual stress



Little or no shrinkage on curing



Easily carved, burnished (smoothened).

The quality of being non sticky is important to facilitate transfer of the material from the packing containers to the prepared cavity. The material also must wet tooth surfaces. To eliminate stickiness, experiments with the first few packable composities in the early 1980’s altered filler characteristics (i.e. filler level, filler shape, filler size or microfiller content). Unfortunately increasing the amount of filler particles lead to the

development of packable compositeis with higher viscosity making the handling of these materials relatively difficult as lead to porosity and insufficient wetting of the particles by the resin matrix and difficult to extrude material through small bore syringes.

While it is important for the composite not to stick to the instrument, it is important for it to stick to the cavity walls. Therefore the manufacturers have eliminated stickiness by slightly altering the filler content, and at the same time reducing the matrix viscosity by using varied matrix monomers (Eg. Polygalss monomer, ethoxylated BisGMA, UDMA ets). This ensured sufficient flow to adapt the composite to the cavity preparation during packing.

The early versions of packable composites were available by admixing PRIMM (Polymeric rigid inorganic matrix material), fused glass fiber powder, with conventional compsities.

Early research showed that levels as low as 5-10% admixed PRIMM

eliminated the tackiness. It produced improvement in mechanical properties only under a few circumstances hence it was not approved as an effective material.

The results from PRIMM experiments demonstrated that small additions of novel fillers would increase the filler surface area, absorb more matrix material and eliminate the stickiness.

The first few packable composite products used fused particle

agglomerates, fibrous filler additions and better filler particle packing arrangements. All of these reduces the viscoelasticity of composites. Since these materials are nonsticky sculpting/carving is most easily accomplished with a burnishing instrument.

Polymeric Rigid Inorganic Matrix Material (JADA Vol.128, 1997,573) The concept provided the basis for fabrication of packable/condensable posterior composite resin. This consists of a resin and a ceramic component. The fibers which are composed of alumina and silicon dioxide are superficially fused together at selected sites; which generates a continuous network with small chambers/cavities in between.

Afer

silanating

these

particles

the

manufacturer

infiltrates

the

space

with

BisGMA/UDMA resin.

Handling Characteristics: The composite mass is inserted just like an amalgam. Alumina fibers might scratch the nozzle of the amalgam carrier. So it should be made with wear resistant polymer. The injected increment is condensed in a conventional light curing unit due to light conducting properties of the individual ceramic fibers.

The PRIMM network is infiltrated with the resin component. The resin tries to shrink away from the fibers during polymerization but as the fibers are silanated the polymerizing resin does not pull away from the surface.

There have been a wide range of packable composites introduced in the past 2 years: 1.

Solitaire

2.

Alert

3.

surefil

4.

Filtek P60

5.

Prodigy condensable

6.

Pyramid

7.

Glacier

8.

Synergy compact

9.

Definite

SOLITAIRE: It is the first packable composite introduced in late 1997. It consist of crushed barium aluminosilicate glass surfaced with small particles of a similar composition.

These particles are bonded at elevated temperature creating large particles with coarse texture.

The matrix monomer used here was polyglass monomer/multifunctional methacrylic acid ester resin. It shows a wear of 6-8 um annually. The unique geometry of the filler component creates an unset composite with packable behaviour. This is because of the friction caused by the sliding of one particle against another. The porous character also allows matrix resin to interlock with the particles.

Greater the forces applied during condensation better is the packing ability.

So

the clinician should use a large condense which conveniently fit within the confines.

This is an acronym for amalgam like esthetic restorative treatment. Its packable consistency results from the incorporation of chopped microglass fiber, in addition to the

standard hybrid composite fillers. Individual fibers are less than 6 um in diameter and greater that 20 um in length.

The hybrid filler is crushed barium boroalumino silicate

glass and colloidal silica. The hybrid filler is crushed barium boroalumino silicate glass and colloidal silica. The overall combination produces a consistency similar to triturated amalgam. These are available in packets and carried with an amalgam carrier and inserted into the cavity. Carriers are coated with plastic/polymer else scratching of the normal carrier may impart gray color to the composite. After injection the condensation is done in a similar way as amalgam. This is one packable composite for which the manufacturer recommends bulk curing, upto a thickness of 5 mm. (J Dent Res 75 (3) : 1998).

The monomer used in this is dimethacrylate

of ethoxylated Bisphenol A

polycarbonate resin.

SUREFIL: This possesses excellent handling characteristics that are attributed to the high packing efficency of the compsite filler particles. Contains a urethane modified bisGMA resin. It contains 3 different sized fillers (Midifiller, Minifiller and Microfiller). This perlmits a high packing density. As a result of this it exhibits good pacing behaiour and amalgam like properties. Has got good clinical wear. It helps in establishing tight proximal contacts. The particles in this are made of a patented fluoride infused glass (barium borofluro aluminosilicate glass and silica). It can also be cured in bulk(5mm).

PROPERTIES: (J OF Esthetic and Restorative Dentistry. Vol.13, No.1, 2001) (J Esthetic Dentistry.

Vol.12,No.4,2000).

Various studies have shown that packable composities have similar properties to posterior composites.

Various studies have shown that packable composites have similar properties to posterior composities.

Fracture Touchness: Alert

: 1.6 – 1.8 MP am ½

Surefil

: 1.25 – 1.45 MP a m ½

Solitaire

: 0.65 – 0.75 MP a m ½

Fracture toughness of a composite has been correlated with its filler volume fraction. As filler volume increases fracture toughness increases. So as filler volume of packables is in same range as that of Z100 mand Heliomolar (Post. Composites). So do not have significantly different fracture toghness except Alert. It is filled with glass fibers, glass fibers have a significant toughening effect, robable by enhancing crack blunting or by providing sites for energy dissipation during crack propagation through delamination. SEM shows rough fracture surface with signs of matrix – filler debonding

and crack deflection from its primary path. Other composites have relatively smoother fracture surfaces.

Flexure Strenght: packable composites have values similar to Heliomolar, the microfill composite, than to Z-100 the minifill. Solitaire having the lowest value (50-70 MPa).

There is not a significant correlation between flexure strength and filler volumes (R2 = .

327).

Flexure Modulus : Packable composites have flexure modulus similar to the nonpackable posterior composities with solitaire having lowest value.

Hardness : the hadness values for the packable compsities are also within the range of the nonpacable material.

Solitaire has lowest hardness value.

In case of solitaire low

hardness and modulus may be because of the matrix resin, multifunctional melthacrylate ester instead of traditional dimethacrylates. Cross linked network produced from this monomer likely includes many unreacted pandent methacry lates that serve as plasticizers and

reduces

the

properties

or

it

may

be

because

of

porous

fillers.

Depth of Cure : the depth of cure of packable is similar to thalt of other posterior compoites.

The increments should not be more than

2 mm to ensure adequate

conversion throughout the restoration, light cured for 40 s with a source of 18\080 m W/Cm2.

Polymerization shrinkage : similar to or greater that that of non packable material solitaires highest value extending 3 %.

Radiopacity : all packable composites, except solitaire have radiopacity exceeding 2 mm of aluminimum. Solitaire may be due to low volume of radiopaque filler and chemical composition of the fillers.

Inorganic filler content : two distinct and rela;tively narrow distributions volume.

Low group 48 % (approximately) Pyramid enamel, solitaire High Group 60 % alert, Pyramid Dentin, surefill

The major advantage/benefit of these new composites is their thicker consistency, which may be deemed helpful in achieving tight interproximal contacts.

COMPOMERS (Polyacid – Modified Resin Composites): Compomer is resin-ionomer hybrid restorative material marketed as multipurpose material, as resin that may release fluoride but have only limited glass ionomer properties. (It contains the major ingredients of both composites (resin component) and glass ionomer cements (polyalkenoate acid and glass fillers component) except for water.

They have a limited dual setting mechanism, dominant setting reaction is the resinous photopolymerisation and no acid base reaction can occur until the material absorbs water.

COMPOSITION : The compomers presently available contain atleast two different resins for the matrix and the glass particles as fillers common to composite resins and glass ionomers.

The resin component contains functional groups of polycarboxylic acid and melthacrylate combined in one molecule. This provides methacrylic groups for cross linking (as in composite resins) and carboxly groups for cross linking (as in composite resins) and carboxyl groups to undergo an acid-base reaction in the presence of water and metal ions (as glass ionomers).

Fluoride containing glasses, typical of glass ionomers comprise the principal fillers to which may be added glass particles similar to those in composite resins. There may also be other fillers providing additional fluoride release and radiopacity.

Dyract: Characterized by a unique single component component restorative and a newly developed primer/adhesive liqueid for enhanced adhesion to tooth tissues and improved seal of the cavity.

Matrix:

(1) UDMA (Urethane dimethacrylate) monomer (2) TCB resing consists

of a new monomer of dula functionality, made up of a butane tetracarboxylic acid backbone with a polymerizable HEMA (Hydroxyethylmethacrylate) side chain.

It contains two methacrylate groups and two carboxyl groups. The former forms cross like with other methacrylate terminated resins when initiated through radical

polymerization while the later group can undergo acid base reaction to form a salt with metal ions and water.

Fillers: Contains solely glass ionomer fillers (Calcium fluoroaluminosilicate glass).

Finely milled glass with mean particle size of 2.5 pm accounts for 72% by wt. of the composition with 13 % of fluoride.

Premier/Adhesive Consists of Three Resins: PENTS,

a patented dipentaerythritol pentacrylate phosphoric acid, which

contains an acidic monomer made up of phosphoric acid with a polymerizable methacrylate group attached and is responsible for the formation of ionic bonds to the inorganic part of the tooth.

TEGDMA and an elastomeric resin to increase the cross linkage among the different monomers and elasticity of the cured primer/adhesive.

Acetone – Solvent (Carries the resins, wet the tooth surface and assists the penetration of the resin in the dentin surface).

Dyract AP: Ingredients are basically similar to the original Dyract. The organic matrix has been modified by adding a small amount of a highly cross linking monomer which brings an enormous increase in hardness and strength of the matrix almost equal to that of hybrid resin composite.

Filler : strontium fluoro silicate glass of mean particle size reduced to 0.8 pm from 1.5 pm and a loading of about 73% by mass.

Adhesive used is Prime and Bond 2.1 Similar to Dyract PSA, in addition cetylamine hydrofluoride to deliver an additional amount of fluoride to teeth.

It has an increased ability to absorb the stresses caused by chewing and temperature fluctuations.

F-2000: Resin matrix is comprised of three monomers: 1. The dimethacrylate functional oligomer (CDMA Oligomer) derived from citric acid.

2. Glyceryl dimethacrylate (GDMA) also called hydroxypropylene dimethacrylate.

3. High molecular mass hydrophilic polymer.

CDMA oligomer has a greater ratio of methacrylate group to carboxyl groups which allows greater cross linking of the resin matrix.

GDMA is chemically, functionally similar to HEMA with a hydrophilic hydroxyl group which acts as a diluent for the CDMA and copolymerizes with the oligomer.

The high molecular mass hydrophilic polymer rapidly takes up a controlled amount of fluid from the oral cavity which facilitates the transport of fluorides. Due to its large size and flexibility, acts as a modifier that account for clinical handling characteristics.

Fillers: Fluoro-aluminosilicate glass with average particle size of about 3 pm and a maximum of about 10 pm. Small amount of colloical silica with a loading of 84 % by mass.

F-2000 COMPOMER Primer/adhesive are hydrophilic in nature. Contain resin monomer (HEMA), methacrylate modified polyacrylic acid and maleic acid in an aqueous solution of water. They are less volatile and highly suitable for use on moist dentin surfaces.

Compoglass: Fillers are a combination of methacrylate monomers and conventional glass ionomer fillers with a mean particle size of 1.5 pm, which produces an additional stability to the cross linkage, with improvements in physical properties.

Resin matrix : Propoxylated

BISGMA,

urethane

dimethacrylate,

dimethacrylate, cycloaliphatic dicarboxylic acid dimethacrylate.

tetraethylene

glycol

Silanized spherical

mixed oxide, Ytterbium trifluoride.

Adhesive used is Syntact Signle component and are hydrophilic in nature.

Chemistry of Setting Reaction: There is a dominant light initiated free radical polymerization followed by a later acid-base reaction. The setting reaction occurs in two stages:

Stage 1 reaction is typical of light activated composite resins, forming a resin network enclosing the filler particles. The light curing mechanism leads to hardening of the material in the cavity.

Stage 2 reaction occurs lowly after placement in the cavity. Water sorption will occur for up to 2-3 months and in the presence of carboxyl groups from the polyacid and metal ion from the ionomer glass, there will be a relatively slow ionic acid base reaction.

Hydrogels will form within the resin structure and there will be a slow and low level release of fluorides.

CLINICAL PROPERTIES: Adhesion : In Dyract AP restorative system there are two mechanisms for adhesive bonds to the cavity wall.

First: Self adhesive property of the material. 50% of the reactive units of the patented TCB monomer consists of hydrophilic carboxyl (-COOH) groups.

Such

polyelectrolytes can bond to both enamel and dentine. The functional carboxyl groups can form ionic bonds with the calcium ions of the tooth surface. Some secondary valence bonding like hydrogen bonding may occur as well.

Second mechanism is adhesion to the tooth surface through primer/adhesive system. The hydrophilic phosphate group of the PENTA resin in the adhesive will form ionic bonds with the calcium ions of the hydroxyapatite.

In addition, when light cured, the three resins in the adhesive will undergo free radical addition polymerization. The cross linked resin form a REINFORCED ZONE, similar to the hybrid zone, of the surface dentin, and make both the enamel and dentin compatible for the actual restoration.

It has been noticed hat if adhesive is not applied before restorative material, the adhesion to enamel and dentin will be reduced by a factor 2 and 4 respectively.

Adhesion to enamel is enhanced with the use of acid etching technique using 10% or 35% phosphoric acid prior to the placement of the primer/adhesive.

Strength and Wear Performance: In order to withstand high chewing forces in the oral cavity, a filling material intended for long term use needs to have high compressive and flexural strength.

Dyract has got more initial and long term compressive strength, dimetral tensile strength and transverse strength that conventional and resin modified glass ionomers.

GIC – 140 MPa, composite- 300 MPa, compomer 200 – 250 MPa Dyract AP

has values almost equal to that of the hybrid resin composite,

spectrum TPH, and higher than original Dyract.

Dyract showed total substance loss after 5 years of laboratory study of 200-250 pm, about twice the amount recorded for Prisma APH, a posterior resin composite.

Dyract AP and Hytac Aplitip showed a wear value similar to that of composites, may be due to introduction of smaller, submicrometre filler in newer compomers. In one clinical study, the wear value of Dyract was 43.3 pm in six months and 72.7 pm in 12 months which is about 3 times the wear rate of a hybrid composite, Prisma TPH. After 24 months wear values of Dyract and TPH were 113 pm and 63.9 pm respectively.

Fluoride Release : Dyract shows fluoride release for more that 12 months and maintains the same rate of diffusion. Fluoride uptake by adjacent enamel in contact is shown to be 20 pm.

Thus producing anticariogenic properties.

Like glass ionomer cement it acts as a fluoride reservoir and absorbs fluoride when exposed to fluoride ion sources, like fluoridated dentirifices which is slowly release into the surroundings after the ion source is removed.

Compoglass F has 50% more fluoride release than is original compolgass,due to finer particle size of the fluoride glass and incorporation of additional fluoride in some of the Primer/adhesive systems.

It is shown that more fluoride in some of the

Premier/adhesive systems. It is shown that more fluoride is released in acidic solution (pH3 – 4.5).

Optical Properties: The esthetic qualities of a material are determined by its colour and opacity. Dyract AP is available in a range of twelve different shades which follows the vita shade guide. F 2000 and compoglass F compomers have speciality shades for primary teeth.

Dyract AP has radiopacity of 5 which is 2.5 times to that of dentin (2) and slightly higher than enamel (3.5). This value is desirable for radiographic detection of recurrent caries and offers an easy method for documentation of dental work.

HANDLING AND MANIPULATION: Easy to manipulate, supplied in capsules which require no mixing. The gun is used for easy dispensing directly to cavities and surfaces. The consistency makes it easy to apply and contour without stickiness thus less time is required for final finishing.

Like other light curing materials, polymerization shrinkage is a problem. It has got polymerization shrinkage similar to hybrid resin composites.

So incremental

placement is advised. For Dyract AP 3 mm or less, 2 mm or less for newer compomers and then each to be cured for atleast 40 seconds.

Finishing can be done immediately after curing using fluted tungsten carbide finishing burs or polishing discs.

LABORATORY COMPOSITE RESINS FOR INDIRECT RESTORATIONS: In the early 1980s, Mormann and Touati and Colleagues pioneered the use of composite resins for the fabrication of indirect inlays and onlays.

In the mid 1980s, Touati and Pissis developed he concept of metal composite inlays and bridges after these silicating technique, which enabled a strong bond between polymer and metal, because of a very thin (0.1 mm) aluminium oxide layer.

First Generation Laboratory Composite Resins: They are microfilled composite resins, with 66% resin content and 33% inorganic particles. Particle size of 0.04 – 0.4 um. Inorganic fillers are round in shape and consist of colloidal silica.

Flexural strength: 60 80 MPa Modulus of elasticity: 2000 – 3500 MPa

Low wear resistance (owing to a low percentage of inorganic filler particles and a high percentage of exposed resin).

High polymerization shrinkage (polymerization is by light, heat and pressure or argon laser).

First generation laboratory composites remain somewhat fragile and subject to chipping and color variation.

The lower the percentage of inorganic particles, the lower the mechanical properties of the composites.

Resulting in failure of first generation laboratory

composites. Used for inlays, onlays and laminates, implant supported prosthesis.

Second generation laboratory composite resins.: They are suitable alternatives to ceramics in some clinical situations.

Second Generation are microhybrid composite resin (sometimes called ceramic polymers) with a high density of ceramic filler particles.

Consists of inorganic filler content of 66% by volume filler content differs from that of First generation in form )longer, whereas the first generation are round), size (bigger 1-5 um) and composition (mainly silica and barium glasses and ceramics).

Resin matrix : 33% *

Flxural strength

: 120 -150 MPa

*

Elastic modulus

: 8000 – 12000 MPa

*

Minimal polymerization shrinkage

*

A bond to metal substructure of crowns and bridges, regardless of alloy used.

*

Resistance to abrasion similar to that of enamel.

Usefull in several clinical applications: ďƒ¨

Inlays and onlays

ďƒ¨

Laminated veneers and jacket crowns



Implant supported restorations (for progressive loading of implant supported prostheses).



For easier repair directly in the mouth



For modification and/or adjustment of proximal contacts.



For reduction of occlusal stresses in bruxism cases (as composite resins, absorb some strains because of their elasticity).

They provide good esthetics, with a wide range of Hue, Chroma, and Opacity, Biocompatibility and tissue preservation.

Most second generation composite resins require post curing process. 

Heat and light (phototherimic treatment) eg. Targis and conquest.



Heat and nitrogen pressure (eg.Belleglass HP)

This procedure allows the optimal conversion rate to be reached within a few minutes (10 for Belleglass HP and 25 for Targis).

Intermediate Laboratory Composite Resins: They are also microhybrid light cured composites. They cannot be classified as second generation composites because they do not feature all the required characteristics, like ; 

High mechanical properties



High percentage in volume of inorganic micro particles



Bond to metal

Used for inlays, onlays and laminate veneers.

Metal-resin bonding can be mechanical or chemical.

Mechanical: Macromechanical retention (beaded metal, metal mesh, pitted metal).

Micromechanical retention (sandblasting or etching).

Chemical: Intermediate interface such as tin plating or ceramic coating, is fused to the metal surface.

Eg.Silicoating, Rocatec, Adhesive Silicoating.

COMPOSITE INSERTS: Preformed shapes and sizes of glass ceramic whose survaces have been silane treated. They are available in different shapes L, T, round, conical, cylindrical size 0.5 -2 (megafillers).

Application: Used to minimize the marginal contraction gaps in composite fillings.

Properties: 

Low coefficient of thermal expansion



Wear resistant



Their presence reduces polymerization shrinkage by upto 75% and inceases the stiffness of the filling.



Radiopaque

Manipulation : these inserts are pressed into a cavity preparation that is already filled with unpolymerized composite. The composite which is extruded during the insertion is removed and that which remains is cured. The restoration is then contoured using diamond rotary instruments and polished. Cavity is prepared > This Layer of composite is placed > above this glass fillers are placed > rest of the cavity is filled with composite resin > contouring done > cured > finishing and polishing.

SMART COMPOSITES: This class of composite was introduced as the product Ariston in 1998. Ariston is an ion releasing composite material. It releases functional ions like fluoride, hydroxyl, and calcium ions as the pH drops in the area immediately adjacent to the restorative materials, as a result of active plaque.

Smart composites work is based on the newly developed alkaline glass. The pase contain Ba, A1, and F silicate glass filler (1 um) with Ytterbium trifluride, silicon dioxide and alkaline glass (1.6 um) in dimethacrylate monomers.

Filler Content: 80% by weight and 60% by volume. Dentin should be sealed to reduce sensitivity. It reduces secondary caries formation at the margin of a restoration by inhibiting bacterial growth.

This result in reduced demineralization and a buffering of

the acid produced by caries forming microorganisms.

Fluoride released is lower than glass ionomers but more than that of compomers.

Flexural strength

: 118 MPa

Flexural modulus

: 7.3 Gpa

Fracture toughness : : 1.9 MNm -3/2 Mean war rate

: 7194 um

ORMOCERS: O ll H3C-C-C-O l ll CH2 O O OR ll ll H3C-C-C-O________________________O-C-N____________Si -OR ll ll CH2 H OR O Ll H3C-C----C-O ll ll CH2

Ormocer is the acronym for “organically modified ceramics”.

This class of

material represents a novel inorganic organic copolymers in the formulation that allows for modification of its mechanical parameters.

The inorganic – organic copolymer are synthesized from multifunctional urethanes and thioether (meth) acrylate alkoxysilanes as sol gel precursors. Alkoxysilyl groups of the silane permit the formation of an inorganic Is-O-Is network by hydrolysis and poly-condensation reactions.

The methacrylate groups are available for

photochemical polymerization. The filler particles are 1-1.5 pm in size and the material contains 77 % filler by weight and 61% by volume.

The essential difference between definite and the previously available composites is found in the matrix. The matrix of conventional composites mainly consists low molecular monomer components, mainly bis-GAM. On light activation only 60-70% of

the free monomers can be converted. Throughout the lifetime of the restoration they can be eluted.

Silicon oxide, a filler, serves as a basic substance for the ormocer. It is modified originally by adding polymerisable side chains in the form of methacrylate groups.

Through bonding of the methacrylate molecules to the carrier medium, the methacrylate molecules can no longer be eluted during incomplete polymerization.

Definite permanently releases fluoride, calcium and phosphate ions that protect the adjoining cavity margins.

Biocompatible Physical properties as given by Wolter are Bending strength (3 point bending test) : 100 – 160 MPa Modulus of elasticity

: 10 – 17 Gpa

Coefficient of thermal expansion

: 17 – 25 x 10-6K.1

Water uptake

: < 1.2%

Solubility in water

: Not detectable

Shrinkage

: 1.7 – 2.5 vol%

FLOWABLE COMPOSITES: Flowable composites were introduced in late 1996. They are broadly similar to rein cements and pit and fissure sealants, with filler loading and particle size less than hybrid composites, resulting in a material of low viscosity. Filler content is generally less

than 50% by volume, so polymerization shrinkage will be greater than for more heavily filled materials. The modulus of elasticity will also be lower than for conventional resin composite materials. This may allow the material to flex and flow under the conditions thought to occur in Class V cavities and the flow of the material may also be useful in absorbing stresses caused by polymerization shrinkage.

Flowabel composites are

available in a range of shades, some versions even include pink for use in masking areas of gingival recession (Pink revolution). A number of formulations contain fluoride, although the clinical benefit of this is not quantified. Claimed advantages of flowable materials are that they are fast and easy, that excellent access and placement can be achieved using the syringe tips in which they are supplied. Flowables should not be used in situation involving high stresses or associated with war.

Wear Resistance: Wear resistance depends on ď&#x192;¨

Inter particle spacing, called the protection hypothesis

ď&#x192;¨

Extent of the filler particle density

Interparticle spacing is reduced with small filler particles such as microfillers, eventhough the percentage of filler by volume may be only 30-50% i.e. why microfilled composites shows good wear resistance and as most of the flowables are based on minifillers (1.0 to 0.1 um size) or microfillers (0.02 to o.04 um).

Aeliteflo 17.2 +- 2.6 um Amalgam 3.4 +- Traditional composite 7.4 +- 3.5 um

Compressive Strength (MPa)

Diametric (MPa) Tensile St.

Vol %

Filler/Size

Aelite flow

43

Ba glass, Coloidal Silica 0.7 um

201

34

Flow Restore

48

Silica barium glass, ba Flourosilicate0.7 pm

209

35

Revolution

41

Ba Glass, Synthetic Silica, 1 um

196

33

Ultraseal XT Plus

37

Glass Ionomer Glasses 1-1 .5 um

161

16

Flowable materials were developed principally to provide their own particular handling characteristics, rather than with any particular physical or clinical performance property in mind and as a result, there is little known about their performance. In one study flowables are compared with hybrid composites with respect to physical properties.

Uses : 1) Can be used as filling material in low stress applications but not in Class I and II in premolars and molars.

2) Resurfacing composite or GI restorations or for rebuilding worn composite contact areas.

3) In areas of difficult access or areas that require greater penetration. Amalgam, composite or crown margin repairs, pit and fissure sealant or preventive resin restoration.

4) As liner or base in Class II proximal box.

5) For veneers or for cementing porcelain veneers.

6) Restoration of air abrasion preparation, Class V lesions, porcelain repairs, enamel defects, incisal edge repair in anteriors, Class III lesions.

FIBER REINFORCED COMPOSITE RESIN SYSTEMS: The use of fibers to improve the mechanical properties of resin based materials has been known for many years. Although the mechanical properties of these materials allow tham to withstand high stress, they lack critical requirements like esthetics as many are black (carbon fibers) or are somewhat opaque glass and resin fibers and ease of fabrication into numerous nonstandard shapes.

Early dental applications often failed due to low fiber content (10% compared to todays 40-70% and poor bonding between the fiber and resin matrix.

Revolution came into dental market with the introduction of Targis-Vectris system. Other are sculpture/fibrekor , Belleglass/Connect, Belleglass/Vectris, etc.

They are also called Ceromer (Ceramic Optimised Polymer), Polyglass and polymer ceramic, as manufacturers try to convince dentists that these materials somehow were closer to

ceramics than to composite resins. As ceramics are seen as stable

materials whereas composites often have been viewed as high wear, color unstable materials. (fiber reinforced materials may be good esthetic option in cases where there are virgin teeth adjoining a pontic space, where no metal is desired, in low stress areas and for implant supported prostheses.

Conventional composite resins consist of micron and submicron glass or ceramic particles â&#x20AC;?floatingâ&#x20AC;? in a resin matrix. They are discrete particles, not connected to each other. In fiber reinforced materials long continuous fibers, about 10 u in diameter are

used to provide the bulk of the mechanical properties to the resin material. It resist stress better in multiple directions while maintaining flexibility, so does not become brittle like ceramics.

The type of fiber reinforcement is also important – it may be parallel fibers, fiber weaves or braided fibers. If the fibers are unidirectional, then their resistance to load is different in different direction. Whereas braided fibers are designed to better resist stresses placed on the material in multiple directions. Fiber reinforced composite resins can be classified broadly as resin preimpregnated or unimpregnated and may be primarily laboratory or chairside based.

LABORATORY BASED, PREIMPREGNATED FIBER REINFORCED SYSTEMS:

Targis/Vectris Introduced in U.S. in 1996.

Consist of two major components Targis composite resin forms the bulk of the restoration vectris fiber framework. Various types of fibers: 

Parallel glass fibers in resin matrix for pontics

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Woven fibers for single crowns and abutments

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A separate weave for covering and joining the abutments to the pontic.

Flexural strength values For vectris pontic : 860 MPa For vectirs weaves : 430-500 MPa

Elastic modulus : 30-40 gPa, much better than conventional composite resins (8-10 gPa0 at resisting stress deformation but not as good as porcelain (60 gPa).

Targis dentin and enamel layers Strength : 147-160 MPa Elastic modulus : 10 gPa Targis base : Less resistant to stress deformation, with low elastic modulus 5gPa.

Crucial links in the system is the bonding of the Targis to the vectris. If the bonding interaction is weak, then delamination may occur when bridge or crown is stressed.

Weak bonding may be due to: ď&#x192;¨

Targis base as it has low elastic modulus

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If layer of Targis are not thoroughly cured and carefully bonded to each other.

Steps in Fabrication: Fiber reinforced network is light cured in vacuum under pressure, to adapt the material to the abutments and pontic, reduce porosity and improve the cure of the resin materials. After the framework is formed, a bonding agent and first layer of Targis (Targis Base) is applied. Subsequent layers of dentin and then enamel Targis composite resin are placed to form the final contours of the restoration. The entire completed restoration undergoes a final cure using heat and light.

Advantages: 1.

Good esthetics, restorations have good translucency and provides an esthetic match.

2.

Good choice for use in situations where high stress precludes the use of a ceramic material or where the patient insists on using no metal in the mouth.

3.

Requires less surface area on abutment teeth when compared to metal or ceramic as it has ability to bond to the tooth structure.

4.

Act as shock absorber when used in implant supported restorations as it transfers less stress to the bone.

5.

Does not abrade the opposing enamel.

Questions remain with respect to color stability, wear, and delamination problems, as will as sensitivity possibly due to dimensional changes in the material because of a high coefficient of thermal expansion.

Sculpture/ Fibrek or: This system also involves veneering a composite resin (Sculpture) to a resin preimpregnated glass fiver network. Fibrekor fibers available in 15 cm lengths of various widths. Sculpture is polycarbonate based composite resin.

Steps: Sculpture resin is applied to the abutments and cured. Notch is created for placement of the initial piece of fibers for the pontic, additional fiber material is then wrapped around abutments pontic area and cut to the proper length to reinforce the

abutments and pontic area and cut to the proper length to reinforce the abutments and pontic area and cut to the proper length to reinforce the abutments and pontic aea.

The sculpture composite resin is then layered on the fiver netweok using dentin and enamel shades and light cured in a pressurized inert atmosphere (nitrogen). Final cure is achieved in a vacuum using heat.

Fiber frame has strength values of 500 MPa. Good esthetics and customization of the restoration can be accomplished using various stains.

Degree of cure for sculpture is higher than that of Targis due to the pressurized nitrogen atmosphere used for curing.

This eliminates the chance for oxygen

inhibition of curing which improves the surface and overall degree of polymerization, making it more wear resistant.

Less chances of debonding from fiber framework and within the sculpture layers because of fabrication and curing technique.

NON-PREIMPREGNATED FIBER SYSTEMS: Belle Glass HP/Connect : Belleglass is a submicron filled resin used to fiabricate inlays, onlays, crowns, and abutments for fixed partial dentures.

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Available in variety of dentin and enamel shades.

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Cured like sculpture, ie light and heat are applied enclosed in a pressurized chamber filled with nitrogen.

A multiple unit bridge is fabricated by connecting the abutments with a braided polyethylene polymer fiber called connect. Resin is flowed into the fiber weave and cured onto the abutments. Pontic is fabricated by layering belle Glass onto the fibers.

Entire restoration is cured in the pressurized nitrogen chamber. Flexural strength of belle is 147 MPa )approximately). Strength of the resin infiltrated connect fibers range from 220-340 MPa. Elastic modulus : 8-10 gPa. Wear rate equivalent to enamel wear rates.

Overall mechanical properties of connect system are significantly less than Vectris and Fiberkor systems so less long term success of fixed partial dentures.

RIBBOND: It is a cross linked leno stitch weave of polyethylene fibers. Can be used chairside or in laboratory to fabricate composite resin bridges like belle Glass Connect System.

Resin is applied by hand to impregnate the weave resulting in a flexural strength of approximately 200-275 MPa, with elastic modulus of 8 gPa.

Used Primarily as:

1. Periodontal splinting material 2. Reinforcement and repair of provisional restorations 3. Complete/Partial removable dentures.

4. Endodontic posts/cores 5. Orthodontic appliances

Disadvantages: because of low modulus of elasticity unlikely to have long term success for use in fixed partial dentures.

Glass Span: It is a braided glass fiber used to fabricate fiber reinforced crowns and bridges. ď&#x192;¨

used in dental laboratory or chairside

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Low viscosity resin is applied to the fibers and then cured.

Flexural strength : 266-321 MPa Elastic modulus : 14 gPa SUMMARY: The Targis/Vectris and Sculpture/Fiberkor systems were devised to create a translucent maximally reinforced resin framework for fabrication of crowns, bridges, inlays and onlays. These restorations rely on proper bonding to the remaining tooth structure.

Cementation procedures should involve silane treatment of the cleaned abraded internal restoration surface, application of bonding agent to the restoration as will as the etched/primed tooth, and finally use of a composite resin.

Polishing done with diamond or alumina impregnated rubber wheels followed by diamond paste.

The glass fibers can pose a health risk as they are small enoght to be inhaled and deposited in the lungs, resulting in a silicosis type problem. Therefore, if fibers are exposed and ground on, it is important to war a mask. Secondly fibers can be a skin irritant, so gloves should be worn.

If fibers become exposed intraorally they can cause gingival inflammation and may attract plaque. The fibers should be covered with additional composite or restoration should be replaced.

The bulk of these restorations are formed using a particulate filled resin, similar in structure to conventional composite resins. Therefore, concerns as to wear resistance, color stability, excessive expansion/contraction and sensitivity remain until these materials are proven in long term clinical trials.

The fibers used for this purpose are composed of carbon Kevlar, Polyethylne and glass fiber.

Mechanical Properties and War Behaviour of Light Cured packabel Composite Resins: (Dent Mat. 16 (2000) : 33-40

Conducted to determine flexural strength., flexural modulus, fracture toughness and wear resistance of three packable composites (solitaire, Surefil, Alert) and apackable Ormocer (Definite) in comparison with an advanced hybrid composite (Tetric Ceram) and an ion releasing composite (Ariston pHc).

Results : Alert exhibited the highest flexural modulus and fracture toughness, but the lowest wear resistance solitaire presented the highest wear resistance but lower mechanical properties than all other materials. Surefil revealed a significantly higher flexlural modulus and wear resistance than tetric ceram and Ariston PHc. Definite has mechanical properties similar to tetric ceram and Ariston PHc but less wear.

Alert and Solitaire exhibited highest wears as a result of high filler load, leavels.

Although solitaire contains high filler fraction volume of 50 % (66 wt%) it is comprised of porous SiO2 filler (30%) with a particle size of 3-22 um, Ba Al-B-Si glass (5 wt%).

So may be due to air porosities included in the composite materials.

Filler load level and filler matrix interactions have a greater influence on fracture parameter that the structure of the organic matrix.

Composites with smaller filler particles and high filler fraction volumes are suggested to wear less. Surefil is based on an interlocking filler technology (82 wt%) bonded to an urethane modified Bis-GMA resin matrix, which can strongly resist

exfoliation dislodgment Bis-GMA resin matrix, which can strongly resist exfoliation dislodgment through abrasion.

The matrix of the ormocer definite is characterized by an interpenetrating network of inorganic organic copolymers.

Solitaire contains 30 wt% of a porous SiO2 filler which integrates part of the resin matrix within the porosities of the bodies of the filler particles resulting in firm bond of the filler particles to the matrix resisting wear better.

Alert contains micro-filamentous glass fiber particles which are 60-80 pm in length and 6 pm in diameter. Large sized rod shaped particles most likely are responsible for the high abrasion wear.

Ariston has high wear rates than tetric because of larger average filler size and contains a relatively hydrophilic monomer in its organic matrix. Interactions between the matrix and the ion releasing alkaline glass filler are probably different from tetric ceram.

CONCLUSION: The area of tooth colored adhesive dentisty is advancing at an exponential rate, and it is essential that all parctioners pay constant attention to the information about all materials as they appear on the market. Coupled with a through knowledge of treatment planning and case design., results make restorative practice a rewarding experience for

clinicians and patients.

Interest in the scientific background, development and

performance of restorative materials must be at a high to avoid being snared by advertising promises.