Composite

composite resin and its application in dentistry

1. COMPOSITE RESIN BY DR IPSITA PATHAK JR II

2. CONTENTS Introduction Definition Classification Composition Advantages & disadvantages Types of composite Steps of clinical procedure Tooth preparation procedure Techniques Light curing units Failure of composite

3. INTRODUCTION Mercury-containing dental amalgam restorations are being replaced with dental composites as the restorative materials of choice mainly because of the inherent esthetic appeal of the latter and the long-standing controversy related to the toxicity of the former.

4. Composites are used because overall properties of the composites are superior to those of the individual components. The fact that dental composite materials continue to improve in strength, abrasion resistance, ease of application, translucency and polishability rapidly increased their use in the first decade after being introduced and continues to increase their popularity.

5. DEFINITION According to Philip’s composite can be defined as a compound of two or more distinctly different materials with properties that are superior or intermediate to those of individual constituents. According to S kinner’s A highly cross linked polymeric material reinforced by a dispersion of amorphous silica, glass crystalline or organic resin filler particles and or short fibers bonded to the matrix by a coupling agent.

6. CLASSIFICATION Composite can be classified based on the filler size , percentage of fillers loading, type of resin matrix, viscosity, methods of polymerization and uses .

7. On the basis of the mean particle size of major fillers (skinner’s) A) Traditional /Conventional / Macrofilled Composites:- 8-12 µm B) Small Particle Filled Size- 1-5µm C) Microfilled Composites - 0.01- 0.04 µm D) Hybrid Composites- 0.6 – 1.0 µm

8. On the basis of filler particle size and distribution ( Bayne & Heymen classification) a) megafilled composites -(1-2µm) b) macrofilled composites-( 10-100µm) c) midifilled composites-(1-10µm) d) minifilled composites- ( 0.1-1µ m) e) microfilled composites- ( 0.01- 0.1µm) f) nanofilled composites-( 0.001-0.01µm)

9. On the basis of viscosity(Summit) A)conventional B) Packable C) Flowable

10. ON THE BASIS OF THE METHOD OF POLYMERIZATION A) Selfcure / Autocure / Chemical cure B) Light cure 1. Uv light 2. Visible light cure C) Dual cure – combine of both self cure & light cure D) Staged-curing composites-initial soft start polymerization followed by complete polymerization.

11. BASED ON THE MODE OF PRESENTATION 1.Two paste system 2.Single paste system 3.Powder-liquid system

12. ON THE BASIS OF THEIR CHRONOLOGICAL DEVELOPMENT(MARZOUK) A) first generation : consist of macro-ceramic reinforcing phases in resin matrix B) second generation : consist of colloidal and micro-ceramic phases in continuous resin phase C) third generation : consist of hybrid composite , having combination of macro and micro ceramic reinforces in a suitable continuous resin phase

13. D) fourth generation : consists of hybrid composites having heat cured, irregularly shaped, highly reinforced , composite macro particles with a reinforcing phase of microceramics E) fifth generation : consist of hybrid composites , having continuous resin phase reinforced by microceramics and macro , spherical , highly reinforced , heat cured composites particles.

14. F) sixth generation : consist of hybrid composites , having continuous resin phase reinforced with a combination of micro-ceramics and agglomerates of sintered micro ceramics.

15. INDICATION Class I II III IV V VI Core build ups sealants and preventive resin restorations Esthetic enhancement procedure Temporary restorations Periodontal splinting Orthodontic bonding Patients allergic to metal Composite inlays

16. CONTRAINDICATION Isolation difficulties Teeth with heavy or abnormal occlusal stress Subgingival area High caries index Habits( bruxism ) If patients allergic to composite

17. ADVANTAGES Esthetics Conservation and less complex Used almost universally Bonded to tooth structure Repairable No corrosion No health hazards

18. DISADVANTAGES Polymerization shrinkage Technique sensitive Higher coefficient of thermal expansion Time consuming Staining Increased occlusal wear Low modulus of elasticity Costly

19. COMPOSITION Composite resin are composed of four major components, which are resin matrix, filler particles, coupling agent and activator-initiator system . Resin Coupling agent Filler

20. The resin matrix is a continuous phase into which all the other constituents are added. It is composed of aliphatic or aromatic diacrylates of which the two commonly used resin is formed by reaction between bisphenol A and glycidyl methacrylate . It is highly viscous. Diluent monomers such as triethylene glycol dimethacrylate are added to reduce the viscosity and allow filler particles to be added.

21. Dispersed in the resin matrix are the inorganic filler particles. Filler provide dimensional stability to the soft resin matrix.

22. For the composite material to perform well the filler particles have to be well bonded to the resin matrix. This is achieved through coupling agents. Silane contains functional groups, which hydrolyze and react with inorganic filler as well as unsaturated organic groups. Thus they are responsible for the bond between inorganic and organic phase of composite; hence promote stability to the system.

23. Activator-initiator system help in generating free radicals required for starting the polymerization reaction. However, to counteract spontaneous polymerization of the monomers, inhibitors like butylated hydroxyl toluene are provided. Optical modifiers are added in minute quantities to produce a variety of shades in the material.

24. CONSTITUENT EXAMPLE FUNCTION Resin matrix BisGMA , UDMA, TEGDMA it is a continuous phase to which other ingredients are added such as fillers, activator-initiator system, inhibitors etc FILLERS Zirconium oxide Crystalline quartz Borosilicate glass Lithium/barium aluminium silicate Silicon dioxide Aluminiumdioxide Fillers are added to improve the physical properties of the resin matrix such as; Decrease polymerization shrinkage Decrease coeff of thermal expansion Increase the hardness of material Makes the material more resistant to wear Decrease water sorption

25. CONSTITUENT EXAMPLE FUNCTION OPTICAL MODIFIERS Aluminium oxide Titanium oxide Metal oxides added in minute amounts Produce different shades in composite COUPLING AGENT Organosilanes like It bonds fillers particles to the resin matrix. This allows the more flexible polymer matrix to transfer stresses to the stiffer filler particles.

26. CONSTITUENT EXAMPLE FUNCTION ACTIVATOR , INITIAOR SYSTEM CHEMICAL CURE INITIATOR ACIVATOR LIGHT CURE ACTIVATOR INITIATOR Benzoyl peroxide Tertiary amine UV light source/ visible light Benzoin methyl ether/ camphoroquinone Generates free radicals to initiate addition polymerization reaction INHIBITOR Butylated hydroxy toluene they minimize or prevent spontaneous polymerization of the monomers.

27. PROPERTIES

28. LINEAR COEFFICIENT OF THERMAL EXPANSION It is a property, which determines the rate of dimensional change of a material per unit change in temperature . Ideally for any restorative material LCTE should be either coinciding or close to that enamel . This is important for the success of the restoration , as it reduces creation of a gap or voids a tooth restoration junction with change in temperature.

29. Composites have higher LCTE compared to tooth structure .with the improvement in the type and content of filler particles attempt is being made to reduce LCTE of composites. Linear rate of tooth approximately 9-11ppm/ºc. The LCTE of composites 28-45ppm/ºc. 3-4 times greater than the tooth structure.

30. It is a property, which relates to the material’s ability to resist surface loss due to abrasive forces . Wear resistance of composites is good , better than GIC, but less than that of amalgam. Factors influencing the wear of the material are: Filler content of the composite material Occlusal contact relation of the restoration WEAR RESISTANCE

31. Location of the restoration on the tooth & the tooth’s in the arch Abrasive effect of food bolus, toothbrush bristles , oral prophylaxis method etc. Rubbing of tooth contacts interproximally . Degree of polymerization of the material

32. WATER ABSORPTION It is the material’s ability to absorb water over time. Resin matrix in composites tends to absorb water making it swell. This leads to reduction in the effectiveness of the composite material and can also cause filler debonding and promote diffusion of unbound monomer . High filler content lowers water absorption tendency.

33. MECHANICAL PROPERTIES Macrofilled Microfilled Hybrid Packable Flowable 1 Filler size(µm) 8-12 0.04-0.4 0.6- 1.0 0.2- 2.0 0.2- 3.0 2 Filler vol % 60-65 20-55 60-65 59-80 42-62 3 Depth of cure _ 5 6.1 5.5 5.6 4 Compressive strength ( Mpa ) 200-300 200-250 250-300 220- 300 203 5 Ten sile strength _ 24 42 34 34

34. Macrofilled Microfilled Hybrid Packable Flowable 6 Elastic modulus 8-15 3-6 7-12 9-12 3-6 7 LCTE 25-35 50-60 30-40 _ _ 8 Water sorption 0.5-0.7 1.4-1.7 0.5-0.7 _ _

35. MODULUS OF ELASTICITY It is a measure of the stiffness of a material. Microfilled composites have low modulus of elasticity ,hence higher flexibility , whereas hybrid composites comparatively exhibit more rigidity . Therefore, microfills are preffered in class v and hybrids in class I & II.

36. RADIOPACITY Radiopacity is an important requirement for esthetic restorative materials to differentiate the restoration from radiolucent recurrent caries. Quartz and silica fillers used are radiolucent. Radiopaque fillers like barium / strontium /zirconium are added for this purpose.

37. COLOUR STABILITY It is an important property of an esthetic restorative material. Change of colour can result due to Staining Water exchange within the polymer matrix and interaction with unreacted polymer sites Stress cracks within the polymer matrix

38. POLYMERIZATION SHRINKAGE When the composite material is cured, the monomer gets converted to polymer and during the process there occurs polymerization shrinkage in the material. It has been observed that during the process of polymerization , about 55-65% of monomer gets converted to polymer and the remaining resin does not polymerize.

39. It leads to generation of internal stresses within the polymer chains and at the surface of the restoration which creates gap formation at the tooth surface restoration interface causing microleakage . The unbonded material present at surface of the restoration tends to distort trying to accommodate stress.

40. C - FACTOR Configuration factor is the ratio of bonded surfaces of the restorations to the unbonded surfaces. c – factor = bonded surface unbonded surface The significance of this ratio is that higher its value, greater is the polymerization shrinkage.

41. The developing polymerization shrinkage in a composite generate stress on the bonded interface that are in competition with the developing bond strength of the setting restorative (Adhesive) to the cavity surfaces, which may result in (partial) debonding , marginal leakage and post-operative pain

42. Methods to reduce polymerization shrinkage It can be decreased by incrementally adding and independently curing each increment of the composite material. The contraction within each small increment is less, thereby generating less stresses. Increasing the filler content of the restorative material. Soft start polymerization method helps in reducing internal stresses instead of high intensity light curing.

43. The most recent modification on the polymer matrix is based on using ring opening polymerization of the silorane molecules, instead of free radical polymerization of dimethacrylate monomers, which decreases polymerization shrinkage. Preheating composite before photo-activation, which provides better marginal adaptation and enhances the flow. Angulation of light tip and distance of curing tip also reduces the polymerization shrinkage.

44. DIFFERENT TYPES OF COMPOSITES

45. TRADITIONAL/ CONVENTIONAL/ MACROFILLED It is referred to as macrofilled because of relatively large size of filler particles. These traditional quartz particles were produced by grinding and milling with a particle size of around 8-12 microns. It generally contain 75%- 80% inorganic filler by weight. It is extremely hard, difficult to grind and polish, has the potential abrade opposing tooth structure .

46. Conventional composite have a higher amount of initial wear at occlusal contact areas than do the microfill or hybrid types. Disadvantages Due to selective abrasion the hard filler particles are left elevated producing rough surface. They show tendency to discolour due to susceptibility of rough surface to retain stain. Fracture of restoration is another commonly occuring consequence. USES :- class II & class IV

47. MICROFILLED COMPOSITES Microfilled composites were designed to overcome the drawbacks of conventional composites, chiefly being the rough surface characteristics. It contained submicron filler particles , approximately 0.01-0.04 µm in size. The manufacturing of microfilled composites involves addition of colloidal silica into the matrix

48. Untill the composites becomes very viscous. Then it is polymerized and ground into 5-50µm particles and are incorporated into non polymerized resin matrix. The resin is then filled with micro-filler, but only at half the conc. Of pre-polymerized resin fillers to avoid excessive thickening. The weakness of these material is that the bond between these pre-polymerized composite particles and curable matrix is weak decreasing its strength & allowing resin filler to be lost at the surface.

49. ADVANTAGES Due to small sized filler particles, they can be polished to the highest luster and smoothest surface. Highly finished restoration is less susceptible to plaque and extrinsic straining. 2. Most esthetic and it has low modulus of elasticity, hence high flexibility. In class v cavities , this property allowed the microfilled restorations to flex during tooth flexure without fracture.

50. DISADVANTAGES The bond between resin filler matrix interface is weak resulting in loss of resin filler from the material’s surface. Low tensile strength High water sorption, which softens the resin matrix decreasing strength. High polymerization shrinkage.

51. Clinical consideration:- Moderate stress areas requiring optimal polishability (class III & V)

52. HYBRID COMPOSITES This resin composite is achieved by using combination of macro and microfillers in the same material. This produced a hybrid category containing a blend of submicron fillers and small particle fillers. They provided improved physical properties due to high level filler loading made possible because of wide range of medium and small filler particle sizes.

53. Ground heavy metal glasses present 75-85 wt%. Colloidal silica present approximately 10-20wt%. Their high filler loading also improves the material’s resistance to intrinsic discolouration.

54. ADVANTAGES Good physical properties Improve wear resistance Superior surface morphology Good esthetics

55. Disadvantages Increased surface roughness with time Clinical consideration Anterior & Posterior restoration due to their superior surface smoothness and good strength.

56. NANOFILLED COMPOSITE These have nanofillers that are 0.005 to 0.01µm in size. These primary particles can be easily agglomerated allowing a full range of filler sizes. This makes possible increased filler loading and a reduced amount of resin matrix, thereby reducing shrinkage while providing esthetics and strength.

57. The main example of nanofilled composites is Filtek Supreme Plus. It can be strengthened by the addition of resin reinforced fillers with nanofibres .

58. NANO-HYBRID COMPOSITE Nano -hybrids comprises of milled glass fillers along with nano particles in the size range of 40-50nm. The smaller size of these particles enables higher filler loading and the distribution in the resin matrix and also tends to increase the interfacial area between the filler & the matrix leading to better dispersion and reduced polymerization shrinkage.

59. RECENT ADVANCES IN COMPOSITE

60. The recent advances in composite material can be grouped as follows: Direct restoration Indirect restoration Packable composite Art glass Flowable Composite Belle glass Compomer Fibre reinforced composite Giomer Ceromer Ormocer Smart composite Silorane Antimicrobial composite Self healing composite

61. PACKABLE / CONDENSABLE/HIGH DENSITY COMPOSITE These are composite materials having high filler loading. They were developed with an idea of having a composite material that has handling characteristics similar to amalgam. Their physical properties include low polymerization shrinkage, radiopacity , high depth of cure and good wear resistance. The Average filler particle size varies from 0.2 to 20µm

62. Uses They are intended primarily for large posterior restorations like class I & class II.

63. They can be easily packed or condensed in a cavity. It is easy to establish a good proximal contact. The occlusal anatomy of the restoration can be well shaped. Good fracture resistance. They can also be used as an underlying support for larger composite restoration ADVANTAGES

64. DISADVANTAGES They are opaque and unaesthetic materials, therefore not used for anterior restoration. Due to high viscosity, the difference layers are not properly adapted with each other. Presence of dry spots from inadequate resin saturation, resulting in weak areas. They do not completely accomplish handling properties similar to amalgam.

65. FLOWABLE COMPOSITE These are low viscosity, lightly filled composite material. The particle size of inorganic filler is in he range of 0.2-3.0µm and filler loading is 42-60% by volume. This materials should be placed in thin layers as they show high polymerization shrinkage. Placing them in bulk should be avoided.

66. INDICATION As a pit & fissure sealant. Restorative for small class I class III and class V abrasion areas. Repair resin for defective margins of composite restorations and crowns. Tunnel restorations Luting agent for porcelain / composite veneers. A thin veneer over resin modified glass- ionomer as it bonds well with dried RMGIC, it provide better colour stability & wear resistance.

67. ADVANTAGES Easy to use syringable materials. they show high wettability , which allows good adaptation of the restorative material to the prepared tooth surfaces High flexibility, therefore can be used in areas of tooth abfraction . Different shades High depth of cure

68. DISADVANTAGES They can no be used in high stress bearing areas due to low wear resistance & low strength. High polymerization shrinkage The material fatigues more quickly and breaks more frequently. The material stains easily.

69. COMPOMER ( polyacid modified composite resin) The term is an acronym derived from composite and glass- ionomer . Basically compomers are light polymerized composite resin restoratives, modified to contain ion- lechable glass particles and anhydrous polyalkenoic acid. This is why the term polyacid modified composite.

70. Compomer monomers contain acidic functional groups that can participate in an acid/base glass- ionomer reaction following polymerization of the resin molecule. A resin polymerization takes place with the compomers after the material has set completely. The glass- ionomer reaction(acid/base) may then occur in the presence of water.

71. In the presence of water from the oral cavity, the acid functional groups, which are attached to the monomer units, and have now become part of the polymerized material are able to react with the base (glass) to stimulate the glass ionomer reaction. Fluoride is released as a result of this reaction.

72. PROPERTIES Adhesion : for proper adhesion of the restoration to the tooth surface, acid etching of the tooth needs to be done. The restorations is retained micromechanically through resin tags. Acid base reaction for ion-exchange requires water does not occur for some time after placement.

73. Fluoride release : It shows limited fluoride release, which starts after 2-3 months. It is more than other comparable glass- ionomer formulations but less than conventional composite. Mechanical properties: inferior to convenional composite(low stress bearing areas). Good strength, biocompatible, low solubility.

74. INDICATIONS: Sealing and filling of occlusal pits and fissures. Restoration of deciduous teeth. Minimal cavity preparation or tunnel preparation As a liner Core-build up. Repair of defective margins in restorations. Class V repairs. Erosion Retrograde filing materials

75. GIOMER Giomers as the name suggests are a combination of glass- ionomer and composites, possessing properties of both the materials. They are resin based materials containing pre reacted glass – ionomer particles. PRG particles comprise of fluorosilicate glass, which has been reacted with polyacrylic acid and then incorporated into the resin.

76. PROPERTIES Light activated material. Require the use of bonding agent. Show excellent esthetics Easy polishability biocompatibility

77. INDICATION Class V abrasion, erosion and abfraction lesions Repair of defective margins in restorations.

78. ORMOCER Ormocer , the acronym of organically modified ceramic can be used as a restorative material for both anterior and posterior teeth. It consist of three components – organic portion, inorganic portion and the polysiloxanes . After polymerization, the organic portion of he methacrylate groups form as 3-dimentionally cross-linked polymers.

79. They are synthesized through solution and gelation process . Their coefficient of thermal expansion is very similar to natural tooth structure. These materials were formulated in an attempt to overcome the problems created by polymerization shrinkage of conventional composites. This class of materials combines the surface properties of silicons , toughness of organic polymers & hardness & thermal stability of ceramics.

80. ADVANTAGES Low polymerization shrinkage High abrasion resistance Good biocompatibility Provide protection against caries Highly esthetic , providing excellent final burnishing .

81. USES Direct restoration for all types of cavities Cosmetic veneer Orthodontic bonding adhesive

82. SILORANE It is a resin based composite comprised of two molecules siloxane and oxirane . The siloxane backbone was introduced in order to provide the most hydrophobic nature, which is important since too high water sorption limits the long term intraoral physical strength of the composites Oxirane is a cationic ring opening addition polymerizaiton reaction which stands for their low shrinkage and low polymerization stress.

83. The cationic cure starts with the initiation process of an acidic cation which opens the oxirane ring and generates a new acidic center , carbocation . After the addition to an oxirane monomer , the epoxy ring is opened to form a chain , or in the case of two-or multifunctional monomers a network is formed. The volumetric shrinkage 0.94-0.99vol%.

84. ADVANTAGES Low polymerization shrinkage and stress Less microleakage and better marginal integrity Less bacterial adhesion Less sensitive towards exogenic staining Good biocompatibility

85. ANTIBACTERIAL COMPOSITE Composites having antimicrobial properties have been tried by introducing agents like chlorhexidene , silver or some antibiotics into the material. The microbes get killed on contact with the material or through leaching of antimicrobial agents into the oral cavity.

86. Silver and titanium particles were introduced. Silver ions cause structural damage to the bacteria by direct contact and not by release of ions. Advantages Addition of silver ions caused No adverse effect on mechanical properties, strength no adverse effect on colour stability Good depth of cure

87. Methacryloxydecyl pyridinium bromide (MDPB) On polymerization, this monomer gets chemically bound to the resin matrix becoming part of the polymer network. Advantages It has been shown to be effective against streptococci No adverse effect seen on the mechanical properties of BisGMA

88. Chlorhexidene Addition of chlorhexidene was atempted in the composite resin, but it proved to be unsuccessful. Disadvantages Its addition caused deterioration of the physical and mechanical properties of the material The released chemical showed toxic effects Antibacterial activity was short lived.

89. SMART COMPOSITE Ivoclair introduced a material in 1998 named Ariston pHC (pH control). Ariston is an ion releasing composite material, which releases fluoride, hydroxyl and calcium ions as the pH drops in the areas immediately adjacent to the restorative material. This is said to neutralize the acid and counteract the decalcification of enamel / dentin.

90. The paste consists of Barium, Aluminium and Fluoride silicate glass filler (1µm) with Ytterbium trifluoride , silicon dioxide and alkaline calcium silicate glass in dimethacrylate monomers. Smart composites work based on the newly developed alkaline glass filler which will reduce secondary caries formation at the margin of a restoration by inhibiting bacterial growth. This results in a reduced demineralization and a buffering of the acid produced by caries forming microorganisms

91. SELF HEALING COMPOSITE Impact damage to composite structures can result in drastic reduction in mechanical properties. Bio-inspired approach is adopted to effect self healing which can be described as mechanical, thermal or chemically induced damage that is automatically repaired by materials already contained within the structure.

92. Resin matrix- GRUBB’s catalyst Dicyclopentadiene (DCPD) in microcapsules

93. INDIRECT RESIN COMPOSITE

94. These composites were developed to overcome the drawbacks of direct resin composites. They are processed in the laboratory under specialized conditions of heat/light/pressure to produce a cured material showing superior physical properties and lesser polymerization shrinkage.

95. ART GLASS It consists of resin matrix of BisGMA / UDMA and radiopaque filler of barium glass along with colloidal silica. Art glass is photocured using a special xenon stroboscopic light having 320-500 nm emission range.

96. Advantages High wear resistance Good marginal adaptation Esthetics Superior proximal contact Uses Most commonly used in inlays, onlays and crowns

97. Belle glass HP It was introduced by Belle de st . Clair in 1996 as indirect restorative material. Its consists of resin matrix of BisGMA and fillers. It is polymerized under pressure of 29 psi at temp. of 138ºc in the presence of nitrogen gas. The esthetics , wear resistance, polymerizaion rate is high due to High temp. Administered Presence of oxygen free enviroment

98. Ordinarily , oxygen tends to gets entrapped in the composites and interferes with polymerization process and also reduces translucency.

99. FIBRE REINFORCED COMPOSITE Major components: resin matrix and fibers Fibers - Ceramic Glass Carbon Alumina Silicon nitride - Polymer KEVLAR (unidirectional) HDLPE Due to translucent appearance of these materials no masking materials are needed, which allows a thin layer(0.5mm) of composite to be placed , which is esthetic .

100. Uses Meal-free restorations, which may be inlay, onlay , crown Periodontal splinting or post trauma spilinting Fixed bridges Implant supported crowns fixed orthodontic retainers Repairing dentures

101. Ribbond Ever stik

102. CEROMER Ceromers are a specific combination of the latest in ceramic filler technology and advanced polymer chemistry that provide enhanced function and aesthetics. Contains barium glass (< 1 μm ), spheroidal mixed oxide, ytterbium trifluoride , and silicon dioxide (57 vol %) in dimethacrylate monomers ( Bis - GMA and urethane dimethacrylate . They exhibit fluoride release lower than conventional glass- ionomers or compomers .

103. Indications Class I and II posterior restorations (stress bearing areas) Class III and IV anterior restorations Class V restorations cervical caries, root erosion, abfraction , wedge-shaped defects Inlays/ onlays with extraoral post-tempering

104. GENERAL STEPS IN CLINICAL PROCEDURE While using composite material for restoration, stepwise clinical technique has to be followed: Local anaesthesia Preparation of operating site Shade selection Isolation of operating site Assessment of occlusal contacts Tooth preparation procedure Restorative technique Inserting and curing composite Design of Incremental technique Developing contacts Finishing & polishing

105. LOCAL ANESTHESIA This is preferred in most patients as it reduces apprehension and salivation . Administering local anaesthesia makes the patient relaxed and comfortable thus contributing to better operative dentistry, especially while placing bonded restorations. It can be omitted in the case preparation is very shallow.

106. Cleaning and preparing operating site It is important that the tooth surface is clean without having any plaque, pellicle , calculus or stains. This makes the surface more receptive to bonding , which is important for the long term success of he restoration. Prophylactic pastes containing flavouring agents, glycerine or fluorides should be avoided as they may interfere with acid etching.

107. SHADE SELECTION While dealing with esthetic restorative materials, selecting the appropriate shade is an important step. Composite shade is selected before placing the rubber dam, without excessive tooth drying and matched with clean moist tooth surface. Colour of the rubber dam tends to reflect on the tooth surface and the teeth when subjected to prolonged drying get dehydrated , which makes them lighter in shade due to decrease in translucency.

108. Therefore both are avoided. Also colour of the tooth is influenced by factors such as thickness , translucency & distribution of enamel & dentin, intrinsic and extrinsic stains, age of the patient, trauma and root canal treatment.

109. Many shade guides are available in the market to the help shade selection Universally adopted shade guide is VITA shade guide. This shade guide first the shades into hues and then shows hues with increased chroma and decreased value. While making colour selection good lightening is very important, natural light being a better option.

110. Colour acuity and eye fatigue The colour selection should be made as quickly as possible because the colour receptors of the eye are unable to distinguish between similar colours after approximately 30 sec. After selection to confirm the shade, a small amount of the selected shade can be directly placed on the tooth close to the area to be restored and cured.

111. ISOLATING OF OPERATING SITE Composite materials are very sensitive to water contamination. Contamination of etched tooth surfaces with oral fluids interferes with bond formation and also causes degradation of physical properties of the material. Adequate isolation can be achieved by using rubber dam. It not only achieves adequate access, vision and moisture control, but also causes retraction of the soft tissues.

112. ASSESSMENT OF OCCLUSAL CONTACTS Preoperative assessment of the occlusal contacts should be made. It is important to identify occlusal contacts of the teeth to be restored, mandibular closure pattern, or any abnormal forces acting. This can influence the stability of the restoration.

113. TYPES OF TOOTH PREPARATIONS Tooth preparation designs vary depending on the clinical situation. Conventional Bevelled conventional Modified box-only Slot preparation

114. CONVENTIONAL DESIGN These are typical amalgam cavity preparation designs with uniform depth , flat floors, butt joint and retention grooves in dentin. This design is indicated for cavity preparations on root surfaces and for large class I & class II composite restoration.

115. BEVELLED CONVENTIONAL This tooth preparation design is similar to conventional but with some bevelled enamel margins. Bevelling exposes the ends of the enamel rods , which allows them to be more effectively etched than when only the sides are exposed to acid etchant. Also, there is an increase in the etched surface area. These together result in stronger enamel- to-resin bond. Bevel is given at an angle of 45º to the cavosurface .

116. Due to such preparation shows: Reduced marginal leakage Less marginal discoloration More retention Better esthetic blend of the restoration to the tooth surface.

117. INDICATION It is indicated when an old amalgam or other defective restoration, having conventional tooth preparation design with enamel design with enamel margin, is to be replaced with composite restoration. For class III, IV, V and VI restoration For restoring large carious lesion in which there is anticipation of increased retention and resistance form.

118. CONTRAINDICATION Bevel are indicated on the proximal margins. Bevels are not placed on occlusal surfaces of posterior teeth or other areas of potentially heavy contacts.

119. MODIFIED PREPARATION It is an scooped out preparation whose depth and extent are dependent solely upon that of the carious lesion. There is no specified wall design or axial/ pulpal depth. No uniform dentinal depth is achieved.

120. INDICATIONS Small or moderate sized lesions having enamel margins. For correcting enamel defects.

121. BOX-ONLY Box only design involves the formation of box shaped preparation restricted only to the proximal surface. A proximal box is prepared with either an inverted cone or round diamond stone held parallel to the long axis of the tooth & it made to cut through the marginal ridge in the gingival direction.

122. The initial proximal axial depth is 0.2mm in the dentino -enamel junction. The extent of the preparation is determined by the size and depth of the caries.

123. SLOT PREPARATION Facial/ lingual slot preparations are restricted to the proximal surfaces of posterior teeth having assess to the lesion either from facial/lingual direction. Proximal surface lesions, which can be easily accessed from the facial/ lingual direction instead of occlusal direction. Preparation is mostly made using a round bur. The initial axial depth is 0.2mm in the dentin enamel junction. The cavosurface margin are 90º or greater.

124. RESTORATIVE TECHNIQUE The steps for the restorative technique are as follows: Etching and bonding Matrix & wedge application Inserting and curing

125. ETCHING AND BONDING The entire cavity preparation including the enamel margins are etched with 30-40% phosphoric acid. In case of proximal preparations before etching, the proximal surface of unprepared tooth is protected by placing a polyester strip. The etchant is applied to all of the prepared tooth surface and about 0.5mm beyond the prepared margins onto the unprepared tooth.

126. The application time for the etchant is 15-30 sec. The area is then washed and dried. Over drying using an air spray should be avoided. With a micro-brush or an applicator tip, the primer and adhesive are applied as per manufacturer’s instruction. After application , it is lightly dried with an air syringe to evaporate any solvent like acetone, alcohol or water followed by polymerization with light curing.

127. MATRIX AND WEDGE APPLICATION Matrix applied to the proximal surface of the prepared tooth before inserting restoration material. It serves purpose of: Confining the restorative material. Assisting in development of appropriate tooth contours . Isolating the tooth preparation. Enhancing the effectiveness of enamel /dentin bonding system. Reduces the amount of excess material and minimizes the finishing time.

128. For class III : matrix used The commonly used matrix is pre-contoured clear polyester strip. The proximal surface of the tooth is usually convex and the strip is flat, so it is necessary to shape the strip to conform to tooth contours. For class IV : clear plastic or celluloid crown form clear polyester strip matrix For class II: tofflemire matrix system

129. Matrix should extend just above ( occlusal to) the marginal ridge and below (gingival to) the gingival margin.

130. Types of matrix used in case of composite restoration : Clear polyester matrix with tofflemire retainer used with light reflecting wedge. Ultrathin universal metal (0.001 inch)matrix with tofflemire retainer . Tofflemire metal matrix with phototech thinned (0.0005 inch) contact areas. Thin sectional metal matrix (0.0015 inch) with metal rings. Customized compound supported sectional metal matrix.

131. Wedge is placed into the gingival embrasure and is positioned between the two adjacent teeth, below the prepared gingival margin, and exterior to the matrix material. FUNCTIONS To seal the gingival margin by pressing the matrix against the prepared tooth. To separate the tooth. Protects the inter-proximal gingiva .

132. Ensures formation of good proximal contact, by preventing gingival overhang of the restoration. The rubber dam and proximal tissues are pushed proximally to open the gingival embrassure . Pre-wedging allows greater separation of teeth and more space to build the contact.

133. INSERTING AND CURING COMPOSITE The composite restoration usually is placed in two stages. First, a bonding adhesive is applied. Second, the composite restorative material is inserted. Etching and priming the prepared structure and placing the bonding adhesive should be done according to manufacturer’s direction.

134. Composite available are of two types: Self cured Light cured

135. Self cure also referred to as chemically activated resins or auto cure resin. They are marketed in two pastes, one contains the initiator ( benzoyl peroxide) and the other contains activator (tertiary amine). As the two pastes are mixed, amine interacts with the peroxide to produce free radicals , i.e a compound with reactive unpaired electron. These radicals attack the carbon double bonds in resin monomer initiating addition polymerization.

136. Polymerization occurs centre of the material Sets within 45 seconds No control over working time Shrinkage towards centre of bulk Air may get incorporated More wastage of material Not properly finished

137. Light activated resin are two types UV light Visible light in UV activated system, the activator was UV light at 365nm wavelength, which spilt benzoin methyl ether (initiator) into the free radicals. Due to their drawbacks, this system was replaced by visible light activated resins.

138. In this system visible light at 470nm wavelength is used as an activator. It shows rapid cure. On command setting occurs. Better colour stability due to aliphatic amine initiator.

139. Many studies recommended the use of flowable composites as the first increment to allow through adaptation to all areas of cavity preparation. However, flowable resins show high polymerization shrinkage. To over come this, some authors advocate the use of ‘ snow plow technique ’.

140. Snow plow technique The use of flowable composites in conjunction with posterior resin composite restorations has been called the snow- plow technique. The technique has demonstrated significantly reduced void formation compared with placement of restorative composite alone. In this technique an initial increment of flowable composite is placed over the gingival and pulpal floors of the cavity preparation.

141. This layer is not cured at this stage, but rather an initial increment of heavily filled restorative resin composite is syringed or pushed into the unset flowable resin composite. This technique is said to show advantages such as: better marginal adaptation and reduced void formation.

142. Injectable composite material is available as syringes with disposable needles or self contained compules with syringe tips of various shades. The syringe technique has advantages that i ) it provides a convenient means of transporting the composite to the preparation ii) reduces the possibility of trapping air.

143. INCREMENTAL LAYERING TECHNIQUE When placing posterior composites, the use of small increments is recommended by many authors for insertion and polymerization so that the after effect of shrinkage stress can be reduced.

144. HORIZONTAL LAYERING TECHNIQUE The horizontal placement technique utilizes composite resin layers, each layer <2.0 mm thick. This technique has been reported to increase the C-factor, and thereupon increases the shrinkage stresses between the opposing cavity walls.

145. OBLIQUE LAYERING TECHNIQUE The oblique technique is accomplished by placing a series of wedge-shaped composite increments. Each increment is photo cured twice, first through the cavity walls and then from the occlusal surface, to direct the vectors of polymerization toward the adhesive surface. This technique reduces the C-factor and prevents the distortion of cavity walls

146. VERTICAL LAYERING TECHNIQUE Place small increments in vertical pattern starting from one wall, i.e., buccal or lingual and carried to another wall. Start polymerization from behind the wall, i.e., if buccal increment is placed on the lingual wall, it is cured from outside of the lingual wall. This reduces gap at gingival wall which is formed due to polymerization shrinkage, hence postoperative sensitivity and secondary caries.

147. U-SHAPED LAYERING TECHNIQUE First a U- shaped increment is placed at the base both occlusally and gingivally . It is followed by horizontal and oblique increments to fill the preparation. Curing is done from the all sides.

148. LIGHT CURING UNITS Light curing can be accomplished with Quartz-Tungsten-Halogen curing unit Plasma arc curing unit Laser curing unit Light emitting diode curing unit

149. In order of lowest to highest intensity LED lamps QTH lamps PAC lamps Argon laser lamps

150. The aim of any curing unit is to maximize light energy in the absorption range of the photoinitiator present in the composite being cured. Most commonly used photo-initiator is camphoroquinone , which when exposed o 474 nm wavelength absorbs photos of light energy and initiates polymerization reaction.

151. QUARTZ-TUNGSTEN-HALOGEN Most widely used dental curing light. Consists of a quartz bulb with a tungsten filament in a halogen environment. Electric current passes through an extremely thin tungsten filament which at about 3000ºC produces Electro Magnetic radiation in the form of visible light.

152. Quartz encasing structure crystalline heat resistant Tungsten filament coil flow of electricity Halogen gas protects filament . Power Density: 500-1500mW/cm2

153. Band-pass filters restricts broader light to narrow blue light 400-500 nm range of photo-initiators 99.5% of original radiant energy filtered

154. Advantages: Economical. Filters used to dissipate heat to the oral structures & provide restriction of visible light to narrower spectrum of initiators. Disadvantages: Diminished light intensity over a period of time causes degradation of halogen bulb & degradation of reflector. Shorter life about 100 hrs. High temperature production. Bond strength decreases with increase in distance.

155. PLASMA-ARC (PAC) High voltage is generated between two tungsten electrodes creating a spark that ionizes Xenon creating a conductive gas known as Plasma. These lamps are characterized by a high energy output in a narrow range of wavelength.

156. Wavelength 400-500 nm. Has a highly filtered photosensor which measures light coming from end of curing tip based on which microcomputer calculates the time required for curing.

157. Advantages: High irradiance up to 2400 mW /cm2 claim 1-3 sec cure. Power density of 600-2050 mW /cm2 Disadvantages: Expensive. High temperature development. Heavy so not portable. Requires an in built filter to produce narrow continuous spectrum.

158. ARGON LASER Laser sources emit monochromatic light at a few distinct frequencies within the desired range to initiate polymerization of composites. Argon laser generates one wavelength of blue light having a band width of 40-45 nm.

159. ADVANTAGES: Produces narrow focused non divergent monochromatic light of 490nm. Less power utilized. Thoroughness and depth of cure is greater. Laser curing bond strength did not decrease with increasing distance. DISADVANTAGES: Risk of other tissues being irradiated. Ophthalmic damage of operator and patient. Large in size and heavy. expensive

160. LIGHT-EMITTING DIODES (LED) Combination of two semiconductors n doped & p doped. n doped have excess of e- & p doped have holes. When both types are combined & voltage is applied e- & holes connect resulting in emission of light of characteristic wavelength.

161. Initially used Silicon Carbide electrode. When LED of suitable band gap energy is used they produce only the desired wavelength range. Narrow emission spectrum – 400-490 nm peak at 470 nm near absorption max of camphoroquinone .

162. Advantages: Long service life of more than 100hrs. Low temperature development. No filter system. Low power consumption. Wavelength of 400-490nm. Disadvantages: Photoinitiator is only CQ. Requires longer exposure time to adequately polymerize microfills & hybrid resin.

163. FINISHING & POLISHING FINISHING : process of removing surface defects or scratches created during the contouring process through the use of cutting or grinding instruments or both. Polishing : process of providing luster or gloss on a material surface.

164. FLUTED FINISHING BURS They are available in 8,12,16,20 30 fluted bur design. The fewer the flutes, the more aggressive is the cutting . They are used for finishing composites. 30 fluted burs can be used to smooth, abrade porcelain surfaces before application of diamond polishing pastes. Several specific group of fluted finishing burs have been developed for finishing of composites known as esthetic trimming burs.

165. FINISHING KIT These kits are designed for reducing and finishing composite fillings, also in interproximal & subgingival areas. Eg : Sof-Lex discs (3M ESPE)

166. Rubber wheels, cups and point: They can be used for initial contouring, smoothing and finishing depending on the grit. Eg : vivadent polishing cups and points. Proximal finishing strips: These strips are made of metal or plastic. They are best suited for enamel disking before cutting a preparation and finishing a restoration after final contouring.

167. REFERENCES Phillips’: Science of dental materials Sturdevant : Art and science of operative dentistry Vimal Sikri : Textbook of operative dentistry Marzouk : Operative dentistry – moder n theory and practice Craig : Dental marterials Charbeneau : Principles & practice of operative dentistry Goldstein : Esthetics in dentistry