COMPOSITE AS AMATERIAL (BASIC CONCEPT OF COMPOSITE AS AMATERIAL)

THIS SLIDE GIVES YOU AN IDEA OF USING COMPOSITE AS MATERIAL IN A BRIEF MANNER ALONG WITH REFERENCE GIVEN IN EACH AND EVERY SLIDE.HOPE THIS HEPLS YOU

1. COMPOSITE –AS A MATERIAL Presented BY , THARA ELIZABETH JES,1 st year Pg DEPARTMENT OF CONSERVATIVE DENTISTRY AND ENDODONTICS GUIDED BY, DR.DEEPAK KURUP DR.SHAZIA MAHREEN DR.RITU RAJ DR.HRISHITA MAJUMDAR

2. Content Definition History Composition Classification Polymerization Types of Composites Recent Advances Properties Indications Contraindications Advantages Disadvantages References

3. Definition: According to Phillips : Composite is defined as, In materials and science, a solid formed from two or more distinct phases (e.g., particles in a metal matrix) that have been combined to produce properties superior to or intermediate to those of the individual constituents. According to Skinners : Dental composites are highly cross-linked polymeric materials reinforced by a dispersion of glass, crystalline, or resin filler particles and/or short fibers bound to the matrix by silane coupling agents

4. HISTORY 1871 : Thomas Fletcher introduced a plastic filling called silicate cement. Its use in dentistry continued till early 1960s These cements resulted from reactions of phosphoric acid with acid soluble glass particles(aluminosilicate) to form a silica gel matrix containing residual glass particles. Disadvantages solubility pulpal irritation Solubility problems with these materials led to the introduction of unfilled acrylic systems based on polymethyl methacrylate (PMMA). Phillips Science Of Dental Materials 12 th edition

5. 1936 polymethyl methacrylate{ (PMMA) 1843 : J. Redtenbacher } was introduced to the dental profession in as Vernonite Disadvantages volumetric shrinkage during polymerization a large difference in the thermal expansion coefficient between PMMAs and the surrounding tooth lack of color stability marginal staining and recurrent caries was identified at the restoration/tooth interface Phillips Science Of Dental Materials 12 th edition

6. 1955 Bunoncore advocated acid etching for the mechanical retention of polymer. 1956 : American dentist Dr. Ray L. Bowen, working at the National Bureau of Standards in Washington DC, synthesized a new monomer Bis-GMA, initiating the era of dental resin composites Phillips Science Of Dental Materials 12 th edition

7. 1962 : Resins containing BisGMA were known as “Bowen’s resins” 1965 : He patented the combination BisGMA resin and silane-treated quartz particles, which is the origin of most resin composites on the market today . Phillips Science Of Dental Materials 12 th edition

8. COMPOSITION 3 structural components in dental resin based composites: Matrix: Continuous phase Filler: Dispersed in matrix Coupling agent: Bonds filler and resin matrix. Also contain Hydroquinone:inhibit or prevent premature polymerization UV absorbers:to improve color stability Opacifiers: e.g titanium dioxide and aluminium oxide Color pigments:to match tooth color Phillips Science Of Dental Materials 12 th edition

9. Schematic representation of different components of composite resin

10. RESIN MATRIX Most dental composites use a blend of aromatic and or aliphatic dimethaacrylate monomers Such as bis glycidyl methacrylate (bis-GMA) Tri ethylene glycol dimethacrylate (TEGDMA) Urethane dimethacrylate (UDMA) Shrinkage occurs during curing as monomers are converted from an aggregate of freely flowing molecules of a rigid assembly of cross linked polymer chains Before polymerization the monomers are held loosely by Van der waal forces at a spacing that produces minimum potential energy Phillips Science Of Dental Materials 12 th edition

11. Bis-GMA and UDMA are viscous so makes the matrix stiffer but also makes filler loading difficult . The lower the viscosity of the monomer mixture, the more filler may be incorporated into the mixture. The high viscosity of these are lowered by admixture with dimethacrylate monomers of lower molecular weight to achieve a viscosity suitable for incorporating fillers Dilution also has negative effects such as increased polymerization shrinkage . Phillips Science Of Dental Materials 12 th edition

12. FILLER PARTICLE Fillers are employed to strengthen composite as well as to decrease curing shrinkage. Fillers are in different size and shape. Include fused quartz, aluminum silicate, lithium aluminum silicate, ytterbium fluoride,barium,strontium,zirconium,etc Increasing the filler content in a material increase the strength and decreases the amount of polymerization shrinkage A contemporary composite resin for restoration should contain atleast 75%filler by weight. Materials with smaller filler particles are more polishable, retain the polish for a longer period and have improved wear resistance. Phillips Science Of Dental Materials 12 th edition

13. FUNCTION OF FILLERS Reinforcement of matrix resin, Increasing hardness, strength Abrasion resistance. Decreasing wear Phillips Science Of Dental Materials 12 th edition

14. Reduction in polymerization shrinkage Reduction of thermal expansion and contraction Less interfacial stress Improved workability. Reduction in water sorption, softening and staining Increased radiopacity Strontium (Sr) and barium (Ba) Phillips Science Of Dental Materials 12 th edition

15. COUPLING AGENTS Bonds filler particles to resin matrix Allows the more flexible resin matrix to transfer stresses to the more rigid filler particles. Properly applied coupling agent can impart improved physical and mechanical properties Inhibit leaching by preventing water from penetrating along the filler resin interface. Most commonly used coupling agents: Organosilanes : 3- methacryloxypropyl trimethoxysilane Phillips Science Of Dental Materials 12 th edition

16. The methoxy (OCH3)groups are hydrolyzed to silanol(-Si-OH) groups, which can bond with other silanols on the filler surface by forming siloxane bonds(-Si-O-Si-). The organosilane methacrylate groups form covalent bond with the resin when it is polymerized, thereby completing the coupling process Zirconates and Titanates can also be used as coupling agents Basic Dental Materials second edition :John J Manappallil

17. CLASSIFICATION OF COMPOSITES Marzouk classified composite into 6 generations 1 st-Micro ceramics 2nd- Colloidal &micro ceramic phases 3rd- Hybrid: macro and micro colloidal ceramics 4th-Hybrid:heat cured irregularly shaped 5th-Hybrid:heat cured spherical 6th-Hybrid:agglomerates of sintered micro ceramics

18. • According to Skinner: – Traditional or conventional composite—8–12 μ m – Small particle filled composites—1–5 μm – Microfilled composites—0.04–0.4 μ m – Hybrid composites—0.6–1 μ m • Philips and Lutz classification according to filler particle size: – Macrofiller composites ( particles from 0.1-100 μ) – Microfiller composites (0.04 μ particles ) – Hybrid composites (fillers of different sizes).

19. According to Sturdevants Based on Polymerization method: Light cured composites Chemical cure composites Dual cure composites Based on filler particle size: Macrofilled Microfilled Hybrid Microhybrid Nanohybrid Based on viscosity: Packable composites Flowable composites

20. Polymerization The resin component of a cured dental resin composite is a polymeric matrix. A polymer is a large molecule built up by repetitive bonding together of many smaller units called monomers. The process by which monomers are joined together and converted into polymers is called polymerization. The extent to which monomer is changed into polymer is termed the degree of conversion. Phillips Science Of Dental Materials 12 th edition

21. Addition Polymerization Here monomers are activated one at a time and added together in sequence to form a growing chain. Most dental resins are polymerized by a mechanism in which monomers add sequentially to the end of a growing chain. Addition polymerization starts from an active centre , adding one monomer at a time to rapidly form a chain T he chain can grow indefinitely until the entire monomer is exhausted Stages in additional polymerization INDUCTION PROPAGATION CHAIN TRANSFER TERMINATION Basic Dental Materials second edition :John J Manappallil

22. Induction: For an ADDITION POLYMERISATION to begin, a source of free radicals R* is required Free radicals can be generated by activation of radical producing molecules using a second chemical, heat , visible light , UV light , or energy transferred from another compound that is transmitted as a free radical FREE RADICALS- a free radical is an atom or a group of atoms possessing an unpaired electron The unpaired electron confers electron withdrawal ability to the free radical When the free radical and the unpaired electron approach the monomer with its high electron density double bond, an electron is extracted, and it pairs with the free radical electron to form a bond between the radical and the monomer molecule leaving the other electron of the double bond unpaired Basic Dental Materials second edition :John J Manappallil

23. Thus the original free radical bonds to one side of the monomer molecule and forms a new free radical site at the other end The reaction is now initiated The free radical forming channel used to start the polymerization is more accurately called an initiator because it is used to start a reaction Basic Dental Materials second edition :John J Manappallil

24. Propagation: The resulting free radical monomer complex then acts as a new free radical centre when it approaches another monomer to from a dimer which also be comes a free radical Basic Dental Materials second edition :John J Manappallil

25. Chain Transfer:

26. Termination: Although chain termination can result from chain transfer, addition polymerization reactions are more often terminated either by direct coupling of two free radical chains ends or by the exchange of a hydrogen atom from one growing chain to another Basic Dental Materials second edition :John J Manappallil

27. According to polymerization method 1) Chemical cure: They are supplied as two pastes, base paste which contains the benzoyl peroxide initiator and a catalyst paste which contains an aromatic tertiary amine activator(N,N dimethyl-p- toulidine ) When the two pastes are mixed together, the amine reacts with benzoyl peroxide to from free radicles and additional polymerisation is initiated . One problem with chemical cure is that it is not possible to avoid incorporation of air into the mix thereby forming pores that weakens the structure and trap oxygen which inhibits polymerisation during curing. Another problem is that the operator has no control over the working time after the two components are mixed.So insertion and contouring must be completed quickly once the components are Colour instability:Aromatic amines accelerators oxidize and turn yellow with time Phillips Science Of Dental Materials 12 th edition

28. Chemical cure: Benzoyl peroxide initiator N, N- dimethyl -p- toluidine activator FREE RADICAL Addition polymerization

29. 2)Light cure: a) UV Light Activated systems: The first light activated systems were formulated for UV light to initiate free radicles Initiator – benzoin methyl ether Activator U-V light 365nm In UV light-activated systems, a 365-nanometer (nm) UV light source splits benzoin methyl ether (in amounts of 0.2%) into free radicals Their limitations were: Limited penetration of the light into resin . Thus,it was difficult to polymerize thick sections Lack of penetration through tooth structure. curing units require a 5-minute warm-up period. Phillips Science Of Dental Materials 12 th edition

30. b)Visible Light Activated systems: Supplied as single paste in light-proof syringe. Free radical initiating system Photosensitizer[ Camphoroquinone (0.2 wt % or less)] + amine activator[ Dimethylaminoethyl Methacrylate, (0.15 wt %)] exposure to light 468 nm, blue light Free radicals Addition polymerization Phillips Science Of Dental Materials 12 th edition

31. Advantages over chemically activated resins: Mixing not required, less porosity Less staining Increased strength Color stability Working time is under operator’s control Curing accomplished in shorter:- less than or equal to 40 seconds to cure a 2mm thick layer. Phillips Science Of Dental Materials 12 th edition

32. Disadvantages: Relatively poor lamp accessibility in certain posterior areas and interproximal areas. Limited curing depth Must be placed incrementally when bulk exceeds more than 2mm. May require more time for large restorations, e.g., class II restorations Cost of light curing unit. Sensitivity to room illumination. Phillips Science Of Dental Materials 12 th edition

33. Initiator-Activator system used in various types of composites Difference between chemically cured and light cured composites

34. Difference between visible light and ultraviolet light curing

35. 3) Dual cure: Consists of two light curable pastes, one containing benzoyl peroxide and the other containing an aromatic tertiary amine accelerator They are formulated to set up very slowly when mixed via the self cure mechanism. The cure is then accelerated on’command’via light curing. Combines chemical and light curing Disadvatages:air inhibition ,porosity

36. Based on filler particle size Conventional composite: Developed during 1970s Also known as macrofilled composites Most commonly used filler: Amorphous silica Quartz Filler loading: 70-80 wt % Sturdevants art and science of operative dentistry 5 th edition

37. Disadvantages: Large size and extreme hardness of filler particle cause rough surface texture Resin matrix wears away at a faster rate than filler partcles causing further roughening of surface which cause discolouration from extrinsic stains. Higher wear at occlusal contact area " plucking" effect caused by loss of filler particles from the matrix i.e large particles are plucked from the surface of posterior restoration by opposing cusp tips and result instantly in a quantam loss of restorative material. Examples: Adaptic (J&J), Concise (3M ESPE) Sturdevants art and science of operative dentistry 5 th edition

38. Microfilled composite: Use colloidal silica To overcome problem of roughness of small particle composites. 0.04mm in diameter Small particle size results in a smooth, polished surface making it less receptive to plaque and extrinsic staining. Contain inorganic filler content by 35-60%by weight Low modules of elasticity allowing the restoration to flex during tooth flexure better protecting the bonding interface. This feature may make microfill composites an appropriate choice for restoring Class V cervical lesions or defects in which cervical flexure can be significant (e.g., bruxism, clenchers, stressful occlusion) Sturdevants art and science of operative dentistry 5 th edition

39. Hybrid composite: In an effort to combine the favorable physical and mechanical properties characteristics of conventional composites with the smooth surface typical of the microfill composites, hybrid composites were developed. These materials generally have an inorganic filler content of approximately 75to 85% by weight. The filler is typically a mixture of microfiller and small filler particles that results in a considerably smaller average particle size (0.4-1 mm)than that of conventional composites. Because of the relatively high content of inorganic fillers, the physical and mechanical characteristics are generally superior to those of conventional composites. Also, the presence of submicrometer -sized microfiller particles interspersed among the larger particles provides a smooth ”surface texture in the finished restoration. Sturdevants art and science of operative dentistry 5 th edition

40. According to viscosity Flowable composite: Flowable composites have lower filler content and consequently inferior physical properties, such as lower wear resistance and strength compared with more heavily filled composites. They also exhibit much higher polymerization shrinkage and should always be placed in thin layers. Filler content ranging between 35-65% by weight Caan be used as the first increment placed as a liner under hybrid or packable composites. Sturdevants art and science of operative dentistry 5 th edition

41. Packable composite: Packable composites are designed to be inherently more viscous to afford a “feel” on insertion, similar to that of amalgam. Because of increased viscosity and resistance to packing, some lateral displacement of the matrix band is possible. No long-term clinical studies equate packable composites’ promoted benefits with improved clinical results compared with other hybrid composites. Their development is an attempt to accomplish two goals: (1) easier restoration of a proximal contact and (2) similarity to the handling properties of amalgam Sturdevants art and science of operative dentistry 5 th edition

42. PROPERTIES OF COMPOSITES Coefficient of Thermal Expansion The LCTE is the rate of dimensional change of a material per unit change in temperature. Coefficient of thermal expansion of composites is approximately three times higher than normal tooth structure. This results in more contraction and expansion than enamel and dentin when there are temperature changes resulting in loosening of the restoration . It can be reduced by adding more filler content. Microfill composites show more coefficient of thermal expansion because of presence of more polymer content. Sturdevants art and science of operative dentistry 5 th edition

43. Water Absorption Water absorption is the amount of water that a material absorbs over time per unit of surface area or volume. Composites have tendency to absorb water which can lead to the swelling of resin matrix, filler debonding and thus restoration failure. Composites with higher filler content exhibit lower water absorption and therefore better properties, than with lower filler content. Factors Affecting Water Absorption of Composites: More is the filler content, lesser will be water sorption. Sturdevants art and science of operative dentistry 5 th edition

44. Wear Resistance Wear resistance refers to material’s ability to resist surface loss as a result of abrasives contact with opposing tooth structure, restorative material or tooth-brushing, etc. Wear resistance is a property of filler particles depending on their size and quantity. Composites are prone to wear under masticatory forces, toothbrushing and abrasive food . Site of restorations in dental arch and occlusal contact relationship, size, shape and content of filler particles affect the wear resistance of the composites. Sturdevants art and science of operative dentistry 5 th edition

45. Surface Texture Size and composition of filler particles determine the smoothness of surface of a restoration. Microfill composites offer the smoothest restorative surface. This property is more significant if the restoration is in close approximation to gingival tissues Although microfill composites offer the smoothest restorative surface, hybrid composites also provide surface textures that are esthetic and compatible with soft tissues. . Sturdevants art and science of operative dentistry 5 th edition

46. Radiopacity Resins are inherently radiolucent. Presence of radiopaque fillers like barium glass, strontium and zirconium makes the composite restoration radiopaque. Modulus Of Elasticity Modulus of elasticity of a material determines its rigidity or stiffness. Microfill composites have greater flexibility than hybrid composite since they have lower modulus of elasticity. This is particularly true for Class V restorations in teeth experiencing heavy occlusal forces, where stress concentrations exist in the cervical area. Such stress can cause tooth flexure that can disrupt the bonding interface .Using a more flexible material, such as a microfill composite,allows the restorations to bend with the tooth , better protecting the bonding interface Sturdevants art and science of operative dentistry 5 th edition

47. Polymerization Shrinkage: Composite materials shrink while curing which can result in formation of a gap between resin-based composite and the preparation wall . Shrinkage in light cured composites occurs in the direction of light For chemical cured composites shrinkage occurs slowly and uniformly towards the center of restoration Sturdevants art and science of operative dentistry 5 th edition

48. Polymerization shrinkage can result in gap between restoration and the tooth surface In light cured composites, shrinkage occurs towards source of light (A) Incremental technique; (B) Bulk technique Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg

49. In chemical cured composites, shrinkage occurs towards center of restoration Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg

50. Polymerization shrinkage usually does not cause significant problems with restorations cured in preparations having all-enamel margins. When a tooth preparation has extended onto the root surface, however, polymerization shrinkage can (and usually does) cause a gap formation at the junction of the composite and root surface The V-shaped gap occurs because the force of polymerization of the composite is greater than the initial bond strength of the composite to the dentin of the root. The V-shaped gap is probably composed of composite on the restoration side and hybridized dentin on the root side. Sturdevants art and science of operative dentistry 5 th edition

51. Contraction gap (exaggerated). A, V-shaped gap on root surface. B, Restoration-side vector is composite; root-side vector is hybridized dentin. Sturdevants art and science of operative dentistry 5 th edition

52. If extending onto the root surface, there may be benefits to placing a RMGI first in the gingival portion of the preparation on the root followed by the composite. This approach may reduce the microleakage and gap formation potential and render the surrounding tooth structure more resistant to recurrent caries. Another important clinical consideration regarding the effects of polymerization shrinkage is the configuration factor (C-factor). The C-factor is the ratio of bonded surfaces to the unbonded, or free, surfaces in a tooth preparation. The higher the C-factor, the greater is the potential for bond disruption from polymerization effects Sturdevants art and science of operative dentistry 5 th edition

53. A Class IV restoration (one bonded surface and four unbonded surfaces) with a C-factor of 0.25 is at low risk for adverse polymerization shrinkage effects. A Class I restoration with a C-factor of 5 (five bonded surfaces, one unbonded surface) is at much higher risk of bond disruption associated with polymerization shrinkage, particularly along the pulpal floor Internal stresses can be reduced in restorations subject to potentially high disruptive contraction forces (e.g., Class I preparations with a high C-factor) by using (1) “soft-start” polymerization instead of high-intensity light curing; (2) incremental additions to reduce the effects of polymerization shrinkage; and (3) a stress-breaking liner, such as a , flowable composite, or RMGI. Sturdevants art and science of operative dentistry 5 th edition

54. Class V Class IV Class III Class II Class I Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg

55. Recent Advances In Composite 1 )COMPOMER: The word “compomer” comes from comp osite & glass iono mer Polyacrylic-/ polycarboxylic acid modified composite. It is an attempt to take advantage of the desirable qualities of both materials: the fluoride release and ease of use of the glass ionomers and the superior material qualities and aesthetics of the composites. Sharma Y Recent Advances in Composite resins-an overview Asian J Biomed Pharmaceut sci.2023;13(99):175

56. Composition: Monomer: In addition to the various polymerizable monomers (e. g. UDMA) the material also contains dicarboxylic acids. Filler : The reactive fluoroaluminiumsilicate glasses The particle size of fillers in these products varies from 0.2 μm up to 10 μ m Sharma Y Recent Advances in Composite resins-an overview Asian J Biomed Pharmaceut sci.2023;13(99):175

57. 1.Fluoride release:caries development next to compomer restorations was lower than next to composite restorations 2. Compared to composite, compomers possess lower flexural modulus of elasticity, compressive strength, flexural strength, fracture toughness, and hardness. 3. The increased water absorption of the compomer compared to conventional composite results in hydrolysis of resin matrix and compromise the longetivity of the restoration. Properties Sharma Y Recent Advances in Composite resins-an overview Asian J Biomed Pharmaceut sci.2023;13(99):175

58. 2)GIOMER G lass ionomer + composites Giomer restoratives have the fluoride-release and recharge properties of glass-ionomer cements along with the excellent esthetics, easy polishability , and strength of resin composites It contains pre reacted glass ionomer fillers blended into a resin matrix These pre reacted glass ionomer filler forms an extensive hydrogel layer(primarily made of hydrated polyacid chains and ionic components such as calcium,aluminium and fluoride ions) which enhances fluoride uptake and release potentially outperforming other resin based materials in fluoride recharging ability. Sharma Y Recent Advances in Composite resins-an overview Asian J Biomed Pharmaceut sci.2023;13(99):175

59. 3) ORMOCERS: Organically Modified Ceramic Restorative material that contains: Inorganic-organic copolymers,i norganic silicated filler particles. Eg. Admira They are high molecular weighted relatively low viscosity cross linking molecules Ormocers have a reduced polymerization shrinkage compared to hybrid composites. Ormocers have decreased microleakage than conventional composites Sharma Y Recent Advances in Composite resins-an overview Asian J Biomed Pharmaceut sci.2023;13(99):175

60. 4 )FIBER-REINFORCED COMPOSITES: Generally, polyethylene fibers , carbon fibers, or glass fibers are incorporated into the composite. The fibers may be arranged in various configurations Have excellent strength Fibers – unidirectional (long, continuous & parallel) ,braided, woven fibers Type of fiber depends on how it is intended to be used, glass fibers for dental lab products Carbon fibers for posts (high tensile strength and modulus of elasticity matches that of dentin) Sharma Y Recent Advances in Composite resins-an overview Asian J Biomed Pharmaceut sci.2023;13(99):175

61. 5)Self healing/repairing materials: An epoxy system which contained resin filled microcapsules. If a crack occurs in the epoxy composite material, some of the microcapsules are destroyed near the crack and release the resin. The resin subsequently fills the crack and reacts with a Grubbs catalyst dispersed in the epoxy composite, resulting in polymerization of the resin and repair of the crack. Sharma Y Recent Advances in Composite resins-an overview Asian J Biomed Pharmaceut sci.2023;13(99):175

62. 6) Siloranes : Siloxane+oxirane The purpose of oxyrane configuration is to lessen polymerization shrinkage that usually occurs and the siloxane works in development of a hydrophobic structure. As silorane based composite polymerizes, ”ring opening” monomer connects by opening ,flattening and extending towards each other and the result is significantly less volumetric shrinkage. Sharma Y Recent Advances in Composite resins-an overview Asian J Biomed Pharmaceut sci.2023;13(99):175

63. INDICATIONS FOR COMPOSITE 1. Class I, II, III, IV,V, and VI restorations 2. Core buildups 3. Non carious lesions 4. Esthetic enhancement procedures Veneers Diastema closures Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg

64. 5. Cements (for indirect restorations) 6. Temporary restorations 7. Periodontal splinting 8. Patient allergic to metal Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg

65. CONTRAINDICATIONS 1.Difficult Moisture Control When isolation of operating field is difficult or accessibility problem is present for example in extremely posterior region. 2.Heavy Occlusal Stresses Where very high occlusal forces are present or in patients with bruxism are not good choice for composite restorations. 3.Class V Lesions Class V lesions where esthetics is not the prime concern. Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg

66. 4.High Caries Susceptibility and Poor Oral Hygiene Patients with high caries susceptibility and poor oral hygiene pose great risk of secondary caries and marginal discoloration . 5.Subgingival or Root Caries When preparation extends subgingivally or root surface, composites do not provide a favourable marginal seal. Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg

67. ADVANTAGES • Conservation of tooth structure: Since composite restoration requires minimal tooth preparation, maximum conservation of tooth structure is possible. • Esthetically acceptable • Composite resin can be used in combination with other materials , such as glass ionomer, to provide the benefits of both materials. • Low thermal conductivity: Composites have low thermal conductivity, thus no insulation base is required to protect underlying pulp. Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg

68. • Mechanical bonding to tooth structure: Restorations are bonded with enamel and dentin, hence show good retention. Composite restorations can bond directly to the tooth, making the tooth stronger than it would be with an amalgam filling. • Immediate finishing and polishing: Restoration with composite resins can be finished immediately after curing. Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg

69. • Extended working time: Extended working time of composites makes their manipulation easier. • Restoration can be completed in one dental visit . • No galvanism because composite resins do not contain any metals . Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg

70. DISADVANTAGES • Polymerization shrinkage: Because of polymerization shrinkage, gap formation on margins may occur, usually on root surfaces. This can result in secondary caries, staining and postoperative sensitivity • Time consuming: Composites restorations require good isolation and number of steps for their placement. Therefore composites restorations are more difficult to place and are time consuming. • Expensive: Composite is more expensive than amalgam. Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg

71. • Low wear resistance: Composites have low wear resistance than amalgam. • High Linear Coefficient of Thermal Expansion: High LCTE may result in marginal percolation around composite restorations. Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg

72. References Sturdevants art and science of operative dentistry 5 th edition Operative dentistry : Modern theory and practise ,Andrew L. Simonton, M.A Marzouk , R.D. Gross Phillips Science Of Dental Materials 12 th edition Sturdevants art and science of operative dentistry Second South Asia Edition Sharma Y Recent Advances in Composite resins-an overview Asian J Biomed Pharmaceut sci.2023;13(99):175 Basic Dental Materials second edition :John J Manappallil Textbook of Operative Dentistry 3 rd edition : Nisha Garg ,Amit Garg