1. Fundamentals of Operative Dentistry, 2 nd Ed., by Summitt JB, Robbins JW, and Schwartz RS. Copyright 2001 by Quintessence Publishing Co. Sturdevant’s Art & Science of Operative Dentistry, 5 th Ed., by Roberson TM, Heymann HO, and Swift EJ. Copyright 2006 by Mosby, Inc. with permission by Elsevier. Phillip’s Science of Dental Materials, 11 th Ed., by Anusavice KJ. Copyright 2003 by Saunders. Restorative Dental Materials, 13 th Ed., by Craig RM and Powers JM. Copyright 2012 by Mosby, Inc. with permission by Elsevier Composite Resin RSD 810 Fall 2015 by C. Rodriguez D.M.D.

2. Definition of Resin Composite (Composite Resin) A dispersed phase of filler particles distributed within a continuous matrix phase. In dentistry, composite resin is a reinforced polymer system used for restoring hard tissues (teeth).

3. OBJECTIVES: Introduce the development of composite resin in dentistry Complete an overview of the components of dental composite resin Discuss classifications of composite resins Understand the physical and mechanical properties which govern the use of dental composite resin Discuss clinical properties relevant to the use of composite resin

4. History of tooth colored restoratives Silicates developed first in 1878 by Fletcher – wonderful anticariogenicity, but early clinical failure due to solubility problems (acid-soluble glass and phosphoric acid), loss of translucency, surface crazing, and lack of mechanical properties. Used on anterior teeth for 60 years. Acrylic resins marketed in the 1940’s were unfilled low MW polymers (i.e. polymethyl methacrylate) which was not strong enough to support occlusal loads, had high polymerization shrinkage, high thermal expansion, and lack of abrasion resistance leading to early clinical failure due to dimensional instability Composite resins introduced in 1962 had better mechanical properties, lower thermal coefficient of expansion, lower dimensional change on setting, and higher resistance to wear, thereby improving clinical performance. Buonocore 1955 Phosphoric acid etch

5. Timeline for the Development of Dental Resin Composite 1962 CR

6. Composite Resins A) Components B) Classifications C) Physical properties D) Mechanical properties E) Clinical Properties

7. Resin Composite A) Components B) Classifications C) Physical properties D) Mechanical properties E) Clinical Properties

8. 1) Organic Polymer Matrix (Resin matrix) 2) Resin Matrix Diluent 3) Inorganic Filler particles 4) Coupling Agent 5) Initiator 6) UV Absorbers 7) Inhibitors 8) Pigments A) Components

9. 1)Organic Polymer Matrix continuous organic polymer matrix commonly referred to as an “oligomer” BIS-GMA (bisphenol-A-glycidyl methacrylate) UDMA (Urethane Dimethacrylate) both Monomeric building blocks

10. Dimethacrylate monomers The double bonds at each end of these molecules undergo addition polymerization by free-radical initiation. This results in a greater molecular weight and increased strength & rigidity. 1)

11. What makes up dental composite? 2) Resin Matrix Diluent monomer of lower MW added to reduce the overall viscosity of the oligomer example is TEGDMA (triethylene glycol dimethacylate) ordinary composite consists of resin matrix 75% BIS-GMA and 25% TEGDMA. Its viscosity could be said to be that of honey. By increasing the diluent:matrix ratio (50% BIS-GMA & 50% TEGDMA ), viscosity decreases to that of thin syrup. Why is this clinically relevant? It allows for increased filler loading

12. 3) Inorganic Filler Particles ( content measured by weight) Types: glass quartz, barium silicate, colloidal silica, zirconium silicate (radiopacity is bonus) Functions to reinforce matrix, provide translucency, control volumetric shrinkage

13. 3) Inorganic Filler Particles affect hardness compressive strength (reinforces matrix) modulus of elasticity (MOE=stiffness) linear coefficient of thermal expansion (LCTE) improves esthetics (provides translucency) decreases affect of polymerization shrinkage

14. 3) Inorganic Filler Particles The greater the amount of filler, the less resin matrix there is available, so better physical properties result. Filler loading range for the typical composite 30-70% by volume 50-85% by weight (Typically makes up the majority)

15. as filler surface area, fluidity, viscosity Hardness Compressive strength MOE LCTE Poly shrinkage 3)

16. It is advantageous to have a distribution of filler diameters so that smaller particles fit into the spaces between larger particles and provide more efficient packing. 3)

17. Composite resins are classified using three criteria relating to filler particles: a) Size of particle macrofillers 10-100 µm midifillers 1-10 µm minifillers.1-1 µm microfillers.01-.1 µm nanofillers.001-.01 µm b) Shape of the particle c) Distribution of the filler (or composition of the inorganic filler) 3)

18. 1) Resin Matrix 2) Resin Matrix Diluent 3) Fillers (inorganic) 4) Coupling Agent 5) Initiator 6) UV Absorbers 7) Inhibitors 8) Pigments A) Components

19. 4 ) Coupling Agent Applied to inorganic particles to surface treat fillers prior to mixing with unreacted monomer. chemically bonds filler particle (inorganic) to resin matrix (organic) The most common coupling agent is an organic silicon compound called silane, a saturated hydro silicon with chemical formula SiH4.

20. As difunctional molecules, silanes have one end bonding to hydroxyl groups on silica particles (inorganic), and the other end copolymerizing with double bonds on the monomers in the matrix phase (organic). 4)

21. Silane coupling agents are capable of improving the strength and wear resistance of the composite, thereby also preventing microbes from adhering to a roughened worn surface. 4)

22. A)Components 1) Resin Matrix 2) Resin Matrix Diluent 3) Fillers (inorganic) 4) Coupling Agent 5) Initiator 6) UV Absorbers 7) Inhibitors 8) Pigments

23. 5) Initiator (activation method is clinically relevant) a) Chemically activated – benzoyl peroxide (initiator) reacts with a tertiary amine (activator), forming free radicals, this starts the polymerization process. b) Light activated – camphorquinone (photo initiator) reacts with DEAEMA (activator) forming free radicals, this starts the polymerization process camphorquinone is sensitive to 400-500 nm (peak is 468 nm). Makes up 0.1%-1.0% of the monomer mixture. degree of double bond conversion 50-70% blue light replaced (earlier) UV-light activator systems c) Dual Cured- use a combination of chemical and light activation to carry out the polymerization reaction.

24. a) Chemical Activation - (Auto-cure) Two pastes Paste 1: initiator Paste 2: accelerator(=activator) Sets upon mixing Uniform cure throughout 5)

25. b) Light Activation One paste Initiator activated by light What did we say was the peak wavelength in nm? Flexible working time Is there a problem with ambient light? Technique sensitive uniformity of cure 5)

26. 460-480nm 5) 468nm

27. QTH Quartz tungsten halogen LED Light curing can be accomplished with QTH, PAC (plasma arc), lasers, and LED. Each unit attempts to maximize light output in the absorption range of the photoinitiator(470nm for camphoroquinone). Unabsorbed light is converted principally into heat. Typically 20 sec. is required for cure, however plasma arc and laser lights can reduce curing times but generate more heat. 5)

28. A)Components 1) Resin Matrix 2) Resin Matrix Diluent 3) Fillers (inorganic) 4) Coupling Agent 5) Initiator 6) UV Absorbers 7) Inhibitors 8) Pigments

29. A)Components 6) UV Absorbers Minimizes color changes caused by oxidation i.e.. benzophenone 7) Inhibitors extend shelf life by retarding autopolymerization during storage i.e. hydroquinone 8) Pigments: inorganic oxides (commonly of iron) provide shading i.e. titanium dioxide, aluminum oxide Darker and more opaque shades require thinner increments when placing than lighter translucent shades.

30. Since 2008 a variety of other methacrylate monomers have been used for controlling the volumetric shrinkage and polymerization stress of composites. By increasing the distance between the methacrylate groups a lower cross-link density or increased stiffness of the monomers occurs. The bonding agents used with these are also prepared from similar organic monomers so they are compatible. Bottom line: follow manufacturers instructions

31. A new monomer system called silorane has been developed to reduce shrinkage and internal stress build-up resulting from polymerization. Special initiator systems are required for the polymerization of these. Specific adhesive system has to be used for bonding these materials during clinical placement. Bottom line: follow manufacturers instructions

32. Composite Resins A) Components B) Classifications C) Physical properties D) Mechanical properties E) Clinical Properties

33. Composite resins are classified using three criteria relating to filler particles: a) particle size macrofillers 10-100 µm midifillers 1-10 µm minifillers.1-1 µm microfillers.01-.1 µm nanofillers.001-.01 µm (100,000 times smaller) ( 1 nm =.001um) b) shape of the particle c) distribution of the filler (or composition of the inorganic filler) B) Classifications

34. MACROFILL COMPOSITES-75-80%filler by wt., relatively large sized particles (20-30 microns), rough surface that wears quickly, opaque. Not much application today. MICROFILL COMPOSITES-colloidal silica particles of very small size. Not as heavily filled(35- 60% by wt.,) but highly polishable. Very wear resistant but relatively poor wear in functional areas. HYBRID COMPOSITES-high filler load (77-84% by wt.), a mixture of small (2-4 microns) and very small ( 5%-15%, 0.04-0.2 microns)particles. Good handling, relatively smooth surface but become rough with time, good wear resistance and mechanical properties, suitable for stress-bearing applications. FLOWABLE COMPOSITES- lower filler content (42-53% by volume), lower strength and wear resistance, high polymerization shrinkage, low MOE, easy to use, favorable wettability.

35. B)Classifications: NANOFILL COMPOSITES-extremely small particles (1-100nm), high filler content, good physical properties, esthetics, polishability. These are heterogeneous, with pre-cured and uncured particles. Nano-clusters are made of lightly sintered nanomeric oxides which form clusters. Clusters can have a wide range of sizes from 100nm to sub-micron level. Has the mechanical strength of a microhybrid but retains smoothness like a microfill because nanoclusters shear at a rate similar to the surrounding matrix during abrasion. As these particles are far smaller than the wavelength of light, long wavelength light passes directly through and materials are highly translucent. (this provides the ability to formulate a wide range of shades and opacities). Wear resistance after 3-5 years similar to enamel. ( 1 nm =.001um) NANOHYBRID COMPOSITE-nano-sized particles mixed with microhybrids. Gradually become dull after a few years because smoothness and wear is determined by the size of the largest filler particles.

36. B)

37. True Nano-filled Composite.001-.02 µm B)

38. B) Classifications It is advantageous to have a distribution of filler diameters so that smaller particles fit into the spaces between larger particles and provide more efficient packing.

39. Some of the small (20 nanometers) spherical filler particles which make up nano filled materials are sintered and form nanoclusers. These are then silanated and mixed with the other nanoparticles. B)

40. Nano Composite B)

41. Why Filtek Supreme Ultra Universal Restorative at UKCD? Contains a cluster of nanometer-sized particles which shear at a rate similar to the wear of the surrounding resin matrix during abrasion, making it an ideal posterior restorative. It maintains favorable handling characteristics, polishability, and esthetics desirable for an anterior material. B)

42. Nano Composite by 3M ESPE Filtek Supreme Ultra B)

43. Composite Resins A) Components B) Classifications C) Physical properties D) Mechanical properties E) Clinical Properties

44. C) Physical Properties- Polymerization Reaction Stages: (“Free-radical addition polymerization of the corresponding methacrylate monomers”) Initiation- peroxide initiator and amine accelerator (chemical cure), or by visible blue light (light cure) Propagation- rapid addition of monomer molecules to the active center to provide the growing polymer chain Termination- occurs in a variety of ways

45. C)Physical Properties – Working and Setting Times Light-cured composites: Polymerization varies by the distance of the light from the restoration and the duration of light exposure, initiation is controlled by operator, so working time may be long. 75% of polymerization occurs within the first 10 min. (curing reaction continues for 24 hrs.) not all carbon double bonds react and 25% of composite remains unreacted (optimum properties occur at 24 hrs.) within 60-90 secs. after being exposed to ambient light, composite loses it’s ability to flow readily. This is clinically relevant.

46. C)Physical Properties – Working and Setting Times Chemical-cured composites: setting time 3-5 minutes, working time is slightly less. shorter setting times can be accomplished by varying the concentration of peroxide initiator and amine accelerator

47. C)Physical Properties – Polymerization Shrinkage Polymerization shrinkage is a direct function of the amount of resin matrix and diluent. The more resin, the greater the shrinkage. Volumetric shrinkage during polymerization can be as great as 7% and this shrinkage can create polymerization stresses as high as 13 MPa which severely strains the interfacial bond between the tooth and composite (average is 3% PS at 24 hrs.) What does this result in? very small gap allowing marginal leakage of saliva, or friable enamel fracture (white line) How can you overcome this problem? one method is incremental placement of composite

48. Fig 10-7a Polymerization shrinkage can cause crazing in the enamel or fractures within the resin composite. Fig 10-7b Craze lines are evident in the lingual cusp of the maxillary right second premolar bonded to a very large Class 2 resin composite restoration. C)

49. Marginal leakage of saliva and resultant recurrent caries and marginal staining… Careful technique and proper clinical assessment can minimize these factors. C)

50. C.Physical Properties – Polymerization Shrinkage Protecting the interfacial bonding : “Stress-breaking liners” such as GI or flowable composites which possess a low elastic modulus Why glass ionomers? 1) true adhesion to tooth structure 2) coefficient of thermal expansion same as tooth structure 3) low setting shrinkage, so they don’t stress the bond Why “flowable composites”? “resin” component makes them more “fluid”

51. C)Physical Properties – Thermal Affects Composite resin has 2-6X greater coefficient of thermal expansion than tooth structure dentin (8.3 ppm/ o K) vs enamel (11.4 ppm/ o K) vs composite (14-50 ppm/ o K) Phillips, Table 3-2, pg. 55 Thermal changes are cyclic, leading to material fatigue and early interfacial bond failure or marginal gap formation. This can lead to “percolation” of oral fluids into the tooth.

52. C)Physical Properties – Thermal Affects Thermal conductivity of composites with fine particles is greater than that of composites with microfine particles because of the higher conductivity of the inorganic fillers compared with the polymer matrix. (plastic is a better insulator than glass) For highly transient temperatures (eating and drinking) composites do not change temperature as fast as tooth structure and this difference does not create a clinical problem.(do not chew ice after drinking hot coffee)

53. C)P hysical Properties – Water Sorption and Solubility Microfill composites, due to higher resin content, have higher values for sorption (1.2-2.2mg/cm3) than small particle composites (.3-.6mg/cm3). Therefore they exhibit more expansion. Inadequate polymerization with light-cured materials can also result in greater sorption.

54. Composite Resins A) Components B) Classifications C) Physical properties D) Mechanical properties E) Clinical Properties

55. D)Mechanical properties Increased filler content correlates to increased fracture resistance. Wear of posterior composites is greatest at the opposing tooth contact area where stresses are highest. It is contraindicated to place the margin of restoration on a “centric stop”. The centric stop is the contact point of two opposing teeth when the dentition is in “maximum Intercuspation” position.

56. Composite Resins A) Components B) Classifications C) Physical properties D) Mechanical properties E) Clinical Properties

57. E)Clinical Properties: 1.Depth of Cure 2.Radiopacity 3.Wear rates 4.Biocompatibility

58. E)Clinical Properties: 1)Depth of cure: light intensity decreases as distance increases (1.0mm is optimum) light scatters when it travels through filler and intensity is reduced (the smaller the particle, the more scatter). depth of penetration depends on wavelength of light, its irradiance, and the scattering that takes place microfilled with smaller and more particles scatter more light than microhybrids so longer exposure times are needed. as shade darkens and opacity increases depth of cure is less requiring longer exposure times but more importantly smaller increments (>20sec., and <2-2.5mm)

59. Fig.18-76 Light intensity influences on the polymerization zone: Varying intensity with width and depth affects: 1) the degree of conversion of monomer to polymer 2) shape of cure 3) depth of cure Polymers in Dentistry: Dental Composite Resin by Caurelia Univ. of York Macromolecule Project YouTube

60. Proximity of light to the surface affects depth of penetration of light into the surface “Depth of cure” is the boundary between the somewhat cured and the uncured resin, and so does not take into consideration degree of conversion—so the effective cure is much less than the publicized “depth of cure”. This is clinically significant.

61. E)Clinical Properties: 2)Radiopacity: Even at the highest volume fraction of filler the amount of radiopacity is less than that exhibited by a metallic restorative like amalgam. Some microhybrids incorporate finely divided heavy-metal glass particles. In the nanofills, nanomeric zirconia (5-7nm) is used.

62. Amalgam Restorations Composite Restorations Base Material Note the relative radiopacity/radiolucency of different dental materials

63. Clinical Properties: 3)Wear Rates: Clinical studies have shown composite to be ideal for anterior restorations in which esthetics is essential and occlusal forces are low. Marginal degradation is evident and is attributed to improper technique. Clinical studies show nanocomposites have excellent wear resistance, similar to that of natural human enamel in 3 and 5- year clinical studies.

64. E)Clinical Properties: 4)Biocompatibility: Nearly all major components are cytotoxic in vitro if bulk monomer Cured composite liability depends upon release of uncured monomer Amount of release depends upon type of material and efficiency of cure Effects of low-dose, long-term exposures of cells to resin components are not generally known. RDT is of 0.5mm is important in vital tooth therapy, and do not use as direct pulp-cap Components are known allergens, but there is no documentation of frequency in the general population. Estrogenicity from cured commercial composites has not been demonstrated. Early studies have been discredited.

65. Biomimetism: The Inspiration Historically it was the study of biomineralization that focused the attention of materials scientists to the possibilities of hybrid structures which mix organic and inorganic components at the molecular scale. Mollusk shells, bones, wood, (teeth), most materials made by living organisms closely associate inorganic and organic components. Biological macromolecules form an intimate mix or composite of proteins and mineral phases at all levels of composition, starting from the nanoscale up to the macroscopic scale. For instance nacre is a kind of sandwich material made of layers of calcium carbonate crystal alternating with organic layers of proteins. In bone, collagen protein fibers form the matrix phase, which is reinforced with small rod-like crystals of hydroxyapatite about 5nm by 5nm by 50nm in size. Hydroxyapatite is an inorganic, calcium phosphate-based crystal with the formula Ca10(HPO4)6(OH)2. Here nature gives scientists a model of a reinforcing phase of small dimensions in relation to the matrix. History of Recent Science and Technology by Tim Palucka and Bernadette Bensaude-Vincent: Composite Overview 2001 The Dibner Institue for the History of Science and Technology