Composite resins PART 1

Descriptive presentation on composite resin

1. Composite Resins (Part I- Basics) Presented by – Shivani M. Raghuwanshi 1 GUIDED BY-Dr Suvarna patil -Dr Ashish Medha -Dr Sharanu srivastav -Dr.Girish umashetty -Dr.Snehal savagave -Dr.Rutuja chopade -Dr.Priyatam karade -Dr.Anil bhaghat -Dr.Ravindra jadhav

2. CONTENTS Introduction History Defination Indications /Contraindications Composition Classification Curing Curing Lamps Properties Types of cavity preparations of composites Incremental placement techniques Composite restorations instruments Conclusion 2

3. Introduction 3 Resin based composites/filled resins Aestheticaly pleasing Less enamel removal Insoluble, easy to manipulate

4. HISTORY 4

5. 1956 - Bowen resin 1960 -Traditional/ Macrofilled composites 1970 - Microfilled composites 1980 - Posterior Composites 1990 - Hybrid, Flowable, Packable composites 2000 - Nanofilled Composites 5

6. DEFINATION A highly cross linked polymeric material reinforced by a dispersion of amorphous silica, glass, crystalline or organic resin filler particles bonded to the matrix by a coupling agent. [Skinners] ADA Sp. No. – 27 ISO Sp. No. - 4049 6 In material and science the word composite refers to a solid formed from two or more distinct phases that have been combined to produce properties superior or intermediate to those of individual constituents. [Studervants]

7. Indications 7 Class I,II,III,IV,V,VI restorations Pit and Fissure sealants Splinting of mobile tooth Fibre reinforced Veneers Core build up Esthetic enhancement procedures -Repairing of old composite restorations -Temporary restorations -Composite inlays -Cements

8. Contraindications Isolation Poor oral hygiene High caries index Bruxism Subgingival area/root surface area Operator abilities 8

9. 9 Esthetics Conservative cavity preps Reparability Low thermal conductivity Technique sensitive COTE Proper contact & contour Polymerization shrinkage Non antimicrobial

10. Classification SKINNER’S (10 th ed) Traditional composites /Macrofilled/Conventional – 8 - 12  m Small particle composite – 1-5  m Microfilled composite – 0.04 – 0.4  m Hybrid composite – 0.6 – 1  m 10

11. STUDERVANT ’S [Based on filler particle size] Megafill – large particles Macrofill -10-100um Midifill -1-10um Minifill -0.1-1um Microfill -0.01-0.1um Nanofill – 0.001-0.01um 11

12. MARZOUK’S [ GENERATIONS OF COMPOSITES ] 1 st generation composite: consists of macroceramic fillers in resin matrix. 2 nd generation composites : consists of colloidal and microceramic phases 3 rd generation composite : hybrid combination of macro and microceramic fillers.(75:25) 12 4 th generation composite : hybrid and heat cured irregularly shaped 5 th generation composite : hybrid heat cured spherical shaped 6 th generation composite : hybrid with agglomerates of sintered macroceramics

13. Based on type of cure. Chemical cure UV light cure Visible light cure Dual cure 13 Based on resin matrix used Bis-GMA based UDMA based Silorane based Based on consistency Light body (flowable composites) Medium body (microfills, macrofills, midifills, hybrid) Heavy body (packable composites)

14. Composition 14

15. Resin matrix Principle monomers - Bis-GMA , Urethane dimethacrylate Limitations - Highly viscous - Polymerization shrinkage - does not adhere to tooth structure Diluent monomers – TEGDMA, MMA, EGDMA which controls the viscosity 15 FILLER RESIN MATRIX COUPLING AGENT

16. Fillers Ground quartz, colloidal silica,barium , glass/ceramics containing heavy metals, fluoride releasing fillers YbF3. ADVANTAGES: Increases strength , Hardness, Abrasion resistance Increases viscosity & Radiopacities Decreases polymerization shrinkage Decreases water sorption Improves clinical handling Reduces thermal expansion and contraction 16

17. Filler particles are most commonly produced by grinding or milling quartz or glasses to produce particles ranging in size from 0.1-100 um. Smaller silica particles of size ranging from 0.06-1um are obtained by a pyrolytic or precipitation process. In these processes a SiCl4 is burned in an O2 and H2 atmosphere to form macromolecule chains of SiO2. 17

18. Coupling agents The filler particles are not soluble in resin matrix as the resins are hydrophobic and fillers are hydrophillic . Hence, they do not bond. This bond is achieved by coating filler particles with coupling agent. Ex: Zirconates , Titanates , Organosilanes ( gamma- methacryloxy propyl trimethoxy silane ) 18 Transfer of stresses from polymer matrix to filler particles They prevent water from penetrating the resin filler interface

19. Activator/Initiator system 19 Chemically cured Light cured 2 paste system Base paste- Benzoyl peroxide Catalyst paste – N,N-dimethyl-p-Toluidine Earlier UV light activated Visible light activated Camphoroquinone photoinitiator (Absorbs blue light) Activator- Dimethyl aminoethyl methacrylate

20. COMPARISON CHEMICAL LIGHT 20 Polymerization is central Curing is in one phase Sets within 45 sec. No control over working time Shrinkage towards centre of bulk Air may get incorporated More wastage of material Not properly finished Peripheral Is in increments Sets only after light activation Working time under control Shrinkage towards light source Less chance of air entrapment Less wastage Better finish

21. Inhibitors – butylated hydroxytoluene 0.01% To extend storage life They reacts with free radicals thereby inhibiting polymerization process. Optical Modifiers To match the appearance of teeth shading is achieved by adding different pigments like Titanium oxide, aluminium oxide in minute amounts as effective opacifiers. 21

22. History of light curing UV curing Quartz Tungsten Halogen Plasma arc LASER LIGHT emitting diode-1 st ,2 nd & 3 rd generations First curing light was NUVA light developed in 1970’s by Caulk company ( Dentsply ) which uses U.V light to cure composite resins. Disadvantages : depth of cure is short, harmful effect on cornea 22

23. 23

24. QUARTZ TUNGSTEN HALOGEN 24 Used in 1990. Consists of quartz bulb with tungsten filament in a in halogen environment. Electric current passes through an extremely thin tungsten filament which at about 3000 C produces Electro Magnetic radiation in form of visible light. It provides a blue light of about 400-500 nm with an intensity of 400-600 mW /cm 2

25. Drawbacks : Large amount of heat generated hence cooling fans are installed Increased weight of machine It should be plugged into a power source not cordless Short life span of halogen bulbs (40-100 hrs ) 25

26. PLASMA ARC CURING (PAC) Two tungsten electrodes held seperated by small distance encased in high – pressure envelope of xenon gas. When high voltage is applied across the electrodes, a spark forms which produces tremendous amount of EM radiation. It uses xenon gas that is ionized to produce plasma arc. Light is filtered to remove all WL except blue light approx (400-500 nm). 26 Drawbacks : Expensive High temperature development Requires in built filters to produce narrow spectrum

27. ARGON LASER 27 Laser photons travel in phase & are collimated such that they travel in same direction. This lamp has highest intensity It emits light in single WL of 490 nm Do not require filters Drawbacks: Large in size & heavy Most expensive Risk of other tissues being irradiated

28. LIGHT EMITTING DIODE It is a semi-conductor light source which emits light when current flows through it. This light uses gallium nitride based semiconductor for blue light emission. A voltage is applied across the junction of two doped semiconductors (n-doped & p-doped) resulting in emission of light in a specific W.L It emits light only in the blue part does not require filters. They require less power than others & do not generate heat. Emits light of WL 440-480 nm. 28

29. Generations of LED 1 st generation : It has low power output Low irradiance < 100-280 mW /cm 2 compared to QTH about 400mW/cm 2 Increase exposure time Easy to handle with less heat generation without using fans Has narrow spectral range suitable for camphoroquinone 29

30. 2 nd generation It has more powerful diodes than in first generation It uses LED chip design raising output of LED to QTH units Expensive High heat generation so external fans required 3 rd generation In order to enable curing other restorative material not only use CQ but use other initiators like (CQ+ tertiary amine) , 1-phenyl propane , Trimethylbenzyl - diphenyl phosphine oxides. These other initiators need UV wavelength to activate them. 30

31. Why is it necessary to measure intensity of curing lights? 31 Digi Rate LM- 100 Analog radiometer It’s a analog radiometer that can instantly measure light intensity of both LED & halogen curing lights Light weight & portable Automatically snoozes after 30 sec The reduction in the light intensity of the device can affect the success rate of the restorative methods via reducing the degree of convergence of composites, which leads to an increase in microleakage and recurrent caries. If the light output intensity decreases, it will adversely influence the clinical and cosmetic performance. Light intensity of < 300 mW/cm2 was considered unacceptable and a device with a light intensity of < 200 mW/cm2 was regarded unusable J Clin Exp Dent. 2018 Jun; 10(6): e555–e560.

32. LIGHT CURING VARIABLES The minimum output of curing lights should not be less than 300 – 400 mW/cm2. Light curing (time) requires a minimum 20 secs for adequate curing . The time can be shortened by- Increasing the conc. of photoinitiator or Increasing the intensity of the output Tip should be kept within 1-2 mm of composite to be effective. 32

33. 33 The blue light forms free radicals in the eye In the retina, these free radicals react with the water-content of cells, causing peroxides to form in the visual cells These peroxides are reactive and denature the delicate photoreceptors of the eye OCULAR HAZARDS OF CURING LIGHTS: Blue light is 33 times more damaging to the photoreceptors of the retina. As exposure duration increased, the burns became more severe. ("SOLAR RETINITIS“) The Saudi Dental Journal Volume 31, Issue 2  April 2019, Pages 173-180

34. This blue light hazard to the retina is greatest at 440nm. High levels of blue light cause immediate & irreversible retinal burning while low levels cause retinal aging and degeneration . So , it is recommended to use blue blocking orange filter glasses or shields for optical safety which reduces the risks of exposure of blue light between WL 420-500 nm

35. EYE PROTECTION The best eye protection is to completely avoid looking at the curing light source. The exposures of under 2 minutes to visible light-curing units (total daily dose from 25 cm) may be safe. Cover the curing field with the reflective side of a mouth mirror. This prevents excess blue light from reflecting back against the restorative and improves curing. 35

36. TYPES OF COMPOSITES Traditional composites Microfilled composites Small particle sized composites Hybrid composites Nanofilled composites 36

37. Macrofilled / Conventional/ Traditional composites. Fillers : Finely ground silica or quartz is used Filler particle size : 8-12um Filler loading : 70-80% wt Advantages – high strength & hardness - less water sorption Disadvantages – rough surface , tendency to discolour, polishing is difficult. INDCATIONS - Class II, IV restorations. 37

38. Microfilled composites. Smallest filler particle size: 0.04-0.4% Colloidal silica is used as filler It has lowest filler content of 50% Advantages - smoother surface, excellent esthetics Disadvantage - Lower strength and hardness -Highest coefficient of thermal expansion - High water sorption - Low modulus of elasticity INDICATIONS – Aesthetic restoration for anterior teeth - Restoring sub gingival areas - Carious lesions on smooth surface (class IV) 38

39. Small particle composite. Filler particle size : 1-5um It achieves surface smoothness of microfilled & physical and mechanical properties of conventional composites Advantages : Highest compressive strength increased filler loading , elastic modulus good surface smoothness Disadvantage : Non- esthetic INDICATIONS - High stress & Abrasion prone areas 39

40. Hybrid composites Fillers : Colloidal silica and Ground particles of glass containing heavy metals Filler particle size : o.6-1um Filler loading : 70 – 80 wt To obtain even better surface smoothness than small particle composites Advantages -smooth finish , better esthetics and physical properties Disadvantage – increased roughness with time INDICATIONS – Anterior restorations (class IV , III) - Non stress bearing areas in posterior teeth 40

41. Nanofilled composites -These particles are extremely small (0.005- 0.01um) and virtually invisible. -Their particle size is below range of wavelength of light and thus they do not absorb or scatter visible light. -Nanofiller offers means of incorporating radiopacifiers that do not interfere with esthetic properties 41

42. PHYSICAL PROPERTIES Polymerization shrinkage This occurs when carbon double bonds in the monomers are converted to single bonds during curing. Conversion of these monomers results in decrease in the distance between the molecules creating gap. It does not cause significant problems when preparations are having all enamel margins but when extended onto root surface cause gap formation at the junction of composite and root surface. 42

43. V shaped gap occurs , Force of polymerization of composite > Bond strength of dentin & root V shaped gap composed of composite on restoration side & hybridized dentin on root side. Placing RMGI first in gingival portion followed by composite may reduce microleakage & gap formation . 43

44. Methods to reduce polymerization shrinkage Increasing filler content Using better bonding agents Incremental placement. “Soft start “ polymerization (instead of high intensity light curing) Use stress breaking liners ( flowable composite, RMGIC) 44

45. Configuration factor C factor = Bonded walls Unbonded walls During curing, shrinkage leaves the bonded surfaces in a state of stress, while the free surfaces relax some of the stresses by contracting inward toward the bulk of the material. 45

46. WATER SORPTION “Water absorbed by the material over time per unit of surface area or volume” 46 Filler particles adsorb water Swelling of matrix & debonding of fillers Expansion of restoration

47. Traditional - 0.5-0.7 mg/cm2 Small particle - 0.5-0.6 mg/cm2 Hybrid - 0.5-0.7 mg/cm2 Microfilled - 1.4-1.7 mg/cm2 The quality and stability of the silane coupling agent are important in minimizing the deterioration of the bond between the filler and polymer and the amount of water sorption. 47

48. Oxygen inhibition layer 48 O2 reacts with free radicals forming unreactive peroxy radicals Terminate polymerization Resulting in poorly polymerized resin rich surface layer Therefore, composites have to be finished & polished to remove this O2 inhibited layer Also can be reduced by increasing photo initiator concentration, thus increasing radical conc. & sufficient free radicals for initiation.

49. Degree of conversion It is the measure of the percentage of carbon = carbon bonds that have been converted to single bond to form a polymeric resin. At the end of polymerization reaction not all monomers take part in the reaction & get converted to polymer. Degree of conversion of bis-GMA based composites is typically between 50-60%. Reduced degree of conversion may lower the mechanical properties of composites. 49

50. 50 65% would be considered a good degree of conversion. A curing light may only produce a 55% degree of cure at 1 mm into a composite and even less at greater depths. Clinically, it is impossible to distinguish differences in the degree of cure.

51. Coefficient of thermal expansion To prevent development of stresses due to expansion & contraction on exposure to varying temperatures , COTE should be close to tooth structure. COTE of Resin matrix is much higher than that of enamel & dentin . Hence by incorporation of fillers it is reduced. COTE of composites ranges from 25-38 ×10̄-6/°C. 51

52. To evaluate integrity of composite resin restoration radiographically , resin needs to be radiopaque. It is provided by fillers such as glass ceramics containing heavy metals- barium, strontium, zirconium. Acc. ADA sp. No. 27 composite resins have radiopacity equivalent to 1mm of Aluminium. 52 Radiopacity

53. Working and Setting time For chemically activated composites , working time should be no less than 90 sec. Since, it is exothermic reaction it is from start of mix till the temperature rises. Setting time ranges from 3 mins to 5 mins. For light cured composites , although it hardens on exposure of light but curing reaction continues for 24 hrs. About 50% of composite material is fully polymerized within 10 mins of application of light source. 53

54. Strength Compressive strength of composites ranges from 200-300 MPa. Nanocomposites have higher compressive strength of about 450 MPa. Hardness It is directly related to volume of fillers present. Hence, microhardness of hybrid composites is greater than microfilled composites 54

55. Biocompatibility The major components of composites (Bis-GMA, TEGDMA, and UDMA, among others) have been found cytotoxic. EGDMA and TEDGMA promote the proliferation of cariogenic micro‑organisms such as Lactobacillus acidophilus and Streptococcus sobrinus . s. In addition, bacterial exotoxins have noxious effects on pulp cells after diffusion throughout dentin tubules. Bisphenol A - Shown to cause reproductive anomalies (in developmental stages of fetal life). Molecular mechanisms involve glutathione depletion and reactive oxygen species (ROS) production as key factors leading to pulp or gingival cell apoptosis. 55 TEGDMA is hydrophilic and interferes with oral tissues. The compound can penetrate membranes and reacts with intracellular molecules. Specifically, glutathione–TEGDMA adducts are formed a mechanism reducing cellular detoxifying potency.[38] A current study[41] has demonstrated that TEGDMA induces significant intracellular glutathione level (GSH) depletion and causes severe cytotoxicity in cultures of human periodontal ligament fibroblasts (HPLF). Glutathione, even in high concentrations had no protective effect against TEGDMA‑induced cytotoxicity. Therefore, the investigated hypothesis that exogenous GSH may prevent or reduce TEGDMA‑associated cytotoxicity in HPLF has to be rejected. [Review article : Release & Toxicity of dental resin composite Sep-Dec 2012 / Vol-19 / Issue-3]

56. Types of cavity preparation for composites restorations. Conventional design These are typical amalgam cavity preparation designs with uniform depth, flat floors, butt joint and retention grooves in dentin. Indications: Preparations located on root surfaces Moderate to large class I or class ll restorations 56

57. Bevelled conventional Indicated for replacing an existing old non-adhesive restoration such as silicate or acrylic resin with composite resin. Prepared using no. ½, 1 or 2 round diamond point. Here instead of butt joint cavosurface margin a bevel is incorporated using flame shaped diamond point producing cavosurface angle of 45 degrees. The bevel may be 0.25-0.5 mm in width. Class lll , lV 57

58. Modified Scooped out cavity preparation Indicated in small to moderate carious lesions & is made as conservative as possible. The depth is usually limited to 0.2 mm into dentin. 58

59. Box only This design is indicated when only proximal surface is faulty with no lesions present on occlusal surface. Facial / lingual slot Design for restoring proximal lesions on posterior teeth. 59

60. 1.Tofflemire with matrix band 60 Types of matrices used for class II composite restorations 2. Clear polyester matrices

61. 61 3. Precontoured sectional matrices Palodent Bitine Composi –Tight rings Composi – Tight 3D rings V3 rings (Triodent)

62. 62 It was introduced mainly to restore Class I cavities and erosively damaged teeth. This technique is indicated when the preoperative anatomy of the tooth is intact and not lost due to the carious lesion.

63. COMPOSITE RESTORATION INSTRUMENTS Titanium Coated Increases the surface hardness of instrument tips Reduce abrasion and eliminate “pull - back” when manipulating composite materials for a smoother, more accurate restoration in less time. 63

64. Micro-Curve Paddle #26T Mirror image blades are 6 mm long and 1.5 mm wide. Ideal for small pit and fissure or minor anterior restorations. 64 Spatula/Paddle #9T Combines a thin, flexible placement spatula that is 18 mm long and 5.5mm wide with a paddle set at an opposing angle that is 10 mm long and 1.8 mm wide

65. Double Paddle #7T Flared blade paddles set at opposing angles that are 11 mm long and 1.8 mm wide 65 Double Paddle #37T Identical parallel blade paddles set at opposing angles that are 11 mm long and 1.5 mm wide.

66. Composite Instrument #52T Designed for smaller posterior composite restorations. This instrument combines a 0° elliptical paddle that is 7mm long/1.8mm wide with a rounded burnisher that is 1.4mm in diameter. 66 Composite Instrument #53T This paddle/anatomical burnisher combination is designed for Class II posterior restorations that require a fine artistic touch. The 90° paddle is elliptical in shape, quite thin and only 7mm long and 1.8mm wide. It is combined with a medium size acorn burnisher

67. COMPOROLLER 67 It is an innovative composite modelling instrument designed to provide complete control when layering and contouring a direct composite restoration into its final form. It is a single instrument with roller tips therefore as the roller moves it will go on modelling resin quickly minimizing finishing polishing time & giving smooth contour It’s a set of 7 different formats that suits each procedure & are disposible. [cylindrical , conical , disc tip , point, oval, spatula]

68. COMPOSITE PLACEMENT TECHNIQUE 1.Horizontal layering technique 2.Vertical layering technique 3.Oblique layering technique 4.Centripetal layering technique 5.Split increment horizontal layering technique 6.Successive cusp buildup technique 68

69. INCREMENTAL LAYERING Used in medium to large posterior composite restorations to avoid the limitation of depth of cure Composite layers < 2mm thickness To attain good marginal quality Ensures complete polymerization of composite 69

70. Horizontal layering technique The horizontal placement technique utilizes composite resin layers, each <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. 70

71. 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 71

72. Oblique layering technique The oblique technique is accomplished by placing a series of wedge-shaped composite increments. Each increment is photocured 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. 72

73. Centripetal buildup technique This technique employs metal matrix bands and wooden wedges eliminating the need for transparent matrix bands, which may not provide firm contact areas and are cumbersome to use for many practitioners. Even if such gap develops, the next consecutive layer which is condensed toward the gingival floor is likely to fill gap since the continuity of space created is not occluded. 73 Thin layer (0.5mm) applied on gingival floor to occlusal marginal ridge of proximal box packed proximally in contact with inner surface of matrix band. Hence, cut down cervical gap.

74. Split-increment horizontal layering technique Each horizontal increment was split, before curing, into four triangle-shaped portion, with each portion placed against only one cavity wall and part of the floor one diagonal cut was filled completely with dentin shade composite and photocured . At this point, the other diagonal cut was filled and photocured , one half at a time. The same technique is followed . This sequence would prevent composite resin from connecting two opposing cavity walls simultaneously, minimizing the negative effects of polymerization shrinkage on the cavity walls and adhesive interfaces also reducing the C-factor ratio. 74

75. Successive cusp buildup technique Here, individual cusps are restored one at a time up to the level of the occlusal enamel. Small sloping increments are applied to each corner of the cavity .This method, while initially time-consuming, can greatly reduce finishing time by precise attention to progressive reconstruction of natural morphology. 75

76. 76 Comparative review: Incremental techniques in direct composite restoration J Conserv Dent. 2017 Nov-Dec ; 20(6): 386–391. -According to Nadig   et al ., incremental technique showed lower microleakage compared to bulk. Among the incremental techniques, split horizontal incremental technique showed least microleakage followed by centripetal technique and oblique placement technique at occlusal margin of Class II restoration. At the gingival margin, there was no significant difference in microleakage between centripetal incremental and oblique placement technique, and split horizontal incremental technique showed least microleakage .[ 30 ]

77. Conclusion 77 Composites have acquired a prominent place among the filling materials employed in direct techniques. Their considerable aesthetic possibilities give rise to a variety of therapeutic indications, which continue to grow as a result of the great versatility of the presentations offered. Nonetheless, it should not be forgotten that they are highly technique-sensitive, hence the need to control certain aspects: correct indication, good isolation, choice of the right composite for each situation, use of a good procedure for bonding to the dental tissues and proper curing are essential if satisfactory clinical results are to be achieved.

78. References Text book of operative dentistry : Sturdervant 5 th EDITION Textbook of dental materials : Phillips Marzouks 9 TH EDITION Mahalaxmi 1 st EDITION Incremental techniques in direct composite restoration J Conserv Dent . 2017 Nov-Dec; 20(6): 386–391. Ocular hazards of curing light units used in dental practice – A systematic review The Saudi Dental Journal Volume 31, Issue 2 , April 2019, Pages 173-180 Light curing in dentistry and clinical implications: a literature review; may 14 (2017) 78

79. Light curing in dentistry and clinical implications: a literature review; may 14 (2017) J Clin Exp Dent. 2018 Jun; 10(6): e555–e560. Intensity output and effectiveness of light curing units in dental offices Review article : Release & Toxicity of dental resin composite Sep-Dec 2012 / Vol-19 / Issue-3 J Conserv Dent . 2016 Sep-Oct; 19(5): 490–493. The stamp technique for direct Class II composite restorations: A case series 79