COSMETIC & RESTORATIVE CARE An alternative method to reduce polymerization shrinkage in direct posterior composite

1. COSMETIC & RESTORATIVE CAREAn alternative method to reduce polymerization shrinkage in direct posterior composite restorations SIMONE DELIPERI, D.D.S.; DAVID N. BARDWELL, D.M.D., M.S.

2. Spreafico RC, Gagliani M. Composite resin restorations on posterior teeth. InAdhesion The silent revolution in dentistry. Chicago: Quintessence; 2000:253-76.

3. Yoshikawa T, Sano H, Burrow MF, Tagami J, Pashley DH. Effects of dentin depth and cavity configuration on bond strength. J Dent Res 1999;78:898-905.

4. In three decades ago resine-based composite was….. • Wear resistance • Micro leakage • Secondary caries • Lack of appropriate proximal contact

5. In the past 10 years…dramatic improvement in newer-generation bonding agents and resin-based composite formulations • Significantly improved wear resistance • good proximal contact and contour • polymerization shrinkage remains the biggest challenge

6. Polymerization shrinkage • formation of a gap between resin-based composite and the cavity wall • 1.67 to 5.68 percent of the total volume • postoperative sensitivity and recurrent caries • bonding failure

7. Stress from polymerization shrinkage is influenc by • restorative technique • modulus of resin elasticity • polymerization rate • cavity configuration or “C-factor.”

8. C-factor is… • ratio between bonded and unbonded surfaces • an increase in this ratio results in increased polymerization stress -Three-dimensional cavity preparations (Class I) have the highest (most unfavorable)

9. To minimize the stress from polymerization shrinkage • improving placement techniques • improving material and composite formulation • curing methods

10. Placement techniques and issues.

11. The incremental technique • Direct shrinkage • Bulk technique

12. The incremental technique • polymerizing with resin-based composite layers less than 2-millimeters thick • achieve good marginal quality • prevent distortion of the cavity wall • ensure complete polymerization of the resin-based composite

13. Horizontal technique • occlusogingival layering • generally used for small restorations • increases the C-factor.

14. Three-site technique • clear matrix and reflective wedges • guide the polymerization vectors toward the gingival margin.

15. Oblique technique • wedge-shaped composite increments • prevent distortion of cavity walls and reduce the C-factor • polymerization first through the cavity walls and then from the occlusal surface • direct vectors of polymerization toward the adhesive surface (indirect polymerization technique)

16. Successive cusp buildup technique • the first composite increment is applied to a single dentin surface without contacting the opposing cavity walls • And then wedge-shaped composite increments • Each cusp then is built up separately • to minimize the C-factor in 3-D cavity preparations

17. Figure 1. Schematic representation of wedge-shaped composite increments (1-6) used to build up the enamel proximal surface. F: Facial aspect. L: Lingual aspect.

18. Figure 2. Schematic representation of the flowable composite increment (1) and wedge-shaped increments (2-7) used to build up dentin;two increments (8 and 9) are used to build up enamel using the successive cusp buildup technique. F: Facial aspect. L: Lingual aspect.

19. Resin-based composite materials &Dentin-enamel adhesive systems

20. Resin-based composite materials • By experimenting with particle size, shape and volume, manufacturers have introduced resin-based composites with differing physical and handling properties • microfill, • hybrid • microhybrid • packable • flow-able

21. TABLE 1

22. TABLE 2

23. Dentin-enamel adhesive systems…Bonding to dentin introduced more recently and has improved over the years • contemporary DAS(dentin-enamel adhesive systems) around 22 Mpa • early bond strength to dentin ranged from 1 to 10 megapascals ……………..

24. Curing methods

25. soft-start” polymerization • “soft-start” polymerization (Miyazaki et al.) • composite exhibited improved physical properties when cured at a low intensity and with slow polymerization vs. higher intensity and faster polymerization

26. initially uses low-intensity curing • for a short period to provide sufficient network formation on the top composite surface • delaying • until the gel point • final high-intensity polymerization

27. highly mineralized tissue (Enamel) • resulting in a lower flexibility and decreased ability in relief of shrinkage stress • high–C-factor restorations • high-modulus composites • transmit more polymerization shrinkage forces to the tooth

28. TABLE 3

29. Figure 3. Preoperative occlusal view of tooth no. 3.

30. Figure 4. Tooth no. 3 after a rubber dam was placed, caries was removed and the cavity preparation was completed with a gingival butt joint and no bevel either on the axial or occlusal surface

31. Figure 5. A matrix was placed to protect adjacent tooth structure during cavity preparation and etching. Then etching was performed using 35 percent phosphoric acid.

32. Figure 6. Enamel’s and dentin’s glossy appearances after application of a fifth-generation, 40 percent filled ethanol-based adhesive system.

33. Figure 7. A sectional matrix, plastic wedge and G-ring placed to reconstruct the proximal surface.

34. Figure 8. Tooth no. 3 after the enamel proximal surface was built up using the Pearl Neutral enamel shade of the microhybrid composite (Vitalescence, Ultradent Products Inc., South Jordan, Utah).

35. Figure 9. Tooth no. 3 after the sectional matrix, plastic wedge and G-ring were removed and the A2 shade of the flowable composite (PermaFlo, Ultradent Products Inc., South Jordan, Utah) was applied to a single dentin surface.

36. Figure 10. A and B. Tooth no. 3 after wedge-shaped composite increments of A3. 5, A3 and A2 shades of the microhybrid composite (PermaFlo, Ultradent Products Inc., South Jordan, Utah) were used to reconstruct dentin

37. Figure 11. Tooth no. 3 after Pearl Neutral enamel shade of the microhybrid composite (Vitalescence, Ultradent Products Inc., South Jordan, Utah) was used to build up the occlusal surface according to the successive cusp buildup technique.

38. Figure 12. Postoperative occlusal view of tooth no. 3.

39. 2 1 4 3

40. 5 6 7 8

41. After Before

42. To minimize the stress from polymerization shrinkage • improving placement techniques • placing successive layers of wedge-shaped composite(1- to 1.5-mm) to decrease the C-factor

43. To minimize the stress from polymerization shrinkage • improving material and composite formulation • select different composite materials to restore dentin (flowables and microhybrids) and enamel (microhybrids)

44. To minimize the stress from polymerization shrinkage • curing methods • “soft-start” polymerization

45. EXPERIMENTAL ARTICLE REVIEW

46. The suitability of packable resin-based composites for posterior restorations

47. Modulus of elasticity • Vickers hardness • Depth of cure • Scraping • Producing a hardness profile

48. TABLE 1

49. TABLE 2

50. Figure. Determination of curing depth of the tested materials by scraping vs. producinga hardness profile(r2 = 0.9945). mm: Millimeters. Manufacturers are as follows: Ariston pHc and Tetric Ceram, Ivoclar Vivadent, Schaan, Liechtenstein; Definite, Degussa AG, Hanau, Germany; Solitaire, Heraeus Kulzer, Wehrheim, Germany; SureFil, Dentsply De Trey, Konstanz, Germany; Alert, Jeneric/Pentron.