Effect of light curing method and thermal cycling on resin composite adaptation to the cavity wall

Purpose: This study evaluated the effects of the light curing methods and thermal cycling on adaptation to the cavity wall of different type of resin composite using a dye penetration test. Materials and Methods: Cylindrical cavities with one-half enamel and one-half dentin margins were prepared on the labial cervical region of bovine incisors. Cavities were restored using Clearfil tri-S Bond ND Quick and filled with Clearfil AP-X or Clearfil Photo Bright composite. The resin composites were cured using the conventional or the slow-start curing method. Half of specimens were thermocycled. Results: Clearfil AP-X showed significantly greater cavity-wall gap formation than that of Clearfil Photo Bright with both the conventional curing method and slow-start curing method with thermal cycling at 500 cycles (p < 0.05). The slow-start curing method showed significantly improved resin composite adaptation to the cavity wall compared with the conventional curing method for thermocycled Clearfil Photo Bright specimens (p < 0.05). Thermal cycling at 500 cycles significantly decreased cavity-wall gap formation compared with 0 cycle for Clearfil Photo Bright resin composites (p < 0.05). Clearfil Photo Bright using the slow-start curing method with thermal cycling at 500 cycles showed least cavity-wall gap formation. Conclusion: Light-cured composite, increased contrast ratio during polymerization with thermal cycling at 500 cycles, improved adaptation to the cavity wall using the slow-start curing method. The slow-start curing method facilitated the high reduction for residual stress of composite that had increased contrast ratio. (Asian Pac J Dent 2019; 19: 59-64.)