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

Takako Yoshikawa, DDS, PhD (1), Alireza Sadr, DDS, PhD (1,2), and Junji Tagami, DDS, PhD (1)

(1) Department of Cariology and Operative Dentistry, Division of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan, and
(2) Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, WA, USA

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.)
Key Words: adaptation, composite, dye penetration, polymerization, residual stress, slow-start curing method