Effect of radiotherapy on resin composite adaptation to the cavity wall and elastic modulus of dentin

Abstract

Purpose: This study aimed to evaluate the effects of 60 Gy γ-ray irradiation on the adaptation of resin composite restorations using two-step and one-step self-etching systems. Materials and Methods: One-half of bovine incisors were irradiated with 60 Gy γ-ray. Flat dentin surfaces were prepared on labial side. Cylindrical cavities were prepared on flat dentin surfaces. Cavities were restored with a two-step self-etching system Clearfil SE Bond or a one-step self-etching system Clearfil tri-S Bond adhesive, followed by Clearfil AP-X composite. The composites were light-cured with 600 mW/cm for 40 s. One-half of the specimens were thermocycled for 5,000 cycles. Dye penetration tests around the restorations were performed. Results: Irradiation with 60 Gy γ-ray significantly decreased resin composite adaptation for the nonthermocycled Clearfil SE Bond (p < 0.05). Clearfil tri-S Bond showed significantly decreased cavity wall adaptation compared with Clearfil SE Bond, regardless of the number of thermal cycling and γ-ray irradiation (p < 0.05). Irradiation with 60 Gy γ-ray significantly decreased nanohardness and elastic modulus of the dentin (p < 0.05). Conclusion: Irradiation with 60 Gy γ-ray significantly decreased resin composite adaptation for the non-thermocycled Clearfil SE bond. Further, nanohardness and elastic modulus of the dentin significantly decreased after the irradiation. (Asian Pac J Dent 2019; 19: 39-44.)