Takako Yoshikawa, DDS, PhD (1), Makoto Arakawa, DDS, PhD (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 Dental Hygiene, Chiba Prefectural University of Health Sciences, Chiba, Japan
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/cm2 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 non- thermocycled 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.)
Key Words: adaptation, dye penetration, elastic modulus, γ-ray irradiation, microhardness, resin composite