The aim of this study was to investigate the effect of laser irradiation to computer-aided de-sign/computer-aided fabrication (CAD/CAM) resin blocks coated with a silane coupling agent on the bond strength between the resin blocks and composite resin. The CAD/CAM resin blocks used in this study were Cerasmart 300 (GC) and Vita Enamic (Vita); they were cut into plates and then subjected to a series of treatments. After processing with a silane coupling agent, treatment with a semiconductor laser was performed at 3.0, 5.0, and 7.0 W, followed by the bonding procedures. The control group included those exposed to silane and bonded without laser application. After bonding, a mold with a simulated cavity was formed on the specimen and filled with flowable composite resin, and they were stored for 24 h or stressed by thermal cycling for subsequent testing that assessed the shear bond strength (n = 10). The results revealed that the bond strength was significantly enhanced by laser irradiation after applying a silane coupling agent, whereas significant effect was not detected between the materials. Particularly, 7 W laser irradiation had a significant effect on the bond strength between the composite resin and Cerasmart block after thermal cycling.

Antimicrobial photodynamic therapy (aPDT) used to sterilize carious dentin may irritate the pulp tissues because of tissue-penetrating laser and singlet oxygen generation. This study aimed to assess the effects of aPDT on rat pulp tissues. A cavity formed in a rat maxillary first molar was treated with aPDT. The combined photosensitizer and laser irradiation conditions in the aPDT groups were as follows: methylene blue and 100 mW for 60 s, brilliant blue (BB) and 100 mW for 60 s, BB and 50 mW for 120 s, and BB and 200 mW for 30 s. Each cavity was treated with an all-in-one adhesive and filled with flowable resin. aPDT was not applied for the control. In each group, the rats were sacrificed on postoperative days 1 and 14, and thin sections of the treated teeth were prepared. Pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), and tertiary dentin formation (TDF) were evaluated. At 1 day evaluation, there were significant differences between the aPDT group and controls with respect to PTD and ICI. 14 days later, almost all specimens showed tertiary dentin formation. aPDT caused temporarily reversible injury to the rat dental pulp, which healed with tertiary dentin formation.

This study aimed to assess the impact of different modes of laser irradiation on the bactericidal efficacy of aPDT. Dentin plates were prepared by sectioning the crown dentin of bovine teeth infected with Streptococcus sobrinus. Nine aPDTs involving the combinations of three photosensitizers (brilliant blue, BB; acid red, AR; and methylene blue, MB) and three laser irradiation modes (50 mW for 120 s, 100 mW for 60 s, and 200 mW for 30 s) were performed for each infected dentin plate, and the control group consisted of the specimens not applied with aPDT. The bactericidal effects in 10 experimental groups were evaluated (n=11) using both assays of the colony-count and adenosine triphosphate (ATP). The data obtained were analyzed using the Kruskal-Wallis test. The aPDT performed with semiconductor laser in combination with BB, AR, and MB exerted a remarkable bactericidal effect. aPDT with MB exerted a more significant bactericidal effect in the colony-count assay. The results of aPDT performed with varying irradiation times and powers but with constant irradiation energy showed no difference with AR and MB between the modes, whereas BB showed a more significant bactericidal effect when irradiated for a shorter time at a higher irradiation power.