Effect of Er:YAG Laser and Chitosan on Dentin Bond Strength

Objectives: Biopolymers can modify caries-affected dentin after selective removal with Er:YAG laser promoting a better substrate to receive restorative treatment. This in vitro study investigated the influence of the selective removal of carious lesions by Er:YAG laser followed by the rewetting with chitosan on microtensile bond strength (µTBS).
Methods: Bovine incisors were cut in specimens of 6 x 6 x 2.5mm and dentin surface was polished. Artificial dentin lesions were created by pH-cycling method (8h in demineralizing solution and 16h in remineralizing solution) for 14 days. Selective removal of carious lesion was performed with low-speed handpiece (CA 1:1L Bien-Air) or Er:YAG laser (MSP mode, 250 mJ, 4 Hz). Specimens were treated with phosphoric acid and rewetted with 2.5% chitosan. Restoration was performed employing adhesive system and Z250XT resin. Specimens were randomly assigned into four groups according to selective caries removal method and dentin rewetting (n=12): (I) low-speed handpiece, (II) low-speed handpiece rewetting with chitosan, (III) Er:YAG laser and (IV) Er:YAG laser rewetting with chitosan. After 24h, specimens were sectioned ± 1mm² sticks and microtensile bond strength test was performed. Data were analyzed by ANOVA and Tukey test (α=0.05).
Results: The highest values of µTBS (p<0.05) were obtained after the selective removal by low-speed handpiece (18.04 ± 3.66a) compared to Er:YAG laser (12.94 ± 1.98b). The specimens rewetted with chitosan after the use of low-speed handpiece (17.10 ± 4.80a) showed highest values of µTBS (p<0.05) compared those rewetted after Er:YAG laser irradiation (14.19 ± 2.78b).
Conclusions: It can be concluded that Er:YAG laser affects µTBS of caries-affected dentin and the rewetting with 2.5% chitosan did not interfere negatively on the bond strength of restorative material to dentin.