The effect of surface treatment with Er:YAG laser on shear bond strength of orthodontic brackets to fiber-reinforced composite

Abstract

Objectives: This study aimed to investigate the effect of surface treatment with Er:YAG laser on shear bond strength (SBS) of orthodontic brackets to fi ber-reinforced composite (FRC). Study Design: Ninety human premolars were randomly divided into six groups of 15. FRC bars were bonded to the teeth with a fl owable composite (FC) and then underwent following treatments. In group 1 no further treatment was performed. In group 2 the FRC surfaces were covered by FC. An Er:YAG laser was employed to treat FRCs in groups 3 (200 mJ/10 Hz) and 4 (300 mJ/15 Hz). The FRC strips in groups 5 and 6 were fi rst covered by FC and then irradiated with Er:YAG laser at 200 mJ/10 Hz (group 5) or 300 mJ/15 Hz (group 6). Stainless steel brackets were bonded to FRCs using a light-cure adhesive system. After 24 hours, the samples were tested for SBS and the adhesive remnant index (ARI) scores were determined. Results: There was a signifi cant difference in SBS among the study groups (P <0.001). Pairwise comparisons indicated that SBS was signifi cantly lower in group 1 compared to all other groups (p<0.05) except group 2. Bond strength in group 6 was signifi cantly greater than all the study groups (p<0.05) except group 5. No signifi cant difference was found in ARI scores among the groups. Conclusions: Covering the FRC surface by a layer of fl owable composite and then application of Er:YAG laser at 300 mJ/15 Hz could be recommended to increase bond strength of orthodontic attachments to FRC.