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 fiber-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 flowable 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 first 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 significant difference in SBS among the study groups (P <0.001). Pairwise comparisons indicated that SBS was significantly lower in group 1 compared to all other groups (p<0.05) except group 2. Bond strength in group 6 was significantly greater than all the study groups (p<0.05) except group 5. No significant difference was found in ARI scores among the groups. Conclusions: Covering the FRC surface by a layer of flowable 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. Key words:Fiber-reinforced composite, orthodontics, Sshear bond strength, laser, Er:YAG, surface treatment, bracket, FRC.
Highlights
Fiber reinforced composite (FRC) is a combination of long continuous fibers and a bisphenol-a-glycidyl dimethacrylate (Bis-GMA) matrix, which provides optimal mechanical properties such as high flexural and fracture strength and adequate flexural modulus [1,2]
The lowest shear bond strength (SBS) belonged to group 1 (8.29 ± 0.84 MPa) in which neither the FRC surface was covered by flowable composite nor erbium family (Er):YAG laser treatment was performed
Covering the FRC surface by a layer of flowable composite and application of Er:YAG laser at 300 mJ/15 Hz resulted in significantly higher bond strength compared to the other study groups (p
Summary
Fiber reinforced composite (FRC) is a combination of long continuous fibers and a bisphenol-a-glycidyl dimethacrylate (Bis-GMA) matrix, which provides optimal mechanical properties such as high flexural and fracture strength and adequate flexural modulus [1,2]. Recent experiments investigated the efficacy of erbium family (Er:YAG and Er,Cr:YSGG) lasers for etching dentin and enamel [10,11,12,13,14], surface roughening of composite restorations to enhance bonding [15,16], and bracket base reconditioning [17,18,19]. Considering the effectiveness of erbium lasers in roughening the surface [20] and increasing micromechanical retention [17,18], it seems that laser conditioning can be employed as a way to enhance bond strength of orthodontic attachments to FRC bars. This study aimed to investigate the effect of FRC surface treatment with Er:YAG laser on shear bond strength (SBS) and mode of bond failure of orthodontic brackets
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