Effects of surface treatment and artificial aging on the shear bond strength of orthodontic brackets bonded to four different provisional restorations

Abstract

Objective: To evaluate the combined effects of material type, surface treatment, and thermocycling on the bond strength of orthodontic brackets to materials used for the fabrication of provisional crowns.

Materials and methods: Four materials were included in this study (ProTemp, Trim Plus, Trim II, and Superpont C+B). Sixty cylindrical specimens (1 × 3 cm) were prepared from each material and equally divided into three groups. The first group was ground with silica carbide paper, the second was polished with pumice, and the last group was sandblasted with 50-µm aluminum oxide particles. Stainless-steel maxillary central incisor brackets (Victory Series, 3M) were bonded to the provisional material specimens with Transbond XT light-cured composite resin, and half of the specimens from each group were thermocycled 500 times in 5°C and 55°C water baths. Then the brackets were debonded with shear testing, and the results were statistically analyzed by three-way analysis of variance and Tukey's multiple-comparison tests at α = 0.05. Adhesive Remnant Index (ARI) was also identified.

Results: Before and after thermocycling, ProTemp materials showed the highest shear bond strength with orthodontic brackets (10.3 and 13.1 MPa, respectively). The statistical analysis indicated an interaction among the three independent variables (P < .05) and statistically significant differences in bond strength among provisional materials (P < .001), surface treatments (P < .001), and thermocycling (P < .05). According to the ARI, most groups demonstrated adhesive failure.

Conclusions: The provisional material type, surface treatment, and artificial aging have a significant effect on bond strength. Sandblasting treatment exerts a beneficial effect on shear bond strength.

Keywords: Adhesives; Orthodontic brackets; Provisional materials; Shear bond strength; Thermocycling.

Figure 1.

(a) The metallic mold used for the production of the specimens. (b) The cylindrical specimens with the bonded bracket. (c) Mounted specimen ready to be tested in shear loading.

Figure 2.

Mean bond strengths (table with data) and standard deviations of all groups tested. Dotted lines with rectangular ends show groups without statistically significant differences among the surface treatments. Dotted lines ending with circles represent groups without statistically significant differences before and after thermocycling. The same capital letter illustrates groups without differences among materials with the same surface treatment and before thermocycling, and numbers indicate groups without significant differences among materials with the same surface treatment and after thermocycling (P > .05).