Shear bond strength of adhesive precoated brackets: A comparative in vitro study

Objective > This study compared the shear bond strength of orthodontic precoated brackets from different manufacturers. Methods > Sixty extracted human premolar teeth were divided into six groups (n = 10). The groups were bonded with one of the following brackets: 3MTM Unitek VictoryTM SeriesTM with APC, 3MTM Unitek ClarityTM Advanced CeramicTM with APC, TP Nu-Edge (R) NX Cobalt-Chromium and TP In-Vu (R) ceramic Readi-Base (R) both with eXact (R) orthodontic adhesive, 3MTM Unitek Clarity Advanced CeramicTM and 3MTM Unitek VictoryTM SeriesTM both with TransbondTM XT Adhesive. Each group was tested for shear bond strength using a universal testing machine. Each sample was observed under a dissecting microscope and received an adhesive remnant index (ARI) score. Statistical analysis was performed using Tukey's Standardized Range (HSD) Test to make comparisons among all groups and a Wilcoxon rank-sum test to evaluate for pairwise comparisons between the groups. The P-values < 0.05 were considered significant. Results > The ceramic control was not statistically different from the metal control, 3MTM VictoryTM APCTM, TP In-Vu (R) ceramic eXact (R) or TP Nu-EDGE (R) eXact (R) in terms of shear bond strength (7.69 +/- 1.41 MPa, 7.72 +/- 1.25 MPa, 8.70 +/- 1.93 MPa, 4.90 +/- 1.76 MPa, 5.33 +/- 0.78 MPa, respec-tively). However, it was statistically different from 3MTM Ceramic APCTM (10.29 +/- 2.78 MPa). In terms of modulus, there were no statistical differences. TP's Nu-edge (R) had the lowest average ARI score, but was not statistically different when compared to the other groups. Conclusion > 3MTM Unitek's Ceramic APC had a statistically higher SBS than the non-precoated brackets and TP Orthodontics' precoated brackets. However, all SBS were 4.9 MPA or above, which is deemed clinically acceptable in terms of laboratory forces. There was no statistical difference between manufacturing companies or precoated vs. non-precoated modulus and ARI scores.