Abstract
Objective
This study investigates the shear-peel orthodontic bond strengths of brackets bonded with an unfilled acrylic resin containing 4-META (MCP Bond®) or a no-mix composite adhesive (Right On®) to acid-etched or sandblasted enamel.
Design
Ex vivo.
Materials and methods
Eighty human pre-molar teeth were separated into four equal groups, according to the adhesive used and method of enamel pre-treatment. Group I—Right On® with enamel etched using phosphoric acid for 30 seconds. Group II—Right On® with enamel sandblasted using 50-μm alumina particles at 80 psi for 3 seconds. Group III—MCP Bond® with enamel etched using phosphoric acid for 30 seconds. Group IV—MCP Bond® with enamel sandblasted using 50-μm alumina particles at 80 psi for 3 seconds. Subsequently, the specimens were stored in distilled water for 24 hours prior to bond strength testing using an Instron® universal testing machine. Each debonded tooth was scored using the adhesive remnant index (ARI) to determine the site of bond failure.
Results
The mean bond strength (1 SD) were Group I: 10.7 (2.7) MPa, Group II: 5.3 (1.3) MPa, Group III: 15.9 (3.4) MPa, Group IV: 15.0 (2.2) MPa. Statistical analysis using one-way analysis of variance and Tukey test found no statistical difference between Group III and Group IV (P > 0.05), but the other groups were statistically different from each other (P < 0.05). The data were found to fit the Weibull distribution and Weibull analysis showed stress required for a 5 per cent probability of failure was: Group I: 5.77 MPa; Group II: 3.32 MPa; Group III: 10.31 MPa; Group IV: 10.58 MPa. Chi-square test showed a statistically significant difference existed between the ARI scores (P < 0.001), principally through less adhesive remnants being observed on the sandblasted specimens.
Conclusion
The adhesive containing 4-META achieved significantly higher bond strengths than the composite adhesive, particularly in the case of sandblasted enamel.
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