Shear bond strength of orthodontic brackets bonded to various esthetic pontic materials

Abstract

In this in-vitro study, we compared the shear bond strengths of orthodontic brackets bonded to various commonly used esthetic pontic materials. Prefabricated denture teeth (acrylic resin, Trubyte, Dentsply, York, Pa) and samples made from Integrity (bis-acryl composite resin, Dentsply Caulk, Milford, Del) and Alike (polymethylmethacrylate resin, GC America, Alsip, Ill) were used to represent the more common esthetic provisional materials. Each material group contained 30 samples; a total of 90 samples were bonded in the same fashion with APC PLUS maxillary lateral incisor brackets (3M Unitek, Monrovia, Calif). Each material group was then divided into 2 testing subgroups. One subgroup was tested for shear bond strength 24 hours after bonding, and the other subgroup was tested after bonding and storage in distilled water at 37 degrees C for a week. Each bracket was loaded perpendicularly in a universal testing machine at a crosshead speed of 1.0 mm per minute until bonding failure. The mean shear bond strength and standard deviation were determined for each group. Analysis of variance (ANOVA, 2-factor and 1-factor) with Tukey HSD post-hoc tests, Student t tests, and Mann-Whitney U tests were used to test the main effects of pontic materials and time of loading (alpha = 0.05). The data were stratified, and 1-way ANOVA tests were performed with the Bonferroni adjustment (alpha = 0.01) to examine the effect of the pontic material on shear bond strength after either 1 day or 7 days of storage. Significant differences were found based on pontic material and time (P <0.05), but there was a significant interaction (P = 0.044), making the results uninterpretable. At 1 day, the Integrity material had a significantly higher mean shear bond strength than both Alike and the denture tooth materials (P <0.001). However, at 7 days, both Integrity and Alike had significantly higher mean shear bond strengths compared with the prefabricated denture tooth (P <0.001). Although the use of Integrity or Alike requires an additional armamentarium, necessitating individual pontic fabrication by the dental practitioner, indications for clinical use are evident with direct applications to multi-disciplinary treatment modalities.