EFFECT OF ETCHING TECHNIQUES ON THE SHEAR BOND STRENGTH OF ADHESIVE PRECOATED BRACKETS BONDED IN VITRO

This study was designed to compare shear bond strength durability of two etching techniques namely conventional etching and self-etching primer techniques, when using Adhesive pre-coated brackets (APCII). Thirty extracted premolars were divided into two equal groups (group 1: etched with 37% Phosphoric acid and group 2: bonded with transbond plus self-etching primer), each group was further subdivided into three subgroups each of them contains five teeth, at different storage times: 24 hours, 30 days and 3 months. Universal testing machine was used to measure shear bond strength. T-test revealed that there was no significant difference in shear bond strength between the two etching techniques at 24 hours and 30 days, while showed a highly significant difference (P ≤ 0.01) at 3 months. For the three storage times, self-etching primer showed less adhesive remnant on the teeth than that of Phosphoric acid etching. It can be concluded that self-etching primer provided shear bond strength Comparable to that of phosphoric acid, and it has less adhesive remnant than conventional etching technique.

Adhesive performance of precoated brackets after expiration

ABSTRACT Objective: To evaluate adhesive performance in terms of debonding forces of precoated metal and ceramic brackets 4 years after expiration. Materials and Methods: Buccal and lingual surfaces of embedded extracted maxillary premolars were etched with 34% Tooth Conditioner Gel (Dentsply Caulk, Milford, Del), rinsed, and dried. Transbond MIP (3M Unitek, Monrovia, Calif) was applied prior to placing adhesive precoated brackets (APC II Victory stainless steel and APC Plus Clarity ceramic brackets, 3M Unitek). The preexpiration brackets had 29–35 months before, and the postexpiration brackets were 45–52 months past, their expiration dates. Sample size was 17–21 per group. Debonding forces were determined by subjecting the bonded brackets to a shear force in a universal testing machine. Debonding forces were compared using two-way ANOVA. Debonded surfaces were examined under a stereomicroscope to determine failure modes, which were compared using the chi-square test. Results: No statistically significant difference was found in debonding forces (P = .8581) or failure modes (P = .4538) between expired and unexpired brackets. Metal brackets required statistically significantly higher debonding forces than did ceramic brackets (P = .0001). For both expired and unexpired brackets, failure modes were mostly cohesive in the adhesive layer for ceramic brackets, and mixed between adhesive and cohesive failure in the adhesive layer for metal brackets. Conclusions: Adhesive precoated brackets did not have any reduction in enamel-adhesion properties up to 4 years after their expiration date. Extended shelf life testing for precoated dental brackets may be worth considering.