Clinical and laboratory evaluation of a ceramic bracket system in orthodontics

Abstract

The purpose of this study was to evaluate the performance in vivo and the in vitro retention of the Allure (GAC) orthodontic ceramic bracket system. Forty human extracted premolars were bracketed with either (A) ceramic brackets (n=20); or (B) metallic (GAC) brackets (n=20). In each group, 10 brackets were bonded with a seIf curing composite (Accubond, GAC) and the other 10 with a light activated composite (Reliance). Teeth were kept in water at room temp. for 7 days. Bond strength was measured by separating brackets in an lnstron machine with a shear force perpendicular to the tooth surface. The in vivo experiment comprised 20 patients in which 152 teeth were bonded with the ceramic brackets and 88 teeth with metallic brackets (control) using either light cured or self cured adhesive systems. ln vitro shear bond strengths were as follows: Self cure lbs/in[2] Light cure lbs/in[2] ceramic (A): 1756[plus or minus]415 2570[plus or minus]996 metallic (B): 2250[plus or minus]507 2082[plus or minus]570 Clinical examination after 20 to 24 months revealed 25% failures in the ceramic group and 2% failures in the metallic group. Failures of 82% of the ceramic brackets were by catastrophic fractures of the bracket itself. ANOVA revealed a significant difference among the groups. Ceramic and metallic brackets were equally retentive in vitro but ceramic brackets were significantly less resistant to failure in vivo.