Bond strength of disinfected metal and ceramic brackets: an in vitro study

The aim of this in vitro investigation was to test whether disinfecting with Chlorhexamed fluid had an influence on the shear bond strength of metal and ceramic orthodontic brackets. Metal and ceramic brackets were fixed by the composite adhesives Transbond XT (light curing) and Concise (chemical curing) to 224 bovine permanent mandibular incisors. Bovine teeth were divided into eight groups of 28 each as group 1: metal bracket/Transbond XT, group 2: disinfected metal bracket/Transbond XT, group 3: metal bracket/Concise, group 4: disinfected metal bracket/Concise, group 5: ceramic bracket/Transbond XT, group 6: disinfected ceramic bracket/Transbond XT, group 7: ceramic bracket/Concise, and group 8: disinfected ceramic bracket/Concise. Adhesive bonding was done according to the manufacturers' instructions. As shown by group comparison (Kruskal-Wallis test, univariate analysis of variance, P < .001), the disinfection of metal brackets had no statistically relevant influence on shear bond strength (P = .454). However, disinfecting ceramic brackets with either adhesive led to a significant reduction in shear bond strength compared with the untreated ceramic bracket group (P < .001). The Fisher's exact test of the Adhesive Remnant Index (ARI) scores showed a significant difference within the metal group bonded with different adhesives (P = .0003). The ARI scores 1 and 2 were not reached by the ceramic bracket groups. The disinfection of the ceramic brackets is a suitable procedure for clinical use because the measured shear bond strength values were higher than 6-8 MPa required in orthodontics.