Aim:

To verify the hypothesis that self-ligating brackets favor greater aggregation of microorganisms when compared with conventional brackets.

Methods:

Four types of self-ligating metal brackets were evaluated. Initially, 50 brackets were divided into five groups (n=10): Morelli Conventional, GAC (In-Ovation R, Dentsply Caulk), Aditek (Easy Clip), Ormco (Damon System) and 3M Unitek (Smart Clip). An in vivo evaluation was carried out in which the brackets were bonded to the mandibular teeth of five healthy individuals who had not undergone previous orthodontic treatment. The right hemiarch brackets were used for bacterial plaque collection and those on the left side were examined by scanning electron microscopy (SEM). Before bracket bonding, the bacterial plaque material aggregated to the tooth surfaces was collected, with the areas of choice being the cervical-buccal and mesial and distal interproximal regions. After 21 days had elapsed since bonding, the plaque adhered to the winglet, channel and cervical regions of the bracket bases was collected. The materials collected were diluted and seeded on Petri dishes onto Mitis salivarius medium specific for S. mutans and non-specified BHI culture medium. Colony forming unit (CFU) counts were performed visually after 24, 48 and 72 h of incubation.

Results:

Greater bacterial accumulation was observed on the winglets of 3M brackets, with statistical statistically significant differences from the other types (p<0.05). As regards the channel regions, most microorganisms accumulated in the Ormco Group (p<0.05), and in the cervical region of Aditek brackets. In all evaluated regions, those with least bacterial accumulation were the conventional brackets.

Conclusions:

The hypothesis was confirmed, as the self-ligating brackets were shown to have greater bacterial accumulation when compared with the conventional brackets.