In situ evaluation of oral pathogen adhesion to orthodontic bracket materials: a split-mouth design with balanced allocation

To evaluate the adhesion of oral pathogens to different orthodontic bracket materials using an in situ split-mouth design with balanced allocation.

Three bracket materials were evaluated: (1) stainless steel, (2) monocrystalline alumina ceramic, and (3) polycarbonate plastic. Customized maxillary trays were fabricated for 10 adult participants, and the materials were systematically assigned to the incisor, canine, premolar, and molar positions according to a predetermined balanced schedule. Participants wore trays containing bracket specimens for 12 hours overnight. Each participant completed at least three sessions, yielding 20 measurements per bracket material at each tooth position. After retrieval, biofilms were detached using sonication. Quantitative real-time polymerase chain reaction was performed to assess total bacteria, Streptococcus mutans, Streptococcus sobrinus, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans. Repeated-measures two-way analysis of variance was used to evaluate the effects of bracket material and tooth position, and their interaction, on bacterial adhesion.

Metal and plastic showed greater total bacterial adhesion than ceramic. S. mutans and S. sobrinus showed higher adhesion to ceramic than to metal and plastic, respectively. No statistically significant differences were observed in the adhesion of P. gingivalis or A. actinomycetemcomitans among the materials. Tooth position had no significant effect on bacterial adhesion.

Bracket material significantly influences bacterial composition during early biofilm formation, whereas tooth position has minimal effect.