Compositional differences in multi-species biofilms formed on various orthodontic adhesives.

Objectives: To investigate the aspects of multi-species biofilm formation on various orthodontic adhesives with different surface characteristics.

Methods: Multi-species biofilms using 13 bacterial species were grown on the surfaces of composite, compomer, and resin-modified glass-ionomer cement (RMGI). The changes in Streptococcus mutans (Sm), Streptococcus sobrinus (Ss), Porphyromonas gingivalis (Pg), Aggregatibacter actinomycetemcomitans (Aa), and total bacteria were determined at day 1 (T1) and day 4 (T2) using real-time polymerase chain reaction. Surface roughness (SR), surface free energy (SFE), and surface texture were analyzed to explain the differences in bacterial compositions among the adhesives. Repeated measures analysis of variance was used to determine time-related changes in bacterial compositions with respect to adhesive type. The Kruskal-Wallis test was used to determine differences in SR and SFE among the adhesives.

Results: There were no significant differences in the adhesion of total bacteria among the adhesives; however, the adhesion of Sm, Ss, and Pg was higher to RMGI than the other adhesives. The amount of Sm, Ss, and total bacteria increased from T1 to T2, while Pg and Aa decreased from T1 to T2. RMGI showed a rougher surface relative to composite or compomer due to the presence of micro-pores and/or flaws. Compomer had the greatest SFE followed by RMGI and composite. Interestingly, SR differences were about 10 times greater than SFE differences among the adhesives.

Conclusions: Considering the greater differences in SR than SFE among the adhesives, the rougher surface of RMGI may cause greater adhesion of Sm, Ss, and Pg.