Differences of multi-species biofilm formation in several orthodontic adhesives

Abstract

Objective: This study investigated the aspects of multi-species biofilm formation on several orthodontic adhesives with different surface characteristics. Materials and Methods: Multi-species biofilms using 13 bacterial species were grown with three adhesives: composite (Transbond XT, TX), compomer (Transbond Plus, TP) and resin-modified glass ionomer (Multi-Cure, MC). The adhesion levels of 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 differences in bacterial amounts and proportions of each species to total bacteria 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 adhesion of total bacteria among orthodontic adhesives

however, the adhesion of Sm, Ss, and Pg was higher to MC than the other adhesives. MC also showed higher Sm and Ss proportion to total bacteria than the other adhesives. From T1 to T2, the amount of Sm, Ss, and total bacteria increased, while Pg and Aa decreased. However, proportions of all the tested bacteria to total bacteria were significantly decreased with increased incubation time. MC showed a rougher surface than TX or TP due to the presence of micro-pores and/or flaws. TP had the greatest SFE followed by MC and TX. Interestingly, SR differences were about 10 times greater than SFE differences between the adhesives. Conclusion: Considering the greater differences in SR than SFE among the adhesives, the rougher surface of MC may cause greater adhesion of Sm, Ss, and Pg.