The effects of orthodontic bonding steps on biofilm formation of Streptococcus mutans in the presence of saliva

Objective. To investigate the effects of various orthodontic bonding steps on biofilm formation of Streptococcus mutans in the presence of saliva. Materials and methods: Hydroxyapatite (HA) and orthodontic adhesive (AD) disks were prepared to a uniform size. HA disks were etched with 37% phosphoric acid gel in the etched group (HE). In the primed group (HP), Transbond XT primer was applied to the etched HA surface and light-cured. For biofilm formation, Streptococcus mutans was grown on each specimen in a biofilm medium with either glucose or sucrose in the presence of fluid-phase UWS (F-UWS) or surface adsorbed saliva (S-UWS). The adherent bacteria were quantified by enumeration of the total viable counts of bacteria. Biofilms formed on each surface were examined by scanning electron microscopy. Results. When glucose was used, both F-UWS and S-UWS suppressed biofilm formation of S. mutans. Compared to HA and HE, biofilm formation was significantly inhibited on HP and AD in the presence of glucose. Biofilm-forming patterns that were inhibited by saliva were restored in a sucrose-containing medium. F-UWS promoted biofilm formation on HA and HE, while S-UWS significantly promoted biofilm formation on HP. S. mutans developed biofilm better on HA and HE than on AD when sucrose was used as the sole carbohydrate source. Conclusions. This study suggests that the biofilm development by S. mutans is significantly influenced by the orthodontic bonding procedure. Biofilm formation of S. mutans was inhibited on AD more than other surfaces, irrespective of the presence of saliva or a carbohydrate source.