In vitro effect of photodynamic therapy with two photosensitizers on Streptococcus mutans load around metal and ceramic brackets bonded to enamel.

Abstract

Background and objectives: The inherent surface porosities of ceramic brackets can enhance bacterial plaque accumulation. This study assessed the in-vitro effect of photodynamic therapy (PDT) with two photosensitizers (PSs) on Streptococcus mutans (S. mutans) load around metal and ceramic brackets bonded to enamel.

Materials and methods: In this in vitro experimental study, 48 sound premolars extracted for orthodontic reasons were randomly assigned to two groups (n=24) for bonding to metal and ceramic brackets. After bracket bonding, the tooth-bracket assemblies were inoculated with S. mutans, and each group was randomly divided into three subgroups (n=8) of control, PDT with toluidine blue O (TBO) and 635 nm laser, and PDT with indocyanine green (ICG) and 808 nm laser. The colony count was quantified in each subgroup, and analyzed by repeated measures ANOVA.

Results: Ceramic brackets showed a significantly higher colony count than metal brackets in the control subgroup by 7.057 log10 CFUs/mL (P<0.05). PDT, irrespective of PS type, significantly decreased the bacterial count around both ceramic (by 7.616 log10 CFUs/mL in the ICG and 7.594 log10 CFUs/mL in the TBO subgroup) and metal (by 7.512 log10 CFUs/mL in the ICG and 7.505 log10 CFUs/mL in the TBO subgroup) brackets (P<0.05). The difference in bacterial count was not significant between the ceramic and metal bracket groups after PDT (P=0.541 for ICG and P=0.101 for TBO).

Conclusion: Within the limitations of this in vitro study and as an attempt to predict what might happen in vivo, the results showed that PDT significantly decreased the bacterial load around metal and ceramic brackets bonded to enamel, irrespective of the type of PS. Thus, PDT may be considered as a possibly efficient strategy to minimize the bacterial load especially around ceramic brackets.