The influence of centrifugation and inoculation time on the number, distribution, and viability of intratubular bacteria and surface biofilm in deciduous and permanent bovine dentin

Abstract

The present study aimed to assess the influence of centrifugation and inoculation time on the number, distribution, and viability of intratubular bacteria and surface monospecies E. faecalis biofilm. Materials and methodsForty-four semicylindrical specimens cut from primary (n = 22) and permanent (n = 22) bovine teeth were randomly assigned to the experimental groups. Teeth of each type were inoculated with E. faecalis with and without centrifugation for 1 and 14 days. The number, localization, viability of bacteria and depth of their penetration were assessed with bacterial culturing of dentin shavings, scanning electron microscopy (SEM) and confocal laser electron microscopy (CLSM). Three-way ANOVA with post-hoc Tukey test were used to assess the influence of different experimental setups on dentin infection. ResultsSevere dentin infection was observed in permanent and deciduous teeth after centrifugation and 1-day incubation: bacteria reached the full length of dentinal tubules and colony-forming units were too numerous to count. The volume of green fluorescence didn’t differ significantly in permanent teeth compared with deciduous (p = 1.0). After 1-day stationary inoculation, small number of cultivable bacteria and few viable bacteria in dentinal tubules were found in both groups. After 14-day stationary inoculation, the dentin infection according to CLSM was deeper in deciduous teeth compared with permanent (p = 0.006 and p = 0.019 for centrifugation and stationary inoculation, respectively). ConclusionThe most even and dense dentin infection was observed in primary and permanent bovine teeth after centrifugation and 1-day inoculation, and in deciduous teeth after 14-day stationary inoculation.