Effect of different atmospheres on microcosm biofilm formation and tooth demineralization

Abstract

This study evaluated the effects of different atmospheres on the cariogenic potential of microcosm biofilms. Ninety bovine enamel and 90 dentin specimens were allocated into three atmospheres: 1) microaerophilia (5 days, 5% CO2); 2) anaerobiosis (5 days, jar); 3) mixed (2 days microaerophilia and 3 days anaerobiosis), which were subdivided into 0.12% chlorhexidine (positive control- CHX) and Phosphate-Buffered Saline (negative control- PBS) (n = 15). Biofilms were prepared using human saliva and McBain's saliva containing 0.2% sucrose. From the second day, the specimens were treated with CHX or PBS (1 x 1 min/day). After five days, colony-forming units (CFU) were counting and tooth demineralization was analyzed using transverse microradiography (TMR). Data were subjected to two-way ANOVA and Tukey–Sidak’s test (p < 0.05). Regarding CFU counting, most atmospheres were able to differentiate between CHX and PBS (differences of 0.3–1.48 log10 CFU/ml), except for anaerobiosis and microaerophilia for total microorganisms in enamel and dentin biofilm, respectively. In the case of dentin, no effect of CHX on Lactobacillus spp. was observed. All atmospheres were able to differentiate between CHX and PBS regarding enamel demineralization, showing lower mineral loss and lesion depth for CHX (78% and 22% reductions for enamel and dentin, respectively). The enamel mineral loss data did not differ between the models; however, the enamel lesion depth was greater under anaerobiosis. Dentin mineral loss was lower under anaerobiosis than under other atmospheres. Conclusion: The choice of atmosphere did not seem to interfere with the cariogenic potential of the microcosm biofilm.