Sonic and mechanical toothbrushes - An in vitro study showing altered microbial surface structures but lack of effect on viability

The purpose of the present study was to compare the in vitro effects of a m echanical and a sonic toothbrush on the viability of Actinomyces viscosus, the rationale being that induction of irreparable microbial damage resultin g from aggressive mechanical action or sonic energy, may inhibit or disrupt the process of successional colonization. Cultures of A. viscosus were gro wn to a standardized optical density and subdivided into 3 treatment groups of 20 specimens each. Treatment groups consisted of an untreated control a nd exposure to a mechanical or sonic toothbrush for 15, 30, 45, and 60 s. S ubsequent to the prescribed treatment, samples were taken from each specime n dish, subcultured, and the number of CFUs determined. Additional samples were obtained for negative staining and examination by electron microscopy. The mean number of CFUs for each treatment group at each treatment interva l were statistically analyzed by ANOVA and multiple pairwise comparisons. R esults showed a significant main effect for toothbrushes (p<0.0001) and exp osure time (p<0.01), but only marginal significance for the interaction of toothbrush with exposure time (p<0.055). Post-hoc tests showed a significan tly greater number of CFUs for the sonic toothbrush compared to both the un treated control and mechanical toothbrush groups. Electron microscopic exam ination revealed a decrease in aggregation tendency and loss of fimbriae in the sonic toothbrush group. Based on the lack of morphologic evidence that would indicate cell damage and the increase in CFUs over that of the contr ol group, it appeared that neither the mechanical or sonic toothbrushes aff ected cell viability.