RESUMEN
Streptococcus mutans is one of the principal pathogens of the human oral habitat, being one of the principal etiological agents of carious lesions. Ozone is a powerful oxidant, it has the ability to inactivate microorganisms in general, and ultrasound is an acoustic system generated through a piezoelectric crystal that also presents microbicidal effects. In the present study, a comparative analysis was made of the damage caused to Streptococcus mutans in vitro by ultrasound and ozone, through scanning electron microscopy (SEM) and atomic force microscopy (AF) analysis. In addition, flow cytometry was used to determine microbial viability and the formation of Reactive Oxygen Species (ROS) after the application of different techniques. The data obtained by means of micro- scopic analysis reveal that both ozone and ultrasound produce morphological alterations in bacteria, which become rod-shaped organisms. In addition to this deformation, on the microbial surface it was possible to identify crater-like impressions. In contrast, the irregularity of protuber- ances on the surface of the microbial wall was only detected when ozone was employed. Regarding the formation of ROS, it was observed that that ozone induces a significant growth (p < .05) of these molecules, while ultrasound does not present this effect. Ozone and ultrasound present micro- bicidal effects, however, ozone is more efficient.