Evaluation of the use of ultrasound within a power toothbrush to dislodge oral bacteria using an in vitro Streptococcus mutans biofilm model.

PURPOSE: To investigate in vitro the use of ultrasound in a power toothbrush to aid in the removal of dental plaque biofilm without bristle contact. METHODS: Dental plaque was modeled using Streptococcus mutans biofilm adherent to hydroxyapatite disks. Treatment arms included positive and negative controls, disks with and without biofilm, respectively. Power toothbrush modes of action tested included a toothbrush with sonic and ultrasonic action (ULT), the same toothbrush with only sonic action (ULN), a sonic toothbrush (SON) and a rotating/oscillating toothbrush (OSC). The active element of the toothbrushes (bristles or point of ultrasound emission) was immersed in toothpaste slurry and held 3 mm away from the disk surface. Treatment included activation of the toothbrush mode of action for 5 seconds. Control disks were exposed to the same fluid environment but not exposed to a power toothbrush. After treatment, biofilm present on the disks was stained using a red dental plaque disclosing solution. Photographs were then taken and the presence of biofilm assessed using digital image analysis. For each disk a normalized pixel volume, related to the presence of biofilm corrected for lighting, was determined. Statistical testing was done with a one-way ANOVA and a Bonferroni post hoc test. RESULTS: Normalized pixel volumes (mean +/- standard deviation) were 0.428 (0.010) for the negative control and 1.022 (0.040) for the positive control. Normalized pixel volumes for the power toothbrush modes of action were 0.641 (0.075) for ULT, 0.972 (0.027) for ULN, 0.921 (0.010) for SON and 0.955 (0.025) for OSC. Statistical analysis showed a significant treatment effect (P<0.001). All power toothbrush modes of action exhibited some biofilm removal without bristle contact in this in vitro assay. Of the modes of action tested, the combined sonic and ultrasonic mode of action (ULT) removed the greatest amount of biofilm from the disk surfaces. The same toothbrush when tested with (ULT) and without (ULN) ultrasound showed a greater amount of biofilm removed when ultrasound was present.