Effects of Ultrasonic Toothbrushes with Different Frequencies on Oral Hygiene

Objectives: General ultrasonic toothbrushes have a frequency of 1.6 MHz. However, few studies have investigated whether 1.6 MHz is the most effective ultrasonic frequency for oral hygiene. The purpose of the present study was to compare the effects of ultrasonic toothbrushes with different frequencies on oral hygiene in healthy people.
Methods: Fifty first-year dental hygiene students were randomly divided into three groups, and used ultrasonic toothbrushes with different frequencies (1.6, 3.2, and 4.8 MHz) twice a day (3-min sessions) for 8 weeks. The plaque index (PlI) and the gingival index (GI) were assessed at 4 and 8 weeks by a blinded examiner. The unstimulated salivary flow rate was measured in each participant, and the Steel test was used to compare intragroup differences.
Results: The GI was significantly lower in the 3.2 and 4.8 MHz groups at 8 weeks (3.2 MHz group: p < 0.01, 4.8 MHz group: p < 0.05). At 4 weeks, the GI was significantly lower in the 3.2 MHz group (p < 0.05) and tended to be lower in the 4.8 MHz group (p = 0.07). The PlI was significantly lower in the 3.2 MHz group at 8 weeks (p < 0.01) and tended to be lower in the 1.6 and 4.8 MHz groups (1.6 MHz: p = 0.07, 4.8 MHz: p = 0.05). In addition, the PlI was significantly lower in the 4.8 MHz group at 4 weeks (p < 0.05). No significant changes were observed in the unstimulated salivary flow rate.
Conclusions: The results of the present study suggest that ultrasonic toothbrushes with higher ultrasonic frequencies may be effective for reducing GI and PlI scores and improving oral hygiene.