Not too harmful, not too still but just right: characteristics of an ultrasonic toothbrush

Abstract

An ultrasonic toothbrush could cause damage like other toothbrushes if the teeth are brushed with too high force or when the enamel is more vulnerable. But ultrasound has risks on its own so the safety of an ultrasonic toothbrush should be evaluated. The purpose of this study was to quantify pressure, frequency and mechanical movement of an ultrasonic toothbrush as well as temperature changes and abrasiveness of the brush so the safety of the brush could be estimated. The frequency and the pressure of the ultrasonic toothbrush was measured with a hydrophone and the temperature changes of the brush was measured with an analogue thermometer. The mechanical movement of the brush was recorded with a high-speed camera and a surface of an china bowl was imaged with a microscope to detect possible surface damages caused by the brush. The lower frequency of the brush was 420kHz and the higher frequency was 840kHz and lowest measured pressure was −35,4 kPa and those lead to mechanical index of 0,06. The maximum temperature for the brush was 19,1 °C. The mechanical index was lower than the safety limit and the temperature of the toothbrush did not increase over normal human temperature. The ultrasonic toothbrush did not to cause more harm to the teeth or to other oral tissues because of the ultrasound.