A pilot study of measurement of the frequency of sounds emitted by high-speed dental air turbines.

Since the development and use of the high-speed dental air turbine some 45 years ago, concern has been expressed in the literature about a possible cause and effect relationship between use of the drill and hearing loss in dentists. The hearing threshold in humans varies with the frequency of sound. It is well known that dentists experience gradual hearing loss during their working life. The aim of this study was to measure the frequency of sounds emitted by high-speed dental air turbines under different working conditions. Five high-speed dental air turbines were used (2 x Trend TC-80 BC W&H Dentalwerk, Austria, 2 x Black Pearl Eco Bien-air, Switzerland, 1 x Trend TC-80 BC W&H Dentalwerk, Austria. Each turbine was tested under 8 different working conditions: under free working conditions the turbines were tested without burs, with fissure burs, with flare burs, with round burs and with inverted cone burs; under operation they were tested with fissure burs by application to a 3 x 3 x 10 mm amalgam block surface, a 3 x 3 x 10 mm composite block surface, and the occlusal surface of an extracted molar tooth. Forty sound recordings were made in total using a computer with a microphone (Shure 16 LC) located 30 cm away from the samples, at 10-s intervals using a mixer. Frequency analysis was done by a Cool Edit Pro 1.2 computer program. Data were analyzed by multi-variate analysis with the S.P.S.S 9.05 software program. The average measurement was 6860 Hz. According to the statistical analysis there was no significant difference in the frequencies recorded under different working conditions. There was also no significant difference among the different high-speed dental air turbines at alpha = 0,05, P > alpha /2 levels. These results indicate that under any working conditions, high-speed dental air turbines emit frequencies which can cause hearing loss.