Noise level evaluation of dental handpieces.

We evaluated the noise level of fourteen air-driven handpieces, six low speed (less than 20,000 rev/min) and eight high speed (greater than 160,000 rev/min), with respect to a three-directional co-ordinate system and distances of 6, 12 and 18 in. in each chosen direction. A two-way analysis of variance of the noise level between handpieces and positions indicates that large significant differences exist amongst handpieces and in different positions, and that interaction is just barely significant. The ranking and least significant differences for the mean of all handpieces v. position and for the mean of all positions v. handpiece were compared with the results for the ranking and significances from the one-way ANOVAS for each handpiece v. position and for each position v. handpiece. A trend exists with some of the handpieces of straight design (all low speed) for increased noise levels in a direction perpendicular to the handpieces and decreased levels in a direction parallel to the handpieces. For handpieces of angled design (all high speed) both directions parallel and perpendicular (the perpendicular to the longitudinal turbine axis) to the rotor axis indicate increased noise levels. The parallel direction includes the exiting air from the exhaust port. The perpendicular direction can be indicative of an aerodynamic factor associated with the established air flow patterns. The extremes in noise level were 56.8 dBA for a low-speed handpiece of straight design at the 18 in. distance in a direction parallel to the handpiece, and 87.3 dBA for a high speed handpiece at the 6 in. distance in a perpendicular direction.