Selection of contra-angle handpieces

How large must the selection of various straight and contra-angle handpieces be in a dental practice?

Air or electric motors are used as drive units for straight and contra-angle handpieces in the dental practice, and these require various step-down contra-angles as a result of the variously high drive speeds. Electric motors allow a narrower choice of contra-angles, since the speed range of these motors is considerably wider than with air motors.

With air motors, it is essential to use turbines for cavity preparations. With electric motors, preparation can be carried out with a 1:5 step-up ratio. This allows a speed of 200,000 rpm with a higher torque than can be achieved with a turbine.