Endodontic access

A considerable proportion of contemporary endodontic practice involves cutting access cavities through large composite or amalgam restorations, and various types of crown. The conventional air turbine handpiece (AT) is thus often tested to its limit. Slow progress and stalling lengthen what is often a difficult and technical procedure. The purpose of this article is to consider the features of an appropriately geared electrically driven handpiece as an alternative.

The Borden Airotor of 1957 produced speeds of up to 300,000rpm, but in common with successive developments lacked torque and was thus easily stalled when called upon to cut resistant materials such as crown alloys. The speed of an AT typically drops up to 40 per cent or more when contact occurs between the bur and material to be cut, as air pressure is insufficient to maintain the rotational speed of the turbine.

Speed increasing electric handpieces (EH) (red ring) are commonly available with a 5:1 increasing gear ratio, giving bur speeds of up to 200,000rpm, with micromotors running at between 1000 to 40,000rpm.