Comparative study of manual and ultrasonic instrumentation of cementum surfaces: influence of lateral pressure.

The goal of periodontal treatments is to eliminate bacteria and their products without damaging cementum surfaces. Nonsurgical treatments are often limited by the inability of curettes to access the most apical zone of the pocket. While ultrasonic mini-inserts have been used for nearly 10 years now, their effect on dental tissues has not been tested. The purpose of the present study was to compare a new series of mini-inserts to Gracey curettes, which are the reference in nonsurgical treatments. Two experienced periodontists conducted root treatments on teeth destined for extraction using regular clinical criteria. One face of each root was instrumented using a Gracey curette, and the opposite face was instrumented using an ultrasonic mini-insert. After the instrumentation procedure, the teeth were prepared for examination by secondary electron (topographic features) and backscattered electron (organic and mineral composition) microscopy. Differences in surface composition between teeth treated by the two periodontists were noted and were related to the lateral pressure exerted. Calculus removal was less effective when strong lateral pressure was exerted using the ultrasonic mini-inserts, while more cementum was removed and more scratching occurred with both manual and ultrasonic instruments. In all cases, the ultrasonic mini-inserts allowed greater apical access. The new ultrasonic mini-inserts were as effective as manual curettes in eliminating plaque and calculus. The shape of the mini-inserts made them more effective in apical zones. The amount of damage to the cementum depended on the lateral pressure exerted by the periodontist.