VARIATIONS IN STROKE RATE AND LOADING USING HAND SONIC OR ULTRASONIC INSTRUMENTATION

An in vitro model system was developed to investigate the stroke rate and loading during hand, sonic, or ultrasonic instrumentation. The mod el system consisted of a mandibular molar tooth attached to a strain g auge and interface to a computer. Ten clinicians instrumented the dist al canal of lower molar teeth. Stroke rates used and loads applied wer e measured using different sized files with the three different prepar ation techniques. There was no significant difference in stroke rates between different file sizes (p > 0.05) within the same generator, how ever, stroke rate for hand was significantly slower than for sonic or ultrasonic (p < 0.01). Loading of the canal wall rose with increase in file size which was significant for hand (p < 0.01) and sonic (p < 0. 05) but not ultrasonic (p > 0.05). There was a tendency for loading to be higher with hand instrumentation, this however was not significant (p > 0.05).