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A survey of interfacial forces used during endosonic instrumentation of root canals
J D Regan1, M Sherriff, N Meredith
1Eastman Dental Institute for Oral Health Care Sciences, University College London, London, 256 Gray's Inn Road, London, WC1X 8LD, England.
Aim:
The aim of this in-vitro study was to measure interfacial forces acting between root canal dentine and ultrasonic files during endosonic instrumentation.
Methodology:
Single-rooted teeth were mounted on a cantilevered aluminium beam to which two pairs of single element strain gauges were joined in a half-bridge configuration mounted at right angles to each other. The strain gauges were connected to an analogue-to-digital converter fitted in a microcomputer via a conditioning amplifier. This enabled strains to be recorded as a function of interfacial forces over a period of time. Twenty operators instrumented root canals using sizes 15, 20 and 25 ultrasonically energized K-type files. The lateral forces generated were calculated.
Results:
The mean interfacial forces used varied widely between operators and files, ranging from 18 g to 149 g, but there was a consistency in the relative magnitude for each operator. The average force used by the operators increased with file size; the differences between file sizes were significant (P < 0.05).
Conclusions:
The range of forces measured is broader than previously reported and may have a bearing on possible uncontrolled dentine removal, even during ultrasonically activated irrigation.