Inside Dentistry
March 2006
Volume 2, Issue 2

Comparison of Cavity Preparation Quality Using an Electric Motor Handpiece and an air Turbine Handpiece

Howard E. Strassler, DMD

Kenyon BJ, van Zyl I, Louie KG. J Am Dent Assoc. 2005 Aug;136(8):1101-1105.


BACKGROUND: The high-speed high-torque (electric motor) handpiece is becoming more popular in dental offices and laboratories in the United States. It is reported to cut more precisely and to assist in the creation of finer margins that enhance cavity preparations. The authors conducted an in vitro study to compare the quality of cavity preparations fabricated with a high-speed high-torque (electric motor) handpiece and a high-speed low-torque (air turbine) handpiece. METHODS: Eighty-six dental students each cut two Class I preparations, one with an air turbine handpiece and the other with an electric motor high-speed handpiece. The authors asked the students to cut each preparation accurately toa circular outline and to establish a flat pulpal floor with 1.5 millimeters’ depth, 90-degree exit angles, parallel vertical walls and sharp internal line angles, as well as to refine the preparation to achieve flat, smooth walls with a well-definedcavosurface margin. A single faculty member scored the preparations for criteria and refinement using a nine-point scale (range, 1-9). The authors analyzed the data statistically using paired t tests. RESULTS: In preparation criteria, theelectric motor high-speed handpiece had a higher average grade than did the air turbine handpiece (5.07 and 4.90, respectively). For refinement, the average grade for the air turbine high-speed handpiece was greater than that for theelectric motor high-speed handpiece (5.72 and 5.52, respectively). The differences were not statistically significant. CLINICAL IMPLICATIONS: The electric motor high-speed handpiece performed as well as, but not better than, the airturbine handpiece in the fabrication of high-quality cavity preparations.


Ergonomic use of dental instruments combined with efficient and effective instrumentation when performing cavity preparations has always been the goal of clinical dentistry. In recent years, manufacturers have introduced electric motor high-speed handpieces with many claims including improved tactile response, more concentric cutting performance, less atomization of airborne pathogens, and increased longevity. The current air-turbine high-speed handpieces have the disadvantage of low torque leading to loss of speed and stalling of the bur or diamond when moderate loads are applied. Electric high-speed handpieces with their high-torque characterisitics supposedly eliminate these problems.

The authors of the article provide insight into whether or not electric high-speed high-torque handpieces offer advantages over the current high-speed low-torque air turbines. The design of the research eliminates the long-term experiences of a dental practitioner and his or her ability to compensate for the pluses and minuses of any given handpiece by using novices (dental students) to perform the cavity preparations, each in a 5-minute period of time. Based on the results, there were no significant differences between the handpieces used. However, one must consider his or her own clinical practice. In my experience for routine operative dentistry preparations, I can achieve excellent results with both types of handpieces. But, for crown and bridge preparations, I prefer the efficiency of an electric motor high-speed high-torque handpiece. A practitioner should try both handpieces to make a decision on which he or she is better suited. With either choice, a clinician cannot go wrong based upon this study.

About the Author
Howard E. Strassler, DMD
Professor and Director of Operative Dentistry
Department of Endodontics, Prosthodontics and Operative Dentistry
University of Maryland Dental School, Baltimore,Maryland

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