Rethinking the Dental Handpiece
David Little, DDS
Thanks to significant advances in design and manufacturing, dentists today can—and should—expect more from their high-speed handpieces. Recent technologic breakthroughs have improved the cutting experience, making it faster and easier for the dentist and more comfortable for the patient.
Where We Started and How Far We Have Come
Handpieces are among the most commonly used mechanical devices in dentistry. No longer the primitive cutting tools introduced in the 1800s, handpieces are now highly efficient and sophisticated after a slow evolutionary process with incremental changes. Traditional handpieces are either air-driven or electrically driven.
In 1871, the first commercial foot-treadle dental engine, or drill, was manufactured after James B. Morrison received the patent.1 About 50 years ago, dentists used belt-driven (belt and pulley) handpieces to cut teeth. At first, only straight handpieces were available, proving to be slow and laborious for the dentist and uncomfortable for the patient.
In the late 1940s, John Patrick Walsh of New Zealand introduced a high-speed air-driven handpiece. In the 1950s, John Borden introduced in the United States the Borden handpiece, or Airotor, which incorporated a contra-angle design.
The other traditional kind of handpiece is electrically driven, with the first model patented in the 1870s. These early devices were heavy and bulky, producing poor ergonomics for the clinician.
Handpieces have evolved with the practice of dentistry and dental technology. High-speed electric handpieces now have a speed of 200,000 revolutions per minute (rpm), while high-speed air-driven devices function at up to 400,000 rpm and usually operate within 180,000 rpm to 330,000 rpm.
Often, head sizes have been reduced to provide better visibility and access. Fiber-optic lighting was first integrated into handpieces in the 1970s and has dramatically improved the dentist's ability to see the work area. Turbine cartridges have been steadily improved to enhance longevity and reduce noise. New bearing configurations and materials have been developed. Innovative materials have made it possible to repeatedly sterilize the handpiece without degradation in looks or performance. Chucking mechanisms have been improved with pushbutton releases to facilitate insertion and removal of the rotary instrument. Ergonomic improvements have made handpieces more comfortable and less tiring for the dentist. Ergonomically, the handpiece should help with seeing the working area; offer a head size and length that maximizes access and visibility at the location; provide a weight, configuration, and grip that is comfortable for the dentist and minimizes his or her fatigue; create low noise; and produce no vibration (which also avoids hand—arm vibration syndrome in the clinician).2
Electric vs. Air-driven: A Comparison
The electric and air-driven handpieces each have unique characteristics and benefits. We will talk briefly about the latest technologies and developments.
Electric: Electrically driven handpieces use a simple electrical supply to power the motor through a control unit. They operate at a minimum of 20 rpm and up to 200,000 rpm, depending on the specific handpiece and attachments used. Given the speed variations that can be obtained with motor attachments, a single electric handpiece can be employed for all high-speed (restorative and endodontic access) and low-speed procedures (restorative, hygienic, endodontic, surgical, and laboratory). However, air and water are still necessary for proper cooling and irrigation.
When using an electric handpiece, the dentist must ensure that the handpiece head ("back cap area") does not overheat. Cases have been reported of patient burns, including third-degree, which have been linked to overheating of the electric handpiece head.3 The weight and configuration of the typical electric handpiece can be fatiguing during a long day. Newer electrics have been streamlined to reduce weight and drag and to improve ergonomics.
One of the benefits of an electric versus a typical air-driven handpiece has been its constant torque even under demanding loads, creating better cutting performance.
Air-driven: Traditional air-driven high-speed handpieces rely on an air-driven turbine to rotate the rotary cutting instrument. High speeds can be attained; however, the bur can slow when under heavy loads, reducing cutting ability. Past efforts to increase torque by increasing turbine size and head size have created obvious disadvantages.
What is New on the Market?
A technology has been introduced that many in the profession believe is a breakthrough. Called Speed-Sensing Intelligence, it actually monitors the bur speed several hundred times per second. A sensor in the coupler detects the frequency of vibrations from the rotating bur. When the bur encounters a higher load that would normally decrease speed, a signal from a small chip in the control source increases air pressure to maintain speed, virtually eliminating stalling to provide a smooth, consistent cutting speed regardless of load. This design provides exceptionally fast removal of tooth structure, amalgam, porcelain, and metal. Because the system adjusts speed when the bur is not under load, wear on bearings is minimized, which means fewer turbine replacements.
Another technology, Superior Turbine Suspension, allows the handpiece to operate at 330,000 rpm under load, with no noticeable bur deflection or chattering. This provides control and a consistent transference of power from the handpiece to the bur, helping overall cutting efficiency. It is especially beneficial for margin refinements, veneer preparations, and other fine restorative procedures.
One manufacturer is featuring new "Plug-n-Prep" auto-calibration technology. Because it does not require adjustment to other equipment, this system offers a simplified setup and a seamless transition. Once calibrated, this system allows for an air-like "feathering" effect between 30,000 rpm to 200,000 rpm with the foot pedal.
Significant advances are also emerging with light-emitting diodes (LEDs), which will be able to provide better intraoral illumination and a longer bulb life. These bulbs offer energy-efficient options for handpieces to switch to a cool-white LED light source with a neutral daylight color, which often lasts up to 10 times longer than a halogen bulb.
In addition, new designs are improving handpiece head size and ergonomics to maximize the field of view in the mouth. These handpieces are becoming significantly smaller and lighter, increasing practice efficiency and patient comfort. Smaller head sizes allow for greater visibility and access. Advanced ergonomic engineering provides less stress and fatigue, as well as better maneuverability and control.
Rethinking Your Expectations
Until just a few years ago, handpiece technology had changed little. Recently, major advances in technology and manufacturing have challenged dental professionals to revisit their choice of handpieces. This will not only help make our work more precise but will also improve the patient experience. Exploring options and thinking outside the box when it comes to handpiece selection is crucial in this day and age.
Although major progress with high-speed devices has been made recently, we still have challenges. Undoubtedly, more changes are coming, and we can look forward to the developments in this area.
1. American Dental Association Web site. ADA Timeline. http://www.ada.org/adatimeline.aspx. Accessed September 23, 2010.
2. Poole RL, Lea SC, Dyson JE, et al. Vibration characteristics of dental high-speed turbines and speed-increasing handpieces. J Dent. 2008;36(7):488-493.
3. US Food and Drug Administration Web site. FDA Public Health Notification: Patient Burns from Electric Dental Handpieces. December 12, 2007. Available at: http://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/PublicHealthNotifications/UCM062018 Accessed September 23, 2010.
About the Author
David Little, DDS
San Antonio, Texas