Advantages of Electric-Driven Handpieces During Tooth Preparation

As amalgam restorations break down and need to be replaced, composite restorations are becoming the restoration of choice for many dental practices. For composite restorations to be a viable alternative to amalgam, the restorations must be placed in a similar amount of treatment time. This places increased demands on the restorative dentist to be able to place bonded restorations adequately in an efficient amount of time in order to keep the practice profitable and fit into the patients busy schedule. Many technological advances have been made in recent years to allow the dentist to place bonded restorations easily and efficiently while still achieving long-lasting restorations. One of the most cost-effective advances is electric handpieces.

This article presents a case report in which a defective amalgam restoration was replaced with a composite restoration using a variety of technologies and materials, including electric handpieces.


Figure 1. Preoperative photo showing failing amalgam.

During a hygiene appointment, digital radiographs (SIDEXIS system, Sirona) as well as digital photographs (Canon 20D) were taken of the patients existing dental restorations. Evaluation with the use of Image FX software (SciCan) revealed recurrent decay around the amalgam restoration on tooth No. 19. It was decided by both the author and the patient to restore the tooth with a composite restoration (Figure 1).

After the gingival tissue in the vestibule adjacent to the tooth was anesthetized with TAC Topical Gel (Professional Arts Pharmacy), which is a combination of tetracaine, benzocaine, and lidocaine, the tooth was anesthetized with 1 carpule of Citanest Plain (DENTSPLY) followed by 1 carpule of Septocaine (Septodont). The arch was then isolated with a rubber dam and W3 clamp. Isolation with a rubber dam provides several advantages. By keeping the preparation free of saliva and moisture from the patients exhaled breath, a superior bond can be achieved compared to not using a rubber dam. The dam also provides constant retraction of the lips and tongue, allowing the clinician and assistant to work with much greater efficiency. The author used dental magnification loupes for the procedure (Orascoptic, Kerr/Sybron). The loupes provide an enhanced view of the tooth, which allows the clinician to see and remove pathology with greater accuracy.

Electric handpieces (KaVo high- and low-speed electric handpieces, KaVo) and diamond burs (Axis Dental) were then used to remove the amalgam. Compared to air-driven handpieces, electric-driven handpieces provide constant torque and speed while cutting. Air-driven handpieces typically turn at more than 360,000 rpm. The downside of air-driven handpieces is the variance in their cutting speeds and the loss of power when force is applied. Their speed drops to about 200,000 rpm when the bur meets resistance during cutting. Variance in cutting speed can also be attributed to the amount of air pressure entering the drill and the type of cutting surface, which can be enamel, dentin, amalgam, porcelain, etc. All of these different substrates can produce different resistances and thus different cutting speeds.

Figure 2. Removal of amalgam with diamond bur.

Electric-driven handpieces maintain a constant cutting speed and torque, which is determined by the operator regardless of the material being cut. The downside of electric handpieces is that they are slightly heavier than air high-speeds. However, the weight is balanced, and the user gets accustomed to the different weight quickly. The control unit for the electric handpiece is connected to a standard, 4-hole air line. The air is used to activate the electric motor and to atomize the water spray during cutting. The use of an existing air line enables the operator to use the existing foot control. Electric handpieces consist of an electric motor and separate attachments, which are all gear-driven and are available with various speed transmission options. The author uses the ELECTRO-torque plus brushless electric motor system and the 25LPA electric high-speed attachment (KaVo). The 25LPA increases the motor speed by a factor of 5. This means that if the motor speed is set to 40 on the control box (corresponds to 40,000 rpm), the high-speed attachment increases the speed to 200,000 rpm at the bur (5 x 40,000). This speed remains constant if the rheostat is fully depressed due to the high torque, regardless of what the operator is cutting. The diamond bur used was an 813 Amalgam Removal Diamond (Axis Dental,  Figure 2).


Figure 3. Removal of gross decay with large round bur.

After the amalgam restoration was removed with the electric-driven high-speed attachment and a diamond bur, the recurrent decay was removed with an electric-driven slow-speed attachment (7LP KaVo slow-speed attachment, KaVo) and a No. 4 latch-type round bur (Axis Dental). The 7LP attachment reduces the motor speed by a 2.7-to-1 factor. This means that if the motor speed is set to 20 (which corresponds to 20,000 rpm), then the bur will run at 7,407 rpm. This allows the clinician to remove decayed tooth structure easily while removing very little solid dentin or enamel. Another advantage is the fiber-optic light and water spray on the slow-speed attachment. This is the same configuration as on the high-speed attachment. Both the light and water spray greatly improve the efficiency of tooth preparation (Figure 3).


Figure 4. Removal of small pits with diamond bur.

The author prefers to conserve as much healthy tooth structure as possible by removing small decayed pits and cracks in the tooth with an 801 diamond (Axis Dental) and the electric-driven high-speed at-tachment. This removes only the unhealthy parts of the tooth as opposed to amalgam restorations, which demand removal of healthy tooth structure for resistance to displacement and fracture (Figure 4).




The tooth was then restored with a nanofilled composite restoration (Premise, Kerr/Sy-bron). The preparation was etched with 37% phosphoric acid, rewet with Tubulicid (Global Dental Products), and primed with multiple coats of OptiBond primer/bonding agent (Kerr/Sybron). A layer of A3 dentin shade was placed and cured for 40 seconds with an L.E.Demetron 1 curing light (Kerr/Sybron). A final layer of Enamel Clear (Kerr/Sybron) was placed and cured.

Figure 5. Finishing margins with carbide bur.

Once the final layer was cured, the margins of the composite restoration were refined using a carbide bur and high-speed electric attachment. The composite resin was sculpted as closely to the final anatomy as possible by following the contours of the existing enamel cusp before being cured. By following the existing contours, only minimal refinement of the restoration was required. A No. 303 carbide bur (Axis Dental) was used. The bur was held at the same angle as the existing cusp, with the tip following the central and marginal groove (Figure 5).


Figure 6. Polishing with rubber points.

The margins of the restorations were refined and flush with the edges of the preparation. Then the composite restoration was polished using a PDQ One Step Polishing Point (Axis Dental), with the electric slow-speed attachment at a motor speed of 20 (this will correspond to a bur speed of 3,700 rpm). Because of the high torque of the electric drills, the rubber polishing point does not skim over the composite restoration but smoothes the surface in a very short amount of time (Figure 6).



Figure 7. Polishing grooves and anatomy with bristle cups.

Once the margins were polished, the PDQ was replaced in the slow-speed attachment with a PDQ Polishing Cup (Axis Dental). The bristles of the polishing cup are capable of cleaning out the grooves and anatomy of the restoration without over polishing and removing too much of the restoration or ditching the margins. Light pressure was used for just a few seconds while angling the cup in all directions to create a polished glaze to the restoration. The newer generation composites along with the latest polishing cups/points coupled with electric handpieces can be polished is less than a minute (Figure 7).


Figure 8. Final restoration.

The rubber dam was then removed, and the occlusion was examined and adjusted where needed. Because the composite restoration was created with the final anatomy in mind, it was not overfilled. This requires very little occlusal adjustment, if any (Figure 8).


With the help and advantages of new technology, especially electric-driven handpieces, composite restorations can be placed faster and easier. The use of digital cameras and digital radiography has made diagnosing and treatment planning fast and simple. Presenting treatment options to patients with software such as Image FX takes case presentation to a new level. But getting the patient to agree to treatment is only beneficial to a dental practice if the services can be performed in a timely and efficient manner. The use of magnification, nanofilled composites, electric-driven handpieces, and one-step polishers allows the dentist to restore teeth quickly, which benefits both the dentists bottom line and the patients busy schedule.

Dr. Soileau is a general dentist from Lafayette, La. His practice focuses on restorative rehabilitation and cosmetic enhancements. He lectures nationally and internationally on the use of digital photography and computer assistance for diagnosing, treatment planning, and performing comprehensive dental procedures. He is a consultant for several technologies-based dental manufacturers and beta tests many of their products. When Dr. Soileau is not lecturing, he is a consultant to several pageant coaches throughout the country. He has judged and worked with local and national Miss USA, Miss Teen USA, Miss America, and Mrs. America contestants. He is co-director of digital photography for GenR8TNext digital photography courses and has taught digital photography at the Institute of Oral Art and Design (IOAD) in Tampa, Fla, and the Pacific Aesthetic Continuum (PAC~Live) in San Francisco. His dental and photography skills can be seen at He can be reached at (337) 234-3551 or This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

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