Electric

If there is one piece of equipment most feared by our patients, it is the dreaded drill, aka the handpiece. These devices are looked upon as implements of pain and suffering. Who can forget the torture scene in the movie Marathon Man? However, virtually every dentist would find it difficult to practice without these trusty instruments.

For patient treatment, handpieces can be primarily divided into two categories: highspeed and slowspeed. There are also handpieces dedicated for laboratory use. This category will cover electric-powered handpieces, most of which can be used at high, medium, and slow speeds.

While the air-powered, highspeed handpiece combined with an air-powered slowspeed remains the preeminent dynamic instrument duo in North America (75%-85% as estimated by several manufacturers), electric-powered handpieces have gained a strong foothold in other areas of the world such as Europe. Deciding between the two types of power generation should be first on your decision tree.

Note: Even though alternative preparation concepts such as air abrasion (fading) and hard tissue lasers (emerging) have their advocates, it is difficult to imagine that either of these technologies will replace your trusty handpiece in the near future.

Air vs. Electric

Yes for electric

The primary reason cited by proponents of electric handpieces is increased torque at lower speed, a combination that allows better control of the handpiece. A secondary reason is that the electric motor can usually be set to rotate at virtually any speed within its limits. This means that with one motor, you can operate at low, medium, and high speeds by merely changing the attachment and the setting on the control box, which provides a host of functions. Finally, since the power of the handpiece is provided by the onboard motor, its performance will not suffer if you are far away from the air compressor and/or other operators are using it at the same time.

No for electric

Size and weight are the two most often voiced complaints about electric handpieces. Especially among dentists suffering from repetitive use injuries such as carpal tunnel syndrome, the added heft of electrics can be a deal killer. When you consider the average weight of highspeed air handpieces being only 3.3oz/93.6g, the same average for electrics (motor + highspeed attachments) is a meaty 7.1oz/201.3g. However, the newest entries into the electric category weigh in around 5.0oz/140g. While this is still heavier than air-driven models, the gap is starting to shrink.

Others reasons for resisting the allure of electrics include the fact that at least some air-powered models cut as fast, although the average veneer cutting speed for air versions is 23 seconds compared to 20 seconds for the electrics. When it comes to noise, the average decibel rating for electrics is 70.2 compared to 70.7 for the air versions, which means they are virtually the same.

Installation of electrics is usually more complicated and involved compared to air-driven models. And, of course, the cost of electrics is still a stumbling block and is typically substantially more expensive than most air-driven models.

But then there is the hot issue of electrics burning patients. In a notice issued by the FDA on December 12, 2007, dental professionals were warned about serious patient injuries, including third degree burns, associated with the use of poorly maintained electric dental handpieces. The warning goes on to state this problem is not just associated with dentistry, since problems with handpieces used during orthopedic procedures was first reported in 2003.

The FDA further explained that unlike air-powered handpieces, which will typically stall out before they overheat, electrics will continue working even harder to overcome performance challenges, for example, as a result of poor maintenance. This working harder can rapidly generate heat that can burn a patient.

In a survey of the Editorial Team members, 11 out of 20 reported that they do not believe their electric handpieces even get hot during use. Another seven stated that they were aware of times when their electric handpieces became hot during use, but they were unaware of any patients being burned.

The last two reported that their handpieces did get hot, but each of them was only aware of burning just one patient during their early usage days. Neither has had a similar experience since that incident. The other 18 were somewhat amazed that this was even a problem. One response from a European dentist confirmed that this is just not a problem in the EU, while another reply was from a dentist who had been routinely using an electric handpiece for 15 years without it ever getting hot or burning a patient.

Then there was a recent article in a dental tabloid stating that the burning problem was handpiece specific and was caused by pressure on the push-button chuck when the handpiece, for example, is being used in the buccal corridor. If this pressure, presumably generated by facial muscles, is substantial, the push-button of the chuck could be depressed during the time the handpiece is activated.

To test this theory, we simulated the pressure that could conceivably be created by the facial muscles and activated four different brands of electric handpieces for one minute at 200,000 rpm using a clinically acceptable level of water spray. Since this was a simulation, the operator conducting the test did not wear gloves so as to better judge whether the handpiece became too hot to touch, a temperature of which could conceivably burn a patient. The results are in the commentaries for each handpiece. For those that did, indeed, get hot, we advise caution when using these handpieces in situations where pressure could be applied to the push-button chucks during use.

The survey and test suggest that a patient can be burned by an electric handpiece, but the instances can largely be mitigated by using a proper amount of water coolant, by properly maintaining the instrument, and by being aware of not applying pressure to the chuck while it is in operation. You should be aware of the problem, but it should not keep you from buying one of these instruments.

 

Hybrid Handpieces

To bridge the gap between conventional, air-powered and electric handpieces is a subcategory of the former. Dubbed as a hybrid, this type of handpiece is air-powered, but relies on a microprocessor to regulate the pressure going into the handpiece based on the task at hand. At this time, only one model has been introduced to the market (see Midwest ATC), but more may be on the way.

Various Items to Consider When Purchasing a Handpiece for Restorative Tasks

Light To measure the luminance of all the products, we placed a 330 bur in all highspeed attachments. We then activated the handpiece and placed it as close to the luminance sensor as we could without actually touching the sensor. These luminance figures may be significantly different than those reported by the manufacturer, but they are closer to what you would experience in the mouth. The light output of each product is included in its commentary.

Water Spray The number and position of the water ports contribute to the cooling capability of the handpiece, lubrication of the tooth structure, and cutting effectiveness through keeping the diamond or carbide bur as free from grinding debris as possible. While having water ports around the bur provides the best water spray, those sprays from ports below the bur can also work.

Push-Button Chuck Pushing a button on the back of the head of the handpiece is the easiest way to insert and remove a bur. Unless indicated, all the handpieces we evaluated have this type of chuck.

Noise Just the sound of a handpiece is enough to strike fear in many patients. And noisy handpieces are not good for your hearing either. To measure the noise generated by these products, we placed a 330 bur in all FG attachments. We then activated the handpiece and placed it as close to the audible sensor as we could without actually touching the sensor. However, the noise you and your patients are subjected to will typically be lower, since the handpiece would never be directly over your or the ear of the patient. Furthermore, regardless of the decibel rating, some handpieces just sound more shrill than others.

Weight Usually, lighter is better. We weighed all the handpieces with their attachments to get a real world value.

Size of the Handpiece The length was measured from the tubing connection, while the diameter was measured at the widest section. Slimmer, shorter handpieces would be more likely to be comfortable for operators with small hands.

Size of the Head Smaller heads can obviously access more areas in mouths of patients with restricted opening. They usually have less power than their full-size brethren, but this may or may not affect their speed in cutting preparations. Even if they are slightly slower, the slight reduction might be worth it for the additional access you can gain. But the length of a head may not tell the entire story, since burs may extend out of certain handpieces more than others, especially those designated as mini-head models. Therefore, we measured the length of all FG heads with a 330 bur and latch-type heads with a #4 bur in place.

Contamination Oil from handpieces has been implicated in contaminating your preparation and interfering with adhesion. To test this possibility, we exposed dentin specimens to five minutes of handpiece spray to simulate a crown preparation. The handpiece was run first to expel visible lubricant, just as you should do before using a freshly lubricated and autoclaved handpiece. No cleaning procedures were performed, since we did not want to introduce another variable. These specimens were then tested for bond strength. Here are the results:

Tooth MPa
Control 32.7
Contaminated 30.1

 

 

 

 

This test suggests that contamination from handpiece lubricant is a real possibility. Even though bond strengths only dropped slightly, these tests are run on flat teeth that could be scrutinized very closely for contamination. Clinically, we strongly suggest routine use of a cavity cleaner to remove any residual lubricant. In addition, do not use a handpiece if it continues to spray lubricant on teeth you are about to restore.

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