What you should know about high speed electric handpieces
By: Phil Leinbach, President of Florida Dental Repair
On:
Electric high speed handpieces are a great innovation. Unlike the air driven highspeed, they offer infinite torque over the entire RPM range of the handpiece. This allows the dentist to reduce chair time per patient and make more money.
The downside is the initial and maintenance costs are high. A typical factory rebuild could easily be over $500. Almost all of the parts are proprietary and manufacturers do not openly sell these parts which makes it very expensive for the independent dealers like us to get parts and repair these handpieces. Because of this, it is difficult for Independents to compete with factory repair centers on a major rebuild.
When the manufacturer rebuilds one of these handpieces they unconditionally replace the spindle cartridge and drive shaft assemblies even if only one bearing is bad. We independents can do a minor rebuild that involves replacing just the bearings and water line seals for a much lower cost. This gives the customer a good value by extending the time before a major rebuild is required. In order to do that, we have set guidelines for determining what gears can be reused and which ones must be replaced.
Why do gears go bad? Usually because dentists continue to use there handpieces after the bearings have gone bad and/or they use of burrs that are too course. If the shafts rotate on their correct axis the wear to a gear is minimal since the geometry of that gear is designed for that axis. Under ideal conditions, when the teeth of gears mesh, they push against one another and do not rub. When a bearing wears the shaft no longer rotates on its correct axis which causes gears to rub against each other and hastens their demise. Coarse burrs cause excess vibration which is not a problem in air driven highspeed handpieces because of feathering, but in the electric highspeed the added torque available allows the dentist to keep the burr in constant contact with the tooth surface. The vibration caused by the coarse burr is transmitted directly back to the bearings.
Another way to help your customer extend the life of their electric highspeed is to make sure they have enough drive air pressure. The drive air is not used to drive the handpiece but it is used to cool the motor and the attachment. It is always best to consult the manufacturer's recommendation before setting the drive air pressure. Some manufacturers sell a flow-meter that attaches to the handpiece for setting the drive air pressure. This is the most accurate way to set the pressure because it is air flow that provides the cooling. We recommend having at least 65psi at the dental unit.
The following pictures show the life span of a gear and what is deemed usable and unusable. 
