Major Causes of Handpiece Failure

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Dental handpieces have many reasons for failure but most common that we see as a repair facility can be prevented if proper care and understanding of the instrument is used.

These are:

1. Sterilization
2. Lack of lubrication or proper lubrication
3. Being dropped
4. Ran with a bent bur or no bur at all
5. Using the wrong handpiece for the job

Handpieces must be purged of any debris prior to sterilization. The debris may become hard or gummy after the sterilization process. This will dramatically affect the bearings performance and consequently the handpiece life.

Bearings are made of an inner race, outer race, retainer cage and 7 to 8 solid ball bearings. Each ball is about the size of a pen tip. The bearing balls ride on a grooved surface between the inner and outer raceways. The retainer keeps the balls equally spaced as they rotate around the inner race.

The ball bearings spin between 350,000-400,000 rpm which is needed for the handpiece to function properly. It is easy to see that any small amount of foreign substance inside the bearing will dramatically affect its ability to perform.

• When air pressure exceeds the recommended settings of 32-35psi, the bearing will turn greater than 350,000-420,000 rpms that they are rated for. When this happens ball bearings that are held equally spaced by the retainer will start to oval the retainer holes. Eventually one hole will meet the next hole and so on until the retainer will break in half for a complete bearing failure.
• If heavy side pressure on the handpiece is used it will cause the bearing balls to roll vertically in the retainer. The holes will enlarge causing increased radial play of the bur.
• When handpieces are repeatedly over sterilized and or sterilizer is not temperature calibrated correctly the excessive heat will cause the retainers to creak on top part of the ball hole at the weakest point this will also cause the bearing to fail.
• If a bur is bent and is used it will cause the bearings to run out of concentricity. It is similar to a tire being out of balance. This will also cause the bearing balls to roll vertically leading to failure. Running without a bur may cause the chuck to back out into the cap.
• If a handpiece is dropped, the head may become dented. The dent will put pressure on the o-rings and bearings. If the dent is severe enough the bearings may become squeezed and also lead to premature failure.
• Handpieces must always have a backend gasket and swivel styles must have good pliable O-rings. If a good seal is not made, either air or water will find the path of least resistance and flow where it is not supposed to causing poor performance.

Using the correct handpiece for the job at hand is important. The use of torque style (Large head) handpieces should be used for heavy cutting when needed. Small heads should be used for lighter applications.

It’s not recommended to extend the bur due the chance it may walk out of the handpiece. 

How to Properly Lubricate Your Handpieces

Heads & Prophy Angles

Take them apart and lube the top, middle and bottom. Re-install. We recommend adding lubricate 2-3 times per week based on use.

Sheath & Contra Angles

Lubricate the top and bottom with 1-2 drops of oil. Sheaths do not have to be oiled every day. We recommend adding oil 2-3 times per week based on use.

Low Speed Lubrication

Lubricate air intake with 2-3 drops of oil after each use. Never autoclave a detachable motor.

Highspeed Lubrication

Lubricate air intake with 2-3 drops of oil. Add one drop into the chuck also. Highspeeds should be lubricated every time before use. Be sure to expel excess lubricant before you put them into the autoclave.

Always clean the surface with alcohol (Do not use harsh cleaners, or ultrasonic cleaner)

Common Handpiece Maintenance Mistakes

1. Using a chemical wipe –down on handpieces before sterilizing: This may cause harmful reactions when the handpiece is subject to heat.
2. Using an ultrasonic cleaner: Handpieces should never be immersed in any fluids.
3. Lubricating in the wrong hole. The drive airline leads directly to the turbine.
4. Not applying enough lubricant- It is important to ensure oil is getting to the bearings, by seeing oil leave the handpiece.
5. Not running the handpiece prior to autoclaving-failure to operate the handpiece following lubrication will gum up the turbine and excess oil gets baked into the bearings.
6. Leaving the bur in the chuck during autoclaving-This shorten the life of the auto chuck and will lead to build up of debris in the chuck.
7. Failing to maintain autoclaves-If the autoclave is not properly cleaned, buildup can occur that contaminates the entire system, including the handpiece.

Handpieces are precision instruments but will not last forever. They will wear out over time. If proper care and regular maintenance are preformed they should provide several years of excellent service.