With internal, precision components being subjected to 250,000+ rotations per minute, dental handpieces are a challenge to maintain optimum performance over an extended period of time. Internal handpiece components that “fail” the most, or quickest, are one of the handpiece’s two bearings, located within the spinning portion of the head of the device.
So what causes dental handpiece bearing failures: 1. High temperatures during dental autoclave sterilizer work.
2. Use of excessive air pressure of the handpiece
3. Build up of debris within the bearing cage
It has been proven, side load pressure will have a greater impact on the rear bearing of the handpiece than the front bearing. For those who attempt to repair their own handpieces, take a moment to compare the front bearing condition to the rear bearing. If the rear bearing is shot, well, you can do better letting the bur do what it is supposed to.
Bent burs, or burs that are not properly seated within the handpiece turbine are bearing killers. “A bur not to spec will keep your bearings in check.”
Be sure a bur inserted is fully seated within the handpiece’s chuck. Side load proportionally increases bearing stresses with improper internal bur placement. It also affects the operating weight displacement of the handpiece turbine while spinning. This will contribute to handpiece chuck failure. Look out for dropped or flying burs!
Excessive temperature is another bearing enemy that is not always evident. All dental handpieces are made to be heat sterilized in accordance with the CDC standards. They should be sterilized in a steam or chemical vapor sterilizer at a maximum of 275° F (135° C). Never use dry heat sterilizers for your handpieces, period!
Don’t forget what “high” air pressure psi does to handpiece bearings … Most manufacturers recommend running their handpieces at about 35 psi (for highspeeds). Generally, anything in excess of 40 psi will cause damage to handpiece bearings. Take a few moments to review the handpiece manufacturer’s operational specifications.
Debris causes premature bearing failure. Metal bearing side shields were mentioned above … they are supposed to keep internal bearing components clean, well, they don’t. Debris will eventually buildup inside of the bearing enclosure, one way or another. Also, debris accumulation on the outside of the bearing assembly causes turbine operation imbalance, putting various stresses throughout bearing cage. Do what you can to maintain a program of frequently purging and cleaning your handpieces to maximize handpiece bearing life.
In a word, Dental handpiece repair is inevitable. With so many moving parts moving so fast, with stresses coming from all directions, within environments that are moist, debris filled and temperature inconsistent, simple mechanical physics lead to problematic operational outcomes. Bearings represent the most vulnerable components within a dental handpiece. With two bearings operating within your typical device, the odds of handpiece failure are definite.