Practice Tips #91: Failed Turbines

A failing handpiece can be due to several factors. After diagnosis, a failed turbine is often the culprit. There are several reasons why a turbine may fail. Below are some of the most common causes:

1. Incorrect Air Pressure. The air pressure from the junction box into the dental unit needs to be set at 80psi. The drive air pressure from your dental unit going into the handpiece should be set between 35psi and 40psi (37psi is a good pressure setting). If you do not know what your drive air pressure is, you can find out using a handpiece pressure gauge. See more in Practice Tip #23.
   
2. Improper Handling. Dropping your handpiece, especially on a hard surface can cause dents to appear in the head of your handpiece. These dents point inward into the cavity where the turbine is seated. When the turbine spins, the impeller will hit these dents causing damage to the impeller as the dents act like speed bumps and in turn will cause the bearings to go out of alignment. Some dents can be removed using a cavity reamer. See more in Practice Tip #40.
   
3. Poor Handpiece Maintenance. If the handpiece is not flushed clean before sterilization, the debris that has built up in the cavity will harden and can prevent the turbine from spinning properly. You still need to flush and sterilize your handpiece after every use. See more in Practice Tip #45.

    

   

   Handpieces are shown connected to a handpiece lubrication system.

4. Excessive Side Load. Excessive side load usually happens during crown preparation. When doing a crown prep, make sure you use a fresh bur (diamond burs are normally better suited than carbides). If you use a dull bur while doing a crown prep, the bur will not cut properly and the excessive pressure put on the bur will cause the rear bearing on the turbine to fail. Let the bur do the cutting -- minimal pressure should be applied. If you find that extra pressure is needed to get the bur to cut, you need to change burs, as this is a sign that the bur has become dull. See more in Practice Tip #66.

    

   

   Notice that the old bur (one on top) looks worn and dull, while the new bur (one on the bottom) looks coarse.

Your dental handpiece is one of your most utilized instruments in the office and will need some TLC every day. Improper use and poor maintenance can lead to expensive repairs or total handpiece replacements later down the road. Hopefully, these tips will assist you in limiting premature turbine failures in the future.