Internal contamination of air-driven low-speed handpieces and attached prophy angles

Background. In an in vitro crossover study, the authors investigated whether the interior of low-speed handpiece/prophy-angle systems becomes contaminated during operation and submersion into Geobacillus stearothermophilus. Methods. This study involves two types of handpieces attached to eight brands of prophy angles. The researches operated angles attached to sterile handpieces for 60 seconds. They then analysed the inside surfaces of the angle, nosecone and motor. They tested each prophy angle and handpiece 10 times. Results. In the 160 tests of handpieces contaminated at the prophy cup end, the spores travelled into the motor gears 32 times (20 percent). In the other 160 tests in which the motor gears were contaminated, the test bacterium travelled through the prophy cup in 75 instances (47 percent). Conclusions. The in vitro data suggest that low-speed handpiece motors can become contaminated internally during use with prophy angles. Also, internal contaminants appear to have been released from the handpiece. Clinical Implications. The results suggest that low-speed handpieces can become contaminated internally during use. Unless low-speed handpieces are sterilized properly between patients, they may become cross-contaminated.