Contamination of Newly Designed Combined Nosecone and Prophy Angle System

Objectives: The purpose of this study was to determine if the interior of a newly designed disposable combined nosecone and prophy angle (esa ^TM) system becomes contaminated during operation. Methods: Forty disposable esa ^TM angles were attached to forty sterilized slow-speed motors. The prophy angles with attached motor were covered with plastic sleeves. Angle heads were submerged into 12.5 mL of 2.0 x 10⁶/mL Geobacillus stearothermophilus in 10% sheep's blood. Rotating angle cups were then pressed against the beaker sides and released. The process was repeated 30 times within 60 seconds. Handpiece components were aseptically disassembled and the inside surfaces of the angle/nosecone, the gears, and the motor were sampled and aerobically incubated in TSB containing 0.25% glucose at 56^oC for 7 days. The process was tested in reverse when 0.1 mL of the spore-blood suspensions was inoculated onto the gears of sterilized motors. Rotating angle cups were submerged in beakers containing 12.5 mL of sterile phosphate buffered saline (PBS). Operation was as previously described. The PBS, the inside of the angle and nosecone, the gears of the nosecone and motor were sampled for contamination. Both methods were tested forty times. Results: In the 40 tests of handpieces contaminated at the prophy cup end, the spores traveled up and inside the motor gears 10 times (25%). In the other 40 tests where the motor gears were contaminated, the test bacterium traveled down inside to the prophy cup and out in 21 instances (52%). Conclusions: These data suggest that slow-speed handpiece motors can become contaminated with oral flora during use with this newly designed disposable prophy angle nosecone system. Also, internal contaminants appear to be released out of the esa ^TM angle. It appears that unless properly sterilized, slow-speed handpiece motors pose a risk for cross-infection.