Objectives: The purpose of this in vivo study was to determine if slow-speed handpiece motors can become contaminated with oral flora during use with prophy angles. Methods: This study was a three-by-two crossover design involving 20 human subjects, two types of handpieces (single and double units) attached to two types of disposable prophy angles and one type of reusable metal prophy angle. Sterile handpieces and each type of prophy angle combination were used to polish subject's teeth for 3 to 5 minutes. Inside surfaces of the angle, nosecone including handpiece gears, and motor were sampled using paper points and swabs, which were placed in PBS (pH 6.8) and vortexed. Aliquots were then spiral plated onto enriched trypticase soy agar (ETSA) plates, which were incubated anaerobically and aerobically (with 5% CO
2) at 37
oC for seven days. After incubation, plates were examined for the presence of bacterial colonies. Levels of contamination were expressed as colony forming units per milliliter (CFU/mL). Results: For each of the six combinations of handpieces and prophy angles, 75 – 100% of the twenty subjects' systems showed bacterial contamination in at least one cultured area. Of the 420 sites samples, 258 (61.4%) produced bacterial growth. Contamination varied from 0 – 5000 CFU/mL (0 - 4500 CFU/mL for anaerobic bacteria: 0 – 5000 CFU/mL for aerobic bacteria). No significant differences (GEE modeling, p>0.05) existed between any of the handpiece prophy angle combinations in mean total bacteria count. Double unit handpieces were not significantly (p>0.05) more likely to be contaminated than were single unit handpieces. Conclusion: These data suggest that internal surfaces of slow-speed handpieces can become microbially contaminated during use with prophy angles. Clinical Implications: It appears that unless properly sterilized, slow-speed handpieces pose a risk for cross-infection.
This study was supported in part by the Delta Dental Master Thesis Award Program.