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According to the centers for disease control and prevention, practitioners should clean and heat-sterilize handpieces and other intraoral instruments that can be removed from the air and waterlines of dental units between patients. Studies of highspeed handpieces using dye expulsion have confirmed the potential for retraction of oral fluids into internal compartments of the device. Studies usinglaboratory models also indicate the possibility for retention of viral DNA and viable viruses inside both high-speed handpieces and prophylaxis angles. The potencial for contamination of the internal surface of other devices (for example, low-speed handpieces) has not been studied clinically.
The standard of care is to heat-sterilize high-speed dental handpieces after each use, as studies havedemonstrated the potential for internal contamination during use that could lead to cross-contamination. the justification for heat-sterilizing low-speed handpieces systems is less clear. compressed air is needed to operate air-driven low-speed handpieces, and it must be reduced or allowed to scape to prevent excessive heat buildup. All disposable and reusable prophylaxis angles have a vent thathelps reduce or eliminate excessive heat buildup, and it helps prevent the handpiece from being a sealed system, which may contribute to internal contamination of the handpiece. If bacterial contaminants escape through the vent but remain within the handpiece, this could lead to subsequent cross-contamination unless the low-speed handpiece is sterilized between each use. There is, however, onlypreliminary information concerning the internal contamination of low-speed handpiece systems during use.
A recent in vitro study demonstrated microbial movement into and out of two types of low-speed handpieces attached to eight different types of disposable or reusable prophylaxis angles. Angles were operated in solution of Geobacillus stearothermophilus, and the inner surfaces were sampled.The authors tested outward movement by inoculating spores onto the gears of sterilized handpiece motors. They then collected specimens of PBS from the beakers, as well as specimens from the inside of the angle and nose cone, the gears of the nose cone and motor, to evaluate contamination. Results indicated that the spores traveled into the motor 20 percent of the time. When the motor gears werecontaminated, the test bacterium traveled beyond the prophylaxis cup, out of the prophylaxis angle and into the PBS solution in 75 of 160 cases (47 percent).
These results suggest a need for an in vivo study examining the same hypothesis. We conducted a study to investigate whether low-speed handpieces with prophylaxis angles can become contaminated with oral flora during clinical use. Ourhypothesis was that was that microbes could enter the prophylaxis angle/handpiece system at the prophylaxis angle's tip and travel to the gears of the air-driven handpiece motor
TEMAS, METODOS Y MATERIALES.
The Indiana University-Purdue University of Indianapolis Institutional Review Board (approval number 0605-74) reviewed and approved our study protocol. We recruited 20 healthy adult subjects(average age 39.8 years; range, 22-59 years). Our inclusion criteria were that subjects have a minimum of 20 teeth, have good dental health, have a history of a prophylaxis within the last two years and not have a history of untreated periodontal disease. Our exclusion criteria included the subjects' having any significant medical condition or systemic disease requiring them to undergo subacutebacterial endocarditis prophylaxis or being unable to participate in six visits. Subjects provided written informed consent before participation.
Study design. The subjects participated in a randomized, three-by-two crossover study. They underwent a full-mouth tooth polishing performed by a single investigator (S.H) once a week for six weeks. Each subject received a full-mouth polishing with two test...