Objective To compare the performance and contaminating level of zero suck-back dental handpiece with conventional handpiece through bacteriological experiments for clinical practice.
Methods Ten zero suck-back handpieces and ten conventional handpieces sucked (n=1 and 3)without bits and in the solution, or with bits and on the surface of culture solution of 107 cfu/mL, 108 cfu/mL, and 109 cfu/mL Salmonella typhimurium TA97 respectively to prepare the bacterium suspensions. The flushing fluid of handpieces and tubes at different time periods was collected for bacterial culture to count the number of bacteria and then compare the contaminating levels of different units.
Results Compared with conventional handpiece, zero suck-back handpiece exhibited less resorption. As sucked with Salmonella typhimurium of 1& #215;107 cfu/ml concentration, 250& #177;71 bacterial colonies of tester strain had been detected in the cultured specimen collected from the rear of the zero suck-back handpieces, while 944& #177;156 had been detected in the cultured specimen collected from the rear of the conventional ones. The tester strain had not been detected in zero suck-back handpieces and tubes under simulated clinical uses, but was detected in conventional ones. After flushing 60 s, no strain could be detected in conventional handpieces and tubes. Compared with one resorption, 3 times of resorption by conventional handpieces produced more bacteria. As sucked with Salmonella typhimurium of 1& #215;109 cfu/ml concentration, 762& #177;292 bacterial colonies of tester strain had been detected in the cultured specimen collected from the head of the zero suck-back handpieces after 1 time of resorption, while 1 925& #177;106 had been detected in the cultured specimen collected from the head of the conventional ones after 3 times of resorption.
Conclusion The use of zero suck-back handpieces could avoid resorption of contaminating substances and thus, reduce the possibility of cross infection. Tubes of dental units should be flushed before and after use of conventional handpieces.
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