Assessment of residual contamination on dental instruments after infection control practices

This study aimed to compare and assess residual microorganisms and organic materials on selected dental instruments after practicing two infection control methods, including the standard protocol. Scaler tips (ST) , 3-way syringe tips（3ST) , Bristle brushes（BB) , and Rubber cups（RC) were collected and grouped into Standard (Group S) and Non-standard (Group N) for processing. In ST and 3ST, Group S was cleaned and autoclaved, while Group N was disinfected. For BBs and RCs, Group N was cleaned and autoclaved, and new instruments were used as Group S. To confirm the presence of residual microorganisms, instruments from each group were incubated in liquid and solid medium. The generated colonies on solid medium were identified at the species level by polymerase chain reaction (PCR) . To confirm the presence of residual organisms, each instrument was stained with Phloxine B and observed using a stereomicroscope. Only ST（8.0%) and 3ST (28.0%) samples from Group N were detected with residual microorganisms. The identified colonies included Staphylococcus, Cupriavidus, and Streptococcus spp. Residual organics were observed in all samples from Group S and N. These findings highlight the limitations of cleaning followed by autoclaving and especially disinfection in completely eradicating all microorganisms and organics.