Contamination of gutta-percha cones before and during clinical use

Introduction: Decontamination of gutta-percha (GP) cones is recommended before placement in the root canal system. However, the incidence of contamination is still a matter of debate. The present study aimed to evaluate the contamination of GP cones before and during clinical use by general dentists. Materials and Methods: In this in vitro study, 120 GP cones (#20) were examined for incidence of contamination. First, 30 GP packages were opened under aseptic laboratory conditions, and two cones were randomly selected for the laboratory tests. Next, the initially sampled packages were distributed among 30 general dentists and then they were asked to use them clinically for 7 days and then the packages were collected for the microbial tests. The collected cones were placed in tubes containing thioglycolate medium and incubated at 37℃ for 21 days. Bacterial growth was detected by presence of turbidity and comparison with the control groups. A sample was collected from the tubes showing turbidity and plated in blood agar and also underwent Gram-staining, followed by colony counting. Data were analyzed using the Chi-square and paired sample t-test (alpha=0.05). Results: None of the 60 samples from initial sampling of packages showed contamination. However, in secondary sampling after clinical use, 8.3% of GP samples were positive for contamination. There was a statistically significant difference in contamination of packages before and after clinical use (P= 0.02). Conclusion: Within the limitations of this study, it can be concluded that GP cones can become infected after opening the package and in the process of clinical use.