Aim: This in vitro study evaluated coronal leakage of endodontically treated teeth submitted to post space preparation and cementation procedures without rubber dam. Materials and methods: Of the 30 instrumented maxillary anterior teeth, 20 were filled (experimental group) and prepared for post placement. Using a bacterial leakage model, the experimental group's coronal tooth portions were exposed to a culture of Enterococcus faecalis for 30 mins, and glass fibre posts were subsequently cemented to seal the teeth. The apical portion remained in contact with the uncontaminated culture medium for 30 days, which turned cloudy when infiltration occurred. Ten teeth comprised the positive and negative control groups. The data were tabulated and statistically analysed according to the Kruskal-Wallis test (P 0.01), followed by application of the Wilcoxon test. Results: Contamination was observed in two samples after 9 days, corresponding to 10% of the experimental group, with no significant difference between the experimental group (EG) and the negative control group (NCG). Conclusion: The possibility of bacterial leakage exists when post space preparation procedures are conducted in unsterile conditions resulting from failure to maintain the aseptic chain. Palabras clave: dental leakage, post and core technique, rubber dams