This study evaluated by molecular microbiology methods the bacterial levels after regenerative endodontic procedures and their correlation with the treatment outcome.
Root canal samples of 15 necrotic immature teeth were analyzed by quantitative polymerase chain reaction. Bacteria were counted before treatment (S1), after irrigation with 6% NaOCl (S2), and after intracanal dressing (S3) using either triple antibiotic paste (TAP) (n = 7) or calcium hydroxide with chlorhexidine (CHP) (n = 8). The Wilcoxon test for related samples and the Mann-Whitney test were used for statistical analysis (p < 0.05). After a follow-up period of 12-48 months, clinical and radiographic findings were correlated with microbiological data using a linear regression model (p < 0.05).
All S1 and S2 samples were positive for bacteria, but the number of positive S3 samples decreased to 53.3% (p = 0.001). Overall, there was a significant reduction of bacterial levels after each treatment step (S1-S2, p = 0.001; S2-S3, p = 0.02). In TAP and CHP groups, 57.1% and 50% of S3 samples were positive, with median numbers of 6.97 x 10 and 3.59 x 10 bacterial cells, respectively. No significant differences were found between groups. Periapical healing occurred in all cases despite the presence of low levels of residual bacteria. However, the latter had a negative impact on the thickness of dentinal walls (R = 0.0043).
Although the bacterial levels were drastically reduced after the regenerative endodontic procedures, residual bacteria influenced on the thickness of dentinal walls.

Copyright © 2020. Published by Elsevier Inc.