Clinical and Molecular Microbiological Evaluation of Regenerative Endodontic Procedures in Immature Permanent Teeth

This study evaluated the bacterial levels after regenerative endodontic procedures and their correlation with the treatment outcome using molecular microbiology methods.

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% sodium hypochlorite (S2), and after intracanal dressing (S3) using either triple antibiotic paste (n = 7) or calcium hydroxide with chlorhexidine (n = 8). The Wilcoxon test for related samples and the Mann-Whitney test were used for statistical analysis (P < .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 < .05).

All S1 and S2 samples were positive for bacteria, but the number of positive S3 samples decreased to 53.3% (P = .001). Overall, there was a significant reduction of bacterial levels after each treatment step (S1-S2, P = .001; S2-S3, P = .02). In the triple antibiotic paste and chlorhexidine groups, 57.1% and 50% of S3 samples were positive with median numbers of 6.97 × 10³ and 3.59 × 10⁴ bacterial cells, respectively. No significant differences were found between the 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 (R² = 0.0043).

Although the bacterial levels were drastically reduced after the regenerative endodontic procedures, the residual bacteria influenced the thickness of the dentinal walls.