Effect of root canal dressings on the regeneration of inflamed periapical tissue.

The aim of this study was to evaluate the effects of chlorhexidine and calcium hydroxide on apical periodontitis in rats. Experimentally induced apical periodontitis was established on the mesial roots of maxillary molars of Wistar rats by leaving the root canals exposed to the oral cavity for 14 d. In the positive control group (n=10 teeth), the root canals were not further treated, but the coronal access openings were filled with composite. In the negative control group (n=10 teeth), partial pulpotomies were performed aseptically and the coronal access openings were sealed immediately. In a third control group (n=10 teeth) the canals were instrumented, left empty, and the coronal access openings were sealed. In the experimental groups, the root canals were instrumented and filled with either 2% chlorhexidine gel or calcium hydroxide paste (n=10 teeth per group). After 7 d all rats were killed and the histological sections were stained for microscopic analysis of periapical regeneration. The data of the subjective evaluation were analyzed with the Kruskal-Wallis test. Lesion sizes were measured and statistically analyzed using the ANOVA and post-hoc Scheffé test. The two treatment groups showed significantly lower average inflammatory scores and smaller lesion sizes than the positive and third control group (p<0.05). No statistically significant differences were obtained between the two treatment groups (p>0.05). Chlorhexidine used as an intra-canal medicament showed good periapical regeneration, suggesting that this may be an alternative to calcium hydroxide root canal dressing.