Microbial leakage and apical inflammatory response in dog's teeth after root canal filling with different sealers, post space preparation and exposure to the oral environment

Abstract

Coronal leakage is an important factor affecting the outcome of endodontic therapy. This study evaluated the microbial leakage (ML) and the apical inflammatory response (AIR) in dog's teeth after root canal filling with three endodontic sealers, post preparation and exposure to the oral environment, testing the hypothesis that there is a positive correlation between these two histological parameters (ML and AIR). Sixty-four root canals of 8 mongrel dogs were cleaned, shaped and randomly distributed into groups according to the sealer to be used: Sealer 26 (n=18); AH Plus (n=18); RoekoSeal (n=19); no sealer - control group (n=9). Root canals were filled by the lateral condensation technique. Post space preparation left 4 mm of filling material in the apical root third, and specimens were exposed to the oral environment for 90 days. The dogs were killed and jaw blocks were histologically processed using Brown & Brenn and HE staining techniques. ML and AIR were scored from 1 to 4. Results were analyzed statistically using ANOVA, Duncan's post-hoc test and Spearman's correlation. ML and AIR score means were: Sealer 26 - 2.44+/-0.98 and 2.50+/-0.70; AH Plus - 2.50+/-0.78 and 2.22+/-0.54; RoekoSeal - 1.84+/-0.95 and 2.63+/-0.83; Control - 2.56+/-1.23 and 3.11+/-0.60. Statistically significant differences in AIR scores were found between the AH Plus and control groups (p<0.05). Although RoekoSeal had the lowest ML means, and AH Plus, the lowest AIR means after 90-day exposure to the oral environment, no statistically significant differences were found between the three sealers under study, and no correlation was found between ML and AIR.

FIGURE 1. A – SEM micrograph of apical and periapical regions of a specimen in the AH Plus group. Observe newly formed hard tissue deposition (arrow), followed by an organized periodontal ligament. HE. 40X. B – Close-up view. Observe sparse mononuclear cells, compatible with score 2 of AIR. HE. 100X

FIGURE 2. A - SEM micrograph of apical and periapical regions of the same specimen showed in Fig.1, belonging to the AH Plus group. No microorganisms can be seen (score 1 of ML). B&B. 40X. B – Close-up view. B&B. 100X

FIGURE 3. A - SEM micrograph of apical and periapical regions of a specimen belonging to the RoekoSeal group. Note inflammatory infiltrate along apical periodontal ligament (arrow). HE. 40X. B - Close-up view. Mononuclear inflammatory reaction can be observed, compatible with score 3 of AIR. H&E. 100X

FIGURE 4. A - SEM micrograph of apical and periapical regions of a specimen in the control group. Note inflammatory infiltrate along apical periodontal ligament. Areas of apical cementum and dentin resorption can be seen (arrow), as well as resorption of adjacent bone. HE. 40X. B - Close-up view. Intense neutrophil infiltrate with some dead cells and resulting in pus formation, compatible with score 4 of AIR. HE. 400X

FIGURE 5. A - SEM micrograph of cervical region of the same specimen shown in Fig. 4, belonging to the control group. Observe the presence of microorganisms within lumen, canal walls and dentinal tubules (arrow). B&B. 40X. B – Close-up view. B&B. 400X

FIGURE 6. A - SEM micrograph of apical and periapical regions of the same specimen of Figs. 4 and 5. This specimen scored 4 in ML. Note presence of microorganisms within apical lacunae (arrows) near root resorption area. B&B. 40X. B – Close-up view. Microorganisms (arrows) within lacunae and ramifications of apical cementum. B&B. 400X