Abstract: PURPOSE: This study was aimed to compare the difference between iRoot SP and AH Plus on root canal sealing ability for teeth extracted due to severe periodontitis and explore whether the dentin tubule pathway plays an important role in the development of endodontic-periodontic lesions(EPL), in order to provide a theoretical basis for selection of proper time for root canal therapy and suitable root canal sealants in patients with EPL. METHODS: Fifty single-root anterior teeth extracted due to severe periodontitis were selected. The roots were completely debrided to remove the calculus, dental plaque and cementum. They were divided into two groups, namely group A and group B, with 25 teeth in each group which included 21 experimental teeth and 4 negative control teeth. The root canals were filled with iRoot SP (group A) and AH Plus(group B) plus gutta-percha by cold lateral condensation technique. All roots were cut across the middle section and divided into coronal segment (group A1 and B1) of which the coronal section and apical section were sealed with self-etching adhesive and fluid resin, and then covered with melted casting wax twice. The apical segment of the experimental group was further divided into two subgroups, namely, the unsealed apical foramen group(group A2 and group B2) and sealed apical foramen group (group A3 and group B3). In group A2 and group B2, only the coronal section was sealed as mentioned above. While in group A3 and B3, both the coronal sections and apical foramen were sealed. The whole surface of the specimens in negative control group were all covered with melted casting wax twice. The samples were immersed in 1% methylene blue dye solution for 14 d, then they were longitudinally cut in half. Vernier caliper was used to measure the penetration length of the dye solution along the inner wall of each root canal. The sample sections were all photographed to process for Image Pro Plus software analysis of the penetration area of the dye solution in dentin tubule. The intra-group and inter-group differences were analyzed by one-way analysis of variance and LSD method, respectively. The data were analyzed by SPSS 26.0 software package. RESULTS: The penetration length of group A2 was significantly longer than that of group A3 (P<0.05). The penetration length of group B2 was significantly longer than that of group B1 and B3 (P<0.05). There was no significant difference between the corresponding subgroups of group A and group B (P>0.05). Statistical analysis showed that the percentage of stained dentin tubule area in group A1 was significantly lower than that in group A2(P<0.05), and the area percentage in group B1 was significantly lower than that in group B2 and B3(P<0.05). There was no significant difference between the corresponding subgroups of group A and group B(P>0.05). CONCLUSIONS: For periodontally compromised teeth, neither iRoot SP nor AH Plus paste combined with gutta-percha by cold lateral condensation technique could completely seal the root canal. There is no significant difference between iRoot SP and AH Plus paste on root canal sealing ability in teeth from periodontitis patients. Dentin tubules are not the main pathway of periodontal tissue and pulp communication. The pathway in the apical 1/2 segment of the root plays a more important role in the occurence of EPL, which suggest that root canal therapy may be taken into consideration when the clinical attachment loss reaches more than the apical 1/2 of the root.

Key words: Periodontitis, Endodontic-periodontic lesions, Root filling paste, Root canal microleakage, Dentin tubule