Revascularization Of Pulpless Immature Dog Teeth With Periapical Periodontitis

Objective:This study aimed to compare the therapeutic effect of revascularization and the growth characterization of newly regenerated tissues that had grown into canal space between in infected root canal and in uninfected root canal.Methods:Self-control was taken. Thirty-six immature roots from maxillary permanent incisors and mandibular premolars of three dogs were divided into experimental group of right hemimandibular teeth and control group of left hemimandibular teeth. Revascularization was conducted with triple antibiotic paste disinfecting after animal model of periapical periodontitis built-up in experimental group, while revascularization was conducted immediately after the vital pulp in control group was removed completely. Both groups were monitored radiographically at pre-operation, intra-operation, immediate post-operation, post-operative three months and six months to evaluate the establishment of animal model, the healing process of apical inflammation and the continuing root development. The subjects were sacrificed at six post-operative months. The histological characterization of regenerated tissue in root canal was evaluated by hematoxylin-eosin (HE) staining.Results:Partial root canals of experimental group showed reducing periapical radiolucency at three post-operative months. Seven in fourteen effective sample roots from experimental group showed improvement or healing of inflammation according to periapical films. All the occurrence rates of canal wall thickening, apical lengthening and continuing apical closure in experimental group at six post-operative months were 42.86%(6/14), while they in control group were 52.94%,35.29% and 70.59%, respectively. There were no statistically significant differences in the above three parameters between both groups. Histological examination showed that, inner dentin walls were thickened after revascularization in both groups by the deposition of newly generated cementum-like tissue. The formation of cementum-like tissue in dental apex might contribute to root lengthening of partial sample teeth. Both bone-like tissue and periodontal-ligament-like connective tissue were observed in the canal spaces.Conclusion:There was no significant difference in the therapeutic effect of revascularization between in infected root canal and in uninfected root canal. The ectopic regeneration of the cementum-like tissue, bone-like tissue and periodontal-ligament-like tissue indicated that the revascularization-treated root canal systems could provide a suitable microenvironment for the differentiation of multipotent stem cells.