[Degradation evaluation and success of pulpectomy with a modified primary root canal filling in primary molars].

OBJECTIVE: To compare clinical and radiographic success rates of a modified primary root canal filling (ingredients: zinc oxide-eugenol, iodoform and calcium hydroxide, MPRCF) vs. zinc oxide-eugenol cement (ZOE) and calcium hydroxide/iodoform paste (Vitapex) in pulpectomized primary molars at the end of 6 and 12 months, and to evaluate the degradation of materials in the root canals and in apical area. METHODS: In the study, 160 primary molars from 155 children (the average age: 5.88±1.27 years) that met the inclusion criteria were allocated to one of the three materials via block randomization. A two-visit pulpectomy was performed by an investigator. The clinical and radiographic diagnoses were blindly assessed by other two investigators. RESULTS: At the end of 6 and 12 months, the ZOE and MPRCF success rates were 100% both in clinical and radiographic evaluation. The Vitapex group showed the clinical success of 100% at the end of 6 months and 94.5% at the end of 12 months. Radiographic evaluation for the Vitapex group showed 80.4% success at the end of 6 months and 60.7% at the end of 12 months. No statistically significant differences were noted at the end of 6 months in the three groups both in clinical and radiographic evaluation. The success rates in clinical and radiographic evaluation at the end of 12 months for ZOE and MPRCF groups were not significantly different, and better than those for Vitapex group with statistically significant difference. The completely resorb rate of excess extruded extraradicularly were 14.3%, 100% and 71.4% for ZOE, Vitapex and MPRCF at the end of 12 months. The rates of resorption of material at the same rate of the root were 5.8%, 7.2% and 40.9% for ZOE, Vitapex and MPRCF at the end of 12 months. CONCLUSION: MPRCF, a mixture of zinc oxide eugenol and iodoform with calcium hydroxide can be used as a root canal filling material in primary teeth, taking account of the success rate and resorbing at a similar rate with the roots of the primary teeth.

Root resorption of primary molars without successor teeth. An experimental study in the beagle dog.

Tooth agenesis is a common craniofacial congenital malformation in humans, but little is known about the mechanisms of root resorption in this condition. The purpose of this study was to investigate the mechanisms of root resorption in primary molars without successors. An animal model without permanent tooth germs was established by surgery in beagles. The times of onset of primary molar root resorption, with and without successors, were compared. The distribution of immune cells, odontoclasts, and their activating factors were determined by histochemistry and immunohistochemistry. Root resorption of primary mandibular molars without successors began later than physiological resorption. In primary molars without permanent germs, odontoclasts and immune cells were present mainly in the apical pulp at the start of root resorption, whereas in control teeth receptor activator of nuclear factor-κB ligand (RANKL)-positive cells were found mainly in the region of the periodontal ligament. CD14(+) and CD3(+) cells were found in both the pulp and the periodontal ligament region. These results suggest that the dental pulp of primary molars, as well as immune cells, may play an important role in root resorption in primary molars without permanent tooth germs.

Identification of multipotent stem cells from adult dog periodontal ligament.

Periodontal diseases, which are characterized by destruction of the connective tissues responsible for restraining the teeth within the jaw, are the main cause of tooth loss. Periodontal regeneration mediated by human periodontal ligament stem cells (hPDLSCs) may offer an alternative strategy for the treatment of periodontal disease. Dogs are a widely used large-animal model for the study of periodontal-disease progression, tissue regeneration, and dental implants, but little attention has been paid to the identification of the cells involved in this species. This study aimed to characterize stem cells isolated from canine periodontal ligament (cPDLSCs). The cPDLSCs, like hPDLSCs, showed clonogenic capability and expressed the mesenchymal stem cell markers STRO-1, CD146, and CD105, but not CD34. After induction of osteogenesis, cPDLSCs showed calcium accumulation in vitro. Moreover, cPDLSCs also showed both adipogenic and chondrogenic potential. Compared with cell-free controls, more cementum/periodontal ligament-like structures were observed in CB-17/SCID mice into which cPDLSCs had been transplanted. These results suggest that cPDLSCs are clonogenic, highly proliferative, and have multidifferentiation potential, and that they could be used as a new cellular therapeutic approach to facilitate successful and more predictable regeneration of periodontal tissue using a canine model of periodontal disease.

[The role of pulp in the root resorption of primary teeth without permanent tooth germs].

OBJECTIVE: To investigate the role of pulp in the root resorption of primary teeth without permanent tooth germs. METHODS: The animal model without permanent tooth germs was established by surgery in Beagle dog. The root resorption was observed by taking periapical radiographs periodically. The samples of mandibular bone and pulp at different resorption stages were collected. The distribution of odontoclasts and the activating factor was analyzed by histological staining and semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR). The role of pulp in the root resorption of primary teeth was tested by early pulpectomy. RESULTS: In the root resorption of primary molars without permanent teeth germs, a large number of odontoclasts were present on the pulpal surface of the root canal. Semi-quantification RT-PCR showed that the ratios of the expression of receptor activator of NF-κB ligand (RANKL) mRNA and ß-actin in the pulp of permanent teeth and primary teeth without permanent teeth germ during different periods of root resorption are 0.1314, 0.1901, 0.2111 and 0.6058 (P > 0.05). The root resorption of primary teeth without permanent teeth germs in test groups was about 5 weeks later than that of control group. CONCLUSIONS: The pulp of primary tooth played an important role in the root resorption of primary tooth without permanent tooth germ.