Pulp Revascularization Of Pulpless Immature Teeth

Objective:To evaluate the characteristic of revascularization in pulpless immature permanent tooth without infect by radiography, histology and immunohistochemistry in dogs.Methods:Eighteen immature right anterior teeth from three dogs divided into experimental group. The pulp in experimental group was removed completely and revascularization was performed immediately under uninfection. Contralateral eighteen anterior teeth divided into control group, and left them for natural development. All of the teeth were monitored radiographically preoperation, during operation, after operation immediately and three months later. The animals were sacrificed after three months. The regenerative tissue in root canals were evaluated by histology and immunohistochemistry.Results:X-ray:The experimental group had 33.3% of the root with continued thickening of radicular dentin walls and vertical increasing of root length judged by radiographically.55.6%(10/18) of the root apex became narrow. The hard tissue bridges were observed beneath the mineral trioxide aggregate(MTA) in 66.7%(12/18) of experimental group.HE Staining Micrograph Examination:Regenerative tissue was observed in most of the experiment samples. There was a gain of thickness of the root because of the ingrowth of cementum-like tissue from the root surface into the canal walls. Most samples in experimental group had an histological evidence of apical closure.94.5% canal spaces (17/18) revealed new vital tissue. In 8 of the 18 experimental samples, we can found the inflammatory infiltration in canal and/or at apex. Based on histological examination, we found three types of tissue regenerated in canal space:cementum-like tissue, bone-like tissue and periodontal ligament-like tissue.Immunohistochemistry:There were not revealed the expression of Neuron Specific Enolase (NSE) and S-100 protein in experimental group, while NSE in 33.3%(5/15) samples and S-100 in 53.3%(8/15) samples were positive in control group。Conclusion:1.Revascularization promote the new tissue regeneration in the canal of pulpless immature teeth, and aid to root thickness, apical length and closure.2. There were mainly three types of new tissue in cananl space: cementum-like tissue, bone-like tissue and periodontal ligament-like tissue. 3. No nerves were found in regeneration tissue by immunohistochemistry.