| Objective: Vital pulp therapy is the best choice for pulp exposure caused by dentalcaries, trauma and various operative dentistry. At present, the pulp capping materials used clinically are all not ideal, therefore, it is necessary to explore the better candidates for pulp capping. An ideal pulp capping agent should conceivably have properties to induce odontoblast differentiation and reparative dentinogenesis and preserve pulp vitality. It is suggested that a functional network consisting of extracellular matrix molecules and growth factors control odontoblast differentiation and reparative dentinogenesis. Fibronectin has been demonstrated to play a crucial role in odontoblast differentiation and reparative dentin formation. MTA can induce cytological and functional changes in pulp cells, resulting in formation of fibrodentin and reparative dentin at the surface of mechanically exposed dental pulp. MTA is successful in preventing bacterial microleakage, minimizing pulpal inflammation and regulating alkaline phosphatates. This study is aimed to assess the effect of MTA combined with fibronectin on reparative dentinogenesis and odontoblast differentiation, investigate the possible mechanism underlying traumatized pulp repair, which would facilitate the choosing of ideal pulp capping agents.Methods: (1) Freshly exposed pulps of twenty six cats were capped with fourdifferent agents. MTA, MTA combined with fibronectin, calcium hydroxide, fibronectin/starch as control. The pulpal tissue reactions were assessed by light microscopy after healing interval of 1 and 4 weeks, and observed by scanning electronic microscopy after healing interval of 12 weeks. (2) MTA, MTA combined with fibronectin were used in 68 patients with exposed pulp teeth by caries, pure calcium hydroxide was used in 41 patients with exposed pulp teeth as controls. Each group was divided into two parts according to age. After 4 and 12 weeks's observation, the success rate for pulp capping was assessed.Results: Light microscope (1) 1 week after pulp capping, no reparative dentinformation was observed in each group. (2) 4 weeks after pulp capping, the dental pulps capped with MTA/fibronectin showed no or slight cellular inflammatory responses and odontoblast differentiation with tublar dentin bridge on the exposed sites. In MTA group, the dental pulpsshowed slight to moderate cellular inflammatory responses with osteodentin formation. In calcium hydroxide group, the pulps showed moderate to severe inflammatory responses with calcified matrix. In fibronectin/starch group, no dentin bridge formation was observed, the pulps showed severe cellular inflammatory responses.Scanning electronic microscopy In calcium hydroxide group, specimens showed scatted and calcified matrix. In MTA group, specimens showed irregular dentin bridge structures along the pulp-MTA interface, the crystalline-like structures were loosen with lacunas. In MTA/fibronectin group, continuous and complete dentin bridge structures were found along the pulp-MTA interface, the crystalline-like structures were in direct contact with the dentin wall, the exposed pulp sites were closed by the dentin bridge. In fibronectin/starch group, no crystalline-like structure was observed.Clinical curative effect (1)4 weeks after pulp capping, the success rate among 3 groups had no significant difference (P>0.05). (2) 12 weeks after pulp capping, the success rate of MTA and MTA/fibronectin were significantly higher than that of calcium hydroxide (P<0.05). (2) There was a significant relationship between the success rate and age in MTA group and calcium hydroxide group (PO.05), however, in MTA/fibronectin group, the success rate was not correlated with age (.PXD.05).Conclusions: (1) MTA combined with fibronectin could induce complete dentinal bridge formation, In MTA group, the formed dentinal bridge was irregular. (2) Calcium hydroxide could induce to form irregular dentin bridge, however it took a longer time to form the dentin bridge, the dental pulps showed...
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