Study Of Three Biological Properties On The Crown & Bridge Abutments

Objective (1) To study whether the maximal occlusal force of abutments before and after restored with fixed partial denture is to change or not, and to probe into the rules of this change. (2) To investigate the results of Green Or for relieving the dentin sensitivity of the vital pulp teeth after crown preparation. (3) To evaluate the influence of crown margin on periodontal conditions.Methods (1) 33 patients with first molar defected were restored by FPD with the second bicuspid and the second molar as the abutments. Thereafter, the patients were followed up for 6 months. The maximal occlusal force in ICP were recorded by Tekscan occlusal diagnostic system, before its restoration, and instantly after its restoration, 2 months, 4 months and 6 months after its restoration, respectively. The data were analyzed. (2) 201 vital pulp teeth in 134 patients after crown preparation were divided into two groups randomly . In testing group: the dentin surface was treated by Green Or , and in control group: the dentin surface was not treated by anything. The temporary crowns were cemented with ZnO cement for the both groups. The patients were recalled for a VAS value test of sensitivity of the prepared teeth 1 day and 14 days after the preparation and 14 days after the cementation. Meanwhile, the surface and longitudinal section of dentin, which treated by Green Or, were observed under SEM and compared with the normal dentin. (3) Forty-nine dog teeth in Four beagle dogs were restored with porcelain fused metal (PFM) crowns which buccal margins were made of porcelain fused to metal (PFM) and 1 ingual margins were metal. Plaque index (PLI) , probing depth (PD), sulcus bleeding index (SBI), gingival crevicular fluid(GCF) and aspartate aminotransferase(AST) were recorded on four sites (mesiolongual, mesiobuccal, distobuccal, distolongual) of all test dog teeth immediatelybefore tooth preparation and after 4 weeks of cementation of PFM crowns. Meanwhile, in clinic, 30 crown or bridge abutments in twenty patients were selected for this study. GCF volume ,AST in GCF, PD and the frequency of SBI^2 and PLI^l in 20 patients has been examined immediately before the dental preparation,1 week after cementation of temporary crowns and 7 weeks after cementation of crowns(PFM group, metal group, subgingival group, supragingival group). The marginal opening of crowns were measured before and after the cementation.Results (1)Comparing the data taken instantly after its restoration with that before its restoration, 2 months, 4 months and 6 months after its restoration, There were statistical differences. But, there were no statistical differences on the time of 2 months, 4 months and 6 months after its restoration. (2)All of the VAS values of the testing group were lower than that of the control group. The SEM investigations showed that, in the dentinal surface, the dentinal tubules of the dentinal surface treated with Green Or were obstructed by crystalline. But, in the longitudinal section, there was nothing found in the dentinal tubules. (3) The results of animal research were that the volumn of GCF, the frequency of PLI^l andSBI^2, PD and the activity of AST in GCF increased significantly for the group of lingual gingival margin in the time of four weeks after cementation of crowns. For the buccal gingival margin, the activity of GCF-AST and the frequency of SBI^2 increased significantly. The difference of GCF, the activity of GCF-AST and the frequency of SBI ^2 between two groups are significant after 4 weeks of cementation of crowns. Meanwhile, The results of clinical research were that GCF volume , GCF-AST and the frequency of SBI^2 did not differ significantly among the groups of before the teeth preparation , 1 week after cementation of temporary crowns and 7 weeks after cementation of crowns(PFM group, metal group, subgingival group, supragingival group), although the frequency of PLI ^ 1 decreased significantly. The marginal openingincreased significantly after cementation, which was negatively correlated to the opening of margin before cementation.Conclusion (l) The occlusal force of abutments in fixed partial denture will increase after its restoration, and it is perceptible within 2 months while it' s imperceptible after that. (2) Green Or has a good effect on reliving the dentin sensitivity of the vital pulp teeth by sealing dentinal tubules. (3) There was not unfavourable influence of the best crowns on the periodontal conditions while the better oral hygiene habit was executed. Otherwise, there was unfavourable influence on the periodontal conditions and the metal margin contributes to inflammation more greatly than the PFM margin. Meanwhile, the marginal opening increased significantly after cementation.