Influence Of Crown Margin On Periodontal Conditions

Objectives (1)To evaluate the influence of different materials of PFM crown margin on periodontal conditions in beagle dogs. (2) To investigate the influence of crowns margin on periodontal conditions of human.Methods (1) Four beagle dogs were utilized in this study. Three weeks after commencing oral hygiene procedures through supragingival scaling and subgingival scaling, forty-nine dog teeth were prepared for receiving porcelain fused metal(PFM) crowns. One week later, the PFM crowns were cemented, whose buccal margins were made of porcelain fused to metal (PFM)and lingual margins were metal. Clinical parameters were recorded on four sites (mesiolongual, mesiobuccal, distobuccal, distoiongual) of all test teeth immediately before tooth preparation and after 4 weeks of cementation of PFM crowns. During the studying period, professional oral hygiene was performed for the Beagles dogs one time a week. (2) Twenty patients requiring 30 artificial crowns were selected for this study, who corresponded with entry provisions. GCF volume , AST in GCF, PD and the frequency of SBI≥2 and PLI≥1 in 20 patients has been examined immediately before the preparation, 1 week after cementation of temporary crowns and 8 weeks after cementation of dural crowns(PFM group, metal group, subgingival group, supragingival group). The marginal opening of crowrrs were measured before and after the cementation. The oral health education was given after the cementation of temporary crowns and durable crowns.Results (1) The results of animal research were that the volumn of GCF, the frequency of PLI≥1 and SBI≥2, PD and the activity of AST in GCF increased significantly for the group of lingual gingiva (P<0.01) in the time of four weeksafter cementation of crowns. For the buccal gingiva margin, the activity of GCF-AST and the frequency of SBI^2 increased significantly (P<0. 05) , but PD, GCF and the frequency of PLI^l didn' t change significantly. The difference of GCF, the activity of GCF-AST and the frequency of SBI^2 between two groups are significant after A weeks of c.enient.at. ion of crowns (P<0. 05) . (2) The results of clinical research were that GCF volume ,GCF-AST and the frequency of SB1 ^2 did not differ significantly among the groups of before the teeth preparation , 1 week after cementation of temporary crowns and 7 weeks after cemention of crowns(PFM group, metal group, subgingival group, supragingival group) (P>0. 01) , although the frequency of PLI^l decreased significantly (P<0. 01). The marginal opening increased significantly after cementation(P<0. 01), which was negatively correlated to the opening of margin before cementation.Conclusion (1) When professional oral hygiene was performed one time a week, both PFM and metal margins could contribute to periodontal inflammation. The metal contributes to inflammation more greatly than PFM. The reason may be that the degree of plaque adherence to metal is greater than PFM. (2) For 1 week after cementation of temporary crowns and 7 weeks after cementation of durable crowns , there were not unfavourable influence of the best crowns on the periodontal conditions when oral health education was executed. (3) The marginal opening increased significantly after cementation, which was negatively correlated to the opening of margin before cementation within limits .