| Objective: Overhanging dental restoration(ODR) is defined as an extension of restorative material beyond the confines of a cavity preparation. Among ODRs, the most dangerous to periodontium is that filling material exceeds the gingival wall of dental cavity, and it is one of contributing factors for gingivitis and attachment loss of periodontium. Gingival retraction cord is a cotton line in which contains zincum, aluminium, slight dose of adstringens and antihemorrhagens, and it's clinical employment and manipulation is convenient. The topic of our research is to observe whether gingival retraction cord can prevent overhanging in fillings of subgingival cavities and odonto-defects.Method: The study consists of two parts:Part 1: The experimental study of using gingival retraction cord for preventing overhanging in fillingⅤclass cavities in an animal model.The 36 dentalⅤclass cavities were made in the buccal surfaces of Mongrel dogs' maxillary and mandibular premolar teeth. The teeth were divided into 2 groups randomly. One group was filled with composite resin after using retraction cord to retract gingiva. The other group was filled with composite resin directly. The aspartate aminotransferase levels (AST) of gingival crevicular fluid were measured on 1 month, 3 months and 6 months after operation. The periodontal status in dogs was identified by diagnosis clinical parameters and histological examination.Part 2: The clinical research on using gingival retraction cord for preventing overhanging dental restoration.80 teeth with dental caries or defects in 24 patients were selected. The teeth were divided into 2 groups randomly. In group 1, dental caries were removed and cavities were prepared routinely, and filled with composite resin after using retraction cord to retract gingival. The dental fillings were shaped and polished. The other is control group, caries were removed and filled directly, Gingival crevicular fluid (GCF) quantity and AST levels, plaque index (PLI), sulcus bleeding index (SBI) and periodontal probing depth (PD) were measured on 1 month, 3 months and 6 months after operation.Results: In part 1, 1 month after operation, the differences of GCF and AST levels between the experimental group and the control group were not significant (P＞0.05); but in 3 and 6 months after operation, GCF and AST levels in the group using retraction cord to retract gingiva were lower than those of the control group, the differences were significant (P＜0.01).The histological sections on 6 months after operation shows that: epithelium of gingival sulcus of the experimental group (EG) eumorphism, very small amount of inflammatory cells infiltrated; epithelium of gingival sulcus of the control group (CG) had large amount of inflammatory cells infiltrated, and blood vessel hyperplasia and congestion.In part 2, before operation, differences of GCF and AST levels, PLI, SBI, and periodontal probing depth between EG and CG were not significant (P＞0.05). 1 month after operation, the incidence of ODRs in using retraction cord to retract gingiva were significantly lower than those of the control group (P＜0.01); 1 and 3 months after operation, the differences of GCF and AST levels, the frequencies of PLI≥2 and SBI≥2, and periodontal probing depth between the EG and CG were not significant(P＞0.05); 6 months after operation, no significant differences were found between GCF levels, the frequencies of PLI≥2 and SBI≥2 and periodontal probing depth in the EG and CG (P＞0.05), but the AST levels between the EG and CG were significantly different (P＜0.01).Conclusion:1,It was acceptable to use gingival retraction cord for preventing overhanging in filling buccal-cervical cavities with 0.5mm subgingival and then prevent the damage of periodontal tissue in animal experiments. Overhangs affect the periodontium may happen in 3 months after restored.2,The incidence of ODRs after using retraction cord to retract gingiva were significantly lower than those of not. It was available to use retraction cord for preventing overhanging in filling cavities defects with leveling or≤1mm of gingival margin.3,It was available to use retraction cord for preventing overhanging in filling cervical cavities defects with leveling or≤1mm below gingival margin and then prevent the damage of periodontal tissue in clinical experiments.4,AST levels, the frequencies of PLI≥2 and SBI≥2 after restoring were much higher than those of before. The influences of subgingival restortions were caused by many factors. The purpose of this study was to seek a way to preventing overhangings. Other factors would be investigated in the future.
|
PDF Full Text Request