Comparative Evaluation of Marginal Fit of Three Provisional Restorative Materials in Different Mediums: An In-Vitro Study

Abstract

Temporaries are used as placeholders before the permanent crowns are installed. If the temporary crown is not fitted properly the tooth can be subject to increased decay and gums can become inflamed causing gingivitis which leads to other more serious problems. A provisional fixed restoration will provide a template for defining tooth contour, esthetics, proximal contacts, ridge contacts and occlusion. Margins made by the indirect technique are considered to be more accurate than those made by the direct technique. The purpose of this in vitro study was to compare the marginal accuracy of provisional crowns made from three different biomaterials using the established indirect method in different environments and to evaluate the effect of water absorption on polymerization shrinkage and the effect of polymerization shrinkage occurring in dry storage for a week. Method:Variables used in this study are: a) Revotek LC-light cured composite b) Protemp II c) poly methyl methacrylate. An aluminium master die was machined with dimensions: 5mm length, 10mm gingival diameter, 5 degree taper, and 1mm shoulder then dental stone die was prepared by making an impression of this experimental model using a poly vinyl siloxane material. Both group A and group B consisted of seven specimens each of DPI, ProtempII, Revotek LC. The specimens were evaluated using measuring microscope (Biolux), which had an eyepiece graticule of 1/10th of an mm. The seven specimens in group A (DPI, ProtempII, Revotek LC) were kept in air at room temperature for one week on the dental stone cast and the readings were tabulated and the mean values were obtained. The seven specimens in group B (DPI, ProtempII, and Revotek LC) were kept in water at room temperature for one week and the readings were tabulated in the same manner and the mean values were obtained. Results: Comparative statistics of the mean values of the specimens kept in air at room temperature showed that DPI had the least marginal discrepancies followed by ProtempII, Revotek LC. The values were highly significant (.002) Comparative statistics of the mean values of the specimens kept in water at room temperature showed that DPI had the least marginal discrepancies followed by Revotek LC, ProtempII. The values were highly significant (.009). Conclusion: After one week in air at room temperature and after one week in water at room temperature DPI recorded the minimal marginal discrepancy. When stored in air at room temperature, DPI had the best marginal adaptation. All of the materials showed evidence of continued polymerization shrinkage after storage in air for a week. Water absorption compensated for polymerization shrinkage in DPI and ProtempII whereas Revotek LC was an exception. Keywords: light cured composite, Protemp II-Bis –acryl composite, poly methyl methacrylate, marginal adaptation, provisional restoration.