| ObjectiveTo evaluate the marginal adaptation of cast full crowns fabricated with three different finish lines and cemented with three luting cements. Two-way ANOVA was used to analyse the interaction effect of two factors on marginal adaptation of cast full crowns.Materials and MethodsNinety resin models with a preparation height of6mm, a diameter of10mm and a total convergence angle of12degrees were made and randomly divided into three groups according to their finish lines. Wax patterns for full crowns were fabricated by a traditional method. Four symbol sites were made in every pattern. All the patterns were invested and cast to fabricate crowns. The crowns were seated on the preparations according to their symbol sites. Then the models in each group were randomly subdivided into three groups on average, and crowns were cemented with Zinc polycarboxylate cement (ZPCC), CX glass ionomer cement (GIC) and resin cement (RC). The groups were as follows:A) chamfer+ZPCC; B) chamfer+GIC; C) chamfer+RC; D) shoulder+ZPCC; E) shoulder+GIC; F) shoulder+RC; G) knife edge+ZPCC; H) knife edge+GIC and I) knife edge+RC, respectively. A10kg load was then maintained on the crowns until complete cement cure. Their vertical marginal gaps were photographed at four points around each crown by SMZ745T optical stereomicroscope before and after cemented, respectively, and measured using Image-Pro Plus6.0. The data were analysed by two-way ANOVA using SPSS13.0. Results1. The marginal gaps before cementation were as follows:A)(53.52±33.26) μm, B)(56.46±34.76)μm, C)(57.49±26.53)μm, D)(53.21±35.19) um, E)(55.48±26.62) um,F)(55.39±35.89) um, G)(58.74±27.63) um, H)(56.07±35.91) um and I)(53.86±25.38) um. No significant differences were found among different groups (P>0.05).2. The marginal discrepancies after cementation were as follows:A)(64.84±35.62) μm, B)(47.47±28.27) μm, C)(107.78±56.91)μm, D)(69.68±39.44) um, E)(58.44±38.39) um, F)(131.90±66.18) um, G)(65.88±36.31)um, H)(50.70±27.63) um and I)(114.47±58.73) um.3. The data were analyzed by one-way ANOVA. there were significant differences among the group A, the group B and the group C (P<0.05), among the group D, the group E and the group F (P<0.05), among the group G, the group H and the group I (P<0.05).4. In ZPCC groups, no significances were found among the group A, the group D and the group G (P>0.05). In GIC groups, there were no significant differences among the group B, the group E and the group H (P>0.05). In RC groups, there were no significant differences among the group C, the group F and the group I (P>0.05).5. Under the effects of finish line and luting cement, the minimum discrepancy was in the group B and the maximum in the group F compared with the others. The double factor variance analysis showed the finish lines combined with luting cement types was interactive (P=0.0021).ConclusionUnder the restricted experimental condition of this study, we can conclude that:1. When using the same cement, there are no significant differences among different finish lines groups.2. Despite different finish lines, there is larger discrepancy in RC than in ZPCC or in GIC.3. Considering marginal adaptation, the effect of finish line and luting cement on marginal adaptation is interactive. For cast full crown restoration, the chamfer combined with GIC should be a better choice. |
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