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Many dental ceramics are commercially available for the fabrication of dental fixed prostheses. The variation in processing and composition of these ceramics could affect the marginal discrepancy of all-ceramic dental prostheses. The objective of this study was to evaluate the marginal and internal adaptation of lithia-disilicate-based all-ceramic posterior crowns fabricated by heat-pressing and computer-aided designed and manufacturing (CAD-CAM) techniques.
Materials and methods: Three lithia-disilicate-based dental ceramics were used in this study (VINTAGE LD Press, IPS e.max Press and IPS e.max CAD). A complete coverage preparation on a posterior upper first molar crown was made on an Ivorine dentoform tooth. Forty type IV gypsum plaster dies were fabricated for use in four experimental groups. For Group 1 and 2, the die plaster models and a wax-up were used to make ten posterior crowns for VINTAGE LD Press and IPS e.max Press as monolithic crowns using a heat-pressing technique. Ten posterior crowns were made for IPS e.max CAD using a CAD-CAM technique for Group 3. For Group 4, ten posterior molar substructures were also made using IPS e.max CAD and veneered with IPS e.max Ceram using a conventional condensation and sintering technique. All ceramic crowns were affixed to their corresponding dies using a silicone material. Micro-computed tomography (Micro-CT) was used to analyze marginal and internal fit of each ceramic crown. The differences between the mean gap widths of all experimental groups were analyzed using the Kruskal-Wallis nonparametric test at a significance level of .05.
Results: The median marginal gap widths of all groups were not significantly different and these values were within an acceptable limit at 120 µm. For internal gap widths, IPS e.max® Press crowns had a significant lower internal gap width than those of the other three remaining groups. IPS e.max® CAD veneered with IPS e.max® Ceram had marginal and internal gap widths comparable to those of IPS e.max® CAD monolithic crowns.
Conclusions: The marginal and internal adaptation of lithia-disilicate-based all-ceramic posterior crowns fabricated by a heat-pressing procedure was as good as those fabricated from the CAD-CAM technique. The micro-CT analysis was a useful analytical technique for internal and interfacial studies of dental prostheses and materials.
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