Abstract
Objective:The aim of the study was to assess the failure loads and compressive stresses among bilayered press on Y-TZP (POZ) and press on metal (POM) crowns with different core-veneer thickness.Methods:Thirty metal and Y-TZP copings were fabricated using CAD-CAM technology with specified thickness. All copings were veneered with ceramic materials using hot pressing technique, with 2mm and 2.5mm thickness. The different coping veneer thickness of crowns resulted in six study groups, including, POM: Coping/ veneer thickness of 0.7/2mm (Gp1), 0.7/2.5mm (Gp 2) and 1mm/2mm (Gp 3)-POZ: 0.7/2mm (Gp A), 0.7/2.5mm (Gp B) and 1mm/2mm (Gp C). Crowns were cemented to a standard implant analog and failure loads (FL) and compressive stress (CS) was ascertained by controlled load application in a universal testing machine. Data was analysed using ANOVA and multiple comparisons test.Results:The maximum FL were observed in the POM specimens with a C/V ratio of 1/2 (Group 3-1880.67± 256.78 N), however the lowest FL were exhibited by POZ crowns with 1/2 C/V ratio (Group C-611.89± 72.79 N). Mean FL and CS were significantly higher in POM compared to POZ crowns in respective groups. Increasing the coping-veneer thickness increased FL and CS among POM crowns. Increasing veneer and decreasing coping thickness improved FL and CS among POZ crowns.Conclusions:Press on metal specimen showed higher resistance to fracture than Press on Y-TZP specimens. Improved failure loads were observed in thin coping and thick veneers among Press on Y-TZP crowns.
Highlights
All ceramic restorations are commonly used in esthetic dentistry
The maximum failure loads were observed in the press on metal (POM) specimens with a C/V ratio of 1/2 (Group 3-1880.67± 256.78 N), the lowest failure loads were exhibited by press on Yttrium stabilized tetragonal zirconia polycrystal (Y-TZP) (POZ) (Press on zirconia) crowns with 1/2 C/V ratio (Group C-611.89± 72.79 N) (Table-I)
Increasing the veneer thickness from 2mm (Group 1) to 2.5mm (Group 2) increased the failure loads significantly (p
Summary
All ceramic restorations are commonly used in esthetic dentistry. They offer excellent translucency and biocompatibility for long-term oral rehabilitations. Yttrium stabilized tetragonal zirconia polycrystal (Y-TZP) materials based crowns and fixed partial dentures, combine the mechanical strength of the coping and the esthetic appearance of translucent ceramic veneer. The fracture and chipping of veneering ceramic, compromises the prognosis of Y-TZP prosthesis as reported in previous studies.[1,2] The failures occurring in the veneer or at the coreveneer interface is attributed to the presence of tensile stresses trapped within the veneer.[3,4] The stresses are higher in the Y-TZP specimnes compared to metal ceramic prosthesis, resulting
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