Accuracy of CEREC virtual articulator and milled veneers
Date
2015
DOI
Authors
Alofi, Raneem Suleiman
Version
OA Version
Citation
Abstract
Objectives: The main failure type in bilayer all-ceramic restorations is veneer chipping. The aim of this study was to evaluate the accuracy and failure load (static and fatigue) of milled porcelain veneers cemented on zirconia framework using only the digital file in CEREC 4.2.5 SW.
Materials and methods: Fifteen (N=15) three unit posterior fixed dental prostheses (FDPs) were fabricated on a standard preparation on ivorine teeth extending from 29-31 using CEREC 4.2.5 SW and direct digital impression. The prepared teeth were scanned using a CEREC blue cam. FPDs were divided into 3 groups (n=5/group) 1: full contour zirconia (Zr), 2: zirconia core veneered with milled Vita Triluxe Forte block using a split file technique (RLT) and 3: provisional material (Vita CAD Temp). Unprepared ivorine teeth were used as control. Occlusal contacts for all groups were measured and compared to those on control using a faroarm machine. To evaluate the cement space, fit checker was plac_ed into the space between the milled veneers and zirconia framework. The weight of fit checker was used to evaluate the space by weight. In addition, the fit checker was sectioned in buccolingual and mesiodistal direction and evaluated under optical microscope for direct measurements. Static and fatigue failure loads of RLT group were measured using instron before and after 100,000 fatigue load cycles. Fractographic analysis using a scanning electron microscope was used to identify the behavior of the tested materials and their mode of failure.
Results: The mean occlusal displacements showed significant differences in CAD Temp and full zirconia groups at all teeth positions, #29, 30 and 31. In RLT group there were no significant differences between #29 and 31; the displacement at #30 was significantly less than #29 and 31. When comparing the effect of material type on the mean occlusal displacement, #29 showed no significant differences in full zirconia and CAD Temp groups but was significantly higher in RLT group. The same was observed at tooth #31; while #30 showed no significant difference in all groups.
The mean cement thickness in mesiodistal section (0.23 mm) was statistically larger than that in buccal (0.149 mm) and lingual section (0.160 mm). Although the cement was thicker in mesiodistal section the variation in the thickness was less than in buccal and lingual section. The cement weight was significantly less after fitting adjustments (p=0.02).
No significant difference was found between RLT mean static failure load before (798.71 N ± 76.95) and after (769.04 N ± 78.94) cyclic fatigue (p = 0.56). Fractographic analysis of static load specimens showed adhesive failure and delamination of the veneering material with no fracture in the zirconia core. After cyclic fatigue, cracks extended into zirconia core at the connector between the premolar and molar.
Conclusions: There were no statistical differences between full zirconia and CAD Temp restorations occlusal positions, while the difference was larger in RLT restorations. The pontic in three units FDPs design had the least difference in occlusal position compared to the abutments. The cement space thickness was larger on the occlusal surface with less variation than on the buccal and lingual. After cyclic loading of RLT, although failure load was not affected, the fracture pattern was different.
Description
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Dissertation (DScD)--Boston University, Henry M. Goldman School of Dental Medicine, 2015 (Department of Restorative Sciences and Biomaterials)
Includes bibliography: leaves 77-84.
Dissertation (DScD)--Boston University, Henry M. Goldman School of Dental Medicine, 2015 (Department of Restorative Sciences and Biomaterials)
Includes bibliography: leaves 77-84.
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This work is protected by copyright. Downloading is restricted to the BU community. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.