doctoral candidate
Baku, Russian Federation
Subject. Edge clearance and mechanical strength are important factors for selecting all-ceramic zirconia crowns. The article presents the results of evaluating the regional adaptation of single monolithic zirconia crowns mounted on premolars and molars made using the CAD/CAM system. Objectives — a clinical assessment of the edge conformity and absolute marginal discrepancy of single monolithic zirconia crowns made by the CAD/CAM system and fixed on premolars and molars. Materials and methods. 75 patients (mean age 34.9 ± 3.77 years) with monolithic zirconia crowns fixed 6 months ago were examined. 3Shape software, Zenotec CAM Wieland Dental system, CNC Wieland Select milling machine, Zenostar translucent blanks were used. The measurements were performed in vivo. Marginal clearance and absolute marginal mismatch are measured with an optical microscope. All measured data were averaged based on four positions: edge, rounded shoulder, axial wall, and occlusal area. Results. 98 crowns were established: in 74.7 % of cases 1 crown was installed, in 20.0 % of cases — 2 crowns, in 5.3 % of cases — 3 crowns. 48 crowns are installed on premolars, 50 — on 1 and 2 molars. On the upper jaw 22 were fixed on premolars, 20 restorations on molars, 26 and 30 crowns on the lower jaw, respectively. The average value of the edge gap was 90.6 ± 20.71 μm, and the average values of the absolute edge discrepancy were 164.90 ± 22.28 μm. The marginal gap of premolars and molars averaged 90.8 ± 18.96 μm and 89.14 ± 21.0 μm, respectively, and the absolute boundary discrepancy was 165.82 ± 19.95 and 163.11 ± 22.37 μm, respectively. Conclusion. The results of the marginal fit and the absolute marginal divergence of monolithic crowns based on zirconium dioxide are within the limits of clinical acceptability. 2. It is necessary to take measurements before and after the sintering process.
monolithic crowns, zirconium dioxide, CAD/CAM, premolars, molars, marginal fit, absolute marginal divergence
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