Title: 0878 - Comparative Evaluation of Shaded and Un-Shaded CAD/CAM Monolithic Zirconia


Maher Mohamed (Presenter)
Faculty of Dentistry, Alexandria University

Sanaa Abdel Kader, Faculty of Dentistry, Alexandria University
Yehia Aboushady, Faculty of Dentistry, Alexandria University
Mona Abdel Latif, New Materials Research Institute (ATNMRI), City of Scientific Research and Technological Applications


Objectives: This work studies the effect of shading using powder mixing method on crystallographic structure and biaxial flexural strength of translucent monolithic dental zirconia.

Methods: Twenty fully sintered monolithic zirconia disks were fabricated in un-shaded [n=10] and shaded [n=10] forms of diameter 12 mm and thickness 1 mm. Specimens were subjected to 1200 thermal cycles corresponding to one year of clinical service, then analysed by X-ray Diffraction (XRD) before being mechanically tested. Specimens were polishedon one side then biaxial flexural strength (BFS) of both groups was measured using a ball-on-ring test fixture on universal testing machine at room temperature. Statistical significance was measured using One-Way ANOVA test. Finally, fractured specimens were examined under confocal laser scanning microscope(CLSM) at magnification 20X

Results: XRD spectrum of un-shaded and shaded disks only showed characteristic peaks of tetragonal zirconia phase. No peaks corresponding to monoclinic zirconia or colouring oxides crystal phases were detected. Mean BFS (MPa) obtained for un-shaded group=1360.96±134.79 MPa, while that of the shaded group=1195.88±112.62 MPa. The One-way ANOVA test revealed statistically insignificant difference (P≥0.05) in BFS between the two groups. CLSM images of both groups showed the classical fracture patterns of brittle materials.

Conclusions: Shading of zirconia using powder mixing method could be a feasible technique for fabrication of shaded monolithic zirconia restorations with comparable properties to un-shaded ones.

Student Presenter

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: NONE