Comparison of the two way of sintering procedure with polishing or glazing on flexural strength of monolithic zirconia fixed dental prosthesis

Abstract

Introduction: New ceramics while maintaining their aesthetic, they show acceptable strength, and zirconia is an example of these ceramics. The main goal of this study is comparison of the two way of sintering procedures with polishing or glazing on flexural strength of monolithic zirconia fixed dental prosthesis.

Methods & Materials: In this study there was 40 three-unit fixed dental prosthesis that extended from the first mandibular premolar to the first mandibular molar. Before the milling process the prepared teeth in typodont was scanned and the prosthesis designed in CAD unit, also the impression was taken from prepared teeth in typodont and a cobalt-chromium die was made and used in three point bending test. After that the prosthesis were milled from monolithic zirconia blank in CAM unit. The samples are divided into two groups according to their Fast or Long sintering speed (20 samples for each group) and then half of each group (10 samples) were polished with an electric handpiece in revers mode and 10000rpm speed and the other half of each group (10 samples) were glazed. The failure load was measured in Newton with three point bending test at a crosshead speed of 0.5 mm/min.

Results: the highest failure load was seen in long sintering groups and in total the greatest failure load was seen in long sintering/polished group (2026.5 ± 172.8 N) and the least failure load was seen in fast sintering/glazed group (1719.6 ± 143.9 N). There was a statistically significant difference between the mean fracture force in the two sintering methods (P-value<0.001), also in both groups of long sintering and fast sintering, polished subgroups have the greatest failure load than glazed subgroups but this difference is not statistically significant (P-value>0.05).

Conclusion: zirconia is a firm dental material for preparing full contour dental restorations. To obtain the maximum amount of failure load in this kind of restorations it is better to use long term sintering protocol.