THE EFFECT OF TWO AGING METHODS ON THE FLEXURAL STRENGTH AND CRYSTAL STRUCTURE OF YTTRIA STABILISED ZIRCONIA POLYCRYSTALS (IN VITRO STUDY) | ||||
| Alexandria Dental Journal | ||||
| Article 11, Volume 42, Issue 2, December 2017, Page 193-197 PDF (254.71 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/adjalexu.2017.57926 | ||||
 View on SCiNiTO | ||||
| Authors | ||||
| Amr A. Elsheemy* 1; Samir I. Bakry2; Amir S Azer3; Tamer M Abdelrazik4 | ||||
| 1Instructor at the Conservative Dentistry Department, Faculty of Dentistry, Alexandria University, Alexandria, Egypt. | ||||
| 2Professor of Fixed prosthodontics, Faculty of Dentistry, Alexandria University, Alexandria, Egypt. | ||||
| 3Lecturer of Fixed prosthodontics, Faculty of Dentistry, Alexandria University, Alexandria, Egypt | ||||
| 4Assistant professor, Polymer research department, City of Scientific Research and Technological Applications, Alexandria University, Egypt. | ||||
| Abstract | ||||
| INTRODUCTION: Dental zirconia restorations present long-term clinical survival and stay in service within the oral environment for many years. However, low temperature degradation could affect their mechanical properties and survival. Objectives: To investigate the effect of two aging methods on the flexural strength and crystal structure of yttrium-stabilized zirconia (YTZP). MATERIALS AND METHODS: Thirty bar specimens were prepared from a Yttria stabilized zirconia polycrystals and were divided into 3 groups (control, aged for 720,000 mechanical loads of 50N and 3600 thermal cycles, aged for 1 hour using autoclave). The aging procedures represent 3 years of clinical use. The specimens were loaded until fracture and the crystalline phase polymorphs of the material (tetragonal, t, and monoclinic, m, zirconia) were investigated by x-ray diffraction (XRD). Further investigations were done using scanning electron microscope (SEM). Data was statistically analysed using ANOVA test. RESULTS: Group B and C showed no statistical significance in their flexural strength with means of their break force (793.23±164.03) and (780.97 ± 257.25) respectively but statistically significant and higher than group A with mean (549.7 ± 54.14). The XRD showed nearly no change in the crystal structure between group A and B but an increase in the percent of monoclinic phase in group C. The SEM demonstrated a relatively homogenous size with particle size ranged between 400 to 570 µm for group A, while Group B and C showed an increase in particle size between 768 to 1150 µm respectively. CONCLUSIONS: Both aging methods caused changes in the flexural strength and structure of the zirconia specimens with no significant difference between them. | ||||
| Keywords | ||||
| Fixed prosthodontics; Zirconia; aging; Low temperature degradation | ||||
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