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https://ptsldigital.ukm.my/jspui/handle/123456789/457422| Title: | Low temperature degradation and flexural strength of nano zirconia |
| Authors: | Intan Azimah binti Azman (P66132) |
| Supervisor: | Jasmina Qamaruz Zaman, Dr. |
| Keywords: | Zirconia polycrystalline ceramic low temperature degradation (LTD) Dissertations, Academic -- Malaysia |
| Issue Date: | 14-Sep-2015 |
| Description: | Zirconia is a polycrystalline ceramic, which it does not contain glass particles. The atoms are densely packed together, contributing to its superior mechanical properties and hence, suitable for posterior fixed partial dentures. However, their mechanical strength reduces overtime due to sensitivity to low temperature degradation (LTD) which leads to catastrophic fracture of the zirconia prosthesis. The aim of this research is to determine the effect of grain size on LTD and fracture toughness of nano zirconia. Sixty standardized discs specimen of 100 nm nano zirconia, 170 nm nano zirconia and Cercon® were hydrothermally aged in an autoclave at 134°C and 2 bar of water for 0, 5, 25,50 and 100 hours. The phase transformation was determined by x-ray diffraction (XRD). Microstructure analysis was done with atomic force microscopy (AFM) before and after ageing. Flexural strength was investigated in a biaxial flexural strength test. Selected fractured discs underwent Field Emmision Scanning Electron Microscope (FESEM) to measure depth of t-m transformation zone. XRD results showed increase of monoclinic phase content with increase of ageing time of each group but statistically it is only significant in the nano zirconia 100nm group and nano zirconia 170 nm (p <0.05). Atomic force microscopy showed evidence of grains pull out of the surface of the samples after ageing. Flexural strength of all groups decreases with increase hour of ageing from 0 hour to 50 hours, but gain in strength at 100 hours of ageing. Moderate correlation was found between the increasing monoclinic fraction and flexural strength. In conclusion, the grain size alone does not determine the extent of LTD. Fracture toughness initially reduces but eventually increases with further LTD due to transformation toughening.,Ijazah Doktor Pergigian |
| Pages: | 77 |
| Call Number: | WU20.5.I61L 2015 9 |
| Publisher: | UKM, Kuala Lumpur |
| Appears in Collections: | Faculty of Dentistry / Fakulti Pergigian |
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