Evaluation of hardness and fracture resistance of surface treated Zirconia on enamel wear : An In-vitro study / Mostafa ElSayed AbouShahba ; Supervised Hesham Katamish , Mona Elagroudy

Thesis (Ph.D.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Prosthodontics

Two types of InCoris zirconia blocks were used in this study (ZI and TZI), Stainless Steel dies with dimensions of maxillary molars were used, duplicated using addition silicon impression material to form twenty four epoxy dies, then dies were scanned by the OmniCam. Software designing of crowns and copings was performed, then milling of the presintered blocks was done followed by separation of crowns and copings from the blocks and finishing. Sintering of zirconia blocks was done afterwards, regarding the copings feldspathic porcelain was used with the layering technique to veneer the copings to produce full anatomic crowns. All samples were then polished using special polishing kit for zirconia and glass ceramics and thermal ageing was done for two group using an autoclave at 135{u00B0}C and 2 atmospheric pressure for 5 hours. The twenty four specimens were weighed before wear testing using a sensitive electronic balance then inserted in a custom made wear machine that simulated the wear mechanism that occurs in the oral cavity with natural mandibular molars as antagonists under a weight of 5kg (49 N) and the rotation was of 240 cycles/min, the total time of wear was 8 hours, so the total cycles performed were 120,000 cycles. The twenty four specimens were weighed again after wear testing for the weight loss measurements determination. One specimen from each tested group was randomly selected and viewed under Scanning Electron Microscope in order to determine the wear pattern. Specimens over their corresponding previously poured epoxy dies were loaded with 5 kN until failure occurred. Vicker{u2019}s hardness testing was the performed for all the specimens in order to detect Vicker{u2019}s hardness number

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