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Title:	Reutilisation of remnants from zirconia blanks for dental crown applications
Authors:	Mohamed Milad Mohamed Aboras (P68304)
Supervisor:	Andanastuti Muchtar, Prof. Dr.
Keywords:	Crowns (Dentistry) Zirconium Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	15-Aug-2018
Description:	In dentistry, zirconia is used for dental restorations because of its high mechanical properties and excellent biocompatibility. However, according to this research, approximately 45% of zirconia blanks are discarded without being used and this amount to a huge waste. Thus, this study aims to recycle these remnants through comminution into powder through ball milling. For comparison, commercial yttriastabilized zirconia powder was used as a reference to the ball-milled powder produced in this study. The morphological characteristics of ball-milled powder were identified through transmission electron microscopy, and then evaluated in terms of chemical composition and phase structure. The suspensions of both materials were then prepared through colloidal processing. Parameters were determined to achieve high colloidal stability in zirconia suspension. This process is important to minimize the agglomeration of zirconia powder during colloidal processing. Next, green bodies were slip-casted through an optimized colloidal process (a) accompanied with, and (b) without Cold Isostatic Pressing (CIP), and (c) fabricated via uniaxial pressing accompanied with CIP. After that, green bodies of ball-milled and commercial zirconia were sintered at four different sintering temperatures from 1300 °C to 1600 °C. The effects of sintering temperature and processing method on the mechanical properties of the sintered samples were investigated. Structural characterization was accomplished through XRD whilst the morphology of the samples was examined via field emission scanning electron microscopy (FESEM). The zeta potential results revealed that the highest suspension stability was achieved at pH 3 and 2 for ballmilled and commercial zirconia, respectively. The density of the sintered samples from ball-milled powder (98%) was similar to that of the commercial samples (98.9%). The mechanical properties of the ball-milled samples exhibited comparable properties to the commercial ones, where the difference between the hardness of both materials is 0.49 GPa and 30 MPa in mean flexural strength. The FESEM micrographs of the samples with the highest mechanical properties showed a dense and homogeneous microstructure with low porosities. XRD also demonstrated that the phase was 100% tetragonal without a monoclinic phase for both materials. In this study, the ball-milled zirconia exhibited good physical and mechanical properties in terms of their density, hardness, and flexural strength with a homogeneous and fine microstructure. Meanwhile, the surface roughness (Ra) evaluation showed the ballmilled and commercial zirconia had smooth surfaces with 12.96 and 21.57 nm, respectively. This study can be used as a guideline for the preparation of zirconia from remnants of nanozirconia blanks in dental crown applications.,Ph.D.
Pages:	153
Call Number:	TP245.Z8A246 2018 3 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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