ABSTRACT The growing trend for restorative glass-ceramic materials has pushed on to the development of the novel dental glass-ceramic systems. Improved biocompatibility, adequate strength, chemical and wear resistance and excellent aesthetic are the main criteria that make these materials clinically successful. The aim of the present study was to investigate the effect of small additions of T1O2, Z1O2, BaO and extra amounts of silica on the microstructural changes and biological properties of an apatite- mullite base glass-ceramic system. Glass transition temperatures and crystallization behavior were investigated using differential thermal analysis (DTA). Addition of Ti02, Z1O2, BaO and extra amounts of silica to the base glass led to some changes in the crystallization temperatures and morphology of the crystalline phases. DTA results showed that while T1O2 and BaO were effective in decreasing the crystallization temperature of the fluorapatite and mullite crystalline phases, Zr02 and the extra amounts of Si02 increased the crystallization temperature. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) revealed that the precipitated crystalline phases were fluorapatite [Caio(P04)6F2] and mullite [AleSijOu], which apart from the extra bearing Si02 specimen had rod-like morphology in the other specimens. The rod-like crystalline phases' lengths were small, i.e. <20 μηι, in the T1O2 and BaO containing glass-ceramics, but small addition of Zr02 enhanced the length of crystalline phases to approximately 50 μπι. MTT assay was used for cell proliferation assessment. The toxicity of glass-ceramic samples was assessed by seeding the osteosarcoma cells (MG63) on powder extracts for 7, 14 and 28 days. MTT results showed that glass-ceramic samples were almost equivalent concerning their in-vitro biological behavior.

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