Papers by Author: Mehmet Yetmez

Abstract: Hydroxyapatite (HA) is a particularly attractive material for bone and tooth implants since it does not only closely resemble human tooth and bone mineral but it has also biologically proven to be compatible with these tissues. The applications of pure HA are restricted to non load bearing implants due to the poor mechanical properties of HA. Biomaterials of synthetic HA are highly reliable but the synthesis of HA is often complicate and expensive. Bioceramics of naturally derived biological apatites are more economic. Aim of the present work is to introduce sheep teeth dentine HA material as an alternative source of bioactive biomaterials for grafting purposes. The work was started with such a way that extracted sheep teeth were cleaned. The teeth were calcinated at 850°C in air. It was seen that enamel matter was easily separated from dentine after calcination. The collected dentine parts were crushed and ball milled. The powder was pressed between hardened steel dies to produce samples suitable for compression and microhardness tests. The obtained powder compacts were sintered at different temperatures, specifically 1000, 1100, 1200, and 1300°C in air. Results of microhardness and compression strength (along with the statistical analysis of these results) as well as those of SEM and XRD analyses are presented. In the literature, there is very little information about the mechanical properties of dentine and enamel matter derived from sheep, bovine and human. The highest compression strength value in the present study was measured around 146 MPa (from human dentine derived HA the highest value was almost 60 MPa after sintering at 1300°C). The best microhardness in the present study was found as nearly 125 HV. The results of this study showed that the HA material produced from sheep tooth dentine can be qualified as a promising source of HA needed to produce bioactive ceramics.

Abstract: The aim of this study is to produce and to investigate the mechanical and microstructural properties of composite materials made of hydroxyapatite, obtained from natural bovine bone and nano barium strontium titanium oxide (5 and 10 wt%). Compositions were mechanical alloyed and compacted to pellets. The samples were subjected to sintering at different temperatures between 1000oC and 1300oC. Compression strength, Vickers microhardness as well as density were measured. SEM and X-ray diffraction studies were also conducted. With increasing sintering temperature, microhardness, compression strength and density of composites increased. With increasing addition of nano barium strontium titanium oxide (BST) to bovine hydroxyapatite (BHA), microhardness values of composites decreased at all sintering temperatures, but compression strength and density values of composites showed different tendency. Compression strengths of BHA-composites at low sintering temperatures were nearly the same, but their compression strengths at high sintering temperatures decreased with increasing nano BST addition. The best mechanical properties were obtained at 1300°C sintering temperature with BHA-5wt% nano BST. Microhardness and compression strengths values of these nano–oxide composites are generally higher than that BHA-composites produced by traditional methods. Adding of nano-oxides to BHA could be a valuable method to produce rigid and high load carrying ability when compared with BHA-composites produced by conventional methods. Nano-HA and nano-oxides composites could be even better. Those nano-nano studies are still in progress.