Behavior of Ti/HA in Saliva at Different Temperatures as Restorative Materials

Abstract

Titanium and hydroxyapatite (HA) are well-known materials applied as biomaterials. Ti shows good mechanical properties and corrosion resistance, whereas HA possesses excellent biocompatibility and bioactivity but weak mechanical properties. The combination of the Ti and HA properties is expected to produce good corrosion resistance. Corrosion behavior of Ti/HA as composite (70Ti/30HA) and functionally graded material (Ti/HA FGM with five layers) has been investigated in saliva at pH 4.4 at five temperatures 10, 20, 30, 40, and 50 °C to use it as restorative material. There is reason for concern about the weak ceramic/metal bond and the integrity of this interface over a long-term performance under functional loading, therefore Ti/HA as FGM was fabricated to get good cohesive force between metal (Ti) and ceramic (HA) through the graduated layers. The corrosion results of Ti/HA materials were compared with that of pure Ti. The X-ray diffraction patterns and SEM of the composite showed that the HA decomposed and formed secondary phases which have biocompatibility in human body. These phases are mainly Ca5(PO4)3(OH), Ti4P3, CaO, Ca4O(PO4)2, and β-TCP. The results showed that the corrosion rate of Ti/HA as composite and FGM was lower than that for pure Ti due to the role of HA which forms phases that reduce the reactivity of titanium to dissolve in saliva over experimental temperatures. Also, the data of polarization resistance for Ti/HA materials were higher than that for pure Ti in saliva. Biocompatibility test showed that Ti/HA materials gave good absorption to culture cells, and functionally graded material had better absorbance than composite.