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

Abstract

Titanium and hydroxyapatite (HA) are wellknown 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 Ca 5 (PO 4) 3 (OH), Ti 4 P 3 , CaO, Ca 4-O(PO 4) 2 , and b-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.

Killing Mechanisms of Chimeric Antigen Receptor (CAR) T Cells

“…In the murine system, however, CD8 + cytotoxic T lymphocytes (CTLs) rely on granule exocytosis and CD4 + CTLs resort to the Fas and Fas ligand (FasL) pathway to mediate cytotoxicity [57,58], whereas in the human system, CTLs (both CD8 + and CD4 + ) predominantly utilize the cytolytic perforin and granzyme axis to mediate target cell apoptosis [59]. In addition, when equipped with a CAR, human T cells of both subsets can effectively eradicate tumor cells in a MHC- and Fas-independent manner [60,61].…”

Microstructure and Mechanical Properties of Nano-Carbon Reinforced Titanium Matrix/Hydroxyapatite Biocomposites Prepared by Spark Plasma Sintering

“…In addition, the existence of Ca 5 (PO 4 ) 3 (OH), Ca 4 O(PO 4 ) 2 , CaTi 4 (PO 4 ) 6 , etc., which were mentioned in other literatures [ 15 , 16 , 51 , 52 , 53 ], were not detected by XRD ( Figure 4 ). Moreover, a small amount of Ti 17 P 10 , CaTiO 3 , Ca 3 (PO 4 ) 2 were detected.…”

Research Progress Regarding Interfacial Characteristics and the Strengthening Mechanisms of Titanium Alloy/Hydroxyapatite Composites

“…Compared with coating, there are similar complex chemical reactions in uncoated composite. Researchers revealed that some new phases, such as Ca 5 (PO 4 ) 3 (OH), CaTiO 3 , Ti x P y , β-Ti, Ti 2 O, CaO, Ca 4 O(PO 4 ) 2 , Ca 3 (PO 4 ) 2 (TCP), CaTi 4 (PO 4 ) 6 , etc., have appeared in Titanium alloys/HA composites prepared by powder metallurgy and other methods [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. The presence of calcium titanate produced by the reaction between Titanium and HA showed the existence of interfacial chemical reactions [ 27 ].…”

“…However, there are some problems such as stress shielding phenomenon, complex reactions, and so on [ 1 , 4 , 5 , 6 ]. Research showed that there were some new phases such as Ca 5 (PO 4 ) 3 (OH), CaTiO 3 , Ti x P y , β-Ti, Ti 2 O, CaO, Ca 4 O(PO 4 ) 2 , Ca 3 (PO 4 ) 2 (TCP), and CaTi 4 (PO 4 ) 6 in Ti alloy/HA composites after high temperature sintering [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. It reveals that there are complex reactions between Ti and HA when sintered at a high temperature.…”