Abstract
Purpose The stress shielding effect caused due to the mechanical mismatch between the solid titanium and the surrounding bone tissue warrants the utilization of a mechanically and biologically compatible material such as the titanium-hydroxyapatite (Ti-HA) functionally graded material (FGM) for dental implants. This study is aimed at fabricating a Ti-HA FGM with superior mechanical and biological properties for dental implantation. Materials and Methods We fabricated a Ti-HA FGM with different Ti volume fractions (VFs) using HA and Ti powders. Ti-HA was characterized by studying its mechanical properties. Cytotoxicity was examined using a Cell Counting Kit-8 assay and an LDH cell cytotoxicity assay. Scanning electron microscopy was performed on an XL30 environmental scanning electron microscope (ESEM). Alkaline phosphatase (ALP) and transforming growth factor (TGF-β1) expressions were quantitatively monitored using enzyme-linked immunosorbent assay (ELISA) kits. The expressions of TGF-β receptors and ALP genes were measured using real-time polymerase chain reaction. The Ti-HA FGM dental implants were placed in beagle dogs. Microcomputed tomography (CT) and hard tissue slices were performed to evaluate the bone-implant contact (BIC) and bone volume over total volume (BV/TV). Results The density and mechanical properties of the Ti-HA exhibited various graded distributions corresponding to VF. Based on the results of the Cell Counting Kit-8 (CCK-8) and lactate dehydrogenase (LDH) assays, the difference in cytotoxicity between the two groups was statistically nonsignificant (P = 0.11). The ALP and TGF-β1 levels were slightly upregulated. The transcript levels of ALP and TGF-βRI were higher in the Ti-HA groups than in the Ti group at 7 days, whereas the transcript levels of TGF-βRII exhibited no obvious increase. The BIC did not exhibit significant differences between the Ti and Ti-HA FGM groups (P = 0.0504). BV/TV showed the Ti-HA FGM group had better osteogenesis (P = 0.04). Conclusion Ti-HA FGM contributes to the osteogenesis of dental implants in vivo and in vitro.
Highlights
Anterior tooth loss affects aesthetics, whereas posterior tooth loss affects mastication
The Ti-HA functionally graded material (FGM) composed of Ti with lower volume fractions (VFs) had relatively more grooves than those composed of Ti with higher VFs
lactate dehydrogenase (LDH) assay was used to investigate whether the decreased metabolic activity of MC3T3-E1 cells after longer FGM exposure was related to the cytotoxic effects of the FGM (Table 2)
Summary
Anterior tooth loss affects aesthetics, whereas posterior tooth loss affects mastication. Dental implants are usually considered the optimum treatment option for tooth loss. Dental implants made of titanium and titanium alloys are considered the gold standard and have been successfully used for a variety of indications such as abutment for removable prostheses, fixed single-tooth reconstructions, and fixed dental prostheses [3]. The mechanical mismatch between the solid titanium and the surrounding bone tissue creates a stress shielding effect, complicating the process of osseointegration and bone remodeling. Their short-term results were satisfactory with a 5-year success rate as high as 90%, the long-term results were still not satisfactory [4].
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