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Applying a porous hydroxyapatite (HA) coating on a titanium substrate is a widely used method to increase the biocompatibility and osteogenic potential of human embryonic palatal mesenchymal (HEPM) pre-osteoblasts. Thermal spraying is one of the most prevalent methods used to coat HA on titanium substrates due to its ease in processing and ability to produce coatings with good adherence, which affect positively the surface topography and coating performance. The objective of this work is to enhance the biocompatibility and osteogenic potential of HA coatings on titanium substrates. HA was first synthesized and then coated onto a titanium substrate by two distinct methods, i.e., the dry coating method and the wet coating method. The phase content was evaluated by X-ray diffraction (XRD). The particle morphology was observed by scanning electron microscopy (SEM). HEPM pre-osteoblasts were used to test the cell-material interaction in vitro, and thereafter, an alkaline phosphatase (ALP) test was conducted. The wet coating method enhanced the specific surface area, which in turn increased the cell proliferation on HA-coated titanium substrates. The in vitro test demonstrated that wet coatings resulted in enhanced cell attachment and ALP activity. This study shows that spraying HA using the wet coating method is a technique that can produce potentially bioactive bone-regeneration implants.

Background Compressive neuropathy is a recurring and challenging disease for patients, regardless of medical or surgical treatment. Neuropathological severity is associated with the force of mechanical compression. Available animal models do not address mechanical issues with reproducible outcomes. We used a chronic constriction injury model to analyze tension-controlled compressive neuropathy and achieve reproducible functional outcomes. New method We refined a modified animal model for chronic constriction nerve injury under controllable compressive tensile strength to target the unilateral sciatic nerve of adult rats. Sensory outcomes were evaluated using the Von Frey test. Muscle atrophy and nerve degeneration were analyzed, including markers of neural degeneration, neuroinflammation, and neuropathic pain in the affected nerve. Results The compressive force significantly affected the neuropathological severity of sensory dysfunction and muscle atrophy. Greater mechanical forces (i.e., tight-knot) contributed to muscle atrophy and hypoesthesia. Low forces (i.e., loose-knot) induced mechanical allodynia with better residual muscle weight. Well-controlled loose knotting can avoid myelin degradation while lessening neuroinflammation and macrophage infiltration. Neuropathic pain was enhanced with increased nociceptive pain markers expression within the affected nerve. Comparison with Existing Method(s): Our chronic constriction injury model, unlike previous models, controls the ligation forces applied for different levels of injury. Conclusion The functional influences of different compressive forces recapitulate the diverse clinical symptoms involved in clinical compressive neuropathy. This controllable and reproducible model of compressive neuropathy revealed the underlying molecular mechanisms of neural degeneration and inflammation. It will lead to the future development of translational therapeutics for neuropathic pain and nerve regeneration.

Strontium (Sr) and magnesium (Mg) have been reported to promote osteoblastic cell proliferation and to accelerate bone formation. However, the biofunctional effect on osseointegration caused by coating dental implants with hydroxyapatite (HA) incorporating both of these elements has not been investigated to date. The aim of this study was to examine bone formation and osseointegration in Sr- and Mg-doped HA-coated titanium implants. In this study, the flame-spraying technique was used to deposit Sr- and Mg-doped HA onto titanium discs and implants. The biocompatibility and alkaline phosphatase (ALP) activity of human embryonic palatal mesenchymal pre-osteoblasts on titanium discs was evaluated. In addition, the expression of the osteogenesis gene and the protein expression of Runt-related transcription factor 2 (RUNX2), osteopontin (OPN), and osteocalcin (OCN) on titanium discs were determined by using real-time polymerase chain reaction assays, Western blot analysis, and enzyme-linked immunosorbent assays. Ultimately, the effects of Sr- and Mg-doped HA on the osseointegration of implants were examined in beagle dogs. The results showed that of the groups tested, the 5Sr5Mg-HA group exhibited the highest biocompatibility, ALP activity, and mRNA and protein expression of RUNX2, OPN, and OCN. Prominent new bone ingrowth with osteoblasts and osteoid tissue was found in the 5Sr5Mg-HA group at 4 weeks and 8 weeks. In addition, the highest bone-to-implant contact ratio was found in the 5Sr5Mg-HA group compared to other groups at 8 weeks in beagle dogs. The results show the potential of using 5Sr5Mg-HA coating on dental implants for enhanced osseointegration. Statement of Significance Osseointegration is assessed according to the extent of bone-to-implant contact and is an indication of implant success. This study is the first to report that flame-sprayed Sr- and Mg-doped HA coatings on titanium surfaces enhance osseointegration and new bone apposition in a beagle dog model. Therefore, the use of titanium implants incorporating Sr and Mg might be advantageous for patients with a low bone density.