Promotion of bone regeneration on titanium implants through a chemical treatment process using calcium phosphate slurry: Microscopic analysis, cellular response, and animal experiment.

The present study provides scientific evidence that a new chemical treatment process using calcium phosphate slurry promotes bone regeneration on titanium (Ti) implants. The material's surface modified by the treatment was analyzed using microscopic observation and the bone regeneration efficacy was evaluated both in vitro and in vivo. Formation of a thin hydroxyapatite layer with a thickness of about 50 nm and an increase of surface roughness were confirmed by microscopic observations. Histological evaluation of rat femora implanted with the specimens showed that the areas of the specimens directly attached to bone tissue were significantly more extensive than those implanted with control Ti at 2 and 8 weeks. Likewise, on the treated Ti, ALP activity, osteopontin, osteocalcin, and calcium contents of rat bone marrow stromal cells were significantly higher than on the control Ti. Furthermore, reverse transcription polymerase chain reaction showed greater expression of messenger ribonucleic acid encoding Cbfa1 and collagen type1 on the treated Ti at 2 weeks. Based on these results, we concluded that the new process was effective to enhance the osteoconductivity of Ti. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2716-2724, 2018.

Fatigue property of a bioabsorbable magnesium alloy with a hydroxyapatite coating formed by a chemical solution deposition.

A hydroxyapatite (HAp) coating was directly formed on an extruded AZ31 magnesium alloy by a single-step chemical solution deposition. The HAp coating consists of an outer porous HAp layer, an inner continuous HAp layer, and a thin intermediate MgO layer, and the inner HAp and MgO layers are composed of nanocrystals. Tensile and fatigue tests were performed on the HAp-coated AZ31 in air. The HAp coating microscopically showed neither crack nor detachment at 5% static elongation (1.5% residual strain). With further elongation under tensile stress, cracks were formed perpendicularly to the tensile direction, and fragments of the coating detached with a fracture inside the inner continuous HAp layer. The fatigue strengths at 10(7) cycles (fatigue limit) of HAp-coated and mechanically polished AZ31 were ca. 80 MPa and ca. 90 MPa, respectively. The slight decrease in the fatigue limit with the HAp coating is attributed to small pits with a depth of ca. 10 µm formed on the substrate during the HAp-coating treatment. The HAp coating remained on the specimen without cracks after 10(7) cycles at the fatigue limit, which provides ca. 3% cyclic elongation.