Suitability evaluation of sol–gel derived Si-substituted hydroxyapatite for dental and maxillofacial applications through in vitro osteoblasts response

Si-hydroxyapatite (Si-HAP) has been used in orthopedic, dental, and maxillofacial surgery as a bone substitute. Objective The aim of this investigation was to study the effect of Si substitution into the hydroxyapatite matrices and evaluate the biocompatibility effects of Si-HAP material in vitro with human osteoblasts. Methods Silicon-substituted hydroxyapatite (Si-HAP) bioceramic materials were prepared by incorporating small amounts of silicon into the structure of hydroxyapatite [Ca10(PO4)6(OH)2, HAP] through a sol–gel method. A series of silicon substitutions ranging from 0, 1, 3 and 5 mol%, which are comparable to the measured silicon contents in natural bone, were performed. Results Single-phase Si-HAP was obtained upon calcining the as-prepared powders up to 800 °C since no secondary phases, such as tricalcium phosphate (TCP), tetracalcium phosphate (TeCP) or calcium oxide (CaO), were identified by X-ray diffraction analysis. The effects of silicon-substituted hydroxyapatite (Si-HAP) materials towards the responses of human osteoblast-like (HOB) cells were investigated and compared with pure hydroxyapatite. Significance The Si-HAP indicated a significant increase in cell growth density with culture time irrespective of the amount of Si substituted in HAP. A high Si content (5 mol%) appears to promote rapid bone mineralization, since large amount of calcium phosphate minerals started to develop across the ECM by day 31 for a sample containing 5 mol% Si. On the other hand, a high Si content may result in fast dissolution of the material, owing to a decrease of HAP crystallite size, which might not be ideal for cell attachment for prolonged time periods. An optimum level of Si appears to exist at 3 mol%, which balances these effects.