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The transcription factor Cbfa1 regulates osteoblast differentiation and expression of genes necessary for the development of a mineralized phenotype. The purpose of this study was to determine if Cbfa1 and BSPII gene expression are influenced by implant surface microtopography. Osteoblasts were cultured on 600-grit (grooved) or sandblasted (roughened) cpTi implant discs. Mineralization was evaluated by Alizarin-Red-S staining. Real Time PCR was used for quantitative analysis of Cbfa1 and BSPII gene expression. Enhanced mineralization was seen in osteoblasts grown on roughened implant surfaces relative to tissue culture plastic. Real Time PCR showed significant (P < 0.05) increases in Cbfa1 gene expression in cells grown on roughened, as compared with grooved, implant surfaces. BSPII gene expression was also increased on rough surfaces in the UMR cells, but was reduced in the rat calvarial osteoblast cultures. These results suggest that osteoblast gene expression and mineralization are affected by roughened implant surface microtopographies during osseointegration of dental implants.

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Organic phosphate, in particular beta-glycerophosphate (beta-GP), has been used to induce mineralization in cell culture systems. It serves as a source of inorganic phosphate when hydrolyzed by alkaline phosphatase. This study examined the effect of supplemental calcium and phosphate as well as the influence of various metabolic inhibitors on mineralization in a rat osteoblast-like cell-culture system. Mineralization was induced by supplementation of 1.8 mM of Ca(+2) and 5 mM of beta-GP or Pi. Mineral deposits associated with in vitro mineralization were revealed under SEM and TEM. Levamisole (10-100 microM) inhibited alkaline phosphatase activity and effectively reduced mineral formation. Actinomycin (500 ng/mL) and cycloheximide (50 microg/mL) also reduced mineral depositions by blocking RNA synthesis and protein synthesis, respectively. Levamisole and beta-GP did not appear to influence DNA synthesis. Spontaneous precipitation of calcium phosphate mineral was not detected in the culture medium with calcium and phosphate supplements in the absence of cell culture. The findings suggest that an elevated concentration of calcium and phosphate is crucial for in vitro mineralization. Furthermore, the mineralization process is associated with biologic events rather than with a spontaneous precipitation of calcium phosphate mineral. In view of the degradation potential of hydroxyapatite (HA)-coated implants, these results may be a viable indication that HA enhances bone formation through a similar mechanism.

Osteogenesis involves the recruitment of multipotent mesenchymal cells and the progressive differentiation of these cells into osteoblasts. The transcription factor Runx2 regulates osteoblast differentiation and expression of genes necessary for the development of a mineralized phenotype. The purpose of this study was to determine if preosteoblast cell differentiation associated with Runx2 and osteocalcin gene expression was influenced by implant surface microtopography. Human embryonic palatal mesenchymal cells (HEPM cells) were cultured on grooved or roughened cpTi implant discs. Cell phenotypes were evaluated with epifluorescent microscopy. Real-time PCR was used for quantitative analysis of Runx2 and osteocalcin gene expression. HEPM cells mineralized when grown on rough and grooved implant surfaces relative to tissue culture plastic. Real-time PCR showed significant (p < 0.05) increases in Runx2 and osteocalcin gene expression in cells cultured on rough and grooved implant microtopographies. These results suggest that preosteoblast cell differentiation is affected by implant surface microtopographies during osseointegration of dental implants.