Determining optimal surface roughness of TiO2 blasted titanium implant material for attachment, proliferation and differentiation of cells derived from human mandibular alveolar bone

In the complex process of bone formation at the implant-tissue interface, i mplant surface roughness is an important factor modulating osteoblastic fun ction. In this study, primary cultures of osteoblast-like cells, derived fr om human mandibular bone, were used. The aim was to examine the effect of v arying surface roughness of titanium implant material on cellular attachmen t, proliferation and differentiation. A recognized method of increasing sur face roughness and enlarging the surface area of titanium implants is by bl asting with titanium dioxide particles: the four specimen types in the stud y comprised surfaces which were machine-turned only, or blasted after turni ng, with 63-90 mum, 106-180 mum, or 180-300 mum TiO2 particles, respectivel y. The specimens were analyzed by scanning electron microscopy and confocal laser scanning. The turned samples had the smoothest surfaces: average hei ght deviation (S-a) of 0.20 mum. The roughest were those blasted with 180-3 00 mum particles, S-a value 1.38 mum. Blasting with intermediate particle s izes yielded S-a values of 0.72 mum and 1.30 mum, respectively. Cell profil e areas were measured using a semiautomatic interactive image analyzer. Fig ures were expressed as percentage of attachment. DNA synthesis was estimate d by measuring the amount of [H-3]-thymidine incorporation into trichloroac etic acid (TCA) insoluble cell precipitates. The specific activity of alkal ine phosphatase was assayed using p-nitrophenylphosphate as a substrate. Th e ability of the cells to synthesize osteocalcin was investigated in serum- free culture medium using the ELSA-OST-NAT immunoradiometric kit. After 3 h of culture, the percentage of cellular attachment did not differ significa ntly between specimens blasted with 180-300 mum particles and the turned sp ecimens. All blasted surfaces showed significantly higher [H-3]-thymidine i ncorporation than the turned surfaces (P<0.05), with the highest on the sur faces blasted with 180-300 <mu>m particles. Osteocalcin synthesis by the ce lls in response to stimulation by 1,25(OH)(2)D-3, was also significantly gr eater (P<0.05) on the surfaces blasted with TiO2 particles. However, analys is of alkaline phosphatase activity disclosed no significant differences am ong the four surface modifications. It is concluded that in this cellular m odel, the proliferation and differentiation of cells derived from human man dibular bone is enhanced by surface roughness of the titanium implant. Howe ver, increasing the size of the blasting particles to 300 <mu>m does not fu rther increase the initial attachment of the cells compared to turned surfa ces and those blasted with 63-90 mum particles.