Evaluation of the titanium Ti-6Al-7Nb alloy with and without plasma-sprayed hydroxyapatite coating on growth and viability of cultured osteoblast-like cells

BACKGROUND: Osseointegrated dental implants are currently recognized as a standard treatment method in dentistry. Titanium (Ti) and its alloys are the metals of choice for endosseous parts of currently available dental implants. Ti-6Al-4V is the most used Ti alloy, however; an improved version, Ti-6Al-7Nb, has been recently developed. METHODS: Rat osteoblast-like cells (osteo- 1 culture) were used to analyze the biocompatibility of Ti-6Al-7Nb alloy with and without hydroxyapatite (HA) coating. The cells were grown on culture Petri dishes on the top of either plain Ti-6Al-7Nb or HA-coated Ti-6Al-7Nb disks. Osteo-1 cells grown on plain culture dishes were used as controls. Growth and cell viability curves were obtained by scanning electron microscopy. For the growth and viability curves, 10(4) cells were seeded on 35 mm dishes. Cells from each group were counted, in triplicate at 3, 7, 11, and 15 days after seeding using the Trypan blue dye exclusion assay. RESULTS: The cells grew as multiple layers on both Ti-6Al-7Nb substrates, showing extracellular matrix only when grown on HA-coated Ti-6Al-7Nb disks. The cells grown on HA-coated Ti-6Al-7Nb grew more slowly than the other 2 groups, with significantly smaller cell numbers than control cultures at the end of the experimental time. Additionally, the HA coated Ti-6Al-7Nb group presented smaller percentage of cell viability when compared to the control group. However, no significant differences were observed between the Ti groups. CONCLUSIONS: The presence of HA on the Ti-6Al-7Nb surface impaired the cell growth and viability of osteo-1 cells. However, this coating improved the extracellular matrix formation. Thus, our cell viability and structural studies showed that Ti-6Al-7Nb with or without HA coating has relevant physical and biological properties as an implant material.