Date of Award
Master of Dental Science (MDS)
Joo L. Ong, Ph.D.
Paul Bland, D.D.S. David Cagna, D.M.D., M.S. Yunzhi Yang, Ph.D.
silver, hydroxyapatite, silver doped hydroxyapatite, titanium, osseointegration, bacterial attachment
The clinical success of dental implants is determined mostly by surface properties of implants and interactions with surrounding tissues. Furthermore, clinical success of dental implants is directed by implant surfaces and bone cell responses that promote osseointegration and long-term stability. Hydroxyapatite (HA)-coated Titanium (Ti) implants have been widely used due to its effect on bone response. However, microbial infection is common. One material known to have anti-microbial properties is silver (Ag). However, the effects Ag has on osteoblastic activity as well as decrease bacterial load has yet to be determined.
In this study, the effect of Ag-doped HA coatings on initial bacterial adhesion and osteoblast cell proliferation, differentiation, and mineralization was investigated. Using a sol-gel process, HA coatings doped with 2 wt % AgNO3 were prepared. Coated surfaces were characterized using Xray diffraction (XRD). The osteoblast cell attachment, differentiation which is measured by alkaline phosphatase activity, and mineralization which is measured by osteocalcin activity were evaluated using human embryonic palatal mesenchyme cells (HEPM), an osteoblast precursor cell line. Initial bacteria adhesion was evaluated using an RP12 strain of Staphylococcus epidermidis (ATCC 35984) and the Cowan I strain of Staphylococcus aureus.
A significant difference in osteoblastic cell attachment over time was observed with 2% Ag-doped HA having the least cell attachment. The use of HEPM cells indicated no significant difference in alkaline phosphatase specific activity or osteocalcin activity among the 2% Ag-doped HA, HA, and Ti surfaces. Furthermore, the in vitro bacterial adhesion study indicated a significantly reduced number of S. epidermidis and S. aureus on Ag-doped HA surfaces when compared to HA and Ti surfaces.
Overall, it was concluded that 2% Ag-doped HA surfaces have similar osteoconductive activity when compared to HA and Ti surfaces. It was also concluded that the doping of HA with Ag minimized the adhesion of bacteria on its surface. Further studies on Ag-doped HA surfaces should involve long and short-term animal studies to evaluate its biocompatibility and ability to induce bone formation for implant stability, as well as bacterial adhesion properties. Furthermore, a decreased concentration of Ag may aid in an increasing osteogenic activity as well as have an antimicrobial effect.
Besu, Nicole , "Silver Doped Hydroxyapatite Coating on Titanium Surfaces and its Effect on Early Bone Response and Osseointegration" (2007). Theses and Dissertations (ETD). Paper 24. http://dx.doi.org/10.21007/etd.cghs.2007.0027.