Improving Biomaterials from a Cellular Point of View
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0925-BB03-02
Improving Biomaterials from a Cellular Point of View V. G. Varanasi1, T. Vallortigara1, P. M. Loomer1, E. Saiz2, A. P. Tomsia2, S. J. Marshall1, and G. W. Marshall1 1 Preventive and Restorative Dental Sciences, Division of Biomaterials and Bioengineering, University of California, San Francisco, 707 Parnassus Avenue, San Francisco, CA, 94143 2 Materials Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 62103, Berkeley, CA, 94720, USA ABSTRACT Bioactive glass (6P55), used for coating Ti/Ti-alloy, was tested for its in vitro behavior in a comparative study with commercial BioglassTM (45S5) and commercial titanium alloy (Ti6Al4V). In vitro testing included pH and dissolution rate determination in simulated body fluid (SBF) along with in vitro cyto-compatibility testing. Similar dissolution behavior was seen for 6P55 and 45S5, demonstrating t ½ dependence and maximum pH of approximately 8.1 after 10 days of immersion. The dissolution rate of these glasses approached 0 after 15 days of immersion, which resulted in pH stabilization at less than 7.5. Cell culture studies showed that both glasses behaved in a similar fashion after 16 hours in culture. Both glasses had an increase in cell numbers of approximately 200-250%, whereas Ti6Al4V had a less pronounced cell number increase (~ 180%) relative to initial cell seeding density. INTRODUCTION In bone, Ti/Ti-alloy, hydroxyapatite (HA), calcium phosphate ceramics, and bioactive glasses have become standard implant materials. Ti was first used in endosseous implants for tooth prosthetics, with bone bonding with the overlying TiO2 layer. However, these implants are severely limited because Ti is only mechanically adherent to bone [1, 2]. Coating Ti with HA (Ca10(OH)2(PO4)6) has been attempted to improve bonding [1]; however, HA delaminates from Ti because of the large thermal expansion mismatch and only mechanical adhesion at the ceramic-metal interface. Bioactive glasses have become the implant material of choice for bone healing. The most well-known bioactive glass, BioglassTM [1-3] (45S5 Table I), has been used in many bone healing applications (such as bone grafts [4] and periodontal defects [5]). Bioglass is termed bioactive because it partially dissolves into physiological fluid, which leads to the formation of a crystalline apatite-like layer on the glass surface [6]. The apatite surface is suitable for bone-forming cells (osteoblasts) to adhere and proliferate. Yet, Bioglass does not bond well to Ti because of rapid hydroxyapatite crystallization; this leads to formation of pores within the glass and causes it to delaminate [7]. Recently, bioactive glasses (50-59 wt.% SiO2) have been developed to coat Ti for improved osteointegration [8]. These glasses are based on the Bioglass composition (relative to P2O5), but are well-adherent on Ti/Ti-alloy. In this study, we are testing the hypothesis that bioactive glasses used for Ti/Ti-alloy implant coatings have similar bioactive characteristics as Bioglass in that they partially disso
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