Owen M. Clarkin

Strontium-based glass polyalkenoate cements for luting applications in the skeleton.

Glass Polyalkenoate Cements (GPCs) based on strontium calcium zinc silicate (Sr-Ca-Zn-SiO2) glasses and high molecular weight poly(acrylic acid) (PAA) have been shown to exhibit suitable mechanical properties for orthopaedic arthroplasty applications, however for vertebroplasty and other medical luting applications these cements have working and setting times which are unsuitable for such applications. In this study GPCs based on Sr-Ca-Zn-SiO 2 glasses and low molecular weight PAA were evaluated for orthopaedic luting applications. GPCs based on four different glasses; BT100 (0.16CaO, 0.36ZnO, 0.48SiO2), BT101 (0.04SrO, 0.12CaO, 0.36ZnO, 0.48SiO 2), BT102 (0.08SrO 0.08CaO, 0.36ZnO, 0.48SiO2) and BT103 (0.12SrO 0.04CaO, 0.36ZnO, 0.48SiO2) and two PAAs (MW; 12,700 and 25,700) were examined. These cement formulations exhibited handling properties potentially suitable for luting applications as well as mechanical strengths which were similar to those of trabecular bone. Upon immersion in simulated body fluid, the GPCs showed sustained growth of a calcium phosphate layer on the surface of the cement indicating that these cements were bioactive in nature.

Antibacterial analysis of a zinc-based glass polyalkenoate cement.

Infection following surgery can result in significant pain and morbidity for patients undergoing vertebroplasty/kyphoplasty, and often results in revision surgery. This study focuses on the development of Al-free glass polyalkenoate cements (GPCs) based on 0.04SrO—0.12CaO—0.36ZnO—0.48SiO 2 glass, with the intent of optimizing their antibacterial efficacy by incorporating low—molecular-weight polyacrylic acids (PAA) and trisodium citrate (TSC), and evaluating the resultant GPCs against bacteria relevant to spinal infections, P. aeruginosa and E. coli. Ion-release profiles were determined for the GPC formulation containing E6 PAA (Cement A) and E7 PAA (Cement B), and Zn, Na, and Sr release was recorded over 1, 7, and 30 days. Inhibition was found in E. coli at each time period (0—30 days) and this generally decreased with exposure time in water. The largest GPC inhibition zones were produced by Cement A (6 mm); however the control material Simplex P + tobramycin produced much higher inhibition zones (11 mm). When testing the GPC against P. aeruginosa, inhibition was only present at the 0-day time period. Simplex P + tobramycin was found to produce inhibition at each time frame. Analysis of the agar from the inhibition zone of the E. coli test revealed that there is a significant change in Zn concentration as compared to a control agar specimen, which suggests that Zn release is responsible for the antibacterial effect of the GPCs.

Silica-Based and Borate-Based, Titania-Containing Bioactive Coatings Characterization: Critical Strain Energy Release Rate, Residual Stresses, Hardness, and Thermal Expansion

Silica-based and borate-based glass series, with increasing amounts of TiO2 incorporated, are characterized in terms of their mechanical properties relevant to their use as metallic coating materials. It is observed that borate-based glasses exhibit CTE (Coefficient of Thermal Expansion) closer to the substrate’s (Ti6Al4V) CTE, translating into higher mode I critical strain energy release rates of glasses and compressive residual stresses and strains at the coating/substrate interface, outperforming the silica-based glasses counterparts. An increase in the content of TiO2 in the glasses results in an increase in the mode I critical strain energy release rate for both the bulk glass and for the coating/substrate system, proving that the addition of TiO2 to the glass structure enhances its toughness, while decreasing its bulk hardness. Borate-based glass BRT3, with 15 mol % TiO2 incorporated, exhibits superior properties overall compared to the other proposed glasses in this work, as well as 45S5 Bioglass® and Pyrex.