Abstract
Objectives.Effects of zinc-eluting fillers on mechanical properties of orthodontic cement were investigated using zinc-eluting microcapsules and Zinc bioactive glass. 5 and 7 w/w% microcapsule loadings were observed without and with zinc glass. Formulations containing zinc glass were at 5, 10, and 15 w/w% loadings. 5 w/w% microcapsule formulations (without and with primer) were tested against Transbond XT on porcelain brackets to reveal any mechanical effects on shear bond strength (SBS).|Methods. Orthodontic cement formulations used Bis-GMA and TEDGMA monomers, standard glass (and/or zinc glass) (70 w/w% total), fumed silica, and (for some) microcapsules. Formulations were polymerized in 2mm by 2mm by 25mm molds, then tested using a MTS Insight Electromechanical – 1kN Standard Length material testing system in a bi-axial flexural strength test. SBS was similarly measured. Porcelain brackets were bonded to the enamel on bovine incisors, incubated, then sheared off using the MTS.|Results. A greater flexural strength appeared in the 1% : 4% group compared to the 0% : 5% group in the Zn MC : F/Ca/PO4 MC w/w% ratio trials (no zinc glass), p≤0.001. No significant differences were found in the corresponding 7 w/w% Zn MC : F/Ca/PO4 MC w/w% ratio trials, p≥0.05. No significant differences were observable in the trials using 5 w/w% microcapsules and 5,10, and 15 w/w% Zn bioactive glass, p≥0.05. The group that used 5, 10, and 15 w/w% Zn Bioactive Glass (no microcapsules) showed significant differences between the 5% and 10% sets, as well as between the 5% and 15% sets. SBS trials with porcelain brackets showed no significant differences between groups in all three trails, p≥0.05.|Discussion. A trend of increasing flexural strength with increasing Zn microcapsules was observable in the 7 w/w% Zn MC : F/Ca/PO4 MC w/w% ratio trials. A trend of decreasing flexural strength to increased zinc glass content appeared in the Zn bioactive glass sample sets (no microcapsules), p≤0.01. SBS trials showed the most difference between the microcapsule-containing orthodontic cement without and with primer sample sets, however insignificant. This study has found that zinc ion-eluting fillers effected neither flexural strength nor SBS mechanical properties in orthodontic cement.