Metal-oxide nanoparticles for the reinforcement of dental restorative resins

The synthesis of highly radiopaque metal oxide nanoparticles that have been surface-functionalized to prevent interparticle associations was attempted. Functionalized metal oxide particles were produced by aqueous prehydrolysis of solutionized tantalum ethoxide or zirconium propoxide, followed by transesterification with formic acid. Highly mobile, transparent, and homogeneous composite resins with working time ranging from hours to weeks were produced using commercial, hydrophobic matrices such as GTE and nanoparticle loadings of up to 30 wt% with the use of vinyl silane surface groups. Both fracture mechanics and three point bending samples were produced as transparent, bubble-free monoliths. Centrifugation was used to remove bubbles prior to photocuring. The use of zirconia nanoparticles as a radiopaque reinforcing system was found to be considerably less expensive than that of tantalum oxide while posing no special difficulties in production.