May 11, 2007
Scientists have scored high marks over the years in reducing the polymer shrinkage that initially limited dental composites as a reliable restorative material. But the report card is less impressive in preventing additional decay, or secondary caries, a frequent cause of premature composite replacement. In two recently published articles, a team of NIDCR supported scientists report they are off to a good start in possibly solving the problem. They have developed a composite filler that combines (1) ceramic whiskers for polymer-reinforcing durability and (2) ion-releasing calcium phosphate particles that continuously remineralize the filled tooth and prevent secondary decay.
As published in the April issue of the Journal of Biomedical Materials Research Part B: Applied Biomaterials, the scientists synthesized for the first time nano-sized particles of monocalcium phosphate monohydrate, or MCPM. Starting with a Bis-GMA/TEGDMA monomer solution, which will polymerize into the composite’s resin backbone, they incorporated various ratios of MCPM particles and silica fused whiskers as filler. Each composite was then immersed from one to 56 days to measure its release of calcium phosphate. They found their nanocomposites had “substantial” calcium phosphate release and matched or exceeded the mechanical properties of commercially available dental composites.
In another study in the April issue of the Journal of Dental Research, the group synthesized for the first time nanoparticles of dicalcium phosphate anhydrous, or DCPA. Starting again with a BIS-GMA/TEGDMA monomer system, they mixed various ratios of DCPA and silica fused whiskers as filler. The composites also were immersed from one to 56 days to measure their calcium phosphate release. Again, they found the nanocomposites provided both a high level of stress relief and and calcium phosphate release at levels needed to remineralize developing decay.