A hybrid material comprised of beta-tricalcium phosphate (beta-TCP) and sodium lauryl sulfate (SLS) was prepared using a mechanochemical process, examined using particle size analysis, IR spectroscopy, (31)P, (23)Na, and (13)C solid-state NMR spectroscopy, and calcium dissolution experiments, and probed for in vitro remineralization of subsurface enamel lesions. Our results suggest that while the (31)P environments of beta-TCP remain unchanged during solid-state processing, there is noticeable shifting among the SLS (23)Na and (13)C environments. Therefore, given the structure of beta-TCP, along with our IR examinations and calcium dissolution isotherms, SLS appears to interface strongly with the cation deficient C(3) symmetry site of the beta-TCP hexagonal crystal lattice with probable emphasis placed on the underbonded CaO(3) polyhedra. To demonstrate the utility of the surface-active TCP material in dental applications, we combined the TCP-SLS with 5,000 ppm F (NaF) and evaluated the remineralization potential of subsurface enamel lesions via an in vitro remineralization/demineralization pH cycling dental model. Using surface and longitudinal microhardness measurements, the TCP-SLS plus 5,000 ppm F system was found to significantly boost remineralization of subsurface enamel lesions, with microhardness values increasing up to 30% greater than fluoride alone.

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The inability to sufficiently prevent and/or repair chemically-etched dental enamel serves as one example that underlines the importance and need for the development of innovative biomaterials for therapeutic applications. In this work we explored the seeding capability of 225 ppm and 1100 ppm fluoride with and without a novel β-tricalcium phosphate-silica-urea (TCP-Si-Ur) biomaterial (concentrations of 20, 40, 80, and 200 ppm) to mineralize into acid-etched bovine enamel. The nature of the mineralization was evaluated by measuring the fluoride and phosphate uptake into the eroded enamel, as well as the orthophosphate microstructure using infrared (IR) spectroscopy. These enamel fluoride uptake and IR experiments revealed a fluoride dose response exists for eroded enamel treated with 225 and 1100 ppm F. The inclusion of 20, 40, and 80 ppm TCP-Si-Ur with 225 ppm F was similar to 225 ppm F alone and did not produce a fluoride uptake dose response; however, 200 ppm TCP-Si-Ur combined with 1100 ppm F improved raw fluoride uptake relative to 1100 ppm F. Furthermore, we found the combination of either 225 ppm or 1100 ppm fluoride plus TCP-Si-Ur at different loading levels leads to unique and significant mineral integration into the PO4 enamel network, including the formation of P-F bonds. The observations reported herein demonstrate the combination of fluoride plus a novel TCP-Si-Ur biomaterial produces synergistic mineralization and bears significantly on eroded enamel microstructure.

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