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Effects of Calcium Phosphate Nanoparticles on Ca-PO₄ Composite

Paffenbarger Research Center, American Dental Association Foundation, National Institute of Standards and Technology, Building 224, Room A-153, Stop 8546, Gaithersburg, MD 20899-8546, USA.

^* corresponding author, hockin.xu{at}nist.gov

Nano-particles of dicalcium phosphate anhydrous (DCPA) were synthesized for the first time. The objectives of this study were to incorporate DCPA nano-particles into resin for Ca-PO₄ release to combat dental caries, and to investigate the filler level effects. Nano-DCPA and nano-silica-fused silicon nitride whiskers at a 1:1 ratio were used at filler mass fractions of 0–75%. The flexural strengths in MPa (mean ± SD; n = 6) of DCPA-whisker composites ranged from (106 ± 39) at 0% fillers to (114 ± 23) at 75% fillers, similar to (112 ± 22) of a non-releasing composite (TPH) (p > 0.1). The composite with 75% fillers in a NaCl solution (133 mmol/L, pH = 7.4, 37°C) yielded a Ca concentration of (0.65 ± 0.02) mmol/L and PO₄ of (2.29 ± 0.07) mmol/L. Relationships were established between ion-release and DCPA volume fraction V_DCPA: Ca = 4.46 V_DCPA^1.6, and = 66.9 V_DCPA^2.6. Nano-DCPA-whisker PO₄ composites had high strength and released high levels of Ca-PO₄ requisite for remineralization. These new nano-composites could provide the needed combination of stress-bearing and caries-inhibiting capabilities.

KEY WORDS: dental composite • nano-particles • whisker reinforcement • tooth caries inhibition • Ca and PO₄ ion release