Dental glass‐reinforced composite for caries inhibition: Calcium phosphate ion release and mechanical properties

The two main challenges facing dental composite restorations are secondary caries and bulk fracture. Previous studies developed whisker‐reinforced Ca‐PO 4 composites that were relatively opaque. The objective of this study was to develop an esthetic glass particle‐reinforced, photo‐cured calcium phosphate composite. Tetracalcium phosphate (TTCP) particles were incorporated into a resin for Ca and PO 4 release, while glass particles provided reinforcement. Ion release and mechanical properties were measured after immersion in solutions with pH of 7, 5.5, and 4. For the composite containing 40% mass fraction of TTCP, incorporating glass fillers increased the strength ( p < 0.05). Flexural strength (Mean ± SD; n = 6) at 30% glass was 99 ± 18 MPa, higher than 54 ± 20 MPa at 0% glass ( p < 0.05). Elastic modulus was 11 GPa at 30% glass, compared to 2 GPa without glass. At 28 days, the released Ca ion concentration was 4.61 ± 0.18 mmol/L at pH of 4, much higher than 1.14 ± 0.07 at pH of 5.5, and 0.27 ± 0.01 at pH of 7 ( p < 0.05). PO 4 release was also dramatically increased at cariogenic, acidic pH. The TTCP‐glass composite had strength 2–3 fold that of a resin‐modified glass ionomer control. In conclusion, the photo‐cured TTCP‐glass composite was “smart” and substantially increased the Ca and PO 4 release when the pH was reduced from neutral to a cariogenic pH of 4, when these ions are most needed to inhibit tooth caries. Its mechanical properties were significantly higher than previous Ca, PO 4 , and fluoride releasing restoratives. Hence, the photo‐cured TTCP‐glass composite may have potential to provide the necessary combination of load‐bearing and caries‐inhibiting capabilities. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010