Objectives: To investigate the wear, thermal-cycling, and water-aging of composites containing amorphous calcium phosphate nanoparticles (NACP).
Methods: NACP of 112-nm and glass particles were used to fabricate four composites with fillers of: (1) 0% NACP+75% glass; (2) 10% NACP+65% glass; (3) 15% NACP+60% glass; and (4) 20% NACP+50% glass. Thermal-cycling was performed at 5ºC and 60ºC water baths for 105 cycles. Wear was performed for 4x105 cycles. Water-aging lasted for two years.
Results: After thermal-cycling, flexural strength (mean±sd; n=6) of nanocomposite with 20% NACP was (89±13)MPa, slightly higher than (80±14)MPa of a commercial composite control (p>0.1), and much higher than (32±2)MPa of resin-modified glass ionomer (p<0.05). Wear depth increased with increasing NACP filler level. Wear depths of NACP nanocomposites were within the range for commercial controls. After 2 years of water-aging, flexural strengths were (64±10)MPa for composite with 0% NACP, (61±8)MPa for 10% NACP, (50±8)MPa for 15% NACP, (46±9)MPa for 20% NACP, and (36±12)MPa for the commercial composite control. They were all much higher than (15±2)MPa for resin-modified glass ionomer (p<0.05). The mechanism of strength loss for resin-modified glass ionomer was identified as microcracking and air-bubbles. NACP nanocomposites and control composite were generally free of microcracks and air-bubbles.
Conclusions: Combining NACP nanoparticles with reinforcement glass-particles resulted in novel nanocomposites with long-term mechanical properties higher than those of commercial controls, and wear within the range of commercial controls. These strong long-term properties, plus the Ca-PO4 release and acid-neutralization capability reported earlier, suggest that the new NACP nanocomposites may be promising for stress-bearing and caries-inhibiting restorations.
Keywords: Composites, Dental materials, Long-term durability and Wear
See more of: Dental Materials 7: Polymer-based Materials-Physical Properties and Performance