1030 Amorphous Calcium Phosphate-Resin Nanocomposite: Thermal-Cycling, Three-Body Wear, and Two-Year Water-Aging

Friday, March 23, 2012: 3:30 p.m. - 4:45 p.m.
Presentation Type: Poster Session
J.L. MOREAU1, M.D. WEIR1, K. ZHANG1, A.A. GIUSEPPETI2, L. CHOW2, J. ANTONUCCI3, and H.H. XU1, 1Endodontics, Operative Dentistry and Prosthodontics Department, University of Maryland Dental School, Baltimore, MD, 2Paffenbarger Research Center, American Dental Association Foundation, Gaithersburg, MD, 3Biomaterials/Plymers Division, NIST, Gaithersburg, MD
Half of all dental restorations fail within 10 years, with secondary caries and restoration fracture being the main reasons.  Calcium phosphate (CaP) composites can release Ca and PO4 ions and remineralize tooth lesions.  However, there has been no report on their long-term mechanical durability. 

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.

This abstract is based on research that was funded entirely or partially by an outside source: Supported by NIH DE14190 and DE17974 (HX), NIST, and the ADAF

Keywords: Composites, Dental materials, Long-term durability and Wear