Mechanical properties of bioactive amorphous calcium phosphate/methacrylate composites

The aim of this study was to determine whether amorphous calcium phosphate (ACP)-containing composites, which have the ability to release mineralizing levels of Ca and PO4 ions, have appropriate mechanical properties for use as base and lining materials.

Composites of pyrophosphate-stabilized ACP particulates (mass fraction of 40%) and photo-activated methacrylate resins (mass fraction of 60%) were tested for biaxial flexure strength (BFS), diametral tensile strength (DTS), and compressive strength (CS). Hydroxyapatite (HAP; mass fraction of 40%), and micro-sized glass (mass fraction of 50%) composites as well as a commercial visible light curable base/liner were also tested. The significance between mean values was determined by Student-Newman-Keuls multiple comparisons (p < 0.05).

BFS of dry and wet (24 h at 37 degrees C in water) ACP composites (60.3 and 62.0 MPa, respectively) were significantly lower than those of the comparison materials (79.2-109.3 MPa). CS values were likewise lower (62.9 MPa dry and 67.6 MPa wet vs 80.6-196.8 MPa) except for the wet base/liner (58.5 MPa). DTS of the dry ACP composite (21.8 MPa) was comparable with that of the HAP (22.8 MPa) and glass (25.5 MPa) composites, but lower than that of the base/liner (36.2 MPa). DTS decreased significantly when the ACP composite was wet (17.8 MPa).

These results suggest that the remineralizing ACP polymeric composites, although mechanically weaker in some respects than other polymeric composites, have properties suitable for use as base and lining materials.