Dental Composites Based on Amorphous Calcium Phosphate - Resin
Composition/Physicochemical Properties Study
D. Skrtic1*
J.M. Antonucci2
1 Paffenbarger Research Center, American Dental Association Foundation,
National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
2 Polymers Division, National Institute of Standards and Technology,
Gaithersburg, MD 20899, USA
* To whom correspondence should be addressed.
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Abstract |
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This study explores how the resin composition/structure affects the
physicochemical properties of copolymers and their amorphous calcium phosphate
(ACP)-filled composites. A series of photo-polymerizable binary and ternary matrices are
formulated utilizing 2,2-bis[
p-(2'-hydroxy-3'-methacryloxypropoxy)phenyl]propane, 2,2-bis[
p-(2'-methacryloxypropoxy)phenyl]propane (EBPADMA), or a urethane
dimethacrylate as base monomers, and triethylene glycol dimethacrylate or hexamethylene
dimethacrylate (HmDMA) with or without 2-hydroxyethyl methacrylate (HEMA) as diluent
monomer. Unfilled copolymers and composites filled with 40% by mass zirconia-hybridized
ACP are evaluated for biaxial flexure strength (BFS), degree of conversion (DC), mineral
ion release, polymerization shrinkage (PS), and water sorption (WS). The average DC
values are 82-94% and 74-91% for copolymers and composites, respectively. Unrelated to
the resin composition, the PS values of composites are up to 8.4 vol.% and the BFS
values of wet composite specimens are on average 51 ± 8 MPa. The maximum WS
values attained in copolymers and composites reach 4.8 mass%. Inclusion of hydrophobic
HmDMA monomer in the matrices significantly reduces the WS. The levels of Ca and
PO4 released from all types of composites are significantly above the minimum
necessary for the re-deposition of apatite to occur. Elevated Ca, and to a lesser extent
PO4 release, is observed in HEMA-containing, ternary EBPADMA formulations.
Further resin reformulations may be needed to improve the PS of composite specimens.
Poor dispersion of 'as-synthesized' ACP within the composite contributes to their
inferior mechanical performance.
Key Words:
amorphous calcium phosphate, biaxial flexure strength, composite, copolymer, degree of vinyl conversion, ion release, polymerization shrinkage, water sorption
