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Structure-Composition-Property Relationships in Polymeric Amorphous Calcium Phosphate-Based Dental Composites†
Paffenbarger Research Center, American Dental Association Foundation, Gaithersburg, 20899, MD, USA
Polymers Division, National Institute of Standards and Technology, Gaithersburg, 20899, MD, USA
† Official contribution of NIST; not subject to copyrights in USA.
* Author to whom correspondence should be addressed.
Received: 30 October 2009; in revised form: 19 November 2009 / Accepted: 23 November 2009 / Published: 24 November 2009
Abstract: Our studies of amorphous calcium phosphate (ACP)-based materials over the last decade have yielded bioactive polymeric composites capable of protecting teeth from demineralization or even regenerating lost tooth mineral. The anti-cariogenic/remineralizing potential of these ACP composites originates from their propensity, when exposed to the oral environment, to release in a sustained manner sufficient levels of mineral-forming calcium and phosphate ions to promote formation of stable apatitic tooth mineral. However, the less than optimal ACP filler/resin matrix cohesion, excessive polymerization shrinkage and water sorption of these experimental materials can adversely affect their physicochemical and mechanical properties, and, ultimately, limit their lifespan. This study demonstrates the effects of chemical structure and composition of the methacrylate monomers used to form the matrix phase of composites on degree of vinyl conversion (DVC) and water sorption of both copolymers and composites and the release of mineral ions from the composites. Modification of ACP surface via introducing cations and/or polymers ab initio during filler synthesis failed to yield mechanically improved composites. However, moderate improvement in composite’s mechanical stability without compromising its remineralization potential was achieved by silanization and/or milling of ACP filler. Using ethoxylated bisphenol A dimethacrylate or urethane dimethacrylate as base monomers and adding moderate amounts of hydrophilic 2-hydroxyethyl methacrylate or its isomer ethyl-α-hydroxymethacrylate appears to be a promising route to maximize the remineralizing ability of the filler while maintaining high DVC. Exploration of the structure/composition/property relationships of ACP fillers and polymer matrices is complex but essential for achieving a better understanding of the fundamental mechanisms that govern dissolution/re-precipitation of bioactive ACP fillers, and, ultimately, the suitability of the composites for clinical evaluation.
Keywords: amorphous calcium phosphate; bioactivity; cellular response; dental composite; mechanical strength; polymerization; re-mineralization; resin
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O’Donnell, J.N.R.; Schumacher, G.E.; Antonucci, J.M.; Skrtic, D. Structure-Composition-Property Relationships in Polymeric Amorphous Calcium Phosphate-Based Dental Composites. Materials 2009, 2, 1929-1954.
O’Donnell JNR, Schumacher GE, Antonucci JM, Skrtic D. Structure-Composition-Property Relationships in Polymeric Amorphous Calcium Phosphate-Based Dental Composites. Materials. 2009; 2(4):1929-1954.
O’Donnell, Justin N. R.; Schumacher, Gary E.; Antonucci, Joseph M.; Skrtic, Drago. 2009. "Structure-Composition-Property Relationships in Polymeric Amorphous Calcium Phosphate-Based Dental Composites." Materials 2, no. 4: 1929-1954.