Amorphous calcium phosphate/urethane methacrylate resin composites. I. Physicochemical characterization.
Urethane dimethacrylate (UDMA), an oligomeric poly(ethylene glycol) extended UDMA (PEG-U) and a blend of UDMA/PEG-U were chosen as model systems for introducing both hydrophobic and hydrophilic segments and a range of compliances in their derived polymers. Experimental composites based on these three resins with amorphous calcium phosphate (ACP) as the filler phase were polymerized and evaluated for mechanical strength and ion release profiles in different aqueous media. Strength of all composites decreased upon immersion in saline (pH = 7.4). Both polymer matrix composition and the pH of the liquid environment strongly affected the ion release kinetics. In saline, the UDMA/PEG-U composite showed a sustained release for at least 350 h. The initially high ion release of the PEG-U composites decreased after 72 h, seemingly due to the mineral re-deposition at the composite surface. Internal conversion from ACP to poorly crystallized apatite could be observed by X-ray diffraction. In various lactic acid (LA) environments (initial pH = 5.1) ion release kinetics was much more complex. In LA medium without thymol and/or carboxymethylcellulose, as a result of unfavorable changes in the internal calcium/phosphate ion stoichiometry, the ion release rate greatly increased but without observable conversion of ACP to apatite.
Regnault
William F
WF
Center for Devices and Radiological Health, Food and Drug Administration, Rockville, MD, USA.
Icenogle
Tonya B
TB
Antonucci
Joseph M
JM
Skrtic
Drago
D
D010129:4-Aminobenzoic Acid / Q000737:chemistry; D000180:Acrylic Resins / Q000737:chemistry*; D001031:Apatites / Q000737:chemistry; D001672:Biocompatible Materials / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry*; D015394:Molecular Structure; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry*; D013499:Surface Properties; D013729:Terpenes / Q000737:chemistry; D013997:Time Factors; D062366:para-Aminobenzoates
D000180:Acrylic Resins; D001031:Apatites; D001672:Biocompatible Materials; D002130:Calcium Phosphates; D011108:Polymers; D011140:Polyurethanes; D013729:Terpenes; D062366:para-Aminobenzoates; C050845:urethane acrylate; D011092:Polyethylene Glycols; C048339:camphoroquinone; C020243:calcium phosphate; C030746:4-(dimethylamino)benzoic acid; D010129:4-Aminobenzoic Acid