Amorphous calcium phosphate/urethane methacrylate resin composites. I. Physicochemical characterization

Abstract

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.

Protein-repellent and antibacterial functions of a calcium phosphate rechargeable nanocomposite

“…To combat caries, calcium phosphate (CaP) composites were developed that could release calcium (Ca) and phosphate (P) ions to remineralize tooth lesions [24,25]. Re-incorporation of minerals into demineralized dentin could serve as sites for nucleation and remineralization [26].…”

“…NACP nanocomposite released Ca and P ions similar to traditional CaP composites [24,25], but with a 2-fold increase in strength for load-bearing restorations [23]. NACP composite was "smart" and rapidly neutralized acids to protect tooth structures [27].…”

“…However, the Ca and P ion release from previous CaP composites lasted for only a couple of months and then diminished over time [23][24][25]28]. Such short-term ion release is not suitable 4 for dental applications where the restoration should last for many years.…”

“…On the contrary, previous studies showed that composites accumulated more biofilms and plaque than other restorative materials [20][21][22]. Biofilm acids can decrease the local pH to a cariogenic range of 5.5 to 4, which could lead to tooth structure demineralization and secondary caries formation [23].To combat caries, calcium phosphate (CaP) composites were developed that could release calcium (Ca) and phosphate (P) ions to remineralize tooth lesions [24,25]. Re-incorporation of minerals into demineralized dentin could serve as sites for nucleation and remineralization [26].…”

“…NACP composite was "smart" and rapidly neutralized acids to protect tooth structures [27]. In a human in situ model, NACP composite inhibited caries at the enamel-composite margins [29].However, the Ca and P ion release from previous CaP composites lasted for only a couple of months and then diminished over time [23][24][25]28]. Such short-term ion release is not suitable 4 for dental applications where the restoration should last for many years.…”