Degree of conversion, mechanical properties and calcium release of an experimental composite containing calcium phosphate particles functionalized with 10-MDP

Abstract

The incorporation of calcium orthophosphate particles (CaP) in resin composites may assist in the remineralization of caries-affected dentin; however, it causes a decrease in the mechanical properties of the material. Particle functionalization seems to reduce this undesired effect. Experimental designs used in previous studies do not allow to state whether the observed increase in the fracture strength of composites containing functionalized CaP particles is due to the higher CaP-matrix bonding or simply to the lower effective CaP content in the composite, once part of the nominal CaP content is occupied by the functionalizing monomer thus making effective CaP content lower than the nominal content. Therefore, the null hypothesis is that the functionalization of CaP particles does not improve the performance of a composite compared to a material containing the same effective content of non-functionalized particles. DCPD particles (dicalcium phosphate dihydrate, CaHPO4.2H2O) will be functionalized with 10-MDP (10-methacryloyloxydecyl dihydrogen phosphate). The functionalizing content will be determined through elemental and thermogravimetric analyses. Five composites will be formulated (assuming a 10-MDP content of 5% by mass): (I) 60% DCPD_MDP and 40% BisGMA/TEGDMA, (II) 55% DCPD_NF (non-functionalized) and 45% BisGMA/TEGDMA , (III) 55% DCPD_NF, 40% BisGMA/TEGDMA and 5% 10-MDP mixed to the matrix, (IV) 55% barium glass and 45% BisGMA/TEGDMA (control 1) and (V) 55% barium glass , 40% BisGMA/TEGDMA and 5% 10-MDP mixed to the matrix (Control 2). The composites will be evaluated for degree of conversion, fracture strength and modulus (initial and after six months in water) and calcium ion release. Data will be assessed using ANOVA/Tukey's test (alpha:5%).(AU)