Chemical affinity of 10-methacryloyloxydecyl dihydrogen phosphate to dental zirconia: Effects of molecular structure and solvents.

Objectives: To examine whether solvents and changing the molecular structure of 10-Methacryloyloxydecyl dihydrogen phosphate (10-MDP) affect its chemical affinity to Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP).

Methods: The present work investigated the chemical affinity between Y-TZP and 10-MDP dissolved in different solvents (acetone/ethanol/water or mixture) using X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and thermodynamic calculations. Shear bond strength (SBS) tests were used to evaluate the influence of different solvents on 10-MDP bonding. In addition, several phosphate ester monomer variants were created by changing the 10-MDP molecular structure. Changes included extending/shortening the spacer chain-length, and installing hydroxyl or carboxyl groups as side chains at different positions along the spacer chain. The thermodynamic parameters of the complexes formed between the 10-MDP variants and tetragonal zirconia were evaluated.

Results: The acquired data indicated that solvent is necessary for the formation of Zr-O-P bonds between 10-MDP and Y-TZP. Solvents affected the chemical affinity of 10-MDP to Y-TZP; acetone facilitated the best bonding, followed by ethanol. Changing the molecular structure of 10-MDP affected its chemical affinity to Y-TZP. The variants 15-MPDP, 12-MDDP, 6-hydroxyl-10-MDP and 6-carboxy-10-MDP all exhibited higher thermodynamic stability than 10-MDP when coordinated with tetragonal zirconia. In contrast, 2-MEP, 5-MPP, 10-hydroxyl-MDP, 10-carboxy-MDP, 5,6-dihydroxyl-10-MDP and 5,6-dicarboxy-10-MDP exhibited lower thermodynamic stability.

Significance: 10-MDP coordinates with zirconia through dissociating in solvents. Changing the molecular structure of 10-MDP theoretically affects its chemical affinity to Y-TZP.