Effect of different 10-Methacryloyloxydecyl Dihydrogen Phosphate concentrations on the shear bond strength between zirconia and composite resin

Information from the abstract

Zirconia ceramics are widely used in restorative dentistry for their mechanical strength, but their lack of a glassy phase makes them resistant to conventional acid etching. While 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) is utilized to facilitate chemical bonding, the influence of monomer concentration on molecular coordination at the interface remains unclear. This study evaluated the effect of varying 10-MDP concentrations on shear bond strength (SBS) and investigated the underlying chemical bonding mechanisms. Specimens were randomly divided into nine groups ( n = 6): seven experimental groups treated with varying concentrations of experimental MDP solutions (2, 4, 6, 8, 10, 12, and 14% v/v in ethanol), a commercial MDP primer positive control (CMP; Z-Prime™ Plus), and a non-MDP primer-treated negative control (NMP). Zirconia surfaces were treated with these MDP solutions prior to bonding with flowable composite resin. Shear bond strength was measured using a universal testing machine. Chemical coordination modes were analyzed using 31 P Nuclear Magnetic Resonance (NMR) spectroscopy and Energy-Dispersive X-ray Spectroscopy (EDS) to correlate molecular configurations with SBS data. Shear bond strength was significantly influenced by MDP concentration, increasing from 2% (7.1 ± 0.4 MPa) to a peak at 10% (11.3 ± 0.8 MPa), followed by a significant decline at 12% (7.6 ± 0.7 MPa) and 14% (7.7 ± 0.8 MPa). 31 P NMR analysis revealed that these variations correspond to five distinct bonding configurations (S1–S5). The superior performance of the 10% concentration was associated with the highest proportion of the S2 configuration, representing ionically bonded bidentate complexes. In contrast, the reduction in SBS at higher concentrations coincided with a decrease in S2 intensity and the emergence of S3 (bridging) and S4/S5 (phosphate oligomers). Bond strength is dictated by the distribution of MDP coordination modes rather than total presence. A 10% concentration is the ideal threshold for maximizing strong S2 ionic bonding. Exceeding this limit promotes non-productive phosphate multilayers that compromise interface stability.

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Related topics: Dental materials and restorations · Polymer Nanocomposites and Properties · Chemical Synthesis and Characterization