Methods: Hexane-diol dimethacrylate (HDDMA) or polyethyleneglycol dimethacrylate (PEGDMA, Mn=400) were combined with 20 or 50 mol% methacrylic acid (MAA). 2-dimethoxy-2-phenyl acetophenone (DMPA, 0.1wt%) as added to mixtures of the neat monomers as the photoinitiator. Pre-polymerized oligomers (PEGDMA/MAA/methyl methacrylate, 30/20/50 mol%, respectively) were synthesized in solution (THF, room temperature). Materials were polymerized in situ (neat) or dry-cast (oligomers) onto the surface of 15 mm diameter CpTi wafers (n=12) , previously cleaned with 1N nitric acid. Three specimens were stored in distilled water (25⁰C) and the time to passive coating detachment was recorded. Nine specimens were attached to the Watanabe jig with resin composite (Z250, 3M-ESPE) for shear bond-strength testing (SBS), at 1 mm/min. Results were analyzed with one-way ANOVA/Tukey’s test (α=5%).
Results: Coatings containing HDDMA, regardless of the MAA concentration, stayed attached to the CpTi disks for over 30 days, likely due to the hydrophobic character of that monomer. Coatings based on PEGDMA detached in less than 24h. SBS (in MPa) was higher for PEGDMA-based coatings (8.49±2.61) compared to HDDMA-based coatings (7.92±0.84) and the dry-cast polymer coating (6.73±1.37), which were all statistically similar to each other. Those values are comparable to shear stresses registered during loading of fully integrated implants, in the range of 1-8 MPa (Alvarez, 2010).
Conclusion: The materials proposed presented sufficient bond strength with titanium to withstand mechanical loadings typically applied to dental implants. Survival of the coating is crucial to its role as a cell signaling molecule depository.