Preparation Of Light-curable Polyurethane Adhesive And Its Effect On Properties Of Commercial Dentin Adhesive

Objective:At present,commercial dentin adhesives contain a large amount of hydrophilic resin monomer components,which is one of the reasons for the degradation of the dentin adhesive bonding interface.Improving the hydrolysis resistance of dentin adhesive is an effective way to improve the durability of the bonding interface.Polyurethane(PU),as a chemical polymer material with good biological safety,moisture resistance and mechanical properties,is widely used in the medical field.Medical products prepared from it include artificial hearts,vascular assist devices,wound dressings and ophthalmic devices.In this study,light-curable PU adhesives were prepared and tested for changes in the the water absorption values,water solubility values,degrees of conversion and micro-shear bond strength of the adhesive after adding it to three existing commercial dentin adhesives.Comprehensively evaluate the effect of PU adhesives on properties of dentin adhesives,with a view to providing experimental basis and new ideas for the development of new hydrolysis-resistant adhesives.Methods:1.The solution polymerization was used to prepare PU prepolymers with polyether triol,isoflurone diisocyanate and 2-hydroxyethyl methacrylate as the main raw materials.Fourier transfor infrared spectroscopy(FTIR)was used to characterize the chemical structure of the final synthesized product.Then PU prepolymers was mixed with a diluent,a solvent and a photoinitiator to be configured as a photocurable PU adhesive.2.Three commercial dentin adhesives were selected in the experiment.Single Bond Universal(SBU),Single Bond2(SB2),and Clearfil SE(SE)were used as the commercial adhesive group.The experimental group with 70% PU mixed adhesives was: SBU-70%PU,SB2-70%PU and SE-70%PU.Water absorption / solubility test pieces were prepared according to the method described in YY 1042-2011,and the water absorption values and water solubility values of each adhesive group were measured.3.FTIR method was used to characterize the structure of the polyether PU adhesive and determine degrees of conversion of each group of adhesives.4.Molars were prepared in vitro to prepare test specimens for adhesion.Universal testing machine detected the micro-shear bond strength of each group of adhesives.5.The experimental results were statistically analyzed using SPSS 19.0 software.The water absorption values,water solubility values,degrees of conversion and micro-shear bond strength of each group of adhesives were in accordance with the normal distribution.Comparisons between the two groups were performed using independent sample t tests.The difference was statistically significant with P <0.05.Results:1.The characteristic absorption peak(C = C double bond)of the photocuring group appeared in the FTIR spectrum,which was consistent with the structure of the expected product.2.The water absorption value of each experimental group was lower than the corresponding commercial adhesive group(P<0.05);the solubility values of SBU-70%PU and SB2-70%PU were lower than the corresponding commercial adhesive group(P <0.05).3.The degrees of conversion of the experimental group was higher than that of the corresponding commercial adhesive group(P <0.05).4.The micro-shear bond strength of SB2-70% PU was significantly higher than the corresponding commercial adhesive group(P <0.05).Conclusion:The introduction of 70% of light-curable PU adhesives into existing commercial dentin adhesives can significantly reduce the water absorption values and water solubility values of the corresponding commercial dentin adhesives and increase the degrees of conversion.At the same time,it has no effect on the micro-shear bond strength,which can effectively improve the overall properties of dentin adhesives.