The Effect Of Chemical Interaction Between Phosphate Monomer And Silane On The Bond Performance Of Lithium Disilicate Ceramics

ObjectivesLithium disilicate ceramics are widely used in clinic due to its superior aesthetic properties,but the bond performance affects its service life.As a kind of glass ceramics,the traditional bonding method is hydrofluoric acid etching to obtain the roughened surface,combined with the use of silane coupling agent to form a chemical combination,making silane become a vital part of the bonding process.However,with the invention of multi-purpose adhesive products,adding a variety of functional monomers contain silane or not,simplifying the operation and reducing the technical sensitivity,but it is still controversial whether additional application of silane is needed when multi-purpose products used.It is not clear that whether there is mutual antagonism or promotion of multiple functional monomers in the multi-purpose adhesive products,and whether it has an effect on the bonding effect.In this study,we systematically evaluated the effect of chemical interaction between phosphate monomer and silane on the adhesion of lithium disilicate ceramics.MethodsThe molecular models of silica,γ-methacryloxypropyltrimethoxysilane(γ-MPS)and 10-methacryloyloxydecyl dihydrogen phosphate(10-MDP)were constructed by quantum chemical method.The reaction between silica and silane,between silane and 10-MDP and the dehydration self-condensation of silane were calculated by thermodynamics.Bondind specimens were built with two kinds of universal adhesives(Su and AU),two kinds of self-adhesive resin cements(CSL and RXU),and one kind of traditional resin cements(Ctr),with half of them received pre-silanization.Half of the bonding specimens were stored for 24 hours in distilled water at 37℃ and the other were subjected to 20,000 thermocycles plus 90 days water storage,then shear bond strength(SBS)was tested.Lithium disilicate powder treated by silane,two kinds of universal adhesives that contained silane or not was analyzed by X-ray photoelectron spectroscopy(XPS)and Fourier transform infrared spectroscopy(FTIR).ResultsThe results of thermodynamic calculation show that siloxane is formed between silica and silane,but the self-condensation of γ-MPS and the reaction of γ-MPS and 10-MDP consume siloxane in acid environment.SBS results showed that there was no significant difference between the group of silane applied alone and the universal adhesives and self-adhesive resin cements.Pre-silanization could improve the bonding effect of universal adhesives or self-adhesive resin cements and lithium disilicate,but aging reduced the bonding strength of most groups.XPS and FTIR support the chemical reaction between silica and silane or two kinds of universal adhesives to form silica bond.Conclusions1.Bonding improvement of silane to lithium disilicate is due to the formation of a Si-O-Sibond between silane and silica,which is limited by p H values;2.Silane can self-dehydrate and self-condense or condense with 10-MDP in acid environment,which may decrease the bond effect,but pre-silanization is not affected by this chemical reaction;3.The universal adhesives or self-adhesive resin cements can at least provide the same bond effectiveness between lithium disilicate and resin as the application of silane alone,which is based on the effect of silane incorporated;the pre-silanization treatment can further improve the bond effect of universal adhesives or self-adhesive resin cements.