Polymerization Characteristic Of Self-adhesive Resin Cements Under Different Cure Mode

Now,resin luting cements were so worldly used in clinic,because of the remarkable mechanical,physical and bonding properties,the excellent esthetic effects and so on.Traditional resin cement consisted of total-etching resin cement and self-etching resin cement.Adhesive was necessary for both of them,which is not only complex but also technology-sensitive.Self-adhesive resin cement is a new kind of adhesive material.Using new technology,there was on need of matching adhesive,which made processing simple and time-saving.It combined etching agent,primer,bonding agent and resin cement paste into one.Self-adhesive resin cement just needed one-step bonding process,which greatly reduce the steps and the technology-sensitive.The self-adhesive resin cements also adopt the dual-cured mode as many conventional resin cements,to ensure sufficient polymerization in positions far from the curing light such as the shade of ceramic restoration thickness,root canal,and so on.However,different from the conventional resin cements,the self-adhesive resin cements have two different curing mechanisms simultaneously during their curing process.It not only included the free radical methacrylate polymerization initiated by photo initiators and acidic initiating redox systems,but also included the acid-base reactions which could form the ionic crosslinks between acidic groups of acid functionalized monomers and ions of the acid-soluble glass fillers or the mineralized tooth tissue.The curing process of self-adhesive resin cement is more complex than traditional resin cement.Sufficient polymerization under different cure mode is very important.[Objective]This study was aiming to investigate the polymerization characteristic of self-adhesive resin cements under dual and chemical cure mode.[Methods]The light-proof silicon rubber cuboid mold with one end open were syringed and filled by a dual-cured flowable core build-up resin composite,a dual-cured composite luting cement and 6 dual-cured self-adhesive resin cements,then the open end of mold was irradiated directly by a light unit at 800mW/cm2×20s.And all specimens were stored in the light-proof box.After irradiation 1h 24h and 120h Knoop microhardness was measured along the vertical surfaces of specimens from 1mm to 10mm depth at 1mm intervals.Data were analyzed by One-way ANOVA.[Results]Before the Knoop hardness numbers of the 8 materials became stable,they decreased gradually in depth at each time point(P<0.05).However,the depths at which they became stable differed.The Knoop hardness numbers of Maxcem Elite reached stability at a depth of 2 mm,G-Cem Automix and Multilink Speed at 3 mm,Duo-link,MultiCore Flow,RelyX Unicem 2 and PermaCem 2.0 at 4mm,and BisCem at 5 mm.Microhardness increment of Duo-link and MultiCore Flow was high within the first 1h after cure start.The microhardness increased gradually during 1-24h and attained to the maximum after 24h.The increment of microhardness variation from 1h to 120h in 1mm was higher than that in 5mm.Unlike Duo-link and MultiCore Flow,the microhardness of G-Cem Automix and BisCem continued to increase after 24h.The increment of microhardness variation from 1h to 120h in 1mm was lower than that in 5mm for Multilink Speed,PermaCem 2.0 and BisCem,and was the same as 5mm for RelyX Unicem 2,Maxcem Elite and G-Cem Automix.[Conclusions]Self-adhesive resin cements had different polymerization characteristic.