| Background:The immediate and short-term bonding strengths of resin-dentin bonds have already reached a clinical satisfactory level.However,the durability of it hasn't.After its function for years,there used to be lots of defects on the resin-dentin bonding interface because of various factors such as saliva,enzyme,pressures,temperatures and so on.Therefore,the bonding strength decreased as a result.Recently,the proposal of dentin biomimetic remineralizaiton provided a potential approach to solve bonding durability problems.But requirement of long time greatly compromised its further clinical application.In previous research we have already established two amorphous calcium phosphate biomimetic remineralization systems,PAA-ACP remineralization system and Glu confirmed PAA-ACP remineralizaiton system by using amorphous calcium phosphate(ACP)and polyacrylic acid(PAA).both of them could reform intrafibrillar and extrafibrillar minerals in few days,whereas studies on the effect of resin-dentin bonding durability has not yet been performed.Objective:To evaluate the effects of remineralization by two amorphous calcium phosphate(ACP)systems on resin-dentin bonding durability by measuring and comparing the dentin microtensile bond strengths(?TBS).Methods:Two kinds of mineralizing fluid,Glu+ and Glu-,were made based on the previous studies.40 extracted third molars of human were chosen and the enamel were removed by using a water-cooled low-speed diamond saw.The samples were polished,etched by 35%phosphoric acid for 15seconds and washed by deionized water for 30 seconds.Then all the samples were randomly assigned to four groups and treated as follows:Group a:group as control,immediate resin bonding,Group b:pretreated by A(Glu+)for 2 days then bonded with resin,Group c:pretreated by A(Glu+)for 4 days then bonded with resin,Group d:pretreated by B(Glu-)for 15 days then bonded with resin.All the samples were bonded with resin by 3M Single Bond Plus and formed 4mm resin crowns,then numbered blindly and stored in deionized water for 24 hours.Each specimens was sectioned into 1mm2 beams and in each group beams were randomly devided into four subgroups,respectively are:(1)NaClO 0h,(2)NaClO 1h,(3)NaCIO 2h,(4)NaClO 3h.Then all these beams were performed with microtensile test and microtensile bond strengths(?TBS)were measured(MPa).The fractures were analyzed by S-4800 scanning electron microscope and the types of fractures were recorded as:(1)dissolution area,(2)adhesive area.Area percentage of each type were measured by S-4800 scanning electron microscopy software.Statistical analysis was computed with SPSS Statistics 20.0 using two-way ANOVA and SNK-q test(a=0.05).Result:1?Microtensile bond strength test showed that after 1,2 and 3 hours NaCIO storage,microtensile bond strengths of Glu+4d(27.980±8.522MPa,25.710±4.732MPa,18.333±7.365MPa)and Glu-15d(30.436±4.885MPa,24.598±8.692MPa,20.048±6.717MPa)were significantly higher than that of Glu+2d(13.623±8.064MPa,7.390±3.385MPa,6.030±2.069MPa)and control group(8.240±4.492MPa,4.319±3.021 MPa,4.189±2.063MPa)(P<0.05).There was no significant difference between Glu+4d and Glu-15d(P>0.05),so was Glu+2d and control group(P>0.05).2?In all these four groups,when stored without NaCIO,types of fracture observed were almost all adhesive area.However,when time of storage prolonged,the percentage of dissolution area increased as well.Group of control showed biggest percentage of dissolution area,Glu-15d showed slowest ones.3?The observation of scanning electron microscope revealed that treatment of both Glu-15d and Glu+4d could provide protection for naked demineralization dentin collagen fibers and increase the ability to resist degradation.Conclusion:The two-day pretreatment of PAA-ACP remineralization system with glutamic acid(Glu+2d)has no significantly enhancement of resin-dentin bonding durability.Both the fifteen-day pretreatment of PAA-ACP remineralization system without glutamic acid(Glu-15d)and the four-day pretreatment of PAA-ACP remineralization system with glutamic acid(Glu+4d)can protect naked dentin collagen fibers,as a result,the durability of resin-dentin bonds were significantly improved. |
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