In Vitro Study Of The Effects Of Different Dentin Cleaning Agents On The Bond Strength Of Three Cements To Dentin

Objective：To assess whether two different dentin surface cleaning agents influenced thebond performance of three different cements to dentin to help the dentists to choosethe suitable dentin surface cleaning agents and cements when dentin wascontaminated after the tooth was prepared in clinic.Methods:Eighty-four intact,caries-free, extracted human premolars of the StomatologicalHospital Affiliated to Nanchang University between July1,2012-August1were usedin this study. Teeth were stored in distilled water containing1%chloramine T at-20℃, and used within three weeks following extraction.The buccal enamel of thecrown of all the specimens was grinded with the high speed cutting disc under waterspray in order to form90dentin blocks with the size of4×4×2mm3. The surroundingand buccal surfaces of the premolars were ground flat with silicon carbide(SiC)metallographic papers(320-grit、400-grit、600-grit) under running water in order toobtain flat dentin surface.(Whether the buccal enamel was grinded completely wasexamined with stereoscopic microscope at2.5×12.5magnification.)The dentin blockswere made out of standard test specimens with the size of14×14×4mm3using specialmould.All dentin blocks were randomly divided into three groups(24for each group)according to different surface treatments: group A: Scrub with cotton ball which wassoaked in distilled water for60s;group B: Scrub with3%EDTA for60s and washwith distilled water for20s;group C: Scrub with1%NaOCl for15s and wash withdistilled water for20s.Every group is subdivided into three groups according todifferent cements:A1,Bland C1groups are bonded with glass ionomer cement(KetacTMCem Easyrmix);A2,B2and C2groups are bonded with resin-modifiedglass-ionomer cement(RelyXTMLuting2);A3,B3and C3groups are bonded withself-adhesive resin cements (RelyXTMUnicem).There are a total of9groups, eachgroup has8specimens.All the dentin blocks of each group were used for shear bondstrength test. The double sticky tape with a central hole2.8mm in diameter was pasted on the surface of buccal dentin in order to define the bonding area. Then thecopper ring with3.8mm in internal diameter and2.0mm in height was fixed on thesticky tape. The three cements were injected into the copper ring according to theirinstructions as high as the summit of the copper ring.After30minutes,all thespecimens were stored in distilled water at37℃for24hours.The SBS test wasperformed using a universal testing machine at a crosshead speed of0.5mm/min andmaximum failure load was recorded, and the SBS was calculated. The SBS valueswere analyzed by2-way ANOVA by using the statistical software SPSS17.0andmultiple comparisons tests were done by the Least-significant difference(LSD) test atα=0.05.A single observer observed the fractured specimen interface usingstereoscopic microscope at45×magnification. in order to evaluate failure mode;9specimens which were treated with different surface conditioning protocols wereobserved by SEM at5000×magnification；9specimens were made additional andobserved the longitudinal section bonding interface morphology by SEM.Results:1.In a two-factor variance analysis of all the data,the main effect of the differentfactors about "different surface treatment" and "different cement" were statisticallysignificant(P<0.05),the two factors had significantly influence on shear strength andthey had interaction(P<0.05)2.In subsequent separate one-factor variance analysis and LSD test for differentcements,significant differences between different cements were found(P＜0.05),andA3、B3、C3groups>A2、B2、C2groups>A1、Bl、C1groups for three cements with EDTAand NaOCl surface treatment(P＜0.05).In one-factor ANOVA models and LSD testfor different surface treatments,significant differences between different cementswere found(P＜0.05),and B group>A group,C group in the GIC and RMGIC(P＜0.05)and there were no statistically significant differences between A group and Cgroup(P>0.05);but C group>A group,B group in the RelyXTMUnicem and there wereno statistically differences between A group and B group(P>0.05).3.The specimens bonded to the dentin with glass ionomer(A1group and C1group) were mainly adhesive failure pattern at the cement-dentin interface, B1grouphad half an adhesive failure pattern and the other half were mixed failure pattern, there were no statistical differences between A1group and C1group(P>0.05),but thedifferences between B1group and the other two groups had statistical significance(P<0.05);B2group were mainly mixed failure pattern and the other wo groups wereboth adhesive failure pattern and mixed failure pattern, there were no statisticallydifferences between A2group and C2group(P>0.05),but the differences between B2group and the other two groups had statistical significance (P<0.05); A3group and B3group were mainly mixed failure pattern,C3were all cohesive failure patternhappened in the cements,there were no statistically differences between A3group andC3group(P>0.05),but the differences between B3group and the other two groups hadstatistical significance (P<0.05)。Conclusions:1.The Shear Bond Strengths between the self-adhesive resin cement and dentinwith three different surface treatments were significantly higher than those of glassionomer cement,and resin-modified glass ionomer cement,and glass ionomer cementproduced the lowest SBS to dentin.2.Glass ionomer cement and resin-modified glass ionomer cement increased theSBS to dentin treated with3%EDTA,but it had no effect to the SBS of theself-adhesive resin cement to dentin.3.Self-adhesive resin cement increased the SBS to dentin treated with1%NaOCl,but it had no effect to the SBS of the glass ionomer cement andresin-modified glass ionomer cement to dentin.4.The specimens bonded to the dentin with GIC groups were mainly adhesivefailure pattern at the cement-dentin interface and RMGIC groups were mainly mixedfailure pattern.The failure modes of self-adhesive resin cement groups were bothcohesive failure pattern and mixed failure pattern happened in the cements.