The Study On Shear Bond Strength Of Different Bonding Systems For Veneer Restoration In Fluorosed Teeth

Objective: In this study,IPS e.max CAD blocks were bonded to normal and fluorosed teeth with three veneer bonding systems.The adhesive property is then compared among groups with different teeth and bonding systems pairs.Specifically,the adhesive property is evaluated by shear bond strength and fracture mode.In order to find the preferable bonding stystem for veneer restoration in fluorosed teeth,we evaluated the effects of different bonding systems on the adhesion properties of fluorosed teeth.Methods: 24 normal teeth and 24 moderately fluorosed teeth were selected,using the standard diamond bur with 0.6-0.7mm of labial enamel surface removed.Each group was then polished with #600,#800,#1000 silicon carbide abrasive paper under water.Each tooth was embedded in self-curing resin block,while the coronal part was visible from the cementoenamel junction.48 IPS e.max CAD slices were chosen and randomly divided into6 groups.Group A,B,C were bonded to normal teeth,while group D,E,F were bonded to fluorosed teeth.Each group had 8 specimens.Group A and D were bonded to IPS e.max CAD slices with 3M Rely X Veneer bonding system.Group B and E were bonded to IPS e.max CAD slices with Bi SCO CHOICE 2 bonding system.Group C and F were bonded to IPS e.max CAD slices with Variolink N bonding system.After cementation,the specimens were stored in distilled water for 24 hours in an incubator at 37℃ before being treated with5000 hot and cold cycles.Each specimen was tested individually by the MTS ceramic test system.The specimen was fractured under tension at a crosshead of 0.5mm/min and the maximum load at fracture was recorded.The stereoscopic microscope was used to examine the fracture interface and classify the type of fracture mode.The data of shear bond strength of different bonding systems to normal teeth and fluorosed teeth respectively was analyzed by one-way ANOVA,whereas the data of shear bond strength of the common bonding systems were analyzed by the Independent-Sample Test.Results:1.The shear bond strengths of the normal teeth and moderately fluorosed teeth treated with the same bonding system were not statistically significant different(P>0.05).2.In groups of normal teeth and moderately fluorosed teeth bonding to IPS e.max CAD blocks,the shear bond strengths of Bi SCO CHOICE 2 bonding system and Variolink N bonding system were higher than that of the 3M Rely X Veneer bonding system.The difference was statistically significant(P<0.05).3.The fracture mode of adhesive failure was observed in the groups of 3M Rely X Veneer bonding system,whereas the fracture mode of cohesive failure within the cement was mostly observed in the groups of Bi SCO CHOICE 2 bonding system and Variolink N bonding system.Conclusion:1.For the normal and the moderately fluorosed teeth bonding to IPS e.max CAD blocks,the shear bond strengths of the three kinds of bonding systems were not statistically significant different.2.For the normal teeth and the moderately fluorosed teeth bonding to IPS e.max CAD blocks,the Bi SCO CHOICE 2 bonding system and the Variolink N bonding system could achieve preferable bonding effectiveness and meet the clinical need.