The Comparative Study Of Different Adhesive To The Mild,Moderate And Severe Dental Fluorosis Bonding Strength

Objective The effects of two different adhesives on the bonding strength of mild,moderate and severe dental fluorosis enamel were studied by means of tensile and shear mechanical properties experiments.The microstructure of resin fracture bonding interface of dental fluorosis was observed by stereomicroscope,scanning electron microscope and laser scanning confocal microscope,and the adhesive properties were evaluated comprehensively.In order to investigate the adhesive effect of mild,moderate and severe dental enamel on different adhesives.It provides experimental basis for the selection of dental adhesives with different degrees of fluorosis in clinical work.Methods According to Dean's classification standard,60 premolars of mild,moderate and severe fluorosis teeth without caries in vitro were selected,and a total of 180 dental fluorosis were selected.Then the teeth with the same degree of fluorosis were randomly divided into two groups(all-etching bonding group and self-etching bonding group)with 30 teeth in each group.The isolated teeth were embedded in superanhydrite and exposed on the lip(cheek)side and tongue(palate)side of the crown above the enamel cementitious boundary.The enamel surface was evenly ground off 0.5mm with carborundum needle to ensure that the remaining surface was enamel.A 2mm long,wide 3mm cuboid hole is made with a perforator on one side of the tape,and the perforated tape is pasted on the polished enamel surface.Two kinds of adhesives(all-etching adhesive Prime & Bond NT,self-etching adhesive SE-Bond)were coated on the polished glaze according to the grouping condition,and the composite resin Z350 was cured under pressure,and finally 2 × 3 × 2mm resin block was formed.Then two kinds of adhesives(all-etching adhesive Prime & Bond NT,self-etching adhesive SE-Bond)were coated on the polished glaze for resin bonding,and the photocuring composite resin Z350 was cured under pressure,and finally 2 × 3 × 2mm resin block was formed.The prepared light,moderate and severe dental fluorosis specimens were stored in distilled water at 37 ? for 24 hours.The tensile strength and shear strength were measured on the universal material testing machine,and the ultrastructure of the fracture interface was observed by stereomicroscope,scanning electron microscope and laser scanning confocal microscope.Results(1)The tensile strength and shear strength of mild dental fluorosis enamel were significantly different from those of Prime & Bond NT)system(P?0.05),and the tensile strength and shear strength of mild fluorosis enamel were significantly higher than those of control group,there was no significant difference in tensile strength and shear strength between moderate and severe dental fluorosis(P > 0.05).(2)There was no significant difference in tensile strength and shear strength of mild,moderate and severe fluorosis teeth by self-etching bonding system(SE-Bond)(P > 0.05).(3)The results of scanning electron microscope: The enamel crystals of mild fluorosis were arranged relatively dense,and a small amount of resin residue could be seen.The arrangement of enamel crystals in moderate fluorosis was loose and the gap was widened.The arrangement of enamel crystals in severe fluorosis was irregular and the disorder was aggravated,and the dentin tubules exposed after partial enamel exfoliation could be seen.(4)The results of laser scanning confocal microscope: with the aggravation of the degree of dental fluorosis,the arrangement of enamel crystals in dental fluorosis was looser.The bonding interface after total etching is rougher than that of self-etching,and the bonding interface is more uneven.Conclusions 1.The bonding strength of mild fluorosis enamel to all-etching bonding system is different from that of self-etching bonding system,and the bonding effect of mild fluorosis enamel to all-etching bonding system(Prime & Bond NT)is better than that of self-etching bonding system(SE-Bond).However,there was no significant difference in bonding strength between moderate and severe fluorosis enamel to all-etching bonding system and self-etching bonding system.2.The bonding strength of Prime & Bond NT)to mild fluorosis enamel was the highest,but the tensile strength and shear strength of self-etching bonding system(SE-Bond)to mild,moderate and severe fluorosis enamel were not significantly different.That is to say,there is no difference in the bonding strength of self-etching bonding system to different degrees of dental fluorosis.