Dentin Bond Strength:Influence Of Er:YAG Laser

Objective:Laser develops rapidly as a brand-new remedy in the past decades in stomatology.Boasting for its decreased pain,decreased vibration,lower noise and other assistance in cutting dental hard tissue,the Er:YAG laser was first applied to tooth ablation.Now it has been proved the Er:YAG laser irradiation leads to a microscopically rough substrate surface with dentinal tubules neatly open without smear layers covering on them.However,there is no concordant conclusion until now on whether the obtained surface,which is similar to the acid-etched one,is prone to dentin bonding.The aim of this study was to probe into the effect of Er:YAG laser on dentinal micromorphology and the dentin-resin bonding property.Methods:Forty extracted human premolars or molars were randomly divided into 6 groups:control group;acid-etching+SB2;Er:YAG laser+SB2;Er:YAG laser+acid-etching+SB2;Er:YAG laser+Easy One;Er:YAG laser+OptiBond Versa.Two teeth selected randomly from each group were cut into 3 mm dentin slices,then observed using SEM after treatment.The remaining teeth were prepared into unified dentin surface,treated differently according to their groups,then combined with resin to test their shear bond strength.Results:Consisting of two parts,the study discussed shear bond strength and surface morphology.Part one contained control group,acid-etching+SB2,Er:YAG laser+SB2,Er:YAG laser+acid-etching+SB2.SEM in this part reflected apparent morphological change in dentin after treatment.Results of statistical analysis mirrored the acid-etching+SB2 group had the highest shear bond strength?16.03±6.56MPa?,followed by Er:YAG laser+acid-etching+SB2?13.21±6.08MPa?,yet with no significant difference between them?P>0.05?.Control group had the lowest shear bond strength?4.52±1.02MPa?and there was no significant difference compared with Er:YAG laser+SB2?7.91±4.56MPa??P>0.05?,while there was a significant difference between control group and the rest ones?P<0.05?.SEM in part two illustrated the variance of surface morpholo gy in each group.On the basis of statistical analysis,the shear bond strength in the order from high to low was Er:YAG laser+acid-etching+SB2?13.21±6.08MPa?>Er:YAG laser+OptiBond Versa(10.93±3₅MPa>Er:YAG laser+Easy One?9.45±4.09MPa?>Er:YAG laser+SB2?7.91±4.46MPa?.There was a significant difference between Er:YAG laser+acid-etching+SB2 and the other three groups?P<0.05?,but there was no such difference among the other three groups?P>0.05?.Conclusion:1?Compared with using Er:YAG laser irradiation alone,acid etching after laser irradiation can enhance the shear bond strength between dentin and resin.2?35%phosphoric acid harvests the best bonding effect when dentin was pretreated by Er:YAG laser.