The Effect Of Er:YAG Laser On Dentin Adhesion:in Vitro Study

Objective:To investigate the effects of Er: YAG laser pretreatment on deciduous and permanent dentin surface morphology,adhesive properties,changes in resin-dentin interface and composition,and to preliminarily explore the effect of Er: YAG laser treatment on dentin bonding properties.It can provide experimental basis for the clinical application of Er: YAG laser.Materials and methods:Er: YAG laser with different energies were used to pretreatment the dentin surface in vitro.The dentin morphology was observed by scanning electron microscope（SEM）and the diameter of dentinal tubules was analyzed;The micro-tensile bond strength of resin-dentin bonding was tested by using a universal testing machine;By using a confocal microscope（CLSM）to observe the resin-dentin bonding interface which was labeled with rhodamine B;The changes of Ca/P were calculated and analyzed by energy-dispersive X-ray spectroscopy（EDX）The organic and inorganic content of the dentin were investigated by Fourier Transforms Infrared spectroscopy（FTIR）.All the data were processed and analyzed statistically by using SPSS25 software.One-way analysis of variance（ANOVA）was used to analyze the data.Results:（1）After Er: YAG laser pretreatment,the dentin surface of deciduous and permanent teeth showed no smear layer and the dentin tubule was open.With the increase of laser energy,at 200 m J or higher energy for permanent teeth and 150 m J and higher energy for deciduous teeth,dentin surface fissure and dentin tubule deformation occurred.（2）Er: YAG laser pretreatment can increase the bonding strength of dentin of permanent and deciduous teeth.When Er: YAG laser energy reached at 150 m J,the bonding strength of permanent dentin reached（26.63 ± 2.92）MPa,which was significantly higher than that of self-etching group（20.41±3.83）MPa.The difference was statistically significant（P < 0.05）.When Er: YAG laser energy reached at 100 m J,the bonding strength of deciduous dentin reached（25.90 ± 1.94）MPa,which was significantly higher than that of self-etching group（20.14±3.11）MPa.The difference was statistically significant（P < 0.05）.（3）After Er: YAG laser pretreatment,the resin tags changed from sparse to dense and the length of the resin tags increased with the increase of laser energy.When the permanent teeth were treated with 150 m J Er: YAG laser and deciduous teeth were treated with 100 m J Er: YAG laser,the resin tags became the most dense.With the further increase of laser energy,the resin tags were short and sparse when 200 m J Er:YAG laser was applied to permanent dentin and 150 m J Er: YAG laser to deciduous teeth.（4）After Er: YAG laser pretreatment on deciduous and permanent dentin!the wave pattern of infrared spectrum was similar to that of natural dentin.There was no significant difference in Ca/P between the blank control group and Er: YAG laser group（P>0.05）.Conclusions:1.The pretreatment of using Er: YAG laser can remove the smear layer on dentin surface,open the dentinal tubles.2.With the increasing of Er: YAG laser energy,the resin-dentin micro-tensile bonding strength of deciduous and permanent dentin gradual increased and then decreased.The ideal bonding strength of deciduous and permanent dentin was obtained at 100 m J and 150 m J respectively.3.Er: YAG laser pretreatment of dentin promoted the penetration of adhesive,the length and density of resin tags increased.4.The wave pattern of infrared spectrum after Er: YAG laser treatment of deciduous and permanent dentin is similar to that of natural dentin,and there was no change in Ca/P.