Application Of Er,Cr:YSGG Laser And Etching Technology In The Treatment Of Wedge-shaped Defect

Objective In this study,the effects of Er,Cr:YSGG laser treatment and modern acid etching technology on improving the adhesion of composite resin were investigated.Material and methods A total of 120 detached third molars were selected to be prepared in the form of wedge-shaped defects in the neck,and the coronal surface was taken.Gradient polishing by water sandpaper to 600 mesh;Will put in ultrasonic cleaning machine,specimen temperature 20 ?,continuous turbulence 120 min,remove the specimen in 0.9% saline,waiting to be processed;20 specimens in each group were randomly divided into G1,self-etching group;G2,total-etching group;G3,Er,Cr:YSGG laser group;G4,Er,Cr:YSGG laser + self-etching group;Group G5,Er,Cr:YSGG laser + total-etching group;G6,total-etching +Er,Cr:YSGG laser group;The molds with the fixed tooth surface diameter of 3 mm and height of 4 mm shall be filled with composite resin and cured by light in strict accordance with the manufacturer's instructions.At the set temperature,after 5,000 cycles by the cold and hot cycle machine,the universal mechanical testing machine tested its shear bond strengh(SBS).Scanning electron microscopy(SEM)was used to observe the morphological changes of teeth with different treated methods.The fracture state was observed by stereoscopic microscope.Univariate anova was used for statistics,andSNK test was used for comparison between groups.P<0.05 showed statistical difference.Results Adopting the processing mode of single factor variance analysis of the six groups,the difference between SBS value,G6(14.61 Mpa)> G5 group(14.52 Mpa)>G4(11.04 Mpa)> G2(8.57 Mpa)> G1(7.83 Mpa)> G3(5.17 Mpa),including the G5 group and G6,G1 and G2 group mean no significant difference,there was no statistically significant difference,and the rest were statistically significant difference between the groups.The fracture surface was observed under stereoscopic microscope in three states: viscous interface failure,cohesion failure and mixed failure.SEM showed that the scratches left after polishing could be observed on the untreated tooth surface,and the stain layer around the scratches was thick and dense.After 35 %phosphoric acid etching,the dentine tubules were found to be in an open state,with smooth tubule wall and loose stain layer on the surface.After 1.5 W and 20 Hz water laser treatment,the shape of dentin tubules was indistinctly visible,showing a blocked state,and the tubules were not open.Cracks in the enamel dentin boundary(EDJ)could be observed,but the shape of enamel dentin was not obvious.In the treatment group treated with 35 % phosphoric acid first and then treated with water laser,the dentine tubules were obviously open,the tubule wall formed a rugged and irregular collagen fiber network,and obvious stain layer could be seen around the tubules.The open state and inner wall state of dentine tubules were similar in the water laser treatment group and the water laser treatment group.In the two latter treatments,the enamel state was similar to that in the 35 % phosphoric acid treatment group.The enamel boundary was protruded towards the dentin,and the glaze column was arranged in fish-scale shape.In the Er,Cr:YSGG laser treatment group,the glaze column shape was not obvious.Conclusion Er,Cr:YSGG laser is simple,safe and minimally invasive,which can effectively remove the contaminated layer and alleviate the pain of patients.1.5 W,20 Hz Er,Cr:YSGG laser can be combined with acid-washing or self-acid-etching for the coronal surface treatment of wedge-shaped defects,which can improve the bonding performance of the interface.However,the clinical efficacy and durability of the root-to-surface adhesion of wedge-shaped defects still need to be further studied.