Effects Of Er,Cr:YSGG Laser Irradiation On Shear Bond Strength Between Dentin And GICs

OBJECTIVEIn tooth preparation,adopting diverse preparative methods would generate different effects on bond of tooth surface.The evaluation of these effects uses mainly shear bond strength.At present,high speed rotary handpiece became the most prevalent clinical method in the tooth preparation.However it could bring many disadvantages in teeth surface observed under SEM,such as smooth surface,thick smear layer,without evidence prism and rarely opened dentinal tubules,which hinder restorative materials from adhesion and so on.In the most recent years,numbers of well-known native and foreign dentists have convincingly demonstrated that Er,Cr:YSGG lasers have the great ability to reducing the negative factors effectively,which caused from adoption of preparative methods on restorative materials.Furthermore,the shear bond strength between teeth and restorative materials are interrelated with restorative materials themselves.Glass ionomers is also known as glass ionomer cement(GIC).Comparing with composite resin,the characteristics of GICs are chemical cohesiveness with dentin,coefficient of thermal expansion is closer to tooth structure,preventing caries by releasing F^-,less side effects on dental plus and operated conveniently and even needless to prepare et al.The aim of this experiment is therefore analyse the effects of two preparetion methods on shear bond strength of three GICs combined with SEM,stereomicroscope and etc,which would be able to bring out a better result on the selection of tooth preparation method and glass ionomers filling material in order to provide theoretical evidence for clinical application.METHODSTo begin with collecting forty-five non-carious,intact,non-filled and extracted premolars and randomly dividing them into two groups,which were group A(thirty) and group B(fifteen).All samples from group A were processde by high-speed rotary handpiece below EDJ under the same condition and again randomly distributed into three separate groups tagged as group A₁,group A₂and group A₃,where each of them had ten samples.Thereafter all samples'buccal surface in the group A were cut off by Er,Cr:YSGG laser.The buccal and lingual sides of group A₁,group A₂and group A₃ were filled respectively with three GICs which was made with the size 3mm×3mm using plastic pipes.Likewise,The group B was also randomly split into three different groups labeled as group B₁,group B₂and group B₃.Preparing the same type size buccal and lingual cavities by Er,Cr:YSGG laser and bur separately,which were again restored with three GICs.All teeth were then thermocycle for 500 cycles.Finally,group A specimens were mounted on the test machine for shear bond strength examination, recording each specimen failure figure and then obversed the mode of failure under a stereomicroscope.ANOVA was used to analyse the failure figures.In addition to the group B,the interfaces between teeth surface and filling materials of allspecimens were observed by SEM.RESULTS1,Shear bond strengthThe data showed:The specimens in group A₃ had much higher bond strength than group A₂,and the specimens in group A₁ demonstrated lowest bond strength.Apart from group A₁,there were significant differences between other test groups and corresponding control groups(P＜0.05).2,StereomicroscopeThere were more remaining restorative materials in test group than corresponding control group.Group A₁:adhesive failure mainly happened between restorative materials and dentin with few material fragments.Group A₂:the mode of failure was similar with Group A₁ but with more material fragments.Group A₃:cohesive failure mainly happened in the bonding GIC with large material fragments. 3,SEMThe result of SEM analysis showed that the result of the test group were better than them in control group;group B₃ showeed best result than two other group and group B₁ showed most undesirable results.CONCLUSIONS1,Adopting Er,Cr:YSGG laser-cutting can enhance the shear bond strength of restorative materials.2,Er,Cr:YSGG laser can improve the effect on bonding between dentin and filling materials.3,The bond strength associated with Fujiâ…¨group are best,the bond strength of FX-â…¡group were the second and the bond strength obtainded with GIC-1 were the worst.