Experimental Study Of The Effect Of Er:YAG For Caries Removal

Object:The most traditional treatment of dental caries is mechanical removal with high-speed dental hand piece.However,common dental instruments and methods used often result in cutting extra healthy dental hard tissue,dentin hypersensitivity and even pain.With the concept of minimally invasive and comfortable treatment gradually gaining popularity,we advocate to maximize the preservation of healthy tooth tissue,minimize or eliminate the pain or discomfort to the patient during the treatment process,especially for children.The treatment process not only helps its oral therapeutic effect,but also contributes to the development of its physical and mental health.Therefore,as a representative of minimally invasive treatment Er:YAG laser debridement method came into being.Er:YAG laser can remove the smear layer to a greater extent,improve the bond strength and reduce micro-leakage and the secondary caries.In this experiment,Micro-tensile test,micro-leakage test,HE staining and scanning electron microscopy were used to analyze the effect of caries removal and filling between Er:YAG laser method and traditional mechanical method.Methods:36 extracted molars with large area of caries deep to dentin were collected.Every sample was evenly divided into two halves before caries removal by traditional mechanical method and Er:YAG laser method.We do the following experiments:(1)Micro-tensile test(n = 13).The caries were removed and filled before samples made into dumbbell-shaped slices with a resin-dentin surface of 1 mm 2.The tensile force at break was measured using a micro-tensile dynamometer.Calculating the micro tensile strength and doing statistical analysis.(2)Micro-leakage test(n = 13).After completion of caries removal,the cavities filled with resin and then performed thermal cycling test,measured the depth of micro-leakage after fuchsin staining.(3)HE staining experiment(n = 6).After dental caries removal,the roots were cut and consecutive decalcified slices(4μm)were sectioned through the cavities.Then we examine the presence of infected dentine tubules under the microscope after the staining,the remaining dentin tubules.Comparing the difference of two groups.(4)SEM experiment(n=4).The teeth were dissected and were caries removed in two methods.The structure of the dentinal tubules and the status of the smear layer were observed under scanning electron microscope.(5)Time experiment(n=36).recorded all above experiments’ caries removal time and Compared.Results:(1)There was significant difference in the micro-tensile strength between the two groups(P=0.031<0.05).(2)Micro-leakage depth of Er:YAG laser group is smaller than that of traditional mechanical group,but there was no significant difference between the two groups in micro-leakage(P=0.059>0.05).(3)There was significant difference in the remaining infected dentin tubules between the two groups(P=0.000<0.05).(4)SEM results of the Er:YAG laser group and the traditional mechanical group showed that the dentinal tubules with clear structure and no smear layer was observed in the laser group.However,the dentin tubules in the conventional mechanical group were blocked and the smear layer was obvious.(5)The time of Er:YAG laser group caries removal is longer than the traditional mechanical group.Conclusion:The Er:YAG laser used in caries removal has the advantages in micro-tensile strength,micro-leakage or anti-bactericidal,and remove the smear layer that are superior to the traditional mechanical methods.Therefore,Er:YAG laser is an alternative clinical treatment of caries removal.