| Objective: By comparing the effects of ultrasound and different power diode lasers on the microhardness and morphology of root canal isthmus dentin,a more advantageous method is sought to assist in cleaning the root canal isthmus,in order to improve the success rate of treatment of pulpal and periapical diseases in complex root canal systems provides a theoretical reference.Methods: 50 maxillary premolars with root canal isthmus were selected by cone beam computer tomography(CBCT).Crown removal,conventional pulp extraction,and K file dredging were performed successively.After that,the canal preparation was completed by using the Wave One Gold machine and the niti file.They were randomly divided into group A,B,C,D,and E correspond to control group,ultrasound group,laser 1.0w group,laser 2.0w group and laser 0.5w group respectively.The following two experiments were carried out respectively.(1)Microhardness experiment: group B was subjected to ultrasonic washing,groups C,D and E were treated with different power diode lasers,and group A was used as a control.The samples were dotted and tested for microhardness,and the obtained data were statistically analyzed using SPSS 23.0 software to compare the effects of ultrasonic washing and different power diode laser on microhardness of dentin in root canal isthmus.(2)Morphological experiment: group B was subjected to ultrasonic washing,groups C,D and E were processed with different power diode lasers,and group A was used as the control.Theroot canal isthmus was scanned by scanning electron microscopy for the upper,middle and lower segments.Their scores of the smear layer of the image was obtained,and statistical analysis of SPSS 23.0 software was performed to compare the effect of ultrasonic washing and different power diode laser to remove the dentin smear layer of the root canal isthmus.Results: ? Hardness experiment:(1)There was no statistically significant difference between group B and group C compared with group A(P>0.05);(2)There was statistically significant difference between group D and E compared with group B(P<0.05),the microhardness of root canal isthmus dentin in the group of laser 1.0 W and 2.0 W were higher than that in ultrasound group;(3)There was statistically significant difference between group D and E compared with group C(P<0.05),the microhardness of root canal isthmus dentin in the group of laser 1.0 W and 2.0 W were higher than 0.5 W;(4)There was no statistically significant difference between group D and group E(P>0.05).? Topography experiment: a.In he same treatment method,the overall comparison between the scores of different levels of root canal isthmus in each group was not statistically significant(P>0.05).So,there was no difference in removal of the smear layer in the upper,middle and lower sections of each root canal isthmus.b.In different treatment methods,the comparison results of the overall score of the root canal isthmus between each group as follows:(1)There was statistically significant difference between group B,C,D,and E compared with group A(P<0.05).The four experimental groups were better than the control group in removing the smear layer of root canal isthmus;(2)There was statistically significant difference between group D and E compared with group B(P<0.05).So,the group of laser 1.0 W and 2.0 W were better than the ultrasound group in removing the smear layer of root canal isthmus;(3)There was statistically significant difference between group D and E compared with group C(P<0.05).So,the group of laser 1.0 W and 2.0 W were better than 0.5 W in removing the smear layer of root canal isthmus;(4)There was no statistically significant difference between group D and group E(P>0.05).Conclusion: 1.Ultrasonic washing and 0.5 W diode laser irradiation have no significant effect on the microhardness of root canal isthmus dentin,while the 1.0 W and 2.0W diode laser irradiation can significantly enhance the microhardness of isthmus dentin.2.Ultrasonic washing and irradiation different power(0.5 W,1.0 W,2.0 W)diode lasers can effectively remove the root canal isthmus smear layer.The 1.0 W and 2.0 W diode lasers are better than ultrasonic washing in removing the isthmus smear layer.During this experiment,the ability of ultrasonic washing and 0.5W diode laser irradiation to remove the isthmus smear layer has a considerable effect. |
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