Study Of Teeth Root Microcracks And Surface Morphology After Root Canal Preparation With Different Kinds Of Nickel Titanium Instruments Horizontal To The Anatomic Apical

Objective: To study the root crack and apical surface morphology after root c-anal preparation with different types of nickel titanium instruments.Methods: 100f-reshly extracted tooth due to periodontal disease which were randomized to 5 groups were taken images by SEM to record the apical surface morphology.Then the y were prepared with Twist File Adaptive?ProTaper Next?WaveOne?ProTaper Un-iversal respectively under work length(horizontal to the anatomic apical foramen).After root prepared the apical surface morphology of each tooth was observed by SEM,then the apical foramen shift,dentin defects and crackle surrounding the apical foramen was recorded.The root tip samples of each group were cut with a precision low speed disk saw,and the incidence rate of root micro cracks and the di-stribution in different sections were compared.Results: The results of stereoscopic microscopy show: There was no significant difference between Twist File Adaptive group and Pro Taper Next group,group Twist File Adaptive root microcracks occurred was lower than that of ProTaper Universal group,the differrence was statistically significant;ProTaper Next group root microcracks occurred was lower than that of Pro Taper Universal group and WaveOne group,the difference was no statisti-cally significant;Pro Taper Universal group and WaveOne group was not statisticall-y significant.Scanning electron microscopy results show: There were statistically s-ignificant differences in nickel titanium instruments after root canal preparation,ap-ical for amen of offset surface around the crack probability(P<0.05),there was n-o statistically significant difference around the nickel titanium instruments after root canal preparation of apical cementum defect probability(P>0.05).The probability of ProTaper Universal was higher than that of WaveOne,and the difference was not statistically significant.The probability of ProTaper Universal was higher than th-at of Twist File Adaptive,and the differrence was statistically significant,and the difference of WaveOne and Twist File Adaptivewas not statistically significant.The probability of apical for amen of offset surface around the crack was less than W-ave One when the root canals were prepared by the Twist File Adaptive,The differ-rence was statistically significant(P<0.05).Conclusion: Root canal preparation is easy to cause teeth root cracks.Twist File Adaptive and WaveOne can reduce the ap-ical foramen shift compared to ProTaper Universalafter the preparation of root c-anal.The incidence of teeth root cracks after Twist File Adaptive root canal prepa-ration is the lowest with the greatest advantages.