| Root canal therapy(RCT) is an efficient method of treating pulposis and periapical disease. Root canal preparation is the most important step in RCT and it is the precondition and foundation of root canal disinfection and filling.Working length mentioned in RCT means the distance from the reference point on the crown to the apical stop and accurate working length is helpful to remove infected mass inside root canals effectively and protect apical constriction from being ruined by canal preparing instruments which are beyond root foramens.Accurate working length plays an important role in canal cleaning and shaping which induce successful endodontic treatments.At present,there are many methods to determine the working length such as tactile perception,radiographic method and electronic apex locator method.As X-ray film shows two-dimensional images of objects and the dentino-cemental junction is determined by the apical plane in radiographic method,it is hard to determine apical constriction with a vague X-ray film.In recent years digital X-ray imaging technique makes root images more distinct and after clinical trials, better accuracy of working length is obtained by radiographic method with digital X-ray imaging technique.Nowadays electronic apex locator method is most commonly used to determin the working length in the root canal therapy. After half a century's development, the accuracy obtained by electronic apex locators of the third and fourth generation is better than that obtained by electronic apex locators of the first generation.The advantages of electronic apex locator are as bellow: accurate, simple, convenient and less X-ray radiation to patients. Although the electronic apex locator presents the working length with high accuracy, the result would be affected by several factors. The hot spot of current studies is about the influence of the root canal apical foramen diameter and the solution quality inside the canal on the measuring accuracy and it is concluded that the residual pulp and strong electrolyte solution inside root canals can affect the measuring results and the measuring accuracy decreases when the apical foramen is larger than 0.4㎜ in many reaserches. Electronic apex locators with different working principles and apical foramens of different diameters are key factors in testing working length.The objective of this study is to discuss the selection of files when measuring the working length of root canals prepared regularly and compare the accuracy of 4 electronic apex locator species commonly used in clinic.40 isolated teech are selected as subjects of this study after being screened.Each of the teeth has only one straight cannal.After the pretreatment of the teeth, model was established with teeth and phosphate buffer agar gel,and then put initial file into cannal to conduct digital imaging and gain working length.In order to make sure the value,we conduct digital imaging again,until the tip of the file locate at the apical narrow region,the length of the file in cannal equals to the standard value of working length.Then enlarge the cannal with Mtwo nickel-titanium file from 10# untile 30# and measure the working length with 8#-30# K files and 4 kinds of electronic apex locator.Analyze the results statistically to evaluate the differences between the measurement and the standard value.Finally results are found as follows:1.Group Root ZX:The mean value between the standard and 8#,10#,15# K file measurements differs significantly whileno statistical differen-ce is found between the mean value of the standard and20#,25#,30#K file measurements. Group Raypex:The mean value between the standard and 8#,10# K file measurements diffe-rs significantly while no statistical difference is found between the meanvalue of the sta-ndard and 15#,20#,25#,30# Kfile measurements.Group ProPex:The mean value between the standard and 8# K file measurements differs significantly while no statistical difference is found between the meanvalue of the standard and 10#,15#,20#,25#,30# K file measurements.Group APEX-EYE: The mean value between the standard and 8# K file measurements dif-fers significantly while no statistical difference is found between the meanvalue of the standard and 10#,15#,20#,25#,30# K file measurements. 2.The accuracy of Root ZX is 85%; the accuracy of Propex is 87.5%;the accuracy of Reypex is 90%;the accuracy of APEX-EYE is 90%.It is found that all the files of different diameters affect the results measured by the four electronic apex locator species.The results obtained by files of significantly different diameters from those of root canals are statitically smaller while the results obtained by files of diameters similar to those of root canals are of no statistical significance.Evaluated by the standard value(from the apical constriction±0.5mm to the reference point on the crown),the accuracy sequence of measuring results is Root ZX |
PDF Full Text Request