| Objective The purpose of this study was to determine the accuracy of the ROOT ZX apex locator under different clinical conditions,and try to find out the influent factors in order to guide clinical practice.Materials and Methods Teeth with mature root apices and planned for extraction because of orthodontics,periodontics,Nasopharyngeal carcinoma or prosthodontic reasons were used in this study.After obtaining the right access to the canals,The teeth were cut horizontally into a flat surface to obtain a stable and unequivocal reference for all measurements before the coronal portion of each canal was flared using number 1 to 3 Gates Glidden,and then irrigated with 0.9%sodium chloride,after that,according to the manufacturer's instructions,a file was introduced in the canal until the signal on the screen reached the "apex" mark which indicated that the file tip arrived at the apical major foramen,a rubber stop was then carefully adjusted to the reference level and the distance between the rubber stop and the file tip was measured to the nearest 0.01mm with a digital caliper and recorded.Then the file was inserted into the root canal again until the signal flashed "Apex" and retracting the file until the display read 0.5mm which was the mark of apical constriction or the minor foramen,adjusted the rubber stop,measured and recorded.All canals were measured by using ROOT ZX apex locator under different size of stainless-steel K-files and different root canal humidity when the signal on the screen reached the "apex" mark and the "0.5"mark as described ahead.And the teeth were extracted and sterilized.The actual canal lengths from the crown reference to the major foramen were determined by placing a file into the canal until the tip of the file was just visible at the major apical foramen under a microscope at 10×magnification.With the file was inserted into the canal again,the apical 4-mm of each root was shaved using a finishing bur along the axis of the tooth until the file could be seen through a thin layer of dentin which was carefully removed to expose the canal under the microscope at 10×magnification.Then adjusted the rubber stop when the end of the file reached the minor foramen or the apical constriction,measured and recorded the actual canal length from the reference to the minor foramen.Informed consent was obtained by each patient.All patients were gathered from the department of oral and maxillofacial surgery in the Affiliated Stomatological Hospital of Guangxi Medical University during September to November in 2006.To eliminate any bias that would be contributed by a systematic error in ROOT ZX apex locator measurements related to uncontrolled variables(e.g,tooth length),the difference between Electronic measuring length(EML)and the Actual length(AL)was compared with using one-sample T test and the five-way analysis of.variance (ANOVA)was conducted to investigate the influence of vital/necrotic pulp, single-rooted/multi-rooted,small/large K-file and dry/wet canal on the measurement error in locating the major foramen and the minor foramen.P value was set at 0.05.Results 1.General data:49 teeth with mature apices and 64 root canals altogether were used in this study,among these teeth 36 were single-rooted and 13 were multi-rooted,40 were vital pulp and 9 were necrotic pulp,among the 64 canals,only 50 had measurements because 5 were fractured during extraction and 9 could not be measured for too small canals.2.There was no significant difference between the Electronic measuring length and the Actual length (P＞0.05).3.In locating the major foramen,the ROOT ZX apex locator was 75.65%,95.34%and 100%accurate to within±0.5mm,±1.0mm,and±1.5mm respectively.In locating the minor foramen,the ROOT ZX apex locator was 77.71%,98.09%and 99.36%accurate to within±0.5mm,±1.0mm and±1.5mm respectively.4.Five-way ANOVA showed that among these factors, including vital/necrotic pulp,single-rooted/multi-rooted,small/large K-file and dry/wet canal,only measurements of the vital pulp provided greater accuracy compared with the necrotic ones(F=5.037,P=0.025＜0.05)in locating both the major and minor foramen,but the difference(0.08mm)were not clinically significant,other factors had no significant influence(P＞0.05)on the measurement error with all the interactions between these factors being insignificant(P＞0.05).Conclusion The result of this study indicates that the ROOT ZX apex locator has high accuracy in clinical practice.The accuracy of ROOT ZX apex locator in locating both the major foramen and the minor foramen is not adversely affected by the four factors,including vital/necrotic pulp, single-rooted/multi- rooted,small/large K-file and dry/wet canal. |
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