Although the available scientific evidence base is short and at considerable risk of bias , it is still possible to conclude that the apical locator reduces the patient radiation exposure and also that the electronic method may perform better on the working length determination .
INTRODUCTION Apical constriction has been proposed as the most appropriate apical limit for the endodontic working length .
Despite being the most used , some limitations are attributed to the radiographic method of working length determination .
It lacks precision because it is based on the average position of the apical constriction .
The electronic apex locators have been presented as an alternative to the odontometry performed by radiography .
These devices detect the transition of the pulp to the periodontal tissue , which is anatomically very close to the apical constriction and may perform with improved accuracy .
In vivo determination of root canal length: a preliminary report using the Tri Auto ZX apex-locating handpiece.
AIM The aim of this study was to assess the clinical perfomance of a cordless h and piece with a built-in apex locator - the Tri Auto ZX - design ed for root canal preparation with nickel-titanium rotary files . METHODOLOGY Twenty-five human maxillary incisor and canine teeth scheduled for extraction with mature apices were selected for the study . Informed written consent was obtained from each patient before treatment . After administration of local anaesthesia , the teeth were isolated and the pulp cavities accessed . The Tri Auto ZX along with a size 15 K-file was used in its electronic apex locating function based on the manufacturer 's recommendations . A periapical radiograph with the file at the electronically determined constriction was taken , the file removed and the measurement registered as the electronic length ( EL ) . To test the auto reverse function , a size 20 ProFile.04 taper NiTi rotary instrument was mounted in the h and piece . The point for the auto apical reverse function was preset on the panel at the 0.5 mm level . After the file was introduced into the canal and reached the predetermined level , the file automatically stopped and rotated in the opposite direction . A reference point was marked and this measurement was registered as the auto reverse length ( ARL ) . All measurements were made twice by two different investigators . Teeth were then extracted and immersed in a 20 % formalin solution for 48 h. After fixation , a size 15 file was inserted into the canal to measure the actual root canal length from the same reference point obtained with the Tri Auto ZX to the apical foramen , as seen in the stereo microscope . When the file tip was visible at the anatomical end of the canal it was withdrawn 0.5 mm and this measurement was registered as the actual length ( AL ) . All measurements were expressed in mm and the measuring accuracy was set to 0.5 mm . The significance of the mean differences between EL and ARL and between EL and AL measurements at the 5 % confidence level was evaluated . RESULTS EL measurements were coincident to ARL in all instances . EL and ARL were coincident to AL in 10 ( 40 % ) canals , in the remaining 15 canals ( 60 % ) the AL measurements were longer than EL and ARL ( + 0.5 mm ) in 14 instances and shorter ( -0.5 mm ) in one case . Overall , the AL was longer than the EL or ARL , the mean difference being -0.23 mm + /- 0.32 ( P < 0.05 ) . CONCLUSIONS It was concluded that the Tri Auto ZX was useful and reliable . The Tri Auto ZX measurements protected against overpreparation
Although the available scientific evidence base is short and at considerable risk of bias , it is still possible to conclude that the apical locator reduces the patient radiation exposure and also that the electronic method may perform better on the working length determination .
INTRODUCTION Apical constriction has been proposed as the most appropriate apical limit for the endodontic working length .
Despite being the most used , some limitations are attributed to the radiographic method of working length determination .
It lacks precision because it is based on the average position of the apical constriction .
The electronic apex locators have been presented as an alternative to the odontometry performed by radiography .
These devices detect the transition of the pulp to the periodontal tissue , which is anatomically very close to the apical constriction and may perform with improved accuracy .