주근단공의 조건에 따른 Root ZX의 정확성 평가 = An evaluation of Root ZX according to the condition of major foramen

다국어 초록 (Multilingual Abstract)

In teeth which have lateral foramen, major foramen deviated from the main axis of root, radiographic appearance of working length determined by electronic apex locator (EAL) often looks "short". In such teeth, it is difficult to determine working length. And the open apex has comparatively large apical foramen and lacks of apical constriction, determining accurate working length is difficult.
The purpose of this study was to assess the accuracy of Root ZX (J.Morita) according to the location of major foramen and open apex.
Total 81 mandibular premolars with mature apices were selected. After standard After access preparation, 54 teeth were classified according to the location of major foramen under surgical microscope (x16, Carl Zeiss Co). Tip foramen (group I, along to the main axis of root) or lateral foramen (group II, deviating from the main axis of root). 27 teeth were fabricated to simulate open apices. The sequence for simulating open apices was cutting 2 mm from the root apex and actual length was determined visually with #10 K file (Dentsply Maillefer) through the canal until the tip was flush with the apical surface. The canals were instrumented with a #2 Peeso reamer (Dentsply Maillefer) to the actual length. A divergent open apex was prepared by retrograde apical preparation with a .04/50 K3 file (SybronEndo) inserted to the length of the cutting blade (D 16). #10 K file was inserted into the root canal until the signal on the display flashed "APEX" and withdrawn to the bar indicating apical constriction ("0.5 Mark") and it was fixed at the location using glass ionomer cement. The apical 4 mm of the apex was carefully removed along to the main axis of tooth to expose tip of file. The distance from file tip to major foramen was measured by calibrating metal ruler (0.5 mm increments) on graph paper under surgical microscope (x25). The data was statistically analyzed using ANOVA and Scheffe post hoc test at p = 0.05 level.

The results were as follows:

1. Mean distance from file tip to the major foramen was as follows. group I was 0.308 mm, group II was 0.519 mm and group III was 0.932 mm.
2. Root ZX located apical constriction accurately within ± 0.5 mm in group I;85.71%, group II; 59.09% and group III; 33.33%.
3. There was a statistically significant difference in distance from file tip to the major foramen between group I and III (p<0.05).
4. There were no statistically significant differences in distance from file tip to the major foramen between group I and II as well as group II and III.

In this study, Root ZX located apical constriction accurately regardless of location of major foramen. However Root ZX couldn't it in open apex. Clinicians have to use a combination of methods to determine an appropriate working length at open apex. It may be more successful than relying on just elecronic apex locator.