(PR06) Determining the Working Length in Immature Teeth – An ex vivo Study

This study evaluated the accuracy of different methods and models for working length (WL) determination in immature teeth. 10 extracted human premolars presenting single canal and immature apices were selected and paired with other 10 similar teeth presenting complete root maturation. Preoperative radiographs and cone-beam tomographic (CBCT) scans were taken, and root canal measurements were performed. After endodontic access, the canals' actual lengths (AL) were measured visually under magnification. Teeth were embedded in saline and measurements were performed using #15 files and three brands of electronic apex locators (EAL): AirPex, CanalPro, and Root ZX mini. Then, the apices of the mature teeth were cut to simulate an open apex (SOA). The WLs of the natural and simulated immature teeth were measured using three different files (#15, adjusted, and self-adjusting file). Data was statistically analyzed (significance set at 5%). No significant difference was found when comparing the results of the three EALs (p>0.05). Although using an adjusted file improved the performance of the EALs (p < 0.05), electronic measurements were significantly shorter in immature teeth (p < 0.05). EAL measurements in SOA teeth were closer to AL compared to immature teeth (p < 0.05). CBCT and intra-operative radiographic working length resulted in mean differences of -0.49mm (±.45) and +0.32mm (±.55), respectively, compared to AL. Electronic measurements were not precise in immature teeth regardless of the type of EAL or instrument used. Preoperative CBCT measurements were similar to the radiographic technique but required less adjustments to determine the WL in immature teeth.