ABSTRACT
The aim of this study was to compare the working length in the curved mesial canals of mandibular molars between pre-flared and non-flared groups. It was a comparative study which was carried out at Dental Department of PIMS [Pakistan Institute of Medical Sciences] Islamabad from 2003 to 2004. A total of 60 patients were divided equally into pre-flared and non-flared groups. In both groups a 15 # K file was used for the measurement of working length but in the pre-flared group the coronal portion of the canal was flared with Hedstrom files [25-55] or Gates Glidden Drills from # 02 to # 05 before inserting the # 15 K file. Then the tooth was radiographed at this moment and the distance between the tip of the file and the radiographic apex. The location of the tip was classified as a] within 1 mm of the radiographic apex b] more than 1 mm of radiographic apex c] over extended, beyond the radiographic apex. In the non-flared group 33.3% of the cases belonged to group [a], 40% to group [b] and 26.7% to group [c]. In the pre-flared group 73.3% of the cases belonged to group [a], 10% to group [b] and 16.7% to group [c]. It was concluded that when the coronal portion of the canal is constricted, then the clinicians cannot discern the accuracy of what they feel apically because quite often the file bends or stucks more coronally than apically. When the coronal portion of the curved canal is pre-flared or prepared then it greatly improves the access to apical portion of curved canal and thus to the apical constriction, which is an apical reference for correct working length determination, by removing the dentinal hindrances in the coronal portion of the curved canals. Thus pre-flaring is a highly recommended procedure, especially in curved canal for correct working length determination