Working length determination in palatal roots of maxillary molars.

The purpose of this study was to determine if a buccal curvature in the palatal roots of maxillary molars affected the clinician's ability to accurately determine working length. Twenty-seven extracted, human maxillary molars were sorted by palatal root curvatures as J- and C-type, and the angle of curvature was determined. Straight-line access was made and a #20 file was placed into the canal until the tip was visible at the apical foramen then withdrawn. The file, tooth, and calibration wire were radiographed on one image using the RadioVisioGraphy system. Actual (file) and radiographic (tooth) lengths were determined using the RadioVisioGraphy ruler. Radiographic length appeared shorter on average than the actual length. Canal curvatures larger than 25 degrees had differences greater than 0.5 mm. This represents a statistically significant difference between the actual and radiographic lengths as the degree of curvature increases. There was no significant difference between the J- and C- types.