Disadvantage of handing method

Based on hand feeling and patient’s pain, dentists decide whether the measuring tool reaches apical foramen, with high subjectivity and low accuracy. Foreign literature suggest that providing the range of error +0.5 mm, accuracy of handing method is only 42%.
 

 

Disadvantage of X ray film

3D structure shooting at 2D plane, because of different angles, easily getting wrong data. Apical foramen can’t be shown in the X ray film, for over 80% apical foramens are in the side edge instead of apex.