Written by : Dr. Urusa I Inamdar
Diagnostic radiograph of tooth used to estimate the working length by measuring the tooth from a stable occlusal reference point till radiographic apex
Subtract atleast 1 mm from this length as minor constriction is present short of the anatomic apex and compensation for radiographic image distortion.
This measurement is transferred to a diagnostic instrument with a silicon stop then placed in the root canal and working length radiograph is taken.
Now measure the difference between the end of the instrument and radiographic apex of the root , on the radiograph.
Tip of the instrument ends 0.5 mm – 1 mm from the radiographic root apex – working length established .
- Short of the radiographic apex by more than 1.0 mm – then add this value to the earlier estimated length and adjust the stopper on diagnostic instrument accordingly.
- Beyond the radiographic apex – reduce this value from the earlier estimated length and adjust the stopper on diagnostic instrument.
Retake the working length radiograph .
- If periapical bone resorption is evident in a radiograph , the working length should be reduced 1.5 mm short of the radiographic apex as the apical constriction would have been destroyed by the resorption .
- If apical root resorption is seen , the working length is reduced to 2 mm short of the radiographic apex , in such an event , an apical stop is created short of the radiographic apex to prevent overinstrumentation and subsequent overfilling of the root canal .
- Grossman’s Endodontic Practice (13th edition)
- Dental notes