Which is not a non-radiographic methods of determining the working length:
NON-RADIOGRAPHIC METHODS
Tactile Sense
If the coronal portion of the canal is not constricted, an experienced clinician may detect an increase in resistance as the file approaches the apical 2-3 mm. This detection is by a tactile sense. it is ineffective in root canals with an immature apex and is highly inaccurate if the canal is constricted throughout its entire length of if it has excessive curvature. This method should be considered as a supplementary method. If the canals are not preflared, determination of the apical constriction by tactile sensation would be possible in only one-third of the cases
Apical Periodontal Sensitivity
Based on the patients’, responses, dentists observe the ‘eye twitching’ sign. This is no more an acceptable method. Leads to too shorter determination of working length, in cases of inflamed tissues and overestimation in cases of non-vital teeth with periapical pathology
Paper Point Method
Paper points in the root canals with immature apex are the most reliable means determining the working lengths. This method is gently pass the blunt end of the paper point into the canal after profound anaesthesia is achieved. The moisture or blood on the portion of the paper point that passes beyond the apex may be an estimation of working length. This method cannot be used in weeping canals. This is a supplementary method. Paper points with millimetre marking have been introduced, recently.
Tactile sensation.
Apical periodontal sensitivity.
Paper point method.
Bergman's Method.