The working length

16 July 2016

Enrico Cassai

After having realized a minimally invasive access cavity and removed the coronal interferences (preflaring) the next step is passed to the scouting of the apical third canal as described in the two preceding articles of Dr Massimo Giovarruscio (

The advantages of the apical third scouting only after a preflaring in summary are:
– Best touch control for clinician in negotiating the apical third
– Gradual increase in the amount of available irrigant
– Reduction of the accumulation of dentin chips
– Better control of the apical foramen

The scouting phase terminates with the achievement of the correct working length.


The current, most common, and predictable method in determining the working length is the electronic apex location, which allows to introduce the concept of "electronic apex" that completes and integrates the concepts of anatomy and radiographic apex allowing the clinician to obtain reliable results. TIPS & TRICKS - Always take a measure of WL on preoperative rx - Check the WL during all steps of the endodontic therapy, from scouting to the glide path to the shaping: more curved is canal and more it tends to shorten the WL - Do the preflaring - Attention to the presence of metallic restorations that can give false readings - The reading of the WL must happen gradually in the apex locator scale - The instrument must have an intimate contact with the canal walls for a correct reading: in presence of large canals use bigger files - Do not perform readings in the presence of excessive humidity the canal


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