Page 15 - The Beauty and Sorrow in Endodontics (WL and C/S)

forcing the files in. Once an obstruction is felt, back up while simultaneously rotating

the file (cleaning the coronal portion), then take the file out, examine, clean, and again
pre-curve the file before placing it back into the canal again and allow it to slide

apically without resistance. Do not force the file in and risk perforating or transporting

the canal, instead, follow the natural flow of the canal – the final canal shape should
resemble its original form (Figs A10, A11, A12, A13, A14, A15).

G. Taper

After cleaning and shaping, canals should exhibit a continuous tapering form (Fig A16).

The canal diameter of any horizontal section should be wider towards the coronal
sections and narrower towards the apical sections. It is recommended that an apical

taper of at least 0.06 is necessary to allow for proper cleaning and shaping of the
apical third; this means that starting from the apex, the diameter of the canal through a

horizontal section increases by 0.06mm with each 1mm coronal advancement. With

this in mind, operators should still consider the existing dentinal wall thickness in
each root (Figs A17, A18), as forcing a 0.06 taper in thin-walled roots can result in

perforations or other complications. Even without perforations, if the walls become
too thin due to over-instrumentation, there is a high risk of root fracture in the future

(Fig A19).

Coronal Flaring is Required to Obtain a Precise Working Length

Flaring and enlarging the coronal and middle third of the canal removes the risk of
the file binding to canal walls prior to reaching working length and giving inaccurate

measurements. This also allows for straighter access of the small file to reach working
length and eliminates any inaccuracy that may result from using an endo ruler to measure

a twisted file. Dr. Schilder often said that the endo ruler is great for measuring straight
lines but will always come with errors when the file is curved or twisted. Therefore,

during the author's graduate training period at Boston University, endo rulers were not

allowed in the operatory. Instead, when transferring working length from one file to
another, the larger file will need to be pre-curved to the same degree as the smaller used

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