Page 30 - The Beauty and Sorrow in Endodontics (WL and C/S)

How Do We Know When Canal Shaping is Sufficient?

Generally, it is suggested that if a master GP cone can be placed into a canal without
resistance all the way to the lWL (see “Working Length”), then the basic shaping of the
canal has been completed. Don’t forget, the purpose of shaping the canals is to: 1) create
a natural flow within the canals to allow for penetration of irrigants into the space for

disinfection, and 2) allow for easier obturation of the system. For the irrigants to fully
remove the pathogens and debris within the lateral and accessory canals, two main
conditions must be met: 1) the main canal must be enlarged enough to allow for irrigant

penetration, and 2) there must be sufficient contact time between the irrigants and the
pathogens.

The Most Common Obturation Material – Gutta Percha

Gutta percha (GP) is made from a palaquium tree that is unique to Southeast Asia

(Fig B8). After removing the tree bark, the saps are then collected (Fig B9), extracted,
and solidified for various usages (Fig B10). The earliest record of use can be traced back
to China. The substance is plasticized and can be shaped when warmed due to changes in

its physical lattice phase. In nature, the substance is present in the α phase, and is quite
unstable. Many commercial products, on the other hand, belongs to the more stable β
phase. The chemical structure of gutta percha is similar to that of rubber, the only
difference is that at the double band, one is a cis- and the other is a trans-bond. Even
though there are many obturation materials available, gutta percha is the most commonly

used.

Non-Standard or Conventional Gutta Percha Points

Since the 1960s, most dentists have wanted the obturation material to correspond to
the files in their size and taper. In other words, they want to be able to place a master GP
cone that corresponds to the master apical file right down to lWL with no resistance. Due
to material restrictions of stainless-steel files in the ISO system, the only available taper
is 0.02, and so the corresponding taper of GP cones are 0.02 as well. The tip sizes of the

GP cones mimic the file sizes as well (0.15, 0.20. 0.25, etc). However, once the canals are
cleaned and shaped, it is inappropriate to obturate with a 0.02 tapered GP cone, since they
are almost never evenly 0.02 tapered. Therefore, many GP cones with >0.02 taper started

to appear in the markets and were termed “non-standard GP” (Fig B11). Dr. Schilder,
however, preferred to call them “conventional GP”, so they are less likely to be

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