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The controversy of the lateral canal- why don't you get all those wonderful accessories in your cases?
We all have been there. You sit in on a lecture by a famous endodontist using a warm gutta percha technique and marvel at all the wonderful accessory canals that are filled. You may even take a course or two (usually given at their expensively equipped ultra-modern laboratories) and work on extracted teeth. In most of those cases your results are spectacular but when you return to your practice you are discouraged by the lack of similar results, especially in vital cases. Why is there such a difference? Why can't you achieve the same results?The answer is quite simple. Most lecturers use necrotic cases when they show examples of treated cases. Many of these have impressive bifidities, spectacular lateral and accessory canals that are quite impressive when blown up on a screen. They invariably have large lesions of endodontic origin that heal perfectly when such high quality treatment is rendered. We also have to remember that these few cases have been chosen out of the many thousands that may have been treated by the lecturer.

Remember to ask the lecturer a few simple questions:
(1) Lets see some examples of vital cases with such spectacular anatomy.
(2) How long did treatment take?
(3) How long did the case sit with irrigation in the canal?
(4) Was treatment performed in a single or multiple appointments?
The truth is that the attainment of spectacular anatomy depends mostly on the tissue solvent ability of the Sodium hypochlorite. NaOCl works far better on necrotic tissue than on vital tissue. The solvent ability of the irrigant is dependent on basically two factors:

(1) The concentration of the irrigant
(2) The time in contact with tissue (preferably necrotic)

Other factors can increase the solvent ability of the irrigant such as heating the solution or the addition of surface-active agents (Surfactants) such as Tween 80, Sodium Laurel Sulfate or Zephiran.

Vital cases (by nature) tend to have less spectacularly filled anatomy because of the lack of penetration of the irrigation. In years past this was countered by the fact that multiple appointment endodontics used to be the norm. After two or three appointments, any tissue that may have originally been vital was made non-vital by file manipulation. This is also why for many years (aside from the outdated and inaccurate culturing techniques), single appointment or "one shots" were officially discouraged by many leading endodontists and institutions.

Because we worked much more slowly, multiple appointment cases had solution in contact with the canal walls for as much as two or three times the duration of the single appointment case. With the advent of the Ni-Ti rotary system, treatment times have been cut even further (some claim by as much as 75%). Unless there is a conscious effort made by the clinician to have these prepared cases "soak", the contact time of the NaOCl with the canal will be even less. Unless the canals are cleaned very efficiently with these instruments, the lesser irrigation times may be detrimental to the case. This is especially critical in cases with fins and isthmi. Rotary instruments, used in a circular motion are not able to clean these areas, meaning that contact time with tissue solvents is even more critical than in hand files cases.

Schilder's original Warm Gutta Percha cases are an excellent example of how techniques have evolved. Although he had been initially criticized for making his preparations "too wide", what many clinicians did not realize at the time was that these preparations facilitated greater irrigation of the apical third. This in turn allowed for better solubility of the deeper portions of the canal, giving rise to the excellent fills and predictability of treatment that had only rarely been achieved with more conservative preparations and cold filling techniques.

So we can see that the attainment of beautiful filled anatomy (with warm gutta percha) in extracted teeth can often be more a function of the fact that they are extracted (and the necrotic tissue remaining readily responds to NaOCl) rather than that of any special technique.

Cleaning and shaping will continue to be the primary method of ensuring canal cleanliness and ultimately, endodontic success. Irrigation is an essential part of cleaning and shaping. Cleaning facilitates shaping by removing pulp remnants. Shaping facilitates cleaning by allowing penetration of tissue solvents into the deeper portions of the canal, giving rise to the spaces that are ultimately sealed by the warmed gutta percha, sealer or a combination of the two.