Australian Dental Journal, August, 1964 309

N2 root canal treatment

Angelo Sargenti, D.M.D. (Zurich)*

A comment on the paper “Root canal treatment with N2” b y E . H . Ehrmann in the Australian Dental Journal, 8 : 5, 434-438 (Oct.) 1063.

The denomination N2 has mnemonic mean- ing and symbolizes both the material and the technique of application.

N2 was developed in Switzerland during the last fifteen years and is now employed by an ever increasing number of dentists in Europe and the whole world. It is developed on a com- plete scientific basis including clinical, histo- logical, and physical data laid down in broad international literature published by neutral and competent research agencies and indi- vidual researchers stating its safety and effectiveness i n use.‘l)

It should be emphasized tha t distinction must be made between teeth with vital pulp, at least in the apical par t of the root canal, and those teeth which are gangrenous. We therefore have two groups of teeth:

Group A with vital pulp (accidentally ex- posed sound pulp, hyperemic pulp, acute serous pulpitis).

Group B with all conditions of infected necrotic pulp or doubtful apical pulp with and without rarefaction area (apical in- volvement).

The gangrenous teeth ((froup B ) have to be mechanically cleansed and disinfected (well debrided and cleansed) in several sittings, step by step, and root-filled to the apex.

In teeth with vital non.infected pulps a simpler approach is possible because the canal

* Lecturer, University of Pavia, Dental School. Received for publieation July, 1964.

(1) Sargenti, A.-Hqndbuch der ratlonallnierten XVurz3lbehsndlung mit Nachtrag : Die Wlnnen- schnftliche Untermauerung der N2 Methode. Indra Verlag. Lonsone. 1963.

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content is vital and the apical region is intact. I n dealing with vital cases the N2 method adopts the clear biological directions given by Coolidge,(*) “A satisfactory tilling in a root canal from which a vital pulp has been removed is one that obliterates the canal 88 far as the pulp has been removed. If the pulp has been destroyed and removed to the apical foramen the filling must be extended to the apical foramen, but if there is a small amount of living tissue near the apical foramen that has not been destroyed or too severely injured by mechanical, chemical, or bacterial irritants, the filling should be inserted to the level of the living tissue, which will heal and remain in healthy conditions.”

The ideal place for the termination of the canal filling is the dentino-cementa1 junction. Unfortunately, the complicated anatomical conditions of the human root do not always permit the ideal condition to be reached. Coolidge and Keselc2) stated that i n curved or obstructed canals the vital pulp may be severed at the curve or at the point of obstruction. The filling should be inserted to the level of the living tissue, which will heal and remain i n healthy condition.

Strindberg‘*) claims that better results can be obtained if the canal in vital teeth is not filled exactly to the apex. During the Third Conference Endodontics, October, 1963, in

(*)Coolidge, E. D., and Kesel, R. G.-A textbook of endodontology ; including the clinical pathology and treatment of tho dental puln .-nA nulp1e-s teeth. Philadelphia, Lea & Fehiger, 2nd ed., 1956.

Strindberg, L. Z.-The dependence of the results of pulp therapy on certain factors. Acta Odont. Scandinav. 14 , Supp. 21, 1956.

310 Austral ian Dental Journal, Augus t , I964

Philadelphia, this observation was clearly ex- pressed by Frostell(‘) and Seltzer, Bender, and Turkenkopf.‘6) Reports of seminar-discussions held a t this Conference stated “that root canal filling in pulpectomy (Group A of N2 cases) should terminate a little short of the apical foramen”. Whereas in non-vital cases (Group B of N2) “the filling material should extend t o the apical foramen”. These principles coincide with the N2 technique. Frostell(‘) stated that “if the canal is not penetrable to the apex, the canal should be filled up to the obstruc- tion in the canal”.

Concerning the method of treatment for acute serous pulpitis, the following statement of Nygaard @stby@) is cited: “The apical part of the pulp consists of fibrous connective tissue, which retains its structure and its sterility, even in cases of severe, chronic inflammation of the pulp. Consequently, the so-called partial pulp extirpation, i.e., the placing of the extirpation wound in the apical par t of the canal, is the safest therapy in these cases”.

An example of healing following the use of N2 has been reported recently by R0we.c-

In the case reported by Ehrmann in the October, 1963, issue of the Australian Dental Journal, the N2 material was not correctly administered: in a vital case the apical region and the mandibular nerve were severely damaged during canal instrumentation. For such cases the N2 method prescribes extirpa- tion of the pulp a little short of the apex with strict respect for the apical region. Ehrmann’s statement that “the case of Mrs. R. L. was treated according to the N2 method” does not correspond to the principles emanated by the authors of the method. The treatment described by Ehrmann does not correspond to conventional treatment practices for vital cases either.

The material was violently forced beyond the apex against both the prescription of the N2 method’s authors and basic endodontic principles. A non-absorbable material, developed for the canal, was pushed into the apical region

C4) Frostell, Q.-Factors influencing the prognosis of endodontic treatment. Transactions of the Third Intern. Conference on Endodontics. Ed. L. I. Crossman, Philadelphia, 1963.

(8) Selzer, S., Bender, I. B., and Turkenkopf, S.- Factors affecting successful repair after root c nal therapy. J.A.D.A., 67 : 651-662 (Nov.) ,863

and forced into the mandibular canal pre- viously damaged with instruments. This was done in spite of the fact that in the book describing the N2 method, as well as in the labelling accompanying the N2 material, it is clearly indicated that the material must not be forced beyond the apex.

The symptoms described by Ehrmann were a logical sequence of this incorrect treatment; they would have appeared if any other non- absorbable material had been applied in the way related by Ehrmann. Ehrmann’s affirma- tion that materials such as Kerr’s Sealer, Diaket, or AH26, when forced beyond the apex would not have resulted in the symptoms described, is arbitrary and not supported by valid evidences: i t is known that such materials result in violent reactions when forced beyond the apex because of their non- absorbability and foreign-body reactions, as Menkin@) stated.

Several of Ehrmann’s statements do not correspond to the principles of the N2 method and must be rectified. 1. His affirmation “Sargenti makes no

attempt to remove necrotic debris from the canal” is inexact: the authors of the method demand, in handling gangrenous cases, well cleansed and debrided canals. We gain the impression that Ehrmann confounds gan- grenous teeth with teeth containing non- infected sound vital pulps, for which cases the method prescribes partial removal of the pulp in accordance with procedures concern- ing the amputation of a sound non-infected pulp as accepted and taught in European dental schools for many years.

2. In Ehrmann’s report the impression is given that the method is severely criticized in Switzerland in spite of the fact that i t has been employed for many years in this country by the majority of dentists. The statement that the Committee on Therapeutics of the Swiss Dental Association does not approve N2 does not correspond to the facts: this Com- mittee had to withdraw its attitude which was proved to be biased.

3. The author cited by Ehrmann, Tschamer, as having stated that the use of N2 was un- favourable, was obliged to acknowledge that his evaluation was not valid-a fact known to Ehrmann long before publication of his report. _.

Nygaard Ostby, B.-Pulp and root canal treat- ment. Internat. D. J., 1 3 : 23-30 (Mar.) 1963.

sealer. Rrit. D. J.. 117: 27-30 (July 7) 1964. York, Macmillan Co. , 1950. ‘ 7 ) Rowe, A. H. R.-Treatment with N T root canal ‘w Menkin, V.-Dynamics of inflammation. New

Australian Dental Journal, August, I964

4. Among other inexactitudes I feel obliged to take up Ehrmann’s assertion “according to Sargenti and Richter instruments are not sterilized”. We use, for sterilization, a new agent, Agasol-Solution,* which was tested a t the Bacteriological Department of the Uni- versity of Zurich (Prof. Grumbach) and was found capable of performing total sterilization of instruments after one half hour: every micro-organism a t that time, including Myco- bacterium tuberculosis, was destroyed.

Ehrmann’s paper-though relating an in- teresting unfortunate accident during endo- dontic treatment-obviously cannot be of any value in judging a method of treatment which,

* dynwul: eth1,svAi;~ininoacridine lactate (Merck). ______

31 r when correctly employed, is used with success in a great number of cases during a period of many years by endodontists.

The N2 technique offers simplification in endodontic treatments. This method, as described by its authors, is based upon bio- logical principles and enables the dentist to control all affections of the pulp and peri- apical tissues with a minimum of time and labour.

The aim of all endodontic work is to prevent the extraction of functioning teeth; it is our duty to practise a method which is as simple and safe as possible.

Palazzo Urbania, Locarno,

Switzerland.

Bacterial wulls When bacteria are examined under a microscope or an electron microscope they are seen to possess characteristic physical features. These include their overall shape and the presence or absence of flagella, hair-like structures, gelatinous capsules, and internal granules. Such features are recognized in the classification of the organisms. Nevertheless, although wide variations occur in the possession of these detailed features, all bacteria conform to a general structural pattern; they consist of cytoplasm enclosed by a thin fragile membrane, usually called the protoplast membrane, and a much thicker structure, the wall, surrounding this. In some cases the wall is itself surrounded by a gelatinous mass, the capsule.

The wall and its immediate vicinity are particularly important parts of the organism. The wall itself is interesting, because it must possess structural rigidity for its function in protectr ing the cytoplasm and its membrane from the considerable osmotic forces that bacteria encounter, yet i t must be permeable to nutrients and metabolites. As it represents up to 20 per cent of the dry weight of the cell, an appreciable proportion of the metabolic activity of bacteria is concerned with the synthesis of the wall and its precursors. I ts importance in bacterial metabolism has been recognized since the discovery that the main action of penicillins on bacteria is to interfere with the biosynthesis of the wall and to cause the accumulation of precursors. Another important aspect of walls relates to the behaviour of bacteria in the tissues of a n infected animal; antigens in the organisms stimulate the production of antibodies in the serum, and the subsequent antigen-antibody reactions are significant in assisting the animal to overcome the infection. Many antigens are in, or associated with, the wall. I t ’ is Clear therefore, that knowledge of the chemical structure of the wall is important for”a good understanding of many aspects of the biology and chemistry of bacteria.+. Baddtley. Endeavour. January, 1964.