ROCANAL
Root Canal Therapy
by Dr. Edgar J. Corneo-Lobenstein
A Biotechnical System
According to N. Ripp(1) the best root canal filling
material is the vital pulp. No doubt that the healthy pulp
is ideal from the biological point of view. However, it is
also true that if the pulp is ill and infected, it can be
considered the worst canal filling.
It is obvious that between these two standards, there is a
therapeutical possibility, even better, a therapeutical
necessity.
The purpose of therapeutical intervention is not to
restore the biological ideal, but to reach the position of
compromise which permits functionality without subsequent
pathological consequences.
Biology and Biotechnique
The root canal treatment must be done with the aid of
technological means. They have to be efficient and
conceived in a manner to avoid negative consequences,
although they are not biological in the literal sense of
the word. This is the field of biotechnology.
What does it mean?
First of all, it means that we must not consider what has
been planned by the dictates of "ideal" biology, since
they are unattainable.
We shouldn't run the experimental tests based on ideal
biological reaction, because the reaction differs from our
intentions and possibilities. On the contrary, we have to
program our therapeutical intervention in such a way to
reach the desired final clinical result.
As a practical example, it is known that eugenol cement is
an excellent root canal filler (2,4). This is due to its
adhesion to the walls (3) and to the presence before
setting, of eugenol. But the biological "tests" proved
that eugenol is toxic for cell cultures such as
fibroblasts (4). Based on these results. one is lead to
believe that the use of eugenol should be avoided since it
appears to be antibiological. However eugenol is also a
useful and powerful disinfectant: its phenol coefficient
is 9.7 (5). Upon the final setting of the cement, this
action diminishes considerably and this explains the
minimum irritability and the excellent tolerability in the
zone of periodontium at the apex (6). Furthermore eugenol
diffuses by imbibition, so it reaches zones which have not
been instrumented and cleaned.
D. Orstavik (24) affirms that there are few data to
indicate that superior biocompatibility is essential for
endodontic treatment success. Endodontic problem cases are
usually successfully treated when antiinfective measures
have been effective. Significant improvement in endodontic
therapy may be expected when control on infection can be
achieved regularly and predictably. Possibly, insertion of
materials with a controlled release of an antibiotic,
disinfectant, or pharmacologically active substance may be
advantageous.
So, ideal biological requirements give place to clinically
proved final result. It is just what is expected to be and
it can be obtained by bio-technical programming.
Problems related to current methods
Current methods may be resumed on the triad proposed by
Naidorf in 1974 (7): Instrumentation - Sterilization -
Obturation.
Many efforts have been made to improve these procedures in
accordance with biological ideals.
For these reasons, the term sterilization has been changed
in "disinfection".
It is given more importance to a thorough cleaning and
shaping of the complete root canal system rather to the
chemical disinfection (26).
The filling material of choice is gutta-percha, considered
an inert material.
Orstavik (24) gives more details: Permanent obturation
after cleansing, shaping, irrigation and medication.
The same author states that the infectious nature of
apical periodontitis and of many of the failures after
endodontic therapy makes it likely that the antibacterial
aspects of treatment will remain important in the future
(16).
He also states that Bacteria-associated endodontic
failures together with pulpo-periapical infections
refractory to conventional treatment represent the
unresolved bacteriological problems in endodontics (16).
The antibacterial aspect cannot solve completely the
problems: the root canal is not just some kind of "tube"
which can be cleaned, irrigated, dried and then sealed
hermetically. Instead it is a capillary system which can
be cleaned only in its main parts.
There will always be micro remnants of the pulp, left in
zones not touched by our chemo-mechanical intervention.
The presence of smear layer (formed during mechanical
preparation of the dentine walls) certainly does not help
in attaining an aseptic situation since it includes
organic substances and bacteria.
Considering the problem under a pure biological aspect
Spangberg (1982) (8) has demonstrated that antibacterial
activity is always accompanied by cytotoxicity. Limiting
the action to the extemporary disinfection seems to be
unproper. The action is time-limited and, soon after it
has exhausted itself, bacteria are present again (13).
The irrigation with sodium hypochlorite seems also to be
unproper. Its hemolitic action has been demonstrated even
at a diluition of 1:1000 (28) and serious complications in
its therapeutic use are well known (28,29).
As a matter of fact, the search for an "ideal"
disinfectant is still on, as well as that of a perfect
cleansing solution ...which practically do not exist.
Wollard et Al. (1976) (9) documented that none of the
methods for obturation of the root canal space with
gutta-percha was efficient.
Munaco et Al. (1978) (10), Moller et Al. (1984) (11),
showed that guttapercha remains highly toxic.
Elmiger (1979) (12), demonstrated that the perfectionistic
obturation methods (three-dimensional vertical
condensation of heated gutta-percha) did not give complete
filling in narrow canals.
The presence of periodontal "buttons" of guttapercha,
consequence of condensation pressure, is not ideal.
In effect, gutta-percha, or more precisely, the mixture of
gutta-percha, zinc-oxide and other additives, if placed
beyond the apex in the periodontium, is not inert at all.
It is not resorbable, it will always irritate and may
provoke a reactive chronic inflammation as well as an
acute one.
Since gutta-percha has no function in the canal (not even
that of sealing), it is necessary to use a cement which
will close the coronal and apical zones of the canal and
dentine tubuli. The efficacy of endodontic cement is
diminished because the cement itself is reduced to a
minimum quantity.
Generally, it is known today that the majority of
pathogenic bacteria are anaerobes (14,15). Therefore, the
ideal place for their growth is a canal sealed by an inert
material or by one that
does not act against anaerobes. Sooner or later there will
be a secondary infection (13).
According to Orstavik (20) infection is the dominating
cause of apical periodontitis and probably of failures
after endodontic treatment.
To day antibacterial properties of endodontic materials
are a controversial issue, whereas relative non-toxicity
and/or bone-growth stimulating activity is considered
desirable by most clinicians and researchers (20).
In the past, some practitioners believed in "magic"
properties due to particular pharmacologically active
substances (19), permitting simplified operative
procedures ("mummification"). In Europe there have been
two attempts to solve the biological pulpar problem:
partial fixation of pulpar wound with paraformaldehyde
(21) and biopulpotomy of vital pulp (22). Unfortunately
the results were not the expected ones. The fault was in
the vain belief that with that therapy the pulpar remnants
could undergo its own cicatrical transformation and
eventually calcification.
The treatment and final filling of the root canal has to
be reconsidered.
Biotechnical Programming
Bio-technical programming is based on two requirements
focussed in the canal treatment: eliminate the possibility
of autolysis and heterolysis.
Gravenmate (17) has written: in the enclosed pulpal
space, toxic compounds are formed by the action of
extracellular enzymes from microorganism and by the
autolysis of proteins from pulpal tissues. Endodontic
intervention should strive to remove both processes. Any
remaining tissue should also be mummified, or fixed, as it
is called in chemical terms. By definition, such fixation
also leeds to disinfection. Since disinfection does not
necessarily lead to fixation, this point of view contrasts
with current therapy that is primarly focused on the
disinfection of the contents of root canal.
Also J.C. Hess (18) states that the terapeutical aspect in
root canal treatment must follow two lines: 1) the
microbicidal, 2) the anti-catabolic action of enzimatic
lysis.
All these aspects have conducted us to consider the root
canal treatment not on the basis of pure biological
concepts, but giving more emphasis to the bio-technical
means. They have conducted us to distinguish the canal
treatment of vital teeth from the treatment of gangrenous
canals.
The reason is that in the first the autholytic processes
are the main problem, while in the second one, the
heterolytic action of bacteria has to be more considered.
The Difference between Pulpectomy of Vital Pulp and
Extirpation
The distinction between vital pulp and gangrenous canal
content must be considered because the treatment is
different since the bacterial situation is different. It
is possible that in the vital pulp bacteria are absent or
present only because brought in during intervention.
In necrotic canals instead, the intervention needs
particular pharmacological treatment, as well as operating
precautions, in order to avoid the transport of germs in
the periapical zone. The bacterial flora is different:
especially anaerobes and fungi.
During the treatment of silent, chronic forms, periapical
flare-up may occur, because the work performed in the
course of mechanical cleansing of the canal, may cause an
unintentional inoculation in the periodontium more easily.
It is possible to prevent or at least to reduce these
reactions if, immediately upon the preparation an
antibiotic-antiinflammatory based medicament is applied in
the periodontium by passing through the
canal with a syringe. We have been using since long a
dermatological cream, neomycin-cortisone based (not
perfumed, not greasy and not radioopaque). Just a small
amount is sufficient. The intervention is not obligatory,
but, often it helps. Sometimes, in difficult situations,
it can be repeated after a day or two. The final filling
will be effected when the periodontal symptomatology
ceases, i.e., when the danger is over.
But, the canal must be prepared first: it is cleaned and
in the meantime disinfected in the same first sitting, to
the apex. For this purpose we use a lubricant with a
disinfecting action, based on povidone-iodine, a iodofor,
mixed with a water-soluble substance. It is an ideal
medicament because it is visible during the application,
it acts on a large antibacterial spectrum and even in the
presence of pus or blood (see table 1). When the
preparation of the canal is finished, the lubricant can be
easily removed with a simple washing.
If it is unintentionally brought over the apex, it does
not cause pain and it is not dangerous if it gets to
patient's tongue or if it is accidentally swallowed.
Water-soluble povidone-iodine is quite an efficient
antiseptic for preparation of the canal prior to permanent
filling.
An antiseptic must act immediately and must not be left in
the canal for long period of time as medication with the
intention to obtain a prolonged nontoxic disinfection. Any
disinfectant is toxic, otherwise it would not work.
Consequently, the less it stays in the canal, the better
it is. Povidone-iodine can be used as temporary medication
between sittings, before permanent filling, by placing a
paper-cone saturated with it. But, as soon as the
"danger-period" of a flare -up has ceased, it is suggested
to close permanently the canal.
In the case of a gangrenous pulp, no medicamentous
treatment beyond the apex is recommended (like iodoform or
calcium hydroxide), only the antiinflammatory cream, as
described.
Irrigation
In our practice the use of toxic and dangerous irrigating
substances (such as sodium hypochlorite) has been
eliminated for a long period of time. Also the use of
hydrogen peroxide (perhydrol) has been abandoned because
of its hemolytic action.The foam which it develops comes
out of the canal, goes in a coronal direction, but also
beyond the apex, causing small hemolysis with subsequent
post-operative pain. It has also been abandoned because of
its poor cleansing and antiseptic actions.
The only irrigation is carried out at the end of the
preparation before the permanent filling.
The liquid used is an hydroalcoholic solution of
quartenary ammonium base (Hyamine 622), a surface-active
cationic agent. It is bactericidal even in minimum
concentration, deodorizes and is highly detergent (see
Table 2).
It also dries easily because it is a hydroalcoholic
solution and there is no need for hard drying with hot
air, which, if performed for a long time, could cause
enphysematous reactions.
Believing that the irrigation eliminates completely all
organic substances and the smear-layer is a concept which
does not take into consideration the real anatomic
situation of root canals (27).
Permanent Filling
The filling of the root canal, the final part of our
intervention, has been programmed in a way to act where
the cleansing-disinfection did not arrive.
The filling is obtained using exclusively cements and not
other materials, like gutta-percha.
We have distinguished the closing of the canal after
vital pulpectomy and the closing which follows the
treatment of gangrenous tooth.
As we have already explained the grounds are different: in
one we have more to consider autolytic processes, in the
second the heterolytic. For these reasons the cements
used are two.
The first cement, used to fill pulpectomized teeth, is
based on the pharmacodynamic aid of Orthophenylphenol (OPP).
The addition of OPP must not "evoke" the spectre of
dangerous, toxic substances, as some surveys tend to
suggest because of the toxicological aspects of certain
phenolic compounds.
There are some of them, like OPP, which show very positive
data (see Table 3). OPP is used also in the food industry,
for conservation of citruces. It has an inhibitory action
on certains enzymes which, under anaerobic conditions can
promote the formation of sulfate-reducer bacteria and even
the proliferation of formalin-resistant bacteria.
The second cement is used to fill treated gangrenous
canals and contains Nitrofurazone and OPP.
The pharmacodynamic function has two distinct moments:
immediately after the introduction in the canal and after
the cement setting.
These two cements harden to a gutta-percha like
consistency. They showed excellent tolerability (25) and
are resorbable beyond the apex but not in the canal.
Conclusion
The bio-technical treatment programmed as described above,
has given very good results. The clinical documentation is
very positive (see clinical cases). It started about 20
years ago.
In the past some teachers have said that it was "more
important what has been removed from the canal than what
has been put in".
We think that it is fundamental, in root canal treatment,
to consider every step as being part of a complete
program.
Continue to Part II >> |
