A Study of the Dentinal Permeability of the Pulp Chamber Floor of Human Lower Molars With Separate Roots
Jesus Djalma PÉCORA
Wanderley Ferreira COSTA
Geraldo MAIA CAMPOS
Faculdade de Odontologia de Ribeirão Preto Universidade
de São Paula, Ribeirão Preto, SP Brasil
Braz Dent J (1990) 1(1): 17-24 ISSN 0103-6440
| Introduction | Material
and Methods | Results | Discussion
| Conclusion | References |
The permeability of the dentin of the pulp chamber floor of lower molars
with separate roots was studied, after instrumentation of the root canals
by manual or ultrasonic techniques. The dentinal permeability was evaluated
by the degree of penetration of copper ions in the tissue and quantified
by methods used in morphometry. None of the combinations of irrigating
solution/instrumentation technique caused an increase in the permeability
of dentinal tissue in the pulp chamber region, probably because the dentin
is reparative dentin, which is more amorphous and less tubular than primary
Key words: dentinal permeability, pulp chamber floor.
The permeability of coronal and radicular dentin has been studied extensively
(Bodecker and Applebaum, 1933; Beust, 1934; Marshall et al., 1960; Pécora,
1985; Pashley et al., 1987), however, the permeability of the dentin of
the pulp chamber floor of molars has received little attention.
Moss (1965), using stains, investigated the dentinal permeability of
this region, in deciduous teeth and concluded that the dentin is more permeable
in teeth with necrotic pulp.
Macchetti and Campos (1975) studied various drugs used in pediatric
dentistry, comparing their action on permeability of the dentin of the
floor of the pulp chamber in deciduous teeth. For this investigation, they
used 131I as the detector of dentinal permeability, concluding that formalin,
cresol formalin, and tricresol formalin increased this permeability. '
Sasso et al. (1966), studying the dentin of human molars, verified the
presence of reparative dentin on the floor and the roof of the pulp chamber,
observing that this dentin was directly related to the defensive capacity
of the pulp against caries. They also noted that the reparative dentin
presented hypocalcification, with fewer tubules irregularly distributed,
even loosing their tubular configuration.
The lack of research on the permeability of dentin in the pulp chamber
floor in permanent molars prompted the present investigation, not only
to test the permeability of dentin when it is submitted to the action of
irrigating solutions during the instrumentation of root canals, but also
to verify the type of dentin present in this region.
Material and Methods
In this experiment, we used 40 human teeth, permanent first and second
molars, all with separate mesial and distal roots.
Two instrumentation techniques were used in the root canals - manual
and ultrasonic - associated with irrigating solutions - distilled water
and Dakin's solution. The Dakin's solution, prepared at the Endodontic
Laboratory of the School of Dentistry of Ribeirão Preto, University
of São Paulo, was 0.58% chloride at pH 9.20.
The 40 teeth were divided into four groups: 1) manual instrumentation
with distilled water; 2) manual instrumentation with Dakin's solution;
3) ultrasonic instrumentation with distilled water; 4) ultrasonic instrumentation
with Dakin's solution.
The outer surface of the teeth was impermeabilized with cyanacrylate,
with the exception of the occlusion surface and the apex of the roots.
The access to the pulp chamber was performed by a routine clinical technique.
The manual instrumentation was performed as follows: localization of
the canals, determination of the working depth in the apical limit, use
of three files in sequential increasing size from that which determined
the anatomic diameter. The irrigating solution used was 10 ml per canal.
The final cleansing was performed by irrigating each canal with 10 ml distilled
The ultrasonic instrumentation was done with the Brazilian ultrasonic
unit Profiendo (Dabi-Atlante, Ribeirão Preto, SP, Brazil), using
only two files of sequential increasing size, for 11/ 2 minutes per file.
The irrigating rate was 3 ml/minute. The final cleansing was performed
with distilled water energized by ultrasound, with a number 15 file in
the root canal.
After the instrumentation of the canals, the teeth were immersed in
a container with 10% copper sulfate solution for 30 minutes, in a vacuum
for the first 5 minutes. After this time, the teeth were dried with absorbent
paper and placed in a 1% rubeanic acid solution. The same time periods
in solution and vacuum were observed as above. The rubeanic acid reveals
copper ions, forming a stained compound ranging in color from deep blue
to black, depending on the quantity of copper ions present (Feigl, 1958).
Upon completion of this reaction revealing the extension of the penetration
of copper ions, the teeth were placed in acrylic blocks and 500- mm mesiodistal
longitudinal sections were obtained with a diamond disk. During this process,
the disk and acrylic block were cooled with jets of water to avoid burning
the dental tissue. From each tooth, about 5 sections were obtained from
which only those that passed through the central region of the furcation
These sections were filed to a thickness of approximately 200 mm, washed
in running water for 4 hours and then dehydrated in an increasing alcohol
solution series, cleared in xylene, and mounted on glass slides for microscopic
examination. The quantification of the penetration of copper ions was done
using morphometric methods, with a 400 point grid inserted into the microscope
eyepiece. The number of points in the stained and non-stained areas of
the dentinal furcation were counted.
This region, of triangular shape, was outlined as follows: the vertex
was the upper external concave point of the region of the furcation and,
from this point, two orthogonal lines were drawn until they reached the
inner floor of the pulp chamber.
Once the number of points in the stained and non-stained areas were
determined, the percent of copper ion penetration in the dentin was calculated
by the following equation: where PC indicated the points in the stained
dentin and PN, the points in the unstained area.
Table 1 shows the percent of copper ion penetration in the dentin of the
pulp chamber floor in the furcation region of the molars studied.
An arc sine transformation of the original data was necessary in order
to make the sample distribution normal and the variance homogeneous to
allow for the application of parametric statistical tests.
The analysis of variance (Table 2) was statistically non-significant
for the main factors of variation (solutions and instrumentation techniques)
as well as for their interactions.
In spite of the non-significance indicated by the parametric statistical
analysis, the non-parametric Kruskal-Wallis test (Table 3) was also applied
for comparison and confirmation.
The Kruskal-Wallis test confirmed the results shown by analysis of variance
that there was no significant difference in the degree of copper ion penetration
of the dentin of the pulp chamber floor, in the furcation region between
the roots, either between the two solutions (distilled water and Dakin's
solution) or between the two instrumentation techniques of root canals
(manual or ultrasonic) or even between their interactions.
The histological sections, examined by an optic microscope, magnified
40, 1W, 2W, and 400 X, showed the presence of reparative dentin in most
of the pulp chamber floors examined (Figures 1 and 2).
The region outlined by 2 orthogonal lines, with the vertex at the upper
point of the external concave area of the furcation in the human lower
molars with separate roots, was considered to be the region of the furcation,
extending to the floor of the pulp chamber. This area was established to
avoid including, in this study, the dentinal permeability of the cervical
area of the root canal, as this area receives the direct action of instrumentation
and irrigation while the floor of the pulp chamber is subject only to the
action of the irrigating liquid.
The use of the identification method of copper ions is justified by
its high reproducibility (Pécora, 1985; Zuolo et al., 1987; Silva,
1988), by the fact that copper ions are much smaller than the stained molecules,
and by permitting the sections to be diaphanized for microscopic examination.
Water was used as the irrigating solution because it does not increase
the dentinal permeability during root canal instrumentation (Marshall et
al., 1960; Pécora, 1985). Dakin's solution was chosen because halogenic
solutions increase dentinal permeability (Pécora, 1985) besides
dissolving organic tissue (Moorer and Wesselink, 1982) and provide cleaner
root canals when energized by ultrasound (Ahmad et al., 1987; Vansan, 1988).
The quantification of copper ion penetration, by the use of a point
grid, offers security and objectivity in calculation and comparison of
the areas, as well as ease of use (Pécora, 1985; Zuolo et al., 1987;
The comparison of the two techniques of root canal instrumentation was
done to verify if the agitation of liquid in the pulp chamber, during ultrasonic
instrumentation, offers a better result in the increase of permeability
of the dentin of the pulp chamber floor than manual instrumentation, in
which the irrigation solution only wets the walls of the floor.
The statistical analysis of the results obtained in this study shows
that there was no significant difference in the degree of penetration of
copper ions in the dentin of the pulp chamber floor, either with the use
of water or Dakin's solution, or with manual or ultrasonic instrumentation,
or with any combination of these factors.
The histological examination showed the presence of reparative dentin
in the pulp chamber floor in the analyzed teeth, amorphous dentin with
a reduced number of tubules, proving the findings of Sasso et al. (1966).
Sasso et al. (1966), Mjör (1972) and Seltzer and Bender (1975)
report that the irregular (or reparative) secondary dentin forms more on
the floor and the roof of the pulp chamber than on the lateral walls; and
that, while the regular (or physiological) secondary dentin forms during
the entire life of a tooth as a response to physiological stimuli, irregular
(reparative)- secondary dentin forms as a response to injury to the pulp
Due to the fact that the reparative dentin appears more amorphous, less
tubular and less regular than primary dentin, the passage of liquid is
hindered, since the reduction in the number of available dentinal tubules
leaves this dentin without its principal path of penetration.
When the pulp chamber floor consists of primary dentin and regular secondary
dentin, the penetration of copper ions is more uniform than in the presence
of reparative dentin.
The method used and the results obtained permit the following conclusions:
I. Distilled water and Dakin's solution as irrigating solutions are
equal in relation to the permeability of dentin of the pulp chamber floor
of lower molars with separate roots. .
2. The two techniques used in the instrumentation of root canals (manual
and ultrasonic) were not significantly different statistically in relation
to the degree of copper ion penetration in the dentin of the pulp chamber
floor of the molars studied.
3. The interaction of instrumentation techniques and irrigating solutions
did not show statistical significance in relation to the degree of copper
ion penetration of the dentin of the area studied. .
4. The statistical non-significance of the irrigating solutions and
the instrumentation techniques as well as the interaction of the solutions
and techniques can be attributed to 2 factors: .
a) the fact that the floor of the pulp chamber consists of reparative
dentin, more amorphous, less tubular, and less regular than primary dentin,
which hinders the passage of copper ions;
b) the fact that only the irrigating solution comes in contact with
the floor of the pulp chamber, leaving the cleaning of this region to only
the hydraulic movement of the irrigating solution.
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Correspondence: Professor Jesus Djalma Pécora, Departamento
de Odontologia Restauradora, Faculdade de Odontologia de Ribeirão
Preto, Universidade de MO Paulo, 14050 Ribeirão Preto, SP, Brasil.