Endodontology
Enhanced CPD DO C
Ajinkya M Pawar
Shishir Singh
Significance of the Coronal
Pulp Chamber Floor Anatomy in
the Human Dentition:
A Narrative Review
Abstract: In root canal treatment, the foundation on which all surgical procedures are performed is a thorough knowledge of the anatomy
of the pulp chamber and the root canal system. The endodontic triad comprises biomechanical preparation, microbial control and complete
obturation of the root canal space. Knowledge of the pulp chamber floor anatomy is important in locating the numbers and orifices of root
canals present within the tooth being root canal treated. This is particularly important while treating teeth that are heavily restored, malpositioned, or calcified. The current review attempts to explain the complex anatomy of the pulp chamber floor and its significance in root
canal treatment.
CPD/Clinical Relevance: To allow the location of all root canal orifices in the pulp chamber and to perform successful root canal treatment,
knowledge of pulp chamber floor anatomy is essential. The clinician should consider that, as the external morphology of the tooth varies in
individuals, so does the internal morphology.
Dent Update 2021; 48: 58–61
The pulp complex should be visualized
as beginning occlusally at the pulp horns
and ending at the apical foramina. In order
to remove pulp tissue entirely from the
Ajinkya M Pawar, BDS, MDS, Assistant
Professor, Department of Conservative
Dentistry and Endodontics, Nair Hospital
Dental College and PhD Scholar,
Department of Conservative Dentistry
and Endodontics, TPCT’s Terna Dental
College and Hospital, Mumbai, India.
Shishir Singh, BDS, MDS, PhD, Professor
and Head, Department of Conservative
Dentistry and Endodontics, TPCT’s
Terna Dental College and Hospital,
Mumbai, India.
email: ajinkya@drpawars.com
58 DentalUpdate
pulp complex, the coronal portion must
be accessed in a manner that will permit
pulp removal and facilitate the location
and debridement of the root canals
without unnecessarily compromising
the strength of the coronal enamel and
dentine. The variation of the pulp chamber
floor, especially in multi-rooted teeth,
is a constant challenge for diagnosis
and subsequent root canal treatment.1
Attempting to treat the root canal system
without detailed anatomical information
could be potentially disastrous. There is
an abundance of literature describing root
canal anatomies, but the studies that have
considered pulp chamber anatomy have
been very generic and offer little insight on
how to determine the orifice number and
location of root canals.2
One of the major reasons for root
canal treatment failure is 'missed canals.'
The access to the pulp chamber is also
determined by a preset and well-defined
set of laws. These are the laws of centrality,
concentricity, cemento-enamel junction
(CEJ), symmetries, colour change, and
orifice location. CEJ, an anatomical
landmark, still remains the pilot guiding
towards an ideal access cavity preparation
aiding the location of all the root canals.3
There is a generic description of the
average number of canals in different
teeth. While the average number of canals
in a tooth is of some value, it may vary
in the individual tooth of an individual
person. The available literature regarding
the location of canal orifices has been
presented in an unsystematic manner.
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Endodontology
Figure 1. Coronally cut sample exhibiting law
of centrality.
Figure 3. Coronally cut sample exhibiting law of
symmetry 1 (red line) and symmetry 2
(white line).
canal bleeding points.7
The aim of this review is to highlight the
importance of the anatomy of the coronal
pulp chamber floor.
Anatomy of the coronal pulp
chamber floor
Figure 2. Coronally cut sample exhibiting law
of concentricity.
Typically, it has been suggested that
access to the cavity should be made in an
approximate position in the clinical crown,
and then a search for the orifices made
in the hopes of finding them. However,
locating canal orifices in teeth that are
heavily restored, broken down due to
extensive caries, or have had improper
earlier access cavities is extremely
problematical, as normal anatomy is
often badly damaged.2 Also, factors such
as physiological ageing, pathology and
production of secondary and tertiary
dentine may increase the difficulty in
locating canal orifices.4–6
Clinically, there are a number of
diagnostic measures that can be taken
to locate root canal orifices, including
multiple pre-operative radiographs, cone
beam computed tomography (CBCT),
examination of the pulp chamber floor
with a sharp explorer, troughing of
grooves with ultrasonic tips, staining the
chamber floor with 1% methylene blue
dye, performing the sodium hypochlorite
'champagne bubble' test and visualizing
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Knowledge of the anatomy of the tooth
being root canal treated, with the anatomy
of the adjacent tissue, is most important for
successful removal of the pulpal tissue. For
successfully removing the contents of an
entire root canal system, the coronal pulpal
chamber and the radicular pulpal tissue
must be identified.
Krasner and Rankow formulated new
laws, providing guidelines for locating the
pulp chamber and root canal orifice. The
existence of constant landmarks makes it
easy to locate orifices systematically and
more successfully, especially in cases where
locating orifices has become difficult.8
The coronal anatomical laws have been
proposed to aid in access cavity preparation
and are discussed below.2
The law of centrality states that the
floor of the pulp chamber is always located
in the center of the tooth at the level of
the CEJ (Figure 1). This law can be used
as a guide to prepare to access the cavity.
But care should be taken, as this law only
applies at the level of CEJ and is not related
to the occlusal anatomy of the tooth
being root canal treated. This law may not
apply when treating a tooth that is heavily
restored with an oversized crown, since the
location of the center of the tooth might
be misleading.2
The law of concentricity states that
the walls of the pulp chamber are always
concentric to the external surface of the
tooth at the level of the CEJ. This law helps
the clinician in extending access to the
cavity efficiently. If there is a presence
of any bulge of the CEJ in a particular
direction, the pulp chamber also extends in
that direction (Figure 2).2
The law of symmetry 1 states that,
except for maxillary molars, the orifices
of the canals are equidistant from a line
drawn in a mesial-distal direction through
the pulp chamber floor (Figure 3). The law
of symmetry 2 states that, except for the
maxillary molars, the orifices of the canals
lie on a line perpendicular to a line drawn in
a mesial-distal direction across the centre of
the floor of the pulp chamber (Figure 3).
The law of colour change states that the
colour of the pulp-chamber floor is always
darker than the walls. The law of orifice
location 1 states that the orifices of the root
canals are always located at the junction of
the walls and the floor. The law of orifice
location 2 states that the orifices of the root
canals are located at the angles in the floorwall junction. The law of orifice location
3 states that the orifices of the root canals
are located at the terminus of the root
developmental fusion lines (Figure 4).
The law of orifice location 1 and 2 may
be used to identify the number and position
of the root canal orifices, as all the orifices
are located along the floor–wall junction.
These two laws, in conjunction with the
law of colour change, are the only reliable
indicator for the location of second canals in
mesiobuccal roots of maxillary molars.9 The
law of orifice location 2 may guide towards
the actual location of the root canal orifices,
with the vertices (ie a point where two or
more lines/walls meet) and/or angles of the
darker chamber floor specifying the position
of the root canal orifices. In cases of calcified
canals, the position of the vertex will dictate
the penetration of the bur, aiding in removal
of reparative dentine from above the root
canal orifice (Figure 5). The laws of symmetry
1 and 2 (except for the maxillary molars),
colour change, and orifice locations 1 and 2
can be applied to any tooth.2
Discussion
A major cause of failure in root canal
DentalUpdate 59
Endodontology
Figure 4. Coronally cut sample exhibiting law of
orifice location 3. Arrows mark the developmental
root fusion lines.
Figure 5. Coronally cut sample exhibiting
calcified pulp stone (arrow) and vertices on the
pulp chamber floor.
Figure 6. Coronally cut sample exhibiting
four canals.
treatment is the inability to locate, debride
and obturate extra canals. There are
numerous studies reported in the literature
on the root canal anatomies of multirooted teeth (premolars and molars).10–14
These teeth often exhibit multiple canals.
If they are considered to have multiple
60 DentalUpdate
canals, knowledge of the coronal pulp
chamber floor of these teeth is most
important.15 If the clinician is not familiar
with the chamber floor, the chances of
missing root canals are high. Walton and
Torabinejad16 and Ash and Nelson17 have
rightly reported that the pulp morphology
of teeth is often extremely complex and
highly variable.
Distinct laws have been proposed for
locating pulp chambers and the multiple
orifices present on the pulp-chamber floor,
on the basis of precise patterns and the
relationship between the pulp chamber
and the pulp-chamber floor. Knowledge of
the laws of orifice location helps prevent
clinicians from causing crown perforations
in a lateral direction. For example, as
the law of centrality states that the pulp
chamber is always centrally located at
the level of the CEJ, the operator can use
the CEJ as a circular target regardless of
how non-anatomical the clinical crown or
restoration may be. Even if the crown sits
at an obtuse angle to the root, the CEJ can
still be a reliable landmark for locating the
pulp chamber. Also, after restoration of a
tooth, the occlusal anatomy may have no
relevance to the position of the underlying
pulp chamber.2
Many clinicians have preconceived
ideas of the anatomy and position of the
pulp chambers and root canals, based on
the conventional clinical presentation of
faultless teeth in textbooks. Gaining access
to the pulp chamber is recommended
from the external surface of the tooth to
the internal surface (ie the pulp chamber),
based on this ideal anatomy. However, this
recommendation has little relevance when
treating pretreated, restored, or crowned
teeth, and may lead to perforation.
The first step in endodontic treatment is
the preparation of the access cavity, which
provides an opening in the dental crown
that allows localization, cleaning, shaping,
disinfection and obturation of the entire
root canal system. An access cavity that
has been prepared improperly in terms
of position, depth, or extent will hamper
the achievement of optimal results.18 The
CEJ is the most accepted and established
anatomical landmark and is regarded as
the paramount landmark for locating the
pulp chamber.2
The law of centrality helps to prevent
coronal lateral perforations when gaining
access to the pulp chamber, as it is
located centrally at the level of the CEJ.
The clinician may use the CEJ as a target
irrespective of the anatomical alteration
of the coronal structure.
The law of concentricity helps
clinicians to extend their access
appropriately. The clinician may refer
to the bulge of the CEJ and extend
the access cavity in that direction. For
example, in cases where the tooth
is narrow mesiodistally, the clinician
can infer the pulp chamber is also
narrow mesiodistally.
In order to be sure that the access
cavity is adequate, the clinician needs
to know the law of colour change.2
The access cavity is deemed complete
when the clinician can successfully
visualize the entire pulp chamber floor.
The law states that the colour of the
pulp chamber is always darker than
the surrounding walls. As the cut walls
are lighter, there is a junction, which is
formed by light walls and the dark pulpal
floor. If this junction is not observed at
the pulp chamber floor, it is a hint to the
clinician that the i cavity preparation
is incomplete and the overlying tooth
structure must be removed. Establishing
this junction clearly helps in applying
the laws of symmetry and orifice
location to find the exact positions and
numbers of orifices. Knowledge of the
laws of symmetry 1 and 2 immediately
indicates the presence of a fourth canal.
Indeed, it not only implies the presence
of a fourth canal, but exactly where it
is located (Figure 6). The law of orifice
locations 1 and 2 may be used to locate
the position and number of root canal
orifices, because all of the orifices are
located along the floor–wall junction,
and any black and white markings or
indentations, observed anywhere else
must be ignored to avoid any possible
perforations. If the canal is calcified, then
this position at the vertex will indicate
with certainty where the operator
should begin to penetrate with the bur
to remove reparative dentine from the
upper portion of the root canal. The law
of orifice location 1 and 2, in conjunction
with law of colour change, is often the
only reliable indicator of the presence
and location of extra canals.
In cases with anatomical variations,
January 2021
Endodontology
endodontic treatment initiation,
instrumentation and completion may be
carried successfully with the clinician being
familiar with basic knowledge of the laws.4
While gaining access during root canal
treatment, magnification with illumination
by either dental operating microscope or
dental loupes enhances the quality of vision
for identifying the root canal orifices more
easily.19,20
Each tooth demonstrates a variety of
root canal configurations that must be
thoroughly disinfected, increasing the
success rate of root canal treatment. With
the development of CBCT, it has become
possible to visualize the anatomy and root
canal system of the teeth, owing to the
three-dimensional (3D) images obtained.
Cases with unusual root formations, such as
dens in dente (tooth within a tooth), multirooted lower premolars, C-shaped molars,
or cases with excessively curved canals, may
benefit from a CBCT scan. Many studies
have used this technique to finvestigate the
anatomy of the root canal system especially
in multi-rooted teeth.21–24
This article correctly recommends
the use of the CEJ as a reference level for
correct access orientation. However, to
use the CEJ as an anatomical reference,
we suggest that beginners use retentive
rubber dam clamps with narrow jaws,
curved and slightly inverted, to help with
gingival displacement when placed below
the maximum diameter of the crown of the
tooth being treated.
Compliance with Ethical Standards
Conclusion
9.
In spite of all of our best efforts, problems
during root canal treatment can occur. The
above description can help to overcome
and remedy the most common problems
that a practitioner might encounter. The
observer should be cautioned, however,
that the number of orifices does not
necessarily correlate to the number of
canals. Sometimes, more than one canal can
be present in a single orifice.
Conflict of Interest: The authors declare that
they have no conflict of interest.
Informed Consent: Informed consent was
obtained from all individual participants
included in the article.
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Acknowledgements
This review is a part of PhD dissertation
being carried out in the Department of
Conservative Dentistry and Endodontics
at Terna Dental College and Hospital, Navi
Mumbai affiliated to the Maharashtra
University of Health Sciences, Nashik.
January 2021
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