Internal anatomy of tooth

 Introduction
 Pulp chamber anatomy
 Root canal and classification of root canal systems
 Apical foramen
 Accessory foramen
 Apical constriction
 Isthmus
 C shaped canals
 Anatomy of individual teeth
 Developmental disturbances
 Conclusion
 References

What we cannot see, we cannot negotiateand
what we cannot negotiate we fail to
prepare!

 Beyond the simple perception is often the intricate internal tooth anatomy and a
complex root canal system.
 Root canal treatment has transformed remarkably since the hollow tube theory was
postulated in 1930.
 Research into the morphology of the pulp has revealed that the dental pulp takes
many intricate shapes and configurations before reaching the tooth apex.
 As a professional, one should be aware of all the probable nooks and crannies of the
complex root canal, its protean permutations and combinations, to render the finest
possible treatment.

Apical foramen
Lateral canals
Furcation canals
Pulp chamber
Pulp horn
Floor
Roof

Krasner and Rankow studied the pulp chamber of 500 extracted teeth and their
consistent observation regarding the pulp chamber anatomy in all teeth led to the
formulation of new laws, forming guidelines for locating the pulp chamber and root
canal orifice.
The anatomic laws/patterns observed are categorized into two groups:
1) Relationships of the pulp-chamber to the clinical crown.
2) Relationships of the root canal orifice on the pulp chamber floor.

• Law of Centrality: the floor of the pulp chamber is always located in the center of the tooth
at the level of the CEJ (cemento-enamel junction).
• Law of the CEJ: The CEJ is the most consistent, repeatable landmark for locating the
position of the pulp-chamber.

 Law of symmetry 1: 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.
 Law of symmetry 2: 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 center of the floor of the pulp
chamber.
 Law of Color Change: the color of the pulp chamber floor is always darker than the walls.

• Law of orifice location 1: the orifices of the root canals are always located at the
junction of the walls and the floor.
• Law of orifice location 2: the orifices of the root canals are located at the angles in
the floor wall junction.
• Law of orifice location 3: the orifices of the root canals are located at the terminus
of the root developmental fusion lines.

Type I
Mature straight roots (having closed apex with apical
constriction)
Slightly Curved Severely Curved Dilacerated Bayonet
Type II
Mature but not straight root canals, which may be:

A. Tubular root apex
B. Blunderbus apex
Type III
Immature (open apex) canals
(Straight or curved)

Type I: Single canal with single orifice and
single apical foramen
Type II: A canal with a single orifice that divided into
two canals and exit with a single apical foramen
According to Weine
Classification of the root canal system

Type IV : Single canal with two orifices and
two apical foramen
Type III : Two canals with two orifices and
single apical foramen

Type V –a root canal configuration having more than two canals that branched off
from the main canal more than 3mm from the apex defined as another main canal.

Sert and Bayirli in 2001 reported fourteen new root canal configurations, which
were not included in the classification by Vertucci or other classification
systems

According to Gulabivala & co - workers

 Root canal curvatures were classified by different authors as
follows:
 By Ingle and Taintor (1980) and Pucci and Reig (1986).
 Apical curve.
 Gradual curve.
 Sickle-shape curve.
 Dilacerations.
 Bayonet.
 Zidell’s (1987) classification of root canal systems.
 Severe curve.
 Dilacerated curve.
 Bayonet curve.
 Apical bifurcation.
 Apical curve.
 Additional canals.
 Lateral and accessory canals.

 Schneider’s (1986) classification on the basis of degree of curvature in the main
root canals. It is measured using protractor.
 Easy: straight and curved <5º
 Average: curved >10º and <25º
 Difficult: curved >25º
D) According to Weine curved canals are also grouped based on their degree of
curvature.
i) Curvatures of 30º to 45º
ii) Curvatures of 45º to 60º
iii) Curvatures of 60º to 90º
iv ) Curvatures of greater than 90º
v) Bayonet curved canals.

 E) Backman et al (1976) and Southard et al (1990) classified root canals on the basis of
“Radius Quotient” which was obtained by dividing a given angle by its radius
measurements.
 F) Dobo Nagy et al (1971) devised a classification based on Schneider’s angle and the
radius of the circle that could be superimposed on the curved part of the root canal.
 G) Mathematical classification of root canal form, by Csaba Dobo Nagy et al in 1995 is
as follows.
 Straight or ‘I’ form.
 Apical curve or ‘J’ form.
 Curved canal along its entire length or ‘C’ form.
 Muticurved or ‘S’ form.

1. Tooth apex (radiographic apex)
2. Apical foramen (major foramen)
3. Apical constriction (minor foramen)
1
2
3
Anatomy of the Root Apex (Kutler’s studies)

According to Ingle
the anatomy of the root apex is partially determined
number location
apical blood vessel
(during development of the apex)
 young and erupting tooth
the foramen is funnel shaped
The mouth of funnel shaped is filled with the periapical tissue,
which is later replaced by dentin and cementum.
As the root develops, the apical foramen becomes narrower.

 The apical foramen is the
main apical opening of the
root canal.
 It is frequently eccentrically
located away from the
anatomic or radiographic
apex.
 An accessory foramen is an
orifice on the surface of the
root communicating with a
lateral or accessory canal.
 They may exist as a single
foramen or as multiple
foramina

 The location and shape of the apical foramen may undergo changes as a result of functional
influences on the teeth.
 A tooth may be tipped from horizontal pressure, or it may migrate mesially, causing the
apex to tilt in the opposite direction.
 Under these conditions the tissues entering the pulp through the apical foramen may exert
pressure on one wall of the foramen, causing resorption.
 At the same time cementum is laid down on the opposite side of the apical root canal.
 Thus, the principal apical foramen might be in the center of the root originally, the foramen
gradually shifts with aging , mesial and occlusal drift, and continuous
cementum deposition.

 With increasing age, minor diameter of apical foramen becomes narrower while their
major diameter becomes wider from the deposition of dentin and cementum.
 Sometimes the apical opening is found on the lateral side of the apex, although the root
itself is not curved.
 All root canals deviate from the long axis of their roots.

 Green’s detailed studies (1955, 1956, and 1960) of the anatomy of the root
apices of teeth demonstrated the major apical foramens are situated
directly at the apex more frequently in the
Maxillary First Premolar and Mandibular Second Premolar
Maxillary central and Lateral incisors,
In the Maxillary molars and all the mandibular teeth with the exception of the
second premolar the main apical foramina coincide with the apices less
frequently.

The physiological foramen or apical constriction is
considered the narrowest diameter of the root canal and
was thought to be located at the cemento-dentinal
junction.
Langeland histologically demonstrated that the cemento-
dentinal junction being highly irregular (e.g. 3mm higher
on one wall than on the opposite wall) did not at all
coincide with the apical constriction.
Physiological foramen is considered as the apical
limit of the root canal preparation. It is also known as
histological foramen, because it is located at the
junction between the pulpal connective tissue and
interstitial loose connective tissue of the periodontal
ligament.

 The apical constriction of the canal usually occurs within the dentin, just prior to the
initial layers of cementum.
 Kuttler referred to this site as the minor diameter of the canal.
 Site to terminate canal preparation and build up the apical dentin matrix.
 Major diameter was found to be approximately twice as wide as the minor diameter.
 This means that the longitudinal view of the canal seen as tapering funnel till the tip
at exit and then widens again.
 When viewed in longitudinal section the configuration between the minor and major
diameters resembles that of a morning glory flower.

 Apical constriction have been classified by
Dummer et al
 Type A: The traditional single constriction.
 Type B: A tapering constriction with the
narrowest portion of the canal very near to the
actual apex.
 Type C: A number of constrictions were present.
 Type D: Where the constriction was followed by
a narrow, parallel portion of canal
 A fifth type was also seen where the canal had
been completely blocked with secondary dentin
or cementum

 Kuttler reported that the distance between the center of the foramen and the narrowest part of
the apical canal was 524μm (18 to 25 yrs) to 659μm (above 55 yrs).
 Mizutani et al reported the distance to be 0.825 to 1.010 mm.
 The apical constriction tends to occur about 0.5 to 1mm from the apical foramen (Chapman
1969)

 Chapman (1969) noted vast majority of constrictions were found between 0.7
to 3mm from the apex.
 Mizutani et al (1992) reported the vertical distance between the apex and
apical constriction for maxillary anterior teeth were 0.8 to 1.0mm.

 The apical constriction is commonly advocated as the ideal
termination for root canal treatment, being a natural
narrowing of the root canal and almost at the termination of
the pulp.
 This is supposedly where an apical stop is formed against
which the obturation materials are packed.
 As this constriction is usually not present, the apical foramen
may be a more useful landmark.
 The distance between the apical constriction (when present)
and the apical foramen ranges from 0.5 to 1.0mm for the
teeth of different ages.
 When the apical foramen is located, the position, of the apical
constriction (if it exists) can be estimated, if the apical
constriction is not present, the preparation and obturation
will usually be within confines of the root.

 In fact, it is difficult to locate either the apical constriction or the apical
foramen clinically or radiographically.
 Although 0.5 to 1mm short of the radiographic apex is commonly used as the
termination point.
 It is an attempt to debride and obturate close to the apical foremen but
hopefully, not beyond.

 no apical injury
 no injury to the periodontal ligament
 maintenance of accessory lateral canals
 no extrusion of root canal fi lling material
 no apical transport of infected pulpal tissues
 adequate compaction of the root canal filling against the canal walls
 no infected tissue remnants within the canal

 It has been demonstrated that when periradicular lesion is present root resorption
not visible radiographically is likely.
 When the periapical tissue exhibited normal structures ,the corrected working
length should be established 1mm from radiographic apex.
 When bone resorption is evident the corrected working length is established 1.5mm
short of apex.
 When bone and apex exhibit resorption the length should be 2mm from apex.

 Lateral canals and accessory foramina are integral parts of a normal pulp cavity rather
than exceptions.
Location:
A lateral canal can be found anywhere along
the length of a root and tends to be at right
angle to the main root canal.
 Accessory canals usually branch off the main root canal somewhere in the apical region.
 Lateral canals are found in profusion in the roots of posterior teeth and occasionally in the
roots of anterior.
 The presence of lateral canals in the furcation areas of molar teeth is well documented and
their incidence is high.

Content:
 Lateral and accessory canals contain fibrous tissue.
 The connective tissue , same as that found in the pulp but more closely resembles the connective
tissue of the periodontal ligament.
Incidence:
 The incidence of lateral and apical canals reportedly increases in posterior teeth, toward the
apical third of the root.
 In younger teeth and multirooted teeth it has been found to vary from 2-3% to over 72%
 Gross methods of detection, such as vulcanite corrosion specimens of the root canals have
indicated that there is an incidence of 16.9% of such canals, in all teeth (Hess 1925).
 In anterior teeth, accessory and / or lateral canals were observed in an incidence of 34%.

Size:
 According to Hess et al (1983) accessory canal foramina have a mean
diameter of 6 to 60μm.
 The size of accessory and lateral canal structures varies with diameter
ranging from 1mm to size of blood vessels.

 In molars, a multitude of accessory canals are present within the
cementum “web” fusing the roots.
 The presence of a dichotomy or branching of the pulp canal near
the apex of the tooth, giving a Y-shaped branching of the root canal
near the apex of the tooth are evident.
 Such apical deltas were also found to be frequent by Hess et al
(1983).
 In the distal roots of lower molars and in the palatal roots of upper
molars, many anomalies in size and shape of the root canals are
found.
 Frequently, in these teeth the canals fan out toward the apex of the
tooth in a ‘canoe shaped’ arrangement.
 Following endodontic treatment, the pulp tissue in the
uninstrumented branches may become inflamed, but usually retains
its vitality with the passage of time, continuous deposition of dentin
or cementum tends to narrow the lumen of these canals.

An isthmus is defined as a ribbon shaped intercanal connection or transverse
anastomosis or a corridor between two root canals encompassing dental pulp and
pulp related tissue.
Observed between any two root canals within the same root.
As the isthmus houses the dental pulp, it might serve as a potential site for bacterial
growth and thus, making complete debridement of this area indispensible.
Whenever two or more root canals are present, an isthmus should be suspected and all
attempts should be made in detecting and debriding it.

 Type I - Is two or three canals with no notable communication.
 Type II - Is two canals that possess a definite connection between the two main
canals.
 Type III- Is three canals that possess a definite connection between them.
 Type IV- Is when the canals extend into the isthmus area.
 Type V- Is the true connection or corridor throughout the section.

 Cooks and Cox first discovered the C-shaped anomaly in
mandibular second and third molars in 1979.
 There are two common possible outcomes for the C-shaped
mandibular molar those that exhibit.
A single, ribbon like, C-shaped canal from orifice to apex .
Three distinct canals below the C-shaped orifice, the more
common form .
 C-shaped canal prevents effective cleaning, shaping and
obturation during a root canal therapy.
 The C-shaped canal has been observed in mandibular first
premolars, mandibular first, second and third molars,
maxillary first molars and maxillary second molars.
 The occurrence of a C-shaped canal and its improper
negotiation can lead to failure in endodontic therapy and
hence should be gingerly examined.

 The size and shape of the pulp are influenced by age. In the young person, pulp horns
are long, pulp chambers are large, root canals are wide, apical foramen are broad ,and
dentin tubules are wide , regular, and are filed with protoplasmic fluid.
 With increasing age pulp horn recede, pulp chambers becomes smaller in height
rather than in width, and root canals become narrower from deposition of secondary
and reparative dentin.
 Moreover, apical foramen deviates from the exact anatomic apex, and their minor
diameter becomes narrower while their major diameter becomes wider from the
deposition of dentin and cementum.
 Dentinal tubules become narrower and even obliterated by the deposition of
peritubular dentin forming sclerotic dentin, and they lose their regularity and become
tortuous.
 Reparative dentin may be devoid of dentinal tubules, and the moisture content of the
dentin is reduced.

MAXILLARY CENTRAL INCISORS
Length of tooth
(mm)
Canal Lateral
canals
Apical
ramification
s
Root curvature
(%)
Average
length
23.5 One canal
99.4%
23% 13% Straight 75
Maximum
length
25.6 Two canals
0.6%
Distal curve 8
Minimum
length
21.0 Mesial curve 4
Range 4.6 Labial curve 9
Lingual
curve
4

Pulp chamber
follows the contour of the crown
3 pulpal horns
located in the center equidistant
from the dentinal walls.
It is broad mesiodistally,
The chamber is ovoid mesiodistally.

 Maxillary central incisor usually has one canal. There
are many case reports of two root canals in maxillary
central incisor.
 Follows the direction of the curved root.
 Broader labiopalatally,
 Large and simple in outline, conical in shape,
 Centrally located.
 The apical foramen is centrally located in the
anatomic apex in only 12% of cases.

Cross section at three level.
 Cervical level: canal is ovoid mesiodistally.
 Middle root level: canal is ovoid to round.
 Apical third level: canal is generally round in shape.
An unusual large apical third have canal which is
more ovoid
 The mean distance of the apical foramen to the root
apex ranges from 0.30 to 0.49mm
 Lateral canals may be present 23%,
usually 49.1% in the apical third area.
 Apical delta is present in 1% of cases.

Gemination:
Its attempt at division of a single tooth germ by an invagination with resultant
incomplete termination of two teeth.
Incidence 0.5-2.5% in primary teeth.
Incidence 0.00.8% in permanent teeth.
Dental fusion and gemination are used to define two different morphological dental
anomalies, characterized by the formation of a clinically wide tooth.

Fusion :
Union of two normally separated tooth germs. Depending upon the stage of development
of the teeth at the time of union, fusion may be either complete or incomplete. The dentin
however is always confluent in cases of true fusion.
1. Complete:
Fusion begins before calcification. The crown incorporates features of both
participating teeth with regard to their enamel, dentin, cementum and pulp.
2. Incomplete:
Fusion occurs at a later stage. The tooth might exhibit separate crowns and fusion
may be limited to the roots alone with pulp canals fused or separate.

MAXILLARY LATERAL INCISORS
Length of tooth
(mm)
Canal Lateral
canals
Apical
ramifications
Root curvature
(%)
Average
length
22.8 One canal
93.4%
10% 12% Straight 30
Maximum
length
25.1 Two
canals
6.6%
Distal curve 53
Minimum
length
20.5 Mesial
curve
3
Bayonet and
gradual
curve
6

Pulp chamber:
Shape is similar to that of the maxillary central
incisor.
 two pulp horns,
 It is broad mesiodistally
 The division between pulp chamber and root
canal is indistinct.

 Slender shaped , wider labiolingually than
mesiodistally.
 The root apex is sharper than that of the central
incisor, displaying a common deflection to distal
and palatal side.
 The maxillary lateral incisors usually have one
root.
 Variations in number of roots have been reported
but are rare

 Follows the direction of the curved root.
 Maxillary lateral incisor usually has one canal.
 Survey of De Deus (1992) reported that 3% of maxillary
lateral incisors may have 2 canals.
 Walvekar et al in 1997 reported a case of 3 root canals.
 These cases are thought to be the result of abnormal
development of the tooth and the root.
 They often manifest clinically as gemination, fusion and
concrescence.

Cross section at three levels.
Cervical level: Canal is wider in
labiopalatal dimension.
Midroot level: canal is ovoid.
Apical third level: canal is generally
round and gradually curved

 Developmental alterations which are most commonly associated with maxillary lateral
incisors are
 microdontia
 hypodontia
 Dens invaginatus
 Dens evaginatus (talon cusp).
 Microdontia teeth are smaller than the normal size,
 Microdontia of maxillary lateral incisor is called as “peg lateral”
 Crown - cone shaped with converging mesial and distal surfaces.
 Root - usually shorter than crown

 Peg shaped lateral incisors incidence – approx 2% to 5% of the general population
 Women show a slightly higher frequency than men.
 Usually they are found equally on the right and left, unilaterally or bilaterally,
Peg lateral is usually associated with other dental anomalies like
 tooth agenesis,
 maxillary canine first premolar transposition,
 palatal displacement of one or both maxillary canine teeth,
 buccally displaced canine,
 mandibular lateral incisor-canine transposition

 Hypodontia developmentally missing one or more teeth.
 Congenitally missing maxillary lateral incisors are the second most common
dental abnormality
 Absence may be either unilateral or bilateral.
 Associated complications of missing maxillary lateral incisors are
compromised aesthetics and occlusal imbalance in the maxillary and
mandibular dental arch, leading to psychological distress in some patients.

 Dens invaginatus is a developmental anomaly
resulting in a deepening or invagination of the
enamel organ into the dental papilla prior to
calcification of the dental tissues.
 Permanent maxillary lateral incisors are most
commonly involved.
 In ‘dens invaginatus’ the clinical appearance of the
crown may vary, ranging from a normal form to
more unusual forms such as greater labio-lingual
or mesio-buccal diameter, peg-shaped, barrel-
shaped and conical.
 Concurrence of talon cusp and dens invaginatus
within the same tooth is rare.
 For this association, studies have revealed an
incidence ranging from 0.89% to as high as 9.2%.

 Most commonly accepted classification belonging to Oehlers (1957)
who described three types:
 Type I = an enamel invagination in the crown only;
 Type II = an enamel-lined invagination that invades the root but
remains confined within it as a blind sac and may communicate with the
dental pulp;
 Type III = an invagination that extends from the crown to the apex and
is penetrated by a second foramen laterally or apically on the root
surface.
 In this type, any infection within the invagination can lead to an
inflammatory response within the periodontal tissues, giving rise to a
peri-invagination periodontitis

 Dens evaginatus originates in the palatal
cingulus, often being bilateral and is known as
“talon cusp”.
 So, the talon cusp is described as an anomalous
hyperplasia of the cingulum of maxillary and
mandibular incisors resulting in the formation
of a supernumerary cusp resembling an eagle’s
talon.
Complications like Caries,
 Periapical lesions,
 Irritation of tongue during speech and
 mastication
 Occlusal interference accidental cusp
fracture, displacement of the affected tooth,
temporomandibular joint pain and periodontal
problems because of excessive occlusal force

Classified on the basis of degree of formation and extent by Hattab F N
et al (1996) into following three types –
 (1) True talon (an additional cusp that prominently projects from the palatal
surface of a primary or permanent anterior tooth and extends at least half
the distance from the cemento-enamel junction to the incisal edge)
 (2) Semitalon (an additional cusp of 1 mm or more but extending less than
the distance from the cemento-enamel junction to the incisal edge)
 (3) Trace talon (enlarged or prominent cingulum and variations, i.e., conical,
bifid, or tubercle-like).

 Is a developmental anatomic aberration with an infolding of enamel organ and the
epithelial sheath of Hertwig before the calcification phase.
 Embryologically, it is related to a mild form of dens invaginatus.
 The maxillary lateral incisor (LI) is most commonly (93.8%) affected.
 Clinically, a V-shaped notch is seen with altered or interrupted cemento-enamel
junction (CEJ).

MAXILLARY CANINES
Length of tooth
(mm)
Canal Lateral
canals
Apical
ramifications
Root curvature (%)
Average
length
26.0 One canal
96.5%
24% 8% Straight 39
Maximum
length
28.9 Two canals
3.5%
Distal curve 32
Minimum
length
23.1 Mesial curve 0
Lingual curve 7
Bayonet and
gradual curve
7

One Canal
96.5%
Two or
More Canals
3.5%
One Canal
at Apex
98.8%
Two or
More Canals
at Apex
1.2%
Maxillary Canine

 A specimen 33.5mm in length has been reported by
Pucci FM and Reig R.
 Pulp chamber:
 are the largest of all single-rooted teeth.
 Labiopalatally, the chamber is triangular
 Mesiodistally, it is narrow, sometimes
resembles a flame.
 Only one pulp horn is present
 In cross-section, the chamber is ovoid in shape,
with the greater diameter labiopalatally.

Normally straight, single and symmetrical labio-lingually,
tapers to sharp apex.
However, the rare incidence of bifidity has been reported.
The root is bent distally
The apical part of the root is often abruptly curved
distally, sometimes labio-distally.

 Wider labiopalatal than mesiodistally, in the middle third, it tapers
gradually to an apical constriction.
 In cross-section, the root canal is wider in the labio-palatal direction in
cervical third, ovoid in middle third and round in the apical third.
 The apical foramen is centrally located in the anatomic apex in 14% of cases.
 The mean distance of apical foramen from the root apex ranges from 0.30 to
0.62mm.

Pulp chamber
 narrow mesiodistally.
 pulp horn under each cusp.
 Buccal pulp horn is more prominent than the palatal.
 The roof of the pulp chamber is coronal to the
cervical line.
 The floor of the pulp chamber is convex,
usually with two canal orifices, one buccal
and the other palatal and it lies deep in the
coronal third of the root below the cervical line
In cross-section, the pulp chamber is wide and ovoid in a buccopalatal dimension

has two roots in 54.6% of cases.
In 21.9%, the roots are separated, whereas in 32.7% the roots are partially fused.
43% have one root and 2.4% have 3 roots.
When two roots are present, they may diverge as much as 25% from each other.
When three roots are present, one is palatal and two are buccal which closely resemble the
configuration of a small maxillary second molar.

 In a tooth with a single canal through the length of the root, the canal is ovoid in
shape, wider bucco-palatally than mesiodistally in the cervical and middle thirds and
round in the apical third.
 When two canals are present the palatal canal is generally the larger of the two canals,
it is directly under the palatal cusp, and its orifice can be penetrated by following the
palatal wall of the pulp chamber.
 The buccal canal is directly under the buccal cusp, and its orifice can be penetrated
by following the buccal wall of the pulp chamber.

 In rare cases have shown three root canals.
 When two root canals are present, the cervical thirds are ovoid in shape, at
midroot they are almost round, and in the apical third they are round and
small.
 Maxillary 1 PM have 2 root canals at apex in 69% of cases and 26% of cases
have single root canal at apex.
 The apical foramina are centrally located in 12% of cases, and being a mean
distance of 0.55mm from the anatomic apex.
 Transverse channels between the canals are common

MAXILLARY FIRST PREMOLARS
Length of tooth
(mm)
Canals (%) Direction Curvature of roots
Single
root
Double roots
Buccal Palatal
Average
length
21.8 One canal
One foramen
9 Straight 38 28 45
Maximum
length
23.8 Two canals One
foramen
13 Distal curve 37 14 14
Minimum
length
18.8 Two canals
Two foramina
72 Mesial curve 0 0 0
Range 5 Three canals
Three foramina
6 Labial curve 15 14 28
Lingual curve 3 36 9
Bayonet curve 0 8 0

 Pulp chamber :
 Narrow mesiodistally.
 Wider buccopalatally than the maxillary first
premolar
 Two pulp horns, buccal and palatal.
 The roof of pulp chamber is coronal to the cervical
line.
 The pulp floor is deeper if two canals are present.
 If one root canal is present, the root canal orifices
will be indistinct, but if two canals are present, two
distinct orifices will be visible.
 In cross-section, the pulp chamber has a narrow,
ovoid shape.

Root:
 Maxillary second premolars have single root in
90.3% of patients.
 7.7% have 2 roots that are partially fused;
 2% have 2 well-developed roots.
 Approximately 15% of the time, 2 separate roots
are present, each with a single canal. An extremely
rare variant has 3 separate roots (Weine).
Root canals:
 One canal at apex is present in 75% of the cases.
 If two canals are present they may be separate
or converge at apex.
 Majority of canals are curved and only 9.5%
are straight.

In cross-section at three levels.
Cervical third: Canals are ovoid and narrow.
 Middle third: When one canal is present it is
ovoid, and when two canals are present they are
round.
 Apical third: Canal is round regardless of
whether one or two canals are present.
 The apical foramen is centrally located in 12% of
cases.
 Gutmann reported that the apical foramen has
been demonstrated to be on the lateral root
surface 78% of the time with a mean distance of
0.62 mm from the anatomical apex.

MAXILLARY SECOND PREMOLARS
Length of tooth (mm) Canals (%) Root curvature (%)
Average length 21 One canal
One foramen
75 Straight 9.5
Maximum
length
23 Two canals
Two foramina
24 Distal curve 27
Minimum
length
19 Three canals 1 Mesial curve 1.6
Range 4 Buccal curve 12.7
Lingual
curve
4.0
Bayonet
curve
20.6

Pulp chamber:
 Largest
 Four pulp horns: Mesiobuccal,
distobuccal,
mesiopalatal and
distopalatal.
 The arrangement of four pulp horns gives the
pulpal roof a rhomboidal shape in cross section.
 The four walls forming the roof converge toward
the floor where the lingual wall almost disappears;
the floor of the pulp chamber thus has a triangular
form in cross section.

 The Palatal orifice is the largest, round or oval in shape and
easily accessible for exploration.
 The Mesiobuccal orifice is under the mesiobuccal cusp is long
buccopalatally, and may have a depression at the palatal end
in which the orifice of a fourth canal may be present.
 The mesiobuccal orifice is located by insinuating the tip of a
long shank explorer, in a mesiobuccal - apical inclination
into the point angle created at the juncture of the buccal wall,
mesial wall, and sub pulpal floor of the pulp chamber.
 The Distobuccal orifice is located slightly distal and palatal
to the mesiobuccal orifice and is accessible from the mesial
for exploration.
 The floor of the pulp chamber is in the cervical third of the
root, and the roof is in the cervical third of the crown.

The maxillary first molar has three roots.
Mesiobuccal root:
 It is broad in the buccopalatal direction.
 The majority of the roots have a distal curve (78%), but some are straight (21%) and some are
“S” or bayonet shaped (1%).
Distobuccal root:
 It is small and is more or less round in shape.
 It is straight in 54% of cases, has a distal curve in 17% has a mesial curve in 19% and has an
“S” or bayonet shape in 10% of cases.

Palatal root:
 largest diameter and is the longest root of the maxillary first molar.
 It is straight in only 40% of cases.
 It may curve buccally (55%), mesially (4%) or distally (1%).
 The root may curve in the apical third toward the buccal.
 Such a curvature is not apparent radiographically, which may lead to perforation of the
root if the instruments are not precurved during cleaning and shaping procedures.
 Oswald in 1979 stated that this curvature is so common that it should be assumed that the
curve is present until proved otherwise.
 One may see a divergence of as much as 45º between the palatal and buccal roots.

 The maxillary first molar usually has three root canals.
 Mesiobuccal.
 Distobuccal.
 Palatal.
Mesiobuccal root canal:
 It is the narrowest of the three canals.
 Jou Yi-Tai (2004) reported that the cross sections of 90% of mesiobuccal canals were oval
or flat in mesiodistal direction, but round in apical third.
 The canal anatomy of mesiobuccal root has been described by a number of investigators and
the incidence of the mesiobuccal-2/mesiopalatal- 2 canals ranges widely. This variation may
be because of the different criteria used for evaluating the presence of this canal.
 From in vitro studies, the presence of mesiobuccal-2 canal ranges from 51.5% to 95.2%
whereas, in vivo studies, the presence of mesiobuccal-2 canal ranges from 18.6% to 77.2%..

 On average, Mesiobuccal-2 canal is located 1.8 mm away from the mesiobuccal canal in a
palatomesial direction.
 More recently, some authors have found a higher percentage of mesiobuccal canals than
these previous studies revealed.
 This could be due to their strict attention to the internal anatomy of the tooth, the change in
the access opening (creating a more heart shape form or rhomboidal shape) and the use of a
surgical microscope.
 Another suitable explanation could be the low age of patients treated. It is well known that in
normal development or in response to carious or restorative insult, the mesiobuccal canal
orifice becomes hidden by an overhanging mesial dentinal shelf.

 Hess in 1925 reported the prevalence of four root canals in maxillary permanent molar to be 53%.
 Gutmann has shown 4 canals anywhere from 46 to 72% of the time.
 However, the actual continuation of these canals into 2 separate foramina only ranges from 14 to
42%.
 Ingle (2002) reported the presence of 3 canals in 41.1%, 4 canals in 56.5% and 5 canals in 2.4% of
cases.

 The distobuccal root usually has a single root canal, which is narrow, tapering canal
sometimes flattened in a mesiodistal direction but generally cone shaped, ending in a
small, round canal in the apical third.
 The percentage of two root canals in the distobuccal root in an investigation done by
Pineda and Kuttler teeth proved to be 3.6%
 The apical foramen is centrally located in only 19% of these cases.
 The mean distance of the foramen ranging from 0.45 to 0.58mm from the root apex.
 The canal exits to a lateral surface 81% of the times.
 The possibility of fusion of distobuccal root canal with the palatal root and canal
exists with the formation of a C-shaped canal. Radiographic determination of this
variation is very difficult.

 The palatal canal is ovoid mesiodistally and taper toward the apex, where it becomes a
small, round canal.
 Frequency of curvature of palatal root canal.
 Type 1 (<10º) – 10%
 Type 2 (>10º & <20º) – 54%
 Type 3 (>20º) – 36%
This is based on Miller’s classification 1975
 Nature of curvature of palatal root canals
 Curve to the buccal – 85%.
 Curve to the buccal and to the palatal – 13%.
 Curve to the palatal only – 2%.

 The average location of the apical foramen is 0.50 - 0.64mm from the root apex.
The canal exits to a lateral surface 88.5% of the time.
 The apical foramen is centrally located in only 18% of the cases.
 Peter and Laib in 2000 investigated the thickness of the apical foramen of
maxillary molar canals which ranges in 78 to 540μm.
 Large apical canal diameter, 1mm from the root apex, was demonstrated histo-
morphologically.

 Taurodontism is a morpho-anatomical change in the shape of the tooth in which
the body of the tooth is enlarged and the roots are reduced in size
 Characterized - enlargement of the pulp chamber with the body of the tooth
enlarged at the expense of the roots and apically displaced furcation areas .
 The bifurcation or trifurcation may be only a few millimeters above the apices
of the roots.

Classification In 1928 , Shaw classified this condition as
 hypotaurodontism
 mesotaurodontism
 hypertaurodontism

MAXILLARY FIRST MOLAR
Length
of tooth
Mesi
obuc
cal
(mm)
Distobuc
cal (mm)
Palat
al
(mm)
Canal (%) Curvature of roots
Directi
on
Pala
tal
(%)
Mesi
al
(%)
Dist
al
(%)
Canals in
mesiobuccal
root
Average
length
19.9 19.4 20.6 Three 41.1 Straigh
t
40 21 54 One canal
One
foramen
41.
1
Maximu
m length
21.6 21.2 22.5 Four 56.5 Distal 1 78 17 Two canals
One
foramen
40
Minimum
length
18.2 17.6 17.6 Five 2.4 Mesial 4 0 19 Two canals
Two
foramina
18.
9
Range 3.4 3.6 3.8 Buccal 55 0 0
Lingua
l
0 0 0
Bayone
t
0 1 10

 The pulp chamber is similar to that of the maxillary first
molar except it is narrower mesiodistally.
 The roof of the pulp chamber is more rhomboidal in cross
section.
 The floor of the pulp chamber is an obtuse triangle in cross
section, and the mesiobuccal and distobuccal canals are closer
together and may appear to have a common opening, but they
are readily distinguishable from each other.
Sometimes, all three canal orifice may in a straight line.
Occasionally canal curve into the chamber at a more horizontal
angle, making it necessary to remove a “lip” of dentin so that the
canal can be entered more in a direct line with the canal axis.

 The palatal root is usually straight, but in 37% of cases it has a buccal curve.
 The mesiobuccal root usually curves distally; only 22% of these roots are
straight.
 The distal root is usually straight, but in 17% of cases it has mesial curve.
 Peikoff in 1996 reported that the ‘standard’ 3-rooted tooth is only one
anatomical variation encountered during root-canal treatment of maxillary
second molar tooth. Variations in the root anatomy of the maxillary second
molar, which include fewer or greater number of roots than the normally
described 3-root forms.

The variation of the morphology of the root canal systems which were found are:
 Variant 1 (56.9%) – 3 separate roots, mesiobuccal, distobuccal and palatal, with one
canal in each root.
 Variant 2 (22.7%) – 3 separate roots, with one canal in the distobuccal and palatal
and 2 canals in the mesiobuccal root.
 Variant 3 (9%) – Similar to variant 1 except that the mesiobuccal and distobuccal
roots join in the apical region resulting in one common apex, join to form one
common apical foramen. The palatal root is separate and has one canal.
 Variant 4 (6.9%) – 2 separate roots, a buccal and a palatal with one canal in each
root.

 Variant 5 (3.1%) – one conically shaped root with a confluence of all canals into
one main canal system.
 Variant 6 (1.4%) – 4 separate roots mesiobuccal, distobuccal and the unusual
occurrence of two separate palatal roots, a mesiopalatal and a distopalatal.
Each root has a single canal with the possible exception of the mesiobuccal
which could have 2 canals as in variant 2.
 According to Gutmann the pulp cavity spaces and radicular anatomy of this tooth are
very similar to those of the first molar with the exceptions that there is a greater
incidence of root fusion in this tooth, as well as the presence of ‘C’ – shaped canals and
canal orifices.

Length of
tooth
Mesiobuc
cal (mm)
Distobuc
cal (mm)
Palata
l
(mm)
Number
of roots
Curvature of roots
Directio
n
Palata
l
Mesia
l
Dist
al
Canals in
mesiobuccal root
Average
length
20.2 19.4 20.8 Thre
e
54 Straight 63 22 54 One canal
One
foramen
63
Maximum
length
22.2 21.3 22.6 Fuse
d
46 Distal 0 54 ? Two canals
One
foramen
13
Minimum
length
18.2 17.5 19.0 Mesial 0 0 17 Two canals
Two
foramina
24
Range 4.0 3.8 3.6 Buccal 37
Lingual 0
MAXILLARY SECOND MOLARS

 The pulp chamber of the maxillary third molar similar second molar with 3 canal
orifices.
 But it may also have an odd shaped chamber with four or five root canal orifices or a conical
chamber with only one root canal.
 Root and root canals
 The maxillary third molar has 3 well developed roots that are closely grouped.
 It may also have fused roots, one conical root, or 4 or more independent roots.
 The roots may be straight, curved or dilacerated and they may be fully or partially
developed.
 Maxillary third molars with root presented an extremely unpredictable internal anatomy
ranging from one to six canals. (Sidow 2000).

 Pulp chamber:
 smallest tooth in the arch.
 The pulp chamber is small and flat mesiodistally.
 three distinct pulp horns present in a recently erupted tooth
 Labiolingually, the pulp chamber is wide and ovoid in cross
section in the cervical third of the crown and tapers
incisally.
 Roots:
 The mandibular central incisor has 1 root, which is flat and
narrow mesiodistally but wide labiolingually.

Root canals:
 Rankine – Wilson & Henry reported a correlation between crown shape and
canal configuration, short squatty crowns had blunted roots usually with a
divided or split canal when two canals are present, the labial canal was the
straighter. The point of division for divided canals was in the cervical 3rd of the
root.
 In cross section,
 Cervical level: the canal is ovoid in labiolingual direction.
 Middle level : canal is ribbon shaped due to the flatness of the root in this
region.
 Apical level: canal is round in shape.

 The apical foramen is situated centrally in the root in 25% of cases..
 The distribution of the smallest root thickness at the 1mm level from the apical foramen was
similar regardless of the root canal thickness.
 The majority of the teeth had a thickness between 1 and 1.5 mm at the smallest part of the root
and 21.8% had a thickness of less than 1mm at the smallest part of the root.

 Pulp chamber:
 The configuration of the mandibular lateral incisor is similar
to that of the mandibular central incisor, but the lateral tooth
has larger dimensions.
 Root:
 the root of the mandibular lateral incisor is larger than that
of the mandibular central incisor.
 The majority of the roots are straight or distally or labially
curved, but the distal curve of the lateral incisor is sharper.
 It can have more than one root.

Root canals:
 The incidence of double canals and their anatomy in cross section is same as that of
central incisor (Vertucci 1985)
 Gutmann reported that in cross section, in the middle and apical third, the root may be
ovoid to figure of ‘8’ or dumbbell shaped.
 Apical foramen in the center of the radiographic apex in 20% of cases.
 The major foramen exiting a mean distance of 0.20-0.46mm from the apex.
 Presence of isthmus in mandibular (central and lateral) incisors, was present in 20% of
the teeth at the 1mm level, 30% at the 2mm level and 55% at 3mm level, as reported by
Mauger and Schindler in 1998

Length of
tooth
Central
incisors
(mm)
Lateral
incisors
(mm)
Canal Central
incisors
(%)
Lateral
incisors
(%)
Root curvature
Average
length
21.5 22.4 One canal
one
foramen
73 56.9 Straight 60%
Maximum
length
23.4 24.6 Two canals
one
foramen
26 14.7 Distal
curve
23%
Minimum
length
19.6 20.2 Two canals
two
foramens
6.5 29.4 Mesial
curve
0%
Range 3.8 4.4 Lateral
canals
5.2 13.9 Labial
curve
13%
Lingual
curve
0%
MANDIBULAR CENTRAL AND LATERAL INCISORS

 Pulp chamber:
 The mandibular cuspid resembles the maxillary
cuspid, but it is smaller in all dimensions.
 The pulp chamber is narrow mesiodistally. When
viewed labiolingually, the chamber tapers to a point
in the incisal third of the crown, but it is wide in the
cervical third.
 No distinct demarcation exists between the pulp
chamber and the root canal.
Root:
 This tooth usually has a slight labial axial inclination of
the crown.
 Although the tooth usually has a single root, it may have
2 in 2.3% of cases.
 Gutmann reported that in extreme cases of fusion during
root formation, 2 separate roots, labially and lingually
placed, can form in the mandibular canine.

Root canals:
 When one root canal is present, a labiolingual view of the root shows a canal that is broad in the
middle third and tapers to a constriction in the apical third. It is ovoid in cross section in the
cervical and middle thirds of the root and round in the apical third

Length of tooth
(mm)
Canals Lateral
canals
Root curvature
(%)
Average
length
25.2 One canal
Two canals
Two foramina
94%
6%
9.5% Straight 68
Maximum
length
27.5 Distal curve 20
Minimum
length
22.9 Mesial curve 1
Lingual
curve
0
Bayonet
curve
2

 Pulp chamber:
 Transitional tooth between anterior and posterior teeth,
 Anatomic structure it resembles both types of teeth.
 The mesiodistal width of the pulp chamber is narrow.
 Buccolingually, the pulp chamber is wide, prominent
buccal pulp horn.
 In the young tooth, one sees a small lingual pulp horn that
may disappear with age and may give the pulp chamber
an appearance similar to that of a mandibular cuspid.
 The prominent buccal cusp and the smaller lingual cusp
give the crown of the mandibular first premolar about a
30º lingual tilt.
 In cross-section, the chamber is ovoid, with the greater
diameter buccolingually. If only one canal is present, no
distinct division will be seen between the pulp chamber and
the root canal.

 Root:
 Mandibular first premolar usually has a short
conical root. Bifurcation and trifurcation of the
roots are most common anomalies in mandibular
first premolar (Saler & Gunda, 1998).
Bifurcation of roots among lower premolar,
usually occurs buccolingually, but rarely
bifurcation may occur mesiodistally also,
(Goswami & Chandra, 1997).
 Root canals:
 If one canal is present, it will be cone shaped and
simple in outline. Mesiodistally, such a root canal
is narrow; buccolingually, it is broad and tapers
toward the apical third.
 In cross section, the cervical and middle thirds are
ovoid, and the apical thirds is round

MANDIBULAR FIRST PREMOLAR
Average length 22.1 One canal
One foramen
73.5 Straight 48
Maximum
length
24.1 Two canals
One foramen
6.5 Distal curve 35
Minimum length 20.1 Two canals two
foramina
19.5 Mesial curve 0
Range 4.0 Three canals 0.5 Buccal curve 2
Lingual curve 7
Bayonet curve 7

 Pulp chamber:
 The pulp chamber of the mandibular second premolar is
similar to that of the mandibular first premolar, except the
lingual horn is more prominent under a well-developed
lingual cusp.
 Roots:
 The mandibular second premolar usually has a single root,
but on rare occasions 2 to 3 roots are present.
 The root has a greater girth and is wider buccolingually
than that of the mandibular first premolar.
 Roots canals:
 Scott Bram reported a case of mandibular second premolar
with 4 root canals.
There is no significant correlation of canal morphology with the
occlusal anatomy of the mandibular second premolar

MANDIBULAR SECOND PREMOLARS
Average length 21.4 One canal
One foramen
85.5 Straight 39
Maximum
length
23.7 Two canals
One foramen
1.5 Distal curve 40
Minimum
length
19.1 Two canals two
foramina
11.5 Mesial curve 0
Range 4.6 Three canals 0.5 Buccal curve 10
Lingual curve 3
Bayonet curve
Trifurcation curve
7
1

 Pulp chamber:
 The roof of the pulp chamber of the mandibular first
molar is often rectangular in shape.
 The mesial wall is straight, the distal wall round, and
the buccal and lingual walls coverage to meet the
mesial and distal walls and to form a rhomboidal floor.
 The roof of a pulp chamber has four pulp horns:
mesiobuccal, mesiolingual, distobuccal and
distolingual.
 These four pulp horns recede with age, with a resulting
decrease in the size of the pulp chamber.
 The roof of the pulp chamber is located in the cervical
third of the crown just above the cervical of the tooth,
and the floor is located in the cervical third of the root.

 Three distinct orifices are present in the pulpal floor; mesiobuccal, mesiolingual and
distal.
 The mesiobuccal orifice is under the mesiobuccal cusp.
 The mesiolingual orifice is located in a depression formed by the mesial and lingual
walls.
 The mesiobuccal and mesiolingual orifice may be close together under the
mesiobuccal cusp.
 The distal orifice is oval in shape.
 The multiple orifices in the distal root are usually found in the buccal and lingual
portion of the ovoid coronal root canal.

 Usually, 2 well-differentiated roots are
present in the mandibular first molar, 1
mesial and 1 distal.
 Both roots are wide and flat
buccolingually, with a depression in the
middle of the root buccolingually.
 This anatomic characteristic may be
accentuated in the mesial root.
 A third root or “Radix Entomolaris” (RE) is
found either distally or mesially in Eurasian
and Indian populations in the less than 5% of
cases

Length
of tooth
Mesial
(mm)
Distal
(mm)
Roots (%) Canals Curvature of roots
Direction Distal Direction Mesial Distal
Average
length
20.9 20.9 Two 97.8 Two 6.7 Two
canals
One
foramen
40.5 One canal 71.1 Straight 16 74
Maximum
length
22.7 22.6 Three 2.2 Three 64.4 Two
canals
Two
foramina
59.5 Two canals 28.9 Distal 84 21
Minimum
length
19.1 19.2 Four 28.9 Two canal
One
foramen
61.5 Mesial 0 5
Range 3.6 3.4 Two canals 38.5 Buccal 0 0
Two
foramina
Lingual 0 0
MANDIBULAR FIRST MOLARS

 Pulp chamber:
 The pulp chamber of the mandibular second
molar is smaller than that of the mandibular first
molar, and root canal orifices are smaller and
closer together
 Roots:
 The majority of the mandibular second molar has
2 roots 71%,
 but teeth with one root 27% and
 3 roots 2% are also seen.
 Root canals:
 3 root canals are usually present; the most
frequent variation is the presence of only 2 canals.
 All 3 canals are small and ovoid in the cervical and
middle 3rd and round in the apical 3rd.

Length of tooth Mesial
(mm)
Distal
(mm)
Canals (%) Curvature of roots (%)
Mesial Distal Direction Single
root
Double root
Mesial Distal
Average length 20.9 20.8 One canal one
foramen
13 92 Straight
Distal
53
26
27
61
58
18
Maximum length 22.6 22.6 Two canals
one foramen
49 5 Mesial
Buccal
0
0
0
4
10
4
Minimum length 19.2 19.0 Two canals
two foramina
38 3 Lingual
Bayonet
2
19
0
7
0
6
Range 3.4 3.6
MANDIBULAR SECOND MOLARS

 Pulp chamber:
 The pulp chamber of the mandibular third molar anatomically
resembles the pulp chamber of the mandibular first and second
molars.
 It is large and possesses many anomalous configuration such as “C-
shaped” root canal orifices.

Roots and Root canals:
 The mandibular third molar usually has two roots and two canals,
but occasionally one root and one canal or 3 roots and 3 canals can
also be seen. The root canals are generally large and short.
 Sidow and West in 2000 reported that the mandibular third molar
17% had one root,
 77% had two roots,
 5% had three roots.
 The number of canals ranged from 1 to 3 with one root, 2 to 6 with 2
roots, 3 to 5 with 3 roots.4 to 5 in teeth with 4 roots,.C-shaped were
identified with one or 2 roots.
 The anatomy of a mandibular third molar cannot be predicted on
the basis of the number of roots.

 Radiographic examination,
 Placing files in the canals to determine the canal configuration
 Root sectioning
 Making polyester resin cast replicas of the pulp space
 Staining and clearing techniques,
 Direct observation with microscope,
 Sectioning and macroscopic observation,
 Stereo microscope,
 Spiral computed tomography,
 Cone beam computed tomography

 Vertucci used the clearing technique to study the root canal morphology of
extracted mandibular anterior teeth. It has been reported that fine details of the
root canal system can be visualized by staining and clearing.
 This technique also makes canal negotiation with instruments unnecessary,
thereby maintaining the original form and relation of canals, and provides a
three-dimensional view of root canal.
 The process of changing the tooth into a transparent object involves many
physical and chemical changes.
 The inorganic constituents of the tooth are first dissolved by decalcification,
and further water, air, and lipid components are removed by dehydration and by
subsequent immersion in the clearing agents

CONCLUSION
THE ROOT APEX IS
MORPHOLOGICALLY THE MOST
COMPLEX REGION,
THERAPEUTICALLY A CHALLENGING
ZONE AND PROGNOSTICALLY AN
IMPORTANT PART BUT
UNFORTUNATELY MOST OBSCURE
AND UNCLEAR RADIOGRAPHICALLY.
SO ENDODONTIST SHOULD HAVE
DETAILED KNOWLEDGE OF THE
ANATOMIC VARIATIONS AND
MECHANICAL CHALLENGES
INVOLVED IN THE TREATMENT OF
APICAL THIRD OF ROOT FOR
EFFECTIVE AND EFFICIENT
MANAGEMENT DURING ENDODONTIC

Internal anatomy of tooth

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