PRESENTED BYDR SNEHA RATNANI

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 negotiate and 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.

DENTINAL MAP

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.

II

III

ACCORDING TO GROSSMAN

Vertuccis’s Classification

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 resorptionnot 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

Range 4.6 Labial curve 4

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

Range 5.8 Labial curve 13

Lingual curve 7

Bayonet and

gradual curve

7

One Canal

96.5%

Two orMore Canals

3.5%

One Canalat Apex

98.8%

Two orMore Canalsat 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 firstpremolar

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

Range 4.6 Labial curve 7

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

Length of tooth (mm) Canals (%) Root curvature (%)

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

Length of tooth (mm) Canals (%) Root curvature (%)

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

THERAPY.