primary root canal anatomy

8/17/2019 Primary Root Canal Anatomy

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Primary Root Canal anatomy 4

Primary Root Canal Anatomy

A sound knowledge of the size, morphology and variation of the root canals of a primary

tooth is useful in visualizing the pulp cavity during treatment. Before starting endodontic

therapy, the clinician should understand the morphological changes that continually occur in

primary teeth and be familiar with the basic differences in the anatomy of primary and permanent

teeth .The root canals of anterior teeth are relatively simple, whereas in posterior teeth due to

anastomosis and ramifications, it is more complex which makes debridement difficult. Continued

deposition of secondary dentin following resorption of teeth produces variations in the root canal

anatomy of primary teeth.

!orphological differences exist between the primary and the permanent dentitions, both

in size as well as in their external and internal design. "# The pulp cavities in primary teeth are

relatively larger due to thin dentinal walls .$o clear demarcation is present between the pulp

chamber and the root canals. The pulp chamber of incisors is wedge shaped and the root canals

are wide labiolingually with the apical third perforated by many accessory canals. The pulp horns

of primary molars are more pointed especially the mesial horns than as suggested by the cusp

anatomy. The pulp canals are more slender and tapering and are longer in proportion to the

crown, than the corresponding permanent dentition . "#

The roots of the primary anterior teeth are narrower mesiodistally and have a narrow

constricted cervix and prominent enamel ridges."#

The root canals of the canines are large with

many accessory canals. %oot furcation in molars lies very close to the level of cementoenamel

&unction increasing the risk of lateral perforation . $umerous studies have been performed to

determine presence of accessory canals in primary molar furcations. !oss '()*+ demonstrated


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that infected primary molar teeth furcations have an increase in the porosity of the dentin and

cementum. -n addition, accessory canals were not always present in all primary molars and

should not be considered as the only pathway for interradicular radiolucency formation. ""

Maxillary Primary Incisors

The maxillary primary incisors have similar morphology with mild variations. The root is

single and conical in shape, fairly regular and ending in a conical form. The pulp chamber

closely follows its crown outlines. The pulp chamber has three pro&ections on its incisal border.

The chamber tapers cervically in its mesiodistal diameter, but it is widest at the cervical ridge

labiolingually. The single pulp canal shows no demarcation and tapers evenly until it ends at the

apical foramen. The maxillary laterals are /uite similar in contour to the maxillary central

incisors except that they are not as wide mesiodistally. "# The maxillary primary incisors are (*

mm long, while the laterals are slightly shorter. 0tudies by 0alama et al have shown that

primary central incisor root canals have a consistent length of (* to ( mm. Their cervicoincisal

lengths are e/ual to that of the central incisors and their labial surfaces are more flattened. The

root of the lateral incisor is thin and tapering. There is a slight demarcation between the pulp

chamber and the canal, especially on the labial and lingual aspects. "#

Mandibular Primary Incisors

They are narrow and are the smallest incisors in the oral cavity. The root of the central

incisor is only slightly flattened on its mesial and distal aspects and tapers towards the apex. The

lateral incisor is slightly broader and longer than the central incisor and has a longer root. The

centrals are (#mm, whereas the laterals are (+ mm. The 1ulp cavity conforms to the crown

outline. The pulp chamber is widest mesiodistally at the roof of the chamber. 2abiolingually,


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the chamber is widest at the cingulum or cervical line. The pulp canal is oval in appearance and

tapers as it approaches the apex. There is a definite demarcation between the pulp chamber and

the canal in the central incisor, which is absent in the laterals. "" The presence of two canals has

been reported in less than (34 of the cases and occasionally accessory canals are seen. (*

Maxillary Primary Cuspid

They are larger than the central and lateral incisors. The roots are long, thick in diameter

and slightly flattened on its mesial and distal surfaces. The root is tapering and the apex is

rounded. The pulp cavity conforms to the general outline of the tooth and the central pulp horn is

the largest. There is very little demarcation between the pulp chamber and the canal. The canal

tapers towards the apex. "# !axillary canines are the longest primary teeth () mm in length. As

the root apices undergo resorption because of the erupting successors, the roots are fre/uently

shorter in older children . )

Mandibular Primary Cuspid

The mandibular canines are ( mm in length . ) They have a similar contour as the

maxillary cuspid, but are not as bulbous labiolingually or as broad mesiodistally. A single root is

present and the labial surface is broader than the lingual surface. The root tapers to a pointed

apex. The pulp cavity conforms to the general surface contour of the tooth. The pulp chamber

follows the external contour of the tooth, mesiostally and labiolingually e/ual in diameter. There

is no demarcation between the pulp chamber and canal. The root canal ends with a marked

constriction in the apical area. ."#

Maxillary First Primary Molar


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This tooth resembles its successor more than any other primary tooth both in diameter as

well as in shape. There are two to four canals that correspond to the exterior root form with much

variation. The root is formed of three well diverged prongs, a mesiobuccal, a distobuccal and

palatal branch. The palatal root is round and diverges in a lingual direction and often larger than

the two facial roots. The distobuccal root is the shortest. 5usion of the palatal and distofacial

roots occurs in approximately one third of all primary molars. Bifurcation of the mesiofacial root

into two canals is common in approximately +4of the first primary molars. (+

The pulp chamber consists of three or four pulpal horns which are more sharply pointed.

The !esiobuccal pulp horn is the largest and occupies the prominent most portion of the

chamber. The mesiolingual pulp horn is the second largest and is sharp and angular. The

distobuccal horn is the smallest. The pulp horns may be as close as "mm from the enamel surface

and chances of pulpal exposure are high during cavity preparation. ) The occlusal view of the

pulp chamber resembles a triangle with rounded corners. The pulp canals extend from the floor

of the chamber near the mesiobuccal and distobuccal line angles. "#

Mandibular First Primary molar

-t is morphologically uni/ue in that the outline form differs from any other primary or

permanent teeth. The overdeveloped mesial marginal ridge is the characteristic feature and it

resembles a fifth cusp. The outline of the tooth is in a rhomboidal shape. The roots are divided

into " prongs namely a mesial and a distal root. The roots are thin and flare out as they approach

the apex to allow space for the developing tooth bud. The pulp chamber is rhomboidal in an

occlusal view and closely follows the contour of the surface of the crown. 5our pulpal horns are

present. The mesiobuccal horn is the largest, rounded, connects with the mesiolingual pulp horn


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and is an area prone to mechanical exposure. The distobuccal horn is second largest but lesser in

height. The distolingual pulp horn is the smallest and is more pointed than the buccal horns.

Three pulp canals are present. The mesiobuccal and mesiolingual canal are confluent. They

separate to form a buccal and lingual canal which gradually taper to the apical foramen. The

distal pulp canal pro&ects in ribbon fashion from the floor in a distal aspect. This canal is wide

buccolingually, but is constricted at the centre. "# -t is reported that approximately +4 of the

mesial roots contain two canals and only "+4 percent of the distal roots contain more than one

canal. (*

Maxillary Second Primary Molar

-t is a four cusped tooth, although a fifth cusp is present on the mesiolingual aspect of it.

The roots are divided into three prongs, a mesiobuccal, distobuccal and a lingual root .The roots

are thinner and flare more as they reach the apex and they resemble the maxillary permanent

molar. "# The bifurcation of the mesiofacial root with two distinct canals is seen in 6+4 to )3 4

of the maxillary second primary molars. (* The pulp chamber conforms to the general outline of

the teeth and three pulp canals are present. 7sually four pulpal horns are present8 sometimes a

fifth horn from the lingual aspect of the mesiolingual horn may be present. The mesiobuccal pulp

horn is the largest and is pointed. The mesiolingual horn is second largest followed by the

distobuccal. The distolingual pulp horn is the smallest. The three pulp canals leave the chamber

at the mesiobuccal and distobuccal corners from the lingual area. "#

Mandibular Second Primary Molar


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The A9delta fibers are lightly myelinated, have a faster conduction velocity than C fibers,

and are believed to transmit a sharp or pricking sensation. A9delta fibers respond primarily to

noxious mechanical stimuli rather than to chemical or thermal stimuli. :ther A9delta fibers may

be polymodal 'responding to mechanical, chemical, and thermal stimuli or respond only to

cold;mechanical or hot;mechanical noxious stimuli. -n the tooth pulp, A9delta fibers traverse the

odontoblastic layer and terminate in the dentinal tubules. (*

Because of their location and their sensitivity to mechanical stimulation, A9delta fibers

are believed to respond to stimuli that result in movement of fluid within the dentinal tubules

'e.g., osmotic, mechanical probing or thermal stimuli applied to the external surface of thetooth .Consistent with the hypothesized mechanism of dentinal pain is the fact that the stimuli

that cause dentinal fluid movement result in a sharp pain associated with A9delta fiber activation.


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primarily by afferent fibers conducting nociceptive information such as that carried by A9delta

and C fibers. (*

primary root canal anatomy

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