LAB: ROOT CANAL ANATOMY

from lab manual

parts of the root canal system

canal bifurcation

(splitting into two canals)

indicates when a root canal disappears or becomes indistinct partway down the root

apical constriction

the narrowest part of the canal

→ root canal gradually narrows as it approaches the apex

1.0 – 1.5 mm from the root apex

diameter of apical constriction

shape of the narrowest area

round

oval

serrated

apical foramen

often exits at an angle to the main canal

is not usually in a straight line with the main canal

forms after the narrowest point which widens again

0-3 mm from the root apex

diameter where apical foramen is located

Frank Weine (1982)

he classified the basic classification of root canal morphology

Type 1

Single canal from pulp chamber to apex

1

Type 2

(2-1)

Two separate canals leaving the pulp chamber but merging short of the apex to form only one canal

type 3

(2)

two separate canals leaving the pulp chamber and exiting from the root in separate apical foramina

Type 4

(1-2)

one canal leaving the pulp chamber but dividing short of the apex into two separate canals with separate apical foramina

lateral canals

present in about 50% of permanent teeth

branch off from the main root canal at right angles

• can be:

  • blind-ending sacs

  • or open channels that reach the root surface (most common)

• can occur:

  • anywhere along the root

• size varies:

  • from very small (microns)

  • sometimes as large as the main canal

relevance of lateral canals in endodontics

• act as communication pathways between:

  • main canal (inside the tooth)

  • periodontal tissues (around the tooth)

• this means:

  • pulp infection → periodontal damage

  • periodontal disease → pulp irritation or infection

irritation or secondary dentin formation

causes the root canal system to gradually reduce in size

• factors that hasten the process::

  • caries (tooth decay)

  • trauma

  • excessive wear

  • dental procedures (preoperative work)

younger patients → larger access cavities

older patients → smaller access cavities needed due to narrower canals

canal obliteration process

canals never fully sclerose (block completely)

• hard tissue deposition occurs:

  1. first fills the pulp chamber

  2. then moves into the coronal part of the canal

• changes in pulp tissue

  • becomes more fibrous

  • less vascular (reduced blood supply)

  • in some cases, pulp dies

  • apical portion of the canal often remains open (patent)

Vertucci

he classified the complex of root canal morphology

Vertucci’s Classification Type I

(1-1)

A single canal extends from pulp chamber to apex

Vertucci’s Classification Type II

(2-1)

Two separate canals leave the pulp chamber and join short of the apex to form one canal

Vertucci’s classification type III

(1-2-1)

one canal leaves the pulp chamber and divides into two in the root: the two then merge to exit as single canal

Vertucci’s Classification Type IV

(2-2)

Two separate, distinct canals extend from the pulp chamber to apex

Vertucci’s Classification Type V

(1-2)

one canal leaves the pulp chamber and divides short of apex into two separate, distinct canals with separate apical foramina

Vertucci’s Classification Type VI

(2-1-2)

two separate canals leave the pulp chamber; merge in body of the root, and redivide short of the apex and exits as two distinct canals

Vertucci’s Classification Type VII

(1-2-1-2)

one canal leaves the pulp chamber; divides and then rejoins in the body of the root, and finally divides into two distinct canals short of the apex

Vertucci’s Classification Type VIII

(3-3)

three separate distinct canals extend from the pulp chamber to apex

canal anatomy of mx incisors

• inclination: labial

• root shape:

  • central: usually straight [fig. 7]

  • lateral: often has a distal curve at apex [fig. 8]

• canal cross-section:

  • oval in coronal and middle thirds

  • becomes round in apical third

canal anatomy of mx canine

apical portion may be thin → only small instruments can be used to avoid perforation

• inclination: Labial [fig. 10]

• root shape: Straight or slightly distal curve near apex

• canal shape:

  • middle third: broad labio-palatal (forms a bulge)

  • apical third: round [fig. 11]

canal anatomy of mx 1st premolar

• roots:

  • 62% have 2 roots

  • 38% have 1 root

  • rarely, 3 roots

• canals:

  • majority (85%) have 2 canals

  • pulp chamber floor extends into roots, wide bucco-palatal

• special cases:

  • 3-rooted premolars are hard to detect radiographically

  • can have 3 canal orifices: 2 buccal, 1 palatal

canal anatomy of mx 2nd premolar

• roots: usually 1

  • 2 roots in 15%

• canals:

  • usually 1, broad bucco-palatal

  • 2 canals occur in 25%

note: buccopalatal extent may be visible only in oblique radiographs

canal anatomy of mx 1st molar

roots: 3 (2 buccal, 1 palatal)

• distobuccal root: straight, round cross-section

• mesiobuccal root:

  • curved distally, broad bucco-lingual

  • usually has a groove mesially and distally

  • 2 canals in 60% of cases

    • if only one canal → broad bucco-lingual, narrow mesio-distal

  • main mesiobuccal canal → larger, buccally positioned

• palatal root:

  • curves buccally, oval mesio-distally

  • opens under mesiopalatal cusp

canal anatomy of mx 2nd molar

similar to first molar

• pulp chamber: flattened mesio-distally (reflects crown shape)

• mesiobuccal root: lower incidence of second canal than first molar

canal anatomy of mn incisors

• canals:

  • 40% have 2 canals

  • configurations:

    • type 1 → 60% [fig. 30]

    • type 2 → 35% [fig. 31]

    • type 3 → 5%

• shape:

  • single canal: broad bucco-lingually, narrow mesio-distally [fig. 32-33]

  • 2 canals: rounder in cross-section

  • ovoid throughout root length [fig. 35]

• root features:

  • shallow vertical grooves on mesial and distal surfaces

  • narrow root width → higher risk of lateral perforation during enlargement

canal anatomy of mn canines

• roots: usually 1; rarely 2 [fig. 36]

• canal configurations: type 1, 2, or 3

• length: longest mandibular tooth, variable length

• canals: 2 canals in 18% of cases [fig. 37]

canal anatomy of mn 1st premolar

• canals:

  • usually 1

  • 2 canals in 27% of cases, rarely 3

  • when two canals present → lingual canal is second

• shape: wide bucco-lingually

• configuration: mainly type 4

canal anatomy of mn 2nd premolar

high incidence of lateral canals

• canals:

  • usually 1 (type 1 most common)

  • wide bucco-lingually

  • apical portion often curves distally

canal anatomy of mn 1st molar

• roots: usually 2 (mesial and distal)

• mesial root:

  • 2 canals in 87% [fig. 42]

    • about half merge at apical foramen

  • canals curve mesially then gradually distal

  • mesiobuccal canal more curved than mesiolingual

  • canals may communicate along their length [fig. 43]

  • grooves on midline wall increase perforation risk [fig. 44]

• distal root:

  • canal centrally located, slightly behind middle bucco-lingual fissure [fig. 45-47]

• single canal cases: Broad bucco-lingually [fig. 48]

• canal openings:

  • mesiobuccal → beneath mesiobuccal cusp

  • mesiolingual → nearer midline

canal anatomy of mn 2nd molar

similar to first molar

• distal root: lower incidence of two canals

• roots: tend to be closer together [fig. 51-52]

• mesial root: usually 2 canals, occasionally 1 (broad bucco-lingually)

• rare variations:

  • single root with single canal [fig. 53]

  • c-shaped canals → distal canal extends mesially, sometimes including mesiobuccal and mesiolingual canals [fig. 44-45]

  • difficult to detect on preoperative radiographs