CHAPTER 7 (from summer endo-basic)

root canal system

follows the external contour of the tooth

the entire space in the dentin housing the pulp

root canal anatomy

essential for endodontic success

complexity is the norm, not the exception

as critical as diagnosis & treatment planning

a simple tapering canal with a single foramen is rare

all groups of teeth had at least one accessory foramen

canal morphology affects:

• shaping & cleaning outcomes

• more than the choice of instrumentation technique

root dimensions can be modified by:

aging

occlusion

disease (pathosis)

formation of secondary/tertiary dentin & cementum

pulp chamber

in the anatomic crown

root canal(s)

in the anatomic root

other key structures of root canal system

pulp horns

canal orifices

apical deltas & apical foramina

accessory, lateral, and furcation canals

root canal curves

faciolingually, which can be challenging to detect on standard x-rays

types of curves

gradual

sharp bends

complex shapes (double s-curves)

canal variation

the number of canals usually matches the number of roots, but some roots (like oval-shaped ones) can have multiple canals

accessory canals

form during root development

minute canals that extend in a horizontal, vertical, or lateral directions from the pulp to the periodontium

contents of accessory canals

connective tissue & vessel

pathological significance of accessory canals

allow irritants to pass from pulp to periodontium, potentially leading to periodontal disease or other issues

weine’s classification type I

(1)

single canal, single exit

weine’s classification type II

(2-1)

two separate canals, merging to one exit

weine’s classification type III

(2)

two canals throughout, two separate exits

weine’s classification type IV

(1-2)

one single canal, splitting into two exits

vertucci’s classification

an extended categorization

based on studies of cleared teeth with dye to reveal internal canal pathways

further strengthens the fact that root canal anatomy can be highly variable and complex

MX 2nd premolar

had the largest accessory foramina

only tooth that showed all eight possible configurations

most complicated apical morphologic structure — which might be a possible reason why root canal therapy may fail in premolar teeth

vertucci’s classification type I

(1-1)

a single canal extends from the pulp chamber to the 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 one canal

vertucci’s classification type IV

(2-2)

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

vertucci’s classification type V

(1-2)

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

vertucci’s vlassification type VI

(2-1-2)

two separate canals leave the pulp chamber, merge in the body of the root, and redivide short of the apex to exit 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 redivides into two distinct canals short of the apex

vertucci’s vlassification type VIII

(3-3)

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

anatomy of the apical root

apical foramen

apical constriction

cementodentinal junction

apical constriction

aka: minor foramen, minor diameter, or minor apical diameter

0.5 - 1.5 mm coronal to the apical foramen (major apical diameter)

reference point and apical termination for shaping, cleaning, and obturation of the root canal

apical foramen

aka: major foramen, major diameter, or major apical diameter

does not normally exit at the anatomic apex but rather is offset 0.5-3mm

the “circumference or rounded edge” that differentiates the termination of the cemental canal from the exterior surface of the root”

cementodentinal junction (CDJ)

1mm from the apical foramen

point in the canal where cementum meets dentin

where pulp tissue ends and periodontal tissues begin

generally not in the same area as the apical constriction

root apex

contains a variety of anatomic structures and tissue remnants, thus, has differing morphology

1mm from the apex

termination points when no bone or root resorption occurred

1.5 mm from the apex

termination points when only bone resorption occurred

2mm from the apex

termination points when both bone and root resorption occurred

radiographic apex

a more reliable reference point locating the apical constriction and apical foramen since it is difficult clinically

within 3 mm

root canal procedures are recommended to terminate at or ___ from the radiographic apex, depending on the pulpal diagnosis

apical pulp stump

prevents extrusion of irritating filling materials into the periradicular tissues

electronic apex locators

are reliable instruments that can help determine the working length of the root canal

isthmus

can function as bacterial reservoirs

contains pulp or pulpally derived tissue

any root with two or more canals may have an isthmus

a narrow, ribbon-shaped communication between two root canals

isthmus classifications type I

an incomplete isthmus

it is a faint communication between two canals

isthmus classifications type II

characterized by two canals with a definite connection between them (complete isthmus)

isthmus classifications type III

a very short, complete isthmus between two canals

isthmus classifications type IV

a complete or incomplete isthmus between three or more canals

isthmus classifications type V

marked by two or three canal openings without visible connections