Tooth Morphology and Access Openings

RELATIONSHIP OF TOOTH MORPHOLOGYAND ACCESS CAVITY PREPARATION

is the first indication of the assumed and is the first key to the root position and root canal system.

A investigation of the sulcus, coronal clefts, restorations, tooth angulation,cusp position, occlusion.

MANDATORY BEFORE ACCESS

The visual The assumed

ACCESS PREPARATIONS

Palpation of buccal or labial soft tissue will help determine root

THE CORONAL ANATOMY

Maxillary Length(mm) Mandibular Length(mm)

CENTRAL INCISORAVERAGEGREATESTLEAST

LATERAL INCISORAVERAGEGREATESTLEAST

CANINEAVERAGEGREATESTLEAST

22.527.018.0

22.026.017.0

26.532.020.0

CENTRAL INCISORAVERAGEGREATESTLEAST

LATERAL INCISORAVERAGEGREATESTLEAST

CANINEAVERAGEGREATESTLEAST

20.724.016.0

21.127.018.0 25.632.518.0

Tooth length determination

FIRST PREMOLARAVERAGEGREATESTLEAST

SECOND PREMOLARAVERAGEGREATESTLEAST

SECOND PREMOLARAVERAGEGREATESTLEAST

FIRST PREMOLARAVERAGEGREATESTLEAST

SECOND PREMOLARAVERAGEGREATESTLEAST

20.622.517.0

21.527.016.0

21.626.018.0

22.326.018.0

21.527.016.0

SECOND PREMOLARAVERAGEGREATESTLEAST

22.326.018.0

Maxillary Length(mm) Mandibular Length(mm)

FIRST MOLARAVERAGEGREATESTLEAST

SECOND MOLARAVERAGEGREATEST1 .EAST

THIRD MOLARAVERAGEGREATESTLEAST

20.824.017 0

20.024.016.0

17.122.014.0

FIRST MOLARAVERAGEGREATESTLEAST

SECOND MOLARAVERAGEGREATESTLEAST

THIRD MOLARAVERAGEGREATESTLEAST

21.024.018.0

19.822.018.0

18.520.016.0

ACCESS CAVITY PREPARATION IN INCISORS

If the incisal edge is intact, it is almost impossible to perforate lingually.

INCISORS, PARTICULARLY MANDIBULAR INCISORS

are often weakened coronally by excessive removal of tooth structure

THE MESIODISTAL WIDTH OF THE PULP CHAMBER

is often narrower than the bur used to make the initial access.

LABIAL PERFORATIONS (cervical or root surface) are common, especially with calcifications.

IncorrectCorrect

A, Sweeping motion in a slightly downward lingualto- labial direction (arrows), until the chamber is engaged, to obtain the best access to the lingual canal.

B, Incorrect approach:directing the end-cutting bur in a straight lingual-tolabial direction. Mutilation of tooth structure and perforation will be the result in this small and narrow incisor.

METHODS OF DETERMINING ANATOMIC DETAIL1. When the radiograph shows that the canal suddenly

stops in the radicular region the assumption is that it has bifurcated (or trifurcatcd) into much finer diameters.

2. To confirm this division, a second radiograph is exposed from a mesial angulation of 10 to 30 degrees.

3. The resultant film will show either more roots or multiple vertical lines indicating the peripherics of additional root surfaces

A radiograph also reveals many clues to anatomic "aberrations":lateral radiolucencies indicating the presence of lateral or accessory canals an abrupt ending of a large canal signifying a bifurcation aknoblikeimage indicating an apex that curves toward or away from the beam of the x-ray machine multiple vertical lines, as shown in this curved mesial root , indicating the possibility of a thin root, which may be hourglass shaped in cross section and susceptible to perforation.

The endodontic pathfinder inserted into the orifice openings will reveal the direction that the canals take in leaving the main chamber

4. Digital perception with a hand instrument can identify curvatures, obstruction, root division, and additional canal orifices

5. Fiberoptic illumination can reveal calcifications, orifice location, and fractures

6. Knowledge of root canal anatomy will prompt the clinician always to search for additional canal orifices where they are known to occur—for instance, the usual location of a fourth canal in the maxillary first permanent molar between the mesiobuccal and palatal canals along the developmental groove

7. Further knowledge of root formation can save the clinician difficulties with instrumentation—for example, in what appears radiographically to be a normal palatal root of a maxillary first permanent molar but is actually a root with a sharp apical curvature toward the buccal

8. Ethnic characteristics as well as other physical differences can be manifested in tooth morphology, for example, the common occurrence of four canals in Asian peoples

Average time of eruption: 7 to 8 yearsAverage age of calcification: 10 yearsAverage length: 22.5 mm

Double lateral canals

Curved accessory canal with straight lateral canal intersecting .

Parallel accessory canal to main canal with simple lateral canal.

Average time of eruption: 8 to 9 yearsAverage age of calcification: 11 yearsAverage length: 22.0 mm

Maxillary Lateral Incisor

Average time of eruption: 10 to 12 yearsAverage age of calcification: 13 to 15 yearsAverage length: 26.5 mm

Maxillary Canine

Canine with multiple accessory foramina.

Maxillary canine with lateral canal dividing into two additional canals.

Average time of eruption: 10 to 11 yearsAverage age of calcification: 12 to 13 yearsAverage length: 20.6 mm

Permanent Maxillary First Premolar

Buccolingual Section -The majority of the max. 1st premolar have 2

well developed roots on a common root trunk or. The majority of max. 2nd PM have 2 root canals. A small percentage have 3 roots that may be

undetectable radiographically. If one root is present, 2 root canals are also seen,

that might join & open in one apical foramen or 2 apical foramina.

-The level of buccal pulp horn is more occlusal than the lingual pulp horn.

- The pulp chamber floor is below cervical level - Root canals often exit at root tip, or slightly

labial or lingual.

Mesiodistal Section

Pulp horns appear blunted. Pulp chamber can’t be diffrentiated

from root canal. Pulp cavity tapers slightly from occlusal

aspect to to apical foramen. Apical foramen often exit at tip of root,

or some at mesial or distal sides.

Cervical Cross Section

Shows the characteristic kidney shaped outline due to the M developmental groove.

Pulp cavity may show constriction adjacent to developmental groove, or may follow outline of root surface.

Some roots will show 2 separate root canals or 3 in case of 3 rooted root canals.

Three canals inmaxillary first bicuspid.

Two canals fusingand rcdividing.

Lateral bony lesionassociated with filled lateral canal

Average time of eruption: 10 to 12 yearsAverage age of calcification: 12 to 14 yearsAverage length: 21.5 mm

Maxillary Second Premolar

Permanent Maxillary Second Premolar

Buccoilingual Section

Most max. 2nd PM have one root & one root canal.

2 roots & 2 root canals may be seen. pulp horns & root canals are very broad in teeth

with single canals. pulp horns may be well developed or blunt.

In apical half or third , root canal may narrow abruptly.

Some teeth process dentinal islands or bifurcations at the apical third of the root, the clinician must treat this situation as 2 roots.

The apical foramen may exit at the root tip, at buccal or lingual aspects of the root, or at both buccal & lingual aspects.

Mesiodistal Section

Pulp horns are blunt, Pulp cavity tapers slightly from occlusal aspect to apex.

Apical foramen may exit at root tip or anywhere near it.

Cervical Cross Section

Is oval or kidney shaped. Pulp cavity is either centered in the

root, may be constricted in the middle of the canal space, elliptical or entire seperation.

Multiple foramina.Single canal dividinginto two canals.

Single canal splittinginto three canals.

Average time of eruption: 6 to 7 yearsAverage age of calcification: 9 to 10 yearsAverage length: 20.8 mm

Maxillary First Molar

Fourth canal in mesiobuccalroot; loops and accessory canals

Second canals in both mesiobuccal and lingual canals.

Sharp curvature and multiple accessory canals in palatal root (contrast to silver cones in second molar).

Maxillary Second Molar

Average time of eruption: 11 to 13 yearsAverage age of calcification: 14 to 16 yearsAverage length: 20.0 mm

Four-rooted maxillary second molar

Severely curved mesiobuccal root with right

angle curve in distobuccal root.

Maxillary Third Molar

Average time of eruption: 17 to 22 yearsAverage age of calcification: 18 to 25 yearsAverage length: 17.0 mm

Showing canals fuses into single canal. (Note multipleaccessories in second molar.)

Distal bridge abutmentwith major accessory canal.

Average time of eruption: 6 to 8 yearsAverage age of calcification: 9 to 10 yearsAverage length: 20.7 mm

Mandibular Central and Lateral Incisors

Two-rooted mandibular lateral incisor. Mandibular lateral and central, both with two canals.

Mandibular Canine

Average time of eruption: 9 to 10 yearsAverage age of calcification: 13 yearsAverage length: 25.6 mm

Two-rooted mandibular canine

Sharp distal curveture at apex

Two lateral canals. The incisal canal is above the crest of bone andwas probably responsible for pocket depth.

Twincanaled mandibular canine with significant lateral canals feeding a periodontal defect

Average time of eruption; 10 to 12 yearsAverage age of calcification: 12 to 13 yearsAverage length: 21.6 mm

Permanent Mandibular First Premolar

Buccolingual Section

Pulp cavity looks like mand canine. Majority have one canal, but may find 2-

3 canals. Buccal pulp horn is prominent, while

lingual pulp horn may be either small or absent.

Pulp chamber is wide & pulp cavity may either taper gently to apex or abruptly constricts in apical region.

Mesiodistal Section

Pulp horn is prominent Pulp chamber & root canal taper gently

to apex. Apical foramen either exit from root tip,

or around it.

Cervical Cross Section

Outline form of root may be either oval, rectangular or triangular.

Pulp cavity may be round, elliptical, or triangular.

If bi or trifurcation exists, 2-3 round canals can be seen.

Mandibular 2nd premolar Buccolingual Section Pulp cavities are larger at crown &

occlusal portion of root canal 2or 3 pulp horns can be seen Apical foramen may exit at apex,at

buccal or lingual aspect of root tip.

Mesiodistal Section

Similar to mand 1st. Usually has one root & one root

canal that may be curved in a distal direction.

Cervical Cross Section

Outline form of root may be either oval, rectangular or triangular.

Pulp cavity may be round, elliptical, or triangular.

Three-rooted mandibular first bicuspid

Single canal dividing at apex.

Average time of eruption: 11 to 12 yearsAverage age of calcification: 13 to 14 yearsAverage length: 22.3 mm