21 July 2017
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Endodontic Access Cavities Cheat Sheet

Endodontic Access Cavities Cheat Sheet

 
We all struggle with access cavities! The stakes are high, the other treatment option is usually to extract the tooth, so if you get it wrong then that will be the end of the tooth! Tutors keep telling us that knowledge of the anatomy is paramount if you want anything to go remotely right.

That said, there is a huge amount of literature out there looking at the number of root canals in each tooth. There’s still dispute about how often you see a MB2 canal, some authors are suggesting 90%! (Your average GDP says it doesn’t exist, hmm…). These two tables are adapted from two textbooks, one of which will be found on most dental schools reading lists, so hopefully the information isn’t too far wrong!

Maxillary Teeth Average Tooth Length (mm) Number of Roots Number of Canals Features
1 23 1 1 Oval shape access cavity starting at cingulum
Wider buccopalatally
Ovoid shape coronal, round at apex
2 22 1 1 Similar to central except:
More rounded coronally
Usually have 2 pulp horns concurrent with mammalons
Palatal curve present in apical third
3 26 1 1 Triangular access with apex to incisor tip
Oval coronally, round at apex
Wider labiopalatally
4 21 2 1 (5%)
2 (90%)
3 (5%)
Buccopalatal oval shape access cavity
Canals directly under buccal and palatal cusp tips.
Usually straight and divergent
If 3 canals found, MB DB and P
5 21 1 1 (75%)
2 (25%)
Buccopalatal oval shape access cavity
1 canal usually centred and oval in shape
If 2 canals may merge apically
6 22 3 3 (40%)
4 (60%)
Rhomboid Access Cavity
MB2 if present will be found in between MB and P
DB canal found mesial to the transverse ridge.
7 20 3 3 (60%)
4 (40%)
Rhomboid Access Cavity
DB canal usually more central
Roots generally more convergent than 6’s.

Mandibular Teeth Average Tooth Length (mm) Number of Roots Number of Canals Features
1 21 1 1 (60%)
2 (40%)
Oval shape access starting at cingulum
Extend to incisal edge to confirm absence of 2nd canal
1 canal may bifurcate to 2
Mesial and distal walls may be thin due to groove in tooth, over preparation can cause strip perforation.
2 21 1 1 (60%)
2 (40%)
Similar to central except:
May have distal curve
3 24 1 1 (90)%
2 (10%)
Ovoid access cavity
Oval coronally, round at apex
30% have lateral canals
May need to incorporate incisal edge to gain straight line access in older patients due to secondary dentine formation
4 22 1 1 (75%)
2 (25%)
Buccopalatal oval shape access cavity
Access to cusp tip for straight line access
5 22 1 1 (90%)
2 (10%)
Similar to lower 4 but lingual pulp horn more prominent
6 21 2 3 (65%)
4 (35%)
Quadrilateral Access Cavity
Wider mesially than distally
Mesial canals are under cusp tips
Distal is widest and usually oval in shape
Distal canal usually in centre, if not, high chance of 2nd canal
7 20 2 2 (10%)
3 (90%)
Similar to the 5 but smaller in size

 

Manogue M, Patel S, Walker R, 2013 The Principles of Endodontics 2nd Edition; Oxford; Oxford University Press
Garg N, Garg A, 2010; Textbook of Endodontics 2nd Edition; Jaypee Brothers Medical Publishers