Endodontic Access Cavity Preparation

Lecture from 8/11/2025

endodontic access cavity

the opening prepared in a tooth to gain entrance to the pulp canal system for the purpose of cleaning, shaping, and obturating

what are the pre-treatment objectives of access cavity preparation?

evaluation of existing restoration, removal of existing restoration, removal of ALL caries, evaluate restorability, occlusal clearance of posterior teeth

what is important to know about evaluating restorability?

you need to evaluate biological width

2mm distance between the periodontal tissue and restoration is to prevent chronic inflammation

how much do you need to reduce occlusal clearance by, and why is it important?

reduce by 0.5 mm

important to get the tooth out of occlusion for patient comfort and protection of the tooth

produce flat surface for reproducible reference point

what are the objectives of access cavity preparations?

removal of pulp chamber roof, removal of pulp stones, locating of all canals, straight line access to every canal, divergent smooth walls, preservation of structural integrity of the tooth

why is it important to preserve tooth structure when preparing a tooth for access cavity?

you need to have enough tooth to perform a crown preparation

how should the walls be prepared when preparing an access cavity?

divergent or parallel walls

why is it important for the walls to be divergent or parallel in an access cavity preparation?

divergent walls allow for a better seal and for better visualization into the canals

convergent walls may also allow fillings to sink down

why is it important to examine the long access of the tooth on radiographs?

it gives you the distance and direction of finding the pulp chamber

most teeth have a ______ inclination, and it gets ______ with age

mesial, better

what instruments are necessary for performing an access cavity preparation?

dressing pliers, periodontal probe, endodontic explorer, spoon excavator, mirror, surgical length (long shank) round burs, tapering fissure carbide or diamond bur

t/f a 17/23 explorer is the same as an endodontic explorer

false

how many roots and pulp horns does a maxillary central incisor have?

1 root, 2-3 pulp horns

does a maxillary central incisor have an inclination?

labial and mesial inclination

what shape should the access cavity be on a maxillary central incisor be?

triangular

how should an access cavity preparation be started when doing a maxillary central incisor?

the initial entrance should be at a right angle, the extension should be done with the long axis of the tooth

what motion should be used to create a cavity access preparation?

sweeping out motion

what are the dimensions of an ideal access cavity on a maxillary central incisor?

the triangular preparation should be 3mm across by 4mm wide, there should be an additional bevel of 1mm on the sides and top, and a 2mm bevel on the short side of the triangle

what are common errors found in creating a cavity access preparation on a maxillary central incisor?

labial perforation, ledge formation, inadequate access, over-extension, or under-extension (can discolor the tooth)

how should an access cavity preparation be completed on a maxillary lateral incisor?

the same as a maxillary central incisor, but smaller and a bit more ovoid than triangular

how many roots and pulp horns does a maxillary canine have?

1 root, 2 pulp horns

what shape should a maxillary lateral incisor access cavity preparation be?

ovoid

what shape should a maxillary canine access cavity preparation be?

ovoid

how many canals does a maxillary 1st premolar have?

2 canals at the apex 69%

2 canals into one at apex 18%

one canal 8%

how many roots and pulp horns does a maxillary 1st premolar have?

2 roots (3 roots in 5%), 2 pulp horns

what shape should a maxillary 1st premolar access cavity preparation be?

ovoid (from buccal to lingual)

how many roots, pulp horns, and canals does a maxillary 2nd premolar have?

1 root, 2 pulp horns, 1 canal in 75%

what shape should a maxillary 2nd premolar access cavity preparation be?

ovoid

what shape should a maxillary 1st molar access cavity preparation be?

rhomboid shape

how many roots and canals does a maxillary 1st molar have?

3 roots, 4 canals 95.2% of the time (MB root)

in a maxillary 1st molar, the pulp chamber is closer to the ______

mesial

t/f when drilling an access cavity on a maxillary 1st molar, you need to cross the oblique transverse ridge

false- you should NEVER cross the oblique transverse ridge

what is important to do when creating a maxillary 1st molar access preparation?

to ensure straight line access, assess the direction of canal access and remove the cervical dentin overhang

what shape should a mandibular anterior access cavity preparation be?

ovoid

how many roots and canals does a mandibular anterior have?

1 root, 2 canals in 41.4%

which canal is most often missed on mandibular anteriors, and why?

lingual canal, often missed because it is under the cingulum

how many roots and canals does a mandibular caninie have?

1 root, 1 canal

occasionally have 2 canals and 2 roots

what shape should a mandibular canine access cavity preparation be?

ovoid

what shape should a mandibular 1st premolar access cavity preparation be?

ovoid

how many roots and canals does a mandibular 1st premolar have?

1 root, 1 canal 74% of the time

how many roots and canals does a mandibular 2nd premolar have?

1 root, 1 canal in 97.5% of the time

what shape should a mandibular 2nd premolar access cavity preparation be?

ovoid

SLOB rule in dental

Two radiographs are taken of the same area, but with a change in the horizontal or vertical angulation of the x-ray beam. 

If the object of interest appears to move in the same direction as the x-ray beam shift, it is located on the lingual side.

If the object appears to move in the opposite direction of the x-ray beam shift, it is located on the buccal side.

what shape should a mandibular 1st molar access cavity preparation be?

rhomboid shape (not triangular)

how many roots and canals does a mandibular 2nd premolar have?

3 roots, 3 canals (4th canal in 33%)

why was the access cavity shape of a mandibular 1st molar changed from triangular to rhomboid shape?

makes it easier to find a potential 4th canal

what is a common canal configuration for mandibular 2nd molars, and what does it mean?

C shaped canal configuration in 4-7.6%

canals are fused together into a C shape- will bleed a lot more

how many roots and canals does a mandibular 2nd premolar have?

2 roots, 3 canals (2 canals only in 4%)

what are common errors that are made when creating an access cavity preparation on mandibular 2nd molars?

furcation perforation or mesial perforation

what is the outline shape of acess cavity preparations dictated by?

tooth type and internal pulp anatomy (makes it dynamic)