Endodontic Access Cavity Anatomy

Questions and Answers

What shape is the access cavity for a single-canal mandibular second molar?

Oval

What is the most commonly seen type of canal in a mandibular second molar?

C-shaped canal

What type of difficulties are created by poor access during root canal treatment?

Risk of tooth fracture

What can debris falling into the canal orifices during root canal treatment cause?

Secondary caries and discoloration Signup and view all the answers

What can make the location of root canal orifices difficult during access cavity preparation?

Pulp stones Signup and view all the answers

What anatomical feature can complicate root canal treatment in mandibular molars?

C-shaped canals Signup and view all the answers

Which wall connects the mesiolingual and distolingual orifices in a mandibular second molar?

Lingual wall Signup and view all the answers

What can inadequate caries removal during root canal treatment lead to?

Secondary caries Signup and view all the answers

What is the shape of the pulp chamber in a mandibular second molar compared to a first molar?

Smaller in size Signup and view all the answers

What difficulties can be caused by labial perforation during root canal treatment?

Weakening of coronal tooth structure Signup and view all the answers

Study Notes

Size of Pulp Chamber

In young patients, pulp chamber is larger in all three dimensions, requiring more extensive preparation.
In older patients, pulp has receded, and pulp chamber is smaller in all three dimensions.

Shape of Pulp Chamber

Incisors: Triangular shape
Premolars: Ovoid bucco-lingually shape
Molars: Triangular or Trapezoidal shape

Number, Position, and Curvature of Root Canals

Cavity walls are extended to allow easy instrument approach to the apical foramen.
Knowledge of internal anatomy of individual tooth is essential due to variations in canal anatomy.

Principles of Access Cavity Preparation

Principle I: Preservation of Tooth Structure
Principle II: Convenience Form
- Unobstructed access to canal orifice
- Direct access to apical foramen
Principle III: Removal of Remaining Carious Dentin
- Eliminate mechanically as many bacteria as possible
- Eliminate discolored tooth structure
- Eliminate saliva leaking into the prepared cavity
Principle IV: Cleansing of the Cavity
- Removal of calcified or metallic debris
- Removal of soft debris
- Prevention of bacterial population and crown staining

Laws of Access Cavity Preparation

Radiographs help in knowing:
- Morphology of the tooth
- Anatomy of root canal system
- Number of canals
- Curvature of branching of the canal system
- Length of the canal
- Position and size of the pulp chamber and its distance from occlusal surface
- Position of apical foramen
- Calcification, resorption present if any

Classification of Access Cavity Preparation Instruments

I. Initial Penetration
- Round and tapered tungsten carbide bur
- Round and tapered diamond points
- Endo access bur
II. Unroofing the Pulp Chamber
- Endo access bur with a safe tip or non-cutting tip
- Round Bur
- Tapered fissure Bur
III. Canal Orifice Flaring Instruments
- Gates-Glidden drill
- Peeso Reamer
- NiTi rotary file
IV. Endodontic Pathfinders
- DG-16 Endodontic explorer
- Ultrasonic unit and tips
- NiTi pathfinder rotary file
V. Vision, Magnification, and Illumination
- Fiber optic light source
- Methyline blue
- Surgical operating microscope
- Binocular loupes
- DG-16 endodontic explorer

Access Cavity Preparation for Different Teeth

Maxillary Central Incisor
- Access cavity is oval or triangular in shape
- Removal of lingual shoulder is critical
Mandibular Incisors
- Access cavity is long oval with greater dimension incisogingivally
- Complete removal of lingual shoulder is critical
Mandibular Canine
- Access cavity is oval or slot-shaped
- One canal is present, but two canals could be present
Maxillary Molars
- Bur entry is determined by the mesial boundary and oblique ridge
- Place bur in Central groove between Mesial and Distal boundary and direct it Palatally
- Feel drop and de-roof using round, tapered fissure or safe tip bur
- Shape and size of the chamber guide the cutting
- Locate canal orifice with Endo explorer, remove ledge or obstruction if present
- Smoothen cavity walls and merge with pulp chamber diverging occlusally

Difficulties Created by Poor Access

Overzealous tooth preparation
Inadequate caries removal
Labial perforation
Furcal perforation
Root perforation due to misinterpretation of angulation
Debris falling into the orifices such as old amalgam restorations and dentin debris

Difficulties During Access Opening and Trouble Shooting

Calcifications
Unusual anatomy
C-shaped canal
Bayonet-shaped canals