Access opening - A quick notes

It is the first step in root canal treatment of a teeth. Let us know various types of access opening methods / approaches. The access cavity preparation generally refers to the part of the cavity from the occlusal table to the canal orifices.

Objectives

• To remove all caries 
• To conserve sound tooth structure 
• To completely unroof the pulp chamber 
• To remove all coronal pulp tissue (vital or necrotic) 
• To locate all root canal orifices 
• To achieve straight- or direct-line access to the apical foramen or to the initial curvature of the canal 
• To establish restorative margins to minimize marginal leakage of the restored tooth 
• Visualization of the Likely Internal Anatomy 
• Determination of the point of penetration 
• Assessment of occlusal and external root form 
• Radiographic measurement of the depth of the pulp chamber roof from the occlusal table 
• Assessment of complicating factors 
• Radiographic assessment 
• Evaluation of the Cementoenamel Junction and Occlusal Anatomies 

Guidelines

• Preparation of the Access Cavity Through the Lingual and Occlusal Surfaces 
• Removal of All Defective Restorations and Caries Before Entry Into the Pulp Chamber 
• Removal of Unsupported Tooth Structure 
• Creation of Access Cavity Walls That Do Not Restrict Straight- or Direct-line Passage of Instruments to the Apical Foramen or Initial Canal Curvature 
• Delay of Dental Dam Placement Until Difficult Canals Have Been Located and Confirmed 
• Location, Flaring, and Exploration of All Root Canal Orifices 
• Inspection of the Pulp Chamber, Using Magnification and Adequate Illumination 
• Tapering of Cavity Walls and Evaluation of Space Adequacy for a Coronal Seal 

Newer designs of access cavity preparation

• Conservative endodontic access cavity  
• Ultra conservative access cavity / ‘Ninja'
• Orifice – directed dentin conservation access cavity / Truss
• Caries driven
• Restorative driven 
• Cala lilly enamel preparation 
• Image guided endodontic access 
• Dynamically guided endodontic access 
• Micro guided endodontic access 

Conservative access cavity

• By David Clark and John Khademi 
• Lessen the tooth structure removal 
• Helps the long time survival & function of root canal treated tooth 
• Here, the teeth are accessed at the central fossa and they are extended out to discover canal orifices. This aids in protecting the pericervical dentin and a part of the chamber floor 

Ultra conservative access cavity/ Ninja method

• Here, an oblique projection is made towards the central fossa of the root canal orifices 
• This projection is made parallel with the enamel cut of 90 degree or more to the occlusal plane 
• This makes simpler to discover the canal orifices from different visual angulations 
• Limited line of vision, incomplete removal of infected pulpal tissue is the main limitation leading to failure of endodontic treatment 

Orifice- Directed Dentin Conservation Access Cavity / ‘Truss’

• Separate cavities are made to approach the canals 
• The point of this methodology is to preserve dentin with the minimally invasive approach i.e. leaving a truss of dentin between the two cavities that have been prepared 
• The restricting components of this methodology which are past the operator’s control are position of tooth, patients mouth opening capability, degree of calcification & other patient related variables 

Caries driven 

Entry into the pulp chamber is carried out by extracting caries and maintaining all the remaining structure of the tooth 

Cala lilly enamel preparation

• Usually, unfavourable C factor and weak enamel rod engagement are present when eliminating old amalgam or composite restoration or with the traditional endodontic access cavity 
• Enamel in the form of cala lilly is cut back at 45 

Dynamically Guided Endodontic Access

• Dr. Charles M introduced it for the first time for implants 
• CBCT is used to design an access cavity 
• Overhead cameras are used to trace the location of patients jaw and clinicians bur in three dimensional space 
• After looking at the software interface, the clinician provides input about the bur location 

Article by: Dr. Siri P.B.