Overview
This lecture introduces the key concepts and procedural steps for creating molar access cavities in endodontics, focusing on upper and lower first and second molars, their anatomy, and proper access techniques.
Importance of Molar Access Cavities
- Access cavity is the essential first technical step in root canal treatment.
- Proper access ensures removal of infection and assessment of tooth restorability.
- Ensures straight-line access to all canal orifices for effective cleaning and shaping.
Molar Anatomy Overview
- Maxillary (upper) first and second molars usually have three roots (mesiobuccal, distobuccal, palatal).
- Mesiobuccal root often contains two canals (MB1 and MB2), especially in first molars (≈90%).
- Mandibular (lower) molars commonly have two roots (mesial and distal), with two canals in mesial and one in distal root.
- Additional or fewer canals may be present, especially in second/third molars or with root fusion.
Principles of Access Cavity Preparation
- Remove all caries and unsupported enamel before access.
- Confirm tooth is restorable before proceeding with root canal treatment.
- Design of access cavity varies with tooth type, but straight-line access to canals is essential.
- Maxillary molars: cavity is triangular with base towards buccal, apex towards palatal.
- Mandibular molars: cavity is triangular with base towards mesial, apex towards distal.
Access Cavity Preparation Technique
- Use endo access bur or diamond cylinder bur (never round diamond bur for molars).
- Identify mesiobuccal cusp; drill initial access hole 1-1.5mm toward center from this cusp.
- Drill vertically (6-6.5mm) until pulp chamber is accessed (not exceeding 8mm).
- Enlarge initial hole with gentle stirring motion to fit endo Z bur.
- Use endo Z bur to extend access and remove pulp chamber roof, following anatomical outline.
- Locate canal orifices with probe or small hand files (sizes 6, 8, or 10).
- Perform orifice opening using Gates Glidden burs or SX file; coronal flaring if necessary.
Key Terms & Definitions
- Access cavity — Opening made in the tooth to allow entry to the root canals.
- Mesiobuccal (MB) root/canal — The root (and canal) nearest the cheek and midline in molars.
- Palatal canal — Canal in the root closest to the palate in upper molars.
- Straight-line access — An unobstructed path from the cavity to the canal orifice.
- Endo access bur — Specialized bur for initial access cavity cutting.
- Endo Z bur — Bur with a non-cutting tip used to remove the pulp chamber roof horizontally.
Action Items / Next Steps
- Obtain first or second extracted molars (upper and lower) for practice.
- Take diagnostic radiographs of the extracted teeth.
- Practice access cavity preparation using correct burs as described.
- Watch the provided preclinical demonstration videos on ClickUp or YouTube.