L6 Access 2_formatted_text

Access Cavities¹

Goal of an Access Cavity

The primary goal is to provide straight-line, unimpeded access to the pulp chamber and the root canals. Classic textbook designs are often most relevant when cutting through an interim restoration, but the principles apply to all teeth, including those without existing restorations.

Method²³⁴⁵

1. High speed bur
   • Tungsten Carbide
     • e.g. **Jet # 331

• ==Rationale: Tungsten carbide burs are more efficient cutting instruments than diamond burs. The action is comparable to cutting with a knife, which is more effective than the abrasive, sandpaper-like action of a diamond bur. - Usage==: This is the primary bur for initial entry and outlining the access cavity.

**

2. Cut DRY - i.e. no water
   • No need to cool pulp!!
   • Better vision
   • No debris forced into the canals

• Eliminates the need for an assistant to manage suction and keep the mirror clear.

Use Light Pressure

Use a very light touch and let the bur do the work. Excessive pressure will generate heat and the smell of burning dentin, indicating poor technique.

3. Use correct angle

   • Esp. anterior teeth

4. Low speed bur

   • **Round bur - 26 mm

• ==Rationale==: The longer shank moves the head of the handpiece away from the occlusal surface, significantly improving visual access to the pulp chamber floor. The purpose is not to drill deeper.
  • ==Usage==: Used for refining the access cavity shape, removing dentin lips or overhangs, and creating a smooth, funnel-like transition into the canals.

**

5. Cut on withdrawal stroke

• This involves engaging the bur against the cavity walls and pulling it outwards in a “shaving” or “brushing” motion.
  • This technique is used to flare the walls, remove pulp horns, and eliminate any dentinal ledges (especially on the palatal/lingual aspect of anterior teeth) that would impede straight-line access.
  • ==Never apply pressure on the inward stroke, as this can easily cut into the delicate pulp chamber floor and cause a perforation==.

6. Open entire pulp chamber

7. Explore floor of pulp chamber to locate the canal orifices

   • **Use the DG16 Endo. Explorer

• It is a double-ended instrument with straight, sharp points at different angles, superior to a standard sickle probe for endodontics. - ==Usage==: Explore the pulp chamber floor with enhanced tactile sensation to feel for a “catch” at the canal orifice and to chip away small calcifications or lips of dentin that may be obscuring a canal entrance.

**

-   **Front Surface Mirror

Why Front Surface is Essential

A Front Surface Mirror has the reflective coating on the top surface, providing a single, crisp reflection. A Back Surface Mirror has the coating behind a layer of glass, which can create multiple “ghost” images, making it difficult to locate tiny canal orifices.

**

    Front Surface
    
    Back Surface

-   **31LS Excavator**

• ==Description==: An excavator with a long shank and a narrow, oval-shaped head, distinct from wider, spoon-shaped operative excavators.
  • ==Usage==: Removing pulp tissue from the chamber, removing caries, or chipping away small calcifications on the pulp chamber floor.

8. Negotiate canals with a small hand file
   • e.g. Size 10 or 15
   • **But will vary with each tooth and each canal

Ensure Sufficient Access Size

The access cavity must be large enough to allow files to enter all canals simultaneously, which is necessary for taking a working length radiograph with files in place.

**

HINT^6789101112

• ==The floor of the pulp chamber is always darker than the surrounding dentin of the cavity walls==. This color change is a key indicator that you have reached the correct depth.

• Look for the “road map” of dark lines on the floor of the pulp chamber

  • $\Rightarrow$ Helps identify the canal orifices

• Generally, the canals will be where the lines meet / stop

Two images showing access to the pulp chamber of a tooth with arrows pointing to the canal openings. This is an image only with sparse text and labels (arrows). The images show a dental procedure related to endodontic access, highlighting the pulp chamber of a tooth and indicating the canal orifices with arrows.

• Transilluminate the floor of the pulp chamber to help locate the canal orifices

• Canal orifices will appear as distinct spots against the illuminated background: - ==Dark Dot: Typically indicates an empty, pulpless canal. - White Dot==: Typically indicates a canal filled with fluid or necrotic tissue.

Common Errors¹³¹⁴

• ==Incorrect Depth and Preparation==
  • ==Cutting Too Deep==: Going past the pulp chamber can lead to perforation through the labial surface of an anterior tooth or the furcation of a molar. Learn the tactile sensation of the bur “dropping” into the chamber.
  • ==Mistaking Pulp Horns for Canals==: This occurs when the roof of the pulp chamber is not fully removed. The operator finds three “holes” (the pulp horns) but is not actually on the pulp chamber floor.
    • ==The Fix==: “Join the dots.” The access must be widened to remove the entire roof of the pulp chamber, revealing the darker floor and true canal orifices below.
• ==Incorrect Size, Shape, and Position==
  • ==Under-prepared (Too Conservative)==: Leaves necrotic tissue in the pulp horns, which can lead to future tooth discoloration and creates ledges that prevent straight-line access for files.
  • ==Over-prepared (Too Large)==: Unnecessarily removes sound tooth structure, weakening the tooth.
  • ==Incorrect Position==: Placing the access cavity too far distally in a lower molar can cause you to miss the mesial canals entirely.
• ==Perforations==
  • A perforation is a catastrophic error that severely compromises the tooth's prognosis.
  • ==Causes==: Cutting too deep with a high-speed bur, using a low-speed bur with pressure on the inward stroke, or misjudging the angulation of a tilted tooth (especially one with a crown).
• ==Missing Canals==
  • ==Lower Incisors==: It is very common for these teeth to have two canals. Always assume there are two and extend the access sufficiently to the lingual to find the second one.
  • ==Upper Molars==: The fourth canal (MB2) is frequently present and will be missed if the access is not extended appropriately.
  • ==Lower Molars==: Using an outdated triangular access design will often lead to missing the fourth canal. A modern rectangular or trapezoidal shape is required.

Pulp and Root Morphology^{15161718192021}

The Importance of Preoperative Assessment

Successful endodontic treatment is fundamentally dependent on a thorough understanding of the tooth’s internal anatomy before treatment begins.

Pre-operative assessment relies on:

• a) Thorough $\underline{\text{knowledge}}$ of the anatomy of each tooth type
  • Common / typical
  • Variations
• b) Clinical examination
• c) $\underline{\text{Radiographic examination

Study and Visualization

• It is essential to study textbooks, journal articles, and modern 3D imaging programs to develop a strong understanding of complex root canal systems.
• The ultimate goal is to know the internal anatomy so that the canals can be effectively located, cleaned, disinfected, and ultimately filled.

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Footnotes

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