L6 Abbot Pulp + Root Morphology, Access - 2018_formatted_text

Pulp and Root Morphology¹

Note

The mechanical aspects of root canal treatment require a thorough knowledge of pulp and root canal morphology. This knowledge must be applied on a case-by-case basis, as anatomy varies significantly between patients. While there are typical anatomical patterns for each tooth type, clinicians must also be aware of common and uncommon variations.

Pre-operative Assessment²

Pre-operative assessment relies on:

• a) Thorough knowledge of the anatomy of each tooth type

  • Common / typical
  • Variations

• b) Clinical examination

• ==Crown Morphology: The external shape of the tooth’s crown can provide clues about the underlying root and canal anatomy.==

  • ==Gingival Recession: If present, recession may expose parts of the root, revealing unusual anatomical findings.==

• c) Radiographic examination

• Pre-operative radiographs are essential not only for diagnosis but also for assessing the anatomy of the roots and the canal systems within them.

  • ==Specific radiographic signs can alert the clinician to anatomical variations. For example:
    • A radiolucency located on the mesial or distal aspect of a root, rather than at the apex, can indicate the presence of a lateral canal exiting on that surface. The lesion often expands symmetrically around the foramen of this lateral canal.
    • A sudden

Resources³

• ==Textbooks and Journal Articles: Dentists and students should dedicate time to reading current literature on root canal anatomy to stay informed about the vast range of possible variations.==

• 3-D Tooth Atlas

3D Visualization Software

Software programs can help create a three-dimensional mental picture of the tooth’s internal and external anatomy. An example is the E Human Atlas (formerly the 3D Tooth Atlas), which allows users to scroll through virtual cross-sections of teeth, helping to relate the canal system to the external tooth structure.

Anatomical Variations⁴⁵

• Cross-sectional shape of canals varies at different levels

• Canals are very rarely perfectly round. They are often oval, flattened, or irregular in shape.

• For example, in a mandibular incisor, a cross-section might show what appears to be a single canal at one level, but two distinct canals at a more apical level.

• Some longitudinal variations of different canals

• ==Common patterns include:

  • Type I: A single canal from the pulp chamber to the apex.
  • Type II: Two separate canals leaving the chamber, which join to form one canal before the apex.
  • Type III: One canal leaving the chamber, which divides into two canals within the root.
  • Type IV: Two separate and distinct canals from the chamber to the apex.==

• ==Complex Systems: Some roots, like the mesiobuccal root of an upper first molar, can have extremely complex anatomy. For many years, it was believed to have only one canal. It is now known that two canals (mesiobuccal and mesiopalatal) are very common, and they can join, separate, and rejoin along their path.==

• • Many others are possible !!!

Access Cavities⁶

Aims and General Principles

The primary aims of an access cavity are to:

1. Open the entire pulp chamber to remove all pulpal tissue.

2. Locate all canal orifices (entrances).

3. Achieve straight-line access to negotiate all canals to their apical foramen.

• Location:
  • Anterior Teeth: Access is typically through the palatal (upper) or lingual (lower) surface.
  • Posterior Teeth: Access is through the occlusal surface.

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• Upper Central Incisor

• ==Anatomy: Typically one root with one canal.==

  • ==Access: A triangular shape on the palatal surface, located in the middle of the crown. In younger patients with large pulp horns, the triangle is broader; in older patients with smaller canals, the access can be smaller and more ovoid.==

• Upper Lateral Incisor

• ==Anatomy: Typically one root with one canal. Two roots are extremely rare.==

  • ==Access: An oval or slightly triangular shape on the palatal surface, narrower mesio-distally than the central incisor’s access.==

• Upper Canine

• ==Anatomy: Most commonly one root with one canal. The canal is flattened mesio-distally. Occasionally, it can have two roots and two canals (resembling a premolar) or, very rarely, two canals in one root.==

  • ==Access: An oval shape on the palatal surface, elongated from the incisal to the gingival aspect.==

Lower Teeth⁷

• Lower Central Incisor

• Lower Lateral Incisor

• ==Anatomy: Typically one root, but a high percentage (50-70%) have two canals (labial and lingual). Lateral incisors are slightly more likely to have two canals than centrals.==

  • ==Access: An oval shape on the lingual surface, elongated inciso-gingivally. In cases of severe attrition, access may be made directly through the incisal edge.==

  Clinical Pearl Always assume and search for two canals. The lingual canal is frequently missed as it is tucked under the cingulum. The access may need to be extended gingivally to locate it.

• Lower Canine

• ==Anatomy: Most commonly one root, but it can have one or two canals. Two roots with two canals is not unusual.==

  • ==Access: An oval shape on the lingual surface. As with incisors, always search for a second canal.==

Upper Teeth (Continued)⁸

• Upper 1st Premolar
• ==Anatomy: Highly variable.
  • Most Common: Two roots (buccal, palatal) with two canals.
  • Variations: One root with one or two canals; three roots (mesiobuccal, distobuccal, palatal) with three canals.==
  • ==Access: An oval cavity on the occlusal surface, elongated bucco-palatally. It should be placed slightly distal to the midline to avoid perforating the mesial concavity of the root.==

- **Upper 2nd Premolar**

• ==Anatomy:
  • Most Common: One root with one canal.
  • Next Common: One root with two canals (buccal, palatal).
  • Less Common: Two roots with two canals. Rarely, three roots.==
  • ==Access: An oval cavity centered on the occlusal surface. If a single canal orifice is found off-center (e.g., towards the buccal), a

Lower Teeth (Continued)⁹¹⁰


• Lower 1st Premolar

• ==Anatomy: Most commonly one root with one canal. However, it can have two or even three canals that often divide mid-root or in the apical third, making them difficult to treat.==

  • ==Access: An oval cavity on the occlusal surface, centered mesio-distally but positioned more towards the lingual aspect. The access is initiated in the central groove.==

• Lower 2nd Premolar

• ==Anatomy: Typically one root with one canal. Variations with two or three canals exist but are less common than in the first premolar.==

  • ==Access: Similar to the first premolar, centered mesio-distally and slightly towards the lingual.==

• Lower 1st Molar

• ==Anatomy: Typically two roots (mesial and distal).

  • The mesial root almost always has two canals (mesiobuccal and mesiolingual).
  • The distal root has one or two canals with roughly 50/50 probability.==
  • ==Access: A rectangular or trapezoidal shape, located in the mesial half of the occlusal surface.==

  Clinical Pearl Always assume and search for four canals. Older triangular access designs often led to missing a second distal canal.

• Lower 2nd Molar

• ==Anatomy: Variable.

  • Most Common: Two roots with three canals (two in the mesial, one in the distal).
  • Variations: Can have two, three, or four canals. A single root is also possible.
  • C-Shaped Canals: This tooth is a common site for a

• Lower 3rd Molar

• ==Anatomy: Highly variable, often with two roots and 2-4 canals, but extra or fused roots are common.==

  • ==Access: A rectangular shape, positioned mesially and slightly towards the buccal on the occlusal surface.==

Clinical Application and Limitations¹¹¹²¹³

• Typical access cavities - from texts
• BUT - these do not account for the state of typical teeth that require endodontic treatment

The Real-World Scenario

Most teeth requiring root canal treatment have extensive caries, large restorations, or fractures.

A procedure is shown on a molar where one tooth is prepared with an onlay, an adjacent tooth has a metal restoration, and another tooth has a composite or porcelain restoration.

The Clinical Process

1. Initial Treatment: The first step is to remove all existing restorations and caries to assess the remaining tooth structure. At this stage, locating the pulp chamber is often straightforward.
2. Interim Restoration: The tooth is then built up with an interim restoration (e.g., a stainless steel band and glass ionomer cement) to facilitate isolation and prevent contamination between appointments.
3. Marking the Chamber: Before placing the final layer of the interim restoration, a soft material like Cavit can be placed over the canal orifices.
4. Second Appointment Access: The

• BUT - use these for access through interim restorations after the existing restorations, caries, & cracks have been removed

Conservation of Tooth Structure

• If the access cavity is entirely within the interim restorative material, its exact shape is not critical, and it can be enlarged for better visibility without weakening the tooth.
• However, if creating ideal access requires removing more natural tooth structure, the clinician must be cautious to preserve as much tissue as possible to avoid weakening the tooth and compromising its long-term prognosis.

UPPER TEETH	LOWER TEETH
(Diagram showing access cavities for upper arch)	(Diagram showing access cavities for lower arch)
Image Description: A diagram illustrating typical access cavities for upper and lower teeth.

Footnotes

1. Original PDF page 1: L6 Abbot Pulp + Root Morphology, Access - 2018, p.1 ↩

2. Original PDF page 2: L6 Abbot Pulp + Root Morphology, Access - 2018, p.2 ↩

3. Original PDF page 5: L6 Abbot Pulp + Root Morphology, Access - 2018, p.5 ↩

4. Original PDF page 7: L6 Abbot Pulp + Root Morphology, Access - 2018, p.7 ↩

5. Original PDF page 8: L6 Abbot Pulp + Root Morphology, Access - 2018, p.8 ↩

6. Original PDF page 9: L6 Abbot Pulp + Root Morphology, Access - 2018, p.9 ↩

7. Original PDF page 14: L6 Abbot Pulp + Root Morphology, Access - 2018, p.14 ↩

8. Original PDF page 15: L6 Abbot Pulp + Root Morphology, Access - 2018, p.15 ↩

9. Original PDF page 16: L6 Abbot Pulp + Root Morphology, Access - 2018, p.16 ↩

10. Original PDF page 18: L6 Abbot Pulp + Root Morphology, Access - 2018, p.18 ↩

11. Original PDF page 19: L6 Abbot Pulp + Root Morphology, Access - 2018, p.19 ↩

12. Original PDF page 21: L6 Abbot Pulp + Root Morphology, Access - 2018, p.21 ↩

13. Original PDF page 23: L6 Abbot Pulp + Root Morphology, Access - 2018, p.23 ↩