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📖 Oral and Maxillofacial Surgery

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Impacted Third Molars
Oral and Maxillofacial Surgery

Classification and Management of Impacted Third Molars

Impacted third molars, commonly known as wisdom teeth, can present in various orientations and depths, influencing the difficulty of their extraction. Understanding the types of impactions and their classifications is crucial for planning surgical intervention.

Types of Impaction

  1. Mesioangular Impaction:

    • Description: The tooth is tilted toward the second molar in a mesial direction.
    • Prevalence: Comprises approximately 43% of all impacted teeth.
    • Difficulty: Generally acknowledged as the least difficult type of impaction to remove.

  2. Vertical Impaction:

    • Description: The tooth is positioned vertically, with the crown facing upward.
    • Prevalence: Accounts for about 38% of impacted teeth.
    • Difficulty: Moderate difficulty in removal.

  3. Distoangular Impaction:

    • Description: The tooth is tilted away from the second molar in a distal direction.
    • Prevalence: Comprises approximately 6% of impacted teeth.
    • Difficulty: Considered the most difficult type of impaction to remove due to the withdrawal pathway running into the mandibular ramus.

  4. Horizontal Impaction:

    • Description: The tooth is positioned horizontally, with the crown facing the buccal or lingual side.
    • Prevalence: Accounts for about 3% of impacted teeth.
    • Difficulty: More difficult than mesioangular but less difficult than distoangular.

Decreasing Level of Difficulty for Types of Impaction

  • Order of Difficulty:
    • Distoangular > Horizontal > Vertical > Mesioangular

Pell and Gregory Classification

The Pell and Gregory classification system categorizes impacted teeth based on their relationship to the mandibular ramus and the occlusal plane. This classification helps assess the difficulty of extraction.

Classification Based on Coverage by the Mandibular Ramus

  1. Class 1:

    • Description: Mesiodistal diameter of the crown is completely anterior to the anterior border of the mandibular ramus.
    • Difficulty: Easiest to remove.

  2. Class 2:

    • Description: Approximately one-half of the tooth is covered by the ramus.
    • Difficulty: Moderate difficulty.

  3. Class 3:

    • Description: The tooth is completely within the mandibular ramus.
    • Difficulty: Most difficult to remove.

Decreasing Level of Difficulty for Ramus Coverage

  • Order of Difficulty:
    • Class 3 > Class 2 > Class 1

Pell and Gregory Classification Based on Relationship to Occlusal Plane

This classification assesses the depth of the impacted tooth relative to the occlusal plane of the second molar.

  1. Class A:

    • Description: The occlusal surface of the impacted tooth is level or nearly level with the occlusal plane of the second molar.
    • Difficulty: Easiest to remove.

  2. Class B:

    • Description: The occlusal surface lies between the occlusal plane and the cervical line of the second molar.
    • Difficulty: Moderate difficulty.

  3. Class C:

    • Description: The occlusal surface is below the cervical line of the second molars.
    • Difficulty: Most difficult to remove.

Decreasing Level of Difficulty for Occlusal Plane Relationship

  • Order of Difficulty:
    • Class C > Class B > Class A

Summary of Extraction Difficulty

  • Most Difficult Impaction:
    • Distoangular impaction with Class 3 ramus coverage and Class C depth.
  • Easiest Impaction:
    • Mesioangular impaction with Class 1 ramus coverage and Class A dep
Radiological Signs
Oral and Maxillofacial Surgery

Radiological Signs Indicating Relationship Between Mandibular Third Molars and the Inferior Alveolar Canal

In 1960, Howe and Payton identified seven radiological signs that suggest a close relationship between the mandibular third molar (wisdom tooth) and the inferior alveolar canal (IAC). Recognizing these signs is crucial for dental practitioners, especially when planning for the extraction of impacted third molars, as they can indicate potential complications such as nerve injury. Below are the seven signs explained in detail:

1. Darkening of the Root

  • This sign appears as a radiolucent area at the root of the mandibular third molar, indicating that the root is in close proximity to the IAC.
  • Clinical Significance: Darkening suggests that the root may be in contact with or resorbing against the canal, which can increase the risk of nerve damage during extraction.

2. Deflected Root

  • This sign is characterized by a deviation or angulation of the root of the mandibular third molar.
  • Clinical Significance: A deflected root may indicate that the tooth is pushing against the IAC, suggesting a close anatomical relationship that could complicate surgical extraction.

3. Narrowing of the Root

  • This sign is observed as a reduction in the width of the root, often seen on radiographs.
  • Clinical Significance: Narrowing may indicate that the root is being resorbed or is in close contact with the IAC, which can pose a risk during extraction.

4. Interruption of the White Line(s)

  • The white line refers to the radiopaque outline of the IAC. An interruption in this line can be seen on radiographs.
  • Clinical Significance: This interruption suggests that the canal may be displaced or affected by the root of the third molar, indicating a potential risk for nerve injury.

5. Diversion of the Inferior Alveolar Canal

  • This sign is characterized by a noticeable change in the path of the IAC, which may appear to be deflected or diverted around the root of the third molar.
  • Clinical Significance: Diversion of the canal indicates that the root is in close proximity to the IAC, which can complicate surgical procedures and increase the risk of nerve damage.

6. Narrowing of the Inferior Alveolar Canal (IAC)

  •  This sign appears as a reduction in the width of the IAC on radiographs.
  • Clinical Significance: Narrowing of the canal may suggest that the root of the third molar is encroaching upon the canal, indicating a close relationship that could lead to complications during extraction.

7. Hourglass Form

  • This sign indicates a partial or complete encirclement of the IAC by the root of the mandibular third molar, resembling an hourglass shape on radiographs.
  • Clinical Significance: An hourglass form suggests that the root may be significantly impinging on the IAC, which poses a high risk for nerve injury during extraction.
Champy Technique of Fracture Stabilization
Oral and Maxillofacial Surgery

Champy Technique of Fracture Stabilization

The Champy technique, developed by Champy et al. in the mid-1970s, is a method of fracture stabilization that utilizes non-compression monocortical miniplates applied as tension bands. This technique is particularly relevant in the context of mandibular fractures and is based on biomechanical principles that optimize the stability and healing of the bone.

Key Principles of the Champy Technique

  1. Biomechanical Considerations:

    • Tensile and Compressive Stresses: Biomechanical studies have shown that tensile stresses occur in the upper border of the mandible, while compressive stresses are found in the lower border. This understanding is crucial for the placement of plates.
    • Bending and Torsional Forces: The forces acting on the mandible primarily produce bending movements. In the symphysis and parasymphysis regions, torsional forces are more significant than bending moments.

  2. Ideal Osteosynthesis Line:

    • Champy et al. established the "ideal osteosynthesis line" at the base of the alveolar process. This line is critical for the effective placement of plates to ensure stability during the healing process.
    • Plate Placement:
      • Anterior Region: In the area between the mental foramina, a subapical plate is placed, and an additional plate is positioned near the lower border of the mandible to counteract torsional forces.
      • Posterior Region: Behind the mental foramen, the plate is applied just below the dental roots and above the inferior alveolar nerve.
      • Angle of Mandible: The plate is placed on the broad surface of the external oblique ridge.

  3. Tension Band Principle:

    • The use of miniplates as tension bands allows for the distribution of forces across the fracture site, enhancing stability and promoting healing.

Treatment Steps

  1. Reduction:

    • The first step in fracture treatment is the accurate reduction of the fracture fragments to restore normal anatomy.

  2. Stabilization:

    • Following reduction, stabilization is achieved using the Champy technique, which involves the application of miniplates in accordance with the biomechanical principles outlined above.

  3. Maxillomandibular Fixation (MMF):

    • MMF is often used as a standard method for both reduction and stabilization, particularly in cases where additional support is needed.

  4. External Fixation:

    • In cases of atrophic edentulous mandibular fractures, extensive soft tissue injuries, severe communication, or infected fractures, external fixation may be considered.

Classification of Internal Fixation Techniques

  • Absolute Stability:

    • Rigid internal fixation methods, such as compression plates, lag screws, and the tension band principle, fall under this category. These techniques provide strong stabilization but may compromise blood supply to the bone.

  • Relative Stability:

    • Techniques such as bridging, biologic (flexible) fixation, and the Champy technique are classified as relative stability methods. These techniques allow for some movement at the fracture site, which can promote healing by maintaining blood supply to the cortical bone.

Biologic Fixation

  • New Paradigm:
    • Biologic fixation represents a shift in fracture treatment philosophy, emphasizing that absolute stability is not always beneficial. Allowing for some movement at the fracture site can enhance blood supply and promote healing.
  • Improved Blood Supply:
    • Not pressing the plate against the bone helps maintain blood supply to the cortical bone and prevents the formation of early temporary porosity, which can be detrimental to healing.
Unicystic Ameloblastoma
Oral and Maxillofacial Surgery

Unicystic Ameloblastoma

Unicystic ameloblastoma is a specific type of ameloblastoma characterized by a single cystic cavity that exhibits ameloblastomatous differentiation in its lining. This type of ameloblastoma is distinct from other forms due to its unique clinical, radiographic features, and behavior.

Characteristics of Unicystic Ameloblastoma

  1. Definition:

    • Unicystic ameloblastoma is defined as a single cystic cavity that shows ameloblastomatous differentiation in the lining.

  2. Clinical Features:

    • More than 90% of unicystic ameloblastomas are found in the posterior mandible.
    • They typically surround the crown of an unerupted mandibular third molar and may resemble a dentigerous cyst.

  3. Radiographic Features:

    • Appears as a well-defined radiolucent lesion, often associated with the crown of an impacted tooth.

  4. Histopathology:

    • There are three types of unicystic ameloblastomas:
      • Luminal: The cystic lining shows ameloblastomatous changes without infiltration into the wall.
      • Intraluminal: The tumor is located within the cystic cavity but does not infiltrate the wall.
      • Mural: The wall of the lesion is infiltrated by typical follicular or plexiform ameloblastoma. This type behaves similarly to conventional ameloblastoma and requires more aggressive treatment.

  5. Recurrence Rate:

    • Unicystic ameloblastomas, particularly those without mural extension, have a low recurrence rate following conservative treatment.

Treatment of Ameloblastomas

  1. Conventional (Follicular) Ameloblastoma:

    • Surgical Resection: Recommended with 1.0 to 1.5 cm margins and removal of one uninvolved anatomic barrier.
    • Enucleation and Curettage: If used, this method has a high recurrence rate (70-85%).

  2. Unicystic Ameloblastoma (Without Mural Extension):

    • Conservative Treatment: Enucleation and curettage are typically successful due to the intraluminal location of the tumor.

  3. Unicystic Ameloblastoma (With Mural Extension):

    • Aggressive Treatment: Managed similarly to conventional ameloblastomas due to the infiltrative nature of the mural component.

  4. Intraosseous Solid and Multicystic Ameloblastomas:

    • Mandibular Excision: Block resection is performed, either with or without continuity defect, removing up to 1.5 cm of clinically normal bone around the margin.

  5. Peripheral Ameloblastoma:

    • Simple Excision: These tumors are less aggressive and can be treated with simple excision, ensuring a rim of soft tissue tumor-free margins (1-1.5 cm).
    • If bone involvement is indicated by biopsy, block resection with continuity defect is preferred.

  6. Recurrent Ameloblastoma:

    • Recurrences can occur 5-10 years after initial treatment and are best managed by resection with 1.5 cm margins.
    • Resection should be based on initial radiographs rather than those showing recurrence.