management of impacted third molars third

MANAGEMENT OF IMPACTED THIRD MOLARS AND UNERUPTED TEETH

Dr. Otasowie D. Osunde, BDS, FWACS, FAOCMF
Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, University of Calabar, Calabar

OUTLINE

  • Definitions

  • Epidemiology

  • Aetiology

  • Classification of Third Molar Impaction

  • Indications and Contraindications for Surgical Extraction

  • Pre-operative Assessment

  • Surgical Technique

  • Complications

DEFINITIONS

  • Impacted Tooth:

    • An impacted tooth is one that follows an abortive path of eruption and fails to reach a proper functional location in the mouth.

    • This tooth may become impacted within the alveolar process or may be found in heterotrophic sites such as:

    • Sinus cavities

    • Nasal cavities

    • Mandibular ramus

    • Inferior border of the mandible

  • Unerupted Tooth:

    • A tooth that is in the process of eruption and is likely to erupt based on clinical and radiographic assessment.

  • Embedded Tooth:

    • The term "embedded" is occasionally used interchangeably with the term impacted.

EPIDEMIOLOGY

  • The mandibular third molar is the most commonly impacted tooth, followed by:

    • Maxillary canine

    • First permanent molars

  • Variation in prevalence of impacted mandibular third molars by location:

    • Developed countries: 18-32%

    • Kenya: 15.8%

    • South-Western Nigeria: 9.2%

    • Calabar, South-South Nigeria: 4.7% prevalence for impacted lower third molars.

  • Eruption time for mandibular third molars typically occurs between the ages of 18 and 24 years.

  • Higher prevalence of impacted mandibular third molars in females as compared to males.

AETIOLOGY

  • Several theories explaining the reasons for third molar impaction:

    • Mendelian Theory (Hereditary Theory):

    • This theory postulates the genetic transmission of small jaws (often from the mother) and large teeth (often from the father), which results in inadequate space for the eruption of all teeth.

    • Orthodontic Theory:

    • Any disturbance in the normal position of earlier erupting teeth may cause malposition, potentially interfering with the normal mesial drift and leading to impaction.

    • Phylogenetic Theory (Nordine, 1943):

    • Suggests that gradual evolutionary reduction in mandible size has made it too small to accommodate third molars, the last teeth to erupt.

  • Begg (1954) Perspective:

    • Claimed that insufficient forward movement of the dentition due to reduced interproximal attrition from dietary changes led to insufficient space for third molars.

    • The change from a coarse diet to a refined one necessitated less chewing, resulting in minimal jaw growth.

  • Bjork (1956):

    • Established that third molar impaction correlated with diminished growth potential, indicating downward growth patterns rather than mesial directional growth.

  • Currently accepted explanation:

    • A combination of genetic and environmental factors leads to impacted wisdom teeth.

    • There is a hereditary component where large teeth on smaller jaws become aggravated due to influences that inhibit maximal jaw growth.

CAUSES OF TOOTH IMPACTION

  • Local Causes Include:

    1. Obstruction on the eruption pathway due to:

    • Irregular positioning of adjacent teeth.

    • Density of surrounding bone.

    1. Lack of space in the dental arch caused by:

    • Overcrowding.

    • Presence of supernumerary teeth.

    1. Ankylosis of primary or deciduous teeth.

    2. Ectopic position of the tooth bud.

    3. Dilacerated roots.

    4. Associated soft tissue or bony lesions.

  • Systemic Causes Include:

    1. Prenatal causes possibly linked to heredity.

    2. Postnatal causes:

    • Rickets

    • Anaemia

    • Tuberculosis

    • Congenital syphilis

    • Malnutrition

    1. Endocrine disorders resulting in lack of osteoclastic activity, associated with disorders of the thyroid, parathyroid, and pituitary glands.

    2. Certain hereditary-linked disorders, e.g.,

    • Down’s syndrome

    • Hurler’s syndrome

    • Osteopetrosis

    • Cleidocranial dysostosis

    • These conditions prevent resorption of overlying bone.

CLASSIFICATION OF THIRD MOLAR IMPACTION

WINTER’S CLASSIFICATION

  • Based on spatial relationship of the impacted tooth to the vertical axis of the second molar.

    • Types of Impaction:

    1. Mesioangular

    2. Distoangular

    3. Horizontal/Transverse

    4. Vertical

  • Imaginary Lines Defined by Winter:

    • White Line:

    • Drawn along occlusal surfaces of erupted mandibular molars extending posteriorly to the anterior border of the ramus.

    • Amber Line:

    • Drawn from the crest of the interdental septum between mandibular first and second molars, indicating the amount of alveolar bone enclosing the tooth.

    • Red Line:

    • Perpendicular to the amber line, directed to the imaginary point of application (cemento-enamel junction) of an elevator on the impacted third molar.

PELL AND GREGORY CLASSIFICATION

Spatial Relationship to Second Molar and Ramus

  • Three Classes:

    1. Class 1:

    • Space between distal surface of the second molar and ascending ramus is greater than the mesiodistal width of the impacted third molar.

    1. Class 2:

    • Space is less than the mesiodistal width of the impacted third molar.

    1. Class 3:

    • All or most of the impacted third molar entries within the ramus.

Depth Classification

  • Positions Defined:

    1. Position A:

    • Highest position of tooth is level with or above occlusal plane.

    1. Position B:

    • Highest position of impacted tooth is below occlusal plane, but above cervical line of second molar.

    1. Position C:

    • Highest position below cervical line of second molar.

INDICATIONS AND CONTRAINDICATIONS FOR SURGICAL EXTRACTION

Indications

  • Situations necessitating extraction:

    1. Over history of infection, including pericoronitis.

    2. Unrestorable caries.

    3. Non-treatable pulpal or periapical diseases.

    4. Cellulitis, abscess, and osteomyelitis.

    5. Periodontal diseases.

    6. Orthodontic abnormalities.

    7. Prophylactic removal in the presence of specific medical and surgical conditions.

    8. Internal/external tooth resorption.

    9. Pain directly related to third molars.

    10. Teeth positioned in the line of bony fractures or impeding trauma management.

    11. Fractured teeth.

    12. Diseases of follicle, including cysts or tumors.

    13. Impeding orthognathic or reconstructive jaw surgeries.

    14. Suitable teeth as donor transplants.

Contraindications

  • Few absolute contraindications:

    1. Active infection (e.g., pericoronitis).

    2. Deeply placed asymptomatic teeth.

    3. Potential damage to adjacent structures.

    4. Compromised patient health status.

    5. Adequate space for eruption.

    6. When a patient refuses surgery.

PRE-OPERATIVE ASSESSMENT

Clinical Assessment

  • Factors to evaluate:

    • Built of the patient.

    • Extent of mouth opening.

    • Size of the tongue.

    • Psychological disposition of the patient.

Radiological Assessment

  • Critical evaluations include:

    • Type of impaction (mesioangular, distoangular, horizontal, vertical).

    • Depth of impaction.

    • Root morphology (bulbous, conical, dilacerated, etc.).

    • Density of surrounding bone.

    • Presence of ankylosis.

    • Relationship to the inferior alveolar neurovascular bundle.

ASSESSMENT OF DIFFICULTY

Pederson Difficulty Index

  • Classification and Values:

    • Spatial Relationship (Position of Molar):

    • Mesioangular: 1

    • Horizontal: 2

    • Vertical: 3

    • Distoangular: 4

  • Relative Depth:

    • Position A: 1

    • Position B: 2

    • Position C: 3

  • Ramus Relationship/Space Available:

    • Class 1: 1

    • Class 2: 2

    • Class 3: 3

  • Difficulty Index Total:

    • Very difficult: 7-10

    • Moderately difficult: 5-6

    • Slightly difficult: 3-4

SURGICAL TECHNIQUE

  • Maintain strict aseptic techniques.

  • Administer local anaesthesia.

  • Procedure Outline:

    • Incision and flap design.

    • Reflection of mucoperiosteal flap.

    • Bone removal via buccal guttering technique with a rotatory handpiece under constant irrigation.

    • Section the tooth if indicated.

    • Use elevators for extraction.

    • Deliver the tooth.

    • Perform socket toileting.

    • Ensure haemostasis.

    • Closure of the incision: apply sutures.

    • Prescribe medications.

    • Provide post-extraction instructions.

    • Schedule follow-ups.

COMPLICATIONS

  • Infectious Complications:

    • Pain, swelling, trismus.

  • Neurologic Complications:

    • Injury to inferior alveolar and lingual nerves.

  • Other Complications Include:

    • Haemorrhage.

    • Fractured tooth.

    • Mandibular fractures.

    • Dry socket (alveolar osteitis).

    • Periodontal pocket distal to the lower second molar.

    • Delayed healing.

    • Osteomyelitis.