Mandibular Third Molar Impaction - Causes, Complications, Diagnosis and Treatment

What Is Impaction?

Impaction is a condition in which a tooth fails to erupt fully out of the gums within the developmental period. Among the third molars, lower mandibular molars have a high chance of being impacted compared to upper molars. According to studies, nearly 75 % of the mandibular molars are impacted in adults.

What Causes the Impaction of Mandibular Third Molars?

The most significant reasons for impaction are as below;

1. Insufficient development of the retromolar area (space behind the wisdom tooth) - Due to lack of space, the third molars fail to erupt into the dental arch.

2. Angulated roots.

3. Hereditary factors.

4. Malposition of the tooth germ.

5. Lack of proper eruption force.

How Are the Mandibular Third Molars Classified?

Mandibular third molar impaction is classified depending on;

1. Depth of impacted lower molar to occlusal plane (classification of Pell and Gregory).

2. The angle formed between the longitudinal axis of second and third molars (Winter’s classification).

3. The distance from the ramus to the distal surface of the second molar.

This classification of mandibular third molar impaction enables the doctor to choose the appropriate treatment and to assess the difficulty in removing the impacted tooth, thereby reducing the possible complications.

What Are the Indications for the Removal of Impacted Third Molar?

The main indications for the removal of the mandibular third molar include;

• Pain due to pericoronitis.

• Non-restorable carious lesions.

• Periapical abscess.

• Resorption of the adjacent tooth.

• Malposition of the tooth causing inflammation of soft tissues.

• For orthodontic and prosthodontic treatments.

• Crowding of the dental arch.

• Cysts and tumors associated with impacted teeth.

• Impacted molars contributing to chronic facial pain.

If the impacted tooth is totally asymptomatic, there is no need for its surgical removal.

How Can We Diagnose an Impacted Third Molar?

Proper assessment of the impacted mandibular third molar is vital in order to eliminate the complications during and after the removal of teeth. It is done by physical and radiographic evaluation.

Physical examination is done mainly by evaluating the mouth opening, inspection and palpation of the temporomandibular joint, mobility of the mandible, the appearance of soft tissue over the impacted tooth, shape and size of the tongue, and mobility of cheeks and lips.

Radiographic assessment grants an idea about root morphology, the density of the surrounding bone, its relation with the second molar, relation with ramus and body of mandible, helps to determine whether the tooth is buccally or lingually inclined and relation with alveolar nerve and vessels.

For many years periapical radiographs were used to access jaws during surgery. But the poor quality of the image is the major shortcoming of this method. Poor quality of images does not allow the proper identification of the mandibular canal, which is a matter of concern. Panoramic radiographs allow a large area to be viewed in a periapical view. Some major drawbacks are the presence of phantom images and lower image resolution.

Cone-beam computed tomography (CBCT) allows a three-dimensional view of mandibular third molars and adjacent anatomical structures. After the introduction of CBCT, the inferior alveolar nerve injury during the impaction surgery has reduced drastically.

How to Treat an Impacted Third Molar?

The primary treatment for the impacted third molar which is responsible for discomfort in patients is surgical removal. The treatment plan for the management of the impacted third molar mainly depends on the physical evaluation, radiographic assessment, main complaint, history of the patient, diagnosis, and prognosis. All these components play a pivotal role in devising a proper treatment plan for the surgical removal of an impacted third molar.

The first step in the surgical removal of the mandibular third molar is anesthetizing the site of surgery. In most cases, inferior alveolar nerve block, buccal nerve block, and local infiltration are generally given in order to anesthetize and for hemostasis (stop bleeding).

For the surgical removal of an impacted third molar, there are mainly two intraoral approaches and one extraoral method. The steps involved in the removal of the third molar are;

1. Flap elevation (removal of gum tissues).

2. Removal of the bone surrounding the impacted tooth.

3. Removal of the impacted tooth.

4. After the successful removal of the tooth, the next step is the debridement of the socket. The bone debris and tissue are removed.

5. The next step is wound closure. Before the wound closure bleeding should be completely arrested. If bleeding is not properly arrested, it can lead to post-surgical complications like a hematoma (collection of blood outside the blood vessels). So proper arresting of bleeding is essential for the prevention of post-surgical complications. The flap is positioned back to its original position, and a suture is placed on the distal end of the second molar.

6. After the successful removal of the tooth, post-operative instructions and medications are given to the patient.

What Are the Complications That Can Occur During the Surgery?

The complications that can occur during the surgical removal of an impacted third molar is classified into;

1. Intraoperative.

2. Post-operative.

The intraoperative complications include;

• Damage to the facial artery or veins.

• Damage to lingual nerve and inferior alveolar nerve.

• Fracture of the mandible.

• Injury to the adjacent tooth.

• Bone necrosis due to excessive heat generated from the bur.

• Accidental burns.

• Soft tissue damage.

• Breakage of the bur.

• Displacement of the entire tooth.

The post-operative complications mainly include;

• Edema.

• Pain.

• Trismus (restriction to jaw movement).

• Hemorrhage (bleeding).

• Dry socket.

• Hematoma.

• Pain during swallowing.

• Temporomandibular joint complications.

• Osteitis (inflammation of the bone).

Damage to the lingual nerve can lead to numbness of the ipsilateral anterior two-thirds of the tongue, and disturbance in taste and damage to the inferior alveolar nerve can cause numbness and pain in the gingival region posterior to premolars, mental area, and lower lip. This nerve damage will affect speech, eating, and drinking.

What Is a Dry Socket?

Dry socket or alveolar osteitis is one of the serious and most common complications that can occur after the removal of an impacted third molar. It mainly occurs due to the exposure of sockets to foreign particles like food or the tongue. This exposure prevents the formation of blood clots in that area or the formation of healing epithelium. Food particles collected at the site of surgery can ferment, which in turn can lead to halitosis (bad breath), unpleasant pain, and pain throughout the jaw. The basic treatment for dry sockets is to irrigate out food particles using saline and fill the socket with a medicament. The bony spicules also should be removed, if any. If possible, under anesthesia, the necrosed tissue is removed, and fresh bleeding should be induced. By doing so, vascular supply is re-established in that area, and new healthy tissues are formed that ensure proper healing. In some cases, mild suturing of the area is done in order to retain the medicament.

Conclusion:

Following the post-operative instructions properly and routine dental checkups can help prevent the complications after the impaction surgery to an extent. If any discomfort is felt during and after surgery, it should be reported immediately to the doctor in order to prevent further worsening of the condition.