Impacted Third Molars: Classification and Removal Guide

An impacted third molar — a wisdom tooth — is one that cannot erupt into its proper position because it is blocked by bone, gum or the tooth in front of it. Lower wisdom teeth are the most commonly impacted teeth in the human mouth, and their removal is the most frequent oral surgical procedure.

This matters because impacted wisdom teeth cause repeated infections (pericoronitis), decay and gum damage to the neighbouring second molar, and cysts in the jaw. Classifying the impaction precisely tells the surgeon how difficult the removal will be, how long it takes and what complications to watch for.

Key Concepts

• Winter's classification (angulation): mesioangular (tilted toward the second molar — most common), distoangular (tilted away), horizontal (lying sideways), vertical (upright but stuck).
• Pell and Gregory ramus relationship: Class I (enough space between second molar and jaw ramus), Class II (partially covered by ramus), Class III (fully inside the ramus).
• Pell and Gregory depth: Position A (crown level with the second molar), Position B (between the chewing surface and neck of the second molar), Position C (below the neck — deepest and hardest).
• IAN proximity: how close the tooth roots sit to the inferior alveolar nerve; close roots raise the risk of lip numbness after surgery.
• Dry socket (alveolar osteitis): loss of the blood clot after extraction, causing severe pain 2 to 4 days later; more common with wisdom teeth.

How It Works

A surgical wisdom-tooth removal follows these steps:

1. Assessment: the x-ray (ideally a CBCT scan for nerve proximity) classifies the impaction by angulation, ramus relationship and depth.
2. Anaesthesia and flap: after numbing, a gum flap is raised to expose the bone covering the tooth.
3. Bone removal: the bone over the crown is trimmed with a bur under water cooling.
4. Sectioning: horizontal or mesioangular teeth are cut into two or three pieces so each piece delivers through a smaller opening.
5. Delivery and cleaning: the pieces are elevated out, the socket is washed, and any infected tissue is removed.
6. Closure: the flap is stitched back; dissolvable stitches are usual.

Worked Example

A 24-year-old patient has a painful lower left wisdom tooth with repeated infections:

1. Classification from the panoramic x-ray: mesioangular, Pell and Gregory Class II, Position B — a moderately difficult impaction.
2. The roots appear 2 mm clear of the nerve canal on CBCT, so the numbness risk is low.
3. Surgery under local anaesthesia takes 25 minutes: bone trimmed, crown sectioned from the roots, pieces delivered separately.
4. Healing: mild swelling peaks at 48 hours and settles by day 5; no dry socket, no nerve symptoms.
5. Result: the source of repeated infections is gone, the second molar is undamaged, and the patient returns to normal diet in a week.

Common Misconceptions

• "All wisdom teeth must be removed." Fully erupted, healthy, cleanable wisdom teeth can stay; only diseased, damaging or uncleanable ones need removal.
• "Removal always damages the nerve." With CBCT planning and careful technique, permanent nerve injury occurs in well under 1 percent of cases.

Real-World Applications

• Oral surgery practice: wisdom-tooth removal is the core daily procedure of most oral surgeons.
• Orthodontics: impacted third molars are assessed before braces to prevent late crowding pressure.
• Emergency care: acute pericoronitis is managed with cleaning and antibiotics before planned removal.
• Pathology prevention: removing impacted teeth early prevents cysts that can hollow large areas of jawbone.

Impacted third molars are a rite of passage in oral surgery: classify the impaction, respect the nerve, section the tooth instead of fighting it, and a feared procedure becomes a routine 30-minute appointment with a smooth week of healing.