MFDS Oral Surgery — Questions and Answers
Question 1: A patient presents for extraction of a lower third molar. The radiograph shows the roots in close proximity to the inferior alveolar canal. Which sign on the radiograph is the MOST reliable indicator of a true intimate relationship between the tooth roots and the inferior alveolar nerve?
- Darkening of the root at the point of overlap with the canal
- Loss of the lamina dura of the canal wall where the root crosses (Correct answer)
- The root appearing to curve away from the canal
- Widening of the periodontal ligament space
Correct answer: Loss of the lamina dura of the canal wall where the root crosses
Loss (interruption) of the white corticated line of the inferior alveolar canal where the root crosses is the most reliable radiographic sign of a true intimate relationship. Other signs include darkening (increased radiolucency) of the root, deflection of the canal, and narrowing of the canal, but loss of the cortical outline is considered the strongest predictor of nerve injury risk.
Question 2: During surgical removal of an upper first premolar, the root fractures and the apical fragment is displaced into the maxillary sinus. What is the most appropriate initial management?
- Immediately enlarge the socket to retrieve the fragment via a Caldwell-Luc approach
- Inform the patient, prescribe antibiotics and a nasal decongestant, and arrange a referral for surgical retrieval (Correct answer)
- Instruct the patient to blow their nose forcefully to expel the fragment
- Ignore the fragment as it will be absorbed naturally
Correct answer: Inform the patient, prescribe antibiotics and a nasal decongestant, and arrange a referral for surgical retrieval
A root fragment displaced into the maxillary sinus should not be retrieved via the socket as this may enlarge the oroantral communication. The patient should be informed, prescribed antibiotics (amoxicillin) and a nasal decongestant (ephedrine nasal drops), given sinus precautions, and referred for elective surgical retrieval, usually via a Caldwell-Luc approach under general anaesthesia.
Question 3: What is the most appropriate local anaesthetic technique for extraction of a lower first molar in an adult patient?
- Infiltration anaesthesia buccally only
- Inferior alveolar nerve block supplemented with long buccal nerve infiltration (Correct answer)
- Mental nerve block alone
- Topical anaesthesia applied to the gingiva
Correct answer: Inferior alveolar nerve block supplemented with long buccal nerve infiltration
The lower first molar is innervated by the inferior alveolar nerve (pulpal and lingual soft tissue) and the long buccal nerve (buccal soft tissue). An inferior alveolar nerve block anaesthetises the tooth and lingual tissues, while a supplementary long buccal infiltration anaesthetises the buccal gingivae. In some patients, articaine infiltration alone may suffice due to its superior bone penetration, but the IANB plus long buccal is the standard technique.
Question 4: A patient develops a dry socket (alveolar osteitis) three days after extraction of a lower wisdom tooth. Which of the following best describes the pathogenesis and management?
- Bacterial infection of the socket requiring systemic antibiotics and incision and drainage
- Premature loss of the blood clot with exposed bone causing severe pain, managed with irrigation and placement of a sedative dressing such as Alvogyl (Correct answer)
- Allergic reaction to the local anaesthetic requiring antihistamine treatment
- Fracture of the alveolar bone during extraction requiring surgical fixation
Correct answer: Premature loss of the blood clot with exposed bone causing severe pain, managed with irrigation and placement of a sedative dressing such as Alvogyl
Dry socket results from premature lysis of the blood clot, possibly due to excessive fibrinolysis activated by bacterial enzymes. The exposed alveolar bone causes severe, throbbing pain radiating to the ear, with halitosis and a foul taste. Management involves gentle irrigation with warm saline to remove debris and placement of a sedative/antiseptic dressing (e.g., Alvogyl containing butamben, iodoform, and eugenol). Systemic antibiotics are not indicated unless there is spreading infection.
Question 5: Which of the following is an absolute contraindication to dental extractions without specialist consultation?
- Controlled hypertension managed with amlodipine
- Patient currently taking therapeutic doses of warfarin with INR of 3.8 (Correct answer)
- Patient with a history of mild asthma using a salbutamol inhaler
- Patient with well-controlled type 2 diabetes on metformin
Correct answer: Patient currently taking therapeutic doses of warfarin with INR of 3.8
An INR of 3.8 exceeds the safe threshold for dental extractions in primary care (generally INR should be ≤4.0 for simple extractions, but ideally ≤3.5 with local haemostatic measures). At this level, the bleeding risk is significantly elevated and specialist consultation is warranted to balance the risks of haemorrhage against thromboembolism from anticoagulant modification. The other conditions, when well controlled, are managed routinely in general practice.
Question 6: During extraction of an upper canine, the labial plate of bone fractures and remains attached to the periosteum. What is the most appropriate management?
- Remove the bone fragment completely and smooth the remaining bone
- Leave the bone fragment attached to its periosteal blood supply, reposition it, and suture the soft tissues over it (Correct answer)
- Pack the socket with bone wax and leave the fragment in situ
- Refer the patient for immediate bone grafting
Correct answer: Leave the bone fragment attached to its periosteal blood supply, reposition it, and suture the soft tissues over it
When the labial plate fractures but remains attached to the periosteum, the blood supply is maintained. The fragment should be left attached, gently repositioned to its original position, and the soft tissue flap sutured over it. This approach preserves the alveolar bone contour and allows healing. Removing a vascularised fragment unnecessarily creates a bony defect and compromises future prosthetic rehabilitation.
MFDS Oral Surgery
A patient presents for extraction of a lower third molar.
The radiograph shows the roots in close proximity to the inferior alveolar canal.
Which sign on the radiograph is the MOST reliable indicator of a true intimate relationship between the tooth roots and the inferior alveolar nerve?