MFDS Oral Surgery 2

Question 1

A patient presents with a swelling in the floor of the mouth that is fluctuant, translucent blue, and recurrent. It collapses on aspiration and refills. What is the most likely diagnosis?

Accepted Answer

Ranula

Answer

A ranula is a mucous extravasation cyst or retention cyst arising from the sublingual gland. It presents as a fluctuant, translucent blue swelling in the floor of the mouth that may recur after aspiration. A simple ranula is confined to the floor of the mouth; a plunging ranula extends below the mylohyoid muscle into the neck. Definitive treatment usually requires excision of the sublingual gland.

Question 2

What are the boundaries of the 'anatomical snuffbox' and which artery is at risk during surgical procedures in this region?

Accepted Answer

Bounded by the tendons of abductor pollicis longus/extensor pollicis brevis and extensor pollicis longus; the radial artery passes through its floor

Answer

The anatomical snuffbox is bounded laterally by the tendons of abductor pollicis longus and extensor pollicis brevis, and medially by the tendon of extensor pollicis longus. The radial artery crosses its floor, and the cephalic vein crosses superficially. While not directly related to oral surgery, knowledge of upper limb anatomy is tested in MFDS Part 1 as part of general surgical anatomy.

Question 3

Which nerve is most commonly damaged during a sagittal split osteotomy of the mandible, and what are the typical symptoms?

Accepted Answer

The inferior alveolar nerve, causing altered sensation (numbness or paraesthesia) of the lower lip, chin, and teeth on the affected side

Answer

The inferior alveolar nerve is at greatest risk during bilateral sagittal split osteotomy (BSSO) because the osteotomy cuts pass in close proximity to, or directly over, the nerve canal within the mandibular body. Damage results in altered sensation (hypoaesthesia, paraesthesia, or anaesthesia) of the lower lip, chin, and mandibular teeth. The incidence of temporary IAN disturbance ranges from 30-85%, with permanent damage in approximately 3-5% of cases.

Question 4

A 45-year-old patient on long-term bisphosphonate therapy for osteoporosis requires extraction of a non-restorable lower molar. What is the primary concern and how should it be managed?

Accepted Answer

Risk of medication-related osteonecrosis of the jaw (MRONJ) — assess risk factors, consider antibiotic prophylaxis, perform atraumatic extraction, and achieve primary closure

Answer

Bisphosphonates inhibit osteoclast activity and reduce bone turnover, increasing the risk of medication-related osteonecrosis of the jaw (MRONJ) following invasive dental procedures. Management includes assessing the patient's MRONJ risk (duration and route of bisphosphonate therapy, other risk factors), providing prophylactic antibiotics, performing the extraction as atraumatically as possible, achieving primary soft tissue closure, and close follow-up monitoring.

Question 5

What is the most appropriate management for a displaced and mobile zygomatic arch fracture causing trismus?

Accepted Answer

Closed reduction using a Gillies temporal approach with elevation of the depressed fragment

Answer

A displaced zygomatic arch fracture causing trismus (due to impingement on the coronoid process of the mandible) is typically reduced using the Gillies temporal approach. An incision is made behind the hairline in the temporal region, an elevator is passed beneath the temporalis fascia and deep to the arch, and the depressed fragment is lifted outward. This closed technique avoids facial scarring and is effective for isolated arch fractures.

MFDS Part 1 Practice Test

MFDS Part 1 Practice Test

MFDS Oral Surgery 2