MJDF Oral Medicine and Surgery 2 — Questions and Answers
Question 1: What is the trigeminal nerve's sensory distribution relevant to dental anaesthesia, and which division supplies the mandibular teeth?
- The ophthalmic division (V1) supplies the mandibular teeth
- The mandibular division (V3) supplies the mandibular teeth via the inferior alveolar nerve; V2 (maxillary) supplies the maxillary teeth; V1 (ophthalmic) supplies the forehead and upper face (Correct answer)
- The facial nerve (CN VII) supplies all dental sensation
- The glossopharyngeal nerve (CN IX) supplies the mandibular teeth
Correct answer: The mandibular division (V3) supplies the mandibular teeth via the inferior alveolar nerve; V2 (maxillary) supplies the maxillary teeth; V1 (ophthalmic) supplies the forehead and upper face
The trigeminal nerve (CN V) has three divisions: V1 (ophthalmic) supplies sensation to the forehead, upper eyelid, and nose dorsum; V2 (maxillary) supplies the mid-face, maxillary teeth (via posterior, middle, and anterior superior alveolar nerves), and palate (via greater and lesser palatine and nasopalatine nerves); V3 (mandibular) supplies the lower face, mandibular teeth (via the inferior alveolar nerve), lower lip and chin (mental nerve), tongue (lingual nerve — general sensation), and buccal mucosa (long buccal nerve). V3 is the only division with motor fibres (muscles of mastication).
Question 2: A patient presents with a unilateral facial swelling causing elevation of the ear lobe, with pain and trismus. The overlying skin is normal in colour. What is the most likely diagnosis?
- Mumps (bilateral parotitis)
- Acute bacterial parotitis — infection of the parotid gland presenting with painful swelling anterior to and below the ear, with possible pus exuding from the parotid duct orifice (Stensen's duct) opposite the upper second molar (Correct answer)
- Angioedema
- Temporomandibular joint arthritis
Correct answer: Acute bacterial parotitis — infection of the parotid gland presenting with painful swelling anterior to and below the ear, with possible pus exuding from the parotid duct orifice (Stensen's duct) opposite the upper second molar
Acute bacterial parotitis presents with painful unilateral swelling of the parotid gland (anterior to the ear, lifting the ear lobe), trismus (due to proximity of the gland to the masseter and medial pterygoid muscles), and pyrexia. Pus may be expressed from Stensen's duct orifice on the buccal mucosa opposite the upper second molar. It commonly occurs in dehydrated, post-operative, or immunocompromised patients. The most common organism is Staphylococcus aureus. Management includes IV fluids (rehydration), empirical IV antibiotics (flucloxacillin), sialagogues, and surgical drainage if an abscess forms.
Question 3: What are the clinical features that distinguish trigeminal neuralgia from other causes of facial pain?
- Continuous dull ache lasting for days, affecting the forehead
- Sudden, severe, brief (seconds to minutes) electric shock-like pain in the distribution of one or more divisions of the trigeminal nerve, triggered by light touch to specific trigger zones (e.g., washing face, shaving, eating), with pain-free intervals between attacks (Correct answer)
- Throbbing pain behind the eye with tearing and nasal congestion
- Bilateral face pain with associated jaw clicking and limited mouth opening
Correct answer: Sudden, severe, brief (seconds to minutes) electric shock-like pain in the distribution of one or more divisions of the trigeminal nerve, triggered by light touch to specific trigger zones (e.g., washing face, shaving, eating), with pain-free intervals between attacks
Trigeminal neuralgia (tic douloureux) is characterised by paroxysmal, severe, stabbing or electric shock-like pain lasting seconds to 2 minutes, strictly following the distribution of one or more trigeminal divisions (V2 and/or V3 most commonly). Key features: triggered by innocuous stimuli to specific trigger zones (e.g., nasolabial fold, lip, chin), pain-free refractory period after an attack, clustering of attacks, and unilateral. The pain is so severe patients may avoid eating, washing, or shaving. First-line treatment is carbamazepine. MRI is mandatory to exclude secondary causes (e.g., cerebellopontine angle tumour).
Question 4: A le Fort I fracture of the maxilla involves which anatomical structures, and how is it clinically diagnosed?
- It involves only the nasal bones and is diagnosed by nasal bleeding alone
- It is a horizontal fracture separating the tooth-bearing maxilla from the upper facial skeleton, passing through the piriform aperture, lateral maxillary walls, and pterygoid plates; diagnosed by mobility of the upper dental arch when the anterior maxilla is grasped and rocked while stabilising the forehead (Correct answer)
- It involves the orbital floor and is diagnosed by diplopia
- It involves the zygomatic arch only and is diagnosed by a flat cheek
Correct answer: It is a horizontal fracture separating the tooth-bearing maxilla from the upper facial skeleton, passing through the piriform aperture, lateral maxillary walls, and pterygoid plates; diagnosed by mobility of the upper dental arch when the anterior maxilla is grasped and rocked while stabilising the forehead
Le Fort I (Guérin's fracture) is a horizontal fracture separating the entire tooth-bearing maxilla (dentoalveolar segment) from the upper craniofacial skeleton. The fracture line passes through the piriform aperture (nose base), the lateral walls of the maxillary sinuses, and the lower pterygoid plates. Clinical diagnosis: grasp the anterior maxilla with finger and thumb, rock gently while stabilising the forehead/nasal bridge with the other hand — mobility of the upper dental arch alone (without movement of the nose or orbits) confirms Le Fort I. Associated features include bruising in the upper buccal sulcus, posterior open bite, and mobile upper teeth.
Question 5: What are the signs and symptoms of an inferior alveolar nerve injury following dental extraction, and what is the prognosis for recovery?
- Complete motor paralysis of the lower face with no chance of recovery
- Altered sensation (numbness, tingling, or paraesthesia) of the lower lip, chin, and gingiva on the affected side; most neuropraxia-type injuries recover within 6-8 weeks, while neurotmesis (complete nerve transection) may be permanent (Correct answer)
- Only affects taste sensation on the tongue
- Causes visible facial asymmetry and always requires surgical repair
Correct answer: Altered sensation (numbness, tingling, or paraesthesia) of the lower lip, chin, and gingiva on the affected side; most neuropraxia-type injuries recover within 6-8 weeks, while neurotmesis (complete nerve transection) may be permanent
IAN injury manifests as sensory disturbance in its distribution: numbness (anaesthesia), reduced sensation (hypoaesthesia), altered sensation (paraesthesia), or painful sensation (dysaesthesia) of the ipsilateral lower lip, chin, labial gingiva, and mandibular teeth. Prognosis depends on injury severity: neuropraxia (nerve bruising, no structural damage) — full recovery typically within 6-8 weeks; axonotmesis (axon damage, intact sheath) — recovery in 2-6 months; neurotmesis (complete transection) — no spontaneous recovery, may require microsurgical repair. If no recovery at 3 months, referral to an oral surgery specialist for assessment and possible exploration is recommended.
Question 6: When should a dentist suspect and test for diabetes mellitus in a dental patient, and what oral findings may be suggestive?
- Diabetes has no oral manifestations and testing is not the dentist's responsibility
- Suspect diabetes in patients with unexplained periodontal disease disproportionate to local factors, recurrent oral candidiasis, xerostomia, delayed healing, unexplained burning mouth, and bilateral parotid enlargement; test with chairside HbA1c or refer for fasting glucose (Correct answer)
- Diabetes only causes caries and is always obvious from the medical history
- Only test patients who report excessive thirst
Correct answer: Suspect diabetes in patients with unexplained periodontal disease disproportionate to local factors, recurrent oral candidiasis, xerostomia, delayed healing, unexplained burning mouth, and bilateral parotid enlargement; test with chairside HbA1c or refer for fasting glucose
Dentists are well-placed to identify undiagnosed diabetes through oral findings: periodontitis disproportionate to plaque levels (especially in younger patients), multiple periodontal abscesses, recurrent oral candidiasis, xerostomia, delayed healing after extractions, bilateral painless parotid enlargement (sialosis), burning mouth syndrome, and altered taste. The British Society of Periodontology recommends that dental professionals consider screening patients with severe periodontitis. Chairside HbA1c testing or referral for fasting plasma glucose/oral glucose tolerance test enables early diagnosis.
MJDF Oral Medicine and Surgery 2
What is the trigeminal nerve's sensory distribution relevant to dental anaesthesia, and which division supplies the mandibular teeth?