INBDE practice questions: FK1 — Development, structure and function

Answer A: It sits within the labelled target range for a mechanical mitral valve

Warfarin's approved labeling sets a target INR of 2.5 with a range of 2.0 to 3.0 for venous thromboembolism and atrial fibrillation, and a target of 3.0 with a range of 2.5 to 3.5 for a mechanical mitral valve and caged-ball or caged-disk valves. His 3.2 is inside the range his valve calls for. B applies the atrial fibrillation range to every patient, which is the error the colleague made. C invents a threshold above the labelled range. D discards a standardised ratio designed precisely to make results comparable between laboratories. The reasoning point is narrower than it looks: an INR is a value you read against the indication, and it is a recent value that counts.

Common trap: Carrying one remembered INR range into a patient whose indication has another.

Source: Warfarin sodium tablets, FDA-approved labeling (DailyMed)

Answer B: A prolonged aPTT with a normal PT and platelet count

Haemophilia A is factor VIII deficiency and haemophilia B is factor IX deficiency, and both factors sit in the intrinsic limb — XII, XI, IX, VIII — which is measured by aPTT. Both therefore prolong aPTT while PT and the platelet count stay normal, because the extrinsic limb of tissue factor and factor VII is untouched and platelets are not the problem. A prolongs the wrong test and adds a platelet defect that does not belong. C describes both limbs failing, which points to a common-pathway or multi-factor problem such as liver disease rather than to a single factor deficiency. D describes a platelet disorder, whose bleeding is superficial and immediate rather than the deep, delayed bleeding of a factor deficiency.

Common trap: Assuming a severe bleeding disorder must disturb every coagulation test.

Source: Little & Falace's Dental Management of the Medically Compromised Patient

Answer C: With beta receptors blocked, epinephrine acts mainly on alpha-1 and reflex slows the rate

Epinephrine acts at alpha-1, beta-1 and beta-2 receptors: alpha-1 constricts vessels, beta-1 raises rate and contractility, and beta-2 dilates skeletal-muscle vessels. When a non-selective beta-blocker removes both beta actions, the injected epinephrine acts mainly on alpha-1, so blood pressure rises and the baroreceptor reflex slows the heart — the two findings in the vignette. A describes the beta-2 dilation that the blocker has removed and predicts the wrong pressure direction. B misassigns the drug's target: a beta-blocker does not block alpha-1, and if it did the pressure would not have risen. D keeps only the receptor that is blocked and predicts a fast pulse, which is the opposite of what was measured. Cartridge limits are set elsewhere.

Common trap: Treating epinephrine as a purely beta drug and missing the unopposed alpha-1 effect.

Source: Malamed, Handbook of Local Anesthesia

Answer C: Renally cleared drugs accumulate, so dose or interval must be adjusted

An eGFR of 60 or more is in the normal range, below 60 may mean kidney disease, and 15 or less is kidney failure, so 38 places her in the middle band. For dentistry this is first a drug-clearance problem: renally cleared drugs accumulate as filtration falls, so the dose is reduced or the interval lengthened. A ignores that many dental drugs and their metabolites leave by the kidney. B is arbitrary, since the pathway of clearance, not the drug class, decides. D reverses the direction and would make accumulation worse. Two further thoughts belong with her number: NSAIDs deserve caution because prostaglandins help maintain renal blood flow, and the calcium and vitamin D axis is disturbed at this level.

Common trap: Treating a reduced eGFR as an antibiotic question rather than a clearance question.

Source: NIDDK — Chronic Kidney Disease Tests & Diagnosis

Answer C: Give 15 to 20 grams of fast carbohydrate and recheck in 15 minutes

For many people with diabetes a low reading means below 70 mg/dL, and the response is the 15-15 rule: 15 to 20 grams of glucose or fast carbohydrate, recheck after 15 minutes, and repeat if still low. He has taken insulin without food, which is the classic dental-appointment setup, and he is conscious and able to swallow, so the oral route is available and fastest. A reserves the right drug for the wrong patient: glucagon by injection or nasal spray is for severe hypoglycaemia, meaning someone who cannot treat themselves. B treats the episode as a faint and leaves the glucose uncorrected. D withholds the one thing he can safely take, which applies to an unresponsive patient.

Common trap: Escalating to glucagon in a patient who is still able to swallow.

Source: NIDDK — Low Blood Glucose (Hypoglycemia)

Answer A: Total the acetaminophen across every product against the 4,000 mg limit

The stated maximum total in 24 hours is 4,000 mg for adults and children 12 and older, too much can cause liver failure and death, and severe liver damage may occur in someone having three or more alcoholic drinks a day while using it. Because acetaminophen sits inside many prescription combination products and many over-the-counter ones, totalling the daily dose across everything she takes is the clinical skill. B assumes over-the-counter strength means a safe total, which is exactly how the limit is exceeded. C is factually wrong here — both products contain the same drug, which is the whole problem. D confines a whole-person daily maximum to one package. The current guideline puts NSAIDs, with or without acetaminophen, first for most adults.

Common trap: Counting only the tablets that carry acetaminophen in the name on the box.

Source: FDA acetaminophen safe-use guidance

Answer D: Pulp carries only A-delta and C fibres, with no proprioceptors to map the pain

Dental pulp contains only A-delta and C fibres and no proprioceptors, so pulpal pain is poorly localised and patients routinely name the wrong tooth or the opposing arch; many afferents also converge on the same second-order neurons in the trigeminal nucleus. Cold pain that lingers for a minute points to C fibres firing in the lower molar, which is the tooth to investigate. A overstates referral: odontogenic pain almost never crosses the midline, and this referral is within one side. B assumes a localising ability the pulp does not possess. C dismisses a negative percussion test that is informative — once inflammation reaches the periapical tissues, periodontal ligament mechanoreceptors let the patient point precisely and reproduce pain on biting.

Common trap: Trusting the patient's finger over the pulp's lack of proprioceptive innervation.

Source: Malamed, Handbook of Local Anesthesia

Answer C: The mental foramen projected over the premolar apex on this particular film

The mental foramen lies on the buccal surface of the mandible near the premolar apices, and on a two-dimensional periapical film it projects over the root as a round radiolucency that imitates periapical disease. Two findings settle it here: the tooth is intact and unrestored, and it responds normally to cold, so the pulp is vital. A and B both fail on that single point, because a granuloma and a radicular cyst are sequelae of pulpal necrosis and this pulp is alive. D invents a lesion the film's location does not support and, like A and B, converts a normal landmark into pathology. Confirm with pulp testing and, if doubt remains, a second film at a different horizontal angle.

Common trap: Reading a round radiolucency at an apex as disease before testing whether the pulp is alive.

Source: Netter's Head and Neck Anatomy for Dentistry

Answer A: Take a second periapical of the tooth at a different horizontal angle

The zygomatic process of the maxilla casts a radiopaque "U" over the maxillary molar roots, and changing the horizontal angle separates the two possibilities geometrically: a superimposed structure shifts relative to the root, while a lesion attached to the apex moves with it. B spends a three-dimensional study on a question a second two-dimensional film answers, in a tooth whose pulp already responds normally. C takes tissue from what is almost certainly normal bone. D turns a cheap, immediate discriminator into six months of uncertainty and adds no new geometry, because repeating the same projection reproduces the same superimposition. Pulp testing and a second angle precede calling any shadow a lesion.

Common trap: Escalating to advanced imaging or to tissue when a change of horizontal angle answers the question.

Source: Netter's Head and Neck Anatomy for Dentistry

Answer D: Disc displacement without reduction with limited opening on the right side

Under the DC/TMD criteria, limited opening is a maximum assisted opening of less than 40 mm including the vertical incisal overlap, and 33 mm meets that threshold. A click that persists with normal opening is disc displacement with reduction, so A ignores the two findings that changed: the click disappeared and opening became restricted, meaning the condyle can no longer translate past the disc. That is the closed lock. B cannot account for a click that stopped, and deviation towards the restricted side indicates reduced translation on that side rather than muscle pain alone. C describes the opposite mechanical failure, in which the condyle has translated anterior to the eminence and cannot return, leaving the patient unable to close.

Common trap: Keeping the old "with reduction" label after the click has disappeared and opening has become limited.

Source: DC/TMD — Diagnostic Criteria for Temporomandibular Disorders