Which of the following condition shows marked reduction in the amount of dentin, widening of predentin layer, presence of large areas of interglobular dentin and irregular pattern of dentin? (PSC - Lumbini 2083)

# Which of the following condition shows marked reduction in the amount of dentin, widening of predentin layer, presence of large areas of interglobular dentin and irregular pattern of dentin? (PSC - Lumbini 2083)

A. Hypocalcified dentin

B. Regional odontodysplasia

C. Dentin dysplasia

D. Dentinogenesis imperfecta

The correct answer is B. Regional odontodysplasia.

Regional odontodysplasia, commonly referred to as "ghost teeth," is a rare, localized, non-hereditary developmental anomaly affecting both the mesodermal and ectodermal components of the tooth.

The exact histological description provided in the question is the classic hallmark of this condition. Under a microscope, teeth affected by regional odontodysplasia exhibit:

A marked reduction in the amount of dentin.
A significantly widened predentin layer.
The presence of large areas of interglobular (hypocalcified) dentin.
An irregular tubular pattern of dentin (often featuring amorphous or cellular dentin).

Because both the enamel and dentin are extremely thin and poorly mineralized, the teeth appear faint, radiolucent, and "ghost-like" on a radiograph, featuring exceptionally large pulp chambers that often contain pulp stones.

Here is why the other options are incorrect:

Dentinogenesis imperfecta: Characterized clinically by opalescent teeth and radiographically by early obliteration of the pulp chambers and bulbous crowns, rather than the severely widened, shell-like pulps seen in this description.
Dentin dysplasia: Type I presents as "rootless teeth" and Type II presents with "thistle-tube" shaped pulp chambers. Histologically, it features a disorganized "cascading waterfall" or "stream flowing around boulders" pattern of atypical dentin, distinct from the widely widened predentin of ghost teeth.
Hypocalcified dentin: While interglobular dentin is a form of hypocalcified dentin, this is a generic descriptive histological term rather than the specific, syndrome-level developmental disturbance requested by the classic tetrad of signs in the prompt.

Fibrous dysplasia is characterized by all EXCEPT: (PSC - Lumbini 2083)

# Fibrous dysplasia is characterized by all EXCEPT: (PSC - Lumbini 2083)
A. Involvement of several bones
B. Enlargement of the affected bones

C. Associated with non-vital teeth

D. Displacement of teeth

Fibrous dysplasia is a developmental, benign fibro-osseous bone condition characterized by the replacement of normal cancellous bone with cellular fibrous connective tissue and poorly formed woven bone.

To answer this MCQ meticulously, let's evaluate each option based on the clinical, radiographic, and histological behavior of the lesion:

A. Involvement of several bones: True. Fibrous dysplasia can present in three primary clinical patterns: monostotic (involving a single bone), polyostotic (involving multiple bones), and McCune-Albright syndrome (polyostotic involvement with endocrinopathies and café-au-lait pigmentation).
B. Enlargement of the affected bones: True. As the proliferating fibro-osseous mass replaces normal bone architecture, it leads to a slow, painless, and progressive bony expansion, which often results in noticeable facial asymmetry when the maxilla or mandible is involved.
D. Displacement of teeth: True. The expansile nature of the lesion commonly causes bodily displacement or migration of adjacent teeth, disrupting the occlusal plane and leading to malocclusion. (Note: Root resorption is relatively rare, but displacement is a hallmark).
C. Associated with non-vital teeth: False. This is the exception. The teeth involved within or adjacent to a fibrous dysplasia lesion retain their normal neurovascular supply and remain vital. Loss of pulp vitality is typically associated with endodontic pathology, radicular cysts, or aggressive malignancies, rather than a developmental fibro-osseous defect. Pulp vitality testing in a purely fibrous dysplasia-affected segment will yield normal responses.

The first-line drug for acute myocardial infarction in dental emergency is: (PSC - Lumbini 2083)

# The first-line drug for acute myocardial infarction in dental emergency is: (PSC - Lumbini 2083)

A. Nitroglycerin

B. Aspirin

C. Atorvastatin

D. Metoprolol

The correct answer is B. Aspirin.

In a dental emergency setting, the pharmacological priority for an acute myocardial infarction (AMI) is halting the expansion of the coronary thrombus:

Aspirin: This is the definitive first-line therapeutic drug for a suspected AMI. Standard protocol mandates the immediate administration of 160–325 mg of non-enteric-coated, chewable aspirin. It acts as a rapid antiplatelet agent by irreversibly inhibiting the cyclooxygenase-1 (COX-1) enzyme, blocking the synthesis of thromboxane A2. This prevents further platelet aggregation and is the primary chairside intervention proven to reduce patient mortality.

Nitroglycerin: While sublingual Nitroglycerin (0.4 mg) is the first-line emergency drug for angina pectoris, it is not the primary disease-modifying drug for an established infarction. During an AMI, it provides symptomatic pain relief by acting as a vasodilator that reduces venous return (preload) and myocardial oxygen demand, but it does not stop the underlying thrombotic event.

Atorvastatin & Metoprolol: These are critical hospital-administered medications utilized following an MI, but they are not acute, first-line emergency drugs kept in a standard clinical emergency armamentarium.

Which anticoagulant is most commonly monitored using INR? (PSC - Lumbini 2083)

# Which anticoagulant is most commonly monitored using INR? (PSC - Lumbini 2083)

A. Aspirin

B. Heparin

C. Warfarin

D. Clopidogrel

The correct answer is C. Warfarin.

Warfarin is a Vitamin K antagonist whose therapeutic efficacy and bleeding risk must be routinely monitored using the International Normalized Ratio (INR). Antiplatelets (like Aspirin and Clopidogrel) do not require routine INR monitoring.

The first line drug for anaphylaxis is: (PSC - Lumbini 2083)

# The first line drug for anaphylaxis is: (PSC - Lumbini 2083)

A. Diphenhydramine

B. Epinephrine

C. Hydrocortisone

D. Oxygen

The correct answer is B. Epinephrine.

Intramuscular epinephrine (typically 0.3 to 0.5 mg of a 1:1,000 solution injected into the anterolateral thigh) is the absolute first-line drug of choice. It acts as a physiological antagonist to systemic mediators of anaphylaxis, reversing peripheral vasodilation, reducing tissue edema, and inducing bronchodilation.

The first step in any medical emergency is: (PSC - Lumbini 2083)

A. Call for help

B. Assess airway, breathing, circulation (ABC)

C. Administer drugs

D. Start CPR

The correct answer is B. Airway, breathing, circulation (ABC)

Current Basic Life Support (BLS) protocols dictate that upon identifying an unresponsive patient, the immediate first step is to call for help (activate emergency response), followed instantly by the primary assessment of Circulation, Airway, and Breathing (CAB in modern AHA guidelines, historically ABC).

The most common complication of oral surgery is: (PSC - Lumbini 2083)

# The most common complication of oral surgery is: (PSC - Lumbini 2083)

A. Infection

B. Hemorrhage

C. Trismus

D. Nerve Injury

The correct answer is B. Hemorrhage.

While localized infections (such as alveolar osteitis) and trismus are frequent postoperative occurrences, minor to moderate hemorrhage is widely considered the most common immediate complication following routine exodontia and minor oral surgery, requiring proper local hemostatic management.

Dental treatment is safest in patients with stable angina at: (PSC - Lumbini 2083)

# Dental treatment is safest in patients with stable angina at: (PSC - Lumbini 2083)

A. Early morning

B. After lunch

C. Evening

D. Late night

The correct answer is A. Early morning

Scientific Rationale & Clinical Principles

In dental management of patients with cardiovascular diseases—specifically stable angina pectoris—appointment timing is a core component of the Stress Reduction Protocol (SRP).

1. Endogenous Cortisol & Stress Resistance

Peak Cortisol Levels: Endogenous glucocorticoids (cortisol) peak in the early morning hours upon awakening. Higher baseline cortisol levels equip the patient to better tolerate physical and emotional stress without triggering excessive endogenous catecholamine (epinephrine/norepinephrine) surges that increase myocardial oxygen demand.

2. Minimization of Physical and Mental Fatigue

Patients who are scheduled in the early morning are well-rested. As the day progresses, accumulation of daily physical exertion, work-related stress, and prolonged anticipation or anxiety regarding the dental appointment significantly increases sympathetic autonomic tone, lower the ischemic threshold, and predispose the patient to an anginal attack.

3. Reduced Waiting Room Anxiety

Early morning appointments minimize wait times in the clinic reception area, reducing pre-procedural apprehension and anxiety-induced tachycardia or hypertension.

Key Stress Reduction Protocol (SRP) Components for Angina

Parameter	Recommended Clinical Protocol
Timing & Duration	Short, stress-free early morning appointments (typically $<60$ minutes).
Nitroglycerin Availability	Patient's own sublingual nitroglycerin (SL NTG) or spray must be placed on the dental tray within immediate reach before beginning treatment.
Pain & Anxiety Control	Excellent local anesthesia with aspiration; judicious use of vasoconstrictors (maximum 0.04 mg epinephrine, equivalent to 2 cartridges of 1:100,000 epinephrine or 4 cartridges of 1:200,000 epinephrine). Nitrous oxide/oxygen ( $N_2O/O_2$ ) inhalation sedation is highly effective.
Pre-medication	Short-acting benzodiazepines (e.g., Triazolam $0.125\text{–}0.25\text{ mg}$ or Diazepam $5\text{–}10\text{ mg}$ ) may be given the night before or 1 hour prior to the procedure if significant dental anxiety is present.
Vital Signs Monitoring	Baseline blood pressure and heart rate must be recorded prior to starting any invasive procedure.

Comparison of Other Options

B. After lunch: Postprandial periods divert cardiac output to the splanchnic circulation (gastrointestinal tract) to facilitate digestion. Dental procedures performed immediately after a heavy meal can place additional hemodynamic demands on an already compromised myocardium.
C. Evening: Cumulative daily fatigue and elevated autonomic baseline make the patient more susceptible to stress-induced angina.
D. Late night: Associated with circadian fatigue, lack of staff availability for emergency resuscitation, and disrupted biological rhythm.

Which heart condition requires antibiotic prophylaxis before invasive dental procedures?

# Which heart condition requires antibiotic prophylaxis before invasive dental procedures?

A. Hypertension

B. Prosthetic heart valves

C. Coronary artery disease

D. Arrhythmias

B. Prosthetic heart valves

Scientific Rationale & AHA Guidelines

According to the American Heart Association (AHA) and American Dental Association (ADA) guidelines, antibiotic prophylaxis prior to invasive dental procedures is restricted strictly to patients at the highest risk of adverse outcomes from Infective Endocarditis (IE).

During invasive dental manipulations, transient bacteremia (primarily caused by Viridans group streptococci) can occur. In patients with prosthetic heart valves or prosthetic valve repair materials, bacteria can adhere to the non-endothelialized artificial surfaces or turbulent flow sites, leading to bacterial vegetation and severe endocarditis.

High-Risk Cardiac Conditions Requiring Prophylaxis

Antibiotic prophylaxis is recommended only for the following specific conditions:

Prosthetic Cardiac Valves or Prosthetic Material: Includes mechanical and bioprosthetic valves, transcatheter-implanted valves, and prosthetic material used for cardiac valve repair (such as annuloplasty rings or chords).
Previous History of Infective Endocarditis.
Congenital Heart Disease (CHD):
- Unrepaired cyanotic CHD, including palliative shunts and conduits.
- Completely repaired congenital heart defect with prosthetic material or device during the first 6 months after the procedure (until endothelialization occurs).
- Repaired CHD with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device.
Cardiac Transplant Recipients who develop cardiac valvulopathy.

Conditions NOT Requiring Prophylaxis

The following cardiac conditions do not meet the criteria for routine antibiotic prophylaxis prior to dental care:

Hypertension (Choice A): No elevated risk for IE.
Coronary Artery Disease (Choice C): Prior myocardial infarction, coronary artery bypass grafts (CABG), or coronary stents do not require prophylaxis.
Arrhythmias (Choice D): Cardiac pacemakers and implanted cardioverter-defibrillators (ICDs) do not require prophylaxis.
Other low-to-moderate risk lesions: Mitral valve prolapse (with or without regurgitation), isolated atrial/ventricular septal defects beyond 6 months post-repair, and innocent heart murmurs.

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Year of Establishment: 2079

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NMC Number of Dental Surgeon: 17479

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Drug of choice for focal seizure is:

# Drug of choice for focal seizure is:

A. Phenytoin

B. Gabapentin

C. Lorazepam

D. Levetiracetam

The correct answer is D. Levetiracetam.

Levetiracetam is the drug of choice for focal (partial) onset seizures.

Current clinical practice and guidelines (including ILAE and NICE) prefer Levetiracetam (or Lamotrigine) as a first-line monotherapy due to its broad-spectrum efficacy, rapid onset, linear pharmacokinetics, minimal drug interactions, and superior safety profile compared to older agents.

Breakdown of the options:

Levetiracetam: First-line drug of choice for newly diagnosed focal seizures (both with and without focal-to-bilateral tonic-clonic evolution).
Phenytoin: Classic first-line agent for focal seizures, but largely replaced by newer anticonvulsants due to zero-order kinetics, severe drug-drug interactions, and adverse effects (e.g., gingival enlargement, nystagmus, ataxia).
Gabapentin: Used primarily as adjunctive (add-on) therapy for focal seizures, or for neuropathic pain.
Lorazepam: First-line drug of choice for acute emergency management of status epilepticus, not long-term monotherapy.

Which of the following is not an antigen-presenting cell?

# Which of the following is not an antigen-presenting cell?

A. B cell

B. Dendritic cell

C. T cell

D. Macrophage

The correct answer is C. T cell.

Explanation:

Professional Antigen-Presenting Cells (APCs) are specialized immune cells that process and display foreign antigens complexed with Major Histocompatibility Complex (MHC) class II molecules on their surfaces. Their primary role is to present these antigens to T cells to trigger an immune response.

The classical professional APCs are:

Dendritic cells: The most potent APCs, crucial for initiating primary immune responses by activating naive T cells.

Macrophages: Phagocytes that engulf pathogens and present antigens to T cells to sustain ongoing immune responses.

B cells: Internalize antigens via their specific surface antibodies and present them to helper T cells to receive the signals necessary for antibody production.

T cells, conversely, are the "responders." They use their T cell receptors (TCRs) to recognize the antigens presented by the APCs. They do not serve the primary function of capturing and presenting antigens.

Ringer lactate does not contain:

# Ringer's lactate does not contain:

A. Magnesium

B. Chloride

C. Potassium

D. Sodium

The correct answer is Magnesium.

Ringer's lactate (also known as Hartmann's solution or sodium lactate solution) is an isotonic crystalloid fluid used for intravenous resuscitation and fluid replacement. It is formulated to closely mimic the electrolyte concentration of human blood plasma, but it does not contain magnesium.

Ideally a malocclusion should be treated between the age of:

# Ideally a malocclusion should be treated between the age of:

A. 5 and 8 years

B. 8 and 10 years

C. 10 to 12 years

D. The age at which a malocclusion is treated depends on the problem involved

The correct answer is: D. The age at which a malocclusion is treated depends on the problem involved.

Explanation: There is no single ideal age to treat all malocclusions. The optimal timing depends on the type and severity of the malocclusion, the patient's growth status, and the treatment objectives.

Examples:

Early (5–8 years):
- Crossbites
- Functional shifts
- Harmful oral habits
- Severe skeletal Class III requiring interceptive treatment
Mixed dentition (8–10 years):
- Severe crowding
- Ectopic eruption
- Functional Class II correction in selected cases
Late mixed/early permanent dentition (10–12 years):
- Most comprehensive orthodontic treatments
- Class II correction during the pubertal growth spurt
- Alignment after eruption of permanent teeth
Adolescence or adulthood:
- Comprehensive orthodontic treatment
- Orthognathic surgery for severe skeletal discrepancies (after growth completion)

Nepal Medical Council Special Examination Sample Questions - Orthodontics and Dentofacial Orthopedics

100 MCQs - Orthodontics & Dentofacial Orthopedics (NMC Special Licence)

NMC Special Licence Exam: Orthodontics (MDS)

100 Interactive Questions including Image-based MCQs.

Instructions

✔️ Total Questions: 100
✔️ Level: Masters of Dental Surgery (MDS)
✔️ Explanations provided after each answer.
✔️ Click an option to lock in your answer.

Dentosphere : World of Dentistry

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