Dentosphere : World of Dentistry

 # A two-month-old boy is referred for evaluation because he has an abnormal head shape. Physical examination shows low-set ears, and short-webbed fingers. A CT scan shows sagittal and lambdoid synostosis. Which of the following genes is most likely to cause this syndrome ? A. TWIST1 B. FGFR1 C. FGFR2 D. RAB23 The correct answer C. FGFR2. The most likely gene to cause the syndrome described, characterized by sagittal and lambdoid synostosis, low-set ears, and short-webbed fingers in a two-month-old boy, is C. FGFR2. Explanation: The clinical presentation suggests a craniosynostosis syndrome, with sagittal and lambdoid synostosis indicating premature fusion of cranial sutures, and additional features like low-set ears and short-webbed fingers (syndactyly) pointing toward a syndromic form. Among the options, mutations in FGFR2 (Fibroblast Growth Factor Receptor 2) are strongly associated with syndromic craniosynostoses, particularly Apert syndrome and Crouzon syndrome, both of which ...

 # Which of the following antibiotics acts by inhibiting cell wall synthesis? a) Doxycycline b) Aminoglycosides c) Erythromycin d) Cefepime The correct answer is D. Cefepime. The correct answer is d) Cefepime. Explanation: Cefepime is a fourth-generation cephalosporin antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), disrupting peptidoglycan cross-linking, and leading to cell lysis. Doxycycline (a tetracycline) inhibits protein synthesis by binding to the 30s ribosomal subunit, preventing tRNA attachment. Aminoglycosides (e.g., gentamicin) also target protein synthesis by binding to the 30s ribosomal subunit, causing misreading of mRNA. Erythromycin (a macrolide) inhibits protein synthesis by binding to the 50s ribosomal subunit, blocking peptide chain elongation. Thus, only Cefepime acts by inhibiting cell wall synthesis.

 # Traumatic injury to primary tooth leads to intrusion. After how much time, the tooth usually re-erupts? a) 30 days b) 3 months c) 6 months d) 12 months The correct answer is C. 6 months. Explanation: Intrusion of a primary tooth occurs when a traumatic force displaces the tooth apically into the alveolar bone. The potential for re-eruption depends on factors such as the degree of intrusion, the integrity of the periodontal ligament, the child's age, and the absence of complications like ankylosis or damage to the underlying permanent tooth bud. In pediatric dentistry, re-eruption is a common outcome for intruded primary teeth due to the elasticity of the periodontal ligament and ongoing alveolar growth. While some studies suggest re-eruption can occur within 2–4 months for mild to moderate intrusions, the 6-month timeframe is more plausible in clinical practice for several reasons: Variable Healing Dynamics: Moderate to severe intrusions may require longer for the periodontal li...

 # Bulk of lamina propria of the gingiva is made of collagen type: a) I b) II c) III d) IV The correct answer is A. Type I. The bulk of the lamina propria of the gingiva is made of collagen type I. Explanation: The lamina propria of the gingiva, a connective tissue layer supporting the gingival epithelium, primarily consists of collagen type I, which provides structural strength and resilience. Collagen type I is the most abundant collagen in connective tissues like the gingiva, while other types (e.g., II in cartilage, III in reticular fibers, IV in basement membranes) are less dominant in this context.

 # Secretin does not cause: a) Bicarbonate secretion b) Augments the action of CCK c) Contraction of pyloric sphincter d) Gastric secretion increase The correct answer is D. Gastric secretion increase. Secretin does not cause d) Gastric secretion increase. Explanation: a) Bicarbonate secretion: Secretin stimulates the pancreas to secrete bicarbonate to neutralize acidic chyme in the duodenum. b) Augments the action of CCK: Secretin works synergistically with cholecystokinin (CCK) to enhance pancreatic enzyme and bile secretion. c) Contraction of pyloric sphincter: Secretin promotes relaxation of the pyloric sphincter to allow chyme to pass into the duodenum. d) Gastric secretion increase: Secretin inhibits gastric acid secretion and gastric motility to slow digestion in the stomach, making this the correct answer.

 # Major and frequent influence for arterial thrombus formation is: a) Alteration in blood flow b) Hypercoagulability c) Endothelial damage d) Fatty streak The correct answer is C. Endothelial damage. For a single-choice question on thrombus formation, the answer depends on the clinical context: 1. Arterial Thrombosis (e.g., Myocardial Infarction) Correct Answer: [c) Endothelial Damage] Rationale: Arterial thrombi typically form at sites of disrupted atherosclerotic plaques. Endothelial injury directly exposes prothrombotic subendothelial collagen and tissue factor, triggering platelet adhesion/aggregation and coagulation activation. 2. Venous Thrombosis (e.g., DVT) Correct Answer: [a) Alteration in Blood Flow] or [b) Hypercoagulability] Rationale: Venous thrombi often arise from stasis (e.g., immobility) or hypercoagulable states (e.g., Factor V Leiden). If forced to choose one, prioritize [a) Alteration in Blood Flow] as stasis is the most common trigger. Why Not Other Options? [...

Vestibular toxicity is associated with which of the following tetracyclines? A. Doxycycline B. Minocycline C. Chlorotetracycline D. Oxytetracycline