Biochemistry Practice Questions
Biochemistry questions on dental board exams rarely ask for a pathway in isolation. They ask why a deficiency shows up in the mouth, why enamel dissolves at a given pH, or how calcium and phosphate are kept in balance. This set covers collagen synthesis and cross-linking, the mineral chemistry of enamel and dentine, mineral homeostasis with parathyroid hormone and vitamin D, saliva biochemistry, metabolic pathways relevant to dentistry, and the oral signs of vitamin and nutritional deficiencies. It suits dental students revising first- and second-year biochemistry as well as dentists preparing for the AFK, INBDE and ORE, where these basic-science links still appear.
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Questions
Question 1 of 10
Collagen Biochemistry
A patient with a known inherited connective tissue disorder affecting collagen presents with unusually fragile, hyperextensible gingival tissue. This finding is best explained by an underlying defect in which biological molecule?
The answer is D.
Inherited connective tissue disorders such as Ehlers-Danlos syndrome commonly result from mutations affecting collagen synthesis, structure, or processing. Because gingival connective tissue relies heavily on properly formed collagen for strength, these patients often show unusually fragile, stretchable oral soft tissue.
Question 2 of 10
Vitamin & Nutritional Deficiencies: Oral Manifestations
A patient presents with persistent angular cheilitis and a magenta, inflamed tongue. Along with checking for candidal infection, which nutritional deficiency should be considered?
The answer is C.
Angular cheilitis paired with a magenta, glossy tongue is a classic presentation of riboflavin deficiency, since B2 is needed for normal epithelial maintenance. Candidal infection can coexist with or mimic these findings, so both possibilities are reasonably considered together in the workup.
Question 3 of 10
Saliva Biochemistry
Statherin, a salivary protein incorporated into the acquired pellicle, plays a key role in which function?
The answer is A.
Statherin adsorbs onto the enamel surface as part of the acquired pellicle and inhibits spontaneous precipitation of calcium phosphate salts from saliva, helping keep saliva supersaturated with these minerals without unwanted calculus formation, while still allowing controlled remineralization of tooth surfaces.
Question 4 of 10
Mineral Homeostasis
Parathyroid hormone (PTH) raises blood calcium by acting on which combination of target organs?
The answer is D.
PTH increases serum calcium by stimulating osteoclastic bone resorption to release calcium and phosphate, and by acting on the kidney to increase calcium reabsorption while promoting phosphate excretion. It also stimulates renal activation of vitamin D, which enhances intestinal calcium absorption indirectly.
Question 5 of 10
Basic Metabolic Pathways Relevant to Dentistry
Which enzyme family carries out the majority of phase I oxidative drug metabolism reactions in the liver?
The answer is D.
The cytochrome P450 superfamily of hepatic microsomal enzymes performs most phase I oxidative reactions, metabolizing a broad range of drugs including many used in dentistry. Genetic variability and drug interactions affecting these enzymes can significantly alter drug clearance and dosing needs.
Question 6 of 10
Enamel/Dentin Mineral Chemistry
Fluorapatite forms when fluoride ions substitute for which component of the normal hydroxyapatite crystal?
The answer is D.
In fluorapatite formation, fluoride ions replace hydroxyl groups within the hydroxyapatite crystal lattice. This substitution produces a more stable, less soluble crystal structure that is more resistant to acid dissolution than the original hydroxyapatite.
Question 7 of 10
Nutrition & Disease Progression
A medically compromised patient with a mechanically altered soft diet after a recent surgery asks about caries risk. What is the most relevant counseling point?
The answer is A.
Many soft or pureed diets rely on processed, easily fermentable carbohydrates that can be just as cariogenic as harder foods, and their softer consistency may also reduce the mechanical clearance that chewing normally provides, so patients on such diets still need active caries risk counseling.
Question 8 of 10
Vitamin & Nutritional Deficiencies: Oral Manifestations
Riboflavin (vitamin B2) deficiency classically presents with which combination of oral findings?
The answer is D.
Riboflavin deficiency impairs epithelial cell turnover and antioxidant defense, producing angular cheilitis at the corners of the mouth along with a smooth, magenta-colored, inflamed tongue known as glossitis, distinguishing it clinically from deficiencies of other B vitamins.
Question 9 of 10
Nutrition & Disease Progression
A patient recovering from periodontal surgery asks if diet matters for healing. What is the most accurate response?
The answer is A.
Wound healing after periodontal surgery depends on adequate protein for collagen synthesis and micronutrients such as vitamin C for proper collagen cross-linking and immune function. Advising a patient that diet meaningfully supports healing, alongside good oral hygiene, is accurate and clinically relevant guidance.
Question 10 of 10
Vitamin & Nutritional Deficiencies: Oral Manifestations
A child presents with generalized enamel hypoplasia on permanent teeth and a history of minimal sun exposure and low dietary vitamin D. Which deficiency most plausibly explains the enamel finding?
The answer is A.
Vitamin D is essential for adequate calcium availability during amelogenesis. A history of low sun exposure and low dietary intake in a child with generalized enamel hypoplasia points toward vitamin D deficiency disrupting normal enamel mineralization during tooth formation.
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