Dental MCQ
Genes and inheritance · Biochemistry · INBDE Patient Cases

Molecular Biology & Genetics INBDE Patient Cases

By Dr. Isaac Sun, DDS

6 ADA INBDE-format patient cases on molecular biology & genetics. Each case is a shared patient box (chief complaint, history, medications, allergies, exam) followed by linked multiple-choice questions with full distractor explanations. Practice the way the real exam is structured.

6 patient cases30 linked questionsADA INBDE formatFull distractor explanations

Six ADA INBDE-format patient cases connecting molecular biology and genetics to dentistry: amelogenesis imperfecta with defective enamel on all teeth, dentinogenesis imperfecta with osteogenesis imperfecta (opalescent teeth, blue sclera, type I collagen), tetracycline intrinsic staining from calcium chelation in developing teeth and the 30S ribosomal mechanism, cleidocranial dysplasia (RUNX2) with supernumerary and unerupted teeth, hypohidrotic ectodermal dysplasia with hypodontia and heat intolerance, and Gardner syndrome (APC) where jaw osteomas and dental anomalies mark colorectal cancer risk. Topics include DNA replication and repair, transcription and translation, antibiotics that target the ribosome, inheritance patterns, and the mutations behind developmental dental disorders.

Case Coverage Map
What each case is testing
Defective enamel on every tooth:
Amelogenesis imperfecta, enamel matrix genes, the all-teeth pattern, variable inheritance, and full-coverage restorative care.
Opalescent teeth and blue sclera:
Dentinogenesis imperfecta with osteogenesis imperfecta, the type I collagen defect, obliterated pulps, and gentle coordinated care.
Banded gray teeth after a childhood antibiotic:
Tetracycline staining, calcium chelation in developing teeth, the 30S translation mechanism, and avoiding it in pregnancy and young children.
Many baby teeth retained and extra teeth on the X-ray:
Cleidocranial dysplasia, RUNX2, supernumerary and unerupted teeth, autosomal dominant inheritance, and surgical-orthodontic care.
A child missing many teeth who can't sweat:
Ectodermal dysplasia, hypodontia and conical teeth, hypohidrosis and overheating, X-linked inheritance, and prosthetic planning.
Jaw lumps and extra teeth that point to the colon:
Gardner syndrome, APC, jaw osteomas and dental anomalies as a marker of colorectal cancer risk, and life-saving referral.
Patient case: Defective enamel on every tooth
0 of 5 answered, 0 correct
Patient
Female, 14 years old, accompanied by parent
Chief Complaint
"All my teeth are yellow-brown and sensitive, and they look worn."
Background and/or Patient History
  • Both the baby teeth and the adult teeth were affected
  • A parent and a sibling have similar teeth
  • Marked tooth sensitivity and self-consciousness about appearance
  • Good oral hygiene, normal diet
Allergies
NKDA
Medications
  • None
Current Findings
  • Thin, soft, discolored enamel on all teeth
  • Generalized sensitivity
  • No localized caries pattern explaining the appearance
  1. Question 1
    Moderate
    Enamel defects on essentially all teeth in both dentitions, with a family history, are most consistent with:
  2. Question 2
    Moderate
    The defect in amelogenesis imperfecta lies in the genes that build:
  3. Question 3
    Moderate
    The positive family history across generations suggests the inheritance can be:
  4. Question 4
    Moderate
    A major restorative challenge in these patients is that:
  5. Question 5
    Moderate
    Beyond restoration, appropriate care includes:

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Patient case: Opalescent teeth and blue sclera
0 of 5 answered, 0 correct
Patient
Male, 9 years old, accompanied by parent
Chief Complaint
"His teeth look gray and shiny and keep chipping."
Background and/or Patient History
  • Teeth described as opalescent gray-brown since eruption
  • History of several bone fractures from minor injuries
  • Parent notes a bluish tint to the whites of his eyes
  • Family members with similar teeth and easy fractures
Allergies
NKDA
Medications
  • None
Current Findings
  • Opalescent, bulbous teeth with worn enamel and short roots
  • Blue sclera
  • Radiographs show obliterated pulp chambers
  1. Question 1
    Hard
    Opalescent teeth with obliterated pulps, in a child with blue sclera and fractures, indicate:
  2. Question 2
    Hard
    The underlying molecular defect involves:
  3. Question 3
    Moderate
    The blue sclera and easy fractures point to involvement of:
  4. Question 4
    Moderate
    A practical dental management point in dentinogenesis imperfecta is that:
  5. Question 5
    Moderate
    Recognizing the osteogenesis imperfecta association matters because the dentist should:

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Patient case: Banded gray teeth after a childhood antibiotic
0 of 5 answered, 0 correct
Patient
Female, 16 years old, accompanied by parent
Chief Complaint
"Her permanent teeth have gray bands and she's embarrassed."
Background and/or Patient History
  • Took a tetracycline antibiotic repeatedly for infections as a young child
  • Horizontal gray-brown bands on the permanent teeth
  • Otherwise healthy with good hygiene
  • Parent asks whether this was preventable
Allergies
NKDA
Medications
  • None
Current Findings
  • Intrinsic horizontal gray-brown banding across multiple teeth
  • Banding corresponds to the time of antibiotic exposure
  • No active caries
  1. Question 1
    Moderate
    Her banded intrinsic discoloration is most likely due to:
  2. Question 2
    Hard
    Tetracycline binds to teeth and bone because it chelates:
  3. Question 3
    Hard
    As an antibiotic, tetracycline works by:
  4. Question 4
    Moderate
    To prevent this, tetracyclines should be avoided in:
  5. Question 5
    Moderate
    If a young child needs an antibiotic for a dental infection, a more appropriate first choice is usually:

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Patient case: Many baby teeth retained and extra teeth on the X-ray
0 of 5 answered, 0 correct
Patient
Male, 12 years old, accompanied by parent
Chief Complaint
"He still has lots of baby teeth and the adult ones aren't coming in."
Background and/or Patient History
  • Many retained primary teeth and few erupted permanent teeth
  • Able to bring his shoulders together unusually far
  • A parent had similar dental and skeletal features
  • Normal intelligence and growth otherwise
Allergies
NKDA
Medications
  • None
Current Findings
  • Multiple retained primary teeth
  • Panoramic radiograph shows numerous unerupted and supernumerary teeth
  • History consistent with absent or hypoplastic clavicles
  1. Question 1
    Hard
    Retained primary teeth with multiple unerupted and supernumerary teeth, plus clavicular changes, suggest:
  2. Question 2
    Hard
    Cleidocranial dysplasia is caused by a mutation in:
  3. Question 3
    Moderate
    Its inheritance is typically:
  4. Question 4
    Moderate
    The main dental management challenge is:
  5. Question 5
    Moderate
    The appropriate dentist response includes:

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Patient case: A child missing many teeth who can't sweat
0 of 5 answered, 0 correct
Patient
Male, 5 years old, accompanied by parent
Chief Complaint
Parent: "He's missing a lot of teeth and the ones he has are pointy."
Background and/or Patient History
  • Several teeth never developed (hypodontia)
  • Sparse, fine hair and a history of overheating in hot weather
  • Reduced ability to sweat
  • A maternal uncle was similarly affected
Allergies
NKDA
Medications
  • None
Current Findings
  • Multiple missing teeth with conical (peg-shaped) teeth present
  • Sparse hair
  • Dry skin and a history of heat intolerance
  1. Question 1
    Moderate
    Hypodontia with conical teeth, sparse hair, and reduced sweating is characteristic of:
  2. Question 2
    Hard
    The common (hypohidrotic) form is frequently inherited as:
  3. Question 3
    Moderate
    A potentially dangerous systemic feature to recognize is:
  4. Question 4
    Moderate
    Dental management of the missing teeth in a growing child typically involves:
  5. Question 5
    Moderate
    The dentist's role also includes:

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Patient case: Jaw lumps and extra teeth that point to the colon
0 of 5 answered, 0 correct
Patient
Male, 28 years old
Chief Complaint
"My dentist found bony lumps in my jaw and some extra teeth on the X-ray."
Background and/or Patient History
  • Panoramic radiograph shows multiple jaw osteomas, supernumerary teeth, and odontomas
  • Several skin lumps (epidermoid cysts) noted
  • Father died of colon cancer in his forties
  • No abdominal symptoms yet
Allergies
NKDA
Medications
  • None
Current Findings
  • Multiple osteomas of the jaws
  • Supernumerary teeth and odontomas on the radiograph
  • Epidermoid cysts of the skin
  1. Question 1
    Hard
    Jaw osteomas, supernumerary teeth, odontomas, and skin cysts, with a strong family history of colon cancer, suggest:
  2. Question 2
    Hard
    Gardner syndrome is caused by a mutation in the:
  3. Question 3
    Moderate
    The most important reason to recognize this from the dental findings is the high risk of:
  4. Question 4
    Moderate
    Because the dental and bony findings often appear before bowel symptoms, the dentist should:
  5. Question 5
    Moderate
    Gardner syndrome illustrates that a mutation in a tumor-suppressor gene can:

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Molecular Biology & Genetics core recall

Refresh the anatomy facts these cases depend on: nerve numbers, foramina, functions, and lesion findings.

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