Dental MCQ
Preparing the tooth · Operative Dentistry · INBDE Patient Cases

Cavity Preparation & Principles INBDE Patient Cases

By Dr. Isaac Sun, DDS

7 ADA INBDE-format patient cases on cavity preparation & principles. 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.

7 patient cases35 linked questionsADA INBDE formatFull distractor explanations

Seven ADA INBDE-format patient cases on cavity preparation and its principles: designing a Class II amalgam preparation with mechanical retention (convergent walls, dovetail, grooves) and a 90-degree butt-joint margin, a conservative bonded composite and preventive resin restoration for a small occlusal lesion, cuspal coverage and resistance form when a cusp is undermined (framed by the Structure and Force lenses), rubber dam isolation and why a dry field is essential for bonding plus airway protection, a matrix and wedge to restore the proximal contact and prevent a gingival overhang, avoiding iatrogenic damage to the adjacent tooth, and the modern shift from extension for prevention to minimal intervention. Topics include preparation nomenclature and the Black classification, outline, resistance, retention, and convenience form, margin and material-driven design, conservative preparation, isolation, and matrix systems.

Case Coverage Map
What each case is testing
Designing a Class II amalgam preparation:
Amalgam mechanical retention (convergence, dovetail, grooves), the 90-degree butt margin, resistance form under load, and the matrix.
A small occlusal cavity in a young patient:
Conservative bonded composite and the preventive resin restoration, adhesion-based retention, the enamel bevel, and isolation.
A weakened cusp after removing a large old filling:
Resistance form and cuspal coverage, the marginal ridge, the Structure and Force lenses, and when a tooth needs an indirect restoration.
Why isolate before bonding:
The dry field for bonding, rubber dam advantages including airway protection, and isolation when a dam is not possible.
Rebuilding the contact between two teeth:
Matrix and wedge for proximal contact and contour, the gingival overhang as a plaque trap, and why the contact matters.
Avoiding damage to the neighboring tooth:
Iatrogenic proximal damage during a Class II prep, protecting the adjacent surface, overextension, and conservation of structure.
How far to extend the preparation:
Extension for prevention versus minimal intervention, conservative outline form, and sealing sound fissures rather than cutting them.
Patient case: Designing a Class II amalgam preparation
0 of 5 answered, 0 correct
Patient
Male, 47 years old
Chief Complaint
"I have a cavity between two back teeth and want a silver filling."
Background and/or Patient History
  • A proximal (Class II) lesion on a molar, cavitated into dentin
  • Heavy occlusal load and some bruxism
  • Prefers amalgam for durability
  • Adequate remaining tooth structure
Allergies
NKDA
Medications
  • None
Current Findings
  • Cavitated proximal caries; cusps largely intact
  • Plans for an amalgam restoration
  1. Question 1
    Moderate
    Retention of this amalgam restoration will depend primarily on:
  2. Question 2
    Moderate
    The cavosurface margin for the amalgam should be:
  3. Question 3
    Hard
    To resist proximal displacement of the restoration, the prep includes a:
  4. Question 4
    Moderate
    Given his bruxism and heavy load, resistance form should emphasize:
  5. Question 5
    Moderate
    To restore the proximal contact and avoid a gingival overhang, the dentist uses:

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Patient case: A small occlusal cavity in a young patient
0 of 5 answered, 0 correct
Patient
Female, 15 years old, accompanied by parent
Chief Complaint
Parent: "There's a small cavity in the groove of a back tooth."
Background and/or Patient History
  • A small, localized occlusal lesion in one fissure of a molar
  • The rest of the fissure system is sound but deep
  • Low to moderate caries risk
  • First restoration on this tooth
Allergies
NKDA
Medications
  • None
Current Findings
  • Limited cavitated occlusal caries in one pit; adjacent fissures sound but susceptible
  • Good isolation achievable
  1. Question 1
    Moderate
    A conservative approach to a small occlusal lesion with sound but susceptible surrounding fissures is a:
  2. Question 2
    Moderate
    Retention for the composite portion is provided by:
  3. Question 3
    Moderate
    Because composite bonds, the preparation can be:
  4. Question 4
    Hard
    An enamel bevel on a composite margin would:
  5. Question 5
    Moderate
    Successful bonding here most depends on:

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Patient case: A weakened cusp after removing a large old filling
0 of 5 answered, 0 correct
Patient
Female, 58 years old
Chief Complaint
"My old large filling needs replacing and a wall of the tooth looks thin."
Background and/or Patient History
  • A large old restoration removed, leaving thin, undermined cusps
  • A history of a cracked cusp on another tooth
  • Heavy occlusal load
  • Tooth is vital and restorable
Allergies
NKDA
Medications
  • None
Current Findings
  • Remaining cusps thin and undermined after caries and old material removed
  • Marginal ridge previously lost
  1. Question 1
    Moderate
    With thin, undermined cusps under heavy load, resistance form is best served by:
  2. Question 2
    Moderate
    Through the SDF lens, the loss of cusps and the marginal ridge most affects which considerations?
  3. Question 3
    Hard
    An intact marginal ridge matters structurally because it:
  4. Question 4
    Moderate
    If the remaining structure is too compromised for a direct restoration to protect it, the appropriate move is to:
  5. Question 5
    Moderate
    This decision (direct restoration versus cuspal coverage) is fundamentally about:

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Patient case: Why isolate before bonding
0 of 5 answered, 0 correct
Patient
Male, 33 years old
Chief Complaint
"Why do you put that sheet in my mouth for a filling?"
Background and/or Patient History
  • Scheduled for a bonded composite restoration
  • Tends to have a wet field and an active tongue
  • Curious about the rubber dam
  • No latex allergy
Allergies
NKDA
Medications
  • None
Current Findings
  • Posterior tooth requiring an adhesive restoration
  • Moisture control challenging without isolation
  1. Question 1
    Moderate
    The primary reason a dry field matters for a bonded composite is that contamination:
  2. Question 2
    Moderate
    Besides moisture control, the rubber dam also provides:
  3. Question 3
    Moderate
    The airway-protection benefit of the rubber dam is important because it prevents:
  4. Question 4
    Moderate
    If a rubber dam cannot be used, the operator must still:
  5. Question 5
    Easy
    The best simple explanation to give this patient is that the dam:

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Patient case: Rebuilding the contact between two teeth
0 of 5 answered, 0 correct
Patient
Female, 38 years old
Chief Complaint
"Food keeps getting stuck between my back teeth since my last filling."
Background and/or Patient History
  • A previous Class II restoration with a poor proximal contact
  • Food impaction and gingival irritation at the site
  • A ledge detectable at the gingival margin
  • Now needs the restoration redone
Allergies
NKDA
Medications
  • None
Current Findings
  • Open or poor proximal contact and a gingival overhang on the existing restoration
  • Localized gingival inflammation at the overhang
  1. Question 1
    Moderate
    Food impaction from an open contact and a marginal ledge indicate problems with the prior restoration's:
  2. Question 2
    Moderate
    To rebuild a proper proximal contact and contour, the dentist should use:
  3. Question 3
    Moderate
    The wedge specifically helps by:
  4. Question 4
    Moderate
    The gingival overhang on the old restoration caused inflammation because it:
  5. Question 5
    Moderate
    A proper proximal contact is important because it:

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Patient case: Avoiding damage to the neighboring tooth
0 of 5 answered, 0 correct
Patient
Male, 25 years old
Chief Complaint
"I'm here for a filling on the side of a back tooth."
Background and/or Patient History
  • A Class II preparation planned on a molar
  • The adjacent tooth is sound and in tight contact
  • Operator is mindful of avoiding iatrogenic damage
  • Routine restorative visit
Allergies
NKDA
Medications
  • None
Current Findings
  • Proximal lesion adjacent to a sound neighboring tooth
  • Tight proximal contact
  1. Question 1
    Moderate
    A recognized iatrogenic risk during a Class II preparation is:
  2. Question 2
    Hard
    A way to protect the adjacent tooth during proximal preparation is to:
  3. Question 3
    Moderate
    Overextending the preparation beyond the disease is a problem because it:
  4. Question 4
    Moderate
    If the adjacent proximal surface is inadvertently nicked, the operator should:
  5. Question 5
    Moderate
    Avoiding iatrogenic damage reflects the broader operative principle of:

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Patient case: How far to extend the preparation
0 of 5 answered, 0 correct
Patient
Female, 30 years old
Chief Complaint
"Does the filling have to be big to keep cavities from coming back?"
Background and/or Patient History
  • A localized occlusal lesion with sound surrounding grooves
  • Low caries risk and good fluoride exposure
  • Asks whether a larger filling prevents future decay
  • Wants to keep the tooth as intact as possible
Allergies
NKDA
Medications
  • None
Current Findings
  • Confined cavitated occlusal caries; adjacent fissures sound
  • Good home care and fluoride use
  1. Question 1
    Moderate
    The historical idea of cutting a larger preparation into self-cleansing areas to prevent future caries is called:
  2. Question 2
    Moderate
    In modern practice, extension for prevention has largely been replaced because:
  3. Question 3
    Moderate
    For this confined lesion in a low-risk patient, the outline form should:
  4. Question 4
    Moderate
    The sound but susceptible grooves are best protected by:
  5. Question 5
    Moderate
    The best answer to her question is that a bigger filling:

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Keep studying
Cavity Preparation & Principles core recall

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

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