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Restorative & Materials · patient case with 2 questions

Soda habit with multiple deep lesions

Patient: 22-year-old patient who arrives sipping a soft drink.

Chief complaint: Sensitivity in several teeth.

History: Drinks two to three sodas daily, sipped over hours. Brushes once daily, no flossing, no fluoride rinse.

Findings: Multiple carious lesions across several quadrants, several radiographically extending into the inner third of dentin close to the pulp. All teeth respond normally to cold with no lingering pain and no periapical changes.

Question 1

Below approximately what pH does enamel begin to demineralize?

  1. 6.5
  2. 5.5
  3. 3.0
  4. 7.0
Show answer and explanation

Correct answer: B. 5.5

  • A. 6.5 is above the enamel threshold, although it is within the demineralizing range for root dentin.
  • B. CORRECT. The CRITICAL pH for enamel is approximately 5.5. Below that, plaque fluid is undersaturated with respect to hydroxyapatite and net mineral loss begins. Root surface dentin and cementum have a higher critical pH of about 6.2 to 6.7, which is why root caries progresses at pH values enamel would tolerate. Colas themselves sit near pH 2.5.
  • C. pH 3 is far below critical and describes the drink itself rather than the threshold being asked for.
  • D. 7.0 is neutral. Resting plaque pH sits above the critical value and enamel is stable.

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Question 2

For the deep lesions in these vital, asymptomatic teeth, what is the MOST appropriate approach?

  1. Access and complete root canal treatment on each tooth before restoring
  2. Remove all carious dentin to hard dentin, and if the pulp is exposed apply calcium hydroxide and restore
  3. Selective removal — excavate to firm dentin peripherally, leave soft affected dentin over the pulp, and seal with a glass ionomer base and a definitive restoration
  4. Excavate the caries and place the restoration with no liner or base
Show answer and explanation

Correct answer: C. Selective removal — excavate to firm dentin peripherally, leave soft affected dentin over the pulp, and seal with a glass ionomer base and a definitive restoration

  • A. These teeth are vital with no lingering pain and no periapical change. Elective endodontics is drastic overtreatment.
  • B. Complete excavation to hard dentin in a deep lesion is the traditional approach, and it carries a much higher exposure rate. Direct pulp capping is a rescue when exposure happens, not a plan.
  • C. CORRECT. Current evidence favours SELECTIVE (partial) caries removal in deep lesions in vital, asymptomatic teeth. Peripheral dentin is taken to hard tissue so the restoration seals, while soft affected dentin over the pulp is deliberately left and sealed. Cutting off the bacterial substrate arrests the lesion, and pulp exposure rates and postoperative symptoms are lower than with complete excavation.
  • D. A deep restoration with no base leaves the pulp without thermal or chemical protection.

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