Restorative & Materials · patient case question
On one deep lesion the excavation approaches the pulp without exposing it. Which material is placed to stimulate reparative dentine formation?
Patient case: Rampant caries on a full-mouth series
Patient: Female, 29 years old
Chief complaint: “A piece of my back tooth broke off.”
History: No systemic disease. Frequent sugared energy drinks. Last dental visit six years ago. Brushes once daily, no floss.
Findings: Full-mouth series shows occlusal and proximal caries in 14 teeth. Tooth #3 has gross coronal destruction extending 2 mm subgingivally on the mesial. No periapical radiolucencies. Salivary flow is normal.
Show answer and explanation
Correct answer: C. Calcium hydroxide
- A. Glass ionomer bonds chemically to dentine and releases fluoride, making it an excellent base and liner, but it is not the classic bridge-forming material.
- B. Zinc phosphate is a strong luting cement with a low initial pH of about 3.5, which is IRRITATING to the pulp. It requires a protective liner over deep dentine rather than providing one.
- C. CORRECT. Calcium hydroxide has a pH around 12.5. That high alkalinity produces a superficial zone of coagulation necrosis, and beneath it the released calcium and hydroxyl ions stimulate odontoblast-like cells to lay down a REPARATIVE DENTINE BRIDGE. It is also antibacterial by virtue of the same pH. The tradeoffs are poor mechanical strength and gradual dissolution, so it is always covered by a base or a bonded restoration.
- D. Zinc oxide eugenol is sedative and palliative, and eugenol has an obtundent effect on pulpal nerve endings, but it does not induce a dentine bridge. It also interferes with resin polymerisation.
Note: MTA and the newer calcium silicate cements such as Biodentine now outperform calcium hydroxide for direct pulp capping, giving more predictable bridges with less tunnel defect formation. Calcium hydroxide remains the classic exam answer for the mechanism.
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