Definition: Biologically active cavity lining and pulp-capping materials based on calcium hydroxide, often combined with zinc oxide and salicylate resins or dispersed in a light-cured resin matrix. They are designed to create an alkaline environment, provide antibacterial action, and stimulate reparative dentine formation rather than to bear heavy loads.
Clinical Case:
A 22-year-old patient presents with a deep carious lesion on an upper premolar. During caries removal, a small pinpoint pulp exposure occurs in an otherwise healthy tooth. You decide on direct pulp capping with a calcium hydroxide material followed by a definitive restoration. The goal is to preserve pulpal vitality and stimulate a dentine bridge beneath the exposure.
Uses
Direct pulp capping of small mechanical or carious exposures in vital teeth.
Indirect pulp capping in very deep carious lesions approaching the pulp.
Thin sublining under other base materials in deep cavities.
Lining under silicate and resin-based fillings where a chemical barrier is desired.
Endodontic applications:
Setting and non-setting calcium hydroxide pastes as intracanal medicaments or temporary root fillings.
Apexification procedures in immature teeth with open apices.
How to use them in clinical practice?
Assess depth and pulpal status
Decide whether direct or indirect pulp capping is appropriate, or whether calcium hydroxide is needed only as a deep liner.
Select formulation
Two-paste chemically cured calcium hydroxide cement for typical pulp capping/lining.
Light-cured calcium hydroxide liner if rapid set and controlled placement are desired.
Prepare the site
Control bleeding at an exposure with gentle irrigation and cotton pellets.
Ensure the area is clean and reasonably dry (avoid flooding).
Dispense and mix
Two-paste: mix equal small amounts of base and catalyst to a smooth, creamy paste.
Light-cured: dispense directly from syringe.
Place
Apply a thin layer over the exposure or deepest area of dentine only.
Avoid coating unnecessary areas, especially where adhesive bonding to dentine is planned.
Set
Two-paste: allow to set; moisture in the dentine accelerates the reaction.
Light-cured: expose to curing light for recommended time.
Overlay
Place a stronger base (e.g. zinc phosphate or glass-ionomer) over the calcium hydroxide where high stresses (e.g. amalgam condensation) are anticipated.
Complete definitive restoration.
Endodontic use (outline)
Place non-setting or slowly setting Ca(OH)₂ paste into prepared canal as an interim dressing or for apexification.
Seal access and review/replace as appropriate.
Constituents
Simple suspensions
Calcium hydroxide in water or polymer solutions (e.g. methylcellulose).
Two-paste cements
Paste 1:
Calcium hydroxide (≈50%)
Zinc oxide (≈10%)
Zinc stearate (accelerator)
Carrier (e.g. ethyl toluene sulphonamide or paraffinic oil)
Paste 2:
Glycol salicylate (e.g. butylene glycol disalicylate)
Inert fillers and radiopacifiers (e.g. titanium dioxide, calcium sulphate, calcium tungstate)
Light-cured liners
Methacrylate resin matrix (e.g. Bis-GMA, HEMA)
Calcium hydroxide
Photoinitiators, stabilisers
Chemistry
Two-paste systems
Salicylate groups chelate zinc ions to form a zinc–salicylate resin matrix on setting.
Calcium hydroxide remains largely as a dispersed phase, available for release of Ca²⁺ and OH⁻ ions.
Light-cured systems
Free-radical polymerisation of methacrylate monomers upon light activation.
Subsequent water uptake allows the release of calcium hydroxide and creation of an alkaline pH.