When is Calcium Hydroxide Medicament Indicated?
A Clinical Case Selection Guide.

Calcium hydroxide is primarily indicated in cases of pulpal necrosis with apical periodontitis, for apexification in immature permanent teeth, and to control inflammatory root resorption. Its efficacy stems from its high pH of approximately 12.5, which denatures bacterial proteins and lipopolysaccharides (LPS), creating an environment hostile to microbial survival and conducive to periapical healing.

This alkaline environment also stimulates hard tissue repair by activating tissue enzymes like alkaline phosphatase, a key factor in its success for apexification and perforation repair. For practising Indian dentists, its long shelf-life and cost-effectiveness make it a go-to material for multi-visit endodontic products protocols.

• Necrotic Pulps with Apical Periodontitis: Used between appointments to disinfect the root canal system and reduce bacterial load before obturation.
• Apexification: Induces the formation of a hard tissue apical barrier in non-vital immature teeth, typically over several months.
• Weeping Canals: Its hygroscopic nature helps to dry persistently wet canals (suppuration/exudate) that would otherwise compromise the seal of the final obturation.
• Root Resorption: Arrests inflammatory external and internal resorption by eliminating bacteria and neutralizing the acidic environment favoured by clastic cells.

Calcium hydroxide is contraindicated for routine vital pulp capping and in single-visit endodontics where thorough disinfection can be achieved chemo-mechanically. Its highly caustic nature causes superficial liquefaction necrosis on contact with vital tissue, making it less suitable than biocompatible materials like MTA or bioceramics for preserving pulp vitality.

Furthermore, its effectiveness against specific resilient microorganisms, such as Enterococcus faecalis, which is commonly found in failed root canal treatments, is limited. In such retreatment cases, an alternative or adjunctive disinfectant may be required for predictable success. The choice of modern root canal sealers with antibacterial properties can also influence the need for an inter-appointment medicament.

• Vital Pulp Capping: Bioceramics (MTA, Biodentine) provide a better seal and promote higher quality dentin bridge formation without causing extensive necrosis.
• Routine Single-Visit Cases: Not necessary if the canal can be adequately debrided and dried in one appointment.
• Known E. faecalis Infections: Ca(OH)2 is less effective; consider 2% chlorhexidine (CHX) as a supplementary irrigant or medicament.
• Severe Anatomic Complexities: In cases with fins, webs, or C-shaped canals, Ca(OH)2 may not penetrate effectively; activated irrigation is more critical.

The optimal duration for calcium hydroxide medicament is 7 to 14 days for routine disinfection of necrotic canals, while apexification protocols require placement for 3 to 6 months. The antibacterial effect is not immediate; it relies on the sustained release of hydroxyl ions to raise the environmental pH, a process that takes several days to reach maximum efficacy within the dentinal tubules.

While a minimum of 7 days is needed for its antimicrobial action, extending the duration beyond 4 weeks in standard cases offers no additional benefit and increases the risk of dentinal weakening. After medicament removal, the canal is ready for final shaping with rotary files and obturation with gutta percha points.

• Routine Disinfection: A 7-day period is sufficient to eliminate most common endodontic pathogens.
• Persistent Infection/Exudation: A 14-day application may be necessary to resolve stubborn symptoms.
• Apexification: Requires 3-6 months, with the paste being replaced every 1-3 months to maintain its potency.
• Inflammatory Resorption: An initial placement of 4 weeks is typically required to arrest resorptive cell activity.

The choice of vehicle—aqueous (like saline) or viscous (like glycerin)—directly impacts the rate of ionic dissociation and therefore dictates the clinical application. The vehicle determines the paste's flow, handling characteristics, and how quickly it exerts its biological effect within the root canal system prepared by an endo motor.

Aqueous vehicles allow for rapid dissociation, leading to a fast but short-lived antimicrobial action. In contrast, viscous vehicles slow down the release of hydroxyl ions, providing a sustained effect suitable for long-term treatments. Most pre-mixed commercial pastes available in India use a viscous vehicle for ease of use and suitability for a broader range of cases, including those requiring longer medication periods before using obturation systems.

• Aqueous Vehicles (e.g., Saline, Anesthetic Solution): Provide rapid ion release. Best for short-term use (1-2 weeks) in standard disinfection cases.
• Viscous Vehicles (e.g., Glycerin, Propylene Glycol): Ensure slow, sustained ion release. Indicated for long-term applications like apexification or resorption.
• Premixed Syringes: Offer convenience and controlled placement but are less customizable than chairside mixing.
• Chairside Mixing: Allows the clinician to control consistency, but achieving a homogenous, void-free mix is technique-sensitive.