Formocresol: Is It Still Used in Dentistry?

Formocresol has been widely used in pediatric pulp therapy, but concerns over its safety and effectiveness have led to ongoing debate. Questions regarding potential toxicity and long-term effects continue to influence its use worldwide.

Examining its components, mechanism of action, tissue response, and interactions with other materials helps determine whether formocresol remains a viable option in contemporary dentistry.

Key Components

Formocresol is a combination of formaldehyde, cresol, glycerin, and water, each contributing to its function as a devitalizing and fixative agent. Formaldehyde, around 19% of the formulation, acts as the primary antimicrobial and tissue-fixing component by cross-linking proteins, halting bacterial proliferation, and preserving pulp tissue. However, its cytotoxicity and potential systemic effects have raised concerns.

Cresol, approximately 35% of the mixture, enhances bactericidal properties by disrupting microbial cell membranes, preventing infection within the pulp chamber. It also aids tissue fixation, though less aggressively than formaldehyde. Together, these agents sterilize and mummify pulp tissue, reducing bacterial reinfection risks.

Glycerin improves handling and reduces volatility, stabilizing the solution and controlling formaldehyde and cresol penetration to prevent excessive necrosis. It also adds viscosity, ensuring the material stays in place on exposed pulp tissue. Water acts as a solvent, maintaining homogeneity and facilitating application.

Mechanism in Pulp Therapy

Formocresol works by fixation and devitalization, balancing bacterial suppression with tissue preservation. When applied to exposed pulp, formaldehyde rapidly penetrates cells, inducing protein denaturation and coagulation. This stabilizes the remaining pulp, halting enzymatic activity and microbial growth. The depth of penetration depends on application duration and pulp condition.

A gradient of tissue fixation forms, with superficial layers undergoing complete coagulation while deeper regions retain partial vitality. This coagulation necrosis zone limits bacterial invasion while preserving underlying radicular pulp. Unlike agents that induce complete devitalization, formocresol maintains a semi-fixed state, contributing to the long-term retention of primary teeth.

Despite histological evidence of chronic inflammation in deeper pulp layers, formocresol’s antimicrobial properties support long-term success in pulpotomy procedures. The gradual breakdown of fixed tissue components allows controlled healing, maintaining pulp function without excessive resorption. However, concerns over systemic absorption and toxicity continue to drive research into safer alternatives.

Tissue Response Features

Formocresol application triggers structural changes in pulp tissue. Formaldehyde induces coagulation necrosis in superficial layers, forming a dense fixation zone that impedes bacterial infiltration while preserving deeper structures. The extent of fixation depends on exposure time, concentration, and pulp condition.

Beneath the fixation zone, partially viable pulp tissue shows mild degenerative changes. Histological studies document fibroblastic activity, indicating some metabolic function despite formocresol presence. Inflammatory cells in deeper pulp layers suggest a localized response, though this does not always lead to clinical failure. Longitudinal studies show many treated primary teeth remain stable until exfoliation.

Pediatric Dentistry Considerations

Formocresol has been a widely used pulpotomy medicament in pediatric dentistry due to its ability to maintain primary teeth function until exfoliation. Its ease of use and high success rates have contributed to its continued presence in clinical practice. However, concerns about systemic formaldehyde exposure in young patients have led many practitioners to reconsider its use.

Regulatory bodies and dental associations have acknowledged these concerns, prompting research into safer alternatives such as ferric sulfate, mineral trioxide aggregate (MTA), and calcium silicate-based cements. Studies suggest these materials offer similar or superior outcomes in pulp vitality preservation and reduced inflammatory responses. The American Academy of Pediatric Dentistry (AAPD) recognizes these alternatives, though formocresol remains an accepted treatment in certain cases.

Interactions With Other Dental Materials

Formocresol’s compatibility with other dental materials affects its practicality in restorative procedures. Its protein-fixing and antimicrobial properties can influence subsequent restorations, particularly base and liner materials like calcium hydroxide and MTA. Residual formaldehyde may interfere with setting reactions, potentially affecting adhesive strength and stability.

Chemical fixation alters dentin properties, impacting bonding with restorative materials such as composite resins and glass ionomer cements. Some studies suggest formocresol-exposed dentin has reduced permeability, affecting adhesive penetration. While this may decrease microleakage, it could also compromise mechanical retention. Clinicians must carefully select restorative materials to ensure compatibility with the altered tissue environment.