Modern dentistry has evolved significantly due to advances in biomaterials, bioactive cements, and evidence-based protocols.
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This article reviews the main materials that should no longer be routinely used in endodontics and pediatric dentistry, including formocresol, paraformaldehyde, arsenical compounds, hydrogen peroxide, and amalgam retrofillings.
✅ Introduction
The evolution of endodontic and pulp therapy procedures has been strongly influenced by scientific research and biomaterial innovation. Historically, many dental materials were introduced before modern biocompatibility standards existed. While some provided short-term clinical success, long-term studies later demonstrated important disadvantages such as tissue toxicity, inflammatory reactions, leakage, and poor regenerative capacity.
Today, minimally invasive and biologically driven dentistry prioritizes materials capable of preserving pulp vitality, stimulating dentin formation, and promoting tissue repair. Consequently, numerous traditional substances have been abandoned or significantly restricted.
Understanding which materials are outdated is essential for both clinicians and dental students in order to avoid complications and improve treatment prognosis.
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Several factors contribute to the discontinuation or restriction of materials in endodontics and pulp therapy:
▪️ Cytotoxicity to pulpal or periapical tissues.
▪️ Mutagenic or carcinogenic potential.
▪️ Poor sealing ability.
▪️ Tissue necrosis.
▪️ Chronic inflammatory reactions.
▪️ Inferior clinical outcomes compared with modern biomaterials.
▪️ Availability of safer and more bioactive alternatives.
Modern dentistry increasingly favors materials that are:
▪️ Bioactive.
▪️ Biocompatible.
▪️ Antibacterial.
▪️ Sealing.
▪️ Regenerative.
▪️ Stable over time.
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Historical Use
Formocresol was widely used for decades in pulpotomy procedures of primary teeth because of its ability to fix and mummify pulpal tissue.
Why It Is No Longer Recommended
Current evidence has raised serious concerns regarding its biological safety.
Main Disadvantages
▪️ Contains formaldehyde.
▪️ Potential mutagenic and carcinogenic effects.
▪️ Systemic distribution after application.
▪️ Tissue fixation instead of true healing.
▪️ Chronic inflammatory response.
Current Alternatives
Modern pulpotomy protocols favor bioactive materials such as:
▪️ Mineral trioxide aggregate (MTA).
▪️ Biodentine.
▪️ Calcium silicate-based cements.
▪️ Bioceramic materials.
These materials stimulate dentin bridge formation and preserve healthier pulpal tissue.
2. Paraformaldehyde in Endodontics
Historical Use
Paraformaldehyde-containing pastes were used to devitalize inflamed pulps, especially in difficult anesthesia situations.
Why It Should Not Be Used
Paraformaldehyde is highly toxic and may diffuse beyond the root canal system.
Clinical Risks
▪️ Severe tissue necrosis.
▪️ Bone destruction.
▪️ Persistent pain.
▪️ Delayed healing.
▪️ Damage to periodontal structures.
▪️ Neurotoxicity in severe cases.
Because of these complications, modern endodontics strongly discourages its use.
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Historical Use
Arsenic compounds were historically employed to intentionally devitalize pulp tissue before root canal treatment.
Why They Are Obsolete
Arsenic is considered one of the most dangerous substances ever used in dentistry.
Serious Complications
▪️ Osteonecrosis.
▪️ Bone sequestration.
▪️ Gingival necrosis.
▪️ Periodontal destruction.
▪️ Severe inflammatory reactions.
▪️ Irreversible tissue damage.
Modern anesthesia and rotary instrumentation have completely eliminated the need for arsenical compounds.
4. Hydrogen Peroxide in Endodontics
Previous Use
Hydrogen peroxide was previously combined with sodium hypochlorite during root canal irrigation because of its bubbling effect.
Why It Is No Longer Recommended
Although it creates effervescence, hydrogen peroxide does not effectively dissolve organic tissue or calcium hydroxide remnants.
Main Problems
▪️ Oxygen bubble formation.
▪️ Risk of emphysema.
▪️ ▪️ Reduced effectiveness of sodium hypochlorite.
▪️ Limited antimicrobial effectiveness compared with modern irrigants.
▪️ Potential extrusion into periapical tissues.
Current Irrigation Protocols
Modern endodontics primarily uses:
▪️ Sodium hypochlorite (NaOCl).
▪️ EDTA 17%.
▪️ Chlorhexidine in selected situations.
▪️ Sonic or ultrasonic irrigation activation.
5. Zinc Oxide Eugenol Directly Over Permanent Pulp Tissue
Historical Use
Zinc oxide eugenol (ZOE) was commonly used as a sedative base and temporary restorative material.
Limitations in Vital Pulp Therapy
Although still useful in some restorative applications, direct contact with pulp tissue is no longer preferred.
Problems
▪️ Cytotoxic effect of eugenol.
▪️ Chronic pulpal irritation.
▪️ Inferior dentin bridge formation.
▪️ Reduced regenerative capacity.
Better Alternatives
▪️ MTA.
▪️ Biodentine.
▪️ Bioceramic liners.
These materials provide superior sealing and biological repair.
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The transition from traditional dental materials to modern bioactive biomaterials reflects the growing emphasis on biological preservation and minimally invasive dentistry. Contemporary evidence demonstrates that many older substances once considered acceptable can negatively affect pulp vitality, periapical healing, and long-term treatment success.
Among all obsolete materials, arsenical compounds and paraformaldehyde represent the most hazardous due to their destructive potential. Likewise, formocresol remains controversial because of its formaldehyde content and systemic concerns.
Modern bioactive materials such as MTA and Biodentine have significantly improved outcomes in both adult and pediatric dentistry by promoting tissue regeneration rather than tissue fixation or necrosis.
🎯 Clinical Recommendations
▪️ Avoid outdated devitalizing agents.
▪️ Use bioactive materials whenever possible.
▪️ Prioritize minimally invasive pulp therapy.
▪️ Follow evidence-based irrigation protocols.
▪️ Use sodium hypochlorite and EDTA instead of hydrogen peroxide.
▪️ Select bioceramic materials for pulp capping and apical surgery.
▪️ Continuously update clinical protocols according to current literature.
✍️ Conclusion
Several materials historically used in endodontics and pulp therapy are now considered obsolete because of their toxicity, poor biological behavior, and inferior clinical outcomes. Modern dentistry favors biocompatible and regenerative materials capable of preserving pulp vitality and improving long-term success.
Clinicians should avoid the routine use of substances such as formocresol, paraformaldehyde, arsenic compounds, and hydrogen peroxide in endodontic procedures. Instead, evidence-based biomaterials like MTA, Biodentine, and calcium silicate cements should be prioritized to ensure safer and more predictable treatments.
📚 References
✔ Torabinejad M, Parirokh M. Mineral trioxide aggregate: a comprehensive literature review. Part II: Leakage and biocompatibility investigations. Journal of Endodontics. 2010;36(2):190-202.
✔ American Academy of Pediatric Dentistry. Pulp therapy for primary and immature permanent teeth. Pediatric Dentistry. 2024;46(6):399-407. Siqueira JF, Rôças IN. Clinical implications and microbiology of bacterial persistence after treatment procedures. Journal of Endodontics. 2008;34(11):1291-1301.
✔ Estrela C, Estrela CRA, Decurcio DA, Hollanda ACB, Silva JA. Antimicrobial efficacy of ozonated water, gaseous ozone, sodium hypochlorite and chlorhexidine in infected human root canals. International Endodontic Journal. 2007;40(2):85-93.
✔ Parirokh M, Torabinejad M. Mineral trioxide aggregate: a comprehensive literature review. Part I: Chemical, physical, and antibacterial properties. Journal of Endodontics. 2010;36(1):16-27.
✔ Fuks AB. Current concepts in vital primary pulp therapy. European Journal of Paediatric Dentistry. 2002;3(3):115-120.
✔ Haapasalo M, Shen Y, Wang Z, Gao Y. Irrigation in endodontics. British Dental Journal. 2014;216(6):299-303.
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