Director of the Postgraduate Endodontic Program, Department of Endodontics, Sheba Medical Center, Tel HaShomer (Israel); Lecturer at Medical Consulting Group (Moscow)
In Russia, medications containing iodoform are widely used in the treatment of apical periodontitis, despite a clear lack of scientific evidence supporting their effectiveness in endodontics.
The aim of this article is to briefly review scientific publications on the efficacy of iodoform-based medications in combating endodontic infection.
It is shown that iodoform has only short-term antimicrobial activity and quickly loses its effectiveness upon contact with organic substances.
Furthermore, adding iodoform to calcium hydroxide paste does not increase its antibacterial properties and may lead to undesirable effects. Based on this, the author does not recommend the use of iodoform as a treatment for apical periodontitis.
For a long time, dentists believed in the miraculous properties of iodoform—especially its broad antibacterial spectrum and long-lasting effect: even long after use, the characteristic smell can still be detected upon re-entering the canal!
Iodoform gained the most popularity in South America under the influence of Dr. O.A. Maisto, a pioneer in South American endodontics and pediatric dentistry. To this day, many pediatric dentists around the world use the Maisto paste (Maisto O.A., Capurro M.A., 1964), which contains iodoform and is prepared ex tempore. The appeal lies in the paste’s ability to dissolve over time without interfering with the physiological root resorption of primary teeth (Maisto O.A., Erausquin J., 1965).
For many years, iodoform-containing pastes were recommended as antiseptics (Walton J.G. et al., 1989), due to iodine release when in contact with exudate or endodontic infection (Pucci F.M., 1945; Castagnola L., Orlay H.G., 1952).
Some practitioners believe so strongly in iodoform’s antibacterial properties that they even add it to AH 26 (based on personal observations in Israel and anecdotal accounts from Argentinian and Brazilian dentists). In Russia, it has even been mixed into phosphate cement (according to online reports).
In 1999, Daniel, Jaeger, and Machado published a review article titled "Use of Iodoform in Endodontics", in which they found no laboratory or clinical studies justifying the use of iodoform in the treatment of apical periodontitis. And thus, the legend began to unravel.
What do we actually know about iodoform?
Iodoform (triiodomethane – CHI₃; molecular weight – 393.78; atomic weight – 126.9044) is a lemon-yellow powder with bright hexagonal crystals, a penetrating persistent odor, poorly soluble in water (1:10,000), soluble in alcohol (1:60) and ether (1:75).
It dissolves in fatty acids, is unstable, and easily decomposes when interacting with organic substances. Its antibacterial action stems from this breakdown process, which releases iodine upon contact with organic matter (Pucci F.M., 1945).
Thus, the smell has nothing to do with its antibacterial effectiveness! Iodine-containing compounds are widely used in dentistry for disinfection. The iodine provides potency by precipitating proteins and oxidizing enzymes. However, in the presence of organic or inorganic materials, iodine’s activity quickly diminishes (Estrela C., 2004).
Endodontic literature supports this. A 1990 study showed that iodine-based products destroy microbes in a very short time (Safavi E. et al., 1990). These findings were confirmed by a later study (Lin S. et al., 2009).
Markus Haapasalo’s group, and his leading student Isabella Portenier (who earned her PhD on this topic), demonstrated in a series of studies (Haapasalo H.K. et al., 2000; Portenier I. et al., 2001) that powdered dentin quickly neutralizes the antibacterial effect of iodine-based compounds. Organic dentin matrix and heat-killed E. faecalis and C. albicans also slowly inhibit their action.
An indirect indicator of iodoform’s weak and short-lived antibacterial action is the marketplace itself: iodoform is never sold alone but always combined with calcium hydroxide—e.g., Metapex, Vitapex, Diapex, Endoflass. Meanwhile, pure calcium hydroxide products are plentiful (Belyaeva T.S., Bolyachin A.V., 2010).
But clinicians want microbial data! C. Estrela (2006) tested S. aureus, E. faecalis, P. aeruginosa, B. subtilis, and C. albicans using an agar diffusion test with these agents:
Ca(OH)2 in saline;
Ca(OH)2 + iodoform;
Pure iodoform.
The results showed that the first two groups had similar effectiveness, while pure iodoform had no antimicrobial action.
A direct contact test showed the same: both the calcium hydroxide and the calcium hydroxide + iodoform groups were equally effective, while pure iodoform had no effect on either mixed microbes or B. subtilis alone.
Conclusion: Iodoform does not enhance the antimicrobial properties of calcium hydroxide.
A Brazilian research group tested pastes composed of calcium hydroxide/camphorated paramonochlorophenol/glycerin with varying iodoform content on obligate anaerobes. They found that adding iodoform did not change the paste’s antimicrobial properties (Siqueira Jr J.F. et al., 1997).
A pediatric dentistry study (Reddy S., Ramakrishna Y., 2007) isolated 23 bacterial species from primary molars with apical periodontitis. These materials were tested:
Zinc oxide-eugenol (ZOE);
ZOE + formocresol;
гCa(OH)₂ in sterile water;
Zinc oxide + camphorated phenol;
Ca(OH)₂ + iodoform (Metapex);
Vaseline (control).
The weakest effect (aside from Vaseline) was seen in Metapex!
A similar result was found in 2008 (Blanscet M.L. et al., 2008), using calcium hydroxide powder in saline (UltraCal XS) vs. Vitapex. Agar diffusion showed Vitapex had the smallest inhibition zone!
In other words, in these studies, Vitapex and Metapex performed worse than pure calcium hydroxide!
Speculative Hypothesis: The silicone oil in such products may interfere with calcium hydroxide’s dissociation, impairing its function. But laboratory results can’t fully mimic clinical situations—so one cannot completely dismiss the antimicrobial potential of iodine-based materials.
Some literature notes brief but intense (Kvist T. et al., 2004) and deep (penetrating dentinal tubules) action from iodine-containing agents (Fuss Z. et al., 2002).
However, the downsides of iodine-based products include:
Potential allergic reactions (Hensten A., Jacobsen N., 2005; Ijima S., Kuramochi M., 2002);
Tooth tissue staining (Kupietzky A. et al., 2003);
Impaired adhesion of epoxy sealers to dentin (Bartanovsky E., Solomonov M. et al., 2014).
Conclusion: Iodoform-based products do not offer long-lasting or broad-spectrum antimicrobial action. They may trigger allergies and impair sealer adhesion. Therefore, I do not recommend using iodoform as a first-line treatment for apical periodontitis.
P.S. This article was published in the journal Endodontia. Special thanks to Editor-in-Chief Alexey Bolyachin for providing the material. Some doctors believe so strongly in iodoform’s properties that they even add it to AH 26 (based on observations in Israel and tales from Argentine and Brazilian doctors). In Russia, it’s even been mixed into phosphate cement.