"New age" pulp therapy: personal thoughts on a hot debate

This article outlines the counterpoint delivered in the debate "Is Formocresol Obsolete?" It addresses the opinion supporting the need to move away from formaldehyde-containing preparations in the dental care of children. It is suggested that such a move should be made not just because of concerns relating to the possible toxicity of formaldehyde but to reflect a more contemporary, biologic approach to pulp therapy in the primary dentition.

Is formocresol obsolete? A fresh look at the evidence concerning safety issues

Concern has been expressed about the safety of formocresol use in pediatric dentistry Formaldehyde, a primary component in formocresol, is a hazardous substance and is considered a probable human carcinogen by the International Agency for Research on Cancer, Health Canada, the Agency for Toxic Substances and Disease Registry in the U.S. Department of Health and Human Services, and the U.S. Environmental Protection Agency Humans inhale and ingest formaldehyde daily however, and produce formaldehyde during cellular metabolism. The human body is physiologically equipped to handle formaldehyde through multiple conversion pathways. The resultant single carbon atom released during metabolism is deposited in the "1-carbon pool," which, in turn, is used for the biosynthesis of macromolecules including DNA and RNA. Reevaluation of earlier research that examined potential health risks associated with formaldehyde exposure has shown that this research was based on flawed assumptions, which resulted in erroneous conclusions. The purpose of this review was to examine more recent research about formaldehyde metabolism, phormacokinetics, and corcinogenicity. These results indicated that formaldehyde is probably not a potent human carcinogen under low exposure conditions. Extrapolation of these research results to pediatric dentistry suggests an inconsequential risk associated with formaldehyde use in pediatric pulp therapy/

Genetic damage in human peripheral lymphocytes exposed to antimicrobial endodontic agents

OBJECTIVE

Formocresol, paramonochlorophenol, or calcium hydroxide have been widely used in dental practice to eradicate bacteria and consequently to produce root canal disinfection. Taking into consideration strong evidence for a relationship between DNA damage and carcinogenesis, the purpose of the present study was to evaluate the genotoxic effects of antimicrobial endodontic compounds in human peripheral lymphocytes by single-cell gel (comet) assay. This technique detects DNA strand breaks in individual cells.

STUDY DESIGN

A total of 10 microL of the tested substance solution (formocreso1, paramonochlorofeno1, and calcium hydroxide at 100-microg/mL concentration) was added to human peripheral lymphocytes from 10 volunteers for 1 hour at 37 degrees C. The negative control group was treated with vehicle control (PBS) for 1 hour at 37 degrees C, as well. For the positive control group, lymphocytes were exposed to hydrogen peroxide at 100 microM during 5 minutes on ice.

RESULTS

No DNA breakage was detected after a treatment of peripheral lymphocytes by formocresol, paramonochlorophenol, or calcium hydroxide at 100 microg/mL.

CONCLUSIONS

In summary, our results indicate that exposure to formocresol, paramonochlorophenol, or calcium hydroxide may not be a factor that increases the level of DNA lesions in human peripheral lymphocytes as detected by single-cell gel (comet) assay.

Effect of formaldehyde on rat liver in doses used in pulpotomies

Many studies have questioned the toxic effects of formocresol, one of which is its systemic distribution. This study focused on determining whether there was risk of acute hepatic lesion after the use of intravenous formaldehyde in doses for multple pulpotomies in rats. Histological and biochemical changes were evaluated. Results showed that very high doses of formaldehyde injected into rats, doses that were much higher than those given for multiple pulp treatments in a single session in Pediatric Dentistry, showed no signs of liver toxicity.

Persuasive evidence that formocresol use in pediatric dentistry is safe

Concern has been expressed about the safety of formocresol use in pediatric dentistry. Formaldehyde, a primary component in formocresol, is a hazardous substance and is considered a probable human carcinogen by Health Canada. However, humans inhale and ingest formaldehyde daily and also produce this compound as part of normal cellular metabolism. The human body is physiologically equipped to handle this exposure through multiple pathways for oxidation of formaldehyde to formate and incorporation into biological macromolecules via tetrahydrofolate-dependent one-carbon biosynthetic pathways. Recent re-evaluation of earlier research that examined potential health risks associated with formaldehyde exposure has shown that the research was based on flawed assumptions, which resulted in erroneous conclusions. This review examines more recent research about formaldehyde metabolism, pharmacokinetics and carcinogenicity, the results of which indicate that formaldehyde is probably not a potent human carcinogen under conditions of low exposure. Extrapolation of these research results to pediatric dentistry suggests an inconsequential risk of carcinogenesis associated with formaldehyde use in pediatric pulp therapy. Areas for further investigation are suggested.

Assessment of genotoxicity of 14 chemical agents used in dental practice: Ability to induce chromosome aberrations in Syrian hamster embryo cells

To assess the genotoxicity of 14 chemical agents used as locally applied agents in dental practice, the ability of these agents to elicit chromosome aberrations was examined using Syrian hamster embryo (SHE) cells. Chromosome aberrations in SHE cells were induced by treatment with three of eight chemical agents used as endodontic medicaments, i.e. ethylenediaminetetraacetic acid (EDTA), formocresol (a mixture of formalin and tricresol), and sodium arsenite. The other five chemical agents, i.e. chloramphenicol, p-chlorophenol, p-phenolsulfonic acid, sodium hypochlorite, and tetracycline hydrochloride exhibited a negative response for chromosome aberrations. Assessment of three dyes used for disclosing dental plaque showed chromosome aberrations induced by basic fuchsin but not by acid fuchsin and erythrosine B. Three local anesthetics, lidocaine hydrochloride, prilocaine hydrochloride, and procaine hydrochloride, were negative for chromosome aberrations. Among the ten chemical agents that exhibited a negative response in the assay, p-chlorophenol, sodium hypochlorite, and erythrosine B induced chromosome aberrations in SHE cells when treated in the presence of exogenous metabolic activation. The percentages of cells with polyploidy or endoreduplication were enhanced by formocresol, sodium arsenite, p-chlorophenol, p-phenolsulfonic acid, sodium hypochlorite, erythrosine B, prilocaine hydrochloride, and procaine hydrochloride in the absence or presence of exogenous metabolic activation. Our results indicate that the chemical agents that had a positive response in the present study are potentially genotoxic to mammalian cells.

Genotoxicity of antimicrobial endodontic compounds by single cell gel (comet) assay in Chinese hamster ovary (CHO) cells

OBJECTIVE

In the current study, the potential DNA damage associated with exposure to a number of antimicrobial endodontic compounds was assessed by the single cell gel (comet) assay in vitro.

STUDY DESIGN

Chinese hamster ovary (CHO) cells were exposed to formocresol, paramonochlorophenol, calcium hydroxide, or chlorhexidine at final concentration ranging from 0.01% to 1%.

RESULTS

Formocresol, paramonochlorophenol, and calcium hydroxide, as well as chlorhexidine in all concentrations tested did not contribute to the DNA damage.

CONCLUSION

These findings are clinically relevant since they represent an important contribution to the correct evaluation of the potential health risk associated with exposure to dental agents.

Lack of Genotoxicity of Formocresol, Paramonochlorophenol, and Calcium Hydroxide on Mammalian Cells by Comet Assay

Formocresol, paramonochlorophenol, and calcium hydroxide are widely used in dentistry because of their antibacterial activities in root canal disinfection. However, the results of genotoxicity studies using these materials are inconsistent in literature. The goal of this study was to examine the genotoxic potential of formocresol, paramonochlorophenol, and calcium hydroxide using mouse lymphoma cells and human fibroblasts cells in vitro by the comet assay. Data were assessed by Kruskal-Wallis nonparametric test. The results showed that all compounds tested did not cause DNA damage for the tail moment or tail intensity parameters. These findings suggest that formocresol, paramonochlorophenol, and calcium hydroxide do not promote DNA damage in mammalian cells and that the comet assay is a suitable tool to investigate genotoxicity.

The acute nephrotoxicity of systemically administered formaldehyde in rats

AIM

The purpose of this study was to assess the acute nephrotoxicity of formaldehyde, as it is believed to be the toxic component of formocresol.

METHODS

A sample of 24 Sprague-Dawley rats was used in the study and divided into 3 groups of 8 rats each. The following procedures were performed: group A) formaldehyde equivalent dose to 20 pulpotomies, injected into the main vein of each rat's tail; group B) formaldehyde equivalent dose to 100 pulpotomies injected; group C) control group with a saline solution injected. Blood analyses were performed after 24 and 48 hours to assess urea and creatinine levels. Urine samples were taken after 24 hours to analyse for LDH protein levels. Rats were sacrificed after 48 hours and histology samples of renal tissue were studied for any pathological defects.

RESULTS

Evaluation of histological samples of kidney tissue did not show any inflammation or other tissue lesions. No significant differences were found, using an ANOVA test procedure, among the variables of LDH protein or creatinine levels after 24 and 48 hours. Significant differences were found between the levels of urea and creatinine after 48 hours between the control group and the other test groups.

CONCLUSION

The use of formaldehyde at the usual clinical doses or with an amount equivalent to 100 pulpotomies did not produce renal tissue damage and the blood and urine factors analysed did not show significant changes after 48 hours in the experimental model used.

Formaldehyde in dentistry: a review for the millennium

This article reviews the history and use of formaldehyde in dentistry. Research from outside the dental field is included, particularly those articles that pertain to mutagenicity and carcinogenicity. The controversies over the use of formocresol continue, despite overwhelming research citing deleterious effects.

Pulpal tissue reaction to formocresol vs. ferric sulfate in pulpotomized rat teeth

The purpose of this study was to assess histologically the pulpal healing process after pulpotomies in rat teeth were done using two different agents: 20% dilution of formocresol (FMC) and ferric sulfate (FS). Two criteria were used: degree of inflammation and extent of pulpal involvement. Zinc oxide-eugenol paste (ZOE) or polycarboxylate cement (PCX) were placed to seal the cavity preparations. The maxillary first molars of 120 Sprague-Dawley rats were treated in this study and were divided into four groups: 1) FMC + ZOE, 2) FS + PCX, 3) FMC + PCX, and 4) FS + ZOE. After treatment the animals were sacrificed at weekly intervals for four weeks and pulpal response was evaluated according to the degree of inflammation. Other criteria were also evaluated: dentinal bridge formation, reparative dentin and odontoblastic layer. A Friedman test was performed to compare the results and find out if any differences could be found. FMC + ZOE group showed the least pulpal inflammation response, and the use of FS as an alternative agent for pulpotomies did not improve pulpal response.

The development of formocresol as a medicament for primary molar pulpotomy procedures

The development of formocresol as a pulpotomy medicament is charted from the 19th Century to the present day. While the solution has come in and out of vogue, few agents can seriously challenge its efficacy. Doubts about its toxicity, mutagenicity, and carcinogenicity have led, however, to a call for a more dilute formulation as well as a review of alternative medicaments. Problems arise in deriving an appropriate formula for a dilute version from existing formulations, which appear to have misinterpreted the concentration of constituents in the original solution.

Formocresol and alternative primary molar pulpotomy medicaments: a review

This paper reviews the history, clinical success and concerns regarding the safety of formocresol as a primary molar pulpotomy medicament. The alternatives to formocresol are discussed and their advantages and disadvantages evaluated.

Irritating effect of formocresol after pulpectomy in vivo

A study was carried out to investigate the effect of formocresol (formalin-creosote) on the periapical tissue after pulpectomy in rats. A pulpectomy was performed on the mesial root of the right mandibular first molar, and, in group A, a paper point containing saline was inserted into the root canal. In group B, a paper point containing formocresol was inserted, and in group C, a drop of formocresol was applied and a paper point containing formocresol was inserted into the root canal. The periapical tissue was examined histologically and histometrically at 3, 7, 14, and 28 days after insertion, and the inflammatory cells and fibroblasts in the apical granulation tissue were also counted. Histologically, in group A, the inflammation observed was slight at 14 and 28 days, while in groups B and C, a moderate inflammation remained. Histometrically, the area of the apical periodontal ligament in groups B and C was increased significantly compared with that in group A at 14 and 28 days. The inflammatory cell count in groups B and C increased significantly compared with that in group A at 7, 14, and 28 days, whereas the fibroblast count in Groups B and C decreased compared with that in Group A at 7, 14, and 28 days. These results demonstrate that formocresol delayed the healing of periapical tissue after pulpectomy.

Formocresol toxicity: is there a suitable alternative for pulpotomy of primary molars?

Some concern has been expressed in recent years about the use of formocresol for vital pulpotomy treatment of primary molars. This paper reviews the literature concerning the toxicity of formocresol and considers the evidence for the use of calcium hydroxide and glutaraldehyde. It is concluded that more work is required in this field before an alternative to formocresol can be recommended and that, in the meantime, a 1:5 dilution of the standard formocresol solution should be used but not included in the zinc oxide-eugenol sublining.

Comparison of antimicrobial and cytotoxic effects of glutaraldehyde and formocresol

The in vitro antimicrobial and cytotoxic concentrations of glutaraldehyde and formocresol were determined. Minimal antimicrobial concentrations of these two agents against selected microbial flora reported in carious primary teeth were 3.125% for glutaraldehyde and 0.75% for formocresol. At a doubling of these concentrations, most organisms, except Candida albicans, Staphylococcus epidermidis, and Streptococcus mutans, were killed by both substances in 30 seconds. Cytotoxicity was evaluated on tissue cultures of pulp fibroblasts and HeLa cells at minimal cidal concentrations and at 10- and 100-fold dilutions. Exposure of pulp fibroblasts and HeLa cells to formocresol and indirect exposure to vapors caused the cells to become atrophic and to form a less dense tissue pattern. Cells directly exposed to glutaraldehyde retained their normal cell shape and tissue pattern, whereas cells indirectly exposed to vapors continued to proliferate. These data showed effective antimicrobial activity at concentrations of 3.125% glutaraldehyde and 0.75% formocresol and suggested that glutaraldehyde may exert a less cytotoxic effect on the immediate and surrounding tissues when used as a pulpotomy agent.

Embryotoxicity and teratogenicity of formocresol on developing chick embryos

White Leghorn chick embryos were used to investigate the embryotoxicity and teratogenicity of 25 and 50% Buckley's formocresol. Embryos were injected at 48 h and sacrificed on the ninth day of incubation. The percentage of mortality of sham and vehicle controls was 4.8 and 17.7%, respectively, whereas eggs injected with 25 and 50% formocresol displayed a 40 and 100% mortality rate. Gross morphological abnormalities, weights, and crown-rump lengths were determined, demonstrating that Buckley's formocresol is embryotoxic and teratogenic in chick embryos. Gross morphological changes were noted to include cranial hematomas, facial abnormalities, eye and beak deformities as well as alterations in feather germ appearance. Histological changes included alterations in the organization of the eyes, and formation of the beak, palate, vasculature, musculature, cartilage, and bone. Moreover, experimental embryos displayed a retardation of development in that they lagged behind their controls by approximately 24 to 36 h.

A critical look at glutaraldehyde

Glutaraldehyde has been proposed as an alternative to formocresol in pulpotomy treatment of primary teeth. Data regarding effects of the two medicaments have been discussed in the literature, but little attention has been given to critical comparisons concerning parameters of toxicity, mutagenicity, and systemic distribution of the two agents. This paper reviews previous data on systemic distribution of glutaraldehyde and formocresol from pulpotomy sites, as well as cytotoxicity and mutagenicity of the agents. Comparisons reveal little difference between the agents on the parameters reviewed. The authors question the rationale for glutaraldehyde as an alternative to formocresol.

Differential sensitivity of normal human pulp and transformed mouse fibroblasts to cytotoxic challenge

Six different lines of diploid cells from human pulp and one commonly used transformed-cell line, L929 (a continuous fibroblast line of mouse lung connective tissue origin), were challenged by sera changes, an agar-overlay toxicity test and transfilter-histochemistry-toxicity test. The normal diploid cells showed greater sensitivity than transformed cells in each test. Although a different parameter of cell toxicity was measured in each test, the data indicate greater toxic response in diploid cells by all measurements. These normal diploid human cells are more appropriate cells for toxicity testing materials for human use.