Evaluation of the genotoxicity and cytotoxicity of filling pastes used for pulp therapy on deciduous teeth using the micronucleus test on bone marrow from mice (Mus musculus)

Abstract

Pulp therapy is the last resort for preserving deciduous teeth. However, the genotoxic and cytotoxic effects of many products used in this therapy are not well established. The aim of this study was to use the micronucleus test on bone marrow from mice to evaluate the genotoxic and cytotoxic effects of four filling pastes: zinc oxide, calcium hydroxide P.A., mineral trioxide aggregate and an iodoform paste (iodoform + camphorated + paramonochlorophenol + rifamycin + prednisolone). Male Swiss mice were divided into 4 groups of 10 animals, each exposed to one of the pastes, and were subdivided according to the dilutions tested: 1/10, 1/50, 1/500 and 1/1000 administered intraperitoneally (0.1ml/10g of weight). Cyclophosphamide was the positive control. The negative controls were dimethylsulfoxide and buffered saline solution. Five animals were killed 24h and five 48h after the treatment. The material was processed in accordance with Schmid (1976) and micronuclei were counted in 1000 polychromatic erythrocytes (PCE), under an optical microscope in a blinded test. Cytotoxicity was evaluated using the PCE/normochromatic erythrocyte (NCE) ratio in 200 erythrocytes. The micronucleus analysis results were evaluated using the conditional test for comparing proportions in situations of rare events. Analysis of variance and Tukey's test were used to evaluate the PCE/NCE ratio. There was significantly greater occurrence of micronuclei in the animals treated with iodoform paste at all the dilutions tested, at both sacrifice times. Greater occurrence of micronuclei was observed among the animals treated with zinc oxide and sacrificed 48h after the treatment, at the dilutions 1:50; 1:500 and 1:1000. Calcium hydroxide P.A. and mineral trioxide aggregate did not present any genotoxic or cytotoxic effects. The genotoxicity and cytotoxicity of zinc oxide and iodoform paste revealed here constitute an initial step towards their contraindication, but additional studies will be necessary in order to securely establish the risks involved in their use.

Evaluation of the Genotoxicity of Endodontic Materials for Deciduous Teeth Using the Comet Assay

“…Concerning the potential of products containing zinc oxide or iodoform pastes, there is a scarcity of studies, especially those with the comet methodology. Pires et al [19] showed that comet assay revealed that iodoform paste did not damage DNA either Guedes Pinto paste, but Santos et al [12] found genotoxic potential, translated as a higher frequency of micronuclei.…”

“…To deciduous pulp therapy, the paste must be resorbable, provide radiopacity, not interfere with the successor tooth germ's development, and be biocompatible with periapical tissue [1,[3][4][5]. Additionally, it is expected that an ideal filling material does not induce genotoxic and/or cytotoxic effects, but also there's also no consensus on such effects in the studies [6][7][8][9][10][11][12][13][14][15][16][17].…”

“…Genotoxicity of mineral trioxide aggregate (MTA) and calcium hydroxide P.A. (pro-analysis) has not been reported, with no greater occurrence of DNA damage [6,9,12,18,19]. Concerning the potential of products containing zinc oxide or iodoform pastes, there is a scarcity of studies, especially those with the comet methodology.…”

In vitro self‐setting properties, bioactivity, and antibacterial ability of a silicate‐based premixed bone cement

“…Ideally, the root canal filling material should be biocompatible, antibacterial, stable, and easy to operate in order to avoid any complication involved during or after operation . Numerous materials, such as zinc oxide‐eugenol cement, iodoform paste, and calcium hydroxide, have been used as root canal filling materials. However, they cannot meet all the above requirements.…”

“…For instance, zinc oxide‐eugenol cement is lack of antibacterial activity . The biocompatibility of iodoform paste still needs improvement . Calcium hydroxide, which is one of the most commonly used capping materials, frequently presents disadvantages such as the low hardness and dissolution that will result in a loose filling .…”