Evidence of genotoxicity and cytotoxicity of X-rays in the oral mucosa epithelium of adults subjected to cone beam computed tomography.

Abstract

Free AccessLetter to the EditorEvidence of genotoxicity and cytotoxicity of X-rays in the oral mucosa epithelium of adults subjected to cone beam computed tomographyDaniel RibeiroDaniel RibeiroUniversidade Federal De Sao Paulo (UNIFESP),Santos, San Paulo, BrazilSearch for more papers by this authorPublished Online:25 Jun 2019https://doi.org/10.1259/dmfr.20180299SectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail AboutI read the recent paper of da Fonte and colleagues1 published in Dentomaxillofacial Radiology entitled “Evidence of genotoxicity and cytotoxicity of X-rays in the oral mucosa epithelium of adults subjected to cone beam CT” with much interest. In this article, the authors were able to detect high frequencies of micronuclei and other metanuclear alterations indicative of cytotoxicity in adults submitted to cone beam CT. However, this study has some questions that must be mentioned for better understanding the paper. First, it is important to stress that Papanicolaou technique is not recommended when evaluating micronucleated cells since it is not specific for staining nucleic acids. For this purpose, Feulgen-Fast Green method has been considered as the best choice.2 Taking into consideration the absence of DNA specificity for the Papanicolaou stain, higher micronuclei frequencies are detected due to the presence of cell structures that resembling micronucleus, such as keratohyalin granules or bacteria.2 In this case, the counting of micronucleus will be overestimated. This may explain the high number of micronuclei presented in Figure 2 (mean of 4–10 micronucleated cells before exposure and 5–10 micronucleated cells after exposure per 1000 cells evaluated).Regarding cytotoxicity, the authors showed positive cytotoxicity induced by cone beam CT on buccal mucosa cells. It is important to stress that the micronucleus frequency decreases when cytotoxicity is increased, because micronucleated cells are lost due to the death. Herein, it would be interesting to show what metanuclear alterations evaluated in the study (pyknosis, karyolysis, and karyorrhexis) are increased by exposure to cone beam CT. This information is very important in order to identify the specific type of cell death induced by cone beam CT, inasmuch some of them are closely associated with necrosis whereas others are related to apoptosis.3Taken as a whole, the results of this study clearly demonstrate that mutagenicity and cytotoxicity are induced by cone beam CT on buccal mucosa cells. In the Discussion, the authors stated that “interpretation of the real clinical significance of these findings, and their relationship to a probable carcinogenic potential, should be made with parsimony, since the magnitude of the effects of radiation exposure depends primarily on the dose and frequency used, as well as on the individual's ability to repair such damage”. When mutagenicity and cytotoxicity are induced by some environmental source simultaneously, it is assumed that the initiation–promotion process is established, which denotes a condition of risk for carcinogenesis. Herein, further studies using medium-term oral carcinogenesis assay and cone beam CT are mandatory for clarifying the issue. Conversely, our research group has demonstrated that cone beam CT is able to induce cytotoxicity only in buccal mucosa cells.4,5 An earlier study conducted by Yang et al6 is fully in line with our published data, demonstrating that buccal mucosa cells, cells of the tongue or epithelial gingival cells exposed to the cone beam CT had no remarkable differences with respect to sensitivity to the radiation.I hope that such comments are useful for better understanding the interesting article investigating cytogenetic biomonitoring on oral mucosa cell induced by cone beam CT.Sincerely;Daniel Araki Ribeiro, DDS, PhDAssociate Professor and ResearcherDepartment of BiosciencesFederal University of Sao Paulo – UNIFESPE-mail: [email protected]Acknowledgment DAR is a recipient of CNPq (Conselho Nacional de Desenolvimento Cientifico e Tecnologico) fellowship.Conflict of Interests None declared.REFERENCES1. da Fonte JB, , Andrade TM, , Albuquerque RL, , de Melo MFB, , Takeshita WM. Evidence of genotoxicity and cytotoxicity of X-rays in the oral mucosa epithelium of adults subjected to cone beam CT. Dentomaxillofac Radiol 2018; 47: 20170160. doi: https://doi.org/10.1259/dmfr.20170160 Link ISI, Google Scholar2. Bonassi S, , Coskun E, , Ceppi M, , Lando C, , Bolognesi C, , Burgaz S, , et al.. The HUman MicroNucleus project on eXfoLiated buccal cells (HUMNXL): The role of life-style, host factors, occupational exposures, health status, and assay protocol. Mutation Research/Reviews in Mutation Research 2011; 728: 88–97. doi: https://doi.org/10.1016/j.mrrev.2011.06.005 Crossref Medline ISI, Google Scholar3. Cerqueira EM, , Gomes-Filho IS, , Trindade S, , Lopes MA, , Passos JS, , Machado-Santelli GM. Genetic damage in exfoliated cells from oral mucosa of individuals exposed to X-rays during panoramic dental radiographies. Mutat Res 2004; 562(1-2): 111–7. doi: https://doi.org/10.1016/j.mrgentox.2004.05.008 Crossref Medline ISI, Google Scholar4. Lorenzoni DC, , Fracalossi AC, , Carlin V, , Ribeiro DA, , Sant'anna EF. Mutagenicity and cytotoxicity in patients submitted to ionizing radiation. Angle Orthod 2013; 83: 104–9. doi: https://doi.org/10.2319/013112-88.1 Crossref Medline ISI, Google Scholar5. Carlin V, , Artioli AJ, , Matsumoto MA, , Filho HN, , Borgo E, , Oshima CT, , et al.. Biomonitoring of DNA damage and cytotoxicity in individuals exposed to cone beam computed tomography. Dentomaxillofac Radiol 2010; 39: 295–9. doi: https://doi.org/10.1259/dmfr/17573156 Link ISI, Google Scholar6. Yang P, , Hao S, , Gong X, , Li G. Cytogenetic biomonitoring in individuals exposed to cone beam CT: comparison among exfoliated buccal mucosa cells, cells of tongue and epithelial gingival cells. Dentomaxillofac Radiol 2017; 46: 20160413. doi: https://doi.org/10.1259/dmfr.20160413 Link ISI, Google ScholarAuthors' response to Letter to the Editor (DMFR-D-18-00299)Batista Melo da Fonte, Department of Dentistry, Master's Degree Program in Dentistry, Federal University of Sergipe, UFS, Aracaju, Brazil; Universidade Federal de Sergipe, BrazilFirstly I would like to thank Professor Ribeiro for the interesting considerations about my manuscript. As mentioned previously by Ribeiro, although the Papanicolaou technique is not specific for nucleic acid staining and the Feulgen-Fast Green method has recently been considered as a better alternative,1 it is important to note that several studies published in recent years have shown that the micronucleus count using Papanicolaou technique, even with its limitations, has been a reliable biomarker for oral cancer risk. In addition, exfoliative cytology and the Papanicolaou technique showed high sensitivity in the detection of dysplastic alterations of the oral mucosa, even in a subclinical phase, and therefore, it has been suggested that it can be used as a population screening for the early detection of oral precancerous changes, especially in high-risk individuals.2–6Thus, the detection of micronuclei in exfoliative cytology should be interpreted as recent exposure to carcinogens or as spontaneous errors during DNA replication. In addition, the micronucleus count makes possible the analysis of the possible genotoxic changes as a result of exposure to carcinogenic agents.7,8 Based on this assumption, the objective of our study was to use a feasible and economical method to identify the possible effects of X-rays on the oral mucosa epithelium of adults subjected to cone beam CT.The highest frequencies of micronuclei were observed in studies using the Giemsa and Aceto-orcein staining, confirming the low specificity of these stains to increase the number of false positives when compared to Papanicolaou staining and the use of specific DNA stains as the method of Feulgen.9,10 However, this method is an economically less viable method than Papanicolaou staining, its execution is difficult and time-consuming compared to other conventional staining techniques. Another disadvantage of its use is dye instability.Although the technique employed in our study may, in fact, increase the probability of false-positives, the morphological analysis was performed meticulously by a pathologist with experience of about 20 years in cytopathology. In addition, the criteria adopted for morphological analysis were established by Tolbert et al.11 The criteria used included only the cells that had the normal and intact nuclei, with a smooth and distinct nuclear perimeter, and that presented the cytoplasm. In addition, for micronuclei counting, the criterion used was the presence of a surrounding halo representative of a membrane, less than one-third of the associated core diameter but large enough to discern shape and colour, no overlap or bonding with the nucleus, intensity of coloration similar to the nucleus and even focal plane.Thus, the variations of the frequency of micronuclei found in this study should not be considered indicative of the absence of probability of cytogenetic alterations resulting of radiation exposure during cone beam CT. However, we agree that further studies should be performed to clarify the issue, using specific experimental models, as suggested by Professor Ribeiro.Sincerely;Juliana Batista Melo da Fonte, DDS, MSD e-mail: [email protected]Acknowledgment DAR is a recipient of CNPq (Conselho Nacional de Desenolvimento Cientifico e Tecnologico) fellowship.Conflict of Interests None declared.REFERENCES1. Bonassi S, , Coskun E, , Ceppi M, , Lando C, , Bolognesi C, , Burgaz S, , et al.. The HUman MicroNucleus project on eXfoLiated buccal cells (HUMN(XL)): the role of life-style, host factors, occupational exposures, health status, and assay protocol. Mutat Res 2011; 728: 88–97. doi: https://doi.org/10.1016/j.mrrev.2011.06.005 Crossref Medline ISI, Google Scholar2. Rajput DV, , Tupkari JV. Early detection of oral cancer: PAP and AgNOR staining in brush biopsies. J Oral Maxillofac Pathol 2010; 14: 52–8. doi: https://doi.org/10.4103/0973-029X.72501 Crossref Medline, Google Scholar3. Dindgire SL, , Gosavi S, , Kumawat RM, , Ganvir S. Frequency in Potentially Malignant and Malignant Lesions. International Journal of Oral and Maxillofacial Pathology 2012; 3: 15–20. Google Scholar4. Chitturi R, , Rathinam E, , Santo R, , Yoithapprabhunath T. The role of exfoliative cytology and molecular biology in oral potentially malignant disorders. Journal of Health Research and Reviews 2017; 4: 43–6. doi: https://doi.org/10.4103/jhrr.jhrr_22_17 Crossref, Google Scholar5. H Alsarraf A, , Kujan O, , Farah CS. The utility of oral brush cytology in the early detection of oral cancer and oral potentially malignant disorders: A systematic review. J Oral Pathol Med 2018; 47: 104–16. doi: https://doi.org/10.1111/jop.12660 Crossref Medline ISI, Google Scholar6. Thakur M, , Guttikonda VR. Modified ultrafast Papanicolaou staining technique: A comparative study. J Cytol 2017; 34: 149–53. doi: https://doi.org/10.4103/JOC.JOC_23_16 Crossref Medline ISI, Google Scholar7. Agarwal M, , Sunitha JD, , Dawar G, , Rallan NS. Micronuclei assay of exfoliated oral mucosal cells: a review. Annals of Dental Specialty 2014; 2: Apr–Jun 2014. Google Scholar8. Shashikala R, , Indira AP, , Manjunath GS, , Rao KA, , Akshatha BK. Role of micronucleus in oral exfoliative cytology. J Pharm Bioallied Sci 2015; 7(Suppl 2): S409–S413. doi: https://doi.org/10.4103/0975-7406.163472 Medline, Google Scholar9. Nersesyan A, , Kundi M, , Atefie K, , Schulte-Hermann R, , Knasmüller S. Effect of staining procedures on the results of micronucleus assays with exfoliated oral mucosa cells. Cancer Epidemiol Biomarkers Prev 2006; 15: 1835–40. doi: https://doi.org/10.1158/1055-9965.EPI-06-0248 Crossref Medline ISI, Google Scholar10. Bolognesi C, , Knasmueller S, , Nersesyan A, , Thomas P, , Fenech M. The HUMNxl scoring criteria for different cell types and nuclear anomalies in the buccal micronucleus cytome assay - an update and expanded photogallery. Mutat Res 2013; 753: 100–13. doi: https://doi.org/10.1016/j.mrrev.2013.07.002 Crossref Medline ISI, Google Scholar11. Tolbert PE, , Shy CM, , Allen JW. Micronuclei and other nuclear anomalies in buccal smears: methods development. Mutat Res 1992; 271: 69–77. doi: https://doi.org/10.1016/0165-1161(92)90033-I Crossref Medline ISI, Google Scholar Previous article FiguresReferencesRelatedDetailsCited byCan exposure to panoramic radiographs induce genotoxic effects on the oral epithelium? A systematic review with meta-analysisMarcos Antônio Lima dos Santos, Graziane Ribeiro Couto, Mark Jon Santana Sabey, Danilo de Paula Ribeiro Borges and Wilton Mitsunari Takeshita28 July 2021 | Dentomaxillofacial Radiology, Vol. 51, No. 2 Volume 48, Issue 6September 2019 © 2019 The Authors. Published by the British Institute of Radiology History ReceivedAugust 17,2018AcceptedSeptember 17,2018Published onlineJune 25,2019 Metrics Download PDF