Genetic damage in exfoliated cells from oral mucosa of individuals exposed to X-rays during panoramic dental radiographies

https://doi.org/10.1016/j.mrgentox.2004.05.008Get rights and content

Abstract

The genotoxic effects of X-ray emitted during dental panoramic radiography were evaluated in exfoliated cells from oral epithelium through a differentiated protocol of the micronucleus test. Thirty-one healthy individuals agreed to participate in this study and were submitted to this procedure for diagnosis purpose after being requested by the dentist. All of them answered a questionnaire before the examination. Cells were obtained from both sides of the cheek by gentle scrapping with a cervical brush, immediately before the exposure and after 10 days. Cytological preparations were stained according to Feulgen–Rossenbeck reaction and analyzed under light and laser scanning confocal microscopies. Micronuclei, nuclear projections (buds and broken eggs) and degenerative nuclear alterations (condensed chromatin, karyolysis and karyorrhexis) were scored. The frequencies of micronuclei, karyolysis and pycnosis were similar before and after exposure (P > 0.90), whereas the condensation of the chromatin and the karyorrhexis increased significantly after exposure (P < 0.0001). In contrast, both bud and broken egg frequencies were significantly higher before the examination (P < 0.005), suggesting that these structures are associated to the normal epithelium differentiation. The results suggest that the X-ray exposure during panoramic dental radiography induces a cytotoxic effect by increasing apoptosis. We also believe that the score of other nuclear alterations in addition to the micronucleus improves the sensitivity of genotoxic effects detection.

Introduction

X-ray is an important tool for diagnosis in medical and dentistry practice, in spite of being a potent inductor of genetic damage [1], [2], [3], [4]. Panoramic radiography of dental arcades is indicated by dentists when the evaluation of all teeth is necessary, since it is considered less harmful than several periapical radiographies. It is largely known, however, that there is no safety in radiation doses and that the biological effects of the exposures received would be accumulated thorough the time.

The micronucleus test performed in lymphocytes or in exfoliated cells is a very reliable assay to evaluate human genetic damage [5], [6]. This test has different applications, and is particularly useful for biomonitoring human populations under exposure to chemical and physical mutagenic agents [7], [8], [9], [10], [11], [12]. In ionizing radiation studies, this test has been used to assess genetic damages after occupational exposure to X-rays [12], [13], to measure cell radiosensitivity [14], [15], [16], to study the persistence of chromosomal aberrations in dividing cells [17] and to detect genotoxic effects of photon radiation [18]. According to Tolbert et al. [19], the specificity of the test to detect genotoxic and cytotoxic effects is increased by recording other degenerative nuclear alterations indicative of cell death, besides the micronucleus.

In the current study, the genotoxic effects promoted by X-ray emission during panoramic dental radiography were evaluated by using a differentiated protocol of the micronucleus test in exfoliated cells from oral mucosa [19], [20]. Besides micronucleus, nuclear alterations indicative of apoptosis (karyorrhexis, pycnosis and condensed chromatin) and necrosis (karyorrhexis, karyolysis, pycnosis and condensed chromatin), nuclear buds and broken eggs were also scored.

Section snippets

Subjects

Cells from oral mucosa were obtained from thirty-one healthy individuals (7 men and 24 women) submitted to a panoramic dental radiography examination as requested by the dentist. They answered a questionnaire before the X-ray examination. The main features computed were age, consumption of tobacco and alcohol, exposure to other genotoxic agents and regular oral antiseptic solutions. The panoramic dental radiographies were performed with a Siemens orthophos equipment, system 250—71 kV/15 mA/14 s/110

Sample characteristics

The mean age ± S.E. of the study subjects was 24 years ± 1.023. Two individuals indicated that they were cigarette smokers and they were considered light users, with a consumption of less than 15 cigarettes/day. Seventeen individuals drank alcohol, but in small doses and very low frequencies. Exposure to other known genotoxic agent was not reported by any of the study subjects. Twelve individuals used oral antiseptic solutions regularly, and one study subject had a dental prosthesis.

Cytological analysis

The total

Discussion

The epithelial cell kinetics is especially important in the interpretation of the results obtained with the micronucleus test. Chromosomal damage leading to micronucleus formation occurs in dividing cells from the basal layer of oral epithelium, but it is only observed later in exfoliated cells after the differentiation. The turnover of this epithelium is rapid (from 7 to 16 days), and thus the maximal rate of micronucleus is expected between 1 and 3 weeks subsequent to the exposure to a

Acknowledgements

We thank Dr. Patricia Gama for the critical reading of the manuscript. This work was supported by FAPESP, FAPESB, CAPES and CNPq. J.S. Passos is recipient of CNPq. student’s fellowship (PIBIC).

References (34)

Cited by (0)

View full text