Panoramic X-rays have long been regarded as a routine and safe procedure. The patient sits down, the machine rotates around the head, and within seconds, a complete image of the upper and lower jaws appears on the screen. However, a study published in the Archives of Orofacial Sciences has revealed something that has largely escaped attention: even at low doses, radiation from the procedure is sufficient to damage DNA and reduce the viability of oral mucosal cells, at least in the short term.
What Was Studied and Why Does It Matter?
The study was conducted by drg. Ryna Dwi Yanuaryska, Ph.D., together with a team from the Department of Dental Radiology, Faculty of Dentistry, Universitas Gadjah Mada. They sought to answer a seemingly simple question that had not previously been fully addressed: is a single panoramic X-ray exposure sufficient to damage cells lining the inside of the cheek, and if so, how quickly does the damage occur?
The study involved 20 healthy patients aged 18–25 years who underwent routine panoramic X-ray examinations at Prof. Soedomo Dental Hospital, UGM. None of the participants smoked, consumed alcohol, or had been exposed to radiation during the preceding two weeks. This was important because the researchers wanted to ensure that any detected changes were genuinely attributable to the X-ray exposure rather than other factors.
Buccal mucosal cells—the cells lining the inside of the cheek—were selected because they can be collected easily without an invasive procedure. A small brush is simply rubbed against the inside of the cheek to collect the cells. Samples were collected three times: before exposure, 30 minutes after exposure (Group 1), and 24 hours after exposure (Group 2).
What Did the Researchers See Under the Microscope?
Two methods were used to assess cellular damage. First, the trypan blue exclusion test was used to measure cell viability, or how many cells remained alive. The principle is straightforward: living cells have intact membranes that exclude the blue dye, whereas dead cells absorb the dye and appear blue under a microscope. Second, the comet assay, an electrophoresis-based technique, was used to visualize the “comet tails” formed by fragmented DNA. The longer the tail, the more severe the DNA damage.
The results were striking. Thirty minutes after a single panoramic X-ray exposure, cell viability decreased significantly. The percentage of DNA tailing in the comet assay increased to approximately 16%, while the visual DNA damage score increased by approximately 24% compared with the pre-exposure condition. In other words, within just half an hour after the X-ray examination, oral mucosal cells were already showing clear signs of cellular stress.
“Panoramic X-ray decreased cell viability and induced double-strand breaks within 30 minutes after exposure. Even though at low doses, panoramic X-rays induce cytotoxicity and genotoxicity in human buccal mucosa cells.”
The good news is that 24 hours later, the damage appeared to have begun to recover. The DNA tail percentage decreased to approximately 3%, and the visual damage score also declined, although this decrease was not statistically significant. Cell viability also showed no further decline compared with the condition 30 minutes after exposure.
The Body Has Defense Mechanisms—but They Are Not Unlimited
This partial recovery is not accidental. The human body possesses active DNA repair pathways that operate following radiation exposure. Two major pathways are non-homologous end joining (NHEJ) and homologous recombination (HR). X-ray radiation, such as that used in panoramic radiography, is generally repaired through the NHEJ pathway, which operates relatively rapidly. The body’s adaptive response to low-dose radiation—including protection against reactive oxygen species and elimination of severely damaged cells—also contributes to this recovery.
However, the researchers emphasize that recovery within 24 hours does not mean repeated exposure should be ignored. They stress that radiation protection for patients undergoing panoramic X-rays must remain a priority—not because a single exposure is necessarily harmful, but because every dose of radiation, however small, has the potential to produce biological changes.
Why Does This Study Open a New Path?
Before this study, most similar research relied on micronucleus assays or observations of nuclear changes such as karyorrhexis and pyknosis. The use of the trypan blue exclusion test to assess buccal mucosal cell viability following panoramic X-ray exposure had not previously been reported. The combination of the two methods—cell viability testing and comet assay—provides a more comprehensive picture: not only whether DNA has been damaged, but also whether the cells remain alive and functional.
The study also raises several unanswered questions: Which molecules are involved in the damage and repair processes? How much does the response vary between individuals? What happens if exposure occurs repeatedly over short intervals?
The answers may not yet be available. But at least we now know that panoramic X-rays, which may seem trivial because the procedure lasts only a few seconds, leave behind a measurable biological footprint. And the body, with all its remarkable complexity, works hard to repair that footprint.
Source DOI: http://10.21315/aos2021.16.s1.8
Authors: Anny Anggraini; drg. Achmad Zam Zam Aghasy, M.Kes.
Photo: Freepik