By Alia Hakakian
There are many genotoxic effects associated with dentistry, both for the dentist and their patients. Fully understanding the risks associated with dentistry allows us to better prepare and find a way to continue dentistry in the safest way possible. Although the risks may seem daunting, understanding them allows us to better deal with them.
One source of risk in this field is with the X-rays that dentists routinely perform. These images show the interior of one’s teeth and gums, allowing the dentist to evaluate one’s oral health. A dental X-ray can show things like cavities, impacted teeth, and tooth decay. DNA and DNA crosslinks can be damaged by the Ionizing Radiation that X-rays use. Additionally, X-rays have been found to cause genotoxic damage, such as single and double DNA strand breaks, cell death, and micronuclei. One study tested the exfoliated oral cells of 29 adults before and 10 days after exposure to partial and total cone-beam CT radiographs. This type of radiograph diverges the X-rays into a cone shape, and is often used in the diagnosis of dental diseases and planning of different treatments. The study found a statistically significant difference in the number of micronucleated cells before and after the CBCT treatment, both for partial and total. Additionally, there was also a statistically significant difference in the frequency of other nuclear alterations both for partial and total CBCT. These nuclear alterations include chromatin condensation, nuclear dissolution, nuclear fragmentation, buds, and broken eggs. This study shows that exposure to dental radiographs leads to several different types of genotoxic damage.
This is not the only study that has found adverse genotoxic effects of dental X-rays. Another study was done in order to determine the genotoxic effects of X-rays on children after dental radiographs. The exfoliated buccal mucosa cells of 40 children were taken and studied immediately before and around 10 days after exposure to dental radiographs. Half of the group was exposed to bitewing radiographs, which are used to determine if there is tooth decay in the back teeth or cavities in between teeth, where they are not visible. The other half was exposed to digital dental panoramic radiographs. Their cells were then studied using the buccal micronucleus cytome assay, which is a minimally invasive way to study DNA damage, chromosomal instability, cell death, and the potential for buccal mucosa tissue to regenerate. The study found that there was an increase in the number of micronuclei in the cells collected after exposure to both radiographs. Furthermore, the frequency of micronuclei was higher after exposure to bitewing, than after exposure to digital dental panoramic radiographs. Both of these radiographs caused genotoxic damage to the buccal mucosa cells of these children after a single exposure. These findings of genotoxic damage due to panoramic radiographs are supported by another study, which found that panoramic dental radiographs increase the frequency of chromosomal damage and nuclear alterations in epithelial gingival cells.
Both of these studies have shown genotoxic effects in the cells of individuals after one exposure to different types of dental radiographs. This is concerning not only for the patients who are exposed to these X-rays, but also for the dentists who are performing them. While patients undergo these X-rays about twice a year, dentists are administering them multiple times a day, and are therefore exposed to much more radiation. Dentists must take steps to protect themselves from too much exposure to X-ray radiation. One way to limit the exposure to radiation is for both the dentists administering the X-ray and the patient receiving it to wear lead aprons. These aprons shield the body from unnecessary radiation exposure. It is also beneficial for the dentist administering the X-ray to leave the room after setting up the camera, before the X-ray actually begins. This way they are not in the room, being exposed to the radiation while it is at its peak.
Many dental materials have also shown significant genotoxic risk. One such material is the resin monomers of acrylic Andresen activator. An Andresen activator is an orthodontic appliance used to correct malocclusion, meaning it corrects the bite of jaws that don’t close down correctly. An in vivo experiment was conducted in which 26 test subjects were treated with Andresen activators and compared to 16 test subjects who had never undergone orthodontic work. This is important because it ensures that the test subjects had not been previously exposed to the resin monomers of this appliance. Buccal mucosa cells were collected before the exposure and 7, 15, 30, 60, and 90 days after it. The cells were analyzed using the micronucleus assay as well as the comet assay. These tests saw a difference between the control and test group in tail moment, tail intensity, micronuclei, binuclear cells, and bud cells. There was no difference found in the cellular viability and tail length. These results show that exposure to the resin monomers of the Andresen activator does not necessarily cause cytotoxic effects, but definitely does cause genotoxic effects.
Another dental material that has been shown to cause genotoxic damage is the materials used in restorative dental fillings. Both the amalgams and the methacrylates resin-based materials have been found to be released into the buccal cavity and be systematically spread. The comet assay, micronucleus test, and monitoring of cell death markers were used to study the oral mucosa cells of 63 subjects. It was found that lifestyle variables such as smoking and alcohol intake did not affect the genotoxic response and are therefore not counted as confounding factors, since they did not influence the results. The results showed unequivocal evidence that exposure to dental fillings made of both of these materials causes genotoxic damage. These findings are very important because after a patient receives a filling with these materials, they are constantly being exposed to the filling’s materials for a long period of time and this can cause severe genotoxic effects.
When receiving fillings, it is important to make sure that one has the potential genotoxic risks in mind, in addition to solving the problem of a cavity or tooth decay. According to the FDA, the use of amalgams is declining, while silorane resin composites and glass ionomers or porcelain fillings are being used more. These composite fillings are more aesthetic than amalgam fillings, as their color matches the natural color of the tooth, instead of a silver color that is highly visible. These materials do not have the same level of genotoxic risk that amalgam fillings have, and are therefore safer to use. However, many people still opt to have amalgam fillings, as they are stronger and last longer than fillings made from other materials. At this time, the FDA has not put a ban on the use of amalgam fillings, but has advised that certain high-risk groups avoid using them.
These findings should not scare us and stop us from going to the dentist. The fact that we know this information allows us to be better informed and prepared to perform the necessary procedures in the safest way possible.