Influence of X-rays on living tissue - Radiography
Influence of X-rays on living tissue
X-ray radiation is ionizing radiation; that is, molecules can be converted to ions. This can have harmful consequences for the human body. For example, in a living cell exposed to radiation, proteins can be broken into pieces. This can lead to the loss of the function of that cell, to cell death or to cell changes. Usually the effect is not demonstrable. A clear biological effect does occur if a body is exposed to a large amount of radiation in a short time. In very serious cases, someone dies within two days.
Small amounts of radiation are used in dentistry. However, years of exposure can have consequences for health. It is very difficult to determine exactly how large the risks are. It is believed that prolonged exposure to small doses of radiation can lead to a biological effect, distinguishing between somatic and genetic effects.
We call the effect of X-rays on a body a somatic effect. Irradiation of the same piece of tissue can lead to its death in the long run. A dentist who always holds the photo in the patient's mouth can develop a radiation ulcer on his finger. The somatic effect is also used positively in medicine. The destruction of cell material by radiation is a therapy used in the treatment of some forms of cancer.
Simple, under-developed cells are more sensitive to radiation than specialized tissue. A growing embryo has a lot of non-specialized cell material, especially in the first three months. A relatively small amount of radiation can therefore be harmful and cause abnormalities in the embryo. Photos should therefore be avoided during pregnancy, especially in the first three months.
After irradiation, a cell may die or changes may occur such that the cell divides rapidly and a tumor forms. In particular, leukemia (blood cancer) and skin cancer may develop after an overdose of X-rays.
Radiation can cause changes in genetic material. This means that the next generation has different qualities than what can be expected on the basis of the characteristics of both parents. This is called mutation. Irradiation of the gonads (reproductive organs) gives a genetic effect.
The amount of radiation to which tissue is exposed is called the dose. The unit in which the dose is expressed is the x-ray (r). The absorbed dose is that part of the total dose that is absorbed by the body or part thereof. This amount is expressed in gray or rad (1 Gy = 100 rad).
The doses used in dentistry are low. Nevertheless, it is important to keep the absorbed amount of radiation as low as possible. This applies to the patient and to all members of the dental team. The dental user has the legal obligation to supervise this.
The dental staff is never in the primary beam transmitted directly by the X-ray machine. But the primary bundle always gives secondary or scattered radiation after an object has been irradiated. This is reflected or diffracted X-rays via the patient, the chair, the film or the adjustment bracket. With an X-ray badge the amount of radiation received during a certain period of time can be determined afterwards. This is a dosimeter. This is pinned to the clothing and is worn every day. After three months, the badge is sent to a special institute (eg TNO), where it is determined how large the absorbed dose has been during the past period. Because it is about personal radiation control, every badge must always be worn by one and the same person.