Xrays: Are they good or are they bad?

Gamma Radiation

First it is necessary to understand that to obtain X-ray films it is necessary to irradiate the body with gamma radiation that has sufficient energy to pass through human tissues to record an image on a film or electronic sensor.

The pros and cons….

Gamma radiation, also known as ionising radiation, is both useful for imaging but potentially harmful to the tissues. The decision to take an X-ray is therefore dependent on the potential diagnostic information that can be obtained from the X-ray image versus the potential risk. In the vast majority of situations, the benefit far outweighs the risk because the amount of ionising radiation used is so small that it has very little chance of causing any damage to the body.

Harmful effects of radiation….

Repeated exposure to high dose gamma radiation will cause tissue injury, the most minor of which is redness and discomfort as you see in sunburn.  However, this is not likely with X-ray exposures in view of the extremely low dose of radiation used. It is precisely because the dose is so low that X-rays are very safe.

High dose radiation damage….

Repeated unnecessary exposure to gamma radiation in higher doses has been demonstrated to cause abnormal changes in the cells in the tissues that can lead to the development of cancer at the site. However, the doses that must be used to achieve this effect are many times greater than the doses used for diagnostic X-ray imaging.

Radiation to treat cancer….

High dose of radiation can also be harnessed to our benefit in the treatment of cancer. Radiotherapy is used to kill cancer cells and cause tumors to shrink. This demonstrates how well we now understand the effects of gamma radiation and how we have learned to use it to our benefit.

The decision to take an X-ray…

It is however important to ensure that X-rays are only taken when they will help in determining the nature of a patient’s problem. X-rays should only be taken when the information required for correct diagnosis is not available from any other investigation.

ALARA – as low as reasonably achievable

The dose of radiation a patient receives over their lifetime should be as low as reasonably achievable. This is the basis of good safety and professional care of patients with respect to the use of radiation.

Patient concerns….

Some patients are concerned about how much radiation they receive when X-ray examinations are conducted. They should be reassured to know that the dose is very little more than a few days of normal background radiation (solar radiation) one receives simply by living on this planet. We are all exposed to a background level of radiation but the level of that exposure is extremely low and allows us to live safely.

X-ray radiation doses….

For example a chest X-ray exposes a patient to the same level of radiation as they would receive in 2.4 days simply living on due to the background radiation produced by our sun. This would equate to 0.02 millisieverts. Similarly the small X-rays taken inside the mouth will result in very little additional radiation exposure. For comparison, a skull X-ray would use a dose of 0.07mSv, which equates to 8.5 days of natural solar radiation.

There are more complex X-ray investigations that will result in far higher exposures to gamma radiation. However, the potential benefit for the diagnosis of serious illness or disease is such that the benefit outweighs the risk.

For example A medical multi-slice computerised tomography scan (MSCT scan) of the head would typically provide a dose of 2.0 milliSieverts (mSv).  This would be equivalent to around 243 days of natural background solar radiation. Generally it is accepted that background solar radiation equates to 3mSv per year.

The doses estimated are those reported in the European Commission, Radiation Protection Report 118 from the year 2000.

Dental benefits of X-rays….

In dentistry we rely on X-rays for thorough examination of teeth and jaws. A visual examination by eye alone fails to identify many early lesions of dental decay between teeth. In addition it is not possible to identify loss of bone in the early stages around teeth due to localised gum disease problems unless specific gum probing is performed. Early stages of dental infective and inflammatory lesions on the end of roots of teeth are also impossible to identify in any other way than by X-ray examination.

The small X-ray films, and the extremely low dose of radiation required to obtain a clear image are associated with such a small risk that they are considered extremely safe and an acceptable risk to achieve good diagnosis and high quality dental care.

Your dentist is trained….

Your dentist is trained in dental radiology during the dental degree course and they understand the need to only take X-rays when they will contribute to good diagnosis. X-rays are not taken as a routine “screening” type of examination. However, in certain instances it is common to obtain an X-ray as part of the assessment procedure. An example of this would be the taking of an Orthopantomogram (OPT). This is a 2-dimensional scan image of the jaws and teeth. It shows the location and angulation of all the teeth and their relative position to various other structures including the maxillary sinuses and the inferior alveolar nerve (IAN), artery and vein. These are structures that must be avoided when certain teeth are removed.

The clinical relevance

Third molars, also known as wisdom teeth, often have roots that can lie against the floor of the maxillary sinus and the lower wisdom teeth may have roots close to the inferior alveolar nerve. In the latter circumstances it is important to have a 3-dimensional interpretation of the relative position of the nerve to ensure that the technique used to remove the tooth does not cause the root to apply pressure to that nerve.

3-dimentional imaging is now possible using equipment known as a Cone Beam Volumetric Tomogram (CBVT). This is equipment that can be used to image a relatively small area of the jaws using a much lower dose of radiation than would be used for a medical Multi-slice Computerised Tomography scan (MSCT scan).

Many practitioners who perform oral surgery or implant surgery will have their own CBVT scanner in the practice to allow them to obtain extremely accurate imaging of a specific area of the jaw and minimise the dose of gamma radiation used. The digitised data is then often loaded into customised surgical software to allow detailed surgical planning to be undertaken. This is very useful when trying to decide on the most appropriate size of dental implant to use to replace a missing tooth.

When planning to place an implant in a jaw, it is useful to be able to do so “virtually” on the computer screen. This then allows the dental surgeon to assess if there is sufficient bone available to support the implant.  If not, it allows the surgeon to assess how much extra bone is required in order to achieve adequate bone around the implant once in place. This can be demonstrated to the patient on the computer screen and help greatly in explaining the surgery to be undertaken. Many patients like to understand what is to be done and why they need additional bone.

In summary….

While there are risks to people if they are inappropriately irradiated with gamma radiation, the use of standardised, safe and in-date certified radiography equipment by a trained operator achieves greatly improved diagnosis with minimal risk. This is the message that should be understood by all patients. They have no need to worry if normal protocols are followed and a sensible approach is taken in the use of medical and dental radiography.

Contact the friendly team at NQ Surgical Dentistry today on (07) 4725 1656 or call in to see us at 183 Kings Rd, Pimlico QLD 4812