Most people are aware of the risks associated with exposure to radiation. The most common place you are likely to receive exposure is at the dental office. Most of you are probably familiar with the protocol. The provider tells you that you are due for checkup x-rays and if you consent, you are then draped with a heavy lead apron and thyroid collar and the x-rays are taken. Most of my patients consent to the x-rays, some don’t. The concern is either financial or fear of exposure to radiation which are both valid reasons. Occasionally the patient is physically incapable of having them.

 The reality is that typical bitewing checkup x-rays are about the same amount of radiation you get in a normal day from the sun and other sources. A panoramic dental X-ray, which goes around your head, has about twice that amount of radiation.  On the other hand, the risks of undiagnosed problems could be dangerous, painful and even life threatening. Today, I would like to discuss the pros and cons of dental x-rays, the different kinds available and their uses. (1)

X-rays were discovered by Wilhelm Conrad Roentgen in 1895 while using a cathode ray tube. He noticed something in the room glowing while it was on, even when he placed a barrier between them. He soon started exposing film by beaming the x-rays through various objects including the human body.  The exposed films were named Roentgenograms or Roentgenographs in honor of his discovery. (2) Most people call the films x-rays, but this is somewhat inaccurate. The true term is radiograph.

X-rays themselves are a spectrum of light which is scientifically classified as electromagnetic radiation. They are short wave and high frequency. Without getting all technical, this allows them to pass through many solid objects.

Radiographs were quickly employed in the medical and dental fields and have been an invaluable diagnostic asset to this day. Amazingly, it took only two weeks after Roenten’s discovery for the first dental radiograph to be taken by Friedrich Otto Walkoff. Hair loss in the area of irradiation was immediately noted by him. The early field of x-ray pioneers is littered with horror stories of burns, swelling, hair loss, gangrene, cancer and death. (3) In 1897, the first legal settlement for radiation poisoning was awarded. In 1928 units of radiation exposure were settled upon making safety guidelines possible. The 1940’s to the 1960’s has been labeled as the golden age of radiation safety due to the numerous regulations for radiation safety. (4)

The advent of digital radiography has further reduced the level of exposure. There is a complex array of radiographic instruments today. Standard, panoramic and 3 dimensional radiographs are all common in the average dental office. Standard radiographs are smaller, capturing a few teeth per exposure. The three types typically taken are bitewings, periapical and occlusal less frequently all with different uses for diagnosis.

Bitewings are the most common and are used to visualize decay under fillings and between the teeth and to see the bone around the teeth. They are designed to see the upper and lower teeth at once. They aretaken on average yearly, or when a problem is suspected. When patients have low decay rates, they can be taken less frequently.

Periapicals are typically used to see the roots of the teeth. The name comes from “peri” = meaning around plus “apical” = meaning tip. They can also be used to see more of the jaw where no teeth exist. The circumstances vary as to the frequency that they are used, however, bitewings can’tbe taken in the anterior, so they are the only option to see those teeth.

Occlusal films are used for children mostly, but are useful in visualizing Nasopalatine Duct Cysts.

Panoramic radiographs are images of the entire set of upper and lower jaws and surrounding structures.

These are more like medical images, not meant to accurately diagnose decay and are taken less frequently. Their primary uses are visualizing wisdom teeth and their roots, locating cysts and tumors, visualizing the sinuses and other landmarks that may be helpful in diagnosing problems or placing implants. We can even see carotid artery calcifications and often refer patients to cardiologists. They are usually taken every 4 years.

Finally, we now use three dimensional radiographs for more precise diagnosis and planning surgeries such as the placement of implants. We usually refer to these images as “cone beams” which is short for Cone beam computed tomography or CBCT for short. They are critical for ideal implant placement or properly visualizing roots for root canal therapy.

Once a decision to obtain radiographs is made, it is the dentist's responsibility to follow the ALARA Principle (As Low as Reasonably Achievable) to minimize the patient's exposure to radiation. Examples of good radiologic practice include:

• use of the fastest image receptor compatible with the diagnostic task;

• collimation of the beam to the size of the receptor whenever feasible;

• proper film exposure and processing techniques; and

• use of leaded aprons and thyroid collars.

The standard for who needs radiographs, which kind, and how often is complex. Here is the table provided by the ADA and The US Department of Health and Human Services to show you the complexities of the situation. It will make your head spin and should give you some insight into the amount of critical thinking is involved in the average dentist’s day:

∗∗Factors increasing risk for caries may include but are not limited to:

1. High level of caries experience or demineralization

2. History of recurrent caries

3. High titers of cariogenic bacteria

4. Existing restoration(s) of poor quality

5. Poor oral hygiene

6. Inadequate fluoride exposure

7. Prolonged nursing (bottle or breast)

8. Frequent high sucrose content in diet

9. Poor family dental health

10. Developmental or acquired enamel defects

11. Developmental or acquired disability

12. Xerostomia

13. Genetic abnormality of teeth

14. Many multisurface restorations

15. Chemo/radiation therapy

16. Eating disorders

17. Drug/alcohol abuse

18. Irregular dental care (5)

*Clinical situations for which radiographs may be

 indicated include but are not limited to:

A. Positive Historical Findings

1. Previous periodontal or endodontic treatment

2. History of pain or trauma

3. Familial history of dental anomalies

4. Postoperative evaluation of healing

5. Remineralization monitoring

6. Presence of implants or evaluation for implant placement

B. Positive Clinical Signs/Symptoms

1. Clinical evidence of periodontal disease

2. Large or deep restorations

3. Deep carious lesions

4. Malposed or clinically impacted teeth

5. Swelling

6. Evidence of dental/facial trauma

7. Mobility of teeth

8. Sinus tract (“fistula”)

9. Clinically suspected sinus pathology

10. Growth abnormalities

11. Oral involvement in known or suspected systemic disease

12. Positive neurologic findings in the head and neck

13. Evidence of foreign objects

14. Pain and/or dysfunction of the temporomandibular joint

15. Facial asymmetry

16. Abutment teeth for fixed or removable partial prosthesis

17. Unexplained bleeding

18. Unexplained sensitivity of teeth

19. Unusual eruption, spacing or migration of teeth

20. Unusual tooth morphology, calcification or color

21. Unexplained absence of teeth

22. Clinical erosion

In short, unless a patient provides previous radiographs, some are usually indicated upon the first visit. If the patient has no history of decay, radiographs that look for decay are barely needed. On the other hand, if a patient continually develops decay and infections, more are needed. Every patient is unique and should be treated as such.

There is a problem however when a patient wants a diagnosis and treatment without proper radiographs. It is malpractice to do most procedures without proper diagnosis. Every diagnosis has proper treatment options. If there is no definitive diagnosis, there can be no definitive treatment to recommend. It is literally akin to working blind. It is equally bad to just diagnose from a radiograph without doing a visual clinical exam. Legally speaking, I am still responsible if something goes wrong. Even if I make a patient sign a form stating that they accept the risks of not taking radiographs, there is no legal precedent for them to consent to my negligence, which is exactly what can arise. It is illegal to do treatment on a patient without their consent, including taking x-rays. The prudent recommendation given by risk management experts is to dismiss the patient, something I seldom do. Typically, in time, the patient will come around and consent. Sometimes there are no issues detected and the patient says, “I told you so”. Sometimes I find grave problems and resist the urge to say the same.