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Dental Radiography

Jan. 1, 2011
Zap! From being sandbagged for 25 minutes in 1896 for an X-ray, to taking a mere tenth of a second for today's filmless images ...

Technology, infection control, and exposure guidelines

by Ellen Standley, RDH, BS, MA, and Heidi Emmerling, RDH, PhD

Zap! From being sandbagged for 25 minutes in 1896 for an X-ray, to taking a mere tenth of a second for today's filmless images, the dental profession has seen a lot of changes in technology, safety procedures, and regulations. This article will discuss film and filmless (digital) images, safe practices for infection control, and current exposure guidelines.

Roentgen, rems, and rads – these are exposures and absorbed doses. We know the name Roentgen because of his 1895 discovery of X-radiation and his subsequent Nobel Prize in 1901. His wife should have been recognized also since he used her hand for the first documented radiograph on a human body – a 15-minute exposure.

Shortly after Roentgen's discovery, other pioneers were involved in the development of radiology. Dr. Otto Walkhoff, another German scientist, is credited with the exposure of the first dental radiograph, which lasted 25 minutes, and it was in his own mouth. Obviously little was known at the time about the biologic effects of exposure. In fact, C. Edmond Kells, a New Orleans dentist, was recognized with some of the first practical dental applications. But he ultimately lost his fingers, hand, and arm due to numerous exposures over the years. Unfortunately, he eventually died from the effects of excess radiation.

William Herbert Rollins, a dentist and a physician, also suffered radiation burns to his hand while developing the first dental X-ray unit. Because of this, he became interested in radiation protection and published the first paper discussing the risks. It took years for his warnings to be heeded by the dental profession in the form of safety regulations for occupational and consumer protection.

Imaging technology

Digital radiography produces filmless images. It was introduced to the dental profession in 1987, and in a little over 20 years has become widely accepted. According to Mel Kantor and Alex Ruprecht, French dentist Francis Mouyen introduced digital imaging to the dental profession. Ruprecht reports, "It has grown into a widely used modality and, parallel to imaging in medicine, has evolved into digital radiography using electronic sensors such as charge-couple devices (CCD) or complementary metal-oxide semiconductors (CMOS), as well as computed radiography using photostimulable storage phosphor plates (PSP) and laser scanners. In both cases, the image is created with the use of a computer and viewed on a monitor."

These sensors are available in different sizes. One thing to remember is that, although the CCD sensor is bulkier than traditional film, it has a slightly smaller surface image. This means there are a few millimeters less per image than the sensor size itself. Some practitioners have found that a common problem with the sensor is missing the mesials of the first bicuspids in periapicals and bitewings. This is due in part to the size and rigidity of the sensor.

Individual software provides variations in viewing the images. The images can be viewed side by side, magnified, manipulated to improve density or contrast, reversing gray scale, embossing, colorization, and more. Some practitioners like these bells and whistles. Because of the advantage of instant imaging, the ability to enhance diagnosis, and the benefit of patient education, digital systems have gained popularity.

Other benefits of digital radiography include the elimination of film, no traditional processing with chemicals, and no more working with certain hazardous wastes. Additionally, the radiation exposure to the patient is significantly less with digital radiography. But practitioners must remember that this is not a free pass for numerous retakes. In her presentation, Evelyn Thomson discussed this trend and expressed concern over the casual attitude regarding digital radiography and retakes.

Digital radiography allows instant and easy transmission of images and electronic storage. Mel Kantor presents an interesting historical side note: "The transmission of radiographic images, called teleradiography, allows practitioners to submit insurance claims electronically, forward patients' radiographs to a dentist across the country, or obtain specialty consultations from experts wherever they may be. But even this is nothing new. Consider this excerpt from a 1929 paper: 'Through the courtesy of Western Union Telegraph Company, we publish two dental radiographs transmitted by telegraph and photographs of the simple-appearing but most ingenious machines that make this modern wonder possible. Even the filled root canals show up well. This service is available commercially if you should want to consult with a distant dentist.' Teleradiography is an 80-year-old idea."

This brings us to some disadvantages of digital radiography. Sometimes computers and software systems are subject to technological malfunctions and operator error. This can result in the loss of images and records. Furthermore, not all practitioners use the same software; therefore, the ease of record transmission can result in frustration and time lost. Also, some digital sensors are bulkier and less comfortable than traditional film. Some authors mention legal concerns with software image manipulation. This is becoming less of a problem now than before. Another disadvantage is the start-up cost. Individual sensors can range from $6,000 to $8,000 each. Add the cost of monitors and software and things can really add up.

A final concern is infection control. Digital sensors cannot be heat sterilized, and continually changing plastic barriers has been known to tear and expose the sensor to the oral cavity. The keyboard and mouse must also be protected. See Table 1 for advantages and disadvantages of digital radiography.

Infection control

Because there are no critical instruments associated with radiology, practitioners assume a more cavalier attitude toward infection control. However, there are many opportunities for cross contamination in both digital and film-based radiography for semicritical and noncritical items.

First of all, it should be understood that the standard protocols such as hand hygiene, gloves, attire, barriers, and personal protective equipment must be observed. Extraoral devices are considered noncritical, meaning they do not come in contact with the mucous membranes but still require observation of aseptic technique. Examples include the lead apron, cone, tube head (PID), exposure button, control panel, computer keyboard/mouse, at-risk countertops, or other surfaces that have potential for risk of cross contamination.

According to the ADA Council on Scientific Affairs, "All extraoral devices that will be contacted during the procedure should be either disinfected between patients or protected by a barrier and changed between patients. An EPA-registered hospital-level disinfectant with low-to-intermediate activity should be used to treat any surfaces that become contaminated."

Film and processing protocols deserve discussion since they are prime areas for cross contamination. Joen Iannucci and Laura Howerton suggest the following steps for film handling:

– Film handling during processing with barrier envelopes

  • Place disposable towel on work surface in darkroom/processor
  • Place container with contaminated films next to towel
  • Put on gloves
  • Take one contaminated film out of container
  • Tear open barrier envelope
  • Allow film to drop on paper towel
  • Do not touch film with gloved hands
  • Dispose of barrier envelope
  • After all barrier envelopes have been opened, dispose of container
  • Remove gloves and wash hands (film packets are still unopened; only the barriers have been removed)
  • Unwrap and process films (in daylight loader or darkroom)

– Label a film mount, paper cup, or envelope and use to collect processed films without barrier envelopes

  • Place disposable towel on work surface in darkroom/processor
  • Place container with contaminated films next to towel
  • Put on gloves
  • Turn out darkroom lights if in darkroom
  • Take one contaminated film out of container
  • Open film packet and slide out lead foil backing and black paper; discard film packet wrapping
  • Rotate foil away from black paper and discard
  • Without touching film, open the black paper wrapping
  • Allow film to drop on paper towel
  • Do not touch film with contaminated gloved hands
  • Discard black paper wrapping
  • After all packets have been opened, remove gloves carefully and place gloves in contaminated holder
  • Wash hands
  • Process films
  • Label a film mount, paper cup, or envelope and use to collect processed films

– We suggest an alternative method for daylight loaders and films with plastic (nonpaper) outer covering

  • Soak films in an EPA moderate-level chemical germicide for the recommended time
  • Put on clean gloves
  • Rinse film packets with water
  • Place on barriered surface and dry with paper towels
  • Remove gloves, wash hands, don new gloves
  • Process films
  • Label a film mount, paper cup, or envelope and use to collect processed films

Exposure guidelines

Gone are the days of cookie-cutter bitewings every six months and full mouth series every five years for all patients. FDA and ADA recommend use of exposure guidelines that take into account patient dental and medical history; even clinical exams are part of these guidelines. This means that each patient is individually assessed for the need for radiographs.

For example, bitewings for recalls at six- to 12-month intervals are not recommended on a routine basis unless they are accompanied by the appropriate risk factors delineated in the guidelines. Such risk factors include a patient with recent caries experience, numerous restorations, and poor oral hygiene.

According to the FDA, the guidelines entitled "The Selection of Patients for X-ray Examination" were developed in 1987 by a panel of dental experts convened by the Center for Devices and Radiological Health of the U.S. Food and Drug Administration (FDA). These guidelines stemmed from a concern about the public's exposure to radiation. From this the guidelines specific for dental X-rays were developed, and these were in place for 15 years. Revisions in 2002/2004 took into account advancing technology. Some of the updates include:

  • An additional "other circumstances" category, including implants and remineralization of enamel
  • Restorative, endodontic needs, and other pathology
  • Inclusion of edentulous patients
  • Use of panoramics
  • Clarification that bitewings can be either horizontal or vertical

The guidelines categorize 1) new and recall patients, 2) age and dental development stage from children with primary through adults with edentulous dentition, and 3) risk category based on presence or absence of certain conditions. These guidelines must be used in conjunction with a complete medical/dental history and clinical exam.

Some examples of applying these guidelines include:

1. An adult recall patient with no caries risk and no clinical caries during the exam should have bitewings every 24 to 36 months.

2. A child with the same situation is recommended for bitewings every 12 to 24 months if the proximal surfaces cannot be visually examined.

(Note that these examples are low risk, no clinical caries categories.)

3. An adult recall patient with caries or increased risk for caries should have bitewings every six to 18 months.

4. A child in the same situation is recommended for bitewings every six to 12 months if proximal surfaces cannot be visually examined.

Ultimately, the guidelines defer to the clinician's judgment and an individual evaluation of each case. In some instances, an individual case and accompanying clinical judgment will merit six-month intervals on bitewings, while others will only need bitewings every 12, 18, 24, or 36 months. Guidelines are available at the FDA's Web site at


Every dental professional should be aware of the "As Low as Reasonably Achievable" (ALARA) Principle, in which consumer diagnostic radiation exposure is minimized. There are many methods to accomplish this. Examples of good radiologic practice include:

  • Use of digital radiography (exposure times are reduced by 50% to 80% from conventional high-speed film)
  • Patient selection criteria, including health history and oral exam prior to taking radiographs
  • Collimation of the beam to the size of the receptor whenever feasible
  • Proper film exposure and processing techniques to avoid retakes
  • Use of leaded aprons and thyroid collars with both film and filmless images
  • Other techniques and safety protocols that protect patients from unnecessary secondary radiation.

A further note on leaded aprons and thyroid collars

According to the FDA, "The amount of scattered radiation striking the patient's abdomen during a properly conducted radiographic examination is negligible. However, there is some evidence that radiation exposure to the thyroid during pregnancy is associated with low birth weight. Protective thyroid collars substantially reduce radiation exposure to the thyroid during dental radiographic procedures. Because every precaution should be taken to minimize radiation exposure, protective thyroid collars and aprons should be used whenever possible. This practice is strongly recommended for children, women of child bearing age, and pregnant women."

Unlike the early days of primitive equipment with minimal safeguards and long exposures, today's radiographs afford the patient the least possible exposure with the best diagnostic information. From the times of Roentgen, Kells, and Rollins, the contrast with today's technology and safe practices is remarkable.

Ellen Standley, RDH, BS, MA, is president of CDHA and a long-time active member of ADHA, CDHA, and the Sacramento Valley Dental Hygienists' Association. She is a professor of Dental Hygiene at Sacramento City College and holds memberships in the California Dental Hygiene Educators' Association and the American Academy of Dental Hygiene. Ms. Standley can be reached at [email protected].

Heidi Emmerling, RDH, PhD, is interim director and assistant professor of dental hygiene at Sacramento City College and a CODA site consultant. She is owner of Writing Cures, a writing and editing service, and co-author, of The Purple Guide: Paper Persona, a guide to preparing professional development and job search materials. Dr. Emmerling can be reached at [email protected].


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