Radio 104
Responsibilities of the Dentist
- To prescribe radiographs only for diagnostic purposes.
- To ensure that all radiographic equipment is properly installed and maintained in a safe working condition.
- To provide appropriate shielding to protect staff and patients from the effects of radiation.
- To require that anyone exposing radiographs be properly trained and appropriately supervised while exposing radiographs.
- To obey all state radiographic licensing requirements, rules, and regulations.
- To participate in obtaining informed consent.
It is important to stay current with the latest recommendations regarding radiation exposure in the dental workplace, protective methods, and new equipment developed to decrease exposure.
Dental assistants need to be prepared to explain to the patient the importance of a diagnostic radiograph and should not hesitate to ask the dentist to reinforce the value of a radiograph for diagnostic purposes.
Equipment for Radiation Protection
- The dental tubehead must be equipped with certain appropriate components:
- Aluminium filters
- Lead collimators
- PIDs
- Equipment should be checked on a regular basis by state or federal regulating agencies.
- Faulty or malfunctioning equipment should be repaired immediately.
If a patient expresses concerns about safety, the dental assistant can mention how the design and maintenance of dental radiography equipment are created with radiation protection in mind.
Radiographic equipment should be regularly assessed and, if need be, repaired as soon as possible to ensure optimal safety for the patient and the dental team.
Aluminum Filter
- The purpose of the aluminum filter is to remove the low-energy, long-wavelength, and least penetrating x-rays from the x-ray beam.
- These x-rays are harmful to the patient and are not useful in producing a diagnostic-quality radiograph.
- X-ray machines operating at 70 kVp or higher must have aluminum filtration of 2.5 mm. This is a federal requirement.
Collimator
- The collimator is used to restrict the size and shape of the x-ray beam as a means of reducing patient exposure.
- A collimator may have either a round or rectangular opening.
- A rectangular collimator restricts the beam to an area slightly larger than a size 2 intraoral film and significantly reduces patient exposure.
Where is the collimator located? (Between the x-ray tube and the PID.)
The PID
- The PID appears as an extension of the x-ray tubehead.
- It is used to direct the x-ray beam. Round and rectangular PIDs are available in two lengths:
- Short (8-inch)
- Long (16-inch)
For infection-control purposes, the PID, along with the tubehead, should be covered in plastic barriers and changed for each patient.
The end of the PID should be positioned close to the extraoral portion of the film holder and lined up correctly in all three planes to ensure accurate exposure and image production on the film.
Patient Protection
- Lead apron and thyroid collar:
- A lead apron and thyroid collar must be used on all patients for all exposures.
- This rule applies to all patients, regardless
of the patient’s age or sex or the number of films being exposed.
- The lead apron should cover the patient from the neck to the lap to protect the reproductive and blood-forming tissues from scatter radiation.
- Many states mandate the use of a lead apron.
Dental assistants should ensure that the lead apron and thyroid collar are stored properly and not folded, because creases may crack the lead.
Newer, more lightweight and flexible versions of the apron are replacing the older, heavier versions.
Care should be taken not to touch the apron with the same gloves that were used to place the film in the patient’s mouth, which will cause cross-contamination, compromising infection control.
The lead apron and thyroid collar must be large enough to cover the seated patient from the neck to above the knees.
The operator is placing the lead apron over the patient’s upper body and putting a lead thyroid collar around the neck.
The operator should ensure that the patient removes any oral piercings, removable dental prostheses, or eyeglasses that may distort or interfere with the desired image.
Fast-Speed Film
- The size of silver bromide crystals is the main factor in determining the film speed: the larger the crystals, the faster the film.
- A fast film requires less exposure to produce a quality radiograph.
- Fast-speed film is the single most effective method of reducing a patient’s exposure to
x-radiation. - Fast-speed film is available for both intraoral and extraoral radiography.
With the advent of digital radiography, reusable sensors placed in the patient’s mouth instead of film are attached to a computer software program which captures the image and displays it almost immediately on the computer screen. Digital radiography allows for an even more substantial decrease in patient exposure.
Film-Holding Devices
- The use of a film-holding instrument keeps the patient’s hands and fingers from being exposed
to x-radiation. - The film holder also keeps the film in a stable position and helps the operator proper position the film and the PID.
Having edentulous or partially edentulous patients insert their denture or partial denture when taking periapical radiographs on the opposing arch will better stabilize the film holder.
What may be placed in areas of missing teeth to help stabilize the film-holding instrument? (Cotton rolls.)
The patient’s fingers are unnecessarily exposed to radiation when film holders are not used.
When possible, a device should be used that aligns the intraoral film with the extraoral source, allowing precise capture of the desired structure and avoiding “cone cuts.” This also avoids distortion of the image captured by the film when the PID is placed at the wrong angle to the film and anatomic structure.
During times when it may be difficult to use this device (e.g., patient has on a rubber dam while undergoing root canal therapy), the film may be held with surgical forceps, keeping the patient’s hand at a reasonable distance from the x-ray source.
Exposure Factors
- Using the proper exposure factors also limits the amount of x-radiation the patient is exposed to.
- Adjusting the kilovoltage peak, milliamperage, and time settings controls the exposure factors.
- A setting of 70 to 90 kVp keeps patient exposure to a minimum.
- On some dental units, the kilovoltage peak and milliamperage settings are preset by the manufacturer and cannot be adjusted.
What is the most likely factor to require adjustment? (Exposure time.)
What determines the exposure time? (The speed of the film [very different for digital radiography], the size of the patient, and the denseness of the patient’s anatomic structures.)
Proper Technique
- Proper technique is necessary to ensure the diagnostic quality of films and reduce the amount of radiation to which the patient is exposed.
- Films that are nondiagnostic must be retaken; this results in additional radiation exposure to the patient.
- Retakes are a major cause of unnecessary radiation exposure in patients and must be avoided.
Having to retake radiographs wastes time and is not relished by most patients.
Although some retakes are unavoidable, most are preventable.
If a retake is ordered, the dental assistant should know how to correct the error that resulted in the need for a retake.
X-Rays During Pregnancy
- The Guidelines for Prescribing Dental Radiographs, issued by the American Dental Association in conjunction with the Food and Drug Administration, state that dental radiographic procedures “do not need to be altered because of pregnancy.”
- When a lead apron is used during dental radiographic procedures, the amount of radiation received in the pelvic region is nearly zero.
- There is no detectable exposure to the embryo or fetus with the use of a lead apron.
When a radiograph is taken during pregnancy, the benefits of a proper dental diagnosis should outweigh the minimal risk of exposure from having a radiograph taken.
An undiagnosed or improperly treated dental infection in a pregnant patient poses a far greater risk to the fetus than does the minimal exposure resulting from a dental radiograph.
Operator Protection
- A dental assistant who fails to follow the rules of radiation protection may suffer the results of chronic radiation exposure.
- By following these rules, dental personnel can keep their radiation exposure to zero.
Dental assistants must accept responsibility for their own radiation safety.
Rules For Operator Protection
- Never stand in the direct line of the primary beam.
- Always stand behind a lead barrier, if one is available, or the proper thickness of drywall.
- If a lead barrier is not available, stand at right angles to the beam.
- Never stand closer than 6 feet to the x-ray unit during an exposure unless you are behind a barrier.
Dental assistants working in an unfamiliar office or treatment room should familiarize themselves with the proper position to stand in while taking radiographs.
Review where the exposure button is in addition to the control panel. These may be located in separate places.
For the sake of safety, the dental assistant must stand out of the path of the primary beam.
Because dental facilities have different layouts for capturing dental radiographs, a different position may have to be taken to avoid exposure, depending on the facility.
There may be a lead wall to stand behind, or the assistant may need to walk around the corner with a portable exposure button.
There may also be an exposure button positioned on a wall outside the room used for radiographs.
When it is time to expose a film, the operator must ensure that visitors and other dental personnel are safely positioned.
Personnel Monitoring
- Three types of monitoring devices are used to determine the amount of radiation exposure to personnel:
- Film badge
- Pocket dosimeter (pen style)
- Thermoluminescent, or TLD
These monitoring devices are small and light enough to be placed on the breast pocket of a lab jacket without interfering with the dental assistant’s normal duties.
Fig. 38-26 A film badge is used to monitor the amount of radiation that reaches the dental radiographer.
(Courtesy of Global Dosimetry Solutions, Irvine, Calif.)
Monitoring devices are usually sent to the agency monthly, and a new one is returned to the operator along with a report to the dentist showing radiation exposure results for the individual.
Equipment Monitoring
- Dental x-ray machines must be monitored for radiation leakage.
- If a dental x-ray tubehead has a faulty tubehead seal, leakage results.
- Dental x-ray equipment can be monitored through the use of a film device that can be obtained from the manufacturer or from the
state health department.
If the Patient Cannot Cooperate
If the patient is a child who is unable to cooperate, he or she is seated on the parent’s lap in the dental chair. Both the parent and child are covered with the lead apron, and the parent holds the film in place.
Sometimes having a child sit on the parent’s lap helps with cooperation, and the child may keep the film holder in his or her mouth without the parent’s assistance.
What simple analogies can be used to help gain the cooperation of young patients? (“Bite on the cookie” or “Can you stay still and smile for the camera while we take a picture?”)
What film size is appropriate for a pediatric patient? (Size 0 or size 1 film is used with children with primary and mixed dentitions; size 2 film is too large for bite-wings on a small child and may cause pain, promoting undesirable behavior.)
Child sitting on parent’s lap for dental x-ray.
Both the child and his guardian are covered with a lead apron.
What is missing around the child’s neck? (Thyroid collar.)
What type of collimator/PID is shown in this photo? (Round/short, 8-inch.)
Why is there plastic over the tubehead? (For proper infection control.)
ALARA Concept
- The ALARA concept states that all exposure to radiation must be kept to a minimum, or “as low as reasonably achievable.”
- Every possible method of reducing exposure to radiation should be used to minimize risk.
- The radiation-protection measures detailed in this chapter should be used to minimize patient, operator, and staff exposure, keeping radiation exposure “as low as reasonably achievable.”
What are some precautions taken to abide by the ALARA concept? (Radiographs should be ordered only for diagnostic purposes; use the lowest possible kilovoltage, milliamperage, and exposure time; use F-speed film or digital radiography; use a longer, rectangular PID; use a tubehead with an aluminum filter and a lead collimator; use a lead apron and thyroid collar; use film-holding devices; avoid retakes; and test equipment for efficiency and proper function.)
Patient Questions
- Patients often have questions and concerns about radiation.
- As a dental assistant. you must be prepared to answer such questions and educate the dental patient about the importance of radiographs.
- Here are some examples of comments you can make to patients during informal discussions:
- “The doctor orders x-rays on the basis of your individual needs.”
- “Our office takes every step possible to protect you from unnecessary radiation.”
- “We use a lead apron and thyroid collar to protect your body from stray radiation.”
- “We use a high-speed film that requires only minimal amounts of radiation.”
- “Do you have any questions before we begin?”