The dental profession is committed to delivering the highest quality of care to each of its individual patients and applying advancements in technology and science to continually improve the oral health status of the U.S. population. These guidelines were developed to serve as an adjunct to the dentist’s professional judgment of how to best use diagnostic imaging for each patient. Radiographs can help the dental practitioner evaluate and definitively diagnose many oral diseases and conditions. However, the dentist must weigh the benefits of taking dental radiographs against the risk of exposing a patient to x-rays, the effects of which accumulate from multiple sources over time. The dentist, knowing the patient’s health history and vulnerability to oral disease, is in the best position to make this judgment in the interest of each patient. For this reason, the guidelines are intended to serve as a resource for the practitioner and are not intended as standards of care, requirements or regulations.
The guidelines are not substitutes for clinical examinations and health histories. The dentist is advised to conduct a clinical examination, consider the patient’s signs, symptoms and oral and medical histories, as well as consider the patient’s vulnerability to environmental factors that may affect oral health. This diagnostic and evaluative information may determine the type of imaging to be used or the frequency of its use. Dentists should only order radiographs when they expect that the additional diagnostic information will affect patient care. Based on this premise, the guidelines can be used by the dentist to optimize patient care, minimize radiation exposure and responsibly allocate health care resources. 1
The guidelines titled, "The Selection of Patients for X-Ray Examination" were first 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). The development of the guidelines at that time was spurred by concern about the U.S. population’s total exposure to radiation from all sources. Thus, the guidelines were developed to promote the appropriate use of x-rays. In 2002, the American Dental Association, recognizing that dental technology and science continually advance, recommended to the FDA that the guidelines be reviewed for possible updating. The FDA welcomed organized dentistry’s interest in maintaining the guidelines, and so the American Dental Association, in collaboration with a number of dental specialty organizations and the FDA, published updated guidelines in 2004. This report updates the 2004 guidelines and includes recommendations for limiting exposure to radiation.
Radiographs and other imaging modalities are used to diagnose and monitor oral diseases, as well as to monitor dentofacial development and the progress or prognosis of therapy. Radiographic examinations can be performed using digital imaging or conventional film. The available evidence suggests that either is a suitable diagnostic method.2-4 Digital imaging may offer reduced radiation exposure and the advantage of image analysis that may enhance sensitivity and reduce error introduced by subjective analysis.5
RECOMMENDATIONS FOR PRESCRIBING DENTAL RADIOGRAPHS
These recommendations are subject to clinical judgment and may not apply to every patient. They are to be used by dentists only after reviewing the patient’s health history and completing a clinical examination. Even though radiation exposure from dental radiographs is low, 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.
TYPE OF ENCOUNTER
PATIENT AGE AND DENTAL DEVELOPMENTAL STAGE
Child with Primary
Dentition (prior to eruption of first permanent tooth)
Transitional Dentition (after eruption of first permanent tooth)
Permanent Dentition (prior to eruption of third molars)
Adult, Dentate or
being evaluated for oral diseases
radiographic exam consisting of selected periapical/occlusal views and/or
posterior bitewings if proximal surfaces cannot be visualized or probed. Patients without evidence of disease and with open proximal contacts may not require a
radiographic exam at this time.
Individualized radiographic exam consisting of posterior bitewings with panoramic exam or posterior bitewings and selected periapical images.
Individualized radiographic exam consisting of posterior bitewings with panoramic exam or posterior bitewings and selected periapical images. A full mouth intraoral radiographic exam is preferred when the patient has
clinical evidence of generalized oral disease or a history of extensive dental treatment.
Individualized radiographic exam, based on clinical signs and symptoms.
Recall Patient* with
clinical caries or at increased risk for caries**
Posterior bitewing exam at 6-12 month intervals if proximal surfaces cannot be examined visually or with a probe
Posterior bitewing exam at 6-18 month intervals
Recall Patient* with no
clinical caries and not at increased risk for caries**
Posterior bitewing exam at 12-24 month
intervals if proximal surfaces cannot be examined visually or with a probe
Posterior bitewing exam at 18-36 month intervals
Posterior bitewing exam at 24-36 month intervals
TYPE OF ENCOUNTER (continued)
Child with Primary
Dentition (prior to eruption of first permanent tooth)
Transitional Dentition (after eruption of first permanent tooth)
Permanent Dentition (prior to eruption of third molars)
Adult, Dentate and
Recall Patient* with
Clinical judgment as to the need for and type of radiographic images for the evaluation of
periodontal disease. Imaging may consist of, but is not limited to, selected bitewing and/or periapical images of areas where periodontal disease (other than nonspecific gingivitis) can be demonstrated clinically.
Patient (New and Recall)
for monitoring of dentofacial growth and development, and/or assessment of dental/skeletal relationships
Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring of dentofacial growth and development or assessment of dental and skeletal relationships
Clinical judgment as
to need for and type of radiographic images for evaluation and/or monitoring of dentofacial growth and development, or assessment of dental and skeletal relationships. Panoramic or periapical exam to assess developing third molars
Usually not indicated for monitoring of growth and development. Clinical judgment as to the need for and type of radiographic image for evaluation of dental and skeletal relationships.
Patient with other
circumstances including, but not limited to, proposed or existing implants, other dental and craniofacial pathoses, restorative/endodontic
needs, treated periodontal disease and caries remineralization
Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring of these conditions
*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, previous implant-related pathosis 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
6. Evidence of dental/facial trauma
7. Mobility of teeth
8. Sinus tract (“fistula”)
9. Clinically suspected sinus pathosis
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 tooth erosion
EXPLANATION OF RECOMMENDATIONS FOR PRESCRIBING DENTAL RADIOGRAPHS
The explanation below presents the rationale for each recommendation by type of encounter and patient age and dental developmental stages.
New Patient Being Evaluated for Oral Diseases
Child (Primary Dentition)
Proximal carious lesions may develop after the interproximal spaces between posterior primary teeth close. Open contacts in the primary dentition will allow a dentist to visually inspect the proximal posterior surfaces. Closure of proximal contacts requires radiographic assessment.16-18 However, evidence suggests that many of these lesions will remain in the enamel for at least 12 months or longer depending on fluoride exposure, allowing sufficient time for implementation and evaluation of preventive interventions.19-21 A periapical/anterior occlusal examination may be indicated because of the need to evaluate dental development, dentoalveolar trauma, or suspected pathoses. Periapical and bitewing radiographs may be required to evaluate pulp pathosis in primary molars.
Therefore, an individualized radiographic examination consisting of selected periapical/occlusal views and/or posterior bitewings if proximal surfaces cannot be examined visually or with a probe is recommended. Patients without evidence of disease and with open proximal contacts may not require radiographic examination at this time.
Child (Transitional Dentition)
Overall dental caries in the primary teeth of children from 2-11 years of age declined from the early 1970s until the mid 1990s.22-24 From the mid 1990s until the 1999-2004 National Health and Nutrition Examination Survey, there was a small but significant increase in primary decay. This trend reversal was larger for younger children. Tooth decay affects more than one-fourth of U.S. children aged 2–5 years and half of those aged 12-15 years; however, its prevalence is not uniformly distributed. About half of all children and two-thirds of adolescents aged 12–19 years from lower-income families have had decay.25
Children and adolescents of some racial and ethnic groups and those from lower-income families have more untreated tooth decay. For example, 40 percent of Mexican American children aged 6–8 years have untreated decay, compared with 25 percent of non-Hispanic whites.25 It is, therefore, important to consider a child’s risk factors for caries before taking radiographs.
Although periodontal disease is uncommon in this age group,26 when clinical evidence exists (except for nonspecific gingivitis), selected periapical and bitewing radiographs are indicated to determine the extent of aggressive periodontitis, other forms of uncontrolled periodontal disease and the extent of osseous destruction related to metabolic diseases.27,28
A periapical or panoramic examination is useful for evaluating dental development. A panoramic radiograph also is useful for the evaluation of craniofacial trauma.15,29,30Intraoral radiographs are more accurate than panoramic radiographs for the evaluation of dentoalveolar trauma, root shape, root resorption31,32and pulp pathosis. However, panoramic examinations may have the advantage of reduced radiation dose, cost and imaging of a larger area.
Occlusal radiographs may be used separately or in combination with panoramic radiographs in the following situations: 1. unsatisfactory image in panoramic radiographs due to abnormal incisor relationship, 2. localizations of tooth position, and 3. when clinical grounds provide a reasonable expectation that pathosis exists.32-34
Therefore, an individualized radiographic examination consisting of posterior bitewings with panoramic examination or posterior bitewings and selected periapical images is recommended.
Adolescent (Permanent Dentition)
Caries in permanent teeth declined among adolescents, while the prevalence of dental sealants increased significantly.35,However, increasing independence and socialization, changing dietary patterns, and decreasing attention to daily oral hygiene can characterize this age group. Each of these factors may result in an increased risk of dental caries. Another consideration, although uncommon, is the increased incidence of periodontal disease found in this age group compared to children.36
Panoramic radiography is effective in dental diagnosis and treatment planning.30,37,38
Specifically, the status of dental development can be assessed using panoramic radiography.39
Occlusal and/or periapical radiographs can be used to detect the position of an unerupted or supernumerary tooth.40-42 Third molars also should be evaluated in this age group for their presence, position, and stage of development.
Therefore, an individualized radiographic examination consisting of posterior bitewings with panoramic examination or posterior bitewings and selected periapical images is recommended. A full mouth intraoral radiographic examination is preferred when the patient has clinical evidence of generalized oral disease or a history of extensive dental treatment.
Adult (Dentate or Partially Edentulous)
The overall dental caries experience of the adult population has declined from the early 1970s until the most recent (1999-2004) National Health and Nutrition Examination Survey.43
However, risk for dental caries exists on a continuum and changes over time as risk factors change.44 Therefore, it is important to evaluate proximal surfaces in the new adult patient for carious lesions. In addition, it is important to examine patients for recurrent dental caries.
The incidence of root surface caries increases with age.45 Although bitewing radiographs can assist in detecting root surface caries in proximal areas, the usual method of detecting root surface caries is by clinical examination.46
The incidence of periodontal disease increases with age.47 Although new adult patients may not have symptoms of active periodontal disease, it is important to evaluate previous experience with periodontal disease and/or treatment. Therefore, a high percentage of adults may require selected intraoral radiographs to determine the current status of the disease.
Taking posterior bitewing radiographs of new adult patients was found to reduce the number of radiological findings and the diagnostic yield of panoramic radiography.48,49In addition, the following clinical indicators for panoramic radiography were identified as the best predictors for useful diagnostic yield: suspicion of teeth with periapical pathologic conditions, presence of partially erupted teeth, caries lesions, swelling, and suspected unerupted teeth.50
Therefore, an individualized radiographic examination, consisting of posterior bitewings with selected periapical images or panoramic examination when indicated is recommended. A full mouth intraoral radiographic examination is preferred when the patient has clinical evidence of generalized oral disease or a history of extensive dental treatment.
The clinical and radiographic examinations of edentulous patients generally occur during an assessment of the need for prostheses. The most common pathological conditions detected are impacted teeth and retained roots with and without associated disease.51Other less common conditions also may be detected: bony spicules along the alveolar ridge, residual cysts or infections, developmental abnormalities of the jaws, intraosseous tumors, and systemic conditions affecting bone metabolism.
The original recommendations for this group called for a full-mouth intraoral radiographic examination or a panoramic examination for the new, edentulous adult patient. Firstly, this recommendation was made because examinations of edentulous patients generally occur during an assessment of the need for prostheses. Secondly, the original recommendation considered edentulous patients to be at increased risk for oral disease.
Studies have found that from 30 to 50 percent of edentulous patients exhibited abnormalities in panoramic radiographs.51-55 In addition, the radiographic examination revealed anatomic considerations that could influence prosthetic treatment, such as the location of the mandibular canal, the position of the mental foramen and maxillary sinus, and relative thickness of the soft tissue covering the edentulous ridge.51,53,55However, in studies that considered treatment outcomes, there was little evidence to support screening radiography for new edentulous patients. For example, one study reported that less than 4 percent of such findings resulted in treatment modification before denture fabrication, and another showed no difference in post- denture delivery complaints in patients who did not receive screening pretreatment radiographs.54,56
This panel concluded that prescription of radiographs is appropriate as part of the initial assessment of edentulous areas for possible prosthetic treatment. A full mouth series of periapical radiographs or a combination of panoramic, occlusal or other extraoral radiographs may be used to achieve diagnostic and therapeutic goals. Particularly with the option of dental implant therapy for edentulous patients,57radiographs can be an important aid in diagnosis,
prognosis, and the determination of treatment complexity.
Therefore, an individualized radiographic examination, based on clinical signs, symptoms, and treatment plan is recommended.
Recall Patient with Clinical Caries or Increased Risk for Caries
Child (Primary and Transitional Dentition) and Adolescent (Permanent Dentition)
Clinically detectable dental caries may suggest the presence of proximal carious lesions that can only be detected with a radiographic examination. In addition, patients who are at increased risk for developing dental caries because of such factors as poor oral hygiene, high frequency of exposure to sucrose-containing foods, and deficient fluoride intake (see caries risk assessment forms, 0 – 6 years of age
and over 6 years of age
) are more likely to have proximal carious lesions.
The bitewing examination is the most efficient method for detecting proximal lesions.16,18,58
The frequency of radiographic recall should be determined on the basis of caries risk assessment.15,59,60 It should be noted that a patient’s caries risk status may change over time and that an individual’s radiographic recall interval may need to be changed accordingly.61
Therefore, a posterior bitewing examination is recommended at 6 to 12 month intervals if proximal surfaces cannot be examined visually or with a probe.
Adult (Dentate and Partially Edentulous)
Adults who exhibit clinical dental caries or who have other increased risk factors should be monitored carefully for any new or recurrent lesions that are detectable only by radiographic examination. The frequency of radiographic recall should be determined on the basis of caries risk assessment.15,59,60 It should be noted that a patient’s risk status can change over time and that an individual’s radiographic recall interval may need to be changed accordingly.61
Therefore, a posterior bitewing examination is recommended at 6 to 18 month intervals.
Recall Patient (Edentulous Adult)
A study that assessed radiographs of edentulous recall patients showed that previously detected incidental findings did not progress and that no intervention was indicated.62 The data suggest that patients who receive continuous dental care do not exhibit new findings that require treatment.
An examination for occult disease in this group cannot be justified on the basis of prevalence, morbidity, mortality, radiation dose, and cost.53-55
Therefore, no radiographic examination is recommended without evidence of disease.
Recall Patient with No Clinical Caries and No Increased Risk for Caries
Child (Primary and Transitional Dentition)
Despite the general decline in dental caries activity, recent data show that subgroups of children have a higher caries experience than the overall population.63,64The identification of patients in these subgroups may be difficult on an individual basis. For children who present for recall examination without evidence of clinical caries and who are not considered at increased risk for the development of caries, it remains important to evaluate proximal surfaces by radiographic examination. In primary teeth the caries process can take approximately one year to progress through the outer half of the enamel and about another year through the inner
half.20,65-68 Considering this rate of progression of carious lesions through primary teeth, a time- based interval of radiographic examinations from one to two years for this group appears appropriate. The prevalence of carious lesions has been shown to increase during the stage of transitional dentition.25,69 Children under routine professional care would be expected to be at a lower risk for caries. Nevertheless, newly erupted teeth are at risk for the development of
Therefore, a radiographic examination consisting of posterior bitewings is recommended at intervals of 12 to 24 months if proximal surfaces cannot be examined visually or with a probe.
Adolescent (Permanent Dentition)
Adolescents with permanent dentition, who are free of clinical dental caries and factors that would place them at increased risk for developing dental caries, should be monitored carefully for development of proximal carious lesions, which may only be detected by radiographic examination. The caries process, on average, takes more than three years to progress through the enamel.20,65-68 However, evidence suggests that the enamel of permanent teeth undergoes posteruptive maturation and that young permanent teeth are susceptible to faster progression of carious lesions.70-73
Therefore, a radiographic examination consisting of posterior bitewings is recommended at intervals of 18 to 36 months.
Adult (Dentate and Partially Edentulous)
Adult dentate patients, who receive regularly scheduled professional care and are free of signs and symptoms of oral disease, are at a low risk for dental caries. Nevertheless, consideration should be given to the fact that caries risk can vary over time as risk factors change.
Advancing age and changes in diet, medical history and periodontal status may increase the risk for dental caries.
Therefore, a radiographic examination consisting of posterior bitewings is recommended at intervals of 24 to 36 months.
Recall Patient with Periodontal Disease
Child (Primary and Transitional Dentition), Adolescent (Permanent Dentition), and Adult
(Dentate and Partially Edentulous)
The decision to obtain radiographs for patients who have clinical evidence or a history of periodontal disease/treatment should be determined on the basis of the anticipation that important diagnostic and prognostic information will result. Structures or conditions to be assessed should include the level of supporting alveolar bone, condition of the interproximal bony crest, length and shape of roots, bone loss in furcations, and calculus deposits. The frequency and type of radiographic examinations for these patients should be determined on the basis of a clinical examination of the periodontium and documented signs and symptoms of periodontal disease. The procedure for prescribing radiographs for the follow-up/recall periodontal patient would be to use selected intraoral radiographs to verify clinical findings on a patient-by-patient basis.28,74
Therefore, it is recommended that clinical judgment be used in determining the need for, and type of radiographic images necessary for, evaluation of periodontal disease. Imaging may consist of, but is not limited to, selected bitewing and/or periapical images of areas where periodontal disease (other than nonspecific gingivitis) can be identified clinically.
Patient (New and Recall) for Monitoring of Dentofacial Growth and Development, and/or Assessment of Dental/Skeletal Relationships
Child (Primary and Transitional Dentition)
For children with primary dentition, before the eruption of the first permanent tooth,
radiographic examination to assess growth and development in the absence of clinical signs or symptoms is unlikely to yield productive information. Any abnormality of growth and development suggested by clinical findings should be evaluated radiographically on an individual basis. After eruption of the first permanent tooth, the child may have a radiographic examination to assess growth and development. This examination need not be repeated unless dictated by clinical signs or symptoms. Cephalometric radiographs may be useful for assessing growth, and/or dental and skeletal relationships.
Therefore, it is recommended that clinical judgment be used in determining the need for, and type of radiographic images necessary for, evaluation and/or monitoring of dentofacial growth and development, or assessment of dental and skeletal relationships.
Adolescent (Permanent Dentition)
During adolescence there is often a need to assess the growth status and/or the dental and skeletal relationships of patients in order to diagnose and treat their malocclusion. Appropriate radiographic assessment of the malocclusion should be determined on an individual basis.
An additional concern relating to growth and development for patients in this age group is to determine the presence, position and development of third molars. This determination can best be made by the use of selected periapical images or a panoramic examination, once the patient is in late adolescence (16 to 19 years of age).
Therefore, it is recommended that clinical judgment be used in determining the need for, and type of radiographic images necessary for, evaluation and/or monitoring of dentofacial growth and development, or assessment of dental and skeletal relationships. Panoramic or periapical examination may be used to assess developing third molars.
Adult (Dentate, Partially Edentulous and Edentulous)
In the absence of any clinical signs or symptoms suggesting abnormalities of growth and Therefore, in the absence of clinical signs and symptoms, no radiographic examination is recommended.
Patients with Other Circumstances
(including, but not limited to, proposed or existing implants, other dental and craniofacial pathoses, restorative/endodontic needs, treated periodontal disease and caries remineralization)
All Patient Categories
The use of imaging, as a diagnostic and evaluative tool, has progressed beyond the longstanding need to diagnose caries and evaluate the status of periodontal disease. The expanded technology in imaging is now used to diagnose other orofacial clinical conditions and evaluate treatment options. A few examples of other clinical circumstances are the use of imaging for dental implant treatment planning, placement, or evaluation; the monitoring of dental caries and remineralization; the assessment of restorative and endodontic needs; and the diagnosis of soft and hard tissue pathoses.
Therefore it is recommended that clinical judgment be used in determining the need for, and type of radiographic images necessary for, evaluation and/or monitoring in these circumstances.
LIMITING RADIATION EXPOSURE
Dental radiographs account for approximately 2.5 percent of the effective dose received from medical radiographs and fluoroscopies.75Even though radiation exposure from dental radiographs is low, 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. Examples of good radiologic practice include
- use of the fastest image receptor compatible with the diagnostic task (F-speed film or digital);
- collimation of the beam to the size of the receptor whenever feasible;
- proper film exposure and processing techniques;
- use of protective aprons and thyroid collars, when appropriate; and
- limiting the number of images obtained to the minimum necessary to obtain essential diagnostic information.
The American National Standards Institute and the International Organization for Standardization have established standards for film speed.76,7778The use of F-speed film can reduce exposure 20 to 50 percent compared to use of E-speed film, without compromising diagnostic quality. 79-85
Exposure of extraoral films such as panoramic radiographs requires intensifying screens to minimize radiation exposure to patients. The intensifying screen consists of layers of phosphor crystals that fluoresce when exposed to radiation. In addition to the radiation incident on the film, the film is exposed primarily to the light emitted from the intensifying screen. Previous generations of intensifying screens were composed of phosphors such as calcium tungstate. However, rare-earth intensifying screens are recommended because they reduce a patient’s radiation exposure by 50 percent compared with calcium tungstate-intensifying screens.86-89
Rare-earth film systems, combined with a high-speed film of 400 or greater, can be used for panoramic radiographs.86Older panoramic equipment can be retrofitted to reduce the radiation exposure to accommodate the use of rare-earth, high-speed systems.
Digital imaging provides an opportunity to further reduce the radiation dose by 40 to 60 percent.90-93In digital radiography, there are three types of receptors that take the place of conventional film: charge-coupled device (CCD), complementary-metal-oxide-semiconductor (CMOS), and photo-stimulable phosphor (PSP) plates. Systems that use CCD and CMOS- based, solid-state detectors are called “direct.” When these sensors receive energy from the x- ray beam, the CCD or CMOS chip sends a signal to the computer and an image appears on
the monitor within seconds. Systems that use PSP plates are called “indirect.” When these plates are irradiated, a latent image is stored on them. The plate is then scanned and the scanner transmits the image to the computer.
Holders that align the receptor precisely with the collimated beam are recommended for periapical and bitewing radiographs. Heat-sterilizable or disposable intraoral radiograph receptor-holding devices are recommended for optimal infection control.94Dental professionals should not hold the receptor holder during exposure.86 Under extraordinary circumstances in which members of the patient’s family (or other caregiver) must provide restraint or hold a receptor holder in place during exposure, such a person should wear appropriate shielding.86
Collimation limits the amount of radiation, both primary and scattered, to which the patient is exposed. An added benefit of rectangular collimation is an improvement in contrast as a result of a reduction in fogging caused by secondary and scattered radiation.89 The x-ray beam should not exceed the minimum coverage necessary, and each dimension of the beam should be collimated so that the beam does not exceed the receptor by more than 2 percent of the source-to-image receptor distance.86Since a rectangular collimator decreases the radiation dose by up to fivefold as compared with a circular one, 86,95,96 radiographic equipment should provide rectangular collimation for exposure of periapical and bitewing radiographs.86 Use of a receptor-holding device minimizes the risk of cone-cutting (non-exposure of part of the image receptor due to malalignment of the x-ray beam). The position-indicating device should be open ended and have a metallic lining to restrict the primary beam and reduce the tissue
volume exposed to radiation.86Use of long source-to-skin distances of 40 cm, rather than short distances of 20 cm, decreases exposure by 10 to 25 percent.86,97 Distances between 20 cm and 40 cm are appropriate, but the longer distances are optimal.86
OPERATING POTENTIAL AND EXPOSURE TIME
The operating potential of dental x-ray units affects the radiation dose and backscatter radiation. Lower voltages produce higher-contrast images and higher entrance skin doses, and lower deep-tissue doses and levels of backscatter radiation. However, higher voltages produce lower contrast images that enable better separation of objects with differing densities. Thus,
the diagnostic purposes of the radiograph should be used to determine the selection of kilovolt setting. A setting above 90 kV(p) will increase the patient dose and should not be used.89The optimal operating potential of dental x-ray units is between 60 and 70 kVp.86,89
Filmless technology is much more forgiving to overexposure often resulting in unnecessary radiation exposure. Facilities should strive to set the x-ray unit exposure timer to the lowest setting providing an image of diagnostic quality. If available, the operator should always confirm that the dose delivered falls within the manufacturer’s exposure index. Imaging plates should be evaluated at least monthly and cleaned as necessary.
PATIENT SHIELDING AND POSITIONING
The amount of scattered radiation striking the patient’s abdomen during a properly conducted radiographic examination is negligible.98The thyroid gland is more susceptible to radiation exposure during dental radiographic exams given its anatomic position, particularly in children.93,99,100Protective thyroid collars and collimation substantially reduce radiation exposure to the thyroid during dental radiographic procedures.101,10 Because every precaution should be taken to minimize radiation exposure, protective thyroid collars should be used whenever possible. If all the recommendations for limiting radiation exposure are put into practice, the gonadal radiation dose will not be significantly affected by use of abdominal shielding.86 Therefore, use of abdominal shielding may not be necessary.
Protective aprons and thyroid shields should be hung or laid flat and never folded, and manufacturer’s instructions should be followed. All protective shields should be evaluated for damage (e.g. tears, folds, and cracks) monthly using visual and manual inspection.
Proper education and training in patient positioning is necessary to ensure that panoramic radiographs are of diagnostic quality.
Although dental professionals receive less exposure to ionizing radiation than do other occupationally exposed health care workers,75,86operator protection measures are essential to minimize exposure. Operator protection measures include education, the implementation of a radiation protection program, occupational radiation exposure limits, recommendations for personal dosimeters and the use of barrier shielding.103The maximum permissible annual
dose of ionizing radiation for health care workers is 50 millisieverts (mSv) and the maximum permissible lifetime dose is 10 mSv multiplied by a person’s age in years.86Personal dosimeters should be used by workers who may receive an annual dose greater than 1 mSv to monitor their exposure levels. Pregnant dental personnel operating x-ray equipment should use personal dosimeters, regardless of anticipated exposure levels.86
Operators of radiographic equipment should use barrier protection when possible, and barriers should ideally contain a leaded glass window to enable the operator to view the patient during exposure.86 When shielding is not possible, the operator should stand at least two meters from the tube head and out of the path of the primary beam.103The National Council on Radiation Protection & Measurements report “Radiation Protection in Dentistry” offers detailed information on shielding and office design.86State radiation control agencies can help assess whether barriers meet minimum standards.
HAND-HELD X-RAY UNITS
Hand-held, battery-powered x-ray systems are available for intra-oral radiographic imaging.
The hand-held exposure device is activated by a trigger on the handle of the device. However, dosimetry studies indicate that these hand-held devices present no greater radiation risk than standard dental radiographic units to the patient or the operator. No additional radiation protection precautions are needed when the device is used according to the manufacturer’s instructions. These include: 1. holding the device at mid-torso height, 2. orienting the shielding ring properly with respect to the operator, and 3. keeping the cone as close to the patient’s
face as practical. If the hand-held device is operated without the ring shield in place, it is recommended that the operator wear a lead apron.
All operators of hand-held units should be instructed on their proper storage. Due to the portable nature of these devices, they should be secured properly when not in use to prevent accidental damage, theft, or operation by an unauthorized user. Hand-held units should be stored in locked cabinets, locked storage rooms, or locked work areas when not under the direct supervision of an individual authorized to use them. Units with user-removable batteries should be stored with the batteries removed. Records listing the names of approved individuals who are granted access and use privileges should be prepared and kept current.
FILM EXPOSURE AND PROCESSING
All film should be processed following the film and processer manufacturer recommendations. Once this is achieved, the x-ray operator can adjust the tube current and time and establish a technique that will provide consistent dental radiographs of diagnostic quality. Poor processing technique, including sight-developing, most often results in underdeveloped films, forcing the x-ray operator to increase the dose to compensate, resulting in patient and personnel being exposed to unnecessary radiation.
A safelight does not provide completely safe exposure for an indefinite period of
time. Extraoral film is much more sensitive to fogging. The length of time for which a film can be exposed to the safelight should be determined for the specific safelight/film combination in use.
Quality assurance protocols for the x-ray unit, imaging receptor, film processing, dark room, and patient shielding should be developed and implemented for each dental health care setting.86All quality assurance procedures, including date, procedure, results, and corrective action, should be logged for documentation purposes. A qualified expert should survey all x- ray units on their placement and should resurvey the equipment every four years or after any changes that may affect the radiation exposure of the operator and others.86 Surveys typically are performed by state agencies, and individual state regulations should be consulted regarding specific survey intervals. The film processor should be evaluated at its initial installation and on a monthly basis afterward. The processing chemistry should be evaluated daily, and each type of film should be evaluated monthly or when a new box or batch of film is opened.86 Abdominal shielding and thyroid collars should be inspected visually for creases or clumping that may indicate voids in their integrity on a monthly basis.86Damaged abdominal shielding and collars should be replaced. Table 2 lists specific methods of quality assurance procedures, covering not only inspection of the x-ray unit itself but also of the film processor, the image receptor devices, the darkroom and abdominal shielding and collars.103,104
It is imperative that the operator’s manual for all imaging acquisition hardware is readily available to the user, and that the equipment is operated and maintained following the manufacturer’s instructions, including any appropriate adjustments for optimizing dose and image quality.
Size-based technique charts/protocols with suggested parameter settings are important for ensuring that radiation exposure is optimized for all patients. Technique charts should be used for all systems with adjustable settings, such as tube potential, tube current, and time or pulses. The purpose of using the charts is to control the amount of radiation to the patient and receptor. Technique charts are tables that indicate appropriate settings on the x-ray unit for a specific anatomical area and will ensure the least amount of radiation exposure to produce a consistently good-quality radiograph.
Technique charts for intraoral and extraoral radiography should list the type of exam, the patient size (small, medium, large) for adults and a pediatric setting. The speed of film used, or use of a digital receptor, should also be listed on the technique chart. The chart should be posted near the control panel where the technique is adjusted for each x-ray unit. A technique chart that is regularly updated should be developed for each x-ray unit. The charts will also need to be updated when a different film or sensor, new unit, or new screens are used.
RADIATION RISK COMMUNICATION
Dentists should be prepared to discuss with their patients the benefits and risks of the x-ray exam.105To help answer patient and parent questions about dental radiology radiation safety, the American Academy of Oral and Maxillofacial Radiology and the Alliance for Radiation Safety in Pediatric Imaging partnered to create a brochure targeted at parents and patients.106
Quality Assurance Procedures for Assessment of Radiographic Equipment
The following procedures for periodic assessment of the performance of radiographic equipment, film processing,
equipment, image receptor devices, dark room integrity, and abdominal and thyroid shielding are adapted from the National Council for Radiation Protection and Measurements report, “Radiation Protection in Dentistry.”86
Please refer to state guidelines for specific regulations.
At regular intervals as recommended by state regulations
Whenever there are any changes in installation workload or operating conditions
Inspection by qualified expert (as specified by
government regulations and manufacturers recommendations).
Method 1: Sensitometry and Densitometry
A sensitometer is used to expose a film, followed by standard processing of the film. The processed film will have a defined pattern of optical densities.
The densities are measured with a densitometer.
The densitometer measurements are
compared to the densities of films exposed and processed under ideal conditions.
A change in densitometer values indicates a problem with either the development time, temperature or the developer solutions. Advantages
Accuracy Speed Disadvantage
Expense of additional equipment
Method 2: Reference Film
A film exposed and processed under ideal conditions is attached to the corner of a view box as a reference film.
Subsequent films are compared with the reference film.
Image Receptor Devices
Intensifying Screen and
With each new batch of film
Every six months
Method 1: Sensitometry and Densitometry
(as described above)
Method 2: Reference Image (as described
Visual inspection of cassette integrity
Examination of intensifying screen for
Development of an unexposed film that has been in the cassette exposed to normal lighting for one hour or more
After a change in the lighting filter or lamp
While in a darkroom with the safelight on, place metal object (such as a coin) on unwrapped
film for a period that is equivalent to the time required for a typical darkroom procedure Develop film
Detection of the object indicates a problem with the safelight or light leaks in the darkroom
Abdominal and Thyroid
Monthly (visual and manual inspection)
All protective shields should be evaluated for damage (e.g., tears, folds, and cracks) monthly
using visual and manual inspection. If a defect in the attenuating material is suspected, radiographic or fluoroscopic inspection may be
performed as an alternative to immediately removing the item from service. Consideration
should be given to minimizing the radiation
exposure of inspectors by minimizing unnecessary fluoroscopy.
TRAINING AND EDUCATION
Where permitted by law, auxiliary dental personnel can perform intraoral and extraoral imaging.103 Personnel certified to take dental radiographs should receive appropriate education. Practitioners should remain informed about safety updates and the availability of new equipment, supplies and techniques that could further improve the diagnostic quality of radiographs and decrease radiation exposure. Free training materials are available for limiting radiation exposure in dental imaging through the International Atomic Energy Agency.107
Dentists should conduct a clinical examination, consider the patient’s oral and medical histories, as well as consider the patient’s vulnerability to environmental factors that may affect oral health before conducting a radiographic examination. This information should guide the dentist in the determination of the type of imaging to be used, the frequency of its use, and the number of images to obtain. Radiographs should be taken only when there is an expectation that the diagnostic yield will affect patient care.
Dentists should develop and implement a radiation protection program in their offices. In addition, practitioners should remain informed on safety updates and the availability of new equipment, supplies, and techniques that could further improve the diagnostic ability of radiographs and decrease exposure.
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