Although occlusal, buccal, and lingual carious lesions are reasonably easy to detect clinically, interproximal caries and caries associated with existing restorations are much more difficult to detect with a clinical examination only (see Chapter 18). Studies have repeatedly demonstrated that clinicians using intraoral images detect caries not evident clinically, both in enamel and in dentin. Although a radiologic examination is very important for diagnosis of dental caries, the optimal frequency for such an examination should be based on mitigating features, such as the patient’s age, medical condition, diet, oral hygiene practices, oral health status, and the nature of the caries process itself.

Carious lesions demonstrate one of three behaviors: (1) progression, (2) arrest, or (3) regression. Only about 50% of lesions progress beyond the initial, just-detectable defect, and in most instances the lesions demonstrate a slow rate of progression through enamel (months to years). Mechanisms are also in use to enhance remineralization of early enamel lesions. However, the rate of caries progression is significantly faster in deciduous enamel than in permanent enamel, and patients vary widely in their rates of formation of caries and in their rates of caries progression.

Because the presence of caries cannot be determined with confidence by clinical examination alone, it is necessary to expose patients periodically through bitewing radiographs to monitor dental caries. The length of the exposure intervals varies considerably because of different patient circumstances. For most patients in good physical health with adequate oral hygiene, an infrequent radiologic examination is needed to monitor dental caries. However, if the patient history and clinical examination suggest that the individual has a relatively high caries experience, shorter intervals allow careful monitoring of disease.

Some form of periodontal disease affects most people at some point during their lives, gingivitis more often in younger individuals and periodontitis more commonly in older adults. Periodontal diseases are responsible for a substantial portion of all teeth lost. A consensus exists among practitioners that radiologic examinations play an important role in the evaluation of patients with periodontal disease after the disease is initially detected on clinical examination (see Chapter 19). In addition to providing a picture of the extent of alveolar bone support for the dentition, radiologic examinations help demonstrate local factors that complicate the disease, including the presence of gingival irritants such as calculus and faulty restorations. Occasionally, the length and morphologic features of roots, visible on periapical radiographs, are crucial factors in the prognosis of the disease. These observations suggest that when clinical evidence exists of periodontal disease other than nonspecific gingivitis, it is appropriate to make intraoral images, generally a combination of periapical and bitewing images, to help establish the severity of the disease. Follow-up images after therapy is complete help the clinician monitor the progression of disease and determine whether the destruction of alveolar bone has been halted.

Abnormal formation of teeth may be manifested as deviations in number, size, and composition. These abnormalities in dental development occur more frequently and are more likely to have a serious impact in the permanent dentition than in the primary dentition. The most frequently encountered anomalies are the presence of supernumerary teeth, usually mesiodens, or developmentally absent teeth, usually second premolars (see Chapter 31).

Only a few anomalies exist for which orthodontic treatment or surgical correction or modification must start at an early age. When the dentist suspects an abnormality requiring treatment, diagnostic images to confirm and localize it are not required until the time when the treatment is most appropriate. For example, a panoramic examination of a 5-year-old child to determine the presence or absence of permanent teeth may be poorly timed. Although the examination provides evidence that one or more second premolars or lateral incisors are developmentally missing, this information usually does not influence the current treatment plan. When examination for dental anomalies is appropriate, both the radiation dose and the anticipated diagnostic benefit should be considered. Projections that best demonstrate the required diagnostic information should be selected. A panoramic image of the lower face is usually best for observing the presence or absence of teeth in all quadrants, although a periapical or occlusal radiograph is sufficient for an examination limited to one area.

Children and adolescents are often examined to assess the growth and development of the teeth and jaws. This assessment considers the relationship of one jaw to the other and to the soft tissues. An examination of occlusion, growth, and development requires an individualized radiologic examination that may include periapical radiographs or a panoramic view to supplement other images ordered to assess dental disease. In addition, a patient of any age group who is being considered for orthodontic treatment may need other images, such as lateral or posteroanterior cephalometric, occlusal, carpal index (wrist), or temporomandibular joint (TMJ) images, depending on the clinical findings (Fig. 16-1).

CBCT imaging is being used increasingly frequently for orthodontic evaluation to provide three-dimensional information about jaw relationships and to substitute for multiple other imaging examinations (see Chapters 11 and 12). At the present time, it is unclear which patients would benefit from CBCT imaging in terms of treatment considerations. There is adequate information in the literature to demonstrate the value of CBCT imaging in the evaluation and treatment of impacted teeth but less information on other conditions of interest in orthodontics. The American Association of Orthodontists and the American Academy of Oral and Maxillofacial Radiology more recently developed a joint position statement on the use of CBCT imaging in orthodontics. Broadly, the statement recommends using CBCT imaging only when justified by individual need and the clinical question cannot be answered by using lower dose conventional imaging. Dose-reduction protocols should be used when possible. CBCT imaging is also used in some cases of impacted mandibular third molars when the relationship of the inferior alveolar nerve to the root apex is unclear with conventional images.

The dentist who is the primary provider of orthodontic treatment should select the number and type of images needed. The needs of each patient should be considered individually. Selecting the appropriate images should allow a maximal diagnostic yield with a minimal radiation exposure after consideration of the clinical examination, the study of plaster models and photographs, and the optimal time to initiate treatment.

Occult disease refers to disease that presents no clinical signs or symptoms. Occult diseases in the jaws include a combination of dental and intraosseous findings. Dental findings may include incipient carious lesions, resorbed or dilacerated roots, and hypercementosis. Intraosseous findings include osteosclerosis, unerupted teeth, periapical disease, and a wide variety of cysts and benign and malignant tumors (see Chapters 20 to 26). Small carious lesions, resorption of root structure, and bony lesions may go unnoticed until signs and symptoms develop.

Although the consequences of some occult diseases may be quite serious, most serious diseases are rare. Often a historical or clinical sign or symptom of intraosseous disease suggests its presence. For instance, an unusual contour of bone or an absent third molar, not explained by a history of extraction, suggests the possibility of an impaction with the potential for an associated dentigerous cyst. Although patient history and clinical signs and symptoms do not always accurately predict dental and intraosseous findings, most of these true occult diseases are not clinically relevant, or they are so rare that except for caries as described previously the dentist need not obtain a radiologic examination of the jaws solely to screen for them in dentate individuals in the absence of unusual clinical signs or symptoms. Caries is an exception because of its much higher prevalence than other occult diseases.

There is a considerable difference of opinion regarding whether asymptomatic edentulous patients seen for routine denture construction should have screening images taken to look for occult disease. Several studies have demonstrated a relatively large number of findings in diagnostic images of edentulous patients, including retained root tips and areas of sclerotic bone, but almost all these findings required no treatment and did not affect the outcome of care. For that reason, some experts recommend no images of edentulous patients if the clinical examination is negative for signs and symptoms of disease. Others think that screening radiographs of these patients are of value. As the standard of care for completely or partially edentulous patients moves toward dental implants rather than removable prosthetics, imaging to assess the quantity and quality of bone available for implants is gaining in importance.

There has been increasing interest in the last few years in using panoramic images to screen patients for the presence of calcified atheromas in the bifurcation of the carotid artery, a finding that may indicate an increased risk for the development of a cerebrovascular accident (stroke). However, the value of this finding has been questioned more recently because a noncalcified vulnerable plaque, which is not visible on panoramic radiographs, may put the patient at more risk for stroke than a more stable calcified plaque. Nevertheless, the general consensus at this time is that panoramic images made for dental purposes should be evaluated for this calcification, particularly in patients older than 55 years, but that these images should not be made simply to screen for atheromas without other dental indications. (See Chapter 28 for more details.)

Imaging of known jaw lesions, such as fibro-osseous diseases or neoplastic diseases, before biopsy and definitive treatment, is also important for appropriate management of the patient. For small lesions of the jaws, periapical or panoramic radiographs may be enough as long as the lesion can be seen in its entirety. If clinical evidence of swelling exists, some type of radiograph at 90 degrees to the original plane (often an occlusal image) should be made to determine whether there is expansion of the jaw or perforation of the buccal or lingual cortical bone. If lesions are too large to fit on standard dental radiographs, extend into the maxillary sinus or other portions of the head outside the jaws, or are suspected to be malignant, additional imaging such as medical computed tomographic (CT) imaging or CBCT imaging is appropriate before biopsy (see Chapters 11 to 14). Both of these types of images can provide excellent bone detail, but if there is a suspicion that the lesion may involve the surrounding soft tissue, medical CT imaging should be used instead of CBCT imaging because it can provide images of the soft tissue. These types of imaging can define the extent of the lesion, indicate an appropriate biopsy site, suggest an operative approach, and provide information about the nature of the lesion. If the lesion is not based in bone but in the adjacent soft tissue, magnetic resonance (MR) imaging, which has superior contrast resolution of soft tissue, should be used. In the initial steps of the investigation, referral to an oral and maxillofacial radiologist to order and report on the most appropriate diagnostic imaging before the biopsy procedure is reasonable.

Many types of diseases affect the TMJ, including congenital and developmental malformations of the mandible and cranial bones; acquired disorders such as disk displacement, neoplasms, fractures, and dislocations; inflammatory diseases that produce capsulitis or synovitis; and arthritides of various types, including rheumatoid arthritis and osteoarthritis. The goal of TMJ imaging, similar to that for imaging other body parts, should be to obtain new information that would influence patient care. Radiologic examination may not be needed for all patients with signs and symptoms referable to the TMJ region, particularly if no treatment is contemplated (see Chapter 27). The decision regarding whether and how to image the joints should depend on the results of the history and clinical findings, the clinical diagnosis, degree of diagnostic certainty required, and results of prior examinations as well as the tentative treatment plan and expected outcome.

The cost of the examination and the radiation dose should also influence />