Cysts. A cyst is a closed sac lined with epithelium that contains fluid and may become infected or neoplastic or damage surrounding
structures. Cystic structures will appear as radiolucent areas with smooth bony edges. Similar to other benign growths, they
grow by expansion and, thus, displace the other structures (e.g. teeth). A dentigerous cyst is typically seen as a radiolucent structure centered on the crown of an unerupted tooth (Figure 19).
Benign neoplasia. Most benign neoplastic growths have no bone involvement on dental radiographs. If bone involvement does occur, it will typically
be expansive (Figure 20) because benign oral soft tissue neoplasms do not generally directly invade or infiltrate bone. This pattern of growth will
result in the bone pulling away from the advancing tumor, leaving a decalcified soft tissue-filled space in the tumor site.28 Bone margins are usually distinct. This expansive growth will typically result in tooth movement.
Malignant neoplasia. Malignant oral neoplasms invade bone early in the course of disease and result in irregular, ragged bone destruction.27 Initially, the bone will have an irregularly mottled, moth-eaten appearance (Figure 21), but radiographs late in the disease course will reveal a complete loss of bone in the area (the teeth will appear to float
in space) (Figure 22). If the cortex is involved, an irregular appearance will be seen because of the cortical bone spicules being forced outward.
In advanced cases, the root apices may develop a spiked appearance because of root resorption.
Differential diagnoses for neoplastic diseases include osteomyelitis (bacterial or fungal) and periodontal, endodontic, and
metabolic bone disease (Figure 23).
Histologic testing is always necessary to accurately diagnose oral masses since a variety of benign and malignant tumors appear
radiographically similar. In addition, osteomyelitis can create similar radiographic findings as malignant tumors. Finally,
malignant or invasive tumors may show no bone involvement early in the course of disease. Be sure to note the type and extent
of any bone involvement on the histologic examination request form (and possibly include copies of the radiographs and pictures)
to aid the pathologist. Always interpret the histologic examination results in light of the radiographic findings. Question
a diagnosis of a malignancy without bone involvement before initiating definitive therapy such as aggressive surgery, radiation
therapy, or chemotherapy. Conversely, a benign tumor diagnosis with marked bone reaction should be further investigated before
assuming that the patient is safe.
Oral trauma
On dental radiographs, oral traumatic injuries (fractures) appear similar to comparable injuries in the appendicular skeleton.
Resolution is the major difference. A postoperative dental radiograph of a case with proper surgical reduction will still
reveal a fracture line disturbance (Figure 24). This must be considered when evaluating fracture displacement and fixation quality.
Figures 20, 21, 22, 23, 24, 25A, 25B
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Root fractures and roots in fracture lines (Figures 25A & 25B) must be evaluated in these cases, as they may alter the treatment plan, fixation options, or future therapy. Proper radiographic
interpretation is critical in the area of the mandibular first molar in older small- and toy-breed dogs, as pathologic fractures
are quite common. These fractures occur when the mandible has been severely weakened by endodontic or more commonly periodontal
disease. Standard radiographic resolution is often inadequate for diagnosing small periapical or periodontal lesions that
contributed to the fracture. The increased detail of dental radiographs is required for proper diagnosis. Finally, if a mandibular
fracture is not responding to what is considered proper therapy, dental radiographs may elucidate the cause of the nonunion
(Figure 26).
Retained tooth roots
Figures 26, 27A, 27B
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Retained tooth roots after extraction attempts are common in veterinary medicine (Figures 27A & 27B). In most cases, no clinical signs are obvious, but the patient may suffer silently. In rare cases, the retained root may
lead to abscess formation, resulting in marked morbidity to the patient and possible legal action from the client.
Regardless of the appearance of complete extraction, retained roots or other pathologies are still possible. Thus, postoperative
radiographs are critical and must be obtained after all extractions. In addition, they will serve as a legal document in cases
with complications. Finally, the AAHA Dental Care Guidelines for Dogs and Cats mandate postoperative radiographs on all extraction
cases to ensure complete removal.31
CONCLUSION
It is impossible to perform proper dental therapy without dental radiography. Appropriate exposure technique and interpretation
will greatly improve the quality of dental care within your practice.
Editors' Note: Dr. Niemiec is a co-founder of the dental radiography consultation service VetDentalRad.com.
Brook A. Niemiec, DVM, DAVDC, FAVD
Southern California Veterinary Dental Specialists
5610 Kearny Mesa Road, Suite B1
San Diego, CA 92111
bn@vetdentalrad.com
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