CBCT: A Three-Dimensional Look at Endodontic Diagnosis
Using technology to bring diagnosis and treatment planning to the next level
The dental history, clinical examination, and two-dimensional (2D) radiography provide the foundation for endodontic diagnostics. In many instances, the data obtained from these sources provide sufficient information to both diagnose pathology and establish appropriate treatment options. Despite a thorough workup, however, clinical situations occasionally arise in which additional diagnostic information is necessary to determine the type or extent of pathology or to rule out unsuitable treatment choices.
Diagnosis in Three Dimensions
Cone beam CT (CBCT) imaging, in many cases, offers information necessary to solve the diagnostic puzzle and establish suitable treatment possibilities. Historically, practitioners were encouraged to obtain several angled radiographs when diagnostic difficulties were encountered.1 Small field-of-view CBCT technology largely obviates this need by providing an accurate, three-dimensional representation of endodontic pathology at a radiation dose comparable to several radiographs.2 In endodontics, situations in which three-dimensional (3D) data may aid the diagnostic process include challenging diagnoses, assessment of traumatic dental injuries, fracture evaluation, examination of resorptive defects, and assessment of recurrent pathology in previously endodontically treated teeth.
The diagnosis of endodontic pathology involves the accurate reproduction of the chief complaint by clinical testing and support of the clinical diagnosis by radiographic data. Unfortunately, situations may arise in which these examinations do not provide sufficient diagnostic information. Clinical testing may prove inaccurate, particularly in heavily restored patients or in those with severe intrapulpal calcifications. Furthermore, 2D radiography may not accurately visualize bony defects. Following an inconclusive clinical exam or normal-appearing periapical radiograph despite patient pain complaints, 3D radiographic data obtained from CBCT imaging may provide essential diagnostic information. Periapical radiographs are limited by structural overlap, often termed “anatomic noise.”3 The projection of overlying anatomy, including the maxillary sinus walls, zygomatic arches, and thick mandibular cortical bone, often obscures periapical lesions confined to cancellous bone, causing clinicians to overlook existing pathology. CBCTs remove the influence of anatomic noise, allowing clinicians to detect pathology not visualized by periapical radiographs. One study found that CBCTs are able to detect 34% more apical pathology than periapical radiographs alone.4 Appropriate use of CBCT technology in difficult diagnostic cases can eliminate confusion and obviate the need for diagnostic follow up exams.
The assessment of traumatic orofacial injuries may also benefit from CBCT data. Though traumatic dental injuries often present with obvious signs of orofacial damage, intra-bony oblique fractures are often difficult to visualize and may exist concomitantly with other injuries. The ability to rule out additional pathology and establish reasonable treatment expectations for patients and parents justifies the use of this technology in many trauma cases. The American Association of Endodontists guidelines for the diagnosis and treatment of traumatic dental injuries provide a detailed framework for the evaluation and treatment of traumatized patients. They recommend obtaining CBCT data in cases of crown-root fractures; root fractures; alveolar fractures; concussions; subluxations; extrusive, lateral, and intrusive luxations; and avulsions.5 The additional information garnered from CBCT imaging can determine the extent and direction of dental and alveolar fractures, degree of periodontal ligament damage, and presence of other injuries. The additional information can shape appropriate treatment and offer more comprehensive prognostic expectations.
Visualizing Root Fractures
Just as CBCT imaging can assist in the diagnosis of traumatic dental fractures, it can also prove useful for the diagnosis of non-traumatic root fractures. As root fractures necessitate extraction, accurate diagnosis of their presence or absence is essential to prevent both the maintenance of hopeless teeth and the extraction of healthy teeth. Though a clinical examination revealing isolated deep probing depths, coronal sinus tracts, or evidence of coronal craze lines may suggest that a fracture is present, periapical radiographs rarely visualize fractures.
CBCT imaging can, in some cases, capture root fractures in the scan volume. A recent study found CBCTs can depict root fractures, particularly those with greater than 50 micrometers of separation.6 In cases where the fracture is not visible on the scan, other diagnostic information can be gained to support the fracture diagnosis. Findings associated with root fracture include loss of bone mid-root, absence of the entire buccal plate, a mid-root radiolucency in the area of post termination, and space between the buccal or lingual plate and the root surface.7 Taken together with the clinical data, the additional diagnostic data obtained from the CBCT scan provide clinicians more confidence in the diagnosis of root fractures.
Examining Resorptive Defects
CBCT imaging is exceptionally useful to both diagnose resorption and plan for its treatment. Although periapical radiographs alone often depict resorptive defects, little information is garnered about their extent, including the presence or absence of perforations. Furthermore, periapical radiographs may not differentiate between internal resorption, external resorption, or invasive cervical root resorption. Historically, clinicians often took multiple angles of radiographs to discern the location and extent of the defect. The lack of dimensionally accurate information, however, often led to the performance of exploratory root canal therapy, a time-consuming and expensive procedure. CBCT technology can largely eliminate the need for exploratory treatment by providing accurate three dimensional representations of resorptive defects including the type of resorption present and the possibility of perforation.8 Preoperative information can prevent exploratory treatment and can better direct clinical resources toward saving teeth with a reasonable expectation of a favorable outcome.
Diagnosing Recurrent Pathology
The assessment of recurrent apical pathology in previously endodontically treated teeth can also benefit from CBCT data. Retreatment outcomes are most favorable when the cause of treatment failure is identified and corrected.9 In many cases, failure reasons may be obvious based on clinical or radiographic data. For instance, the clinical exam may reveal recurrent caries under the coronal restoration, or the periapical radiograph might visualize an exceptionally short fill. In cases where both the restorative and endodontic treatment appears sufficient despite the presence of radiographic pathology, a CBCT scan can often visualize the presence or absence of untreated anatomy. This information gives confidence to both clinicians and patients when deciding whether or not to pursue retreatment.