8.1 Digital Imaging in Endodontics
Dental radiography is essential for the successful diagnosis of oral pain, odontogenic or nonodontogenic, treatment of the root canal system, evaluation of the final obturation, and assessment of healing after endodontic treatment. These images are necessary for visualization of the pulp chamber and root canal space such as pulp chamber location, pulp stones, pulp chamber and root canal calcification, number of roots and canals, canal bifurcations, dilacerations, resorptions, and root length. The surrounding periapical tissues must be evaluated radiographically for radiolucent and radiopaque areas, periodontal bone levels and defects, anatomical structures, odontogenic and nonodontogenic pathologies, and anomalous dental defects. When viewed in total, endodontic radiography is crucial to making an accurate diagnosis, developing an endodontic treatment plan and executing treatment with the knowledge of obstacles that may be encountered during treatment.
Traditionally, radiographic assessment in endodontic diagnosis and treatment has been limited to intraoral and panoramic radiography. These modalities provide a two‐dimensional representation of three‐dimensional anatomical structures. In cases with complex anatomy and surrounding structures, interpretation of these two‐dimensional images can be difficult and may lead to misinterpretation of the situation.
With the advent of CBCT, images can be generated that make it possible to view oral structures and the surrounding maxillofacial skeleton and anatomical relationships in three dimensions. While this technology is impressive, it does have limitations such as higher radiation dose to the patient and generation of artifacts.
Cone beam computed tomography should not be used routinely for endodontic diagnosis or screening purposes in the absence of any clinical signs or symptoms. It should only be used when the patient’s history and clinical examination demonstrate that the benefits to the patient outweigh the potential risks and the need for imaging cannot be met by two‐dimensional imaging. In all cases, the “as low as reasonably achievable” (ALARA) principle should be observed.
8.1.1 Recommendations for Endodontic Imaging
- Diagnosis: 2D should be used for the initial imaging. 3D should be used after 2D imaging for diagnosis of patients presenting with contradictory or nonspecific signs or symptoms, such as in cases of suspected vertical root fracture.
- Treatment: 3D imaging should be considered, after the initial diagnosis and radiographic evaluation are complete, for those situations where complex endodontic morphology is suspected, such as mandibular anterior teeth, maxillary and mandibular premolars and molars or other dental anomalies such as extensive dens invaginatus.
- Intraoperative: 2D imaging should be considered the modality of choice for working length (WL) determination, post space depth, etc.
- Postoperative: 2D imaging should be considered the modality of choice for assessment of the final obturation.
- Outcome assessment: 2D imaging should be considered the primary choice. 3D can be used in situations of nonhealing previous endodontic treatment after a sufficient posttreatment period to allow for healing to be noted.
- Nonsurgical endodontic retreatment: 3D should be considered the primary choice for better determination of factors leading to the need for retreatment.
- Surgical endodontic treatment: 3D imaging should be considered the primary choice for assessing anatomical structures that may be impacted during surgical treatment.
- Traumatic injuries: 3D imaging should be considered the primary choice for determination of any fractures, dislocations, intrusions or impactions or involvement of any of the other maxillofacial structures.
- Resorptions and perforations: 3D imaging should be considered the primary choice for determining location, size, and accessibility for repair.
8.2 Electronic Apex Location
Electronic apex location (EAL) has become more widely used in root canal treatment for determination of WL, replacing the more traditional radiographic method of WL determination. EAL is highly accurate in determination of WL (92–95%) compared to radiographic determination (85%). EAL offers a means of locating the most appropriate endpoint for root canal procedures. The principle behind most EAL devices is that human tissues have certain electrical characteristics that can be used in mathematical algorithms to determine the canal terminus.
The disadvantage or limitation of the radiographic technique is that it is sensitive in both exposure and interpretation. These limitations include operator interpretation of the root end, film positioning, angulation, and patient compliance. Also, in some cases, multiple radiographs may be necessary for this determination, thus exposing the patient to excess radiation.
Two‐dimensional and 3D radiographic techniques are useful in determining an estimated WL. While 2D films do not accurately reflect the 3D reality of the root canal space, 3D imaging has its own limitations as well. With both digital radiographic imaging modalities, the root canal length can be estimated using the measuring tools available in the digital radiography software; it cannot always take into account the intraoral reference point used during canal length determination and instrumentation. Therefore, EAL becomes a more accurate method for determining the WL intraorally, with the radiographic measurement giving guidance.