When to consider the use of CBCT in endodontic treatment planning in adults

Guided endodontic treatment

Guided access in endodontics has resulted in improved success rates, efficiency and patient experience in both orthograde and surgical endodontics, as summarized in Table 1. The wealth of information about tooth morphology and surrounding structures provided by CBCT can be combined with scan data of the teeth using specialist software typically used for implant planning. The data may be from an intra-oral scan or scan of a cast from an alginate or silicone impression. Following this, a 3D drilling pathway is planned, and a guide to accommodate this either 3D printed or milled. Additionally, digital burs and files can be designed and superimposed via the software to allow personalized access to a tooth, and these can be miniaturized if conventional burs are too wide and unsuitable.¹³Figure 1 illustrates the stages involved in the fabrication of a surgical guide for access.

Guided access offers numerous benefits over conventional access cavities. Of utmost importance is the improved accuracy and predictability of canal location, which appears to be independent of operator experience.^{14,15,16,17,18} This may allow for considerably more complex cases, which may otherwise have been referred to specialist centres, to be carried out in primary care. Guided access techniques may also be more conservative than conventional approaches, thereby preserving tooth structure and integrity.^18,19 The use of guided access has also been reported to be more efficient, reducing surgery time by up to 30%.¹⁴

Supplemental or missed canals

CBCT demonstrates a superior ability to identify additional or supplemental canals,^20,21 thereby facilitating the preparation, disinfection and obturation of all canals, essential to eliminate bacteria and facilitate healing.^22,23 If canal anatomy is complex or peri-apical radiographs unclear, CBCT should be considered,²⁴ with prior assessment of anatomy reducing the likelihood of iatrogenic errors including ledges, transportations and perforations.²⁵ In the event of a perforation, or where a perforation is suspected, detection by 2D imaging may be challenging because of superimposition, particularly labial and lingual root surface defects²⁶ while 3D imaging has a greater ability to detect and assess,²⁷ again facilitating appropriate management.

Atypical root morphology

CBCT has also proved beneficial in the management of atypical root morphology, for example, dens invaginatus and dens evaginatus.^28,29 As well as facilitating a guided approach to treatment, the diagnostic value of CBCT is greater than 2D imaging in such cases. This allows clearer visualization of the precise location and depth of the pulpal tissue within the tubercle and intricacies of canal morphology, clarifying if and where there may be communications between the invagination and the primary canal. Other examples of challenging root morphology successfully treated with the aid of CBCT and guided access include dilaceration, hypercementosis and fibre post removal.^30,31,32

Resorption

Resorption is defined as a physiological or pathological process resulting in the loss of dentine, cementum and/or bone.³³ Diagnosis of resorption via CBCT has greater accuracy than peri-apical radiographs,^34,35 and is indispensable to properly diagnose and treatment plan more advanced resorption cases.⁴ Where operative intervention is planned, it is desirable to gain as much information as possible prior to undertaking irreversible procedures in order to make informed decisions. The importance of CBCT in treatment planning is illustrated in Figure 2. This is especially true in cervical resorption, which can be particularly aggressive.³⁶ This is recognized with the latest ESE position statement^3,5 in which a new 3D classification is recommended and it is acknowledged that a 2D classification³⁷ (Table 2) cannot fully identify the extent of the lesion, possibly resulting in inappropriate surgery when an extraction followed by replacement may be the most appropriate option. It is important to note that CBCT is only indicated where there are uncertainties regarding restorability or treatment options, as illustrated in Figure 3.

Dento-alveolar trauma

For patients presenting with dento-alveolar trauma, clinical and 2D radiographic examinations may be insufficient to assess pulpal and periodontal injury or healing and CBCT may aid diagnosis and treatment planning. The International Association of Dental Traumatology guidelines recognize that CBCT can provide enhanced visualization of traumatic dental injuries, including monitoring of healing and complications, while both the ESE and American Association of Endodontists state that CBCT should be considered in the diagnosis and management of dento-alveolar trauma and detection of secondary changes, where clinical examination and conventional imaging are inconclusive.^4,40,41 CBCT is particularly relevant in trauma to show a third dimension not present in peri-apical radiographs; eliminating errors that may occur with conventional intra-oral radiography including poor sensitivity detecting minimal displacements, missed diagnoses of root and alveolar fractures, superimposition and processing errors and therefore can improve the ability to accurately diagnose traumatic injuries.⁴²

When identifying root fractures, intra-oral radiographs have limited diagnostic yield, particularly where there is no fragment displacement or formation of granulation tissue, therefore, multiple radiographs at varying angles are recommended.^40,43 Accurate determination of the apical extent of a crown-root fracture is not always possible with 2D radiography and exploration of the location and extension of the fracture with a CBCT is strongly recommended to assess crown to root ratio which influences treatment options and long-term prognosis^.40,44 An increased detection rate of root fractures from 30–40% with 2D imaging to 90% with a CBCT has been reported.⁴⁵ The enhanced visualization of dento-alveolar injury through CBCT can show oblique components to fractures, alveolar bone fractures, displaced root fragments, subluxations and areas of trauma-induced root resorption that may otherwise not be detected and remain undiagnosed.

A further complication is that canal obliteration is a frequent finding following root fractures,^46,47 therefore these cases would certainly benefit from CBCT and potentially guided access techniques for endodontic management.

If there is any suspicion that dento-alveolar trauma is not diagnosed adequately on a 2D image, CBCT should be considered to aid both diagnosis and treatment planning. Figure 5 describes a case where a patient presented with trauma to several teeth and following CBCT, the treatment plan was altered significantly from that made when assessing peri-apical radiographs only. This additional information facilitated the most appropriate treatment option and avoided an approach which could have a negative biological and financial impact.

Apical periodontitis

Despite being the standard technique for diagnosis of apical periodontitis, 2D imaging may underdiagnose peri-apical radiolucencies because of superimposition and distortion. In cases with undiagnosed pain suggestive of apical periodontitis, where there is no clear pathology on a 2D image, CBCT may again be justified. Studies show a greater accuracy of CBCT in the diagnosis of apical pathology compared to peri-apical radiographs and suggest that a clinician would be able to differentiate most diseased and healthy teeth correctly with a high sensitivity and specificity.^{48,49,50,51,52} This may positively impact treatment planning when deciding whether to restore a large carious lesion or begin endodontic treatment, particularly if asymptomatic. Additionally, this may improve outcomes of endodontic therapy if CBCT leads to earlier diagnosis of apical periodontitis as the presence and size of a pre-operative radiolucency significantly reduces success (Table 3).

Review of endodontic treatment

As well as diagnosis of endodontic disease, CBCT may also be beneficial post-operatively in assessing the quality of root filling and post-treatment healing. CBCT may reveal more suboptimal root fillings than peri-apical radiographs, identifying more voids and the extent of over/under obturation, particularly in the bucco-lingual plane,⁵³ all of which can influence success (Table 3). Figure 6 is an example where endodontic treatment may appear to have been completed to a high standard two dimensionally, but 3D imaging suggests otherwise, offering an explanation for failure. The radiographic root apex does not always correspond with the clinical apex,⁵⁴ therefore CBCT can be considered a much more precise assessment of the root filling terminus where this is unclear from 2D imaging. ESE quality guidelines state that if a lesion is unchanged or only diminished, the outcome is ’uncertain’ and should be assessed for up to 4 years.⁵⁵ CBCT has a significantly superior ability to identify peri-apical lesions following root canal treatment,^51,52,56,57 leading us to question whether the existing estimated success rate of 83% for primary treatment⁵⁴ is overestimated while peri-apical radiographs are employed as the method for reviewing and whether CBCT should become the gold standard method.

Other pathology

Benefits are also seen in diagnosing other pathologies, especially where surgical intervention is considered. Figure 7 is another example of where the employment of CBCT altered diagnosis entirely and alternative treatment was provided to resolve symptoms and pathology.