Non-surgical and Surgical Re-treatment
Endodontic treatment has a high success rate (Ng et al, 2011); however, on occasion treatment may fail. Several factors have been reported to contribute to the failure of endodontically treated teeth (Siqueira, 2001; Ng et al, 2007; Azim et al, 2015).
The management of failed root canal treatment is dependant on the mode of failure, which may be multi-factorial (Fig 8-1). Treatment options commonly include non-surgical endodontic re-treatment, surgical re-treatment, extraction, and no treatment. Other less-frequent treatment options include root amputation and intentional implantation.
An effective treatment plan can only be devised when firstly, the diagnosis, and secondly the reason behind treatment failure have been determined. This chapter will explore how the data obtained by cone beam computed tomography (CBCT) may influence clinical decision making and the overall treatment planning in managing failed endodontically treated teeth (Fig 8-1).
Non-surgical endodontic re-treatment
CBCT has been shown to be useful in the management of failed root canal treatments (Davies et al, 2015b) and may provide information regarding the presence, exact location (root) and nature of periapical lesions that may not be readily detected on conventional radiographs (Simon et al, 2006; Patel et al, 2012; Cheung et al, 2013).
Furthermore, additional root canals (Blattner et al, 2010; Neelakantan et al, 2010) and complications, such as vertical root fractures (Fig 8-2), perforations (Figs 8-3 and 8-4), and the nature and position of resorption defects (Figs 8-5 and 8-6) may be readily identified with CBCT (D’Addazio et al, 2011; Shemesh et al, 2011).
Presence of a periapical lesion
It is well established that conventional radiographs may not detect periapical lesions, especially on molar teeth (Cheung et al, 2013; Liang et al, 2014; Venskutonis et al, 2014a). The presence of a periapical radiolucency, not detected on a conventional radiograph, may have an effect on whether an existing root canal treatment should be left alone or re-treated prior to providing a new coronal restoration (Figs 8-2 and 8-3). Davies et al (2015b) assessed the outcome of non-surgical root canal re-treatment radiographically and found a lower number of favourable outcomes with CBCT compared to periapical radiographs. The assessment with CBCT affected the management of the reviewed cases. The ability of CBCT to diagnose periapical disease is further discussed in Chapter 7.
The differential diagnosis of a cyst from a periapical granuloma using CBCT has also been investigated (Simon et al, 2006; Rosenberg et al, 2010; Guo et al, 2013). In a clinical study, Bornstein et al (2015) concluded that CBCT could not reliably differentiate between a granuloma and a cyst. At present, the only reliable diagnosis can be made by in-toto excision and subsequent serial sectioning of the lesion (Nair et al, 1996).
CBCT has been shown to be beneficial in the diagnosis of vertical root fractures (VRFs). Subtle periradicular signs of bone loss indicating a VRF associated with a root-treated tooth (Fig 8-2), which may be challenging to diagnose by other means, may be evident on CBCT examination (Bernades et al, 2009; Wang et al, 2011; Kajan and Taromsari, 2012). The presence or absence of a VRF will have an impact on treatment planning and is described in more detail in Chapter 11.
Quality of existing root canal treatment
Clinical and population studies have shown a strong correlation between the quality of root canal fillings and the outcome of treatment (Liang et al, 2012a; Kirkevang et al, 2014). The quality of the root canal filling is usually assessed by periapical radiographs and is focused on the length and density of the filling (Fig 8-7). A root canal filling that terminates 0 to 2 mm from the radiographic apex has been shown to be more likely to result in a favourable outcome, compared to long or short fillings (European Society of Endodontology, quality guidelines, 2006; Liang et al, 2012a). A void-free root canal filling also results in a higher success rate (Sjögren et al, 1990; Song et al, 2011; Ng et al, 2011).
Liang et al (2012a) demonstrated an overestimation of root canal filling quality by radiographs compared to CBCT. On conventional radiographs when the root filling was flush at the radiographic apex, it was actually long on CBCT. Furthermore, CBCT was also found to be superior to conventional radiography in detecting root filling voids, especially in the buccolingual plane of the root filling (Liang et al, 2012a).
The additional information from a CBCT scan may influence whether the clinician decides to carry outnon-surgical or surgical endodontic re-treatment in refractory cases. In some instances, extraction may be the only viable treatment option (D’Addazio et al, 2011; Shemesh et al, 2011; Eskandarloo et al, 2012).
Missed root canals and anatomical features
Inadequate disinfection of the root canal system may lead to failure of root canal treatment. (Ng et al, 2008). One of the reasons for persistent intra-radicular infection is failure to identify and treat all canals during treatment. The ability of CBCT to detect supplemental canals (Figs 8-8 and 8-9) and anatomic aberrations is well established (Tu et al, 2007, 2009; Abella et al, 2012; Davies et al, 2015a). Nevertheless, incorrect interpretations of images resulting in false positive diagnoses of supplemental canals may occur from scatter caused by filling materials in an adjacent root filled canal (Krithikadatta et al, 2010).
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