Imagine this clinical scenario: in your equine practice, you routinely use computed tomography (CT) to identify apical dental pathology when adult horses present with secondary sinusitis. However, you are aware that some equine vets favour radiography over CT for this purpose. You therefore decide to explore whether there is evidence of greater accuracy of CT or radiography in identifying apical dental pathology.
Four studies that investigated CT and radiographic findings of maxillary apical dental pathology were critically appraised: two observational studies and two retrospective case-controlled studies.
The observational studies reported the accuracy of CT and radiography for diagnosis of maxillary cheek tooth apical infection confirmed by gross and histopathological findings (Liuti et al., 2018a, 2018b). The retrospective case-controlled studies investigated radiographic and CT changes present in maxillary cheek teeth from horses with clinical signs consistent with sinusitis (Bühler et al., 2014; Henninger et al., 2003).
The study by Liuti et al. (2018a) evaluated radiographic and CT findings of 29 horses aged between 3 and 15 years with clinical signs of sinusitis. CT findings consistent with apical dental pathology included heterogeneity of the pulp, changes to pulpar volume, gas within or widening of the periapical periodontium, root clubbing and fragmentation and periapical alveolar bone lysis. Radiographic changes consistent with apical dental pathology included periapical sclerosis and apical clubbing. Histopathological evaluation was performed on the 32 teeth removed from these horses based on the CT findings. The authors found that 100 percent (32/32) of teeth with CT findings consistent with apical dental pathology had histopathological evidence of apical dental pathology. One histologically healthy tooth had abnormal CT findings. In contrast, radiographic abnormalities were detected in only 53 percent (17/32) of teeth.
Limitations of the study included, but were not limited to, the fact that study design led to gold standard histopathological evidence of apical dental pathology, as tooth removal was predetermined due to abnormal CT findings; the number of abnormal teeth present and missed by CT is unknown; poor evidence of the duration of infection or clinical signs; the small sample size; and the lack of a control sinusitis population. In addition, the criteria of radiographic features considered consistent with apical dental pathology were not specified beforehand but were agreed by consensus of highly indicative features rather than independent characteristics.
The authors found that 100 percent (32/32) of teeth with CT findings consistent with apical dental pathology had histopathological evidence of apical dental pathology […] In contrast, radiographic abnormalities were detected in only 53 percent (17/32) of teeth
The second study by Liuti et al. (2018b) used a similar study design to evaluate cheek teeth from 54 cadavers with unknown clinical histories. Ninety-three percent (28/30) of teeth were found to have apical abnormalities. Ninety-six percent (27/28) of teeth with histologically identified apical pathology were found to have had CT changes consistent with apical disease, whereas radiography identified abnormalities in 50 percent (14/28) of teeth.
In terms of limitations, CT imaging produced one false negative of apical disease; no previous history of the horses was provided; the observers’ image evaluation was not independent; and teeth were initially screened as apically infected by imaging and/or clinical examination, before being removed for histopathological evaluation.
The retrospective case-controlled study by Bühler et al. (2014) investigated horses aged between 4 and 20 years scanned with CT. The authors found 96 percent (27/28) of horses with an inconclusive radiographic evaluation had CT changes of apical dental pathology. Three or more of the following CT changes were considered indicative of apical dental pathology: clubbing of the tooth root, widening of the periodontal space, nondetectable lamina dura, periapical sclerosis and changes within the pulp cavity (increased pulp horn volume, irregular margination and heterogenous density). However, the study did not specify which radiographic features were initially examined, and CT was only undertaken in horses with inconclusive changes of apical dental pathology on radiographic evaluation. Further, horses with negative radiographs were excluded from the study, therefore the comparative effectiveness of CT in these cases is unknown.
The final study, by Henninger et al. (2003), investigated 18 horses aged between 1.8 and 18.1 years. The authors found CT changes consistent with apical dental pathology in 89 percent (16/18) of horses that presented for evaluation of sinusitis, with only 28 percent (5/18) of horses showing radiographic evidence of apical infection. The limitations of this older study were the less clearly defined CT criteria for the presence of apical dental pathology and the small sample size. There was no comparison between radiography and CT, nor a definition of criteria for radiographic apical changes. Further, it was not stated whether the same teeth were imaged radiographically and with CT nor how many people reviewed the images.
In all four papers investigating CT and radiographic evaluation of apical dental pathology, CT identified lesions in horses without conclusive radiographic evidence of pathological changes consistent with apical dental disease. While variation existed in reported CT changes associated with apical dental pathology, three out of four papers reported a higher sensitivity of CT to detect pathology compared with radiography. The fourth paper did not directly compare the sensitivity of CT and radiography in detecting pathology but found that CT allowed for a more confident diagnosis than radiography. The literature therefore supports the use of CT imaging in the diagnosis of apical dental pathology in horses with signs of sinusitis as being more sensitive than radiography.
It should be noted that the true relative accuracy of CT and radiography were not determined, as false negatives were not included in several studies. However, within the evidence, the implication is that if appropriate radiographic changes were identified, these horses did have apical dental changes, so from a cost perspective it would be reasonable to radiograph first and then perform a CT if radiographic changes were unremarkable or equivocal.
While variation existed in reported CT changes associated with apical dental pathology, three out of four papers reported a higher sensitivity of CT to detect pathology compared with radiography
Importantly, Bühler et al. (2014) found individual CT abnormalities other than clubbing of the root in dental apices of horses without clinical signs of sinusitis, and loss of lamina dura in 76 percent (1,338/1,764) of tooth roots examined, with 555 roots being from the 21 horses without clinical signs of dental disease.
Likewise, infundibular changes as a solitary CT feature were not significantly associated with other CT signs of apical infection. Liuti et al. (2018a) found one tooth containing gas pockets in the apical aspect of one pulp and adjacent periodontal space where no pathological changes were found following its extraction. It is therefore recommended that in cases where individual CT changes of loss of lamina dura, infundibular changes and gas pockets within the pulp are identified, additional pathological changes should be identified to meet the criteria of dental apical pathology. CT appears to have a low rate of false positives when appropriate criteria for interpretation of the CT are used. No evidence is available on CT false negatives so the true accuracy of CT in the diagnosis of equine sinusitis secondary to dental disease remains unknown.
The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise; patient’s circumstances and owner’s values; country, location or clinic where you work; the individual case in front of you; the availability of therapies and resources.
Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.