Comparison of radiography and scintigraphy in the diagnosis of dental disorders in the horse

Abstract

Summary Scintigraphy, with 99mTechnetium methylenediphosphonate (99mTc‐MDP) and 99mTc‐labelled leucocytes, was compared to radiography in the diagnosis of dental disease in the horse in a prospective case‐controlled study, comprising 30 horses with clinical signs of dental disease and 30 control horses. In each case, right and left lateral, ventral and dorsal soft tissue and bone phase scintigraphic images were obtained after i.v. injection of 1 GBq/100 kg bwt 99mTc‐MDP, using a gamma camera. The same views were acquired in 10 horses with clinical signs of dental disease and 12 control horses after injection of 99mTc‐labelled leucocytes. Standard radiographic projections of the paranasal sinuses and of the apices of the maxillary and mandibular teeth were obtained. The scintigraphs and radiographs were assessed subjectively by 2 board‐certified surgeons and one board‐certified radiologist, with extensive experience of equine radiology, from who the clinical history was withheld. Sensitivity, specificity and kappa, as a measure of agreement, were calculated for the different methods. Bone phase images were also scored subjectively on a scale from 0 to 3 on the basis of isotope uptake over the teeth. Regions of interest were defined over the teeth, and normal teeth compared to diseased counterparts. Total scintigraphic counts were related to the age of the animal and to the disease process. Differences in density ratios between left and right teeth were evaluated using the Mann‐Whitney Test. Dental disease was confirmed in 22 horses at surgery or postmortem examination. Horses with dental disease showed a significant increase in scintigraphic activity over the affected tooth compared to the contralateral tooth, with a typical pattern for different diseases. The sensitivity of scintigraphy with 99mTc‐MDP proved to be excellent (95.5%), whereas the specificity was moderate (86.4%). In contrast, radiography had excellent specificity (95.0%) and a low sensitivity (51.5%). The greatest sensitivity and specificity were achieved by evaluating radiographs and scintigrams together. The objective scintigraphic density ratios were found to be significantly different between diseased and control horses. The results of this study suggest that, if a density ratio of 1.5 or greater between a suspected diseased tooth and its contralateral number is regarded as abnormal, only 1% false positive diagnoses and 20% false negative diagnoses will occur. In contrast, scintigraphy with 99mTc‐labelled leucocytes was not very successful, due to the lack of anatomical detail provided by this technique, which made identification of the diseased tooth impossible. Accurate radiographic interpretation of dental disease presents difficulties, both in terms of missed diagnoses and mistaken diagnoses. Scintigraphy complements radiographic examination of dental structures by providing information important for accurate diagnosis and is, therefore, conceived to be essential for selection of the appropriate treatment for dental disease.

Diagnostic of equine cheek tooth diseases with magnetic resonance imaging

“…In vielen Fällen ist der erkrankte Zahn schwer zu identifizieren, weil die klinischen Zeichen auf eine Sinusitis beschränkt sind. Die röntgenologische Diagnostik ist schwierig und weist nur eine geringe Sensitivität auf (Weller et al 2001). Lediglich eine Sklerose und die Bildung eines periapikalen Halo sind ein zuverlässiges Zeichen für eine Infektion (Townsend et al 2011).…”

Oral endoscopy as an aid to diagnosis of equine cheek tooth infections in the absence of gross oral pathological changes: 17 cases

“…Correct identification of the diseased tooth often depends on the accumulation of a body of evidence using several diagnostic aids, although diagnosis has traditionally relied heavily upon the radiographic imaging of the apical and alveolar portions of the cheek tooth arcade of interest. The interpretation of radiographic images of the equine head has, for some time, been considered difficult and somewhat inaccurate (Gibbs and Lane 1987) prompting utilisation of other imaging modalities, such as scintigraphy (Weller et al 2001) and computed tomography (Tietje et al 1996;Henninger et al 2003).…”

“…Radiography continues to play an important role in the investigation of suspected dental sepsis in horses, although the sensitivity and specificity of equine dental radiography for infection has been shown to be limited (Gibbs and Lane 1987;Weller et al 2001). In recent years, the quality of imaging in equine practice has been boosted by the use of computed radiography, but correct interpretation of radiographic images remains highly dependent upon the experience of the viewing clinician and does not always permit a definitive diagnosis (Dixon and Dacre 2005).…”

“…Nasal endoscopy (Tremaine and Dixon 2001), sinoscopy (Easley 2005), gamma scintigraphy (Weller et al 2001) and computed tomography (Henninger et al 2003) all have a role in the diagnostic armoury of the examining clinician depending on the nature of the infection. Although external features of apical cheek tooth infection (facial/mandibular swelling or fistulation, nasal discharge from sinus empyema) are well known, very few references to the examination of dental tissues within the oral cavity as an aid to correct identification of diseased teeth exist (Tremaine and Lane 2005).…”

Clinical and microbiological aspects of periodontal disease in horses in South-East Queensland, Australia

“…Some areas, such the apices, reserve crowns and periodontal structures are impossible to examine in the horse even with the aid of sophisticated instrumentations, such full mouth speculums, dental mirrors, extreme bright dental lights, retractors and endoscopes. Radiography is considered to be an accurate alternative diagnostic technique for assessment of these hard to examine areas of equine head, especially using advanced imaging techniques, such as CT, standing CT (Porter & Werpy 2014), MRI (Tucker & Farrell 2001), nuclear scintigraphy (Weller 2001;Archer 2003) and computerized 3D reconstructed imaging (Brinkschulte et al 2014). However, the expense and risks associated with general anaesthesia necessary for CT and MRI will render radiography as the most commonly used ancillary imaging diagnostic technique for equine dental disorders.…”