Computed tomographic features of apical infection of equine maxillary cheek teeth: A retrospective study of 49 horses

Micro-CT and histological examination of accessory canals in 34 equine cheek teeth

Accessory canals and apical deltas have been extensively studied in human dentistry. Their clinical role as a difficult to clean reservoir for bacteria during endodontic treatments has been well described. Many papers describe in detail the pulp anatomy of equine dentition but little attention has been given to their apical ramifications. The goal of this paper is to describe the presence and anatomy of these accessory canals and apical deltas in healthy equine cheek teeth and discuss their possible relevance in the light of equine endodontics. To accomplish this, 15 maxillary and 19 mandibular healthy cheek teeth were collected ranging from Triadan 06 s to 11 s with eruption ages from 4 to 9 years. Their root anatomy was documented in detail based on micro computed tomography images. A subset of 3 teeth also underwent histological examination. Accessory canals were found in all but two teeth examined. Up to 44 accessory canals per tooth have been found with locations ranging from the root furcation down to the apex of the root and with highly variable diameters. Apical deltas in different stages of development were found in 84% of the roots. The presence of accessory canals identified on microCT images could be confirmed using histological examination although some of them were obliterated by reparative dentin. Accessory canals can be found in most equine cheek teeth and add complexity to their endodontic anatomy. This could have important implications for their treatment in case of pulp pathology. In humans, failure to remove bacterial biofilm from such canals has been associated with failure of endodontic treatment. Research on diseased equine teeth is required to gain a better understanding of their clinical relevance in horses.

The Epidemiology of Infundibular Caries in Donkeys in Inner Mongolia Autonomous Region of China and Associated Risk Factors

Infundibular caries (IC) affects donkeys of all ages and causes pain, difficulty in mastication and weight loss. The study aimed to determine the epidemiology of IC in donkeys and examine the potential risk factors associated with the disease development. A total of 2118 donkeys in Inner Mongolia were sampled. The first section of the survey was performed by veterinarians and included the oral health of the donkeys. A survey on the donkey's signalment, diet, and husbandry was also conducted. The risk factors associated with IC were assessed using multivariable logistic regression analysis. Univariate analysis of 11 variables assessed revealed that only four factors, including age, type of forage, pasture time and water source, increased the risk of IC. The findings of this study enhance our knowledge of the management and prevention of IC in donkeys.

The Role of Computed Tomography in Imaging Non-neurologic Disorders of the Head in Equine Patients

Computed tomography (CT) imaging of the head in equine patients is now commonly performed as CT scanners are more readily available. Head CT has proven valuable in evaluating spatially complex anatomic structures, where radiographic superimposition, or restricted access via endoscopy or ultrasound, limit complete evaluation of the disease process. Head CT has been demonstrated to be incredibly valuable in the evaluation of dental and paranasal sinus disease, disease of the hyoid apparatus and ear, and in evaluation of skull trauma. CT is an excellent modality for assessment of both osseous and soft tissue structures; however, evaluation of complex vascular anatomy and determination of tissue viability is limited without the use of contrast agents. Therefore, various contrast agent protocols including intravenous and intraarterial iodinated contrast administration techniques have been established. CT also has limitations in the evaluation of brain and spinal cord disease, for which magnetic resonance imaging (MRI) has major advantages. Head CT images are most commonly evaluated in transverse planes. However, standard multiplanar reconstructions of the head including dorsal and parasagittal planes improve the understanding of spatially complex disease processes. These reconstructions can be crucial for accurate identification of diseased teeth and determination of the extent and severity of osseous and paranasal sinus disease. Head CT examinations are becoming an increasingly important diagnostic tool in the evaluation of horses with head disorders, and CT imaging findings are an important aspect in the clinical decision-making process. The following review discusses the indications, benefits, and technical considerations for the use of computed tomography (CT) in evaluating non-neurologic head pathologies in equine patients.

The facultative human oral pathogen Prevotella histicola in equine cheek tooth apical/ periapical infection: a case report

BACKGROUND

Prevotella histicola is a facultative oral pathogen that under certain conditions causes pathologies such as caries and periodontitis in humans. Prevotella spp. also colonize the oral cavity of horses and can cause disease, but P. histicola has not yet been identified.

CASE PRESENTATION

A 12-year-old Tinker mare was referred to the clinic for persistent, malodorous purulent nasal discharge and quidding. Conservative antibiotic (penicillin), antiphlogistic (meloxicam), and mucolytic (dembrexine-hydrochloride) treatment prior to referral was unsuccessful and symptoms worsened. Oral examination, radiography, sino-/ rhinoscopy, and standing computed tomography revealed severe apical/ periapical infection of the upper cheek tooth 209 with accompanying unilateral sinonasal inflammation and conchal necrosis. The tooth exhibited extensive subocclusal mesial infundibular cemental hypoplasia and caries, and an occlusal fissure fracture. After mechanical debridement and thermoplastic resin filling of the spacious subocclusal carious infundibular lesion, the tooth was extracted intraorally. The sinusitis and conchal necrosis were treated transendoscopically. Selective bacteriological swab cultures of affected tooth roots and subsequent matrix-assisted laser desorption ionization-time of flight mass spectrometry showed an infection with the obligate anaerobic, Gram-negative bacterium P. histicola. Surgical intervention and adapted antibiotic therapy led to normal healing without complications.

CONCLUSIONS

This study provides the first documented case of dental infection in a horse caused by P. histicola at once indicating necessity of more sufficient microbiological diagnostics and targeted antibiotic treatment in equine dental practice. This finding is also conducive to understand species-specific Prevotella diversity and cross-species distribution.

A computed tomographic study of endodontic and apical changes in 81 equine cheek teeth with sagittal fractures

BACKGROUND

Sagittal fractures of equine cheek teeth are commonly observed during oral examination. There are few reports on the apical and endodontic pathology associated with such fractures seen during computed tomographic (CT) examination.

OBJECTIVES

This study aimed to document the prevalence of CT changes indicative of apical disease in equine cheek teeth, which have suffered a sagittal fracture involving the clinical ± reserve crown.

STUDY DESIGN

This study is a retrospective case series.

METHODS

CT examinations of equine heads with sagittal fractures of cheek teeth present were reviewed: 81 teeth from 49 horses were identified to have a sagittal cheek tooth fracture. The images were evaluated for apical pathology including gas (in the endodontic system and periapically), widened periodontal space, periapical sclerosis, apical clubbing, cementoma/hypercementosis, lamina dura loss, associated sinusitis and sinus mucosal swelling. An apical infection grading system was created to give each tooth a score. Hounsfield units were used to measure the density of the endodontic, apical and periapical regions. The fracture length ratio was recorded. Statistical analysis was performed using a generalised estimating equation to evaluate predictors of apical infection and associations between clinical signs and CT abnormalities.

RESULTS

Eighty-seven sagittal fractures (56 buccal, 17 palatal/lingual and 14 midline) from 81 teeth were recorded (74 maxillary and 7 mandibular). Apical infection was diagnosed in 73% (37/51, P = .05) of buccal, 55% (6/11, P = .07) of palatal/lingual, 100% (13/13) of midline, 100% (6/6) of multiple fractures and 96% (23/24, P = .008) of fractures involving infundibula. There was no significant relationship between apical infection and the presence of clinical signs associated with dental pathology (P = .4). There was no significant association between fracture length ratio and apical infection (P = 1.0). Midline sagittal fractures were significantly associated with sinusitis when compared with all other maxillary fractures (odds ratio [OR] 5.92, 95% confidence interval [CI] 1.67-20.83, P = .006). Loss of the lamina dura was not significantly associated with apical infection (P = .5).

MAIN LIMITATIONS

There is a maxillary cheek tooth bias in the data set and the subjective grading system.

CONCLUSIONS

A large proportion of fractured cheek teeth have evidence of apical infection on CT examination and therefore warrant treatment.

Computed Tomographic Assessment of Individual Paranasal Sinus Compartment and Nasal Conchal Bulla Involvement in 300 Cases of Equine Sinonasal Disease

Background: Computed tomographic (CT) imaging has allowed new anatomical studies and detailed clinical imaging of the complex, overlapping equine sinonasal structures. Despite the widespread use of CT, no study has specifically identified which compartments are most commonly affected with sinus disorders. CT has also shown the presence of intercurrent, ipsilateral nasal disorders, especially infection of the nasal conchal bullae (NCB) in many cases of sinus disease, but the frequency of intercurrent NCB infections has not been reported.

Objectives: To identify which sinus compartments are most commonly affected in horses with clinical sinus disorders and to record the prevalence of NCB involvement in such cases.

Study Design: Retrospective examination of CT images of horses with confirmed unilateral sinus disease.

Methods: The CT images of 300 horses, from three different equine hospitals with clinically confirmed sinus disease [mainly dental (53%) and primary sinusitis (25.7%)] were retrospectively examined to determine which sinus compartments and NCBs were affected.

Results: The rostral, more dependent sinus compartments were most commonly involved, i.e., the rostral maxillary sinus in 284/300 (94.7% affected) and the ventral conchal sinus (87% affected). The caudal maxillary sinus (65.3%), dorsal conchal sinus (52.7%), frontal sinus (26%), ethmoidal sinus (32%) and sphenopalatine sinus (28.7%) were less commonly affected. There was infection or destruction of the ipsilateral NCBs in 56% of horses with sinus disorders, including the ventral NCBs in 42.3%, dorsal NCBs in 29% and both NCBs in 18% of cases.

Main Limitations: The horses with sinonasal disease that underwent head CT imaging include more problematic cases and horses of high value, rather than the general horse population.

Conclusions: The more dependant (i.e., the RMS and VCS) sinus compartments are most commonly involved in sinus disorders, with the RMS involved in nearly every case. The more dorsally located sinuses (i.e., caudal group) are less commonly involved. Many horses with sinus disease also have disorders of their nasal conchal bullae and so the term sinonasal disease seems appropriate for these disorders.

Equine Imaging: Computed Tomography Interpretation

Computed tomography (CT) has revolutionized the veterinarian's ability to image the equine skull and led to improved diagnostic accuracy and clarity for surgical planning. The increased cost for this evaluation is offset by more accurate diagnosis and targeted therapy. As novel technology is developed that allows for increased availability of equine head, the price will continue to decrease and more examinations will be performed. New skills are needed for the veterinarian to accurately interpret this modality. This article reviews the normal CT appearance of the equine skull and presents examples and key features of several common diseases.

A Computed Tomographic Assessment of Osteitis of Sinus Bony Structures in Horses With Sinonasal Disorders

Background: Computed tomographic (CT) imaging has shown some horses with sinonasal diseases to have changes in their sinus bony structures. Scintigraphic and clinical evidence of sinus osteitis have also been reported. However, no study has objectively examined for the presence and degree of osteitis in equine sinonasal disease.

Objectives: To assess for the presence and extent of osteitis of sinus-related bony structures by examination of CT images of horses with clinically and sinoscopically confirmed unilateral sinonasal disease.

Study Design: Retrospective examination of CT images of horses with confirmed, mainly chronic (>2 month duration) unilateral sinus disease of different etiologies.

Methods: Bone thickness at designated sites of the maxillary bone (n = 3), frontal bone (n = 1), infraorbital canal (n = 2), and bony nasolacrimal duct (n = 1) were measured, as were the maximal diameters of the infraorbital canal and the bony nasolacrimal duct on both affected and control sides. Maxillary bone density (in Hounsfield Units) was also assessed bilaterally. Bone thickness was compared between affected and controlled sides using paired statistical tests.

Results: Bone was significantly thicker in the affected sinuses compared to the control sides at the three maxillary bone sites (all, P < 0.001) and at both infraorbital bone sites (both, P < 0.001), but not at the two most dorsal sites examined, i.e. frontal bone (P = 0.188) and bony nasolacrimal duct (P = −0.260) sites. Infraorbital canal and bony nasolacrimal duct diameters were significantly wider in the affected as compared to the control sides (P < 0.001 and P = 0.002, respectively). Maxillary bone density did not differ significantly between the affected (mean = 1,075 HU, SD = 230.01) and control (mean = 1,100, SD = 200.71) sides (t₍₅₈₎ = −1.03, P = 0.306).

Main Limitations: Possible variation in selecting measurement sites. Variation in the severity and chronicity of sinonasal disease between horses.

Conclusions: Osteitis and enlargement of paranasal bony structures commonly occurs in horses with sinonasal disease and can explain the clinical presence of ipsilateral diffuse soft tissue facial swelling, epiphora, and scintigraphic evidence of bone inflammation in sinonasal disease.

Assessment of clinical and computed tomographic findings for association with the outcome of intraoral cheek tooth extraction in horses and ponies

OBJECTIVE

To describe clinical and CT findings for horses and ponies undergoing intraoral cheek tooth extraction and assess potential associations between these features and outcome of the procedure.

ANIMALS

74 horses and 7 ponies.

PROCEDURES

Medical records were searched to identify horses and ponies that underwent CT and intraoral extraction of ≥ 1 cheek tooth with standing sedation. Signalment and clinical variables were recorded, and CT scans were reviewed. Anatomic location and measurements of affected teeth; abnormalities of the periodontium, pulp, infundibula, roots, and tooth shape; fracture presence and type; presence of sinusitis; and affected sinus cavities were assessed by a surgeon and a radiologist. Intraoral extraction outcome was recorded as successful (complete removal of the tooth in 1 intraoral extraction procedure) or unsuccessful. Univariable and multivariable logistic regression analyses were performed to assess associations between clinical or CT findings and outcome.

RESULTS

89 cheek teeth (80 maxillary and 9 mandibular) were included in the analyses. Sixty of 89 (67%) cheek teeth were extracted successfully (56/80 [70%] maxillary and 4/9 [44%] mandibular cheek teeth). Only presence of a simple fracture (vs no fracture) was associated with outcome on multivariable regression analysis; odds of successful intraoral extraction were significantly lower when this feature was present.

CONCLUSIONS AND CLINICAL RELEVANCE

Most extractions of cheek teeth in the study sample were successful, and results may be useful for practitioners in refining cheek tooth extraction plans for horses and ponies. Further studies are required to assess whether specific CT findings can be used to predict the outcome of intraoral extraction in equids.

Computed tomography characteristics of equine paranasal sinus cysts

BACKGROUND

Computed tomography (CT) is commonly used to investigate equine paranasal sinus disease, however, only limited information is available in the literature about the detailed CT appearance of equine paranasal sinus cysts.

OBJECTIVES

To investigate if paranasal sinus cysts have specific characteristics in CT images that allow differentiation from other sinus diseases.

STUDY DESIGN

Retrospective observational study.

METHODS

Evaluation and comparison of CT studies of eight horses with surgically and/or histopathologically confirmed paranasal sinus cysts and 10 horses with other confirmed paranasal sinus diseases.

RESULTS

A discrete hyperattenuating wall-like structure was detected in the periphery of the sinus lesion in precontrast acquisition in 7/8 horses with paranasal sinus cysts. A similar wall-like structure was detected in 3/10 horses with other sinus diseases, however, in contrast to horses with paranasal sinus cysts, two of these also had hyperattenuating regions within the contents of the sinus lesion. Bone destruction and formation affecting cancellous and cortical bone and dental disease were frequent in horses with paranasal sinus cysts. No significant difference in attenuation values was found when the fluid/soft tissue attenuation contents of lesions in horses with paranasal sinus cysts (mean 28.9 ± SD 9.2 HU) were compared with other sinus diseases when ethmoid haematomas were excluded (30.4 ± 12.9 HU, P = .8).

MAIN LIMITATIONS

Low number of cases.

CONCLUSIONS

Detection of a hyperattenuating cystic wall is a helpful feature for identifying paranasal sinus cysts in CT images of horses. In contrast, measurement of attenuation values of the soft tissue/fluid contents of the sinus lesions was not helpful in identifying paranasal sinus cysts.

A Study on the Potential Role of Occlusal Fissure Fractures in the Etiopathogenesis of Equine Cheek Teeth Apical Infections

Thirty-nine equine cheek teeth diagnosed as having anachoretic apical infections and also having occlusal fissure fractures, but without occlusal pulpar exposure, that had been orally extracted without causing occlusal damage and 10 control teeth were used in this study. The teeth were individually imaged by computed tomography, occlusally stained with methylene blue and visually reexamined, then sectioned subocclusally at 5 mm intervals until the fissure fractures could no longer be detected. A limited histological study was then performed on 7 apically infected and 5 control teeth. Standard computed tomography only detected 1 of 39 fissure fractures. Thirteen of the 39 stained teeth had subocclusal fissure fractures visually identified at approximately 6 mm beneath the surface, and in 9 of these 13 teeth the fissure fractures had deeper staining to a level immediately above or into a pulp horn, indicating a potential route for bacterial pulpitis. However, the current study cannot rule out the possibility that the extraction process, long-term formalin storage, or the processing of teeth may have allowed for deeper staining. Additionally, methylene blue may penetrate dental tissue more readily than bacteria can invade. Further studies on the potential role of fissure fractures in the etiopathogenesis of cheek teeth apical infection are warranted.

Magnetic resonance imaging and computed tomography of equine cheek teeth and adjacent structures: comparative study of image quality in horses in vivo, post-mortem and frozen-thawed

BACKGROUND

The use of cadavers for radiology research methodologies involving subjective image quality evaluation of anatomical criteria is well-documented. The purpose of this method comparison study was to evaluate the image quality of dental and adjacent structures in computed tomography (CT) and high-field (3 T) magnetic resonance (MR) images in cadaveric heads, based on an objective four-point rating scale. Whilst CT is a well-established technique, MR imaging (MRI) is rarely used for equine dental diagnostics. The use of a grading system in this study allowed an objective assessment of CT and MRI advantages in portraying equine cheek teeth. As imaging is commonly performed with cadaveric or frozen and thawed heads for dental research investigations, the second objective was to quantify the impact of the specimens' conditions (in vivo, post-mortem, frozen-thawed) on the image quality in CT and MRI.

RESULTS

The CT and MR images of nine horses, focused on the maxillary premolar 08s and molar 09s, were acquired post-mortem (Group A). Three observers scored the dental and adjacent tissues. Results showed that MR sequences gave an excellent depiction of endo- and periodontal structures, whereas CT produced high-quality images of the hard tooth and bony tissues. Additional CT and MRI was performed in vivo (Group B) and frozen-thawed (Group C) in three of these nine horses to specify the condition of the best specimens for further research. Assessing the impact of the specimens' conditions on image quality, specific soft tissues of the maxillary 08s and 09s including adjacent structures (pulps, mucosa of the maxillary sinuses, periodontal ligament, soft tissue inside the infraorbital canal) were graded in group B and C and analysed for significant differences within CT and MR modalities in comparison to group A. Results showed that MRI scores in vivo were superior to the post-mortem and frozen-thawed condition.

CONCLUSIONS

On comparing the imaging performance of CT and MRI, both techniques show a huge potential for application in equine dentistry. Further studies are needed to assess the clinical suitability of MRI. For further research investigations it must be considered, that the best MR image quality is provided in live horses.

Cone-beam computed tomography of the head in standing equids

Background

Computed tomography in standing horses has revolutionized diagnostic imaging. The O-arm®, a cone beam computed tomography (CBCT) scanner with a gantry opening of 96.5 cm is routinely used for image-guided spine and neurosurgery in humans. The aim of this study is to describe the set-up and first experiences using the O-arm® to achieve CBCT imaging of the head in standing horses.

CT imaging of the predefined region of interest (ROI) was tested on 2 cadaveric heads, concentrating on centering issues within the gantry, as well as determining the number of scans needed per ROI. All horses presented with head-related diseases and subjected to a CBCT examination between February 2015 and November 2016 for CBCT were included. Per scan, a limited field of view, i.e. a cylindrical volume of 21 cm in diameter and 16 cm in height was acquired within 13 s. Depending on the dimensions of the ROI, the minimum number of scans could range from one to six, if the entire equine head is to be examined in an adult horse.

Results

Sixty-eight horses were included, five of which had a follow-up CBCT exam, and two of which were presented twice for two different indications (75 clinical cases). A total number of 449 acquired three-dimensional (3D) scans were recorded for these 75 cases. Two-hundred and forty-two 3D scans (54%) were considered as diagnostic quality. The imaging procedure was generally well tolerated by the sedated, standing equid, and diagnostic studies were performed in 73 out of 75 cases (97.3%). Motion artefacts and inadequate centering of the ROI were the most common reasons for non-diagnostic quality images and repeat scans of the same ROI.

Conclusions

CBCT is a valuable imaging modality for the equine head. Advantages of the O-arm® compared to a conventional multi-slice helical CT for imaging of the head in standing equids include the rapid image acquisition, the gantry’s mobility in all dimensions, and the free movability of the entire imaging unit. Disadvantages include the considerable sensitivity to motion artefact, increased scatter, low soft tissue contrast and the limited dimensions of the field of view.

A Computed Tomographic and Pathological Study of Equine Cheek Teeth Infundibulae Extracted From Asymptomatic Horses. Part 2: MicroCT, Gross, and Histological Findings

Background: Equine maxillary cheek teeth infundibulae are frequently affected by developmental and acquired disorders, but the imaging, gross, and histological features of normal and abnormal infundibulae remain incompletely understood. Objective: To perform MicroCT, gross examination, and histology on sectioned teeth and compare the imaging and anatomical findings. Study design: Ex vivo original study. Methods: Eight maxillary cheek teeth of different ages and with varying grades of unilateral (n = 5) or bilateral (n = 3) occlusal infundibular caries were extracted from equine heads obtained from an abattoir. The teeth were imaged by MicroCT, then transversely sectioned and grossly and histologically examined, with the imaging and gross and histological anatomical findings examined and compared. Results: Fifteen infundibulae, including two without occlusal caries had subocclusal cemental hypoplasia or caries. One infundibulum without occlusal caries had no subocclusal cemental defects. Histologically, hypoplastic cemental areas consisted of irregularly-shaped, wide central channels, with multiple, large, cylindrical side-branches that extended peripherally to a variable extent. Cementum with extensive, wide, empty channels, and cementum with a more irregular moth-eaten appearance had dark or eroded gross appearance and a low HU on CT. Some infundibulae had cement-free areas that only contained fragments of collagen-like material, especially at their apical aspects (apical cemental hypoplasia). Carious subocclusal areas had connections with the occlusal surface and had disrupted cemental architecture, including of their central vascular channel that, along with their side branches, contained degraded food, and cemental debris. Main Limitations: No clinical histories or accurate ages were available for these eight teeth. Conclusions: Hypoplastic cemental lesions, including at central linear and apical sites, histologically contain areas with multiple wide-branched, cylindrical channels or even areas of total cement hypoplasia visible on gross sections When such cemental defects contact the occlusal surface due to normal wear, food impaction, and caries can ensue.

A Computed Tomographic (CT) and Pathological Study of Equine Cheek Teeth Infundibulae Extracted From Asymptomatic Horses. Part 1: Prevalence, Type and Location of Infundibular Lesions on CT Imaging

Background: Equine maxillary cheek teeth infundibulae are frequently affected by developmental and acquired disorders, but the computed tomographic (CT) imaging features of normal and abnormal infundibulae remain incompletely understood. Objective: To examine infundibulae with various grades of occlusal caries and control teeth by standard CT in order to assess the prevalence, type and location of subocclusal infundibular lesions present. Study design: Ex vivo original study. Methods: One hundred maxillary cheek teeth, including 82 with, and 18 without infundibular occlusal caries, were extracted from horses of different ages and imaged by standard CT; 8 teeth were also imaged by MicroCT. Images were later assessed by Osirix® and the prevalence, characteristics and sites of infundibular lesions were assessed. Results: Teeth with shorter infundibulae (i.e., Triadan 09 position and older teeth) were more likely to have occlusal caries, as were the rostral infundibulae. Subocclusal developmental infundibular lesions, including cemental hypoplasia and caries, were present in 72% of infundibulae without occlusal caries. CT imaging confirmed two main patterns of developmental cemental hypoplasia, i.e., apical cemental hypoplasia usually involving the full width of the apical aspect of the infundibulum and central linear hypoplasia involving the central aspect of the infundibulum over most of its length, and combinations of these types. These developmental lesions could later be affected by (acquired) infundibular caries once occlusally exposed due to normal wear. Some "normal-sized" (i.e., circa 1 mm diameter) occlusal central vascular channels expanded subocclusally to the dimensions of central linear defects. Main Limitations: No clinical histories or accurate ages were available for these teeth. Conclusions: Hypoplastic cemental lesions, including at central linear, and apical sites, are common even in clinically normal maxillary cheek teeth infundibulae and caries can occur when these lesions contact the occlusal surface. Central linear defects are not always clearly distinguishable from "normal" central vascular channels.

Computed tomographic description of the highly variable imaging features of equine oromaxillary sinus and oronasal fistulae

Oronasal and oromaxillary sinus fistulae are well-documented complications following removal or loss of a maxillary cheek tooth. Diagnosis is currently based on a combination of oral examination, videoendoscopy, radiography, and computed tomography (CT). The objective of this retrospective, case series study was to describe the CT characteristics of confirmed oronasal and oromaxillary sinus fistulae in a group of horses. Inclusion criteria were a head CT acquired at the authors' hospital during the period of 2012-2017, a CT diagnosis of oronasal or oromaxillary sinus fistulae, and a confirmed diagnosis based on a method other than CT. Signalment, clinical findings, oral examination findings, presence of a confirmed fistula, and method for confirmation of the diagnosis were recorded. A veterinary radiologist reviewed CT studies for all included horses and recorded characteristics of the fistulae. Seventeen horses were sampled. Fourteen oromaxillary sinus fistulae and three oronasal fistulae were identified. All fistulae appeared as variably sized focal defects in the alveolar bone. Defects frequently contained a linear tract of heterogeneous material interspersed with gas bubbles, considered consistent with food. Computed tomographic attenuation of the material (Hounsfield units, HU) varied widely within and between cases. In 16 of 17 cases, there was evidence of concurrent dental disease in addition to the fistulae. Although the gold standard diagnostic test remains identification of feed material within the sinus or nasal passages, findings from the current study support the use of CT as an adjunctive diagnostic test for assessing the extent of involvement and presurgical planning.

A Comparison of Computed Tomographic, Radiographic, Gross and Histological, Dental, and Alveolar Findings in 30 Abnormal Cheek Teeth from Equine Cadavers

Background

Equine cheek teeth disorders, especially pulpar/apical infections, can have very serious consequences due to the frequent extension of infection to the supporting bones and/or adjacent paranasal sinuses. Limited studies have assessed the accuracy of computed tomographic (CT) imaging in the diagnosis of these disorders, and no study has directly compared imaging and pathological findings of the alveoli of diseased equine cheek teeth.

Objective

To validate the accuracy of CT and radiographic imaging of cheek teeth disorders by comparing CT and radiographic imaging, gross and histological findings in abnormal cheek teeth and their alveoli extracted from equine cadaver heads.

Study design

Ex vivo original study.

Methods

Fifty-four cadaver heads from horses with unknown histories that had died or been euthanized on humane grounds obtained from a rendering plant had radiography, CT imaging, and gross pathological examinations performed. Based on imaging and gross examination findings, 30 abnormal cheek teeth (26 maxillary and 4 mandibular) identified in 26 heads were extracted along with their dental alveoli where possible, and further CT imaging, gross, and histological examinations were performed. Eight maxillary cheek teeth (including four with attached alveolar bone) from these heads, that were normal on gross and CT examinations, were used as controls.

Results

Gross pathological and histological examinations indicated that 28/30 teeth, including two supernumerary teeth, had pulpar/apical infection, including pulpar and apical changes. A further supernumerary and a dysplastic tooth were also identified. Abnormal calcified tissue architecture was present in all three supernumerary and in the dysplastic tooth. CT imaging strongly indicated the presence of pulpar/apical infection in 27 of the 28 (96.4%) pulpar/apically infected teeth, including the presence of intrapulpar gas (N = 19/28), apical clubbing (N = 20), periapical halo (N = 4), root lysis or fragmentation (N = 7), and periapical gas (N = 2). Also present were alveolar bone sclerosis (N = 20), alveolar bone thickening (N = 3), and lytic/erosive changes (N = 8). Radiographic abnormalities strongly indicative of pulpar/apical infection including periapical sclerosis (N = 8/28) and apical clubbing (N = 14/28) were found in 14/28 (50%) of apically infected teeth. Histological changes were present in alveolar bone of all 21 cases of apical infection where alveolus remained attached to the tooth and was marked in 16 cases, all which had CT alveolar changes. Histological changes included disruption of the normal trabecular pattern, increased osteoclastic activity, and the presence of islands of bone with a scalloped profile within the thickened attached periodontal ligament. No gross pathological or histological changes were present in the eight control teeth or their alveoli (N = 4).

Main limitations

No history or breed-related information was available on these cases.

Conclusion

There was a 96.4% correlation between a CT diagnosis and confirmative pathological findings in 28 apically infected teeth confirming the accuracy of CT imaging in diagnosing equine pulpar/apical infections. There was also excellent correlation between CT and histological alveolar bone findings.

Computed tomographic assessment of equine maxillary cheek teeth anatomical relationships, and paranasal sinus volumes

Disorders affecting the equine maxillary cheek teeth and paranasal sinuses are relatively common, but limited objective information is available on the dimensions and relationships of these structures in horses of different ages. The aims of this study were to assess age-related changes in the positioning and anatomical relationships of the individual maxillary cheek teeth with the infraorbital canal and maxillary septum and the volumes of the individual sinus compartments. CT and gross examination were performed on 60 normal equine cadaver heads that were aged by their dentition. The intrasinus position of cheek teeth, length of reserve crowns, relationship to the infraorbital canal and measurements of rostral drift and sinus compartment volumes were assessed from CT images. The findings included that Triadan 10 alveoli lay fully or partially in the rostral maxillary sinus (RMS) in 60% of cases. The infraorbital canal lay directly on the medial aspect of the alveolar apex in younger horses. The Triadan 11'sclinical crowns and apices drifted a mean of 2.48 and 2.83 cm more rostral to the orbit, respectively, in the >15 years old vs the <6 years old age group. The mean volumes of sinus compartments ranged from 175 cm³ for the caudal maxillary sinus (CMS) to 4 cm³ for the ethmoidal sinus (ES). This information should be of value in the diagnosis and treatment of equine dental and sinus disorders and as reference values for further studies.

Comparison of computed tomography and high-field (3.0 T) magnetic resonance imaging of age-related variances in selected equine maxillary cheek teeth and adjacent tissues

Background

Modern imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI) have the advantage of producing images without superimposition. Whilst CT is a well-established technique for dental diagnostics, MRI examinations are rarely used for the evaluation of dental diseases in horses. Regarding equine endodontic therapies which are increasingly implemented, MRI could help to portray changes of the periodontal ligament and display gross pulpar anatomy. Knowledge of age-related changes is essential for diagnosis, as cheek teeth and surrounding structures alter with increasing age. The aim of the present study was to highlight the advantages of CT and MRI regarding age-related changes in selected equine cheek teeth and their adjacent structures.

Results

The CT and MRI appearances of the maxillary 08 s and 09 s and adjacent structures were described by evaluation of post-mortem examinations of nine horses of different ages (Group A: <6 years, B: 6–15 years, C: ≥16 years). Most of the tissues selected were imaged accurately with MRI and CT. Magnetic resonance imaging gives an excellent depiction of soft endo- and periodontal units, and CT of hard dental and bony tissues. Negative correlation between dental age and pulpar sizes was found: 71.3% of the changes in pulp dimensions can be explained by teeth aging. Pulpar sizes ranged from 14.3 to 1.3 mm and were significantly smaller in older horses (p < 0.05). A common pulp chamber was present in 33% of the teeth with a mean dental age of 2.25 years. Ninety-four percent of the 08 and 09 alveoli of all groups were in direct contact with the maxillary sinus. An age-related regression was found (R² = 0.88) for the distance between alveoli and the infraorbital canal.

Conclusions

The present study provides information about the dental and periodontal age-related morphology and its visibility using different imaging techniques. These results aid in evaluating diagnostic images and in deciding which is the superior imaging modality for clinical cases.

Epidemiological survey on equine cheek tooth infundibular caries in the United Kingdom

Infundibular caries (IC) is an important equine dental disorder that can cause premature wear, fractures and apical infection of affected maxillary cheek teeth. No accurate prevalence values for IC are available for UK horses. The feeding of high levels of concentrates is believed to increase its prevalence, but no objective information is available on such possible environmental risk factors. The aims of the study were to document the prevalence of IC in UK horses, assess its distribution and severity between infundibulae and teeth in affected horses and examine for potential risk factors for its development. Using well-defined criteria for grading and recording IC, 25 experienced personnel across the UK completed a questionnaire on their patients. Frequency of IC occurrence was compared between individual teeth and infundibulae using McNemar's tests. Potential risk factors for IC presence were examined using univariable logistic regression prior to building a multilevel multivariable model. Of 706 horses examined, 45.5 per cent had IC, which was most commonly present and most severe in the Triadan 09s (>10>08>06>07>11), with 13.4 per cent of all rostral and 10 per cent of all caudal infundibulae affected. The prevalence of IC was significantly associated with increasing age; the lowest IC prevalence was found in South West England.