Clinical findings and treatment of shear mouth in two horses associated with ipsilateral painful dental disease

Shear mouth is a rare and poorly described dental condition observed in horses. This report outlines 2 cases of unilateral shear mouth with ipsilateral painful dental disease. Both cases are young horses diagnosed with idiopathic 409 cheek tooth fractures associated with shear angles on the 100 and 400 cheek teeth rows. Corrective odontoplasty was performed in both cases to correct the cheek tooth occlusal surface angle following exodontia of the diseased molars.     

The prevalence of secondary dentinal lesions in cheek teeth from horses with clinical signs of pulpitis compared to controls

Reasons for performing study: With the advent of detailed oral examination in horses using dental mirrors and rigid endoscopy, secondary dentinal lesions are observed more frequently. More information regarding the association of secondary dentinal defects with apical dental disease would improve the sensitivity of oral examination as a diagnostic aid for pulpitis. Objectives: To assess prevalence and severity of secondary dentinal defects observed on examination of occlusal surfaces of cheek teeth (CT) from horses showing clinical signs of pulpitis compared to asymptomatic controls. Methods: Records from all cases of equine CT exodontia at the University of Bristol over a 4 year period were examined. Case selection criteria included the presence of clinical signs of pulpitis, an intact extracted tooth and availability of a complete history and follow up. Cases where coronal fracture or periodontal pocketing featured were excluded. CT from cadavers with no history of dental disease served as normal controls. Triadan positions and eruption ages of control teeth were matched with those of teeth extracted from cases. CT from selected cases and control teeth were examined occlusally. Secondary dentinal defects were identified and graded. Prevalence of occlusal lesions in CT with pulpitis and controls was compared. Results: From the records of 120 horses where exodontia was performed, 40 cases matched selection criteria. Twenty‐three mandibular and 21 maxillary CT were extracted from cases. The controls consisted of 60 mandibular and 60 maxillary CT from 7 cadaver skulls. Secondary dentinal defects were significantly over‐represented in CT extracted from cases of pulpitis (P<0.001). Of diseased mandibular CT, 56.5% had defects compared to none of the controls. Of diseased maxillary CT, 57% had defects compared with 1.6% of controls. Multiple defective secondary dentinal areas and severe lesions were more prevalent in diseased mandibular CT compared with diseased maxillary CT. Conclusions and practical significance: Careful examination of occlusal secondary dentine is an essential component in investigation of suspected pulpitis in equine CT.     

Occlusal angles of cheek teeth in normal horses and horses with dental disease

The angle between the occlusal surface of the tooth and the horizontal plane of 687 cheek teeth from the skulls of 22 horses without gross dental disorders and 11 horses with dental disorders were measured by using stiff malleable wire as an imprint. Each measurement was repeated five times and the mean angle was recorded. In the normal skulls, the mean occlusal angles of the mandibular cheek teeth ranged from 19.2 degrees at the Triadan 06 position to 30 degrees at the 11 position, and these angles were significantly greater than the occlusal angles of the opposing maxillary cheek teeth (range 12.5 degrees to 18 degrees) at all the positions except the 06. The rostral mandibular cheek teeth had significantly lower occlusal angles than the caudal mandibular cheek teeth, but the converse was true for the maxillary teeth. In the skulls with dental disorders the occlusal angles of the mandibular cheek teeth ranged from 15.6 degrees to 28.5 degrees , and of the maxillary cheek teeth from 9.2 degrees to 16.4 degrees. They were not significantly different from the angles of the teeth from the normal skulls, except at the 06 position, where they were smaller.     

Observations of the cheek tooth occlusal angle in the horse

The angle of occlusion was evaluated in 230 mandibular cheek teeth from 21 horses. There was no significant relationship between horse condition (sedated, anesthetized, dead) and measurement of mean cheek tooth occlusal angle. Cheek tooth occlusal angle was not significantly affected by the position of the tooth in the mandibular arcade or tooth age. The measurement of individual mandibular cheek tooth occlusal angles was predictive for occlusal angle of the entire mouth. Multiple variations of the incisor separation angle technique were predictive of cheek tooth molar occlusal angle for the measured arcade and the entire mouth but was significantly different contralaterally, suggesting that the single tooth method may be preferred. However, despite the limitations of the relatively simple incisor separation angle technique, it may provide the equine veterinary dentist a rapid method of assessing cheek tooth occlusal angle to ensure proper dental floating methods and outcomes.     

The use of oral endoscopy for detection of cheek teeth abnormalities in 300 horses

The main objective of this study was to evaluate an endoscopic examination protocol for routine dental examination in horses. The oral cavities of 300 standing, sedated horses were examined under field and hospital conditions with a rigid endoscope using a standardised technique that included examination of the occlusal, lingual (palatal) and buccal surfaces of all cheek teeth rows. The most common cheek teeth abnormalities detected were sharp enamel edges (present in 96.3% of horses), focal overgrowths (64.3%), fissure fractures (54.3%), diastemata (24.3%) and infundibular hypoplasia/caries (48.3%). Rigid endoscopy of the equine oral cavity was found to be a safe non-invasive diagnostic technique that appeared to be superior to clinical oral examination for detecting subtle cheek teeth changes.     

Repulsion of maxillary and mandibular cheek teeth in standing horses

Objective: To report the technique and results of cheek teeth repulsion in standing, sedated horses. Study Design: Case series. Animals: Horses (n=12), ponies (6). Methods: Medical records (2006–2009) of horses that had cheek tooth repulsion while standing were reviewed. Inclusion criteria included: maxillary or mandibular cheek tooth disease diagnosed by clinical and radiographic examination where attempted oral extraction failed necessitating repulsion. Horses were sedated and a local nerve block performed. Intraoperative radiographs facilitated instrument positioning and ensured repulsion of all dental remnants. Alveolar cavities were packed postoperatively and secondary dental sinusitis treated with lavage. Results: Median horse age was 7 years (range, 1–30 years). Maxillary (n=15) and mandibular (5) cheek teeth were removed successfully. One horse was euthanatized 1 week after tooth removal because of concurrent liver disease and 10 horses (59%) had resolution of discharge after the 1st treatment; 41% of extractions required follow‐up medical or surgical treatment to resolve signs [6/12 maxillary sinusitis and 1/5 persistent mandibular drainage]. Conclusions: Standing repulsion of diseased and fractured cheek teeth is an effective means of resolving clinical signs of dental disease when oral extraction fails. Chronic sinus involvement increased the risk of postextraction surgical treatment for sinusitis.     

Two‐ and three‐dimensional computed tomographic anatomy of the enamel,infundibulae and pulp of 126 equine cheek teeth. Part 2: Findings in teeth with macroscopic occlusal or computed tomographic lesions

Reasons for performing study: Dental disease often presents a diagnostic challenge in the horse. Computed tomography (CT) is increasingly used in the evaluation of head related disease in the horse, but the CT appearance of the most common dental diseases of horses has not yet been fully described. Objective: To describe the CT appearance of the peripheral enamel, pulp, infundibular enamel and cement in equine cheek teeth with macroscopic occlusal or CT lesions. Methods: In this study, 126 cadaveric cheek teeth with eruption ages of between 0.5 and 19 years were evaluated for lesions of their infundibulae, pulp and enamel using occlusal surface morphology, 2‐ (2D) and 3‐dimensional (3D) CT and anatomical sectioning. Variations in teeth with no macroscopic lesions have been described in a previous study. The infundibular lesions were categorised further into one of 6 classifications. Results: Infundibular lesions were identified on CT in 90% (115/128) of infundibulae. Of these, 65% (83/128) had infundibular lesions on occlusal surface examination. The extent of infundibular lesions observed varied with age group. All infundibulae over 6 years post eruption had detectable lesions. Peripheral enamel hypoplasia and enamel prolapses, were observed in 10% (12/126) and 1.6% (2/126) of teeth, respectively. The CT appearance of teeth with pulp infections was seen to vary with differing pathologies. Conclusions and potential relevance: The high prevalence of infundibular lesions should encourage consideration of their clinical significance, in addition to the role of infundibulae in dental disease of the horse. Two‐dimensional and 3D CT proved to be highly valuable imaging modalities for dental disease, enabling lesions within the enamel, infundibulae and pulp of equine cheek teeth to be easily detected. The results of this study will facilitate the use of 2D and 3D CT as clinical diagnostic tools for dental disease and aid in the selection of the most appropriate treatment protocol.     

Prevalence of occlusal pulpar exposure in 110 equine cheek teeth with apical infections and idiopathic fractures

Examination of 110 cheek teeth (CT) that were clinically extracted (between 2004 and 2008) because of apical infection (n = 79; mean dental age 3.5 years) or idiopathic CT fractures (n = 31; median dental age 8.5 years), including examinations of transverse and longitudinal sections, showed the apical infections to be mainly (68%) due to anachoresis, with the residual cases caused by periodontal spread, infundibular caries spread, fissure fractures and dysplasia.The idiopathic fracture patterns were similar to previously described patterns. Occlusal pulpar exposure was found in 32% of apically infected CT, including multiple pulps in 27% and a single pulp in 5%. However, 10% of apically infected CT had changes to the occlusal secondary dentine, termed occlusal pitting, but did not have exposure of the underlying pulp. Multiple pulpar exposures occurred in some CT with apical infections, and the combination of pulp involvement reflects the anatomical relationships of these pulps. A higher proportion (42%) of CT extracted because idiopathic fractures had pulpar exposure (26% multiple, 16% single pulps), especially with midline sagittal maxillary and miscellaneous pattern mandibular CT fractures, but only (3%) had occlusal pitting.     

A study of sub-occlusal secondary dentine thickness in overgrown equine cheek teeth

The presence of cheek tooth loss or defects, with subsequent overgrowth of the opposing teeth, is common in horses. Little is known about the factors that control the deposition of sub-occlusal secondary dentine (SO2D) in normal equine teeth, but these are likely to include stimulation of the occlusal surface. There appears to be no information on the possible alterations to this process when teeth develop overgrowths and, consequently, of the net effect on SO2D thickness caused by reduced stimulation of the occlusal surface and of absent/reduced normal occlusal wear (attrition). Knowledge of the likely thickness of SO2D in overgrown teeth may help reduce the risks of pulp horn exposure or thermal damage during therapeutic reduction of overgrowths. This study utilised 24 permanent cheek teeth (CT) with overgrowths (mean overgrowth height: 9.5 mm; range, 3.4-17.9 mm), and 18 control CT obtained from 15 horses of different breeds and ages. The thickness of SO2D was measured above 94 matched pulp horns in control and overgrown CT and showed a mean value of 12.14 mm (range 1.87-36.02 mm) in overgrown teeth and of 10.25 mm (range 2.64-17.26 mm) in controls. There was no significant difference between SO2D thickness in overgrown (mean 11.38 mm) and control (11.41 mm) mandibular CT, but SO2D was significantly thicker in overgrown (mean 12.57 mm) as compared to control maxillary (9.41 mm) CT. A comparison of SO2D thickness above the 94 matched pulp horns in overgrown and control teeth showed that 49% (46/94) of pulps in overgrown teeth had less SO2D overlying them than had control teeth. Of major clinical relevance was that the height of dental overgrowths was greater than SO2D thickness over one or more pulp horns in 14/24 overgrown teeth. Consequently, reduction of these overgrown teeth to the level of adjacent normal-height teeth would cause occlusal pulp exposure in 58% of teeth, in addition to possible thermal damage to additional pulp horns. It was concluded that equine CT overgrowths should be gradually reduced, by a few millimetres at a time, over a prolonged period.     

A study of the thickness of cheek teeth subocclusal secondary dentine in horses of different ages

Reasons for performing study: There is limited knowledge on the thickness of subocclusal secondary dentine in equine cheek teeth (CT). Hypotheses: Subocclusal secondary dentine is of consistent thickness above different pulp horns in individual horses and its thickness increases with age. Methods: 408 permanent CT were extracted post mortem from 17 horses aged 4–30 years, with no history of dental disease. The CT were sectioned longitudinally in the medio‐lateral (bucco‐palatal/lingual) plane through each pulp horn, and the thickness of the secondary dentine overlying each pulp horn was measured directly. Results: The subocclusal thickness of secondary dentine above the pulp horns of CT varied from a mean thickness (above all pulp horns) of 12.8 mm (range 5–33 mm) in a 4‐year‐old to 7.5 mm (range 2–24 mm) in a 16‐year‐old horse. There was wide variation in the depth of subocclusal secondary dentine above different pulp horns, even within the same CT. In contrast to expectations, occlusal secondary dentine thickness did not increase with age. There were no significant differences in occlusal secondary dentine thickness between rostral and caudal, or medial and lateral aspects of the CT, or between contralateral CT. Mandibular CT had significantly thicker subocclusal secondary dentine than maxillary CT. Pink coloured secondary dentine was sometimes found 1–3 mm occlusal to the pulp horn in sectioned CT and this was likely caused by artefactual blood staining from the underlying pulp during sectioning. Conclusions: The thickness of subocclusal secondary dentine varies greatly between individual pulp horns, teeth and individual horses and can be as low as 2 mm over individual pulp horns. Potential relevance: Due to the great variation in the thickness of subocclusal secondary dentine between horses, and even between pulp horns in individual CT, there is a risk of exposure or thermal damage to pulp and thus of apical infection, even with modest therapeutic reductions of CT occlusal overgrowths. In the light of these findings, great care should be taken when reducing equine CT overgrowths and larger dental overgrowths should be reduced in stages.     

Use of computed tomography to investigate cheek tooth abnormalities in chinchillas (Chinchilla laniger)

Computerised tomographic scanning was used to investigate tooth structure in chinchillas ( Chinchilla laniger ), both cheek tooth crown and root abnormalities being common in this species. This paper describes a common form of dental disease affecting species with continuously growing teeth, with particular reference to the chinchilla, and confirms the potential role of computed tomography (CT) in its early diagnosis. CT imaging is compared with previously available methods of investigation which frequently fail to detect early pathological changes.     

Evaluation of the long-term oral consequences of equine exodontia in 50 horses

The aims of this study were to objectively evaluate and quantify the process of post-extraction cheek teeth (CT) dental drift in horses, and to report on associated disorders of CT wear and long-term periodontal health. Fifty horses that had CT oral extraction because of apical infection were prospectively re-examined and a full oral examination, including measurements of some dental parameters, was performed.Narrowing of the extraction space was noted in all cases with complete closure occurring in 18% of horses. The rate of dental drift was calculated as 15.7% of extraction space/year (range 4–50%) and was not associated with the age at extraction (P = 0.78) or frequency of dental care since extraction (P = 0.48). There was a significant negative relationship between the rate of dental drift and the duration of time since extraction (P = 0.008). Overgrowths were present on the opposite CT row in 98% of horses, including opposite the extracted CT and on the Triadan 06s and 11s. No significant difference was noted in either the number of diastemata (P = 0.9) or periodontal disease score (P = 0.8) between the extraction and the contralateral cheek tooth rows.     

Equine idiopathic cheek teeth fractures: part 2: a practice-based survey of 147 affected horses in Britain and Ireland

REASONS FOR PERFORMING STUDY: There is limited information on the prevalence of idiopathic cheek teeth (CT) fractures in the general equine population and on which CT are most commonly affected. OBJECTIVES: To obtain information on the prevalence of fracture patterns and clinical details of idiopathic CT fractures. METHODS: Details of cases with idiopathic CT fractures encountered were obtained via a questionnaire sent to suitably experienced veterinary practitioners and equine dental technicians (EDTs). RESULTS: Details of 147 horses that suffered a total of 182 idiopathic CT fractures; and median 0.4% (range 0.07-5.9%) of horses examined were diagnosed with such fractures; 133 maxillary CT and 49 mandibular CT fractures were found; maxillary Triadan 09s and 10s were preferentially fractured (46% of all fractured CT); fracture patterns included maxillary CT slab fractures (through 1st and 2nd pulp chambers) in 87 teeth (48% of all fractured CT), maxillary CT midline sagittal fractures (through the infundibula) in 31 CT; and various other types of maxillary CT fractures in 15 CT. In the mandibular CT, lateral slab fractures (through the 4th and 5th pulp chambers) were found in 28 CT and a variety of other fracture patterns in the other 21 mandibular CT. Clinical signs included quidding in 33% of cases, bitting and behavioural problems (29%) and halitosis (12%), however 39% of horses with idiopathic CT fractures were asymptomatic. Treatments included oral extraction of the smaller dental fragment in 37% of cases, extraction of the entire fractured tooth (9%); removal of sharp edges on the remaining part of fractured tooth (14%); reduction of height of the opposite tooth (4%); other surgical or endodontic treatments, or referral of case for further investigation and treatment (10%); or no specific treatment (39%). Following treatment, 81% of cases were reported to be asymptomatic, 6% had ongoing clinical problems and the outcome was unclear in 13% of cases. CONCLUSIONS: Idiopathic CT fractures are present in approximately 0.4% of horses and may variably cause none to severe clinical signs. Most idiopathic CT fractures respond well to treatment. POTENTIAL RELEVANCE: Understanding of the prevalence, clinical findings and treatment of idiopathic CT fractures will improve management of these disorders.     

The relationship between cheek tooth occlusal morphology, apparent digestibility, and ingesta particle size reduction in horses

OBJECTIVE: To investigate potential relationships between cheek tooth occlusal morphology, apparent feed digestibility, and the reduction in feed particle size that occurs during digestion in horses. DESIGN: Cross-sectional study. ANIMALS: 17 horses of various ages and breeds and either sex. PROCEDURES: Horses were fed 1 of 3 hay-based diets ad libitum for 14 days prior to euthanasia; nutrient analysis was performed on samples of each of the 3 diets. At the time of postmortem examination, the head was disarticulated, photographs were taken of the occlusal surfaces of the maxillary and mandibular cheek tooth arcades, and samples of stomach and small colon or rectum contents were collected for determination of apparent feed digestibility and particle size determination. An overall oral pathology score was assigned, and morphologic features of the occlusal surfaces of the cheek tooth arcades were determined. RESULTS: Results of nutrient analyses did not differ among the 3 hay diets, and there was no significant difference in apparent feed digestibility among diets. Feed particle size differed significantly among the 3 diets, but stomach content and fecal particle sizes did not differ among diet groups. No significant correlations were identified between cheek tooth morphologic variables and feed digestibility, and fecal particle size was not significantly associated with oral pathology score. CONCLUSIONS AND CLINICAL RELEVANCE: Results did not provide any evidence of associations between cheek tooth morphologic variables, fecal particle size, and apparent digestibility in horses.     

RADIOGRAPHY AND COMPUTED TOMOGRAPHY IN THE DIAGNOSIS OF NONNEOPLASTIC EQUINE MANDIBULAR DISEASE

We compared the information gained from computed tomography (CT) vs. radiography in horses with nonneoplastic disease of the mandible. We hypothesized that CT would provide additional diagnostic information. Medical records, radiographs, and CT images of horses with nonneoplastic mandibular disease evaluated between 1994 and 2008 were reviewed. Nineteen horses were identified; 11 had a tooth root abscess and related disease, four had a fracture of the teeth and/or mandible, and four had a nonneoplastic mass. Both CT images and radiographs allowed identification of diseased teeth that appeared clinically normal otherwise. CT allowed identification of teeth that were clinically affected but appeared normal radiographically. Parameters such as tooth pulp involvement, lamina dura destruction, presence of bone fragments, lingual and buccal mandibular bone periosteal reaction, and cortical bone destruction were more conspicuous with CT. Performing radiography and CT in horses with nonneoplastic mandibular disease provides a more complete evaluation than either technique alone. CT contributes additional information that could otherwise be overlooked with radiographs alone in horses with a mandibular fracture. CT provides ancillary information to radiographs in horses with dental infection or a nonneoplastic mass of the mandible.     

Extraction of 22 equine cheek teeth with displaced sagittal fractures using polymethylmethacrylate stabilisation (2011–2016)

Displaced sagittal cheek tooth fractures are a cause of oral pain, quidding and apical infection. Intraoral extraction is the preferred technique to remove affected teeth, but can be difficult due to displaced and friable fracture fragments. Stabilising fracture fragments via filling of the fracture space with polymethymethacrylate (PMMA) prior to removal may be a useful method to facilitate intraoral extraction. Case details were examined retrospectively. A total of 22 cheek teeth required extraction in 20 horses because of displaced sagittal fractures. Clinical diagnoses were made using oral examination, oral endoscopy, skull radiography and computed tomography. All procedures were performed in standing, sedated horses in stocks. Fracture spaces were cleaned and packed with PMMA and teeth removed using a routine intraoral extraction technique. Digital photographs of extracted teeth were taken and tooth measurements calibrated using digital image software. Intraoperative difficulties, as well as post-operative complications were recorded. A total of 21 maxillary and one mandibular cheek teeth were extracted. All maxillary teeth had advanced infundibular caries. Intraoral extraction was successful in 16 cases; six were unsuccessful and required repulsion due to tooth fragmentation or abnormal dental anatomy. In 11 cases, maxillary or conchofrontal sinus trephination was performed to either treat sinusitis, repulse the tooth, or both. Two horses developed short-term complications following local anaesthesia of the maxillary nerve. The mean ratio of fracture depth to tooth length was 0.59 and mean ratio of fracture width to tooth width 0.53. The limitations of the study are its small sample size, retrospective nature and lack of control group to compare extraction success in PMMA and non-PMMA groups. It was concluded that using PMMA to stabilise displaced sagittal fractures in equine cheek teeth is a simple, effective method of facilitating intraoral extraction and may reduce the need for more invasive procedures.     

Donkey dental anatomy. Part 2: Histological and scanning electron microscopic examinations

Ten normal cheek teeth (CT) were extracted at post mortem from donkeys that died or were euthanased for humane reasons. Decalcified histology was performed on three sections (sub-occlusal, mid-tooth and pre-apical) of each tooth, and undecalcified histology undertaken on sub-occlusal sections of the same teeth. The normal histological anatomy of primary, regular and irregular secondary dentine was found to be similar to that of the horse, with no tertiary dentine present. Undecalcified histology demonstrated the normal enamel histology, including the presence of enamel spindles. Scanning electron microscopy was performed on mid-tooth sections of five maxillary CT, five mandibular CT and two incisors. The ultrastructural anatomy of primary and secondary dentine, and equine enamel types-1, -2 and -3 (as described in horses) were identified in donkey teeth. Histological and ultrastructural donkey dental anatomy was found to be very similar to equine dental anatomy with only a few quantitative differences observed.     

Periapical curettage: an alternative surgical approach to infected mandibular cheek teeth in horses

OBJECTIVE: To evaluate an alternative surgical method for treating periapical infection of the mandibular cheek teeth of horses. DESIGN: Retrospective study. ANIMALS: Eleven horses (3-13 years) with periapical mandibular tooth infection. METHODS: Hospital records (1992-2002) of horses that had periapical curettage for the treatment of mandibular cheek tooth root infection were retrieved. Clinical signs, radiographic, and surgical reports were reviewed. Outcome was obtained by telephone questionnaire for 7 horses and by physical examination in 2. RESULTS: Eleven horses (14 infected mandibular molariform teeth) had periapical curettage. Two horses were lost to follow-up. Mean follow-up was 41 months; 2 horses had subsequent tooth repulsion, 7 (78%) horses healed completely although 2 horses still had some local mandibular swelling. CONCLUSION: Periapical curettage, which allows alveolar drainage, appears to be a viable treatment option for periapical infections of equine mandibular cheek teeth. CLINICAL RELEVANCE: Periapical curettage can be performed simply, without expensive imaging or surgical equipment, and thus is useful for both referral and first opinion practice.