Effect of rostrocaudal mobility of the mandible on feed digestibility and fecal particle size in horses

OBJECTIVE: To evaluate the effect of rostrocaudal mobility (RCM) of the mandible during extension and flexion of the atlanto-occipital joint on weight gain, feed digestibility, and fecal particle size in horses. DESIGN: Randomized controlled trial. ANIMALS: 34 pregnant mares housed in 1 barn. PROCEDURES: Horses were randomized into a treatment (n = 17) or control (17) group. All horses were sedated, and the distance between the rostral portions of the upper and lower incisor arcades was determined during extension and flexion of the atlanto-occipital joint; mandibular RCM was calculated as the difference between these values. In the treatment group, measurements were made after dental floating. Body weight was recorded 1 day before dental floating and at intervals after mandibular RCM determination for a period of 24 weeks. Feces were collected from each horse during two 5-day periods. Samples of feed and feces were analyzed to determine feed digestibility; particle size analysis was performed on dried fecal samples. RESULTS: Data obtained from each group of horses revealed that RCM of the mandible did not affect weight gain, feed digestibility, or particle size in feces; there were no differences among breeds. Controlling for age and number of dental lesions did not significantly affect results. CONCLUSIONS AND CLINICAL RELEVANCE: In horses, RCM of the mandible did not appear to affect weight gain, feed digestibility, or fecal particle size. On the basis of these and other published data, the assumption that dental abnormalities affect digestion detrimentally in horses needs to be reevaluated.     

Effect of dental correction on feed digestibility in horses

To test the hypothesis that routine dental correction (removal only of sharp hooks and points from molars and premolars) would improve digestion of a hay/grain ration whereas performance 'floats' (rounding and smoothing of the dental arcades) would adversely affect digestion, 8 mature horses free from dental correction for over a year were used. Five-day digestion trials were conducted before and 2 and 4 weeks after correction in all horses. Although all horses had sharp points and minor premolar hooks, none had severe dental abnormalities. There were no significant differences found in apparent digestion of dry matter, crude protein, neutral detergent fibre or acid detergent fibre relative to precorrection data or controls (uncorrected horses on same digestion trial). Apparent digestibility of crude protein and fibre, however, was reduced if the occlusal angle of premolar 307 was greater than 80 degrees relative to the vertical axis (flattened). It should be recommended that regular dental correction be continued. However, if only small points and hooks are present, correction will not significantly improve digestion. Performance floating does not adversely affect digestion 2-4 weeks after the procedure is performed. Alterations in molar occlusal surface angle may affect digestibility of protein and fibre.     

Effect of dental floating on weight gain, body condition score, feed digestibility, and fecal particle size in pregnant mares

OBJECTIVE: To investigate the effect of routine dental floating on weight gain, body condition score, feed digestibility, and fecal particle size in pregnant mares fed various diets. DESIGN: Randomized controlled clinical trial. ANIMALS: 56 pregnant mares. PROCEDURE: Mares were randomly allocated to 1 of 4 feed groups (n = 14 mares/group). All horses were sedated and an oral examination was performed, after which dental floating was performed on 7 horses in each group. Body weight was measured, and a body condition score was assigned before and at various times for 24 weeks after dental floating. Feed digestibility and fecal particle size were analyzed 7 and 19 weeks after dental floating. RESULTS: Weight gain, change in body condition score, feed digestibility, and fecal particle size were not significantly different between horses that underwent dental floating and untreated control horses. In contrast, weight gain was significantly associated with feed group. In the control horses, neither the number of dental lesions nor the presence of any particular type of lesion at the time of the initial oral examination was significantly associated with subsequent feed digestibility. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that dental floating does not result in significant short-term changes in body weight, body condition score, feed digestibility, or fecal particle size in healthy pregnant mares. Further studies are necessary to determine the clinical utility of regular dental floating in apparently healthy horses.     

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.     

Effect of dental correction on voluntary hay intake,apparent digestibility of feed and faecal particle size in horse

Summary In nine adult Warmblood horses with mild to moderate dental findings (no signs of discomfort during chewing), voluntary hay intake before and after dental correction was examined. In a second experiment, digestibility of feed and faecal particle size were determined (3 days of total faecal collection) before and after dental correction. During both digestion trials including a 3‐day adaptation period, the amount of hay and concentrate (mixture of oats, barley and maize) was kept constant in each individual horse before and after dental correction. Voluntary hay intake in individual horses ranged from 11 to 22 g DM/kg BW/day and did not differ before and after dental treatment. Apparent digestibility of DM, energy, crude fibre and Nfe increased significantly after dental correction (energy digestibility before dental correction 46.8 ± 7.4%, after dental correction 51.5 ± 8.5%). Apparent digestibility of feed was higher in horses eating more concentrates than in those eating less concentrates. Improvement of digestibility was more marked in horses eating larger amounts of grain. There was no relationship between severity or type of dental alterations and improvement of apparent feed digestibility. Dental correction had no effect on faecal particle size.     

Comparison of mandibular motion in horses chewing hay and pellets

REASONS FOR PERFORMING STUDY: Previous studies have suggested that temporomandibular joint (TMJ) kinematics depend on the type of food being masticated, but accurate measurements of TMJ motion in horses chewing different feeds have not been published. HYPOTHESIS: The temporomandibular joint has a larger range of motion when horses chew hay compared to pellets. METHODS: An optical motion capture system was used to track skin markers on the skull and mandible of 7 horses as they chewed hay and pellets. A virtual marker was created on the midline between the mandibles at the level of the 4th premolar teeth to represent the overall motion of the mandible relative to the skull during the chewing cycle. RESULTS: Frequency of the chewing cycles was lower for hay than for pellets. Excursions of the virtual mandibular marker were significantly larger in all 3 directions when chewing hay compared to pellets. The mean velocity of the virtual mandibular marker during the chewing cycle was the same when chewing the 2 feeds. CONCLUSIONS: The range of mediolateral displacement of the mandible was sufficient to give full occlusal contact of the upper and lower dental arcades when chewing hay but not when chewing pellets. POTENTIAL RELEVANCE: These findings support the suggestion that horses receiving a diet high in concentrate feeds may require more frequent dental prophylactic examinations and treatments to avoid the development of dental irregularities associated with smaller mandibular excursions during chewing.     

The prevalence of oral ulceration in Swedish horses when ridden with bit and bridle and when unridden

Oral soft tissue ulcers are common disorders of horses, but it is unclear if their prevalence is increased by riding horses with a bit and bridle. Oral examinations were performed on 113 horses and ponies, all which had received routine dental floating, that were divided into four groups depending on when they had last been ridden with a bit and bridle. The subjects comprised: group 1, a randomly selected population of ridden horses; group 2, a group of horses examined after being rested at pasture for 5 weeks; group 3, the previous group following 7 weeks of riding with a bit and bridle, and group 4, brood mares that had not been ridden for at least 11 months. Lip and intraoral soft tissue lesions were recorded at seven pre-determined locations, with lesions classified as large or small; acute or chronic.The examinations showed that horses that were currently being ridden with a bit and bridle had a significantly higher prevalence of large and acute buccal ulcers opposite the maxillary Triadan 06 teeth and of the commissures of the lips, as compared to horses that were not being currently ridden. It was concluded that using a bit and bridle can cause oral ulceration even in horses that have regular prophylactic dental floating. It is suggested that riding tack should be individually fitted for each horse and also that prophylactic dental treatments should be individually adapted for each horse.     

Temporomandibular joint cytokine profiles in the horse

It has been suggested that dental abnormalities lead to temporomandibular joint inflammation and pain that may be mitigated by regular dental care. There is considerable literature on the pathophysiology of equine joint disease including studies on cytokine profiles in diseased appendicular joints. This study examined the effects of age and dental malocclusions summarized as a dental pathology score on equine temporomandibular joint cytokine (IL-1, IL-6, IL-8, TNF alpha and TGF-beta1, -beta2, -beta3) concentrations. TGF-beta3 was not detected in any joint sample. IL-1, IL-6 and TNF alpha were not influenced by age. Foals had significantly lower concentrations of lL-8 and TGF-beta1, and higher levels of TGF-beta2 compared with older horses. Age did not effect cytokine concentration in older horses although there was a trend towards increasing 1L-8 with age. The dental pathology score increased with age in mature horses, however there was no effect of dental pathology score on cytokine concentration. There was no effect of incisor eruption, and presence or number of periodontal lesions on temporomandibular joint cytokine concentration. Our findings indicate that age but not dental pathology affected temporomandibular joint proinflammatory cytokine concentration in this population of horses.     

Kinematic analysis of equine masticatory movements: comparison before and after routine dental treatment

The objective of this study was to compare masticatory movements before and after dental treatment using kinematic analysis. The masticatory movements of 15 adult Warmblood horses with mild dental pathology chewing standardised hay were recorded on three consecutive days before and three times after (days 7, 21, 28) dental correction. The results of the leading mandibular tracking marker, located at the caudal edge of the inter-mandibular suture, were compared statistically. Reproducibility of measurements prior to dental treatment was excellent (P<0.05). Rostrocaudal mandibular motion was significantly reduced after dental correction (9±2mm vs. 8±2mm; P=0.046). Oscillations during the power stroke were significantly reduced after dental correction (R(2)=98.3%±0.3 vs. 98.8%±0.3; P=0.050). Although significant changes were observed in individual horses, the overall results of lateral and dorsoventral mandibular motion did not reveal significant differences. In conclusion, kinematic analysis of masticatory movements provided reproducible results and may be useful to evaluate changed movement patterns following dental correction.     

Fractures of the rostral portion of the mandible and maxilla in horses: 89 cases (1979-1997).

OBJECTIVE: To compare fracture locations, repair methods, complications, and outcomes of horses with fractures of the rostral portions of the mandible and maxilla. DESIGN: Retrospective study. ANIMALS: 89 horses with fractures of the rostral portions of the mandible and maxilla. PROCEDURE: Medical records and radiographs were reviewed. Fractures were categorized by fracture location and stability. Postoperative complications and long-term outcome were determined by clinical examination and telephone interviews with horse owners. RESULTS: 4 fracture types were recognized. Fractures involving just the alveolar plate (33%) and those involving the alveolar plate and the body of the bone (32%) were most common and were often repaired by interdental wiring. Unilateral fractures of the mandible (11%) were managed without surgery if stable. Unstable fractures were repaired with wires, a U-shaped bar (U-bar), or a bone plate. Bilateral fractures (24%) were often repaired with orthopedic wires in foals or with a U-bar, acrylic splint, wires, or bone plate in adult horses. In 2 horses, bilateral fractures were managed conservatively. Short-term complications developed in 24 of 89 (27%) horses. Soft tissue infections and wire loosening or failure were the most common short-term and long-term complications. Wire replacement was not required in any horses after release from hospital. Persistent draining tracts were most often associated with bone sequestration. Long-term functional and cosmetic outcomes were favorable for all fracture types and repair methods. CLINICAL IMPLICATIONS: Although complications in horses with fractures of the mandible and maxilla are common, long-term prognoses for functional and cosmetic outcome are favorable.     

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.     

Measurement of clinical crown length of incisor and premolar teeth in clinically healthy rabbits

The clinical crown length of rabbit teeth has not been well documented. The aim of this study was to determine the clinical crown length of incisor and cheek teeth, and the periodontal probing depth in young healthy rabbits without clinical signs of dental disease. Two groups of 20 male rabbits were measured, the first in 2007 and the second in 2008/2009. The measurements were taken with rabbits under general anesthesia using a periodontal probe. The average crown length (mm) of the mandibular third and fourth premolar, and maxillary second premolar teeth was 3.1 +/- 0.4, 2.6 +/- 0.4, and 1.5 +/- 0.4, respectively. The periodontal probing depth for the cheek teeth in the maxilla and the mandible was very similar (0.5 - 1.0-mm). There was a minor difference in the average crown length (mm) of the mandibular (6.4 +/- 0.6) and maxillary (6.1 +/- 0.9) incisor teeth. The periodontal probing depth (mm) was different when comparing maxillary (2.2 +/- 0.4) and mandibular (5.1 +/- 0.8) incisor teeth. The divergence in tooth length in individual rabbits and between the two groups was minimal. Measuring the crown length of the rostral cheek and incisor teeth with a periodontalprobe is easy to do in the rabbit and should be integrated into the clinical examination. The measurement results of this study can be used as a reference when trimming teeth.     

Dental dolorimetry for the evaluation of an analgesic agent in the horse

A monopolar electrode was implanted surgically in the canine tooth dentine layer to evaluate pain threshold responses of horses. A constant-current stimulator was used to deliver a known electrical current to the tooth pulp nerve. A single stimulus of 2-ms duration, repeated at greater than or equal to 20-s intervals, was used to elicit a head lift response. The lowest current level that produced 3 positive head lift responses was recorded as the pain threshold of the horse. The testing technique, dental dolorimetry, was easily performed. Tooth pulp pain thresholds (TPPT) were established on 8 nonmedicated adult male horses. Electrodes were nonreactive and remained functional for up to 98 days. Base-line TPPT values were consistent with repeated measurements on the same day and measurements on subsequent test days. The quantity of electrical current necessary to elicit the TPPT was increased after administration of xylazine HCl as a test analgesic.     

Use of colonic luminal pressure to predict outcome after surgical treatment of strangulating large colon volvulus in horses

OBJECTIVE: To evaluate the relationship of colonic luminal pressure (CLP) measurements to outcome in horses with large colon volvulus (LCV) after either manual correction or large colon resection and anastomosis (LCRA). STUDY DESIGN: Retrospective study. ANIMALS: Horses (n=57) that had LCV. METHODS: Records for horses with LCV (March 1997-December 2003) were reviewed. Inclusion criteria were strangulating LCV proximal to the cecocolic ligament (>270 degrees), recorded CLP, and successful recovery from anesthesia. CLP measurements and survival/mortality rates were compared between horses that had manual correction (M) or LCRA (R). RESULTS: Of 57 horses, 27 had M and 30 had LCRA. For group M, CLP measurements had a sensitivity of 0.60 and specificity of 0.77 for predicting survival, whereas for group R, sensitivity was 0.50 and specificity was 0.54. CONCLUSION: In our LCV population, elevated CLP measurements had poor accuracy for predicting outcome in horses after surgical correction, especially after LCRA. CLINICAL RELEVANCE: CLP measurements based on a single hospital population of horses with LCV should be used with caution for other hospital populations of LCV. CLP may be only one of many variables needed for predicting outcome of horses with strangulating LCV, especially after LCRA.     

Diagnostic findings and prognosis following arthroscopic treatment of subtle osteochondral lesions in the shoulder joint of horses: 15 cases (1996-1999)

OBJECTIVE: To determine clinical, scintigraphic, radiographic, and arthroscopic findings and results of treatment in horses with lameness attributable to subtle osteochondral lesions of the shoulder joint. DESIGN: Retrospective study. ANIMALS: 15 horses. PROCEDURE: Medical records were reviewed, and results of physical examination, scintigraphy, radiography, arthroscopy, and treatment were recorded. RESULTS: Severity of lameness ranged from grade 1 to 4. Response to shoulder flexion or extension was variable. Twelve horses had a narrow upright foot. Intra-articular anesthesia of the shoulder joint localized the cause of the lameness to the shoulder joint in 9 of 10 horses. Scintigraphic abnormalities were detected in 4 of 6 horses. Radiographic lesions were subtle and included glenoid sclerosis, focal glenoid lysis, small glenoid cysts, and alterations in the humeral head contour. Arthroscopic evaluation confirmed clefts in the glenoid cartilage, glenoid cysts, a humeral head cyst, fibrillation of the humeral head cartilage, cartilage fragmentation, or a nondisplaced fracture of the humeral head. After treatment, 12 horses returned to their previous level of performance, 1 was sound for light riding, 1 remained lame, and 1 was euthanatized because of chronic lameness. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that a combination of physical examination, scintigraphy, and radiography is necessary to diagnose subtle osteochondral lesions of the shoulder joint in horses. Arthroscopy can be used to confirm the diagnosis and treat cartilage and subchondral bone lesions. Young and middle-aged horses with subtle osteochondral lesions of the shoulder joints have a good prognosis for return to performance following arthroscopic treatment.     

Mandibular Condylectomy Technique and Results in Normal Horses

A technique of mandibular condylectomy and menisectomy is described. Unilateral condylectomy and menisectomy were performed in two horses, and two horses were treated by bilateral condylectomy and unilateral meniscectomy. Minor temporary alterations in mastication occurred following unilateral condylectomy; more severe and longer lasting abnormalities of prehension and mastication occurred following bilateral condylectomy. Malocclusion occurred in all horses following surgery but was only clinically significant in one horse that developed occlusion of the lower incisor teeth 3 mm caudal to the upper incisor teeth following bilateral condylectomy. Maximal mouth opening was normal following unilateral condylectomy and increased following bilateral condylectomy, both immediately following surgery and after 16 weeks. Maximal lateral deviation of the mandible was increased immediately following unilateral and bilateral condylectomy; 16 weeks following surgery one joint had increased, and two had normal and three had decreased maximal lateral deviations. On radiographic, gross, and histological evaluation, the condylectomy sites underwent remodelling and bony proliferation to produce "pseudo" condyles. At necropsy, 16 weeks following surgery, five of the six operated temporomandibular joints contained fibrous tissue with single or multiple cavities lined by synoviocytes. The nonoperated temporomandibular joints were normal. Functional use of the mandible was good in three horses; the fourth horse developed significant malocclusion and had satisfactory function following bilateral condylectomy.     

合作猪与大白猪头骨形态比较

以6月龄的合作猪、大白猪猪头为试验材料,运用大体解剖学的方法对猪头进行处理,测定了6月龄合作猪和大白猪头骨相关的基本量度指标、较大头骨的面积及牙齿齿式。研究结果表明,合作猪头骨大部分基本量度指标及较大头骨面积指标均极显著小于大白猪,合作猪切齿及犬齿的生长稍早于大白猪。     

The teeth of the horse: evolution and anatomo-morphological and radiographic study of their development in the foetus

The aim of this work was to study the ontogenetic process in teeth from their early appearance in the ossifying matrix of the mandible and maxilla, in different foetuses of scalar ages. Radiographic examinations of the skull and mandible hemisections were performed and the latero-medial (LM) and dorsoventral (DV) projections for the skull and mandible were analysed. A high-definition film-screen combination was used for this study. The exposure values ranged from 35 kV/6 mAs to 58 kV/10 mAs, according to the size of the skulls and their degree of ossification. The first dental germ observed was the P3, at 138-140 days of pregnancy. At 146 days, P2 and P4 dental germs were visible. At 160-168 days, the dental germ of the first deciduous incisor tooth (I1) appeared; at 180-188 days of pregnancy the germ of the second (I2), and at 224 days the germ of the third (I3), were detectable. At 275 days the dental germ of the mandibular first molar tooth (M1) appeared, while the maxillary M1, which was not visible radiographically, was represented by a jelly-like amorphous body within its alveolar cavity.     

Mandibular Osteodistraction for Correction of Deep Bite Class II Malocclusion in a Horse

Objective— To describe a technique for, and outcome after, mandibular osteodistraction in the horse.
Study Design— Clinical report.
Animals— Warmblood horse.
Methods— A half ring external fixator was applied on both sides of an osteotomy site performed on the mandible of a colt. A bite plate was placed on the upper incisors creating occlusion between lower and upper jaw. After a 5-day latency period, distraction was applied (1 mm/day) until the overjet was judged normal.
Results— Mandibular elongation and correction of brachygnathia was obtained without major complications. Six months after the procedure the overjet reduction was considered stable.
Conclusions— Mandibular osteodistraction can be considered for treatment of severe brachygnathia in yearlings.
Clinical Relevance— Distraction osteogenesis has the advantage of progressive elongation of the mandible, allowing concurrent bone remodeling and soft tissue adaptation. Severe mandibular incisor malocclusion in horses outside the maximal growth phase can be corrected using this technique.     

Relationship of cheek tooth abrasion to fluoride-induced permanent incisor lesions in livestock

Teeth from cattle, sheep, and horses that ingested various fluoride intakes and teeth from field studies of these species plus deer, elk, and bison were examined for abnormalities. Approximately 99,000 animals in 322 herds were examined for fluorosis. From field studies, 988 cattle of various ages and with different degrees of dental fluorosis were slaughtered and necropsied. The severity of fluoride-induced mottling, hypoplasia, and abnormal abrasion of paired permanent incisor teeth was correlated with abrasion of premolar and molar (cheek) teeth that form and mineralize at approximately the same age. Severe irregular wear of cheek teeth impaired mastication and resulted in poor utilization of feed and unthriftiness. Excessive amounts of fluoride during tooth formation and mineralization induce characteristic dental changes. Offspring from the fluoride-affected animals did not have discernible fluoride-induced lesions in the deciduous teeth.