Erosion behaviour of human, bovine and equine dental hard tissues

Dental hard tissues from different species are used in dental research, but little is known about their comparability. The aim of this study was to compare the erosive behaviour of dental hard tissues (enamel, dentin) obtained from human, bovine and equine teeth. In addition, the protective effect of the pellicle on each hard tissue under erosive conditions was determined. In situ pellicle formation was performed for 30 min on enamel and dentin samples from all species in four subjects. Calcium and phosphate release was assessed during 120 s of HCl incubation on both native and pellicle-covered enamel and dentin samples. SEM and TEM were used to examine surface changes in native enamel and dentin samples after acid incubation and the ultrastructure of the pellicle before and after erosive exposure. In general, bovine enamel and dentin showed the highest degree of erosion after acid exposure compared to human and equine samples. Erosion of human primary enamel tended to be higher than that of permanent teeth, whereas dentin showed the opposite behaviour. SEM showed that eroded equine dentin appeared more irregular than human or bovine dentin. TEM studies showed that primary enamel appeared to be most susceptible to erosion.

Functional anatomy of the equine temporomandibular joint: Histological characteristics of the articular surfaces and underlining tissues

It has been assumed that dental conditions cause disorders of the equine temporomandibular joint (TMJ), due to biomechanical overload or aberrant loading. However, the incidence of published TMJ disorders in horses is low and this leads to the question whether the equine TMJ is adapted well to its biomechanical requirements or is able to remodel its articular surfaces in response to modified loading conditions. The aim of this study was to determine the histological characteristics of healthy equine TMJs. The tissue components of the articular surfaces of 10 TMJs obtained from horses without any clinical history of dental or TMJ disorders were analysed. Apart from the mandibular fossa of the temporal bone, the osseous aspects of the TMJ exhibited a uniform zoning pattern. The articular surfaces were composed of three tissue layers: (1) a superficial cell-rich dense connective tissue layer; (2) a middle fibrocartilage layer; and (3) a deep hyaline-like cartilage layer. The articular disc was composed of an inner core of fibrocartilage and hyaline-like cartilage meshwork covered with both cell-rich dense connective tissue and fibrocartilage at its dorsal and ventral aspects. In contrast, the mandibular fossa was only covered by a dense connective tissue, frequently supplemented by a synovial membrane, suggesting low biomechanical stress. Glycosaminoglycans, which are indicative of compressive loads, were predominantly present within the rostral part of the articular tubercle and the retroarticular process, the dorsal part of articular disc and the entire mandibular head, but were absent within the mandibular fossa. The results of this study suggest the presence of different biomechanical demands in the dorsal and ventral compartment of the equine TMJ.

Functional anatomy of the equine temporomandibular joint: Collagen fiber texture of the articular surfaces

In the last decade, the equine masticatory apparatus has received much attention. Numerous studies have emphasized the importance of the temporomandibular joint (TMJ) in the functional process of mastication. However, ultrastructural and histological data providing a basis for biomechanical and histopathological considerations are not available. The aim of the present study was to analyze the architecture of the collagen fiber apparatus in the articular surfaces of the equine TMJ to reveal typical morphological features indicating biomechanical adaptions. Therefore, the collagen fiber alignment was visualized using the split-line technique in 16 adult warmblood horses without any history of TMJ disorders. Within the central two-thirds of the articular surfaces of the articular tubercle, the articular disc and the mandibular head, split-lines ran in a correspondent rostrocaudal direction. In the lateral and medial aspects of these articular surfaces, the split-line pattern varied, displaying curved arrangements in the articular disc and punctual split-lines in the bony components. Mediolateral orientated split-lines were found in the rostral and caudal border of the articular disc and in the mandibular fossa. The complex movements during the equine chewing cycle are likely assigned to different areas of the TMJ. The split-line pattern of the equine TMJ is indicative of a relative movement of the joint components in a preferential rostrocaudal direction which is consigned to the central aspects of the TMJ. The lateral and medial aspects of the articular surfaces provide split-line patterns that indicate movements particularly around a dorsoventral axis.

Dental Benign Cementomas in Three Horses

Cementoma is a very rare odontogenic neoplasm of mesenchymal origin. Clinically, in 3 horses, multiple bony enlargements of the upper and lower jaw extending into the oral cavity were observed. Radiographically, multiple, well-circumscribed, radiopaque masses surrounding the roots of the upper and lower incisors or an upper premolar tooth were present. Due to malocclusion and local pain, single teeth were extracted in each case. Grossly, a hard grayish-white mass surrounding the root of the incisors and the premolars was identified. Histopathologically, the tumors consisted of excessive deposition of cementum-like tissue. Cells, resembling cementoblasts, lined irregularly shaped lacunae, which were present in the tumor tissue, and showed minimal cellular pleomorphism. Mitotic figures were not present. Macroscopically and histologically, all 3 equine cases displayed great similarities to cementomas in other species. However, due to their high degree of differentiation, hypercementosis must be considered as a differential diagnosis.

Cranial morphology in the brachygnathic sheep

Background

Craniofacial morphology of sheep with phenotypically observed mandibular distocclusion was analysed using the multivariate techniques principle component analysis and cluster analysis in order to test whether different types of craniofacial malformations can be distinguished.

Results

The results showed 8 principal components with a variance of 82.72 % in the database. The method creates new variables then used in the Cluster analysis indicating 7 clusters with 3 different facial types: Normal, prognathia inferior and brachygnathia inferior.

Conclusion

The brachygnathic facial type was mainly characterised as a shortened mandible, the upper jaw is not significantly involved. The correlations to the temporomandibular joint were shown. Molar and premolar malocclusions were revealed in two of three Clusters. Phenotypical distocclusion was not a single criterion for the affected sheep.

Infundibula of equine maxillary cheek teeth: Part 2: Morphological variations and pathological changes

Incomplete cemental filling of the infundibula of equine maxillary cheek teeth (CT) is a common feature. Depending on the extent of the defect, three stages of infundibular decay have been suggested. However, histomorphological criteria to identify non-pathological abnormalities and destructive changes have not been defined. Six hundred and eighty eight CT with no evidence of dental diseases and 55 diseased permanent, fully erupted maxillary CT were evaluated on a macroscopic level by assessing the occlusal surface and horizontal sections, including porphyrin assays to detect residual blood within the infundibular cementum. Selected specimens were investigated on a microscopic level using routine and immunohistological staining methods to identify possible routes for the spread of infectious agents from the infundibulum into the endodontic system. Infundibular cemental hypoplasia was defined as a non-pathological developmental abnormality and was detected in >50% of CT with no evidence of dental diseases and in >70% of diseased CT. The first molar (Triadan 09) showed the highest prevalence (75%) of infundibular cemental hypoplasia. The mesial infundibulum was more often affected than the distal infundibulum. Infundibular erosion was considered as the most appropriate term to describe destructive infundibular changes. Infundibular erosion was present in <6% of CT with no evidence of dental diseases, but was detected in >27% of diseased teeth, always accompanied by endodontic disease. This suggests that teeth affected by infundibular cemental hypoplasia are prone to destructive erosion, which possibly leads to endodontic disease. Morphological factors that supplement this ethological hypothesis were described. In 74% of infundibula residual blood was identified, although no vital blood vessels were detected. It is assumed that this content of blood remained in the ample infundibular cemental blood system after tooth eruption and creates a favorable environment for microbial growth. The infundibular enamel was characterised by numerous infoldings to variable degrees and depths. In certain areas focal enamel aplasia was observed. These morphological features might contribute to microbiological settlement and spread of infectious agents through the infundibular wall into the endodontic system.

[Clinical anatomy of the horse: teeth and dentition]

The routine inspection of the equine oral cavity allows a numerical assessment of the teeth and provides information about positional changes within the dentition. By use of appropriate dental equipment, the occlusal surfaces of all teeth can be inspected and diagnosed. However, neither the teeth nor their occlusal surfaces are constant structures. Instead, equine teeth and, in particular, their occlusal surfaces are subjected to continuous morphological and positional changes due to the effects of aging and the equine-specific high amount of occlusal wear. Therefore, it is mandatory to define anatomical criteria, which allow us to distinguish between anatomical variations and pathological conditions. Moreover, an unambiguous nomenclature with regard to the equine-specific dental anatomy is essential. This article provides a tutorial overview of the equine dental anatomy as well as recent findings in the field of equine dentistry. Special attention is paid to dynamic changes within both individual teeth and dentition.

Three-dimensional anatomy of the equine sternum

The sternum is a frequently used anatomical site to obtain bone marrow for diagnostic and therapeutic purposes in equine medicine and surgery. For a safe and reproducible aspiration of sternal bone marrow, a reliable anatomical description of the sternum is mandatory. However, the anatomical literature provides very heterogeneous information concerning the structure and number of sternebrae. Isolated sterna (horses of different ages) underwent clinical computed tomography, and single sternebrae were scanned by microcomputed tomography. Data sets were analysed in detail, the dimensions of each sternebra were determined, and correlations to the age and weight were generated. A uniform arrangement of seven sternebrae within the equine sternum was obtained, whereas the 6th and 7th sternebrae were fused in all sterna. The cranial sternebrae (sternebrae 1-3) had a lentiform shape with flattened lateral sides, while the caudal sternebrae (6 and 7) were flattened dorso-ventrally. In contrast, sternebrae 4 and 5 were spherical. The single sternebrae were well demarcated to the chondral sternum and showed two different zones. The periphery consisted of radiodense woven tissue, while in the centre the radiodense tissue was loosely arranged and contained large cavities with radiolucent tissue. A thin lamina (substantia corticalis) of <1 mm was arranged around the peripheral zone. There was no correlation between the body weight and the dimensions of the sternebrae, but there was a positive correlation to the age of the horses. The obtained data provide a sufficient basis to establish a standard nomenclature of the equine sternum.

Tenotomie von Karpal- und Zehenbeugesehnen zur Korrektur der Neuromyodysplasie bei einem Kalb

Bei einem 7 Tage alten Kuhkalb wurde eine Verkürzung der Zehenbeuger, des M. interosseus medius und der Beuger des Karpalgelenks (M. flexor carpi ulnaris, M. extensor carpi ulnaris) an beiden Gliedmaßen diagnostiziert. Die manuelle Streckung der Karpal- und Fesselgelenke war jeweils nur bis etwa 120° möglich. Der über 2 Wochen durchgeführte konservative Therapieversuch mittels Stützverband, Anbringen eines über die Klauenspitze hervorstehenden Holzklotzes und Physiotherapie führte nur an der rechten Gliedmaße zu einer Verbesserung der Kontraktur. Deshalb wurde an der linken Gliedmaße eine Tenotomie des M. flexor carpi ulnaris und der Zehenbeuger sowie des M. interosseus medius vorgenommen. Nach postoperativer Versorgung mit Stützverbänden über 8 Wochen war eine vollständige Durchstreckung des Karpus und der Zehengelenke möglich. Eine Neuromyodysplasie infolge Verkürzung der Karpalgelenkbeuger kann durch Tenotomie der entsprechenden Endsehne proximal des Os carpi accessorium korrigiert werden. Dabei bleibt der Karpaltunnel intakt und es besteht keine Gefahr einer Durchtrennung von Nerven oder gar der Eröffnung des Karpalgelenks.

[Tenotomy of carpal and digital flexor tendons for correction of congenital neuromyodysplasia in a calf]

In a 7-day-old heifer calf, a bilateral flexural deformity of the forelimbs involving the digital flexor tendons, the suspensory ligament and the ulnar and radial carpal flexor tendons was diagnosed. After 2 weeks of conservative treatment consisting of manual stretching of the legs and the application of splints and wooden blocks, which were glued to the soles and extended beyond the tip of the claws, the right forelimb could be extended sufficiently to allow weight bearing, whereas the left forelimb could be passively extended to only approximately 120°. Therefore, tenotomy of the ulnar carpal flexor tendon, the digital flexor tendons and the suspensory ligament was carried out in the left leg. A support bandage was then applied to the leg for 8 weeks, after which the carpus and fetlock could be completely extended passively. Flexural deformity of the carpus caused by contracture of the carpal flexor tendons was treated by means of a tenotomy of the ulnar carpal flexor tendon proximal to the accessory carpal bone, which allowed preservation of the carpal tunnel and avoided the risk of iatrogenic damage to nerves and the carpal joint capsule.

Arthrotomy for the treatment of chronic purulent septic gonitis with subchondral osteolysis in two calves

CASE HISTORY

A 6-week-old German Holstein heifer calf (Case 1) and a 4-week-old Charolais bull calf (Case 2) were referred because of unilateral hind limb lameness. Both had been treated with systemic antibiotics by the referring veterinarian.

CLINICAL FINDINGS AND DIAGNOSIS

Based on the results of clinical, radiographic and ultrasonographic examination, a diagnosis of chronic purulent septic gonitis with subchondral osteolysis of the lateral femoral condyle was made in both calves. In Case 2 the lateral tibial condyle also showed osteolysis.

TREATMENT AND OUTCOME

Treatment consisted of arthrotomy with debridement of abnormal bone and cartilage via a craniolateral and a caudolateral approach. Case 1 was discharged from with grade 1/5 lameness 60 days after surgery. In a follow-up 15 months postoperatively, the owner reported that it had been bred at 14 months, was not lame and the affected stifle joint appeared normal. Case 2 had grade 2/5 lameness 52 days after surgery, but was sound at the time of slaughter at 22 months of age.

CLINICAL RELEVANCE

Arthrotomy via a caudolateral approach is a suitable method for the treatment of septic purulent gonitis with osteolysis of the lateral femoral and tibial condyles in calves. In these cases, this treatment resulted in the elimination of localised inflammation, prevented clinically relevant spread of infection to other organs, and restored normal joint function.

Ovine craniofacial malformation: a morphometrical study

Craniofacial malformation in 64 sheep was phenotypically described as mandibular distoclusion. Digital radiographs were examined in order to determine the degree of morphological changes in certain bones of the skull. Therefore, laterolateral standardised digital radiographs were used to determine anatomic reference points. Subsequently, five reference lines were defined and 16 linear and seven angular measurements were determined to describe malformations in the bones of the skull. Statistical analysis revealed a significant shortening of the rostral part of the corpus mandibulae and of the ramus mandibulae. However, the molar part of the mandible remained unchanged. These morphological changes caused premolar and molar malocclusion. No further craniofacial abnormalities, such as an elongation of the maxilla or of the incisive bone, were identified. In conclusion, the phenotypically observed mandibular distoclusion is caused by a shortening of specific parts of the mandible. This form of ovine craniofacial malformation is therefore best described as brachygnathia inferior.

Optimising μCT imaging of the middle and inner cat ear

This study's aim was to determine the optimal scan parameters for imaging the middle and inner ear of the cat with micro-computertomography (μCT). Besides, the study set out to assess whether adequate image quality can be obtained to use μCT in diagnostics and research on cat ears. For optimisation, μCT imaging of two cat skull preparations was performed using 36 different scanning protocols. The μCT-scans were evaluated by four experienced experts with regard to the image quality and detail detectability. By compiling a ranking of the results, the best possible scan parameters could be determined. From a third cat's skull, a μCT-scan, using these optimised scan parameters, and a comparative clinical CT-scan were acquired. Afterwards, histological specimens of the ears were produced which were compared to the μCT-images. The comparison shows that the osseous structures are depicted in detail. Although soft tissues cannot be differentiated, the osseous structures serve as valuable spatial orientation of relevant nerves and muscles. Clinical CT can depict many anatomical structures which can also be seen on μCT-images, but these appear a lot less sharp and also less detailed than with μCT.

Identification of equine cutaneous lymphangioma by application of a lymphatic endothelial cell marker

An adult horse was presented with a mass located within the dermis and subcutis of the right forelimb. At post-mortem examination there was a marked increase in thickness of the subcutis of the right forelimb extending from the fetlock to the pectoral muscles. Microscopically, the dermis and subcutis were diffusely infiltrated by endothelial-like cells forming irregular channels and cavernous spaces. Immunohistochemical examination revealed the endothelial-like cells to express vimentin, factor VIII-related antigen and PROX-1, confirming the identity of the tumour as a lymphangioma. Ultrastructural analysis showed that the cavernous spaces were lined by a discontinuous endothelium lacking any basement membrane.

Immunohistochemical detection of matrix metalloproteinase-1 in the periodontal ligament of equine cheek teeth

The hypsodont equine cheek tooth erupts continuously throughout life. The collagen fibers of the periodontal ligament (PDL) have to remodel constantly to allow the tooth to move in an occlusal direction. Remodeling of the collagen fiber bundles needs to be well-coordinated in order to maintain functional tooth support. The aim of this study was to examine the role of matrix metalloproteinase-1 (MMP-1) in the collagen remodeling of the equine PDL under physiological conditions. Specimens containing the PDL interposed between the dental cementum and the alveolar bone were taken from nine Warmblood horses at three designated horizontal levels: subgingival, middle, and apical. The expression of MMP-1 was detected immunohistochemically. MMP-1 was found to be present in the specimens of all horses. Immunopositive fibroblasts/fibrocytes were accumulated within individual single collagen fascicles. Our results suggest that MMP-1 induced collagen degradation plays a central role in the physiological remodeling of the equine PDL. The distribution of MMP-1 positive fascicles indicates well-directed remodeling which occurs as an asynchronous process, so that only single collagen fascicles are remodeled at the same time. Due to this remodeling of one fascicle at a time, the overall anchorage of the tooth is preserved at all times.

Primary culture of fibroblasts and cementoblasts of the equine periodontium

Fibroblasts and cementoblasts in the periodontal ligament (PDL) of equine cheek teeth were harvested, and monocultures were obtained by means of a "selective detachment" procedure. Cells were characterized by morphological criteria and by immunostaining for vimentin, FVIII, pan-cytokeratin, smooth muscle actin, and pro-collagen. Cementogenic potential of the cells was determined by immunostaining for osteopontin and by histochemical detection of alkaline phosphatase. Equine periodontal fibroblasts (EPF) were spindle-shaped and polygonal. Equine dental cementoblasts (EDC) grew in cobblestone-like clusters. Both EPF and EDC stained positive for vimentin. Only EPF contained smooth muscle actin, pro-collagen, and alkaline phosphatase. Few EDC stained positive for osteopontin. The phenotypes of EPF and EDC and their specific expression of proteins corresponded to PDL fibroblasts and dental cementoblasts of other species. These results indicate the potential use of EPF and EDC in an adequate in vitro model of equine cementogenesis and equine periodontal remodeling.

Oxytalan fibres in the periodontal ligament of equine molar cheek teeth

The distribution and arrangement of oxytalan fibres were examined in periodontal specimens of cheek teeth from seven horses. Oxidation prior to aldehyde fuchsin exposition permitted a selective staining of the oxytalan fibres, which are a distinct component of the elastic fibre system. On three horizontal levels of the periodontium--(a) subgingival, (b) middle third and (c) apical--two oxytalan fibre groups were shown histologically: 'blood vessel-related' and 'independent' oxytalan fibres. In levels a and b, both groups were arranged in a typical occluso-apical alignment along the reserve crown. Single oxytalan fibres deviated from their general course in order to attach to the cementum. In these cemental entheses the oxytalan fibres ran parallel to collagen fibre bundles. The interpretation of such morphological features emphasized the oxytalan fibres' capacity to improve the stability of periodontal blood vessel walls during masticatory movements. Level c, especially in regions next to the persisting epithelial root sheath, is the site of oxytalan fibre generation. This is a prerequisite for the facilitation of periodontal regeneration and reorganization during dental growth and eruption.

Caudomedial approach for removal of an ununited anconeal process and assessment of the medial coronoid process of the ulna

A caudomedial approach that allows the removal of an ununited anconeal process (UAP) is described. Intraoperative examination of the medial part of the joint to diagnose a fragmented coronoid process (FCP) is also possible using the same approach. Sixty-two joints (53 dogs) with UAP and various degrees of arthrosis were included in the study. In all joints the UAP could be removed via the caudomedial approach and the medial coronoid process could be inspected after extending the incision of the joint capsule distally. In eight cases a FCP was diagnosed and removed either by the caudomedial or by a medial approach. The results of the present study show that an UAP can occur simultaneously with a FCP in the same joint and that inspection of the medial part of the joint is useful.

The enthesis of the elbow-joint capsule of the dog humerus

The enthesis of the elbow-joint capsule in the dog is described histologically in relation to the specific mechanical forces that operate in different regions along its line of attachment. Special attention is given to the collagen fibre-bone interface in those parts of the capsule that are highly affected by mechanical stress. The histological features of the enthesis are heterogeneous along the entire circumference of the attachment site. Three types of collagen fibre-bone interconnections can be distinguished: (1) periosteal insertion: attachment to the periosteum of the humerus; (2) bony insertion: attachment directly to peripheral osteons; (3) fibrocartilaginous insertion: attachment to the bone via fibrocartilage. The periosteal insertion covers the greatest part of the joint capsule attachment line, along the peripheral borders of the radial and olecranon fossae. In contrast, bony insertions and fibrocartilaginous insertions are focally arranged: bony insertions in the caudoproximal aspect of the olecranon fossa, related to nutrient foramina; fibrocartilaginous insertions in combination with the attachment of distinct ligaments. This distribution reflects a strict relation between the type of enthesis and the biomechanical stress at the attachment site. The periosteal insertion type is predominant in entheses adjacent to pouches of a loose joint capsule -- i.e., regions less dependent on the high tensile strength of collagen fibres. Fibrocartilaginous insertions characterise areas of the joint capsule which are subjected to high biomechanical traction during joint movement. Both structurally and functionally, the entheses of the fibrous layer of the joint capsule are similar to those of tendons and ligaments.

Mucosal microvasculature of the gastric pars nonglandularis and margo plicatus in the horse: a scanning electron microscopic study on corrosion casts

The microvascularisation of the equine non-glandular gastric mucosa was investigated using corrosion casts for scanning electron microscopy. Specimens from 11 healthy horses were examined. Corresponding to the high incidence of gastric lesions in the margo plicatus, special attention was paid to the differentiation between the pars nonglandularis and the margo plicatus as a distinct area of the aglandular mucosa. In both areas, the blood vessels of the lamina propria mucosae were arranged in three vascular layers; i. e. I) a basal, II) an intermediate, and III) a subepithelial horizontal level. In the basal (I) and in the intermediate (II) layers the vascular supply was organised in arterial retia-rete arteriosum profundum, rete arteriosum subpapillare- and venous plexus-plexus venosus profundus, plexus venosus subpapillare. Vertical interconnections integrated the layers into the vascular network of the entire lamina propria. The subepithelial (III) layer represented the blood vessels of all the individual connective tissue papillae in the lamina propria mucosae. Ansae capillares intrapapillares were found in the pars nonglandularis. In contrast, each of the papilla of the margo plicatus contained a "cone shaped" rete capillare intrapapillare. The thicker epithelium and lamina propria mucosae of the margo plicatus was therefore supplied by less numerous, but longer intrapapillary blood vessel systems. The typical vascular components of the margo plicatus may be considered to be one of several links in the etiological chain which characterises gastric mucosal lesions in the horse's stomach.