Effects of inflammatory periodontal disease ('broken mouth') on the ultrastructure of collagen fibrils in the sheep incisor periodontium

The ultrastructure of the matrix of the sheep central incisor periodontium showing clinical signs of severe periodontitis was analysed quantitatively. The distribution of collagen fibril diameters in the lower dental pad changed from a bimodal distribution seen in healthy periodontia to a unimodal distribution. Collagen fibrils with an abnormal morphology were seen in the connective tissue adjacent to the crest of the alveolar bone. These results suggest that the deepening periodontal pocket resulting from inflammation removes the major area of support for the tooth and abnormal loads are applied to fibres deeper within the tissue.     

A method for the measurement of the gingival sulcus of sheep.

A method for measuring and comparing the depths of the gingival sulcus of sheep in the incisor region at necropsy is described. The method was devised to assess and compare dental health in groups of sheep with and without premature loss of incisor teeth (broken mouth). The technique involves the use of paper spills in combination with dental plaster models.     

Variability in the eruption of the permanent incisor teeth in sheep

The incisor teeth of 176 sheep of six breeds were inspected every two to three months for a year to record the shedding of the deciduous teeth and the eruption of the permanent teeth. In all the breeds the permanent central incisors erupted at between 12 and 18 months of age. In 96 per cent of the sheep the permanent middle incisors erupted at between 18 and 26 months; and in 92 per cent the permanent lateral incisors erupted at between 24 and 36 months of age. The permanent corner teeth erupted at between 32 and 44 months in 96 per cent of the sheep. The gingival redness and swelling accompanying the eruption of a permanent tooth disappeared within two months. In 14 cases two pairs of incisors erupted during the year, in 18 cases the incisors erupted asymmetrically, and in 22 cases no incisors erupted. Rotation of one incisor was observed in five sheep and was combined with dental deviation in one.     

A study of the ultrastructure and staining characteristics of the 'dental star' of equine incisors

The objective of this study was to examine the diameter, extent, orientation and contents of dentinal tubules in order to validate the hypothesis of pigment penetration into the dental star of equine incisival occlusal surfaces. The time of appearance and the configuration of the dental star on the incisival occlusal surface are macroscopically visible features that, along with other more reliable parameters, are used for the determination of horses' age. Although dental stars are an integral part of the equine incisor occlusive surface, the exact nature and microstructure of the dental star are poorly documented. Therefore, equine incisor dentine was examined macroscopically and by scanning electron microscopy to elucidate numerical density, diameter and 3-dimensional organisation of the dentinal tubules in the dental star. The dental star is surrounded by primary dentine and consists of a central core of tertiary dentine, an intermediate ring of pale secondary dentine and a peripheral rim of darker, yellowish-brown secondary dentine. The central core of tertiary dentine contains relatively few dentinal tubules (<8000/mm2) that have small diameters (mean +/- s.d. 1.67 +/- 034 microm) and are arranged in an irregular pattern. The surrounding pale ring of secondary dentine comprises manifestly more and wider tubules that lie almost parallel to the occlusal surface. The dark peripheral rim of the dental star contains high numbers of tubules (28,000-58,000/mm2) that have wide luminal diameters (mean +/- s.d. 3.09 +/- 0.31 microm) and open perpendicular to the occlusal surface. In contrast, the primary dentine surrounding the dental star is made up by a lower number of dentinal tubules (<25,000/mm2). The tubules of primary dentine, which are initially mean +/- s.d. 5.15 +/- 0.80 microm wide, are narrowed by circumferential deposits of peritubular dentine and are obliquely exposed at the occlusal surface. From these observations, it was concluded that the regional differences in numerical density, diameter and spatial orientation of the dentinal tubules may influence the penetration of food pigments into the equine occlusal surface and result in the particular staining of the dental star.     

The pathogenesis of excessive wear in the permanent teeth of sheep

The two central pairs of permanent incisor teeth (l1P, I2P) were compared post mortem in sheep from two flocks, one of which showed excessive wear. Sheep were usually killed in groups of six. Excessive wear occurred during the winter and spring after the eruption of l1P. When l1P erupted at an early age it was also subject to that season;s wear but when it erupted at a later age, it was subject to less wear according to the amount of time it was in apposition with the dental pad during the high wear season. A small amount of compensatory growth at the root of the tooth occurred in some sheep when cementum was deposited on the apex. Apparent eruption of the crown of the tooth was actually due to gum recession. Normal reparative dentine was laid down in the pulp cavity of the crown of the tooth in anticipation of wear, but where wear was excessive unstructured dentine was deposited. In two cases the rate of wear was so great that the reparative dentine could not keep up and infection was able to gain access to the pulp cavity. There was no evidence of difference in the rate of wear of the molar teeth between the two flocks.     

Dental configuration among different breeds of sheep

Three breeds of sheep, Southdown, Suffolk and Romney, and two mixed breeds, Border Leicester over Romney and Coopworth over Romney, managed identically on a research station, where they were free from culling and allowed to live their natural life, had their dental configuration examined. The sheep were divided into age groups with 10 sheep in each. The least variation was found in the relation of the upper dental pad to the lower jaw. The most statistically significant differences were found in the first age group: one year six months. The Suffolk breed was noticeably different from the others. Deepened gingival sulci, as well as the inconsistency of bleeding after probing associated with labial gingivitis highlighted the problems of using these latter criteria as indicators of health or disease among sheep on the basis of a single examination.     

The effect of intralesional injection of bone marrow derived mesenchymal stem cells and bone marrow supernatant on collagen fibril size in a surgical model of equine superficial digital flexor tendonitis

Reasons for performing study: Collagen fibril size is decreased in repair tissue following tendon injury compared to normal tendon matrix in horses. Mesenchymal stem cells have been suggested to promote regeneration of tendon matrix rather than fibrotic repair following injury, although this concept remains unproven. Objectives: To explore the hypothesis that implantation of autologous mesenchymal stem cells derived from bone marrow into a surgically created central core defect in the superficial digital flexor tendon (SDFT) of horses would induce the formation of a matrix with greater ultrastructural similarities to tendon matrix than the fibrotic scar tissue formed in control defects. Methods: Tissue was collected 16 weeks after induction of injury and 12 weeks after treatment from normal and injured regions of control and treated limbs of 6 horses and examined using transmission electron microscopy. Collagen fibril diameters were measured manually with image analysis software and surface areas calculated. Three parameters assessed for normal and injured tissue were mass average diameter (MAD), collagen fibril index (CFI) and the area dependent diameter (ADD). Results: Normal regions from both treated and control limbs displayed higher MAD and CFI values, as well as a characteristic bimodal distribution in fibril size. Injured regions from both treated and control limbs displayed significantly lower MAD and CFI values, as well as a unimodal distribution in fibril size. There were no significant differences between treated and control limbs for any of the parameters assessed. Conclusions: Intralesional injection of autologous bone marrow derived mesenchymal stem cells had no measurable effect on the fibril diameter of collagen in healing tissue in the SDFT of this experimental model 16 weeks after injury. Potential relevance: Favouring matrix regeneration over fibrotic repair may not be the mechanism by which autologous mesenchymal stem cells assist healing of tendon injury.     

Age-related differences in collagen crimp patterns in the superficial digital flexor tendon core region of untrained horses

Objective To measure collagen fibril crimp angles and lengths as well as collagen fibril mass-average diameters in central and peripheral regions of the superficial digital flexor tendon of wild horses, to ascertain any age-related changes in either region in the absence of imposed galloping exercise.
Design Measurements from a random cull of wild horses.
Sample population Superficial digital flexor tendon samples were taken from 23 wild horses ranging in age from two to ten years.
Procedure Horses were divided into 'young' (< 5 years, n = 10), 'middle-aged' (5 to < 10 years, n = 9) and 'old' groups (10+ years, n = 4) and the mean crimp angle, mean crimp length and collagen fibril mass-average diameter calculated for the central region, and for the peripheral region of each group. Differences between groups and regions were analysed using two-tailed t tests.
Results The crimp angle for the central region was found to decrease with age, so that in old horses it was smaller than that for the tendon periphery (P < 0.05). The crimp angle for the latter region did not alter significantly with age. Crimp period lengths and collagen fibril mass-average diameters did not show significant changes with age in either region.
Conclusion Reduction of the crimp angle in the core of the superficial digital flexor tendon occurs normally with age, as tendons of older animals would have undergone a higher number of loading cycles. It is possible that athletic training increases the frequency and/or the magnitude of high loading cycles experienced by the tendon, and may accelerate and worsen the normal load-related ageing process in the superficial digital flexor tendons of young performance horses, particularly in the central regions where lesions usually occur.     

The effect of gastro-intestinal parasitism on the temporary dentition of lambs

The temporary dentitions of 18 to 39-week-old lambs with a very light or a very heavy parasite burden are compared. The heavily parasitised lambs developed longer temporary incisors which tended to protrude further forward in relation to the upper dental pad. They showed absolute hypocalcaemia and hypoalbuminaemia and relative hypophosphataemia and hypoproteinaemia and in the alveolar bone of the mandible there was a reduction in ash and matrix densities and matrix mineralisation. The incisor protrusion and lengthening may have been a consequence of the loss of supporting bone, but inappetance was likely to have been a factor contributing to the lengthening.     

A laboratory method for studying tooth mobility of the mandibular central incisor of the sheep

Linguolabially directed loads of 0.01 to 1.0 N were applied to a mandibular central incisor in each of 12 four-year-old ewes with healthy mouths. For each incisor, tooth position was monitored continuously with an ultrasonic displacement transducer. On suddenly applying a load and maintaining it for five minutes, a biphasic pattern of displacement was recorded, a phase of rapid displacement being followed by a more gradual one. A similar biphasic recovery response was seen on suddenly removing the load. These patterns are viscoelastic-like. The group mean displacements showed that for all phases the responses were force-dependent, though not linearly graded. For a given load, the group mean displacements were considerably larger than those reported previously for the teeth of other animals, supporting the impression that the sheep incisor is extremely mobile. These data will provide a baseline for studies on the mobility of the teeth of sheep with inflammatory periodontal disease ('broken mouth').     

Characteristics, prevalence and aetiology of lesions of the oral mucosa in adult sheep

A total of 214 sheep with lesions of the oral mucosa were recorded at the Veterinary Laboratories Agency regional laboratories between March 15, 2002 and February 28, 2003. Using denominator data from the scrapie abattoir survey a prevalence of 0.95 per cent (95 per cent CI 0.82 to 1.10 per cent) was recorded, and using the fallen stock survey a prevalence of 1.15 per cent (95 per cent CI 0.64 to 1.91 per cent) was recorded. The lesions varied widely and included dental pad lesions in 20 per cent of cases. In total, 248 sites were affected, the commonest being the lower gum below the incisors, which was affected in 100 sheep. Most of the lesions were 1 cm or less in diameter. Ninety per cent of the 251 lesions examined histologically were erosions, ulcers, healed ulcers, focal epithelial necrosis or haemorrhages, and the changes observed indicated that trauma was the most likely primary cause.     

The pathogenesis of excessive wear in the deciduous teeth of sheep

The teeth and various supporting and ancillary tissues were examined post mortem from two flocks of sheep, one of which had previously shown high deciduous incisor wear. Sheep were killed in groups selected on clinical signs at equivalent ages from birth to 116 weeks of age. At the end of this time the lengths of clinical crowns of the remaining deciduous incisor teeth in the high wear flock were not measurable, whereas the other flock had up to 5.5 mm in visible crown. Using the cingulum as a marker, measurements were made from extracted teeth of the attrition of the crown and size of the root. The tooth root did not grow substantially longer after the 13th week of the sheep;s life. Wear facets were just visible in some sheep at six weeks. More rapid wear occurred three times in the high wear flock. The first of these was relatively small and occurred between the 13th and 27th week of age in I1 and I2. The second was larger and occurred between the 38th and 57th week of age in the winter/spring period. A third period of wear, which was not measured from the cingulum, because this structure had by then been worn away, was seen in the remaining deciduous teeth between the ages of 91 and 110 weeks of age, i.e., during the second winter and spring. In the low wear flock the first of these periods of wear did not occur, the second was of shorter duration and smaller size, and the third equivocal. Eruption of the teeth after the 6th week was principally passive. There was no difference in the degree of wear of the molar teeth from the two flocks. Histological examination showed that the wear was compensated for by the deposition of reparative dentine in the pulp cavity. This usually gave the appearance of an ordered process. However, when wear was excessively rapid, a different, less orderly form of reparative dentine was laid down. In a few cases the reparative process was not fast enough, and a connection developed between the mouth and the pulp causing pulpitis. There was no histological evidence that the supportive tissues of the teeth, or the upper dental pad, contributed to the excessive wear.     

Effect of dental floating on the rostrocaudal mobility of the mandible of horses

OBJECTIVE: To evaluate the effect of dental floating on the position of the mandible relative to the maxilla (a measure of rostrocaudal mobility [RCM] of the mandible) during extension and flexion of the head of horses. DESIGN: Randomized controlled blinded trial. ANIMALS: 59 horses housed in 1 barn. PROCEDURE: Horses were formally randomized into a treatment (n = 33) or control (26) group. All horses were sedated, and the distance between rostral portions of the upper and lower incisor arcades were determined with the head fully extended and flexed at the poll (the difference in measurements represented the RCM of the mandible). The oral cavity was examined. For the treatment group, dental floating was performed, and the incisor arcade measurements were repeated. RESULTS: Dental correction resulted in a significant increase in RCM of the mandible in 31 of 33 horses. The mobility was greater in heavy horses than that detected in other breed classifications. Age and number of dental lesions did not significantly affect mobility before or after dental floating. CONCLUSIONS AND CLINICAL RELEVANCE: Dental floating increased RCM of the mandible, but measurement of this variable was not an indicator of the number or extent of dental lesions, and no specific dental abnormality appeared to significantly affect RCM of the mandible in horses. In horses, measurement of RCM of the mandible can be used as a guide to determine whether dental correction is necessary; after dental floating, it can be used to ensure that irregularities of the occlusal surface have been corrected.     

The influence of the ovulation rate on ultrasonically determined ovine corpus luteum morphometry and progesterone concentrations in cyclic and early pregnant sheep

The objective of the present study was to describe morphology and function of the Corpora lutea (CL) during the oestrous cycle and early pregnancy in sheep with different ovulation rates. In total 40 Booroola. Mutton Merino crosses [heterozygous carriers (FecBFec+) and non-carriers (Fec+Fec+) of the Booroola-fecundity gene (FecB)] with ovulation rates 1 to 4 were examined. During the oestrous cycle (n = 20) and the first month of pregnancy (n = 20) blood samples were taken daily (radioimmunoassay of progesterone) and an ultrasonic ovary diagnosis was conducted. The ewes were scanned transrectally with a 7.5 MHz linear probe lying in a dorsal position. During every examination the CL could be detected. The number and the diameter of the CL were documented and the total volume of luteal tissue per ewe was calculated. The effect of the ovulation rate on CL-morphology (diameter and total volume of luteal tissue per ewe) and peripheral progesterone concentrations were assessed by one-way ANOVA. On day 6 and 7 post ovulationem in cyclic and early pregnant sheep 42% of the diagnosed CL had a cavity. On day 11 (cyclic sheep) and day 10 post ovulationem (early pregnant sheep) this number decreased to 22% (p < 0.05). Both conditions of the CL (compact or with a central cavity) are similar in function and should be regarded as appearances of the same basic process. From the third day onwards the ovulation rate influenced significantly (p < 0.05) the development of the outside diameters of the CL. However, the ovulation rate had no effect on the total volume of the luteal tissue per sheep and on the progesterone concentrations. Yet, in sheep with the ovulation rate 1 significantly lower progesterone concentrations were determined than in sheep with the ovulation rates 2 to 4. In sheep with the ovulation rates 2 to 4 the peripheral progesterone concentrations did not differ significantly. In cyclic and pregnant sheep there is a positive correlation (r = 0.75, p < 0.05) between the progesterone concentration and the total volume of luteal tissue. Considering the smaller diameters of the preovulatory follicles it seems that the development of the CL continues until a threshold-value of progesterone and/or of the total luteal tissue is exceeded. Ewes with low ovulation rates reach this threshold-value with only a few but large CL. With increasing ovulation rate the CL tend to have smaller diameters.     

The development of oral lesions in lambs naturally infected with orf virus

Stomatitis in sheep caused by orf virus can be confused with lesions of more economically significant diseases, including foot-and-mouth disease, but there is no published account of the sequential development of oral orf lesions in the sheep. This report describes the clinical appearance of such lesions during a natural outbreak of the disease in young lambs. Lesions were seen on the gingiva, the tongue and the dental pad/hard palate, and progressed from small erythematous papules to larger, often coalescing papules that in some cases were ulcerated. Resolution started within seven days and was complete within 22 days. The lambs continued to suck and thrive throughout the infection. Lesions at all stages were proliferative, providing a major differentiating factor between orf and other causes of stomatitis in sheep.     

Histology and ultrastructure of the developing superficial digital flexor tendon in rabbits

This study was designed to investigate the developmental changes in the superficial digital flexor tendon (SDFT) of the white New Zealand rabbit, from 5 to 7 days pre-natal to 112 days post-natal (PN), at histological and ultrastructural levels. The tendons changed from being highly cellular with 13079 ± 2538 cell/mm² and little directional organization to a longitudinally oriented, predominantly connective tissue structure with relatively few, mature tenocytes (2384 ± 365 cell/mm²). Fibrillogenesis was seen in isolated vacuoles of fibroblast cytoplasm during fetal life as well as after birth, but less frequently with increasing age. At the ultrastructural level, there was a progressive increase in the mean diameter of collagen fibrils with age throughout the population , until PN day 28. A bimodal distribution of collagen fibril size was first observed on PN day 56 while at day 112, the fibrils were fully differentiated and showed a multimodal size distribution. The development of elastic fibres preceded that of collagen fibres and accompanied progressively more marked sinusoidal crimping in collagen fibres on PN days 7 and 14. The tendons of older animals became less tightly crimped. The cells of the epi- and endotenon were less mature and relatively undifferentiated compared with the cells in the body of the tendon of the same age, which might explain their ability to initiate healing of tendon injuries in older animals. In conclusion, extensive changes were observed in tendons during growth and maturation, with diameters of collagen fibrils, tissue orientation and cellularity being the parameters affected, probably due largely to increased physical activity.     

Restoration of the anterior dentition of a Canadian beaver (Castor canadensis)

An eight-year-old beaver lost one of its upper central incisors through unknown causes. As the anterior teeth of this species continually erupt in a similar manner to rodents' teeth, the unopposed lower incisor had over-erupted perforating the palate and entered the nasal cavity. The height of the lower incisor tooth was reduced and a cobaltchromium alloy bridge was constructed which was attached to the remaining upper incisor. The occlusal surface of the bridge was of sufficient width that both incisors could contact it. It was cemented into place with composite resin cement and cross-pinned through the labial surface of the metal into the tooth substance. It is unknown how such treatment will affect the biological processes underlying the continually erupting incisor and the animal is being monitored for any adverse effects.     

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.     

Functional significance of the morphology and micromechanics of collagen fibres in relation to partial rupture of the superficial digital flexor tendon in racehorses

The high incidence of partial rupture of the superficial digital flexor tendor in the equine athlete represents a major cause for concern in the racing industry. Frequently, the lesion is localised to the central core of the tendon. This study tested the hypothesis that the site specific structural failure results from differences in the collagen fibre morphology and associated micromechanics between central and peripheral regions of the tendon. Bundles of collagen fibres were dissected from central and peripheral sites in the mid-metacarpal region of the tendon. Crimp morphology was quantified by polarised light microscopy and mechanical characteristics determined using a fibre tensometer. In older horses, centrally located fibres showed significantly lower values for crimp angle, crimp length and toe limit strain than seen peripherally. There were no significant differences in these features between corresponding sites in the younger horses. No significant difference between sites was found in elastic modulus in either group. These data indicate a non-uniform functional stress distribution which may result from ageing or be related to the exercise history as a feature of accumulated damage. These observations may explain the location of central core lesions seen on clinical examination.     

Noradrenergic and cholinergic innervation of the accessory sexual glands in male sheep

Immunohistochemistry was applied to determine the distribution patterns of nerve fibres containing tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DbetaH), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP) and vesicular acetylcholine transporter (VAChT) in the prostate, seminal vesicle (SV) and bulbourethral glands (BU) of male sheep. In all organs studied, cholinergic innervation was more developed than noradrenergic innervation. Numerous VAChT-immunoreactive (IR) nerve fibres were found in the muscular layer and mucosa of the SV and BU as well as in the prostate. A similar abundance of noradrenergic nerve fibres (showing immunoreactivity both to TH and DbetaH) was also found in both layers of the SV and BU (but not in the prostate). In the prostate a moderate density of VIP-IR nerve fibres was present but only very scarce NPY-IR nerve fibres were shown. All the studied accessory sexual glands (ASG) of male sheep contained VIP-IR nerve fibres in a similar frequency. Double immunohistochemistry revealed that the vast majority of noradrenergic nerve fibres also contained NPY. None of the noradrenergic nerve fibres showed the presence of VAChT or VIP. The possible functional significance of these findings is discussed.