Finite element analysis of equine incisor teeth. Part 1: determination of the material parameters of the periodontal ligament.

In equine dentistry, periodontal diseases are frequently found in aged horses. Excessive strains and stresses within the periodontal ligament (PDL) occurring during the masticatory cycle may be predisposing factors especially in old horses with short, worn teeth. The finite element (FE) analysis is a valuable tool to investigate such strains and stresses in biological materials but a precondition for a realistic and reliable FE analysis is accurate knowledge of material parameters. As no data exist concerning the PDL of equine incisor teeth, this study was undertaken to determine the equine specific, age related and load dependent Young's modulus of equine incisors. To determine the biomechanical behaviour of the PDL, the incisor jaw-regions of horses of different ages were sectioned into 5mm thick slice samples and the incisors experimentally intruded (i.e. axially displaced into the alveolus) while recording the load-displacement relationship. Based on high resolution micro-computer tomography (µCT)-datasets, reliable and detailed 3-dimensional models of the slice samples were constructed focusing on precisely modelling the anatomy of the PDL. FE calculations were then performed and set-actual comparisons of the FE results with the experimentally measured displacements enabled the Young's modulus of the PDL to be determined. The results of this study reflect the typical non-linear behaviour of the collagen fibres of the PDL and present a high load dependency of the PDL's Young's modulus. Further investigations calculating the strains and stresses within the periodontal ligament, teeth and surrounding bone of the entire rostral aspect of the jaw are warranted.

Finite element analysis of equine incisor teeth. Part 2: investigation of stresses and strain energy densities in the periodontal ligament and surrounding bone during tooth movement.

This study investigated the hypothetical contribution of biomechanical loading to the onset of equine odontoclastic tooth resorption and hypercementosis (EOTRH) and to elucidate the physiological age-related positional changes of the equine incisors. Based on high resolution micro-computed tomography (µCT) datasets, 3-dimensional models of entire incisor arcades and the canine teeth were constructed representing a young and an old incisor dentition. Special attention was paid to constructing an anatomically correct model of the periodontal ligament (PDL). Using previously determined Young's moduli for the equine incisor PDL, finite element (FE) analysis was performed. Resulting strains, stresses and strain energy densities (SEDs), as well as the resulting regions of tension and compression within the PDL and the surrounding bone were investigated during occlusion. The results showed a distinct distribution pattern of high stresses and corresponding SEDs in the PDL and bone. Due to the tooth movement, peaks of SEDs were obtained in the PDL as well as in the bone on the labial and palatal/lingual sides of the alveolar crest. At the root, highest SEDs were detected in the PDL on the palatal/lingual side slightly occlusal of the root tip. This distribution pattern of high SEDs within the PDL coincides with the position of initial resorptive lesions in EOTRH affected teeth. The position of high SEDs in the bone can explain the typical age-related alteration of shape and angulation of equine incisors.

Isolation and identification of Porphyromonas spp. and other putative pathogens from cats with periodontal disease.

The purpose of this study was to evaluate the subgingival microbiota and determine the most prevalent periodontal pathogens implicated in feline periodontal disease and to correlate these findings with the clinical periodontal status. Subgingival microbiological samples were taken under sedation from 50 cats with clinical signs of periodontal disease. Pooled paper point samples from 4 selected subgingival sites were cultured on blood agar and on Dentaid-1 medium. Suspected pathogens were identified, subcultured, and preserved. The association between the microbiological findings and the clinical status was studied using correlation coefficients (CC). In addition, cats were stratified in subgroups according to presence of putative pathogens, and comparisons were carried out using unpaired t-test. Three bacterial species were frequently detected including Porphyromonas gulae (86%), Porphyromonas circumdentaria (70%) and Fusobacterium nucleatum (90%). The mean proportion of total flora was high for P. gulae (32.54%), moderate for P. circundentaria (8.82%), and low for F. nucleatum (3.96%). Among the clinical variables, tooth mobility was correlated (CC > 0.50, p < 0.001) with recession, pocket depth, attachment level, gingival index, and calculus index (CC = 0.29, p = 0.04) as well as with total bacterial counts (CC = 0.38, p = 0.006). Cats with more than 10% of P. gulae showed significantly more mobility (p = 0.014) and recession (p = 0.038), and a tendency for deeper probing pocket depths (p = 0.084) and attachment loss (p = 0.087). The results from this cross-sectional study confirmed that P. gulae is the most relevant pathogen in periodontal disease in cats.

The development of an oral health charting system for koalas (Phascolarctos cinereus).

The koala is one of Australia's most highly specialized folivores with a diet exclusively of eucalyptus leaves to provide all nutritive needs and therefore requires to be free of oral disease as they are dependent on good dentition for optimal health and quality of life. We developed an oral examination methodology based on protocols for companion animals and human dentistry to chart the oral health of koalas. Thirty free-ranging koalas from South-East Queensland, Australia were examined for general body and oral health. Inspection of the oral cavity was conducted for the presence or absence of the indicators oforal disease such as caries or periodontal disease. Univariate and multivariate analyses were performed on the examination data and a prototype oral health chart developed. The prototype was then trialled and the methodology validated by the Kappa statistic using ten additional koalas examined by four multidisciplinary personnel involved in koala care. Trauma associated fractures, tooth displacement, abnormal occlusion and tooth wear compacted vegetation, extrinsic stain deposits, periodontal bone loss, gingivitis, tooth mobility, and calculus were present in the oral cavities of the examined koalas. A system of scoring between 0 and 3 was constructed in accordance with current koala general health charting formats. Validation of the charting method using Kappa coefficients of agreement statistics indicated that there was a good agreement among observers on recorded results except for inflammation and calculus scoring. Modifications were made and visual aids and index scales produced to further assist observers. Oral health surveillance has been proven in other species to be significant in diagnosing physiological disturbances derived from environmental genetic, and developmental causes. Veterinarians, dental researchers, and koala husbandry personnel will benefit in using this charting method and reporting the oral health of koala populations in their future findings. This unique form of oral health monitoring would be adaptable to other mammals.

Surgical extractions for periodontal disease in a Western Lowland gorilla.

This case report describes surgical exraction of multiple premolar and molar teeth in a Western Lowland gorilla. Postoperative photographs and radiographs indicated complete healing of the extraction sites. This case report includes a review of gorilla dental anatomy, oral disease in primates, pathogenesis of periodontal disease, predisposing factors to periodontal disease, and principles of surgical tooth extraction.

Nasal displacement of a tooth root in a dog.

A ten-year-old miniature Dachshund dog was presented for chronic paroxysmal sneezing and unilateral nasal discharge. Extraction of the maxillary right fourth premolar tooth had been performed 2-weeks prior to the onset of clinical signs. Multiple diagnostic modalities were used to confirm the diagnosis and determine that the etiology was a nasally displaced mesiopalatal tooth root. A limited lateral rhinotomy was performed to remove the root. Postoperative examination 1-month following surgery indicated resolution of the clinical signs and uncomplicated healing of the surgery site. Oral examination indicated normal healing of the surgery site with continued absence of clinical signs 6-months after treatment.

Induced elephant (Loxodonta africana) tusk removal.

Elephant tusk removal usually requires costly surgical procedures that are time-consuming and present a significant risk to the animal when performed using general anesthesia. Such techniques require gauges, chisels, and forceps to remove the tusk. This article reports the simple removal of the tusk of an 18-yr-old African elephant (Loxodonta africana) without the use of surgical instruments and anesthesia. Rubber elastics were placed around a tusk, causing loss of alveolar bone with subsequent exfoliation of the tusk within 3 wk. The healing process was uneventful.

Oral malodor in beagles: association with indicators of periodontal disease.

The study of oral malodor continues to receive attention. Most bad breath is of oral origin and can be corrected with proper oral hygiene. Studies performed with saliva from people with periodontal disease and from healthy individuals showed that saliva from diseased patients produced a more objectionable odor faster than that of healthy people, and that the volatile sulfur components (VSC) produced may actually play a role in the etiology of periodontal disease. However, not all people or animals with bad breath have periodontal disease. The objectives of this study were to determine if a trained panel could discriminate between 10 dogs with clinically defined periodontal disease and those with relatively healthy periodontium. Second, this study attempted to establish a correlation between odor intensity and six clinical parameters of oral health. The judges were able to differentiate between the two groups of dogs based only on oral malodor (p < 0.02). There were strong associations of the intensity of oral malodor with oral health index scores. The correlations established between odor and gingivitis (r = 0.81) and between odor and furcation exposure (r = 0.88) were very high and statistically significant. Similarly, probing depth (r = 0.73), plaque (r = 0.07) and tooth mobility (r = 0.66) showed clear, positive relationships with oral malodor.

Renal dysplasia with secondary hyperparathyroidism and loose teeth in a young dog.

In a dog with renal dysplasia and secondary hyperparathyroidism, loose teeth resulted from excessive resorption of alveolar bone. Sharpey's fibers, still anchored in the cementum, were lost in the replacing fibrous tissue and few fibers found their way to distant bone fragments. The alveolar bone is the site of predilection for the excessive, generalized resorption of bone in hyperparathyroidism. Clinical radiographic examination of the jaws is a valuable tool in the detection of the disease.

Tooth splinting for severely mobile mandibular incisor teeth in a dog.

Periodontal disease, in its advanced stages, causes tooth mobility. The tooth movement further damages the periodontium, accelerating the disease process leading to tooth loss. Dental splinting can provide coaptive stability to the teeth as an important component of a periodontal treatment plan. This report documents results four years following splinting of the mandibular incisor teeth in a 3 year old Miniature Schnauzer dog.

Effects of inflammatory periodontal disease ('broken mouth') on the mobility of the sheep incisor.

Loads directed linguolabially and between 0.01 N and 0.2 N were applied to a mandibular central incisor in each of 12 four-year-old ewes with evidence of inflammatory periodontal disease ('broken mouth'). For every incisor, tooth position was monitored continuously with an ultrasonic displacement transducer. Each load chosen was suddenly applied and then maintained for five minutes, producing a biphasic, viscoelastic-like response (a phase of rapid displacement being followed by a more gradual phase of creep). A similar biphasic recovery response was seen on suddenly removing the load. Comparing the findings with those obtained in a previous study for incisors in healthy dentitions, there was a considerable increase in mobility with inflammatory periodontal disease. Surprisingly, however, the patterns of the responses did not differ. The reason for the change in the amount of mobility may be related simply to the quantity of the tooth supporting tissues which is lost, although there is some evidence that qualitative changes occurring in these tissues may also be important.

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').

Clinical signs and treatment of aged sheep with loose mandibular or maxillary cheek teeth.

Five cases of loose mandibular or maxillary cheek teeth in sheep are described. All the sheep showed loss of condition but excessive salivation was not a consistent feature. Two had high helminth egg counts, one a facial abscess and three loose rostral teeth. Blood biochemical results showed raised creatine phosphokinase (three cases), low glucose (three) and marginally low calcium levels (two). Diagnosis was based on digital palpation of the teeth during sedation. Treatment by extraction of loose teeth allowed a further litter of lambs from pregnant ewes and an extra tupping season from a ram.

Application of the radiological sciences to advance clinical and fundamental knowledge of the animal kingdom. New Horizons for Radiologists Lecture.

Many radiological techniques are useful in fundamental research. Selected clinical problems in animals as well as certain basic research projects are utilized to emphasize the potential of radiological imaging. The author describes the use of several radiological methods in studies of how birds breathe.