Measurement of Incisor Overjet and Physiological Diastemata Parameters in Quarter Horse Foals.

Cephalometric studies are important to quantify abnormalities of jaw length and positioning. In this study, 4 to 7-month-old Quarter horse foals (n = 51) were examined to determine overjet (horizontal overlap) prevalence and measure the size of the physiological diastemata. Results were analyzed in relation to age, sex, and lineage. Another aim of this study was to develop a simple field technique for measuring incisor malocclusion and physiological diastemata dimensions that could be used to monitor the growth of the rostral components of maxilla, incisive bone, and mandible. The overall prevalence of overjet lesions in these foals was 51%. Females were overrepresented (61.5%). Overjet occurred more commonly in show foals (50% prevalence) than other working (7.7%) and race (42.3%) lineage foals. Significant differences were found between maxillary and mandibular physiological diastemata lengths in foals of all ages and, as expected, there was a positive statistical correlation between age and maxillary and mandibular physiological diastemata measurements. Incisor overjet was present in 44.4% of 4-month-old foals, 45.5% of 5-month-old foals, 58.3% of 6-month-old foals, and 60% of 7-month-old foals. There was a weak positive correlation between age and the presence of incisor overjet. It was concluded that incisor overiet was common among Quarter horse foals, especially those from show and race lineages. The field technique for physiological diastema measurements was considered effective.

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.

Markers of physiological stress in juvenile bonobos (Pan paniscus): are enamel hypoplasia, skeletal development and tooth size interrelated?

A reduction in enamel thickness due to disrupted amelogenesis is referred to as enamel hypoplasia (EH). Linear EH in permanent teeth is a widely accepted marker of systemic physiological stress. An enigmatic, nonlinear form of EH commonly manifest in great ape and human deciduous canines (dc) is known as localized hypoplasia of primary canines (LHPC). The etiology of LHPC and what it signifies-localized traumatic or systemic physiological stress-remains unclear. This report presents frequency data on LHPC, hypostotic cranial traits, and tooth size in a sample of juvenile bonobos, then tests hypotheses of intertrait association that improve knowledge of the etiology and meaning of LHPC. The fenestration hypothesis is tested using hypostotic cranial traits as a proxy for membrane bone ossification, and the relationship between tooth size, LHPC, and hypostosis is investigated. Macroscopic observations of EH, hypostotic traits, and measurements of buccolingual tooth size were conducted according to established standards. LHPC was found in 51.2% of bonobos (n = 86) and in 26% of dc teeth (n = 269). Hypostotic traits were observed in 55.2% of bonobos (n = 96). A test of the association between LHPC and hypostosis yielded nonsignificant results (chi(2) = 2.935; P = 0.0867). Primary canines were larger in specimens with LHPC than in unaffected specimens (paired samples t test; udc, P = 0.011; ldc, P = 0.018), a result consistent with the fenestration hypothesis of LHPC pathogenesis. Hypostosis was not associated with differences in tooth size (P > 0.05). LHPC may be an indirect indicator of physiological stress, resulting from large, buccally displaced primary canines.

Bigger teeth for longer life? Longevity and molar height in two roe deer populations.

The role of tooth wear as a proximate cause of senescence in ruminants has recently been highlighted. There are two competing hypotheses to explain variation in tooth height and wear; the diet-quality hypothesis predicting increased wear in low-quality habitats, and the life-history hypothesis predicting molar height to be related to expected longevity. We compared tooth height and wear from roe deer of known age from two contrasting populations of roe deer (Capreolus capreolus) in France: Trois Fontaines (TF) with good habitat and shorter animal life expectancy and Chizé (CH) with poor habitat and longer animal life expectancy. There was no population difference in tooth wear, leading to rejection of the diet-quality hypothesis. However, despite their smaller body size, initial molar height for animals from CH was larger than for animals from TF. This provides the first evidence that variation in longevity between populations can lead to differences in molar height within a species.

Dental topography and molar wear in Alouatta palliata from Costa Rica.

Paleoprimatologists depend on relationships between form and function of teeth to reconstruct the diets of fossil species. Most of this work has been limited to studies of unworn teeth. A new approach, dental topographic analysis, allows the characterization and comparison of worn primate teeth. Variably worn museum specimens have been used to construct species-specific wear sequences so that measurements can be compared by wear stage among taxa with known differences in diet. This assumes that individuals in a species tend to wear their molar teeth in similar ways, a supposition that has yet to be tested. Here we evaluate this assumption with a longitudinal study of changes in tooth form over time in primates. Fourteen individual mantled howling monkeys (Alouatta palliata) were captured and then recaptured after 2, 4, and 7 years when possible at Hacienda La Pacifica in Costa Rica between 1989-1999. Dental impressions were taken each time, and molar casts were produced and analyzed using dental topographic analysis. Results showed consistent decreases in crown slope and occlusal relief. In contrast, crown angularity, a measure of surface jaggedness, remained fairly constant except with extreme wear. There were no evident differences between specimens collected in different microhabitats. These results suggest that different individual mantled howling monkeys wear their teeth down in similar ways, evidently following a species-specific wear sequence. Dental topographic analysis may therefore be used to compare morphology among similarly worn individuals from different species.

Evaluation of electronic method in determining the root canal length in teeth of dogs.

The aim of this study was to investigate the efficacy of electronic apex locators to determine the root canal length in teeth of dogs. For this purpose, APIT and ENDOSONIC units, which are third generation apex locator devices, were used to identify the root length in 58 teeth (82 roots). The electronic method was compared to radiographic and tactile sense methods. The results showed that APIT and ENDOSONIC devices were ineffective when used to determine the root canal length in 2-3 year-old dogs. A beep indicating the canal depth was heard in only two of 82 (2.4%) canals. The digital-tactile sense method with radiographic confirmation is more appropriate for root length measurement than the electronic method during endodontic therapy in dogs.

An evaluation of the accuracy of ageing horses by their dentition: a matter of experience?

There is a widely held belief that a horse can be accurately aged by an examination of its teeth but this belief has recently been questioned. In this study photographs were taken of the dentition of 434 thoroughbreds of known age. Four experienced equine clinicians provided estimates of the ages of the horses from the photographs. A comparison of the estimated and true ages showed large discrepancies in many cases and the discrepancies increased as the horse's true age increased. The results show that the ageing of horses from their dentition is an imprecise science. It is suggested that written records of the dental features are made on each occasion when a dental examination is made and that veterinary surgeons advise clients that estimating a horse's age from dental criteria can provide no more than an 'informed guess'.

An evaluation of the accuracy of ageing horses by their dentition: changes of dental morphology with age.

Dental features are commonly expected to provide an accurate estimate of a horse's age. In this study the dentition of 434 thoroughbreds was photographed and the individual dental features documented, the true age of all the horses was known. For each dental feature the correlation with true age was determined. The eruption of the incisor teeth was the most consistent feature but it was not totally reliable. The presence of a hook on the upper corner incisor and Galvayne's groove proved to be of no value when estimating age and, of the attritional features studied, the dental star showed the highest correlation with age. The results show that specific ages cannot be assigned to these dental criteria owing to the wide variation between horses, and that as a result the estimation of age from dentition can never be precise.

Dental variation in the genus Pan.

Dental measurements and 23 anatomical dental features are observed on 151 Pan troglodytes and 69 Pan paniscus of both sexes, preserved in the Museum of Tervuren (Belgium). Odontometric investigations confirm the reality of the two species in the genus Pan, but do not show any difference between subspecies in Pan troglodytes. Correspondence analysis demonstrates that the qualitative anatomical features are differently distributed in the two chimpanzee species.

Canine tooth size variability in primates.

I present an analysis of canine tooth size variability in male and female primates. The coefficient of variation (CV = SD X 100/mean) as an index of canine size variability proved to be dependent on mean canine size in males and, to a lower extent, in females. Therefore, variability tends to increase with increasing values of mean canine size. Using residuals from the regression of log SD on log mean canine size in male and female primates, I analysed the contribution of diet, habitat and mating system to canine size variability. Habitat and mating system are known to influence to a certain extent the degree of sexual dimorphism in canine size. Given the well-known relationship between sexual dimorphism and phenotypic variability, it was suggested that these factors might influence variability in canine size. Everything else being equal, males of polygynous species are characterized by more variable canine sizes than males of monogamous species. Habitat and diet did not contribute to the level of variability observed in either males or females. It is proposed that a high level of variability in canine size may be related to the likelihood that enlarged canines evolved as a result of male-male competition for mates in polygynous species.

The relationship of tooth size to body size in a population of rhesus monkeys (Macaca mulatta).

Tooth areas correlate significantly with long bone measurements in a skeletal population of rhesus monkeys from Cayo Santiago. Correlations are relatively large for the troop as a whole, as well as for males and females separately. Femur and humerus length measurements show the higheres correlations with tooth size.