Canine "honing" in Australopithecus afarensis

The maxillary canines of Australopithecus afarensis show a distal wear facet that extends from the apex of the crown to a point near the distal cingulum. Although these facets bear a superficial resemblance to the honing facets found on the projecting portions of the canines of other anthropoids, a more detailed examination provided in this paper shows that they are not homologous or functionally equivalent. The facets are not related to the use of the maxillary canine as a weapon or as an additional masticatory surface. Instead, their presence in A. afarensis represented a blunting or dulling of the posterior edge of C so that its occlusion with P3 would be consistent with cheek tooth occlusion.     

Estimating canine tooth crown height in early Australopithecus

Canine tooth size reduction and the associated reduction in canine dimorphism is a basal hominin character that also provides important evidence for models of behavioral evolution. Two specimens of Australopithecus anamensis (KNM-KP 29287 and KNM-KP 29283) that do not preserve the canine crown, but do preserve the root or alveolus, appear to suggest that canine size variation and canine dimorphism in this species may have been greater than in other hominins. We evaluate canine root and crown dimensions in a series of extant hominoids, and estimate canine crown height in Australopithecus afarensis and A. anamensis. Our results demonstrate that it is possible to generate estimates of canine crown height from basal canine crown and root dimensions with a moderate degree of accuracy. Estimates of maxillary canine crown size for A. anamensis are slightly larger than those of A. afarensis, and are approximately the same size as canines of modern female chimpanzees. Estimated mandibular canine crown height is very similar in the two species. Variation within the A. anamensis sample of estimated canine crown heights is similar to that of modern humans, suggesting a low degree of sexual dimorphism. Inclusion of estimates for KNM-KP 29287 and KNM-KP 29283 does not substantially increase either the estimate of overall canine size or variation for A. anamensis.     

Aberrant growth of maxillary canine teeth in male babirusa (genus Babyrousa)

A worldwide survey of babirusa skulls curated in museum and private collections located 431 that were from adult males and had retained at least one maxillary canine tooth. Eighty-three of these skulls were identified as exhibiting aberrant maxillary canine tooth growth. Twenty-four of the skulls represented babirusa from Buru and the Sula Islands, and forty-five skulls represented babirusa from Sulawesi and the Togian Islands. The remaining series of fourteen babirusa skulls originally came from zoo animals. Fifteen skulls showed anomalous alveolar and tooth rotation in a median plane. Twenty-nine skulls had maxillary canine teeth that did not grow symmetrically towards the median plane of the cranium. Fourteen skulls showed evidence that the tips of one or both maxillary canine teeth had eroded the nasal bones. Twenty-one skulls had maxillary canine teeth that had eroded the frontal bones. The teeth of two skulls had eroded a parietal bone. One skull had two maxillary canines arising from an adjacent pair of alveoli on the left side of the cranium. Three skulls exhibited alveoli with no formed maxillary canine teeth in them. Analysis suggested that approximately 12% of the adult male babirusa in the wild experience erosion of the cranial bony tissues as a result of maxillary canine tooth growth. There was no skeletal evidence that maxillary canine teeth penetrate the eye.     

A new rhynchosaur maxillary tooth plate morphotype expands the disparity of the group in the Ischigualasto Formation (Late Triassic) of Northwestern Argentina

Abstract

Rhynchosaurs are a clade of quadruped, herbivorous stem-archosaur diapsids restricted to the Triassic Period. The group became globally distributed and the numerically dominant tetrapods of several terrestrial ecosystems before their extinction. Derived rhynchosaurs are characterized by a specialized masticatory apparatus, composed of a blade-and-groove occlusion with multiple longitudinal maxillary tooth rows. The morphology of the maxillary tooth plate has shown to be taxonomically and phylogenetically informative. So far, two rhynchosaur maxillary tooth plate morphotypes are known in Argentina, one belonging to an unnamed stenaulorhynchine from the Chañares Formation and the other to the hyperodapedontine Hyperodapedon sanjuanensis, the single rhynchosaur species currently name for the Ischigualasto Formation. Here we describe a new rhynchosaur maxillary tooth plate morphotype based on an indeterminate hyperodapedontine specimen from the Ischigualasto Formation. This maxillary tooth plate (PVL 2728) possesses a single longitudinal groove that divides symmetric lateral and medial tooth-bearing areas with relatively large tooth crowns, which is an uncommon combination of features among hyperodapedontines. These qualitative observations in addition to quantitative analyses show that the morphology of PVL 2728 differs from that of, at least, other sampled South American rhynchosaurs. Therefore, this specimen expands the morphological disparity of rhynchosaurs in northwest Argentina and southwestern Pangaea.     

Investigation of effective intrusion and extrusion force for maxillary canine using finite element analysis

Abstract

Orthodontic tooth movement is mainly regulated by the biomechanical responses of loaded periodontal ligament (PDL). We investigated the effective intervals of orthodontic force in pure maxillary canine intrusion and extrusion referring to PDL hydrostatic stress and logarithmic strain. Finite element analysis (FEA) models, including a maxillary canine, PDL and alveolar bone, were constructed based on computed tomography (CT) images of a patient. The material properties of alveolar bone were non-uniformly defined using HU values of CT images; PDL was assumed to be a hyperelastic–viscoelastic material. The compressive stress and tensile stress ranging from 0.47 to 12.8?kPa and 18.8 to 51.2?kPa, respectively, were identified as effective for tooth movement; a strain 0.24% was identified as the lower limit of effective strain. The stress/strain distributions within PDL were acquired in canine intrusion and extrusion using FEA; root apex was the main force-bearing area in intrusion–extrusion movements and was more prone to resorption. Owing to the distinction of PDL biomechanical responses to compression and tension, the effective interval of orthodontic force was substantially lower in canine intrusion (80–90?g) than in canine extrusion (230–260?g). A larger magnitude of force remained applicable in canine extrusion. This study revised and complemented orthodontic biomechanical behaviours of tooth movement with intrusive–extrusive force and could further help optimize orthodontic treatment.     

New fossils of Australopithecus anamensis from Kanapoi,West Turkana,Kenya (2003–2008)

Renewed fieldwork from 2003 through 2008 at the Australopithecus anamensis type-site of Kanapoi, Kenya, yielded nine new fossils attributable to this species. These fossils all date to between 4.195 and 4.108 million years ago. Most were recovered from the lower fluvial sequence at the site, with one from the lacustrine sequence deltaic sands that overlie the lower fluvial deposits but are still below the Kanapoi Tuff. The new specimens include a partial edentulous mandible, partial maxillary dentition, two partial mandibular dentitions, and five isolated teeth. The new Kanapoi hominin fossils increase the sample known from the earliest Australopithecus, and provide new insights into morphology within this taxon. They support the distinctiveness of the early A. anamensis fossils relative to earlier hominins and to the later Australopithecus afarensis. The new fossils do not appreciably extend the range of observed variation in A. anamensis from Kanapoi, with the exception of some slightly larger molars, and a canine tooth root that is the largest in the hominin fossil record. All of the Kanapoi hominins share a distinctive morphology of the canine–premolar complex, typical early hominin low canine crowns but with mesiodistally longer honing teeth than seen in A. afarensis, and large, probably dimorphic, canine tooth roots. The new Kanapoi specimens support the observation that canine crown height, morphology, root size and dimorphism were not altered from a primitive ape-like condition as part of a single event in human evolution, and that there may have been an adaptive difference in canine function between A. anamensis and A. afarensis.     

Data on morphometric analysis of anterior teeth from Hazaribag College of Dental Sciences and Hospital,jharkhand

It is of interest to document data on morphometric (measurement of external form) analysis of maxillary and mandibular anterior teeth collected from a dental set up using mesio-distal (MD) dimension. The mesiodistal dimensions of all permanent anterior teeth (central incisor, lateral incisor and canine) of 25 males and 25 females patients were recorded using digital vernier calipers. Data were charted and statistical analysis was done using Mann Whitney U test. Data shows sexual dimorphism for every tooth between males and females. However, dimorphism was exhibited only in maxillary and mandibular canine, mandibular central incisors, and lateral incisor. Hence,odontometric parameters offer simple, reliable and cost-effective in forensic investigation for recording gender discrimination.     

Tooth morphology of Notosuchus terrestris (Notosuchia: Mesoeucrocodylia): New evidence and implications

Notosuchia is a large and diverse group of Crocodyliforms, characterized, among other features, by a heterodont dentition. New information on the tooth anatomy of Notosuchus terrestris is presented, based on well-preserved specimens from the Late Cretaceous of Patagonia (southern Argentina). This allows a complete characterization of its dental anatomy (composed by incisiviform, caniniform, and molariform teeth) that includes autapomorphic features and derived features shared with Sphagesaurus and Mariliasuchus. This includes the extensive wear facets in molariforms, indicative of tooth–tooth occlusion and a sharp keel that bears rounded denticles. Notosuchus also shares with Mariliasuchus the presence of a tooth with a transitional morphology located at the premaxilla–maxilla contact and the absence of interalveolar septa in the entire premaxillary and maxillary dentition.     

Cheek tooth erosion in male babirusa (genus Babyrousa)

The wear on the occlusal surfaces of male babirusa cheek teeth was evaluated in 53 skulls of Babyrousa babyrussa from Buru and the Sula Islands and 87 skulls of B. celebensis from Sulawesi, Indonesia. Based on the comparative lengths of their continually growing maxillary canine teeth, the skulls were divided into five ‘age categories’ (A–E). Numerical and symbolic codes representing tooth wear were applied to each pillar (cusp region) of the mandibular and maxillary permanent third and fourth premolar teeth, and the first, second and third permanent molar teeth. There was no significant difference between the tooth wear patters of skulls in groups A and B, or in groups C and D, and so these were amalgamated. There was close correspondence in wear patterns between each side of the mouth in both species and in each age group. The wear patterns of the mandibular and maxillary teeth, although not identical, were very similar, as were the wear patterns of both species. In group A + B for both species tooth wear was relatively slight, with the M1 teeth experiencing most relative wear. There was almost no wear of the M3 teeth. In group C + D substantial wear of upper and lower M1 was evident. In group E more widespread wear of the cheek teeth was seen, with increased severity of M1 tooth wear, yet there was comparatively much less M2 and M3 tooth wear. The pattern of cheek tooth wear of the Babyrousa spp. was different from that shown by Sus scrofa. Differences in diet selection and processing were highlighted as potential contributing factors. The pattern of cheek tooth wear in male babirusa was not adequate for use to monitor their age.     

Maxillary tooth growth in the adult male babirusa (genus Babyrousa)

The growth of the maxillary canine teeth of the babirusa (genus Babyrousa) was studied on a sample of 149 adult male babirusa skulls from twenty-two international museum and private collections. Skulls from Buru, Sulawesi and the Togian Islands were represented. The continuous growth process was summarised into five stages (‘A’–‘E’) according to the position of the tip of the tooth over the bones of the skull. The supracutaneous portion of the tooth grew in a curve-linear fashion dorso-caudally, and was orientated such that the tips grew towards the midline of the cranium. The teeth of Sulawesi and Togian babirusa grew more dorsally over the nasal and frontal bones. Measurements were made on a subset of 45 teeth from Sulawesi babirusa skulls. The subcutaneous portion of the maxillary canine tooth (n = 22) increased in size from 37.3 mm (95% CI: 29.9–44.4 mm) in growth stage ‘B’ to 54.3 mm (49.4–59.2 mm) in growth stage ‘E’ as the erupted portion of the tooth (n = 19) lengthened from 81.3 mm (43.8–118.9 mm) in growth stage ‘A’ to 215.3 mm (177.8–252.9 mm) in growth stage ‘E’. The apical end of the tooth was open and thin-walled. The lumen of the tooth was filled with a cone of well vascularised dental pulp that extended almost to the tip of the tooth. The angle of curvature of the tooth within the alveolus (n = 22) decreased from 19.8 (17.3–22.3) degrees in growth stage ‘B’ to 7.4 (5.7–9.0) degrees in growth stage ‘E’. The corresponding supracutaneous angle of curvature (n = 25) reduced from 36.8 (33.6–40.1) degrees in growth stage ‘A’ to 10.7 (8.6–12.8) degrees in growth stage ‘E’.     

Unicausal theories of human canine evolution: are they sufficient?

Most theories of human canine evolution are unicausal and only purport to explain size and related shape changes in human canines. The present work tests whether one of the morphological changes, dulling of the distal edge of the maxillary canine, can be entirely explained as a byproduct of changes in the overall shape of the canine. The data show that the distal edge of maxillary canines of A. afarensis became far duller than would be predicted from changes in crown shape. The greater than expected dullness of the distal edge can be explained by evolutionary changes in the genetic field for cheek tooth morphology. This suggests that human canine evolution is complex and cannot be accounted for by unicausal theories.     

Static intraspecific allometry of jaws and teeth in Cercopithecus aethiops

Adult static intraspecific allometry of jaw size and tooth area was evaluated in a sample of 100 Cercopithecus aethiops crania (50 male, 50 female). Tooth areas were calculated from mesiodistal and buccolingual measurements of all the teeth in both arcades and were scaled to four viscero-cranial measurements: bimaxillary breadth, maxillo-alveolar length, mandibular length and bigonial width. Allometric coefficients calculated for jaw dimensions alone indicate tighter viscerocranial integration in females than in males. A finding of note was that half of the variation in maxillo-alveolar length may be accounted for by variation in mandibular length: females are isometric, males negatively allometric.
A similar degree of allometric mosaicism was found when maxillary incisor size was scaled to maxillary length and width. In females, the relationship was negatively allometric, whilst incisor size in males was found to be unrelated to either. Negative allometry characterized the relationship of canine base area to jaw length in both sexes, with males additionally being positively allometric to mandibular width.
The scaling of postcanine tooth areas to jaw length was characterized by a dichotomous pattern: males showed significant mandibular integration whilst females showed only significant maxillary integration. Compensatory tooth size interaction between maxillary canine base area and the summed incisor and postcanine areas was suggested by the significant negative allometric relation between them.     

The distribution of pheromone-biosynthesis-activating neuropeptide (PBAN) immunoreactivity in the central nervous system of the corn earworm moth,Helicoverpa zea

Summary Production of sex pheromone in several species of moths has been shown to be under the control of a neuropeptide termed pheromone-biosynthesis-activating neuropeptide (PBAN). We have produced an antiserum to PBAN from Helicoverpa zea (Lepidoptera: Noctuidae) and used it to investigate the distribution of immunoreactive peptide in the brain-suboesophageal ganglion complex and its associated neurohemal structures, and the segmental ganglia of the ventral nerve cord. Immunocytochemical methods reveal three clusters of cells along the ventral midline in the suboesophageal ganglion (SOG), one cluster each in the presumptive mandibular (4 cells), maxillary (12–14 cells), and labial neuromeres (4 cells). The proximal neurites of these cells are similar in their dorsal and lateral patterns of projection, indicating a serial homology among the three clusters. Members of the mandibular and maxillary clusters have axons projecting into the maxillary nerve, while two additional pairs of axons from the maxillary cluster project into the ventral nerve cord. Members of the labial cluster project to the retrocerebral complex (corpora cardiaca and cephalic aorta) via the nervus corpus cardiaci III (NCC III). The axons projecting into the ventral nerve cord appear to arborize principally in the dorsolateral region of each segmental ganglion; the terminal abdominal ganglion is distinct in containing an additional ventromedial arborization in the posterior third of the ganglion. Quantification of the extractable immunoreactive peptide in the retrocerebral complex by ELISA indicates that PBAN is gradually depleted during the scotophase, then restored to maximal levels in the photophase. Taken together, our findings provide anatomical evidence for both neurohormonal release of PBAN as well as axonal transport via the ventral nerve cord to release sites within the segmental ganglia.Abbreviations A aorta - Br-SOG brain-suboesophageal ganglion complex - CC corpus cardiacum - PBS phosphate-buffered saline - PLI PBAN-like immunoreactivity - TAG terminal abdominal ganglion - VNC ventral nerve cord     

Functional and phylogenetic significance of integrated growth and form in occluding monkey canine teeth (Alouatta caraya and Macaca mulatta)

Crown-root lengths in paired apposing, functionally interacting monkey canine teeth (Alouatta caraya and Macaca mulatta) are highly correlated throughout their concurrent development. Regression is rectilinear and growth pattern accretional. The differential growth rate is not significantly different in the sexes within each species during concurrent tooth pair development. These integrated morphological characteristics are adaptations to functional needs imposed by jaw anatomy and masticatory dynamics. Divergence from rectilinearity occurs in the mature male Macaca mulatta with the continued growth of the maxillary canine fang after cessation of growth of the apposing mandibular canine tooth. This altered tooth pair crown-root length relationship is associated with the subordination of mastication in these predominantly piercing and slashing teeth. Species differences in regression are significant and afford insight into possible preadaptive factors determining divergent paths in the evolution of canine tooth sexual dimorphism.     

Morphogenetic experiments in facial asymmetry: the nasal cavity

An experiment was designed to test the response of the nasal cavity and associated structures to maxillary deformity. Forty young M. mulatta were surgically produced in 20 animals, and the small maxillary segments moved medialward. Intrapair observation tests were applied to selected measurements and indices of symmetry relationships. Deformity of the surgically undisturbed nasal septum occurred in response to the maxillary deformation. The lateral walls were moved medially with the maxilla, but in six months symmetry relationships were similar to those found in the control animals. The lateral walls of the nasal cavity appeared to be relatively independent of the shape and position of the tooth carrying part of the maxilla. The development and use of primate models can contribute to understanding the extent of the adaptational response systems in facial morphogenesis.     

Tooth eruption in Reeves' muntjac (Muntiacus reevesi) and its use as a method of age estimation (Mammalia: Cervidae)

The sequence of tooth eruption and replacement in Reeves' muntjac was determined from captive animals of known age. Pronounced sexual dimorphism is shown by the permanent upper canine which in the male is large, tusk-like and is used as a weapon. The upper canine was the first deciduous tooth to be replaced in males, at approximately 21 weeks of age, compared with 53–57 weeks in the female. The permanent mandibular teeth erupted in the order: molars, first and second incisors, premolars, third incisor and canine. The maxillary teeth erupted in the order: first molar, canine (in male), second and third molars, canine (in female), premolars. The full complement of 34 functional permanent teeth was attained by 83–92 weeks of age.     

Premaxillary-maxillary suture asymmetry in a juvenile Gorilla. Implications for understanding dentofacial growth and development

A specimen of juvenile gorilla was found that had the premaxillary-maxillary suture coursing between the lateral deciduous incisor and deciduous canine on one side of the jaw, but between the central and lateral deciduous incisors on the other; in the latter, the suture also separates the alveolus of the lateral deciduous incisor from the crypt of the growing successional lateral incisor. Rather than dismiss this exception to the traditional dictum of tooth identification--which is based on the position to teeth relative to this suture--as some inconsequential anomaly, an attempt is made to understand how this can occur within the confines of present understanding of dentofacial growth and development and developmental theory. An hypothesis relating tooth and tooth class identification is presented in the context of ectomesenchymally predifferentiated stem progenitors and subsequent tooth class proliferation.     

Studies on agenesis in the permanent dentition

Tooth dimensions in 104 males and females with agenesis of one or more permanent teeth, other than third molars, have been examined. The amounts of size reduction from normal in mesiodistal and buccolingual tooth diameters appear to be independent. Also some apparent differences from normal tooth size variability were noted. Interestingly, first molars and canines, both considered to be stable components of the dentition, showed significant variability in tooth size. In addition the incidence of individual tooth agenesis within this sample was noted and maxillary lateral incisor was most frequently absent in both sexes.     

Brief communication: Additional cases of maxillary canine‐first premolar transposition in several prehistoric skeletal assemblages from the Santa Barbara Channel Islands of California

This article identifies and discusses seven new cases of complete maxillary canine‐premolar transposition in ancient populations from the Santa Barbara Channel region of California. A high frequency of this tooth transposition has been previously documented within a single prehistoric cemetery on one of the Channel Islands. A total of 966 crania representing 30 local sites and about 7,000 years of human occupation were examined, revealing an abnormally high prevalence of this transposition trait among islanders during the Early period of southern California prehistory (～5500–600 B.C.). One of the affected crania is from a cemetery more than 7,000‐years‐old and constitutes the earliest case of tooth transposition in humans so far reported. The results are consistent with findings by other studies that have indicated inbreeding among the early Channel Islands groups. Together with the normal transposition rates among mainland populations, the decreasing prevalence of maxillary canine‐first premolar transposition among island populations across the Holocene suggests that inbreeding on the northern Channel Islands had all but ceased by the end of the first millennium B.C., most likely as a result of increased cross‐channel migration and interaction. Am J Phys Anthropol 143:155–160, 2010. © 2010 Wiley‐Liss, Inc.     

Brief communication: Identification reassessment of the isolated tooth Krapina D58 through occlusal fingerprint analysis

High variability in the dentition of Homo can create uncertainties in the correct identification of isolated teeth. For instance, standard tooth identification criteria cannot determine with absolute certainty if an isolated tooth is a second or third maxillary molar. In this contribution, using occlusal fingerprint analysis, we reassess the identification of Krapina D58 (Homo neanderthalensis), which is catalogued as a third maxillary molar. We have hypothesized that the presence/absence of the distal occlusal wear facets can be used to differentiate second from third maxillary molars. The results obtained confirm our hypothesis, showing a significant difference between second and third maxillary molars. In particular we note the complete absence of Facets 7 and 10 in all third molars included in this analysis. The presence of these facets in Krapina D58 eliminates the possibility that it is a third maxillary molar. Consequently it should be reclassified as a second molar. Although this method is limited by the degree of dental wear (i.e., unworn teeth cannot be analyzed) and to individual molars in full occlusion, it can be used for tooth identification when other common criteria are not sufficient to discriminate between second and third maxillary molars. Am J Phys Anthropol 143:306–312, 2010. © 2010 Wiley‐Liss, Inc.