Shape components of the maxillary molars in Australian aboriginals

Principal components analysis was used to quantify the variability in crown outlines of maxillary molars in Australian Aboriginals. The outlines were measured by 36 radii from the central pit to the crown periphery. The first component, responsible for over half of the total variance, was concerned with general crown size. Four remaining components were retained to indicate sources of variability resulting from contrasting degrees of development or reduction of different crown components. Shape changes from the first to third molars were identified with components representing overall size reduction, diminution of the hypocone, and metacone elements and mesiodistal compression. An anteroposterior gradient along the molar series in average scores and variances for all components resulted from the progressive reduction of distal crown elements, increasing mesiodistal compression, and greater morphological variation.     

Canadian Eskimo permanent tooth emergence timing

To identify the times of emergence of the permanent teeth of Canadian Eskimos (Inuit), 368 children and adolescents were examined. The presence or absence of all permanent teeth except the third molars was recorded and these data subjected to probit analysis. Female emergence times were advanced over males. Generally, the Inuit of both sexes showed statistically significant earlier emergence times than Montreal children, except for the incisors. The present results do not support hypotheses indicating that premature extraction of the deciduous teeth advances the emergence of their succedaneous counterparts. There is some indication the controls of deciduous tooth emergence continue to play some part in emergence of the permanent dentition, especially the first permanent teeth that emerge.     

Probit and survival analysis of tooth emergence ages in a mixed-longitudinal sample of chimpanzees (Pan troglodytes).

Tooth emergence data from a mixed-longitudinal sample of 58 chimpanzees of known age were analyzed using probit and survival techniques to produce median emergence ages, ranges of variability, and emergence sequences for primary and permanent teeth. Between-group comparisons were made to test for statistically significant differences in emergence ages. No such differences were found between right and left sides, or between maxilla and mandible, for any primary or permanent teeth. Male-female comparisons did demonstrate significant emergence-age differences for some teeth, although they were not always bilaterally symmetrical. More complete data are required to further clarify the nature of sex differences in tooth emergence in chimpanzees. Regression models for age prediction from the number of emerged teeth were generated and indicate that males achieve a given number of emerged teeth at a significantly later age than females. However, when fewer than five teeth have emerged, males are predicted to be younger than females. The sizable root mean square error values for these models suggest that this method of age prediction has limited usefulness owing to the amount of variability in timing of tooth emergence in chimpanzees. The implications of these data for studies on tooth emergence in early hominids are addressed.     

Congenital defects of the upper lateral incisors: Multivariate analysis of measurements of the other teeth,the superior arch,head and face

The survey of a French male population allowed us to ascertain 75 propositi with one or two missing ULI, 59 propositi with one or two reduced ULI and 99 controls on whom measurements (mesiodistal and buccolingual diameters) of all teeth of the superior arch are available. Principal Component Analysis gave a first estimated principal component highly correlated with each of the dental measurements or arch measurements. This size factor was eliminated by observing the plane of the second and third principal components. Strikingly different clusters of MD diameters or BL diameters were observed for the controls, the propositi missing one or two of the ULI and the propositi with reduced ULI. For the controls, the arch length is correlated with the MD molar diameters and the MD incisor diameter, the arch width being isolated from the other measurements. For the propositi with missing ULI, among the dental measurements the MD and BL diameters cluster, the arch length is isolated as are the arch widths. For the propositi with reduced ULI, the arch length is closer to the dental measurements while the widths, especially the first one, are isolated. The best discriminant measurements are the diameters of the first premolars and the canine, the first arch width and the arch length. Among controls, the arch is narrowed and shorter for the propositi with absence and wider for the propositi with reduction. Teeth measurements are always smaller in propositi.     

Association of relatively delayed emergence of mandibular molars with molar reduction and molar position

Among 234 children examined annually from age three to 20 years at the Burlington Growth Centre, there was statistically significant cooccurrence of early and late emergence sequences of the permanent first and second molars relative to the central incisors and second premolars in the same jaw and in both jaws. Alternatively, mandibular molar delay was not accompanied by corresponding maxillary molar delay, and the mandibular molars emerged later than the maxillary molars. This was strongly associated with Angle Class II malocclusion, indicating a relationship between relative time of emergence and relative position of opposing molars. Delay of the mandibular molar relative to the successional teeth or maxillary molars was associated with increased frequency of four cusped first and second molars and agenesis of third molars, indicating a tendency for co-occurrence of delay in timing of molar emergence with reduction in structure of the molars. These relationships were evident even though emergences were affected by early loss of a deciduous second molar which increased M1I1 and M2P2 sequences by earlier emergence of M1 and delayed emergence of P2.     

More lingual surface attrition of the maxillary anterior teeth in American Indians: prehistoric Panamanians

Lingual surface attrition of the maxillary anterior teeth (LSA-MAT) has been found in additional prehistoric Latin American Indian skeletons. LSAMAT was first observed in crania from an Archaic Brazilian site. This second finding occurs in teeth from Venado Beach, a late prehistoric site in Panama. LSAMAT is also present in some fragmentary specimens from the Archaic Cerro Mangote site in Panama. LSAMAT at Venado Beach is present in 57% of 28 adult crania. As in the Brazilian study, LSAMAT is associated with a high caries rate (82% of 50 adults; 11.7% of 852 permanent teeth). As first suggested, eating and processing of some type of abrasive carbohydrate food, such as manioc, is the possible cause of LSAMAT. However, other possible causes relating to habitation on or near marine coasts cannot be totally ruled out.     

The role of lead and cadmium in deciduous teeth and saliva on dental caries in children residing in Tehran,Iran

BackgroundLead (Pb) and Cadmium (Cd) are important environmental contaminants. There is no biological monitoring of exposure to these heavy metals and their potential effect on dental caries in children in Tehran, Iran, a polluted megacity. Therefore, the present study investigated the potential association between Pb and Cd levels in primary teeth and saliva and dental caries.MethodsIn a cross-sectional design, 211 children aged 6–11 years referred to Tehran University of Medical Sciences, School of Dentistry and residing in Tehran were examined. Pb and Cd levels of exfoliated primary teeth and stimulated saliva were determined by atomic absorption spectrophotometry (AAS). Dental caries prevalence was evaluated according to WHO criteria. Socioeconomic status, oral hygiene behavior, snacking frequency and salivary pH data were acquired as confounding factors. Frequency and percentages were reported for categorical variables, mean and standard deviation (SD) for continuous variables, and geometric mean for skewed continuous variables. A simple linear regression and Pearson correlation tests were used for statistical analyses. P-values < 0.05 were considered as significant.ResultThe mean (95 % confidence interval) Pb and Cd levels in teeth were 213.26 ppb (164.29–274.84) and 23.75 ppb (20.86–27.05), respectively. The mean Pb and Cd levels in saliva were 11.83 ppb (10.71–13.06) and 3.18 ppb (2.69–3.75), respectively. Furthermore, Pb and Cd in primary teeth and saliva were not associated (p > 0.05) with socioeconomic status, oral hygiene behavior and snacking frequencyConclusionThis study showed no association between Pb and Cd concentrations in primary teeth and in saliva with dental caries prevalence.     

A principal components analysis of human odontometrics

It has long been recognized that tooth crown diameters in hominoids are all positively intercorrelated one with another. This study reports on sex-specific correlation matrices derived from 2,650 individuals from the Solomon Islands, Melanesia. Mesiodistal and buccolingual diameters of all permanent teeth from one side are used, excluding third molars. Analysis discloses significant sex dimorphism in the strengths of the intercorrelations, with females being better integrated. Principal components analysis (PCA) provides an objective means of data reduction (shown here to be preferable to simple size summation methods) and decorrelation of the resulting linear combinations. Four components are extracted (with results being virtually identical in the two sexes) and arguments are put forth that varimax rotation to "a simpler solution" may be counterproductive. Before rotation, the four components are 1) overall size, 2) buccolingual widths contrasted with mesiodistal lengths, 3) anterior (I,C) contrasted with posterior (P,M) teeth, and 4) premolars contrasted with molars. Most of the explained (shared) variance (63%) extracted by PCA is in overall size of the dentition. There is a strong urge to view the results of these principal components analyses as reflective of biologically and genetically meaningful entities.     

Sexual dimorphism in the early Miocene species ofProconsul from the Kisingiri Formation of east Africa: A morphometric examination using multivariate statistics

This paper examines the pattern(s) of sexual dimorphism within the upper dentition ofProconsul specimens from the early Miocene of east Africa. These fossils are compared against the corresponding dentition ofPan troglodytes andGorilla gorilla using principal components and cluster analyses. This paper demonstrates that both sexes ofPan andGorilla are characterized by their own distinctive shape patterns. It is also demonstrated that someProconsul specimens examined here display a pattern that is dissimilar from otherProconsul specimens also examined. This suggests that at least two species ofProconsul may have to be recognized as having lived in this region during the early Miocene. The identification of distinct patterns withinProconsul also suggests that their overall shape and size range are more similar toPan than toGorilla.     

A morphometric analysis of extant and early miocene fossil hominoid maxillo-dental specimens

It is demonstrated in this paper that before we can hope to formulate phylogenetic relationships between and amongst fossil hominoid material it is first necessary to sex the material accurately. In order to determine whether the morphological and morphometrical variability seen in fossil specimens is due to sexual or inter species dimorphism, it is necessary to calibrate fossil specimens against extant hominoid species' morphologies. Only after fossil specimens have been sexed is it possible to differentiate between morphologies that are related to sex and those that are species specific. This will help reduce fossil misallocation. A morphometric analysis of extant and fossilProconsul hominoid material is presented. Each fossil specimen has been sexed according to symplesiomorphic sex morphologies as defined in this paper. After the fossil specimens have been sexed they are analyzed using multivariate statistics. The identification of differing sex patterns within the specimens examined here suggests that a new species ofProconsul may have to be considered.     

Finger ridge-count variation among various Subsaharan African groups

This paper addresses the question of the extent to which finger ridge-count data are useful features with which to study population variation in Subsaharan Africa. Each subject was represented by a vector of 20 ridge-counts, a radial and an ulnar count for each digit. Such data were available from 11 African groups, nine of which were indigenous Africans, and two, the South African Colored and South African Indians, contained a portion of non-African ancestory. The ridge-counts were first transformed to principal component scores and these were subjected to multivariate analysis of variance and distance analysis to elucidate intergroup variation. The primary findings were that ridgecounts provide a good reflection of variation on at least two levels, that of African versus non-African, and variation among Africans. Also, the principal components that reveal variation at these two levels are very different. We conclude that ridge-counts can only be useful in population studies if full account is taken of their multicomponent nature.     

Comparative analysis of weight gain,hand/wrist maturation; and dental emergence rates in chimpanzees aged 0–24 months from varying captive environments

Variability during the first 2 years of growth and development is examined in captive chimpanzees. The mixed longitudinal study of 175 animals compares curves of weight, hand/wrist maturation, and dental emergence for groups within the sample which differ in sex, rearing circumstances (mother-reared versus hand-reared), and colony (Primate Foundation of Arizona, White Sands Research Center, and The University of Texas M.D. Anderson Cancer Center Department of Veterinary Sciences in Bastrop, Texas). Comparison of LOWESS fits of the curves, using a conservative jack-knife approach, reveals trends toward significant differences between colonies for weight (with 4 comparisons reaching significance) and between rearing groups for maturation (1 reaching significance). Results of a full versus reduced model approach show the same trends, for which significance is reached in a higher number of comparisons. The latter approach also indicates possible effects of sex and environmental differences on dental emergence rate. Difficulties with both approaches are discussed. It is concluded that the results are suggestive of significant sex and environmental effects on the variables monitored, justifying further analysis and continuation of the study. The study is significant in 1) providing norms specific to sex and rearing and colony environments with which individual colony animals may be compared in the assessment of their development and in 2) providing a standard, based upon data from a larger and more varied captive chimpanzee population than previously available, with which the dental emergence status and hand/wrist maturation of fossil apes and hominids may be compared. © 1996 Wiley-Liss, Inc.     

Age at first molar emergence in Lufengpithecus lufengensis and its implications for life-history evolution

The late Miocene hominoid Lufengpithecus from Yunnan Province, China, is crucial for understanding hominoid evolution in Asia. Given that age at first permanent molar emergence is a key life-history trait in primates, the present study determined the age at death of the Lufengpithecus lufengensis juvenile PA868, which was in the process of erupting its first molar. Using a perikymata periodicity of 7-11 days, along with estimation of cusp formation time and the postnatal delay of crown mineralization, perikymata counts obtained from the permanent central incisor and canine germs indicate that the age at death of PA868 was 2.4-4.5 years based on the central incisor germ, and 2.5-4.7 years based on the canine germ. The age at the first molar emergence was actually slightly younger (by about 0.3 years), as demonstrated by tiny wear facets on this tooth, which indicate that gingival emergence had occurred sometime before death. The average age at first molar emergence of Lufengpithecus lufengensis PA868 is estimated to be 3.2-3.3 years, with a range of 2.1-4.4 years. In comparison to extant primates and other fossil hominoids, the life history of Lufengpithecus lufengensis is similar to that of extant great apes and the Miocene hominoids Afropithecus turkanensis and Sivapithecus parvada, as well as Plio-Pleistocene Australopithecus, and different from monkeys, gibbons, and modern humans.     

OPGmRNA在牙齿萌出过程中牙台方组织内的表达

目的：探讨骨保护素（osteoprotegerin OPG）mRNA在牙齿萌出过程中胎方组织内的表达。方法：运用原位杂交方法检测大鼠下颌第一磨牙胎方组织内OPGmRNA的表达。结果：大鼠下颌第一磨牙牙台方组织内牙囊成纤维细胞中OPGmRNA在牙齿骨内萌出阶段中期阳性表达,与萌出早、晚期比较差异有统计学意义（P〈0．01）,其中早期比晚期差异显著（P〈0．01）;成釉细胞中OPGmRNA在牙齿骨内萌出阶段中期阳性表达,与萌出早、晚期比较差异亦有统计学意义（P〈0.01）,早期与晚期没有显著性差异（P〉0．05）。结论：OPGmRNA在大鼠出生后下颌第一磨牙牙囊成纤维细胞、成釉细胞骨内萌出阶段中期表达最强,牙齿萌出过程中可能通过OPGmRNA表达量的变化来调节牙齿的萌出。     

OPG mRNA在牙齿萌出过程中(牙合)方组织内的表达

目的:探讨骨保护素(osteoprotegerin OPG)mRNA在牙齿萌出过程中方组织内的表达。方法:运用原位杂交方法检测大鼠下颌第一磨牙方组织内OPG mRNA的表达。结果:大鼠下颌第一磨牙方组织内牙囊成纤维细胞中OPG mRNA在牙齿骨内萌出阶段中期阳性表达,与萌出早、晚期比较差异有统计学意义(P<0.01),其中早期比晚期差异显著(P<0.01);成釉细胞中OPG mRNA在牙齿骨内萌出阶段中期阳性表达,与萌出早、晚期比较差异亦有统计学意义(P<0.01),早期与晚期没有显著性差异(P>0.05)。结论:OPG mRNA在大鼠出生后下颌第一磨牙牙囊成纤维细胞、成釉细胞骨内萌出阶段中期表达最强,牙齿萌出过程中可能通过OPG mRNA表达量的变化来调节牙齿的萌出。     

Homologies of the anterior teeth in indriidae

Schwartz ('74) proposed revised homologies of the deciduous and permanent anterior teeth in living lemuriform primates of the family Indriidae. Gingerich ('77) described a juvenile specimen of Avahi and emphasized the importance of functional integrity in controlling the pattern of dental reduction in primates, neither of which supports Schwartz's interpretation. Schwartz ('78) recently reiterated his position without adequately discussing the Avahi evidence and the functional basis that probably controls dental reduction. Avahi has a deciduous dentition intermediate in morphology between that of Lemuridae and Indriidae, and similar to both. Thus the lower deciduous dental formula of Indriidae is probably 2.1.3, which is the typical and maximum deciduous complement known in living and fossil lemuriform primates. The formula of the lower permanent dentition in Indriidae is thus 2.0.2.3.     

湖北长阳青铜时代人类乳齿特征的研究

对在湖北长阳县深潭湾崖葬墓出土的青铜时代人类乳齿形态特征的观察研究显示在人类恒齿出现的大多数具有种族识别价值的形态特征在乳齿有相等程度的表现,其中部分特征的出现率和表现程度高于恒齿。与其他地区人群相比,长阳青铜时代人类乳齿特征在总体上与东北亚人类具有的“中国型牙齿”特征接近。同时,在个别牙齿特征上呈现出南亚蒙古人种的特点。作者对产生这种现象的原因进行了分析。本文还就长阳青铜时代人类乳齿测量数据的表现特点进行了探讨。     

Temporomandibular joint osteoarthritis in a British skeletal population

The potential role of dental function in TMJ osteoarthritis is examined in an ancient British population. Human skeletal remains from five archaeological sites in England (n = 369) were studied to assess the associations between the presence of osteoarthritis and dental function variables, in particular antemortem tooth loss and dental attrition. Individuals aged over 17 years with at least a portion of either the left or right TMJ were included in the study. Each individual was scored for the occurrence of arthritic lesions on the mandibular condyle and glenoid fossa, the level of dental attrition, and antemortem tooth loss. A loglinear analysis was performed with osteoarthritis as the dependent variable and tooth loss, attrition, sex, and age as the independent variables. Tooth loss and sex are not significantly associated with TMJ osteoarthritis when attrition and age are included in the analysis. Attrition is significantly associated with osteoarthritis even when the analysis corrects for age. The significant association of attrition with osteoarthritis suggests that dental functions may have an influence, separate from ageing, on the development of TMJ osteoarthritis.