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Objective: To determine the anterior Bolton ratio for a Finnish adult population and to investigate its associations with overjet., Material and Methods: This study is part of the Northern Finland Birth Cohort 1966. Clinical oral investigations, including three-dimensional intraoral scanning and registration of occlusion, were performed in connection with the 46-year follow-up for 1,961 subjects. Subjects with normal occlusion ( n  = 149), extreme overjet ≥ 8 mm ( n  = 49), large overjet 6-7 mm ( n  = 86), and negative overjet ( n  = 16) and no orthodontic treatment history were selected for further analysis. The mesiodistal widths were measured from canine to canine to evaluate the anterior Bolton ratio., Results: A mean anterior Bolton ratio of 78.6 (SD 3.1) was found for the normal occlusion group. Subjects with extreme overjet had smaller Bolton ratios compared to the normal occlusion group and the negative overjet group ( p  = .005, p  = .019, respectively). Overjet deviations were associated with upper canine and incisor widths., Conclusions: The mean anterior Bolton ratio in subjects with normal occlusion was larger compared to the original Bolton ratio. Tooth size discrepancy was associated with extreme and negative overjet at population level.

Background: The relationship between tooth size and stature has been analysed extensively at the interspecies level but has received less attention at the intraspecies level. The relationship between these two parameters does not seem to be the same among modern human populations. Aim: The aim of this study is to analyse the relationship between tooth dimensions and body measurements in the Baka Pygmies. Subjects and methods: Height, weight, and tooth dimensions were obtained for 45 adult Baka females and 17 males from Le Bosquet (Cameroon). Correlations were obtained between the variables and compared to results for other human populations. Results: The Baka population is distinctive in the small number of significant correlations. Only two buccolingual diameters among Baka females show any significant correlation with height. The lack of significant correlations between tooth dimensions and body dimensions among the Baka means that changes in body size are accompanied by random variations in tooth dimensions. Conclusion: The absence of correlations may be accounted for by the impact of environmental effects on the somatic growth of the Baka producing a Pygmy phenotype adapted to live in the forest. It is worth noting that many correlations become significant when sexes are pooled.

Aim: The purpose of this study was to investigate the scanning and segmentation precision of surface models of molars for the detection of small volumes, such as the reduced pulp cavity; formation of mineral deposits; detection of narrow root canals and to improve the clinical and morphological understanding of the number of root canals and their configuration., Methods: Eighteen human molars were scanned using X-ray micro-computed tomography. The reconstruction of the surface models had a precision of <1 voxel, using three-dimensional software and quantitative color mapping. In order to relate the measurements to changes over time the size of the pulp chambers was classified in two well-defined groups., Results: The mineral deposits were more evenly distributed in small pulp chambers than in large, but complete root canal calcification was never observed. No difference was observed in the material with respect to the presence of intra-radicular connections. In upper molars, a second mesiobuccal canal (mb(2)) frequency of 91% was found. The difference in length between the first mesiobuccal canal (mb(1)) and mb(2) was <1 mm. The number of root canals could be related to the number of root cones., Conclusion: In summary, three-dimensional surface models were made with a high precision; an increased accumulation of mineral deposits was noted in molars with small pulp chambers and combined with the consistent pattern of intra-radicular connections, the potential endodontic treatment complexity is underlined in such cases. Finally, an improved understanding of root canal prevalence was reached, when merging well-defined definitions on root morphology and clinical classification systems.

OBJECTIVE. To analyze correlations between the inclination of the permanent maxillary lateral incisors and the intraosseous position of the erupting permanent maxillary canines on panoramic radiographs. MATERIAL AND METHODS. The inclination of the lateral incisor to the midline, the mesiodistal position of the crown of the canine, and the inclination of the canine to the midline and to the long axis of the adjacent incisor were measured on panoramic radiographs of 1013 subjects aged 8-11 years. RESULTS. The distal inclination of the lateral incisor crown increased until 10 years, after which no significant changes occurred. The canine erupted with increasing mesial inclination of the crown until 9 years, after which it began to progressively right itself. As a result, inclination of the canine to the adjacent incisor increased between 8 and 9 years and decreased between 10 and 11 years. Until the children reached 9 years of age, the more mesial the crown of the unerupted canine, the greater the decrease in the distal inclination of the lateral incisor crown. CONCLUSIONS. The inclination of the crown of the lateral incisor varies during eruption of the canine, increasing distally until 10 years as a physiological stage in the mixed dentition. The inclination of the lateral incisor is also associated with the mesiodistal position of the canine crown. The mesial intraosseous location of the canine crown results in righting of the lateral incisor.

Objective: Previous studies have demonstrated differential effects of the X and Y chromosomes on dental development. The expression of sexual dimorphism in terms of tooth size, shape, number and developmental timing has been explained especially by Y chromosome influence. The Y chromosome promotes enamel, crown and root dentin development. The X chromosome has an effect on enamel deposition. The aim of this research is to study the influence of the extra X chromosome on the development of permanent tooth root length., Material and Methods: The study subjects (all of whom were from the Kvantti Dental Research Project) were seven 47,XXX females, five female relatives and 51 and 52 population control men and women, respectively. Measurements were made from panoramic radiographs on available permanent teeth by a digital calliper according to established procedures., Results: The results showed that the maxillary root lengths of the 47,XXX females were of the same magnitude as those in normal women, but the mandibular root lengths were longer in 47,XXX females than in normal men or women., Conclusions: Increased enamel thickness in the teeth of 47,XXX females is apparently caused by the active enamel gene in all X chromosomes having no increased influence on crown dentin formation. These results in 47,XXX females indicate an increase in root dentin development, at least in the mandible, which together with the data on crown formation reflects a continuous long-lasting effect of the X chromosome on dental development.

Objective: To analyze differences in tooth display, lip-line height, and smile width between the posed smiling record, traditionally produced for orthodontic diagnosis, and the spontaneous (Duchenne) smile of joy., Material and Methods: The faces of 122 male participants were each filmed during spontaneous and posed smiling. Spontaneous smiles were elicited through the participants watching a comical movie. Maxillary and mandibular lip-line heights, tooth display, and smile width were measured using a digital videographic method for smile analysis. Paired sample t-tests were used to compare measurements of posed and spontaneous smiling., Results: Maxillary lip-line heights during spontaneous smiling were significantly higher than during posed smiling. Compared to spontaneous smiling, tooth display in the (pre)molar area during posed smiling decreased by up to 30%, along with a significant reduction of smile width. During posed smiling, also mandibular lip-line heights changed and the teeth were more covered by the lower lip than during spontaneous smiling., Conclusions: Reduced lip-line heights, tooth display, and smile width on a posed smiling record can have implications for the diagnostics of lip-line height, smile arc, buccal corridors, and plane of occlusion. Spontaneous smiling records next to posed smiling records are therefore recommended for diagnostic purposes. Because of the dynamic nature of spontaneous smiling, it is proposed to switch to dynamic video recording of the smile.

Facial asymmetry is a naturally occurring phenomenon that is often due to differences in the mandibular dimensions on the right and left sides. The point where normal asymmetry turns abnormal cannot be easily defined, and no standards exist by which a judgement of abnormality can be made. The aim of the present study was to assess mandibular asymmetry in healthy children and its possible fluctuation during growth. The subjects consisted of 182 healthy children (88 girls, 94 boys) who had had an orthopantomogram taken at ages 7 (mean 7.5 years) and 16 (mean 15.9 years). On digitized orthopantomograms, condylar and ramus heights on both mandibular sides were measured with a Numonics Accugrid digitizer (Numonics Co., Montgomeryville, Pa., USA) and analysed with X-metrix software (Smart Systems, Turku, Finland). A paired t-test was used to determine the significance of the differences between the sides, and ANOVA to test the significance of the change in asymmetry during growth and between genders. The results revealed a statistically significant difference between the right and left sides in condylar height at age 7 years, in ramus height at both ages, and in the condylar and ramus height at age 16 years. The present study confirms that healthy young subjects generally have a statistically significant mandibular asymmetry, which, however, is only seldom clinically significant. The decision to initiate treatment because of asymmetry has to be carefully considered, since the study further showed that mandibular asymmetry may diminish or appear during growth of healthy subjects.

The sizes of dental arches in 129 children with cleft palate were evaluated retrospectively from dental casts taken at the mean age 6.2 years (range 5.2-7.5). The material included 61 children with submucous cleft palate (SMCP) and 68 children with isolated cleft palate (ICP). Twenty of the children with SMCP were not operated on, while 41 had had surgical treatment, either palatal repair (n = 16, mean age at operation: 1.6 years, range 0.8-3.9) or pharyngeal flap (VPP) surgery (n = 25, mean age at operation: 4.5 years, range 2.6-6.2). In children with ICP, one-stage hard-palate and soft-palate closure had been done at the mean age of 1.5 years (range 1.0-2.1). Decreased maxillary intermolar widths were seen in children with SMCP after VPP, and especially after palatal repair. The children with ICP had the smallest maxillary dental arch widths. No significant differences were observed in the maxillary arch length or mandibular intermolar arch dimensions in children with SMCP or ICP. Surgery is associated with decreased maxillary intermolar arch widths in children with SMCP. Children with ICP had smaller maxillary dental arch widths than children SMCP.

The objectives of the present prospective longitudinal study were to establish the survival and success rates for premolars with partly developed roots transplanted according to a set protocol, and to analyze the effect of varying pre-surgery root development on final root length. Standardized periapical radiographs of 132 consecutively transplanted premolars were obtained at predetermined intervals over a 4-year follow-up period. Survival and success rates were calculated on the basis of presence of teeth and recording of defined radiological variables, respectively. Final root length was compared to normative metric data for root morphology. From the total sample, 54 patients with 68 transplanted premolars suitable for analysis of root growth relative to initial root length were identified, and divided into subsamples according to root length pre-transplantation. Survival rates were 100% after 1, 2, and 3 years, and 98.6% 4 years post-transplantation. The success rates were 92.9%, 92.8%, 89%, and 90.5% in subsamples collected 1, 2, 3, and 4 years after transplantation, respectively. The transplants obtained on average 78% of normative root length, and by dichotomizing the transplanted teeth in subsamples with 'short' and 'long' roots pre-surgery, similar final root lengths were observed even if 'short' roots had the greatest increase. Very early transplantation (roots < 7 mm), however, tended to result in short final root length. It is concluded that the success and survival rates were comparable to results obtained in similar studies. Initial root length was a significant predictor of root length increase. Transplanting teeth with short roots is to risk short final root length.

Williams syndrome is a rare congenital syndrome with distinctive craniofacial features, cardiovascular abnormalities, and behavior characteristics including mental retardation. The dental abnormalities have received scant attention in previous literature. The aim of this study was to describe dental characteristics in individuals with Williams syndrome. In a group of 41 individuals more than 10 years of age, 40.5% had agenesis of one or more permanent teeth and 11.9% had agenesis of 6 permanent teeth or more. The mesio-distal and labio-lingual dimensions of permanent tooth crowns were measured on 31 dental study casts from individuals older than 12 years. The mesio-distal and labio-lingual dimensions were significantly smaller compared with a reference sample. An analysis of tooth morphology was performed on the same dental study casts revealing altered tooth morphology. A high proportion of maxillary and mandibular incisors was tapered or screwdriver shaped. An evaluation of taurodontism on mandibular permanent molars was performed using a metric crown-body/root ratio. However, most of the molars rated as being taurodontic had short or extremely short total tooth lengths and could thus be rated taurodontic without meeting the classical definition. The results of this study indicate that although there is variation in dental development in individuals with Williams syndrome, agenesis of permanent teeth in combination with aberrations in tooth size and morphology may affect dental esthetics and complicate orthodontic and prosthodontic treatment.

Short-root anomaly (SRA), occurring mostly in maxillary incisors, is defined as developmentally very short, blunt dental roots. The condition has a genetic background and is related to hypodontia. Earlier population studies have been based on schoolchildren with developing dentitions and have indicated prevalence figures between 1% and 10%. We studied a random sample of existing panoramic radiographs of 2000 university students for SRA. Roots as long as or shorter than the crowns in the incisors and visually evaluated as very short, blunt roots bilaterally in the posterior teeth were classified as SRA. The prevalence was 1.3%. According to anamnestic information, half the SRA patients had undergone orthodontic therapy, but pre-treatment radiographs were unavailable. In 70% of the SRA patients the short-rooted tooth pairs were upper incisors, but also involved were maxillary premolars, lateral incisors, and lower second premolars. Women were significantly more often affected. We discuss other factors known to cause short-rooted teeth and conclude that the population prevalence for genetic SRA in fully developed dentitions is close to our 1.3%.

Handedness has been shown to be related to a number of systematic asymmetries in body dimensions, dermatoglyphic patterns and cerebral morphology. The aim here was to compare linear and angular tooth crown asymmetries of the permanent molars in healthy right-handed and left-handed subjects. The material comprised 27 children with recorded concordant left-side dominance of hand, eye and foot. The controls were an age- and sex-matched group with right side dominance. The material is based on the Collaborative Perinatal Project where detailed medical records and the dentitions, including accurate dental impressions, of over two thousand American children were examined in the USA in the sixties. Machine vision technique was used to obtain accurate three-dimensional information from the occlusal surfaces of the first permanent upper and lower molars. The directional asymmetry values of angular measurements of mandibular first molars showed evidence of asymmetry of opposite direction between the two examined groups. The results indicate that occlusal morphology of first permanent molars may be affected by handedness, and this tendency is most evident in the angular measurements of the mandibular molars. Fluctuating asymmetry did not differ significantly between the examined groups.

Two lingual root structures are occasionally found on human permanent maxillary molars. One of these is the normal lingual root, which is always present, the other is a supernumerary structure which can be located either mesiolingually (radix mesiolingualis (RML)) or distolingually (radix distolingualis (RDL)). The available literature refers only to the existence and location of RML and RDL Very small materials have, quite simply, hitherto precluded a more detailed description of these roots. The large collection of extracted teeth at the School of Dentistry in Copenhagen now includes a non-random subcollection of 145 permanent maxillary molars, the root complex of which contains 2 lingual root structures. Based on this material it was possible to undertake a modern, systematic analysis of the macromorphological variation of RMLs and RDLs. In this study, which was mainly non-metric, criteria for the identification of RML and RDL were established. The analysis also showed that the lingual supernumerary roots were only rarely found on the first molar, but with increasing frequency on the second and third molars. Both separate and non-separate RML and RDL were observed. In the material, degrees of separation greater than 0.9 were registered, degrees of divergence up to approximately 45 degrees, an apical bend of approximately 90 degrees, and extreme apical slenderness. Even though the supernumerary roots described here do not occur very often, knowing about them is nevertheless clinically relevant in for example endodontic and surgical contexts.

The aim of this investigation was to present the 2-year follow-up results of a longitudinal study examining the influence of growth hormone (GH) substitution on dental maturity in healthy children of short stature (height <2 SD). At baseline, the children were divided into a GH-deficient group and a GH non-deficient group, and comparisons were made with healthy controls (height between -2 SD and 2 SD) and between the short stature groups. The GH-substituted group included 24 children (8 F, 16 M) with a mean chronological age of 12.20 +/- 2.40 years, whereas the GH non-substituted group included 19 children (5 F, 14 M) with a mean chronological age of 11.00 +/- 2.40 years. The corresponding age- and sex-matched control groups constituted 48 and 36 children, respectively. The mean dental age in the GH-substituted group was 11.60 +/- 2.70 years, compared to their healthy controls 12.40 +/- 2.60 years (P< 0.05). The dental age for the GH non-substituted children was 10.20 +/- 2.60 years compared to their controls 11.90 +/- 2.60 years (P< 0.001). GH-substituted children show an acceleration in their dental maturity in contrast to controls, whereas in non-substituted children the acceleration is less pronounced.

Scanning electron microscopy was used to study the effect of cyclophosphamide (Cy) on molar development in 18 Sprague-Dawley rats from 15 to 48 days of age after birth. Doses of 30 mg/kg body weight of Cy dissolved in 1 ml 0.9% NaCl were given to the rats at 10 and 13 days of age. Eighteen control rats had injections of 1 ml 0.9% NaCl at the same ages. The most obvious changes in the experimental teeth were found in the developing roots of the first and second molars and in both the crown and roots of the third molar. The roots of the first and second molars were short and showed apical closure in the experimental rats. In addition to the disturbances in crown and root formation, the third molars were also significantly reduced in total size as compared with the third molars in the control rats.

Root length, crown height, and root morphology were studied on intraoral and panoramic radiographs in 33 Turner syndrome patients aged 7.0-16.7 years, subdivided on the basis of karyotype. Thirty-three normal girls aged 10.2-16.4 years served as controls. In the 45X patients and, with the exception of a few teeth, also in the isochromosome and mosaic karyotypes, root length and crown height of incisors, canines, and premolars were significantly reduced. Some teeth showed altered crown-root proportions. Maxillary first premolars showed a significantly increased number of two-rooted and three-rooted variants. Mandibular premolars and molars had a complex root morphology, and a classification system was established including four premolar and six molar root types. Premolars had a significantly increased number of root components. Some of the variants, such as a molar-like second premolar, are apparently specific for these patients. On several first molars a radix entomolaris was identified. Two separate mesial and one or two separate distal roots were also frequently seen. Our investigation demonstrates that X-chromosome deficiency influences root formation.

To determine the effect of phenytoin (PHT) on dentin apposition and the rate of caries progression in dentin, 40 Wistar rats were treated daily for 35 days with intraperitoneal injections of 5,5-diphenylhydantoin. Twenty-eight controls received saline with pH adjusted to that of PHT. One PHT and one control group were fed a 43% sucrose diet, and the others a non-cariogenic pellet diet. Streptococcus sobrinus was inoculated to induce caries. Schiff staining was used to determine caries. The areas of dentin apposition and dentinal caries lesions were quantified after tetracycline staining. The root lengths were measured. PHT reduced slightly the dentin apposition and activated significantly the progression of the dentinal carious lesions. No difference in caries initiation was found. The high-sucrose diet reduced dentin apposition and increased the rate of progression of existing caries greatly. Our study suggests that both the high-sucrose diet and PHT have an effect on secreting odontoblasts, which can be seen as an alteration in dentin apposition and caries progression rates in dentin.

Fluctuating asymmetry was evaluated in the dental arcades of 112 children (60 male, 52 female) of alcoholic mothers. Only individuals who showed no signs of the fetal alcohol syndrome were included. When these results were compared with those of a control group of 120 normal children, the former group was found to be significantly more asymmetric. The present study showed that canines were the least asymmetric whilst lateral incisors showed the greatest levels of asymmetry. It is suggested that the elevated levels of fluctuating odontometric asymmetry in children of alcoholic mothers may be ascribed to prenatal stress, especially during the soft tissue stage of odontogenesis.

Metric changes in the Negro dentition were evaluated in a sample of artificial stone casts of the dental arcades of 106 living South African Negroes (56 males, 50 females) and in 100 Negro crania (50 males, 50 females) drawn from the R. A. Dart Collection. Comparison of the mesiodistal and buccolingual dimensions of these two samples to the published results of a similar study on earlier Negroes revealed a statistically significant trend towards tooth-size enlargement. This positive secular trend was found to be most pronounced in the mesiodistal diameter, with less than half of the teeth considered showing significant buccolingual enlargement. Although the trend was equally pronounced in both sexes and in both arcades, mesiodistal change was found to increase in an antero-posterior direction, while buccolingual change centred around the anterior teeth.

In 1957 a woman was murdered in Oslo. Her left breast exhibited tooth marks. A man was arrested and sentenced to life imprisonment partly because of the dental evidence. He never admitted guilt and filed a petition for retrial. The present author was appointed as new dental expert. The material consisted of the fixed breast, models of the bite mark and models of the teeth of the convict, and several photographs. By means of visual examination, a magnifying glass, a lens stereoscope and a stereomicroscope characteristic details were noted. Stereoscopic picture pairs were taken, the material was studied by means of scanning electron microscopy and a stereometricgraphic plotting method permitting the outline of the tooth mark or the biting edge of a tooth to be registered in great detail in all three dimensions in the form of a contour map. This method has not previously been applied in the analysis of tooth marks in human skin. These examinations revealed no discrepancies but showed many corresponding characteristic features between the tooth marks and the teeth of the convict, resulting in the conclusion that it is highly probable that the tooth marks in the breast were made by the teeth of the convict.

Mesiodistal and buccolingual crown diameters of deciduous teeth were measured from dental casts of 540 Icelandic children. Statistically significant sexual dimorphism was present in five of the buccolingual and in six of the mesiodistal diameters. The variability of the measurements followed the field concept but did not show systematic sexual dimorphism. In accordance with the permanent teeth, the size of the deciduous teeth also proved to be at the top of the range for populations of European origin.

Maxillary incisor lingual fossa depth was measured in East Greenland Eskimos. It was shown that the statistical distribution for the trait may vary from population to population, from tooth type to tooth type and between the sexes. Examination of statistical distribution should be a part of studies giving detailed statistical analysis of trait. The statistical distribution is probably compatible with a hypothesis of polygenic inheritance. The correlations across the midline were higher for I1 than for I2, and I1 to I2 correlations were lower than across midline correlations for both I1 and I2. It was shown that the degree of fluctuating asymmetry may vary from one dental trait to another. For lingual fossa depth no population variation in fluctuating asymmetry could be demonstrated, in spite of obvious differences in environmental conditions for the populations compared. No sex differences in fluctuating asymmetry were found.

A study of morphologic variability was made for maxillary incisor lingual fossa depth. The problem of variability is discussed, and new methods for the statistical treatment of variability are presented. Possibly, the best procedure to express biologic variability is to present SDs, CVs, Xs, ranges, RCs, and the logarithmic graphic method of the relationship between CV and X. No sex differences in variability could be demonstrated. Maxillary centrals and laterals in the Eskimo were found to have relatively equal variability. This is seen in connection with the great functional demand on Eskimo incisors, giving less reduction of the laterals, a possible simultaneous commencement of calcification for I1sup and I2sup, and possible genetic drift. Comparison of variability for six populations shows no racial differences in variability. Variability is not found to increase with inbreeding. Population comparisons do not confirm little reduction in the Eskimo to be associated with high variability. Genetic drift might be the explanation of the homogeneity of maxillary incisor lingual fossa depth in East Greenland Eskimos.

The occurrence of neonatal lines (NL) in all cusps of the first permanent molar (M 1) has been investigated in complete series of M 1 from 16 males and 11 females. Previous investigations of newborn children gave reason to expect a lower frequency of occurrence in males. The present investigation showed that about one half of the males did not have NL in any of their four M 1's, while all females had NL in at least one tooth. This wound seem to indicate that on the average boys are less dentally mature at the time of birth than girls. At the same time, it opens up the possibility of a forensic sex assessment. When skeletal remains of children and young persons are in concern.

A morphologic trait, not previously registered, on the incisor lingual surface: "The lingual angle of incisors", was studied in Norwegians. The lingual angle is the angle between the floor of the lingual fossa and the dental tubercle. Measurements of the lingual angle could be performed with sufficient accuracy. Deviations from normal distribution in skewness and kurtosis values did not affect statistical testing. The general similarity of the frequency polygons for all incisors in the way they were peaked and stepped is possibly due to participation of the same factors on the genetic level in the determination of the trait. The mean lingual angles were (in degrees): I1sup = 142, I2sup equal 156, I1inf = 153 and I2inf = 154. No significant bilateral asymmetry or sex differences were found. Correlations were high for both central to central and lateral to lateral incisors in both jaws, highest for centrals in the maxilla and laterals in the mandibula. Central to lateral correlations were relatively low, especially in the upper jaw. Interjaw correlations were low, but I1sup showed a tendency to be better correlated than I2sup to lower incisors. I2sup and I1inf were the most variable incisors in each jaw. The dental tubercle probably plays an important role in determining the lingual angle. Measurements of the lingual angle give information on the profile of the lingual surface in inciso-cervical direction. Statistical analysis of a phenotypic trait may give information on factors which determine the trait.

Dental casts and genealogical records collected among several linguistic groups of the Solomon Islands of Bougainville and Malaita form the data-base for the present series of analyses of the human dentition at the population level. Pedigree analysis and complex segregation analysis of nuclear families produce mutually consistent results which are interpreted as the absence of any significant major-gene effect on tooth size.

The size and shape characteristics of permanent mandibular first molars were compared in a group of young males with Down syndrome (DS) and a control group of normal males. Generalized size was quantified by the log transforms of five intercusp distances and shape by a principal component analysis of the log distances scaled to constant size. On average the DS molars were smaller than the controls by 8%, the most marked reduction being in the distance between the distal and distolingual cusps. The scores on two of the four components of shape also differed between the DS and control teeth. These two shape components, which accounted for over 41% of the total shape variation, were determined specially by the occlusal morphology of the distal crown region. Discriminant function analyses also indicated the importance of the distal regions in discriminating between control and DS molars. Evidence suggests that trisomy 21 is associated with a general retardation in growth. The observed features of DS molars were consistent with decreased cellular activity in the developing tooth germs, producing morphological changes that were more pronounced in the later-forming crown regions.

Maxillary incisor lingual fossa depth was measured on casts of East Greenland Eskimo dentitions. No directional side asymmetry was found. The present study is the only which shows mean lingual fossa depth to be significantly deeper in the female than in the male. Larger incisor strength in the females is functional as the females are known to use their incisors as tools. The present investigation shows that on the question of sex differences conclusions should be drawn for the examined population only, and that generalization to other populations should be avoided. Mean lingual fossa depths were significantly different for centrals and laterals, but the laterals demonstrate special lack of reduction in this population. Lack of reduction of incisors together with frequent agenesis of third molars demonstrate that the posterior dentition may reduce independently of the anterior dentition. Mean lingual fossa depth, and relative fossa depth, in East Greenland Eskimos clearly show Mongoloid values.

Fluctuating dental asymmetry was evaluated as an indicator of environmental stress in a group of 202 living Lengua Indians from the Paraguayan Chaco area. Older, less accultured individuals were shown to be significantly more asymmetric than younger individuals who had been increasingly exposed to western foodstuffs and medicine. Lengua Indians demonstrated similar levels of asymmetry to another preliterate group, the Ticuna Indians of Columbia, but were found to be significantly more asymmetric than contemporary caucasoids. Similar patterns of asymmetry in both arcades for males and females were confirmed by analyses of variance and by Spearman's rank-order correlation coefficients. Partitioning variation in the degree of asymmetry by arcade, dimension and tooth revealed significant differences in the effects of tooth and arcade only: asymmetry was greater in the maxilla and greater in the more distal teeth within each morphogenic class.

Mesiodistal and buccolingual crown diameters were measured from casts of 1010 dentitions of schoolchildren from Northeast Iceland. Their teeth proved to be larger than in Europeans generally, being exceeded only by Australian Aborigines, some American Indian populations, and American Negroes. In comparison with Ohio Caucasians of Northwest European origin Icelanders showed clearly larger dimensions, less sexual dimorphism, and a different pattern of dimorphism. Crown indices were also distinctly different in Icelanders and Ohio Caucasians.