A study of the taxonomic significance of the dental arch.

Sixteen dimensions were measured from the maxillary and mandibular dental arches of different ethnic groups of man, apes and monkeys. Multivariate analysis showed that discrimination was possible among the ethnic groups of man on the one hand and between the ape and monkey samples on the other. Nevertheless, the actual degree of discrimination between the primate samples depended upon whether the maxillary or mandibular arch dimensions were analysed. Furthermore, subsequent inclusion of the dental arch dimensions of fossil hominoid samples into the analysis confirmed the taxonomic significance of the dental arch, although its importance must await the acquisition of the more non-human primate data.     

The British dental arch

Thirty-two dimensions of the maxillary and mandibular dental arches were measured on 320 adult skulls derived from Anglo-saxon to modern times. Multivariate analysis showed varying patterns of contrast between the samples, depending upon which arch dimensions were considered. The results suggest that dental arch changes occur independently of jaw changes.     

儿童下牙弓发育的测量

本研究测量了１９３６名６－１２岁男女儿童的下颌牙弓的宽度和弦长。儿童前牙弓在７－９岁时增长最快,为此时恒尖牙萌出所致,１０岁以后各年龄组均数差异检验没有显著性意义。在整个替牙期,儿童前牙弓宽度约增加２ｍｍ,弦长增加１．８ｍｍ,儿童后牙弓的宽度和弦长约增加１ｍｍ左右。男孩前牙弓宽度比女孩大１ｍｍ左右。后牙弓的宽度和弦箕各年龄组均为男大于女,约１ｍｍ在右。可以把小学年龄阶段儿童的牙列分为乳牙弓、第１恒     

The relationship of dental crowding to tooth size, dental arch width, and arch depth

This study was undertaken to answer the question, "Are there any differences in the mesiodistal tooth diameters, dental arch width and dental arch depth between the crowded and noncrowded dentitions?" The materials submitted for study consisted of the Orthoscan intraoral occlusograms of 89 subjects with well-aligned dentition and those of 74 subjects with gross dental crowding. The tooth size and arch dimensions were measured from these intraoral occlusograms. The data were subjected to statistical treatment for comparison of noncrowded and crowded groups. The findings in this study lead to the following conclusions: The mesiodistal tooth diameters of the crowded group were significantly larger than those of the noncrowded group. The dental arch widths of the crowded group were significantly smaller than those of the noncrowded group. No substantial or significant difference in dental arch depth between the crowded and noncrowded subjects could be noted. From these findings it seems that tooth size and dental arch width are determining factors in the formation of dental crowding. Clinically, these results suggest that in the treatment of dental crowding, extraction of teeth and/or expansion of dental arches should be considered depending on what is the main causative factor.     

Genetic influences on dentition and dental arch dimensions: a study of monozygotic and dizygotic triplets

Previous studies of the tooth and dental arch dimensions in twins have suggested that the size and form of the dentition is more under genetic control than the size and form of the dental arch. A study of dentition and dental arch was carried out on three sets of same-sex triplets, two sets being monozygotic and one set dizygotic. No significant differences were found in the dental arch dimensions in any set of the triplets. The tooth dimensions showed no significant differenes in the monozygotic triplet sets or in the monozygotic pair from the dizygotic triplet set, but showed significant differences between the monozygotic pair and the third member of the dizygotic set. This confirms the data obtained from twin studies.     

Oro-maxillofacial development in patients with GH deficiency and in normal short children

Detailed oro-maxillofacial studies using dental cast, pantomogram and cephalogram were performed in 43 patients with GH deficiency aged 7-17 years and compared statistically to the results from 62 short children with normal GH secretion. The dental age was retarded as compared to the chronological age in patients with GH deficiency by a mean of 2.0 +/- 1.3 years. This value did not differ statistically from that observed in normal short children (1.7 +/- 0.8 years). However the bone age was significantly retarded in patients with GH deficiency (3.2 +/- 1.7 yrs vs 1.5 +/- 1.1 yrs, p less than 0.001). There was no difference between tooth size or cephalogram analysis results in the children in the two groups. The coronal arch length, basal arch width and basal arch length were shorter in patients with GH deficiency. These data indicate underdevelopment of the maxilla in patients with GH deficiency.     

Risk factors for poor dental arch relationships in young children born with unilateral cleft lip and palate

To identify risk factors for poor dental arch relationships in children with unilateral cleft lip and palate in the United Kingdom, the authors performed a cross-sectional outcome study with retrospective data capture of treatment histories in children under the care of 44 cleft teams in the United Kingdom. The study sample comprised 238 children born with nonsyndromic complete unilateral cleft lip and palate between April 1, 1989, and March 31, 1991, who were between 5.0 and 7.7 years of age (mean age, 6.5 years) at the time of data collection. The Five-Year-Old Index was used to rank dental arch relationships from dental study models. Velopharyngeal insufficiency was assessed with the use of the Cleft Audit Protocol for Speech. An independent panel recorded surgical treatment histories from the clinical notes. There was no association between the technique and the timing of primary repair, the experience of the surgeon, or presurgical orthopedics and dental arch relationships. Secondary velopharyngeal surgery was independently associated with poor outcome (OR, 4.14; 95 percent CI, 1.6 to 10.7; p = 0.003). Primary nasal repair was protective (OR, 0.47; 95 percent CI, 0.23 to 0.93; p = 0.031) against poor dental arch relationships. Secondary velopharyngeal surgery and primary nasal repair were found to be independently associated with dental arch relationship outcomes in young children with unilateral cleft lip and palate in the United Kingdom.     

Palatal and dental arch morphology in Down syndrome

The analysis of palatal vault morphology and maxillary dental arch shape was carried out in the sample of 42 Down syndrome (DS) patients with trisomy 21. The data were compared to those of healthy controls from the same population matched for age and sex. Palatal morphology and upper dental arch shape were studied on hard plaster casts of the patients and controls. No sexual dimorphism in palatal and dental arch shape was observed in DS and controls. Normal palatal shape was more frequent in controls than in DS subjects (52.38% vs. 28.57%; p < 0.05). DS patients displayed significantly higher frequency of shelf-like or "stair palate" (38.1%) than controls (11.9%) (p < 0.02). The younger age group (3-14 year) showed much higher frequency of "stair palate" than controls (26.19% vs. 2.38%; c2 = 9.72; p = 0.003). The older group of DS patients did not show increased frequency of such shape of the palatal vault. There was no significant difference in dental arch shape between DS patients and controls. High frequency of shelf-like palate in DS subjects is decreasing by age. The obtained results indicate that palatal vault morphology is subjected to the age related changes. These changes can be attributed to the growth of caraniofacial structures and increased tonus of tongue and other orofacial muscles.     

Heritability of dental arch dimensions in humans.

The purposes of this study were to estimate the heritabilities of several human dental arch dimensions and compare the hereditary differences among kinships and among variables. The sample consisted of 102 Japanese families, each including both parents and one of their offspring, and on average all subjects had relatively well-aligned permanent dentitions. The heritabilities of all variables were estimated from the regression of offspring on parent and on midparent. Results showed that genetics played a role regarding dental arch dimensions, and arch perimeter (sum of tooth width) was a more definite genetic-related factor than other arch dimensions, such as width, length, or size. There were few significant hereditary differences between sons and daughters, and between upper and lower arches for each variable. Sex chromosomal involvement was not confirmed, but maternal effects were found to be more evident in daughters than in sons, for both arches. Comparisons among the heritabilities of overall and of anterior arch dimensions indicated that size of the anterior part of the dental arch might be less resistant to environmental factors, especially in case of the lower arch.     

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.     

Measurements of tooth wear among Australian Aborigines: I. Serial loss of the enamel crown

The dental casts made from Aboriginal children during the course of a longitudinal growth study in Central Australia provided material for analyzing tooth wear under known environmental conditions. The wear facets produced on the occlusal surfaces were clearly preserved on the dental stone casts and recorded the progress of enamel attrition from ages 6 to 18. These casts were photographed and traced by electronic planimetric methods that automatically recorded the location and size of wear facets on the first and second permanent molars. These areas of worn tooth surface were compared to the total tooth surface. The worn surface was regressed on age to calculate wear rates of each tooth. Discriminant analyses were also performed to determine the significance of dental attrition differences between the sexes at each age group. The total wear on each tooth was highly correlated with age as expected but females wore their teeth at a significantly higher rate than males. The mandibular molars wore more rapidly than maxillary teeth in both sexes. The discriminant analysis successfully grouped 91% of the cases according to age and sex. Pattern of wear, the location, and size of wear facets also differed between age groups and sex. The questions of why there is a difference between male and female wear or why there is greater wear on one arch or arch region have no ready answers. The differing rates and pattern of dental wear do suggest that arch shape and growth rates may be the answer though it has yet to be tested. However, the occlusal surface wear is useful for age estimation in a population and provides a record of shifting masticatory forces during growth.     

Familial similarity in dental arch form and tooth position.

This study was done to quantify and compare similarities in dental arch form and tooth position among individuals of various degrees of biological kinship. The sample consisted of 360 dental casts selected from 102 Japanese families, each including both parents and one of their offspring. Most of the subjects had well-aligned permanent dentitions. Coefficients of dissimilarity were obtained by orienting two standard-sized dental arch diagrams plotted from occlusal photographs to the position of best fit. Dissimilarity between adults and children from different families was computed and served as the control data. With few exceptions, the mean dissimilarity between parents and offspring was smaller than that of the nonfamilial pairings; however, statistical differences were not always significant. Among all the teeth observed, the position of both upper and lower central incisors was found to exhibit the least familial similarity. Analysis of variance among pairings of different sources of variation suggested the existence of significant additive genetic effect, both autosomal and sex-linked. Relative contribution of the additive genetic effect in the total variability of this sample was estimated for dental arch form and tooth position to be in the range of 55-60% and 39-77%, respectively. Autosomal additive genetic effects appear to strongly account for the variation in position of the second premolar and of the first molar.     

Comparative study of mesiodistal crown diameters and arch dimensions between indigenous British and Pakistani immigrant populations

Over the last two decades, the United Kingdom has seen an increase in the number of immigrants from the Indian subcontinent, mainly Pakistan. The amount of information that is available regarding parameters such as mesiodistal crown diameters and dental arch dimensions is, however, somewhat limited for this population. An investigation was carried out to compare corresponding mesiodistal crown diameters and arch dimensions between samples of the indigenous British population in Leeds (England) and the Pakistani immigrant population living in Rochdale (England). Measurements were taken from dental casts. The results showed that there were no significant differences between the two ethnic groups in corresponding mesiodistal crown diameters or arch dimensions. Data are provided for the Pakistani immigrant population in Britain.     

Interspecific allometry of the mandible,dental arch,and molar area in anthropoid primates: Functional morphology of masticatory components

Allometric equations relating the lengths and widths of the mandible and dental arch, and of molar area, were obtained in a wide range of anthropoid primates grouped into four subsets, pongids, cercopithecids, nonmarmoset platyrrhines, and marmosets. Mandibular width is negatively allometric against length across anthropoids but cercopithecids had relatively wider mandibles than nonmarmosets of the same size class. Mandibular length relative to dental arch length was isometric within and between the four groups but dental arch width scaled negatively against all the other dimensions examined in this study, indicating a functional dissociation between the dental arcade and the bony mandible. Molar area showed various scaling patterns relative to mandibular length (isometry) and width (positive). There were no parameters that scaled positively against body weight across groups, except for molar area in cercopithecids (strongly) and nonmarmoset (moderately). Notable functional specializations include relatively long dental arches in cercopithecoids, related to large, elongate bilophodont molars, and the tendency to increase relative jaw length across the range of anthropoid sizes, reflecting negative allometry of the brain (cranial bicondylar width). We caution that various allometry and functional patterns may be masked by generalizing from broad taxonomic comparison involving a large sweep of adaptative patterns.     

Tooth eruption: the phase transition theory on biological formation of an orderly structure

The mechanism of the formation of an orderly structure from random elements in organ development was clarified by studying the maturation of the dental arch in the human mandible. First, an application of methods established in statistical physics to a system of organ development was made possible, and then, the mathematical procedures for quantitative study of the structure and development of the dental arch were established in relation to radiographic data. The experimental results demonstrate that a parallel arrangement of the longitudinal axes of the lateral teeth is formed co-operatively in the dental arch. As formulation of the results to mathematical relations, the regulatory process was expressed by a non-linear Langevin equation of order parameter denoting an angle between longitudinal axes of the individual teeth. It follows that the orderly structure evolves with a change in thermodynamic potential; that is, the establishment of order in a phase transition. We propose the concept that organ differentiation is a phase transition in a dissipative system, with the decrease of gene activity substituted for temperature.     

A comparative study of tooth and dental arch dimensions in Jewish children of different ethnic descent. I. Kurds and Yemenites

Dental casts of 99 Kurdish and 98 Yemenite Jewish children evenly distributed between the sexes, aged 12 years, were measured for mesio-distal and buccolingual tooth dimensions, and arch depth and width. Dental dimensions showed significant differences between the two groups in certain permanent teeth in mesiodistal length, while in the buccolingual diameter the differences did not reach statistical significance. Dental arch form in Kurdish children was more rounded due to significantly bigger arch width, while arch depth was not significantly different from Yemenites. Intragroup sex differences were found in both groups with reference to arch dimensions, while in the dental parameters they were more strongly expressed in Kurdish children.     

Dental arch asymmetry in an isolated Adriatic community

Developmental stability reflects the ability of a genotype to develop in the same way under varying environmental conditions. Deviations from developmental stability, arising from disruptive effects of environmental and genetic stresses, can be measured in terms of fluctuating asymmetry, a particularly sensitive indicator of the ability to cope with these stresses during ontogeny. In an inbred Adriatic island population, we expected dental arch fluctuating asymmetry 1) to be higher than in an outbred sample from the same island, and 2) within this population, to increase with the level of inbreeding. Due to environmental stress, we also expected to find higher fluctuating asymmetry in the outbred island population than in an urban reference group from the same country. The material consisted of 506 dental casts of 253 children from 1) the island of Hvar, and 2) Zagreb, Croatia. Three-dimensional coordinates of 26 landmarks spanning the arches were digitized. The analysis partitioned the asymmetry of arch forms into components for directional and fluctuating bilateral asymmetry, using the appropriate Procrustes method (geometric morphometrics). The results corroborated the hypotheses. Fluctuating asymmetry was found to be higher on the island than in Zagreb in all groups and in both jaws, and increased significantly with endogamy level in the lower jaw. There was no significant directional asymmetry in the Zagreb sample and likewise none in the upper jaws of the outbred island group, but significant directional asymmetry in both jaws of the inbred population and also in the lower jaws of the outbred island group. These results suggest an environmental as well as a genetic influence on dental arch asymmetry. Although the lower jaws expressed these two stresses almost additively, the upper jaws appeared to be better buffered. The role of directional asymmetry as a potential indicator of craniofacial developmental instability clearly merits further attention.     

Variation in dental occlusion and arches among Melanesians of Bougainville Island, Papua New Guinea. II. Clinical variation, geographic microdifferentiation and synthesis

Patterns of geographic microdifferentiation for dental occlusion and the size and shape of the dental arches are described for 14 villages on Bougainville Island, Papua New Guinea. Occlusal variables, such as overjet, overbite, molar relationships, crowding or spacing, and malalignment vary less among villages than do arch length and width. Arch length and width decrease in size from north to south. The pattern of biological distance among villages for occlusal variables and arch size correspond poorly to anthropometric, linguistic, geographic and migrational distances. The value of occlusal variables and arch size for discriminating among populations, the biological interpretation of multivariate data and the objectives of research on geographic microdifferentiation are discussed.     

Human dental arch shape evaluated by Euclidean-distance matrix analysis

Form differences between biological structures can be evaluated using several approaches. When landmark data are available, a recently proposed method (euclidean-distance matrix analysis) seems to be able to differentiate between size and shape differences. This method also localizes those areas which differ most between the two structures. We have applied it to analyze the sexual dimorphism in dental arch form in a sample of 50 men and 45 women. Subjects ranged in age between 20 and 27 years, and had sound dentitions. Fourteen landmarks, corresponding to the centers of gravity (centroids) of the occlusal surfaces of all permanent teeth (right second molar to left second molar), were individualized on the dental casts of subjects. All the possible linear distances between pairs of teeth were computed, thus creating four mean form matrices (one for each arch within sex). Gender differences were tested by using euclidean-distance matrix analysis. No significant differences were demonstrated in the shape of arches, while male arches proved to be slightly bigger than female arches. © 1993 Wiley-Liss, Inc.     

金丝猴牙齿与体重间的相关性研究

对金丝猴牙齿与体重间关系的研究结果表明,在雄性中,无论是线性还是面积与颅长之间的相关关系均较雌性的更为紧密。而且,随着体重的增加,雄性牙齿的近中远中长(M/D)也比雌性的增长较快。在上、下颌中,上颌牙齿与颅长的关系表现出更强的相联性。与其他灵长类相比较,金丝猴在取食和咀嚼过程中主要利用颊齿;大的个体具有大的犬齿及一定比例的臼齿面积和齿弓(牙合)面面积;上齿弓(牙合)面面积大于下齿弓(牙合)面面积。也就是说上齿弓提供了比下齿弓更大的咀嚼面积。金丝猴牙齿与体重间的关系位于猴类和人猿类之间,更接近于大猩猩(Gorilla)、疣猴(Colobus)和猕猴。