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At least 19 recordsLinked to original sources
PubMed1991

Tooth crown heights, tooth wear, sexual dimorphism and jaw growth in hominoids.

The aim of this review is to bring together data that link tooth morphology with tooth function and tooth growth: We aim to show how the microanatomy of hominoid teeth is providing evidence about rates of tooth growth that are likely to be a consequence of both masticatory strategy and social behaviour. First, we present data about incisor and molar tooth wear in wild short chimpanzees that demonstrate how crown heights are likely to be related to relative tooth use in a broad sense. Following this we review recent studies that describe the microanatomy of hominoid tooth enamel and show how these studies are providing evidence about tooth crown formation times in hominoids, as well as improving estimates for the age at death of certain juvenile fossil hominids. Next, we outline what is known about the mechanisms of tooth growth in the sexually dimorphic canine teeth of chimpanzees and compare these patterns of growth with tooth growth patterns in the canines of three fossil hominids from Laetoli, Tanzania. Finally, we discuss how selection pressures that operate to increase or reduce the size of anterior teeth interact with jaw size. We argue that the space available to grow developing teeth in the mandibles of juvenile hominoids is determined by the growth patterns of the mandibles, which in turn reflect masticatory strategy. The consequences of selection pressure to grow large or small anterior teeth are likely to be reflected in the times at which these teeth are able to emerge into occlusion.

Animals↗
PubMed2001

Permanent tooth crown dimensions in prematurely born children.

AIM: The aim was to examine the effect of preterm birth on permanent tooth crown dimensions. MATERIALS AND METHODS: The data consisted of 328 prematurely born white and black children and 1804 control children who participated in the cross-sectional study of the Collaborative Perinatal Project (USA) in the early 1960s and 1970s. The dental examinations were carried out in a standardized fashion at ages varying from 6 to 12 years in 95% of cases. Tooth crown size measurements were performed on the dental casts with an electronic measuring device and readout by two experienced observers according to precise definitions generally quoted in the anthropological and genetic literature. The preterm and control groups were divided by sex and race. RESULTS: The results show both increased and decreased tooth crown dimensions in the prematurely born children. Significantly increased dimensions were found in the means of the intercuspal distances of the first permanent molars in the white boys and in the mesiodistal dimensions (MD) of the lower lateral incisors and the upper left first molar in the black girls. By contrast, there were decreased intercuspal distances, MD and labiolingual (LL) tooth crown dimensions in the white girls and black boys. The statistical method used was the Mann-Whitney's U-test (Willcoxon Rank-Sums test). CONCLUSIONS: The findings partly support previous reports of decreased tooth crown dimensions in preterm infants, but the increased dimensions found in the preterm white boys and black girls differ from earlier reports. Our results indicate the importance of environmental factors including neonatal factors in determining permanent tooth crown dimensions. Growth patterns, the buffering capacity and the timing of sensitive moments in tooth crown volume gain may vary between the sexes and ethnic groups and the possible effect of the accelerated growth period in preterm infants (catch-up growth) may influence the determination of permanent tooth crown dimensions.

Adolescent↗
PubMed1989

[Study on determination of the imaginary axis of the tooth crown in anterior teeth: 1].

1. The state of inclination and the change under various conditions of the imaginary axis of the tooth crown of upper jaw anterior teeth can be determined by the image measuring system and method of this study. 2. The measurement error of this system was not more than 0.3 degree. This value was sufficient for the purpose of this study. 3. The imaginary axis of the tooth crown of anterior teeth was determined on the study cast with 1 to 3 degrees in mesiodistal direction and 2 to 4 degrees in labiopalatal direction as standard deviation. 4. The imaginary axis of the tooth crown of anterior teeth was determined toward labial in the random position and toward patient's right and palatal in Standing Posture. 5. It was confirmed that the determination of the imaginary axis of tooth crown was effected by the position of the patient relative to the operator, limitation or direction of view, and approach direction.

Humans↗
PubMed1991

Tooth crown size in 46, X, i (Xq) human females.

Permanent tooth crown sizes of six Finnish females with a 46, X, i(Xq) chromosome constitution (isochromosome for the long arm of the X chromosome) were measured from dental casts and compared with those of normal women, first-degree female relatives and 45, X females. Crown diameters of the 46, X, i(Xq) females were not only smaller than in the normal women but even smaller than the 45, X females. These findings can be considered indirect evidence that X chromosome gene(s) for tooth crown growth are most probably located on the short arm.

Chromosome Aberrations↗
PubMed2000

[A newly developed method for taking pictures of tooth crown cracks for clinical records].

It is very important to examine fine cracks on the crown surface of traumatized tooth in the dental clinic because the presence of these cracks may cause discomfort or hypersensitivity of the tooth. By the emission of routinely used light, it is difficult to illuminate cracks, and the usual intraoral photography using strobe light emission is not useful to make records of cracks in most cases. In the present study, a method for taking pictures to record tooth crown cracks was newly developed using LED as a light source, and applied to patients with traumatized teeth in the dental clinic. The results were as follows: 1. Cracks on the tooth surface could be confirmed with the LEDs of all the colors used in this study. However, the blue LED enabled cracks in the incisal edge part to be more easily confirmed, and the white LED enabled cracks in the cervical part to be more easily confirmed. 2. Cracks of multiple modalities on the tooth surface was illuminated more often when the LED light was emitted at 45 degrees to the axis of the tooth than 90 degrees. 3. The light exposure field became wider by the use of the LED of diameter 5 mm than that of diameter 3 mm. However, the LED of diameter 3 mm was more favorable than that of diameter 5 mm for the observation of the cracks because the former could more easily change the direction of light emission.

Child↗
PubMed2001

Tissue contributions to sex and race: differences in tooth crown size of deciduous molars.

This study describes size of constituent deciduous tooth crown components (enamel, dentine, and pulp) to address the manner in which males characteristically have larger teeth than females, and the observation that teeth of American blacks are larger than those of American whites. Measurements were collected (n = 333 individuals) from bitewing radiographs using computer-aided image analysis. Tissue thicknesses (enamel, dentine, pulp) were measured at the crown's mesial and distal heights of contour. Deciduous mesiodistal molar crown length is composed of about 1/7 enamel, 1/3 dentine, and 1/2 pulp. Details differ by tooth type, but males typically have significantly larger dentine and pulp dimensions than females; there is no sexual dimorphism in marginal enamel thickness. Males scale isometrically with females for all variables tested here. Blacks significantly exceed whites in size of all tissues, but tissue types scale isometrically with blacks and whites with one exception: enamel thickness is disproportionately thick in blacks. While the absolute difference is small (5.56 mm of enamel in blacks summed over all four deciduous molar tooth types vs. 5.04 mm in whites), the statistical difference is considerable (P < 0.001). Aside from enamel, crown size in blacks is increased proportionately vis-à-vis whites. Principal components analysis confirmed these univariate relationships and emphasizes the statistical independence of crown component thicknesses, which is in keeping with the sequential growth and separate embryonic origins of the tissues contributing to a tooth crown. Results direct attention to the rates of enamel and dentine deposition (of which little is known), since the literature suggests that blacks (with larger crowns and thicker enamel) spend less time in tooth formation than whites.

Anthropology, Physical↗
PubMed1994

[Psychophysical scaling of translucent sensory measurement of tooth crowns].

The purpose of this study is to investigate the translucent sensory measurement as a basic study for developing the translucent sensory scale (Haze Guide) of tooth crowns. Seven subjects with normal visual sensation were examined to search for the translucent sensory interval of uncertainty using methods of limits, and 3 panels were selected from this result and prepared for further experiments. Fact-findings of the translucent senses were performed on these 3 panels using the magnitude estimation method and the absolute judgement method. With these methods we were able to construct the translucent sensory measurement and to establish the ranges of Haze scores and magnitude of each step and a permitted limit of each Haze tab, which should be possessed with the tooth crown translucent sensory scale. The results were as follows: 1. The translucent senses were well adapted to the Stevens power law of modality characteristic exponent. The exponent was 1.74. 2. Standard light translucent sensory guide for tooth crowns were in the range between 25. 2% and 91.9% at Haze values. Eighteen steps were arranged within this range, and when the Haze difference was taken larger at lower Haze values and the difference was taken smaller accordingly at higher values, the visual sensation came to achieve an equally appearing interval of translucency.

Adult↗
PubMed1991

[Interrelation of tooth crown diameters].

The purpose of this study was to clarify the interrelation of the tooth crown diameters using statistical methods. The material consisted of 414 dental casts from orthodontic patients in the Japanese female. The mesiodistal diameters of all permanent teeth on the left side were measured, excluding the third molars. These values were examined by correlation coefficient matrix and multivariate analyses such as multiple regression, principal component and canonical correlation, etc. The results were as follows: 1) The tooth crown diameters showed a strong intercorrelation within each jaw and between both jaws. 2) When the incisors and the canine were large in size, the premolars and the molars tended to be small. 3) When the incisors and the molars were large in size, the canine and the premolars tended to be small. 4) When the incisors and the premolars were large in size, the canine and the molars tended to be small. 5) All of the teeth except the upper lateral incisor were classified according to size into the four groups of incisors, canines, premolars and molars. 6) The dentition with small teeth tended to show a spaced arch.

Crowns↗
PubMed1989

[Resemblance of nonmetrical trait of tooth crown among siblings and between parents and children].

An elaborate observation and comparative study was made on the degree of resemblance among siblings, and parents and their children employing, as a means of investigation, the tooth crowns of the plaster casts of upper and lower jaws obtained from the inhabitants of Kamiina District, Nagano Prefecture. The comparisons were made between the right and left sides of an individual and also free pairs of individuals taken at random. To reach a decision on the degree of resemblance, the following factors were utilized: the degree of resemblance, interfamily correlation, and the percentage of heredity. Genealogies were also taken into consideration in some cases of tooth crowns. The main point of the results of this study is that the degree of resemblance among siblings, parents and their children differs according to the kind of tooth crown. 1. The degree of resemblance was most remarkable in the case of the following four morphological peculiarities the labial relief of incisors (I1, I2), shovel shaped incisors (I1), basal tubercle (C'), and mesial interstitial tubercle (P1). 2. Not so much as the four morphological peculiarities mentioned above but still considerable was the degree of resemblance on the singular tubercle of the Carabelli tubercle (M1), protostylid (M1), sixth cusp (M1), etc., and the tetracuspid type of the second lower molars, basal tubercle (I1). These were followed by the interstitial tubercle (P2) and the tricuspid type of the second upper molar with only a slight difference. 3. Resemblance of the basal tubercle (I2), Carabelli tubercle (M2), protostylid (M2), sixth cusp (M2), reduction of the upper lateral incisor, or Metacone reduction (M2) was rarely observed. 4. Resemblance between the permanent teeth of a mother and the deciduous teeth of her child was also rare, except the shovel shaped ones. 5. Generally, the degree of resemblance decreased in the following order: between the right and left sides, between siblings, between parents and their children, and finally, among unrelated pairs. Most outstanding was the resemblance between the right and left sides.

Adolescent↗
PubMed1997

Relationship of enamel hypoplasia to the pattern of tooth crown growth: a discussion.

The defects of enamel hypoplasia can be related to the layered structure of enamel which represents the sequence of development in tooth crowns. From such studies, it is possible to see that furrow-type enamel defects (the most common form of hypoplasia seen with the naked eye) are just the most prominent expression of a continuum which extends ever smaller, down to a microscopic disturbance to a single layer in the crown formation sequence. Furthermore, the progressive decrease in spacing between development layers which occurs down the crown sides, from occlusal to cervical, affects both the prominence and apparent width of the defects. This makes it difficult to use measurements as a means of estimating the duration of the disturbance causing a particular defect. The difficulty is even greater for the less common pitted or exposed-plane-type defects, for which the apparent width bears very little relationship with the duration of the growth disturbance. The defects of enamel hypoplasia can therefore be understood clearly only when examined under the microscope in relation to the structures which mark the development sequence of the tooth crown.

Anthropometry↗
PubMed1997

Normal faciolingual inclinations of tooth crowns compared with treatment groups of standard and pretorqued brackets.

Faciolingual inclinations of tooth crowns were measured on plaster casts of normal occlusions and posttreatment orthodontic models of treated cases. Normal anatomic occlusion, standard edgewise and Roth bracket groups of 10 subjects were examined for a change in torque values. On study models, crown inclinations of right and left central teeth to second molar in the upper and lower dental arches were measured to the functional occlusal plane and mean tooth inclinations were calculated. In normal occlusion group, upper central and lateral teeth inclined lingually, lower central teeth inclined slightly labially and lower lateral teeth inclined lingually but the standard deviations of mean values for upper and lower anterior teeth were high. Upper posterior teeth, from canine to molar, had a lingual inclination and lower posterior teeth had a progressively increasing lingual inclination from lateral to molar teeth. In treatment groups, upper central and lateral teeth had labial crown inclination and lower molar teeth had more lingual inclination as compared with the normal occlusion group. No significant variation was found between the mean torque values of standard and Roth treatment groups.

Adolescent↗
PubMed1993

Small primary tooth-crown size in low birthweight children.

As part of a longitudinal study of dental development in a group of low birthweight children (LBW), study models of 72 children at age 7 years were measured to determine the tooth-crown size of primary molars and canines and to compare the findings with equivalent measurements in 60 normal birthweight (NBW) controls. Mesiodistal (length) and buccolingual (width) dimensions were measured manually, using dial calipers. Primary canines and molars were smaller in the LBW than the controls, with significance values ranging from P < 0.001 for the mesiodistal dimension of maxillary and mandibular canine (> 4% difference) to a non-significant difference P < 0.2 for the buccolingual dimension mandibular first primary molar (1.8% difference). Within the LBW group there was a positive correlation between birthweight and mesiodistal tooth size. Small primary tooth size in LBW children may be influenced by both genetic and environmental factors. The shorter prenatal growth period and poor perinatal and early postnatal development may influence the developing deciduous dentition. Small primary tooth-crown size, associated with LBW, should be considered in all population studies of tooth size.

Child↗
PubMed1994

Maternal smoking and tooth formation in the foetus. II. Tooth crown size in the permanent dentition.

Altogether 2159 pregnancies among black and white Americans in the Collaborative Perinatal Study and dental casts from their children at the age of 6-12 years were studied to determine the effect of maternal smoking on permanent tooth crown dimensions. A trend of reduction, similar to that observed in the deciduous second molars, was found in the permanent first molars and also in the mesio-distal dimension of permanent incisors in relation to sex and race of the children and smoking habits of the mother. In terms of peak in their mitotic growth, the results can be interpreted to indicate a sensitive period of intra uterine development from the 24th to 28th gestational weeks. Comparisons of postnatal body size and differential correlation patterns in affected tooth dimensions with early postnatal body and head size between smokers and non-smokers, suggests that maternal smoking during pregnancy may have an effect on basic growth of the head and body and/or the developmental process that impacts tooth development at some specific sensitive period also during the postnatal formation of these tooth crowns.

Birth Weight↗