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PubMedDate not supplied

Tooth crown fractures in 3-year-old Andalusian children.

PURPOSE: The purpose of this study was to determine the prevalence of tooth crown fractures affecting primary incisors of 3-year-old Andalusian children. METHODS: Clinicians examined 337 three-year-old children (mean age=3.6 years) of Seville, Andalusia, southern Spain. They examined the children for several dental and oral conditions, including tooth trauma. RESULTS: Crown fractures were found in 15% of the examined children. The prevalence of tooth crown fractures was significantly higher in males (18%) than in females (10%) (P=.04; odds ratio:0.5). In both genders, the upper central incisors had the most fractures, 77% in males and 71% in females. The most common crown fracture was found in enamel only (82%), followed by fracture into dentin (12%), and fracture involving the dental pulp (7%). CONCLUSIONS: Dentists have a responsibility to examine primary tooth injuries at the initial presentation of children because a dental injury to a primary tooth may include more severe injuries, such as dento-alveolar fractures.

Child, Preschool↗
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↗
PubMed1997

Third order tooth movements with straight wire appliances. Influence of vestibular tooth crown morphology in the vertical plane.

1. The labial surface in the vertical plane was investigated in 3 sections: center, mesial, and distal edge of an ideally positioned bracket. The material consisted of 28 casts taken from 14 female and male individuals with a mean age of 26.8 years. 2. After trimming each cast, the resulting surface was photocopied, enlarged 8 times, then digitized under a 2.0 mm grid (corresponding to 0.25 mm of the original size). 3. Using a statistical computer program, mean curves including standard deviations and non-linear regression curves were calculated from the individual data. In accordance with their anatomy 3 groups of teeth were formed in each jaw: front teeth, premolars, and molars. The curves, including the comparison of the squared regression curves, provide an accurate mathematical description of the labial tooth crown in the above-stated sections. 4. The angle differentials between a reference tangent and 20 other tangents were calculated. From a practical standpoint, information is obtained on the extent to which the torque of a tooth would be changed if a bracket was to be positioned vertically (in 0.5 mm increments) from its ideal position. These changes of torque fluctuate on average between 1.3 degrees (mandibular front teeth) and 3.3 degrees (mandibular molars) for every 0.5 mm of vertical deviation. 5. The calculated comparisons of the curves permitted the construction of bracket bases filling-at least in the vertical dimension-the tooth surface most accurately in the "optimal" position.

Adolescent↗
PubMed1991

Upper central incisor and canine tooth crown size in 47,XXY males.

Enamel and dentin thicknesses were measured in permanent tooth crowns of 47,XXY (Klinefelter syndrome) males. In 47,XXY males, enamel thickness in maxillary central incisors was significantly greater than that in control males or females, and dentin thickness in incisors and canines was significantly greater than that in control females, but smaller than that in normal males. These findings confirm the concept that human dental growth is affected by sex chromosomes. Amelogenesis is promoted by both X and Y chromosome genes, and sexual dimorphism in average tooth size is evidently determined by a promoting effect of the Y chromosome on dentin growth, probably through cell proliferation. This effect can also explain sex predilection for males in the numbers of supernumerary and ordinary teeth.

Amelogenesis↗
PubMed1991

Protective coatings for tooth crowns.

Transfer of technology to the dental office could provide thin polymeric coatings over tooth crowns and accessible root surfaces. These coatings can be prepared from relatively inexpensive, commercially available materials in one-step reactions. When the monomer technique becomes available, it will provide caries protection for all of your patients.

Benzoates↗
PubMed1987

A hypothetical model of genetic control of tooth-crown growth in man.

Twins and families were investigated to obtain information about inheritance of tooth-crown size. Sixty twin pairs and 100 families were examined using four methods of estimation. The results suggest genetically controlled interactions between tooth germs during their formation. A hypothetical model of odontogenesis is presented.

Humans↗
PubMed1992

Dental enamel growth, perikymata and hypoplasia in ancient tooth crowns.

This paper describes the hypoplastic defects commonly seen on the surface of ancient human tooth crowns, excavated from archaeological sites, and presents a new method for estimating the ages at which these defects were initiated during life. The method is based upon examination of microscopic incremental structures on the enamel surface and it is possible also to apply it to reconstruction of the sequence and timing of dental crown development. The method of examination is non-destructive and allows full use to be made of the large numbers of complete, unworn dentitions which are found amongst archaeological remains.

Archaeology↗
PubMed1994

Tooth crown size and morphology in Turner syndrome.

The aims of this investigation were to analyze permanent tooth crown size and morphology and to perform symmetry analysis between corresponding teeth on the right and the left side. The material comprised 32 Turner syndrome patients aged 7-16.7 years. As controls served 33 normal girls 10.2-16.7 years old. The mesiodistal diameter was significantly reduced for every tooth measured except for the maxillary canine. The buccolingual dimension was reduced only for some teeth. Eleven morphologic traits were defined. Ten of these were identified in the Turner patients; seven occurred in the controls as well, but at a lower frequency. Some of the traits have not been described earlier for this group of patients. There was a significant difference between Turner and control patients both in the number of patients with bilateral tooth asymmetries and in the number of corresponding tooth pairs in the maxilla with bilateral asymmetry. No significant differences were found between the 45X patients and the other karyotypes. Maxillary central incisors showed a surprisingly high relative frequency (38.5%) of bilateral asymmetry.

Adolescent↗
PubMed2001

Numerical simulation of the casting process of titanium tooth crowns and bridges.

The objectives of this paper were to simulate the casting process of titanium tooth crowns and bridges; to predict and control porosity defect. A casting simulation software, MAGMASOFT, was used. The geometry of the crowns with fine details of the occlusal surface were digitized by means of laser measuring technique, then converted and read in the simulation software. Both mold filling and solidification were simulated, the shrinkage porosity was predicted by a "feeding criterion", and the gas pore sensitivity was studied based on the mold filling and solidification simulations. Two types of dental prostheses (a single-crown casting and a three-unit-bridge) with various sprue designs were numerically "poured", and only one optimal design for each prosthesis was recommended for real casting trial. With the numerically optimized design, real titanium dental prostheses (five replicas for each) were made on a centrifugal casting machine. All the castings endured radiographic examination, and no porosity was detected in the cast prostheses. It indicates that the numerical simulation is an efficient tool for dental casting design and porosity control.

Journal Article↗
PubMed1997

Non-metric tooth crown traits of the Thai, Aka and Yao tribes of northern Thailand.

A survey was made of Thai tribe members, who cultivate rice paddies in the flatlands of northern Thailand, and of the Aka and Yao tribes, who farm with the slash-and-burn method in a mountainous region of northern Thailand. Plaster casts of the upper and lower jaws of tribe members were taken. Seventeen non-metric traits of their tooth crowns were classified and compared with other Mongoloid populations in various regions and periods. It was observed that the Thai tribe had the Sundadont characteristics, typical of South-East Asians, but the Aka and Yao tribe had more Sinodont than Sundadont characteristics, typical of North-East Asians. The regional and temporal variations of crown morphology in South-East Asia suggest earlier setting of the Thai tribe than the Aka and Yao tribes in this region. Moreover, comparison of the tooth morphological and linguistic classifications contradicts the traditional theory of the genealogy of the Thai language family. On the subject of the origin of modern South-East Asians, it is suggested that there has not been a gene flow of Sinodonty into Sundadonty of the principal ethnic groups in Neolithic South-East Asia.

Asian People↗
PubMed2004

Patterns of tooth crown size and shape variation in great apes and humans and species recognition in the hominid fossil record.

It has been suggested that patterns of craniodental variation in living hominids (Gorilla, Homo, Pan, and Pongo) may be useful for evaluating variation in fossil hominid assemblages. Using this approach, a fossil sample exhibiting a pattern of variation that deviates from one shared among living taxa would be regarded as taxonomically heterogeneous. Here we examine patterns of tooth crown size and shape variation in great apes and humans to determine 1) if these taxa share a pattern of dental variation, and 2) if such a pattern can reliably discriminate between samples that contain single species and those that contain multiple species. We use parametric and nonparametric correlation methods to establish the degree of pattern similarity among taxa, and randomization tests to assess their statistical significance. The results of this study show that extant hominids do not share a pattern of dental size variation, and thus these taxa cannot be used to generate expectations for patterns of size variation in fossil hominid species. The hominines (Gorilla, Homo, and Pan) do share a pattern of shape variation in the mandibular dentition; however, Pongo is distinct, and thus it is unclear which, if either, pattern should be expected in fossil hominids. Moreover, in this case, most combined-species samples exhibit patterns of shape variation that are similar to those for single hominine species samples. Thus, although a common pattern of shape variation is present in the mandibular dentition, it is not useful for recognizing taxonomically mixed paleontological samples.

Animals↗
PubMed1992

Nonmetric tooth crown traits in the Ami tribe, Taiwan aborigines: comparisons with other east Asian populations.

The frequencies of occurrence of 17 tooth crown traits in the living Ami tribe, which inhabits the east coast of Taiwan, were investigated and compared with other East Asian populations based on Turner's (1987) Mongoloid dental variation theory. Principal coordinate analysis based on Smith's mean measure of divergence using frequencies of the 17 traits suggests that the Ami tribe together with the Yami tribe and the Bunun tribe is included in the sinodont group typical of the Chinese mainland and northeast Asia. In light of these results and the estimated distribution of sinodonty and sundadonty in the past and the present, we speculate that the gene flow from Chinese mainlanders to native sundadonts, who seem to have migrated northward to Taiwan, contributed significantly to the formation of the living Taiwan aboriginal groups, sinodonts. Among the aboriginal tribes of Taiwan, the Ami have characteristics intermediate between those of the Yami and the Bunun. The relative positions of these tribes in East Asian populations suggests that the extent of sinodontification and of genetic isolation is one of the causes of the intertribal variation.

Adolescent↗