Dentition Patterns Research Articles

Prevalence of normal occlusion traits in deciduous dentition

The aim of this research was to study the normal occlusal patterns of deciduous dentition in Brazilian preschool children. The sample consisted of 356 preschool children, of both genders, aged 3-5 1/2 years from the urban zone of Salvador, Bahia. The occlusion exam was carried out by two examiners, in the classroom, utilizing a wooden spatula. The data were analyzed by the statistical program EPI-INFO 6.02 using the Chi-squared test. The frequency of the type I arch was 43.3% for the upper and 46.3% for the lower arch. The frequency of the type II arch was 56.7% for the upper and 53.75 for the lower arch, however, no difference between genders was noticed. The distribution of primate spaces was: 89.9% for the upper and 67.1% for the lower arch. This prevalence decreased significantly as age increased (p < 0.01). Normal canine relationship was found in almost 60% of the children for the right and left sides. Out of 712 evaluated terminal planes, 55.9% presented mesial terminal step for the primary second molars, 37.9% straight terminal plane and 6.2% distal step. The results permitted to conclude that the presence of generalized spacing between incisors, commonly described by other authors, was not the most prevailing condition for both arches in this sample. On the other hand, primate spaces were the most common ones. The most frequent normal occlusal patterns for canine and molar relationships were found to be the Class I patterns.

Development of the pattern of dentition and dental laminae of costa rican plethodontid salamanders (Amphibia: Urodela)

The pattern of development of teeth and dental laminae of three Costa Rican plethodontids (Amphibia, Urodela, Plethodontidae) was investigated using transparent preparations, light microscopy and scanning electron microscopy. The teeth of the jaws are monostichously positioned, those of the posterior vomeral parts are polystichously arranged. The anterior vomeral parts carry monostichously positioned teeth at the caudal margin; yet, the adult Bolitoglossa subpalmata possesses two lines. As a sex dimorphism adult males display long monocuspid premaxillary teeth which protrude to the outside of the mouth cavity. All species studied possess paired dental laminae in the lower jaw. Nototriton abscondens possesses an unpaired dental lamina in the upper jaw, which is constricted between the unpaired premaxillary and the maxillaries. In contrast, the dental laminae in the upper jaw of B. subpalmata and Oedipina uniformis are segmented into a premaxillary and two maxillary laminae. All species possess a pair of anterior vomeral and a pair of posterior vomeral dental laminae in the adults, whereas the vomeral dental laminae of the subadults are unsegmented. The pattern of dentition is compared with that of Gyrinophilus and Eurycea.

Independent regulation of Dlx2 expression in the epithelium and mesenchyme of the first branchial arch.

Dlx2, a member of the distal-less gene family, is expressed in the first branchial arch, prior to the initiation of tooth development, in distinct, non-overlapping domains in the mesenchyme and the epithelium. In the mesenchyme Dlx2 is expressed proximally, whereas in oral epithelium it is expressed distally. Dlx2 has been shown to be involved in the patterning of the murine dentition, since loss of function of Dlx1 and Dlx2 results in early failure of development of upper molar teeth. We have investigated the regulation of Dlx2 expression to determine how the early epithelial and mesenchymal expression boundaries are maintained, to help to understand the role of these distinct expression domains in patterning of the dentition. Transgenic mice produced with a lacZ reporter construct, containing 3.8 kb upstream sequence of Dlx2, led to the mapping of regulatory regions driving epithelial but not mesenchymal expression in the first branchial arch. We show that the epithelial expression of Dlx2 is regulated by planar signalling by BMP4, which is coexpressed in distal oral epithelium. Mesenchymal expression is regulated by a different mechanism involving FGF8, which is expressed in the overlying epithelium. FGF8 also inhibits expression of Dlx2 in the epithelium by a signalling pathway that requires the mesenchyme. Thus, the signalling molecules BMP4 and FGF8 provide the mechanism for maintaining the strict epithelial and mesenchymal expression domains of Dlx2 in the first arch.

Dynamics of tooth formation and replacement in the zebrafish (Danio rerio) (Teleostei, Cyprinidae).

We have used three-dimensional reconstructions from serial sections as well as cleared and stained specimens to infer patterning of the pharyngeal dentition throughout ontogeny in the zebrafish. Each pharyngeal tooth has been monitored from its initiation to its complete disappearance (resorption and shedding). We have identified tooth families and have studied the persistence of the pattern through successive replacements. Teeth arise in two seemingly independent clusters, a ventral and a dorsal cluster, with differing patterning features. The ventral cluster consists of one row of five teeth in which a tooth is first initiated in position four, and subsequent teeth in adjacent positions, posterior and anterior to it. Replacement teeth in odd and even positions are initiated simultaneously during successive odontogenic waves but differ in generation number according to the timing of appearance of the first-generation tooth, i.e., the founder of the tooth family. Up to four teeth of a single tooth family are simultaneously present in early juveniles of which two are usually "co-functional." The number of teeth per tooth family is reduced in older juveniles and adults, reflecting a slowing down of the replacement rate. The consistent way in which the pattern is established and maintained during ontogeny calls for research of the presence of specific molecular controls.

Comparative study of dentition among species of Poecilia (Pisces).

Many studies in the genus Poecilia have focused on reproductive and genetic characteristics of Poecilia formosa, the Amazon molly, and its sympatric species P. latipinna and P. mexicana. The research literature of Poecilia dentition has been limited to general tooth morphology. Essentially absent are comparative analyses of dentition patterns and total numbers of teeth. The current study uses dentition analysis as a method to compare species in the genus Poecilia and to address some taxonomic issues related to these fish. The study focused on fish from the areas of southern Texas and northeastern Mexico. Through the use of scanning electron microscopy, the lower jaws of Poecilia spp were examined to determine total numbers of outer and inner teeth. In addition, the differences in distribution patterns of the inner teeth were recorded and compared. Statistical analyses were performed to determine which comparisons were significant. This study reveals several observations: 1) variations in the numbers of outer and inner teeth exist in some of these fish with respect to site of collection; 2) differences in total teeth numbers and dentition patterns were found both interspecifically and intraspecifically; and 3) in addition, dentition analysis provided evidence regarding the origin of P. formosa. This study supports the current notion that P. latipinna, the proported paternal component, and P. mexicana limantouri, the purported maternal component, are the progenitor species of P. formosa. Two unresolved taxonomic questions were addressed through dentition analysis. First, the present study supports the exclusion of the triploid associate of P. formosa as a separate species from P. formosa. Second, this study shows a significant difference in the number of inner teeth and in dentition patterns between P. mexicana limantouri and P. mexicana mexicana. Such differences, in addition to previously known distinguishing characteristics, should prompt careful consideration of whether or not these taxa deserve specific status or retention of their current subspecific status. J. Morphol. 239:271-282, 1999. © 1999 Wiley-Liss, Inc.

Activin is an essential early mesenchymal signal in tooth development that is required for patterning of the murine dentition.

Development of the mammalian tooth has been intensively studied as a model system for epithelial/mesenchymal interactions during organogenesis, and progress has been made in identifying key molecules involved in this signaling. We show that activin betaA is expressed in presumptive tooth-germ mesenchyme and is thus a candidate for a signaling molecule in tooth development. Analysis of tooth development in activin betaA mutant embryos shows that incisor and mandibular molar teeth fail to develop beyond the bud stage. Activin betaA is thus an essential component of tooth development. Development of maxillary molars, however, is unaffected in the mutants. Using tissue recombination experiments we show that activin is required in the mesenchyme prior to bud formation and that although activin signaling from mesenchyme to epithelium takes place, mutant epithelium retains its ability to support tooth development. Implantation of beads soaked in activin A, into developing mandibles, is able to completely rescue tooth development from E11.5, but not E12.5 or E13.5, confirming that activin is an early, essential mesenchyme signal required before tooth bud formation. Normal development of maxillary molars in the absence of activin shows a position specific role for this pathway in development of dentition. Functional redundancy with activin B or other TGFbeta family members that bind to activin receptors cannot explain development of maxillary molars in the mutants since the activin-signaling pathway appears not to be active in these tooth germs. The early requirement for activin signaling in the mesenchyme in incisor and mandibular molar tooth germs must be carried-out in maxillary molar mesenchyme by other independent signaling pathways.

Distribution patterns of primary and permanent dentition in children with unilateral complete cleft lip and palate.

To investigate the distribution patterns of primary and permanent teeth in the cleft area and the numerical variation in teeth in unilateral complete cleft lip and palate (UCLP) patients. A survey of the dentition in UCLP patients. Craniofacial Center, Chang Gung Memorial Hospital, Taipei, Taiwan. 137 UCLP patients who met the following criteria: (1) have had at least one panoramic film taken, (2) the first panoramic film illustrates either primary or early mixed dentition. Evaluation of both permanent and primary dentition was available in 91 cases. Two evaluators performed independent evaluations of number and distribution of teeth in UCLP patients. The hypothesis that there are two odontogenic origins for maxillary lateral incisors was proposed to explain the occurrence of distribution patterns of dentition in the cleft area and to explain differences between primary and permanent dentition in UCLP patients. Four distribution patterns in the cleft area were identified in both the primary and the permanent dentition. In the primary dentition, placement of the lateral incisor distal to the alveolar cleft was the predominant pattern (pattern y, 82.4%), followed by absence of the cleft side maxillary lateral incisor (pattern ab, 9.9%), presence of one tooth on each side of the alveolar cleft (pattern xy, 5.5%), and placement of the lateral incisor mesial to the alveolar cleft (pattern x, 2.2%). In the permanent dentition, the most common pattern was the absence of the maxillary lateral incisor on the cleft side (pattern AB, 51.8%), followed by lateral incisor placement distal to the alveolar cleft (pattern Y, 46%), lateral incisor placement mesial to the alveolar cleft (pattern X, 1.5%) and the presence of one tooth on each side of the alveolar cleft (pattern XY, 0.7%). The discrepancy between the distribution patterns of primary dentition and permanent dentition successors is 57.1%. Variations in tooth number in both primary and permanent dentition of UCLP patients occurred most often in the cleft area. Abnormalities in the number of teeth (hypodontia or hyperdontia) outside the cleft area were more common in the permanent dentition than in the primary dentition (24.1% versus 4.4%). Four distribution patterns in the cleft area were identified in both sets of dentition. Our findings of distribution patterns in UCLP patients support the hypothesis that there may be two odontogenic origins for maxillary lateral incisors. Clinicians involved in managing the dentition of UCLP patients should consider the high frequency of numerical variation both in and outside the cleft area before starting dental treatment.

Distribution Patterns of Primary and Permanent Dentition in Children with Unilateral Complete Cleft Lip and Palate

Distribution Patterns of Primary and Permanent Dentition in Children with Unilateral Complete Cleft Lip and Palate

Molecular control of odontogenic patterning: positional dependent initiation and morphogenesis.

We have previously proposed that the patterning of the mammalian dentition is determined by an odontogenic homeobox code, whereby positional specification of odontogenic ectomesenchymal cell populations in a given region of the first branchial arch are determined by the combination of different homeobox genes expressed, described in detail in (1). Here we describe the first functional evidence for such a mechanism, and show that development of different types of teeth is controlled by independent genetic pathways. We suggest a mechanism whereby patterning is determined by position dependent control of tooth germ initiation, and propose that the pathway of morphogenesis is directly linked to the early mesenchymal expression of homeobox genes.

Expression of the transcription factors Otlx2, Barx1 and Sox9 during mouse odontogenesis.

The molecular mechanisms governing the decision between molariform and incisiform patterns of rodent dentition are not yet known. Transcription factors are regulators of regionally specific morphogenesis and key co-ordinators of gene activity during developmental processes. Here, we analysed the expression of several transcription factors during mouse tooth development. Otlx2/Rieg is a homeobox gene involved in Rieger syndrome, a human disorder characterized by dental hypoplasia. Otlx2/Rieg expression distinguishes stomatodeal epithelium well before tooth initiation, and thereafter its expression becomes restricted to the epithelia of both molar and incisor primordia. The recently identified homeodomain transcription factor Barx1 is first expressed in mesenchyme of the first branchial arch, but during advanced developmental stages the gene is exclusively expressed in the mesenchyme of molar primordia. Finally, the Sry-related transcription factor Sox9 is expressed in epithelial components and to a lesser degree in condensed mesenchyme of the developing teeth. These results suggest that Otlx2/Rieg, Barx1, and Sox9 participate in the hierarchical cascade of factors involved in the regulation of tooth morphogenesis.

Patterning of the murine dentition by homeobox genes

Homeobox genes have been shown to be important for the regulation of pattern formation of many systems during embryogenesis. Overlapping domains of Hox gene expression in the paraxial mesoderm have been suggested to create a combinatorial code of expression (Hox code) specifying the structures of individual segments such as the vertebrae. Hox genes are not expressed in the neural crest cells contributing to tooth formation, and so a Hox code can not be involved in patterning the dentition. It has previously been proposed that other, non-Hox homeobox genes may pattern the dentition. Expression data in this paper shows that there is a pattern of overlapping domains of homeobox gene expression in facial mesenchyme prior to the initiation of tooth development. We propose that expression of these genes constitutes an odontogenic homeobox code which patterns the dentition.

Role of Dlx-1 and Dlx-2 genes in patterning of the murine dentition.

The molecular events of odontogenic induction are beginning to be elucidated, but until now nothing was known about the molecular basis of the patterning of the dentition. A role for Dlx-1 and Dlx-2 genes in patterning of the dentition has been proposed with the genes envisaged as participating in an 'odontogenic homeobox gene code' by specifying molar development. This proposal was based on the restricted expression of the genes in molar ectomesenchyme derived from cranial neural crest cells prior to tooth initiation. Mice with targeted null mutations of both Dlx-1 and Dlx-2 homeobox genes do not develop maxillary molar teeth but incisors and mandibular molars are normal. We have carried out heterologous recombinations between mutant and wild-type maxillary epithelium and mesenchyme and show that the ectomesenchyme underlying the maxillary molar epithelium has lost its odontogenic potential. Using molecular markers of branchial arch neural crest (Barx1) and commitment to chondrogenic differentiation (Sox9), we show that this population alters its fate from odontogenic to become chondrogenic. These results provide evidence that a subpopulation of cranial neural crest is specified as odontogenic by Dlx-1 and Dlx-2 genes. Loss of function of these genes results in reprogramming of this population of ectomesenchyme cells into chondrocytes. This is the first indication that the development of different shaped teeth at different positions in the jaws is determined by independent genetic pathways.

Patterning of the mammalian dentition in development and evolution.

The mammalian dentition is a segmented organ system with shape differences among its serially homologous elements (individual teeth). It is believed to have evolved from simpler precursors with greater similarities in shape among teeth, and a wealth of descriptive data exist on changes to the dentition that have occurred within mammals. Recent progress has been made in determining the genetic basis of the processes that form an individual tooth, but patterning of the dentition as a whole (i.e. the number, location and shape of the teeth) is less well understood. In contrast to similarly organized systems, such as the vertebral column and limb, Hox genes are not involved in specifying differences among elements. Nevertheless, recent work on a variety of systems is providing clues to the transcription factors and extracellular signalling molecules involved.

Sexual dimorphism in the canines and skulls of carnivores: effects of size, phylogency, and behavioural ecology

Sexual dimorphism in craniodental features is investigated in a sample of 45 carnivore species in relation to allometry, phylogeny, and behavioural ecology. Dimorphism is more pronounced in both upper and lower canine size and strength than in carnassial size, skull dimensions and biomechanical features, but all dimorphism indices covary. As with most morphological characters, differences in canine sexual dimorphism are significantly related to phylogeny, estimated from either taxonomic rankings or a limited matrix of molecular distances; in particular, mustelids, felids and procyonids are more dimorphic than other carnivore families. Thus, because of problems related to species dependence in comparative data, remaining analyses are based on phylogenetically transformed values using a spatial autoregressive method.In contrast to other mammals, sexual dimorphism in carnivore canines is not correlated with differences in body weight, skull length or basicranial axis length. Nor is it correlated with categorical variables of activity pattern, habitat, or diet. In our Carnivore sample, canine dimorphism is related only to breeding system: uni‐male, group‐living (harem) species have significantly greater canine dimorphism than multi‐male, multi‐female groups and monogamous pair‐bonding species. By contrast, dimorphism in carnassial size is related to dietary differences, specifically greater dimorphism in meat‐eating species, and not breeding patterns. Dimorphism in estimates of jaw muscle size suggest functional demands from both diet and breeding type. It is concluded that, befitting patterns of heterodont dentition, sexual selection influences variation in canine dimorphism while feeding ecology is related to carnassial dimorphism.

Appearance pattern of tooth germs with developmental process inMylopharyngodon piceus

The pharyngeal dental formula ofMylopharyngodon piceus is 4–5 as a rule, and the dentition is asymmetrical. It is difficult to identify each tooth in the larval dentition. In this paper the appearance pattern of tooth germ with development process in this fish is described in detail. The formation pattern of the left dentition is contrasted with that of the right one. In the developmental process, the left pharyngeal dentition lacks teeth at position An3. Thus the left dentition is D-type as designated by Nakajima (1984), while the right one is A-type.

Late development of supernumerary teeth: a report of two cases

Two cases are presented of late developing supernumerary teeth. In the first the patient developed two crops of supernumeraries, both of which were found on radiographic examination following delay in the normal eruption pattern of the permanent dentition. The first crop of four supernumerary teeth were in the maxillary incisor region and were surgically removed; 5 years later four more supernumerary teeth was found in the maxillary canine and mandibular premolar regions, which were also surgically extracted. In the second case two supplemental mandibular premolars were found as an incidental finding on radiographic examination at the age of 15 years following orthodontic treatment, the patient having previously had four first premolars extracted; these supernumerary teeth were not extracted as they were asymptomatic. These cases emphasize the importance of careful review of patients with a history of supernumerary teeth and, where clinically indicated, of further radiographic examination.

Dentition patterns among Pacific and Western Atlantic butterflyfishes (Perciformes, Chaetodontidae): relationship to feeding ecology and evolutionary history

Dentition patterns among Pacific and Western Atlantic butterflyfishes (Perciformes, Chaetodontidae): relationship to feeding ecology and evolutionary history

Modalities of brooding and morphogenesis of larvae in Ostrea puelchana (D'Orbigny) under experimental rearing

Ostrea puelchana is a larviparous oyster from the S.W. Atlantic coasts. This species is not being commercially exploited at present. Because of its high food qualities, however, it may constitute a resource of economic interest in the future.Until now larval development and characteristics of the incubation period have been poorly known. This study describes the characteristics of the mode of brooding under laboratory rearing conditions and, using scanning electron microscopy, the morphogenesis of the hinge until larval release from the parents.The larva develops two anterior and two posterior denticles during brooding. A comparison with larvae of other species of the genus Ostrea reveals that the main differences among them do not lie so much in the pattern of hinge dentition as in the rate of evolution of the hinge components, which is faster in Ostrea puelchana. This species has fully developed denticles at the time of release, which places the larva of this oyster as particularly evolved within the genus Ostrea.

Proportional changes in caries patterns from early to late primary dentition.

A tooth-oriented caries measure has limitations in depicting the caries experience in the primary dentition for a population. Caries patterns based on the child have been presented previously and quantified. The purpose of this study was to explore proportional changes in caries patterns of the primary dentition in two populations. Graphic representation is suggested in developing a model. Children two to five years of age were examined in a city pediatric dental clinic and in a suburban private practice and were categorized as caries-free or as having one of the following etiology-oriented caries experiences associated with lesion sites: Fissures, Hypoplasia, Facial-Lingual, Molar-Approximal, or Facial Lingual/Molar-Approximal. Over 85 percent of children aged 2.5 years or younger were either caries-free or fit the Facial-Lingual category consistent with descriptions of "nursing caries." Trends explored in this study would not be evident using an average for a tooth-oriented caries measure.

Diagnostic Value of Morone Dentition

Abstract Widespread introductions of Morone species and hybrids have led to occasional difficulties in their identification. As the number of Morone morphotypes in individual water bodies continues to expand, or if introgression occurs, there will be an increasing need for diagnostic tools such as the dentition patterns described here. Two sets of specialized teeth are found in the soft tissue at the margins of the tongue–elongate tooth plates lateral to the basihyal and scattered teeth or tooth patches near the tip of the tongue. Variations among six species in these tooth formations, incorporated into a dental key, provide additional discriminatory information to supplement the oft-cited differences in dentition at the rear of the tongue. The presence of a single basihyal tooth patch as diagnostic for white bass Morone chrysops is not reliable as usually claimed because nearly all juvenile and many adult specimens examined bore two basihyal tooth patches. White perch Morone americana and yellow bass M. ...