[Supernumerary and atypically formed vestibular element in the upper jaw].
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BACKGROUND: Talon cusp is a supernumerary structure projecting from the dento-enamel junction to a variable distance towards the incisal edge of an anterior tooth. Studies have shown that it consists of enamel, dentine and a variable amount of pulp tissue. Hyperactivity of the enamel organ during morphodifferentiation has been attributed to its formation. Most previous reports have been made concerning the occurrence of this structure on primary and permanent teeth and mostly on the palatal aspect. Only few have been reported on the facial aspect of the teeth. When it occurs, the effects are mainly aesthetic and functional and so early detection and treatment is essential in its management to avoid complications. CASE PRESENTATION: An unusual case of talon cusp on the facial aspect of a mandibular central incisor is reported. Its presence resulted in attrition of the opposing tooth. Reduction of the cusp and topical application of fluoride gel was initiated. CONCLUSION: The management and treatment outcome of talon cusp depends on the size, presenting complications and patient cooperation.
The term retarded eruption, may be used in cases where eruption is inhibited, causing an interruption in the coordination of tooth formation and tooth eruption. The phenomenon may be local or general, and several etiological factors for retarded eruption have been listed, comprising a lack of space, ankylosis, cysts, supernumerary teeth, hormone and vitamin deficiencies and several developmental disturbances and syndromes. The present paper describes several cases of retarded eruption where no factors other than inheritance have been evident. So far 14 cases have been evaluated, 9 boys and 5 girls. In addition several cases have been registered among parents and grandparents of the probands. Typical features are: retarded eruption, defined as more than 3 SD beyond mean eruption figures, comprises all teeth in the permanent dentition, and in 5 cases also second primary molars. The chronology of tooth formation are within normal limits. Consequently the teeth finish development still laying deeply buried in the jaws, often in aberrant positions and with curves or hooks on the roots. When the teeth finally get the "signal" for eruption, 5-15 years beyond normal eruption time, they move rather quickly into right positions, despite the long eruption paths and the hooked roots. Permanent teeth without, as well as with predecessors, are affected. Extraction of predecessors does not seem to provoke eruption. The main features in management are to take care of the primary teeth, to improve-esthetics, and offer surgery and orthodontics when needed. Analyses of pedigrees indicates that the genetic transmittance may be autosomal dominant as both sexes are affected, about half of the siblings show the trait, and the trait shows continuity through generations.
Oral findings on the panoramic tomograms of fifty-two patients with adenomatosis coli (AC) are presented. Osteomatous lesions, embedded teeth, and supernumerary teeth were found more frequently in AC patients than in a normal population. The osteomatous lesions were found in more than 80 percent of the AC patients, and the average number of such lesions per patient was 4.7. In a normal population, 15 percent had the osteomatous lesions, and the average number per patient was 1.1. The panoramic tomograms of twelve AC patients who had more than six osteomatous lesions showed very characteristic images. The possibility of early detection of AC through oral radiographic findings is suggested.
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Osteoblasts and odontoblasts, cells that are responsible for the formation of bone and dentin matrices respectively, share several molecular characteristics. Recently, Cbfa1 was shown to be a critical transcriptional regulator of osteoblast differentiation. Mutations in this gene cause cleidocranial dysplasia (CCD), an autosomal dominant disorder in humans and mice characterized by defective bone formation. CCD also results in dental defects that include supernumerary teeth and delayed eruption of permanent dentition. The dental abnormalities in CCD suggest an important role for this molecule in the formation of dentition. Here we describe results of studies aimed at understanding the functions of Cbfa1 in tooth formation. RT-PCR and in situ hybridization analyses show that Cbfa1 has a unique expression pattern in dental mesenchyme from the bud to early bell stages during active epithelial morphogenesis. Unlike that observed in osteoblast differentiation, Cbfa1 is downregulated in fully differentiated odontoblasts and is surprisingly expressed in ectodermally derived ameloblasts during the maturation phase of enamel formation. The role of Cbfa1 in tooth morphogenesis is further illustrated by the misshapen and severely hypoplastic tooth organs in Cbfa1-/- mice. These tooth organs lacked overt odontoblast and ameloblast differentiation and normal dentin and enamel matrices. Epithelial-mesenchymal recombinants demonstrate that dental epithelium regulates mesenchymal Cbfa1 expression during the bud and cap stages and that these effects are mimicked by the FGFs but not by the BMPs as shown by our bead implantation assays. We propose that Cbfa1 regulates the expression of molecules in mesenchyme that act reciprocally on dental epithelium to control its growth and differentiation. Taken together, our data indicate a non-redundant role for Cbfa1 in tooth development that may be distinct from that in bone formation. In odontogenesis, Cbfa1 is not involved in the early signaling networks regulating tooth initiation and early morphogenesis but regulates key epithelial-mesenchymal interactions that control advancing morphogenesis and histodifferentiation of the epithelial enamel organ.
Pax genes have been shown to play important roles in mammalian development and organogenesis. Pax9, a member of this transcription factor family, is expressed in somites, pharyngeal pouches, mesenchyme involved in craniofacial, tooth, and limb development, as well as other sites during mouse embryogenesis. To analyze its function in vivo, we generated Pax9 deficient mice and show that Pax9 is essential for the development of a variety of organs and skeletal elements. Homozygous Pax9-mutant mice die shortly after birth, most likely as a consequence of a cleft secondary palate. They lack a thymus, parathyroid glands, and ultimobranchial bodies, organs which are derived from the pharyngeal pouches. In all limbs, a supernumerary preaxial digit is formed, but the flexor of the hindlimb toes is missing. Furthermore, craniofacial and visceral skeletogenesis is disturbed, and all teeth are absent. In Pax9-deficient embryos tooth development is arrested at the bud stage. At this stage, Pax9 is required for the mesenchymal expression of Bmp4, Msx1, and Lef1, suggesting a role for Pax9 in the establishment of the inductive capacity of the tooth mesenchyme. In summary, our analysis shows that Pax9 is a key regulator during the development of a wide range of organ primordia.
Dental invagination or dens in dente is a rare malformation with a widely varied morphology. Radiographically, the affected tooth shows an infolding of the enamel and dentin that can extend to within the pulp cavity and the root and sometimes to the root apex. It can occur in both primary and permanent teeth, and its prevalence is reported to be 1.7% to 10%. The dental anomalies observed in association with dental invagination include taurodontia, microdontia, supernumerary teeth, gemination, and dentinogenesis imperfecta. This article presents a clinical case in which a radiographic finding could be compatible with the presence of a nasopalatine or globulomaxillary cyst and a dens in dente. It was decided to extract the invaginated tooth, and by 15 days postextraction, the radiolucid area had completely disappeared. The complex surgery that would have been required to remove the patient's supposed cyst was thus avoided. Clinical and radiographic examination is suggested before making further decisions that could complicate treatment when a lesion is associated with other dental anomalies.
Skulls (n=104) of northern elephant seals from California were examined macroscopically. The animals varied in age but the numbers of each sex were roughly equal. The majority (86%) of teeth were available for examination. The mandibular first premolars were the most common teeth to be congenitally absent, with 2.3% missing. Supernumerary teeth (usually a supplemental mandibular molar) were associated with only 1.4% of normal teeth (or empty alveolar sockets). At least one persistent deciduous tooth was present in 38% of skulls, 70% of which were juvenile skulls. The majority (95.8%) of premolars had the type 2a tooth form, with only 3.8% and 0.5% of type 2b and 2c, respectively. Forty-six skulls, of which 43 were from adults, showed signs of attrition. Tooth fractures were uncommon, affecting only 33 teeth (1.2%). One skull showed an "incremental line" suggestive of enamel hypoplasia. Periodontal hard tissue lesions were seen in 44.3% of all teeth present (46.0% of skulls). Six cases of periapical disease with bone loss were observed.
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Six patients with transposed tooth germ before root formation are reported in cases with cleft lip or palate. A boy with complete bilateral cleft lip and palate had a maxillary permanent canine displaced posteriorly in the vomer. A girl with cleft palate had an upwards and distally transmigrated maxillary canine. Two girls with cleft palate had a transposed maxillary canine with the first premolar. One patient had a maxillary second premolar migrated between the first and second permanent molar, and another had the germ of a supernumerary maxillary premolar between the first and second permanent molars. The follow-up findings concerning the development of the teeth and treatment are described; they are also discussed in the light of present theories on the etiology of tooth transposition.
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