Single Maxillary Central Incisor Research Articles

Anatomical Consideration of the Congenital Nasal Pyriform Aperture Stenosis: Localized Dysostosis Without Interorbital Hypoplasia

Congenital nasal pyriform aperture stenosis may be isolated or associated with other midline anomalies. The aim of the study was to describe the measurements and features of the interorbital structure and midface in congenital nasal pyriform aperture stenosis. The computed tomography scans of eight patients (two girls and six boys) were retrospectively reviewed. Several distances were obtained at the orbital and midface levels and compared with normative data. The average width of the pyriform aperture was 5.5 mm +/- 1.6, and there was overgrowth of the pyriform aperture rim (nasal process of the maxilla). No skeletal anomalies were present other than the congenital nasal pyriform aperture stenosis. It was associated with a single median maxillary central incisor in two cases. The anterior and lateral interorbital distances were normal (17.4 mm and 65.4 mm, respectively). The midface was not hypoplastic. There was no brain malformation. Congenital nasal pyriform aperture stenosis is a localized dysostosis of the pyriform aperture rim without interorbital or midface hypoplasia. It may be associated with a single median maxillary central incisor but cannot be viewed as a minor form of holoprosencephaly.

Inner canthal distance and geometric progression as a predictor of maxillary central incisor width

Statement of Problem. Estimating the mesiodistal width of maxillary central incisors may be difficult when artificial teeth are selected for edentulous subjects. Purpose. This study examined the relationship between inner canthal distance and maxillary central incisor mesiodistal width in terms of the geometric progression popularly known as the golden proportion. Material and Methods. Two hundred twenty-nine dentate Saudi subjects (120 males, 109 females; mean age 21.46 years) free from facial and dental deformities were examined. The mesiodistal width of each maxillary central incisor was measured between its interproximal contact points. The inner canthal distance was measured from medial angle to medial angle of the palpebral fissures of the eyes. The common ratios of geometric progression are 0.618 and 1.618. The inner canthal distance of each subject was multiplied by a decreasing function value of the geometric progression term (0.618) to provide the combined width of 2 central incisors. The product was then divided by 2 to obtain the width of a single maxillary central incisor. A t test was used to identify any significant differences in mesiodistal tooth width and inner canthal distance by gender. Agreement between the measured and calculated central incisor widths was evaluated with Pearson's correlation coefficients, as was intraexaminer reliability. Significance was set at α=.05. Results. The mean inner canthal distance of male and female subjects was 28.7 ± 1.7 mm and 27.9 ± 2.1 mm, respectively. The mean maxillary central incisor width of male and female subjects was 8.87 ± 0.5 mm and 8.68 mm ± 0.4 mm, respectively. Differences between the mean values for both measurements were significant (P =.002). The actual and calculated widths of the natural maxillary central incisors were found to be highly correlated (r =.943). Conclusion. Within the population tested, a significantly higher mean inner canthal distance and maxillary central incisor width were recorded for male subjects. Inner canthal distance, when multiplied by a decreasing function value of the geometric progression term and then divided by 2, was a reliable predictor of maxillary central incisor width. (J Prosthet Dent 2002;88:16-20.)

Midline Skeletodental Morphology in Holoprosencephaly

Abstract Objective: The purpose of the present study was to analyze histologically the midline structures in a human fetus with holoprosencephaly and a single median maxillary central incisor. Methods: A human male fetus, CRL 137 mm, postconceptional age 18 weeks, with a diagnosis of holoprosencephaly, the cebocephalic type (one nostril), and alobar brain development, was investigated. After radiography, the cranial midline structures were examined histologically. Results: The histological examination revealed partial absence of the intermaxillary suture (in the region anterior to the central incisor), absence of the internasal suture, and partial absence of the metopic suture (caudal part). A single midline nasal bone was observed instead of two bilateral nasal bones, and a midline maxillary central incisor was found instead of two bilateral incisors. A short nasal septum, absence of crista galli, and partial absence of cartilaginous tissue anterior to the sella turcica in the region of the presphenoid b...

Eruption of the central incisor, the intermaxillary suture, and maxillary growth in patients with a single median maxillary central incisor

The occurrence of a single median maxillary central incisor (SMMCI) is a very rare condition and might be a sign of a more severe midline defect, which could be a mild degree of holoprosencephaly. Absence of the internasal and partial absence of the intermaxillary suture has been observed in a fetus with holoprosencephaly. The purpose of this study was to evaluate the intermaxillary suture, the eruption pattern of the single central incisor in the SMMCI condition, and the growth of the maxilla in a group of patients with SMMCI. A similar study was not found in the scientific literature. The material included orthopantomographs, dental radiographs, and lateral cephalometric radiographs from 11 patients with an SMMCI. The orthopantomographs and dental radiographs showed that the intermaxillary suture was abnormal anterior to the incisive foramen; however, the SMMCI erupted within the expected time interval. Superimposition on stable structures on lateral cephalometric radiographs from two untreated patients, in which growth analysis was possible, showed that the horizontal and vertical growth of the maxilla was normal. Due to the sutural midline defect it is suggested that a transversal growth analysis is included in all treatment planning of SMMCI patients.

Solitary maxillary central incisor in the midline associated with systemic disorders

A single maxillary central incisor in the midline is a rare developmental anomaly. The appearance of a single incisor in place of two teeth may occur as an isolated dental finding that can be related to fusion of two neighboring teeth or to agenesis of a tooth germ. However, the condition has also been reported to occur in association with autosomal dominant holoprosencephaly, growth retardation, and midline developmental defects. This article reports on other systemic defects that can be found in association with a single maxillary central incisor.

Mutations in the human Sonic Hedgehog gene cause holoprosencephaly.

Holoprosencephaly (HPE) is a common developmental defect of the forebrain and frequently the midface in humans, with both genetic and environmental causes. HPE has a prevalence of 1:250 during embryogenesis and 1:16,000 newborn infants, and involves incomplete development and septation of midline structures in the central nervous system (CNS) with a broad spectrum of clinical severity. Alobar HPE, the most severe form which is usually incompatible with postnatal life, involves complete failure of division of the forebrain into right and left hemispheres and is characteristically associated with facial anomalies including cyclopia, a primitive nasal structure (proboscis) and/or midfacial clefting. At the mild end of the spectrum, findings may include microcephaly, mild hypotelorism, single maxillary central incisor and other defects (Fig. 1). This phenotypic variability also occurs between affected members of the same family. The molecular basis underlying HPE is not known, although teratogens, non-random chromosomal anomalies and familial forms with autosomal dominant and recessive inheritance have been described. HPE3 on chromosome 7q36 is one of at least four different loci implicated in HPE. Here, we report the identification of human Sonic Hedgehog (SHH) as HPE3-the first known gene to cause HPE. Analyzing 30 autosomal dominant HPE (ADHPE) families, we found five families that segregate different heterozygous SHH mutations. Two of these mutations predict premature termination of the SHH protein, whereas the others alter highly conserved residues in the vicinity of the alpha-helix-1 motif or signal cleavage site.

Single maxillary central incisor in a girl with del(18p) syndrome.

We present a girl with del(18p) syndrome and a single maxillary central incisor; she is only the second patient in whom this association has been reported.

Two unrelated cases of single maxillary central incisor with 7q terminal deletion

Two unrelated cases of single maxillary central incisor (SM-CI) with 7q terminal deletion of the same breakpoint at 7q36.1 were described. They had mental retardation, microcephaly, hypotelorism, short stature, and normal levels of plasma growth hormone. One case had bilateral caudal ectopic kidneys, double renal pelves, and dilated ureters. The other had bilateral hydroureteronephrosis. The present cases suggest that 7q terminal deletion is one of the causes of SMCI.

Single maxillary central incisor in association with mid-line anomalies

A single maxillary central incisor may occur as an isolated dental finding. However, it has also been reported to occur in association with autosomal dominant holoprosencephaly, in association with growth retardation with or without growth hormone deficiency and occasionally in association with other mid-line developmental defects. Holoprosencephaly and pituitary dysfunction are two specific examples of mid-line defects and this report emphasises that other mid-line defects may be associated with a single maxillary central incisor. We recommend that patients with this dental anomaly should be referred for a detailed medical examination.

Solitary maxillary central incisor and normal stature

Two children, one boy and one girl, each with solitary maxillary deciduous and permanent central incisors, normal height, and normal plasma growth hormone levels, are reported. Review of the literature reveals fourteen reports of patients with a similar dental anomaly. Of these, three are normal in height. The height and growth rate of patients with a single maxillary central incisor should be evaluated prior to growth hormone evaluation; such investigation should be undertaken only if the height is two standard deviations below the mean or if there is evidence of plateauing of linear growth.

Solitary maxillary central incisor and short stature

Seven patients, three males and four females, each with a single (unpaired) deciduous and permanent maxillary central incisor, were studied. All the males and two the female children were growth hormone deficient. One adult woman and a female infant with a single maxillary central incisor were short in stature but had normal growth hormone responses. No other dental anomalies or pituitary-hypothalamic dysfunctions were found. The dental anomaly was not familial. No eye abnormalitis were present in the patients or their families.