上颌正中孤立中切牙综合征1例报告

上颌正中孤立中切牙(solitary median maxillary central incisor, SMMCI)是一种比较罕见的牙畸形, 是指在上颌牙弓中仅发育并萌出1颗中切牙且该中切牙位于牙弓的正中, 形态左右对称, 大小与正常中切牙相似, 在乳、恒牙列均可见。SMMCI可单独发生, 也可伴发其他先天性中线结构畸形, 或与一些系统性疾病同时发生。其中, 与前脑无裂畸形(holoprosencephaly, HPE)关系最为密切。本文报告1例伴有其他中线结构缺陷的上颌正中孤立中切牙病例。并对相关问题进行讨论。     

Beware the solitary maxillary median central incisor

The incidence of a solitary maxillary median central incisor (SMMCI) tooth in the general population is low, in either the primary or secondary dentition. The most common cause of a missing maxillary central incisor is trauma, or more rarely hypodontia. However, SMMCI is also a recognized genetic anomaly and affected individuals can be carriers for a potentially more serious condition affecting midline development of the brain and face, holoprosencephaly (HPE). The presence of an SMMCI of unknown aetiology is therefore considered a risk factor for HPE, even in the absence of any other clinical signs. The orthodontist may be responsible for diagnosing cases of SMMCI with no obvious cause, and in these subjects due consideration should be given to referral for the appropriate genetic testing and counselling.     

Commentaries on scientific papers published in this issue

Abstract

The incidence of a solitary maxillary median central incisor (SMMCI) tooth in the general population is low, in either the primary or secondary dentition. The most common cause of a missing maxillary central incisor is trauma, or more rarely hypodontia. However, SMMCI is also a recognized genetic anomaly and affected individuals can be carriers for a potentially more serious condition affecting midline development of the brain and face, holoprosencephaly (HPE). The presence of an SMMCI of unknown aetiology is therefore considered a risk factor for HPE, even in the absence of any other clinical signs. The orthodontist may be responsible for diagnosing cases of SMMCI with no obvious cause, and in these subjects due consideration should be given to referral for the appropriate genetic testing and counselling.     

Solitary median maxillary central incisor and normal stature: a report of three cases

Solitary median maxillary central incisor (SMMCI) is a rare finding. Growth deficiency or other systemic abnormalities may or may not be seen in children with this anomaly. Nevertheless, the growth and development of all children with SMMCI should be closely monitored. This article reports the dental findings of three Chinese girls with SMMCI, but no growth deficiency or other systemic involvement.     

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 median maxillary central incisor in association with hemifacial microsomia: A rare case report and review of literature

Solitary median maxillary central incisor (SMMCI) is a rare dental anomaly. It is estimated to occur in 1:50,000 live births. The SMMCI tooth differs from the normal central incisor in that the crown form is symmetric and it develops and erupts precisely in the midline of the maxillary dental arch in both primary and permanent dentitions. Presence of SMMCI with hemifacial microsomia (HFM) is a very rare clinical condition. We report a case of HFM in a male of Indian origin who presented with SMMCI in both primary and permanent dentitions. The association of HFM with SMMCI may be due to defective development of neural crest cells and/or lack of space in maxilla.     

Osteogenic distraction to treat solitary median maxillary central incisor (SMMCI) syndrome: a case report

Solitary median maxillary central incisor (SMMCI) syndrome is a rare developmental disorder characterized by a single symmetrical maxillary central incisor. Only a small number of cases with comprehensive dental treatment have been reported in the literature. No surgical treatment has been proposed before. We report the case of an 8-year-old girl who presented SMMCI syndrome associated with an Angle class II occlusion and a maxillary transverse deficiency. After the failure of two rapid maxillary expansions, a surgical option was proposed: osteogenic maxillary distraction. The distraction, associated with multi-bracketed fixed orthodontic treatment, created enough space to place a prosthetic central incisor without dental extractions. Osteogenic distraction is an interesting option to treat patients with SMMCI.     

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.     

The neurocranial and craniofacial morphology in children with solitary median maxillary central incisor (SMMCI)

OBJECTIVES: The purpose of this study was to describe the neurocranial and craniofacial morphology on profile radiographs of children with single median maxillary central incisor (SMMCI). DESIGN: Cephalometric analyses of neurocranium and craniofacial morphology on profile radiographs. SETTING AND SAMPLE POPULATION: Department of Orthodontics, School of Dentistry, University of Copenhagen. Thirteen children with SMMCI, 12 girls and one boy (7-17 years of age). OUTCOME MEASURE: Cephalometric measurement were compared with normal standards using a paired t-test and Wilcoxon signed rank test. RESULTS: The size of the neurocranium (especially the length of the anterior cranial base), the maxillary prognathia, the maxillary inclination, the mandibular prognathia and the inclination of the mandibular incisors are significantly reduced in SMMCI. The mandibular inclination, the vertical jaw relationship, the alveolar bone prognathia in the upper jaw and the mandibular angle are significantly enlarged in SMMCI. CONCLUSION: The present study showed that occurrence of SMMCI is a sign of a developmental anomaly associated with deviations in neurocranial size and shape and in craniofacial morphology.     

A new technique for symmetry determination in tooth morphology using image analysis: application in the diagnosis of solitary maxillary median central incisor

OBJECTIVE: To develop a new technique for determining symmetry in tooth morphology and to evaluate this in the investigation of a patient with a solitary maxillary median central incisor (SMMCI) and a control group. DESIGN: A 9-year-old Caucasian female presented with SMMCI. Clinically the tooth appeared symmetrical. Morphology measurements of the maxillary central incisor were made using an image analysis system. Symmetry was determined by outlining the tooth from labial and axial views. These images were block filled, duplicated, flipped horizontally and then superimposed on the original image. The coincident area and perimeter of the two images from both views were measured. The method was repeated for the maxillary central incisors of 20 sets of control study models for young adult patients from which reference intervals for comparison with the SMMCI case were prepared. RESULTS: From the labial view, the area and perimeter of the two images of the SMMCI tooth were 98.85% and 98.97% coincident, respectively. From the axial view the area of the two images was 96.17% coincident, while the perimeter was 99.03% coincident. In all but one comparison for coincidence the SMMCI was above the upper limit of the reference range from the control group. CONCLUSIONS: This new technique is a valid method of assessing symmetry and is a useful clinical tool in cases of SMMCI.     

Face, palate, and craniofacial morphology in patients with a solitary median maxillary central incisor

The occurrence of a solitary median maxillary central incisor (SMMCI) is a very rare condition and might be a sign of a mild degree of holoprosencephaly. In this investigation, material from 10 patients, nine girls and one boy with a SMMCI (8-17 years of age) registered in orthodontic clinics was examined. The purpose was to evaluate the clinical characteristics and craniofacial morphology in this group of patients. Oral photographs, study casts, profile radiographs, and orthopantomograms were analysed. The study showed that this group of SMMCI patients were characterized by an indistinct philtrum, an arch-shaped upper lip, absence of the fraenulum of the upper lip, a complete or incomplete mid-palatal ridge, a SMMCI, and nasal obstruction or septum deviation. The craniofacial morphology of the nine girls, compared with normal standards for girls showed a short anterior cranial base, a short, retrognathic and posteriorly inclined maxilla, and a retrognathic and posteriorly inclined mandible. Furthermore, the sella turcica had a deviant morphology in five of the 10 subjects. The results indicate that the presence of a SMMCI should not be considered as a simple dental anomaly, since it may be associated with other clinical characteristics and more complex craniofacial malformations. It is therefore suggested that the SMMCI condition in future studies is classified according to clinical symptoms and craniofacial morphology.     

Solitary median maxillary central incisor in association with Goldenhar's syndrome: a case report

Goldenhar's syndrome is a rare disorder characterized by several anomalies that include dermal epibulbar cysts, auricular appendices and malformations and vertebral anomalies. In this article, the authors report a case of Goldenhar's syndrome in a 10-year-old child who presented with the classical signs of this condition and a solitary median maxillary central incisor (SMMCI).     

Solitary median maxillary central incisor syndrome and holoprosencephaly: a case report

Solitary median maxillary central incisor syndrome (SMMCIS) is a rare anomaly that affects 1 in 50,000 live births. Of unknown etiology, SMMCIS is characterized by the presence of a single central incisor located on the maxillary midline and may be associated with developmental defects and systemic alterations. SMMCIS also is associated with short stature, mild forms of deviation in craniofacial morphology, and intellectual disability. The purposes of this paper were to: describe the clinical case of an 8-year-old boy with a permanent central incisor located at the midline in association with holoprosencephaly; and highlight the most important aspects related to diagnosis and treatment of solitary median maxillary central incisor syndrome.     

A solitary maxillary central incisor treated orthodontically: a case report

The presentation of a solitary maxillary central incisor is reported and its association with other congenital abnormalities discussed. It is an important finding for dental health professionals, since it may indicate the presence of other significant midline congenital abnormalities. It may also indicate the presence of associated disorders that profoundly affect growth and development and which, once identified, may be treated     

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.     

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.     

Talon cusp associated with other dental anomalies: a case report

Talon cusp is an uncommon dental anomaly referring to an accessory cusp projecting from the cingulum area, or cemento-enamel junction of maxillary or mandibular anterior teeth, in both the primary and permanent dentition. This paper reports a rare case of talon cusp affecting the mandibular right central incisor and maxillary right lateral incisor, together with other dental abnormalities, viz. an inverted impacted migrating mandibular right second premolar; complete agenesis of the maxillary and mandibular third molars, the maxillary right second permanent molar, and the mandibular left permanent central incisor; severe crowding; deep bite; hypoplastic teeth; bilateral reverse cross-bite in the premolar region; and a retrognathic mandible. The presence of this number of dental anomalies in a single patient is rare.     

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.     

Solitary median maxillary central incisor syndrome occurring together with oromandibular-limb hypogenesis syndrome type 1: a case report of this previously unreported combination of syndromes

Background.  Solitary median maxillary central incisor syndrome is a unique developmental abnormality, involving the central incisor tooth germs, occurring with and without systemic involvement. This syndrome has been recorded in association with many other midline developmental anomalies and several known syndromes. Its presence, together with oromandibular-limb hypogenesis syndrome type 1, has not previously been reported.
Case report.  A 3-year-old girl was presented with early childhood caries and a solitary median maxillary central incisor. She had a median submucosal cleft palate and severe micrognathia with hypoglossia. In addition, she had short stature, eating difficulty, and hearing and speech problems. Comprehensive dental treatment for severe early childhood caries was accomplished with a 3-month follow-up appointment to monitor the oral health. The multidisciplinary consultation important for further management has been established.
Conclusion.  The results suggested that when a solitary median maxillary incisor tooth presents, a paediatrician and a geneticist should be asked to carefully examine the patient for other craniofacial malformations and especially midline systemic problems.     

Determination of approximate size of maxillary anterior denture teeth when mandibular anterior teeth are present. Part III: Relationship of maxillary to mandibular central incisor widths

The average width of a natural maxillary central incisor is 8.92 mm. This value is determined from the results of three studies of natural dentitions. The average width of a mandibular central incisor is 5.5 mm. The average ratio produced by dividing the average maxillary central incisor width by the average mandibular incisor width is 1.62. The factor of 1.5 times the width of a mandibular central incisor produces a maxillary central incisor width that is too narrow. The width of a mandibular central incisor plus half the width of the mandibular lateral incisor also produces a maxillary central incisor width that is too narrow. There may be a tendency to undersize the maxillary prosthetic dentition. The ratio of 1.62 can be used to select the appropriate width for a missing maxillary central incisor when given the width of the mandibular central incisor. This ratio of 1.62 is also valuable to verify the dimension of a selected artificial maxillary central incisor when the patient complains that the tooth is too large. If substitutions or adjustments are made in the mold, the desired canine-to-canine measurement produced by the ratio range of 1.3 to 1.38 reported in Parts I and II of this study should be maintained.