Hong-Keun Hyun

Clinical Characteristics and Complications Associated With Mesiodentes

PURPOSE The purpose of the present study was to analyze the clinical characteristics and complications of patients with mesiodens. PATIENTS AND METHODS Using the radiographic reviews of patients who visited Seoul National University Dental Hospital from January 2005 through January 2008, 919 patients were identified as having mesiodens (total 1,200 mesiodentes). The number, location, position, eruption status, shape, direction, and complications of the mesiodens and gender and age were collected and analyzed. RESULTS The mean patient age was 11.05 years (median 7.58) with a male/female ratio of 2.74:1. The results showed that 71.38% of the patients had 1 mesiodens, 27.75% had 2, 0.65% had 3, and 0.22% had 4 mesiodentes. Complications occurred in 46.92% of the mesiodentes. Of the complications, midline diastema was observed in 35.34%, delayed eruption in 20.60%, displacement in 16.60%, rotation in 11.02%, root resorption of adjacent teeth in 7.58%, cystic changes or cyst formation in 5.29%, and nasal eruption in 3.58%. CONCLUSIONS Complications were found in approximately one half of the patients with a mesiodens. Early detection and timely surgical intervention should be emphasized to prevent unwanted complications.

Recurrent keratocystic odontogenic tumor in the mandible: a case report and literature review.

Keratocystic odontogenic tumor is characterized by benign intraosseous neoplasm of odontogenic origin with high recurrence rates. Conservative or aggressive management has been suggested a method of treatment. Conservative approaches have some advantages in that they avoid adverse effects on the development of involved teeth and the jaw when the patient is young, although aggressive methods, including surgical resection, can be recommended considering the nature of the neoplasm. Here we report a case of a 7-year-old patient with a recurrent keratocystic odontogenic tumor treated by marsupialization for normal development of the involved teeth.

Nonsyndromic Multiple Mandibular Supernumerary Premolars

PURPOSE The purpose of this study was to estimate the frequency of and describe the clinical characteristics and complications of patients with nonsyndromic multiple mandibular supernumerary premolars. PATIENTS AND METHODS Among 110,500 patients seen between July 2003 and January 2007, 32 cases of multiple (2 or more) mandibular supernumerary premolars were found. Data including age, gender, number, distribution, and location of supernumerary premolars, extraction procedure, and related complications (such as cystic changes, root resorption, or adjacent teeth eruption disturbance) were collected. RESULTS Six of 32 patients were female; the male to female ratio was 4.3:1. Prevalence of non-syndromic multiple mandibular supernumerary premolars was 0.029%. Mean age was 17.8 years. Root resorption of an adjacent tooth was found in 1 patient. Eruption anomalies were found in 5 patients and included impaction of a permanent tooth, prolonged retention of a deciduous tooth, and displacement of an adjacent tooth. Supernumerary teeth locations were predominantly lingual except for 4 teeth. CONCLUSION Prevalence found in this study was lower compared with previous studies. However, the rate of related complications was higher, even though the mean age was relatively low. Surgical intervention should be considered to prevent unwanted sequelae for any signs of complication.

The position of maxillary canine impactions and the influenced factors to adjacent root resorption in the Korean population

The purpose of this study was to evaluate the position and aspects of maxillary canine impactions in the Korean population and investigate its comparison with the previous reports, while aiding in the establishment of diagnosis and treatment planning by revealing the influential factors of root resorption associated with such impactions. The subjects of this study consisted of 186 teeth from 148 patients, who had visited Seoul National University Dental Hospital due to impacted canines and had taken computerized tomographic images and panorama radiographic images. As a result, maxillary canine impaction in the Korean population occurred 1.5 times more often in females (F:M = 89:59) than males. Regarding the position of impaction, there were three times more buccal impactions (B:P = 140:46) than palatal impactions. The occurrence of root resorption was as high as 49.5 per cent. In evaluating the influential factors affecting adjacent root resorption, the significance of the impacted angulation was insufficient (P = 0.652). However, the buccopalatal position (P < 0.0001) and mesiodistal placement (P = 0.006, 0.037) of the impacted tooth were determined to be significant factors. Therefore, the adjacent root resorption caused by impacted maxillary canines can be stated to exhibit a greater amount of resorption as the positional proximity of the canine crown and lateral incisor root increases.

Identification of a novel FAM83H mutation and microhardness of an affected molar in autosomal dominant hypocalcified amelogenesis imperfecta

AIM To determine the underlying molecular genetic aetiology of a family with the hypocalcified form of amelogenesis imperfecta and to investigate the hardness of the enamel and dentine of a known FAM83H mutation. METHODOLOGY Mutational screening of the FAM83H on the basis of candidate gene approach was performed. All exons and exon-intron boundaries was amplified and sequenced. A microhardness test was performed to measure the Vickers microhardness value. RESULTS A novel nonsense mutation (c.1354C>T, p.Q452X) was identified in the last exon of FAM83H, which resulted in soft, uncalcified enamel. The affected enamel was extremely soft (about 17% of the normal control), but the underlying dentine was as hard as the normal control. CONCLUSIONS Mutational analysis revealed a novel mutation in FAM83H gene. Hardness of dentine was not affected by the mutation, whilst the enamel was extremely soft.

Alteration of Conserved Alternative Splicing in AMELX Causes Enamel Defects

Tooth enamel is the most highly mineralized tissue in vertebrates. Enamel crystal formation and elongation should be well controlled to achieve an exceptional hardness and a compact microstructure. Enamel matrix calcification occurs with several matrix proteins, such as amelogenin, enamelin, and ameloblastin. Among them, amelogenin is the most abundant enamel matrix protein, and multiple isoforms resulting from extensive but well-conserved alternative splicing and postsecretional processing have been identified. In this report, we recruited a family with a unique enamel defect and identified a silent mutation in exon 4 of the AMELX gene. We show that the mutation caused the inclusion of exon 4, which is almost always skipped, in the mRNA transcript. We further show, by generating and characterizing a transgenic animal model, that the alteration of the ratio and quantity of the developmentally conserved alternative splicing repertoire of AMELX caused defects in enamel matrix mineralization.

Recessive Mutations in ACPT, Encoding Testicular Acid Phosphatase, Cause Hypoplastic Amelogenesis Imperfecta

Amelogenesis imperfecta (AI) is a heterogeneous group of genetic disorders affecting tooth enamel. The affected enamel can be hypoplastic and/or hypomineralized. In this study, we identified ACPT (testicular acid phosphatase) biallelic mutations causing non-syndromic, generalized hypoplastic autosomal-recessive amelogenesis imperfecta (AI) in individuals from six apparently unrelated Turkish families. Families 1, 4, and 5 were affected by the homozygous ACPT mutation c.713C>T (p.Ser238Leu), family 2 by the homozygous ACPT mutation c.331C>T (p.Arg111Cys), family 3 by the homozygous ACPT mutation c.226C>T (p.Arg76Cys), and family 6 by the compound heterozygous ACPT mutations c.382G>C (p.Ala128Pro) and 397G>A (p.Glu133Lys). Analysis of the ACPT crystal structure suggests that these mutations damaged the activity of ACPT by altering the sizes and charges of key amino acid side chains, limiting accessibility of the catalytic core, and interfering with homodimerization. Immunohistochemical analysis confirmed localization of ACPT in secretory-stage ameloblasts. The study results provide evidence for the crucial function of ACPT during amelogenesis.

Oligodontia and Curly Hair Occur with Ectodysplasin-A Mutations

Oligodontia is the developmental absence of more than 5 permanent teeth except for the third molar. Familial oligodontia can occur as an isolated form or as part of a genetic syndrome. Mutations in the MSX1, PAX9, AXIN2, EDA, and WNT10A genes have been identified in familial non-syndromic oligodontia. Ectodermal dysplasia is a group of syndromes involving abnormalities of the ectodermal structures and is comprised of more than 150 different forms. Mutations in the ectodysplasin-A (EDA) gene have been associated with X-linked hypohidrotic ectodermal dysplasia, and partial disruption of the EDA signaling pathway has been shown to cause an isolated form of oligodontia. We identified 2 X-linked oligodontia families and performed mutational analysis of the EDA gene. The mutational analysis revealed 2 novel EDA mutations: c.866G>T, p.Arg289Leu and c.1135T>G, p.Phe379Val (reference sequence NM_001399.4). These mutations were perfectly segregated with oligodontia and curly hair within each family and were not found in the 150 control X-chromosomes with the same ethnic background and in the exome variant server. This study broadens the mutational spectrum of the EDA gene and the understanding of X-linked oligodontia with curly hair.

A nanoscale ridge/groove pattern arrayed surface enhances adipogenic differentiation of human supernumerary tooth-derived dental pulp stem cells in vitro

OBJECTIVE The aim of this study was to establish human dental pulp stem cells (hDPSCs) from supernumerary teeth and determine the effects of a 350-nm nano-patterned surface on adipogenic and osteogenic differentiation of hDPSCs. DESIGN Several surface markers were analysed by FACS to confirm the isolated cells as hDPSCs. To demonstrate the effects of a nano-patterned surface on the differentiation of hDPSCs, the cells were cultured on a nano-patterned surface with or without adipogenic or osteogenic induction factors. Cells were then stained with Oil red O or Alizarin red, and the lineage specific genes LPL and Runx-2 were analysed by real-time PCR at 3, 6 and 9 days after culture. RESULTS The hDPSCs on a nano-patterned surface showed a linear arrangement compared to irregular cells on a conventional surface. During adipogenic differentiation, more Oil red O stained cells were found in the nano-patterned group than in the conventional group. On the other hand, there was no significant difference in Alizarin red staining between the nano-pattern and conventional surface groups after induction of osteogenic differentiation. Gene expression analyses revealed significantly higher expression of LPL in the nano-patterned group than in the conventional group, whereas Runx-2 expression was higher in the conventional group than in the nano-patterned group. CONCLUSION This study showed that a nano-patterned surface may be able to enhance adipogenic differentiation of hDPSCs by altering their morphology and gene expression patterns, whereas the same surface may inhibit or suppress osteogenic differentiation of the cells.

Deep sedation with sevoflurane inhalation via a nasal hood for brief dental procedures in pediatric patients.

Nitrous oxide is widely used for dental sedation. However, weak potency of nitrous oxide requires additional sedatives for maintaining a deeper level of sedation. Sevoflurane, a mainstay in pediatric anesthesia, is a potent anesthetic agent. Some attempts have been made to use sevoflurane for conscious sedation. In this case, we successfully treat pediatric patients under deep sedation by sevoflurane inhalation without other sedatives. Sevoflurane may be useful for sedation in pediatric dental outpatient setting.