Heung-Kyu Son

Incidence and relationship of an additional root in the mandibular first permanent molar and primary molars

OBJECTIVES The mandibular first permanent and primary molars occasionally have an additional root located distolingually. This study aimed to determine the incidences of an additional root in these molars and their relationship. STUDY DESIGN This study involved 4050 children for whom periapical radiographs of the mandibular molar area were available. The incidence of an additional root for each molar was calculated and the pattern of concurrent additional roots in different molars was also investigated. RESULTS Additional roots were present in 33.1%, 27.8%, and 9.7% of the first permanent, second primary, and first primary molars, respectively. When an additional root was present in a primary molar, the probability of the posterior adjacent molar also having an additional root was greater than 94.3%. CONCLUSION The presence of an additional root in a primary molar can be used to predict the presence of an additional root in molars posterior to it.

Growth effects of botulinum toxin type A injected into masseter muscle on a developing rat mandible

OBJECTIVES Botulinum toxin type A (BTX-A) reduces the muscular contractions by temporarily inhibiting the release of acetylcholine at the neuromuscular junction. The purpose of this study was to investigate the effects of the BTX-A injected into the masseter muscle of a developing rat mandible. MATERIALS AND METHODS Four-week-old male (no. 80) Sprague-Dawley rats were divided into four groups: control group, saline group, BTX-A group and baseline control group. Rats of baseline group were sacrificed at 0 day to provide baseline values of the mandibular measurements. The masseter muscle of rats in the saline and the BTX-A group were administered with saline and BTX-A solutions respectively. Experimental animals were sacrificed after 4 weeks. RESULTS The BTX-A group demonstrated smaller mandibular dimension compared with the other groups (P < 0.05). Their condylar cartilages showed increased apoptosis at the proliferation stage of the reserve zone and masseter muscle fibers demonstrated atrophic changes. CONCLUSIONS The result demonstrated BTX-A influence on inhibitory action of the developing mandible because of apoptosis at the proliferation stage of the reserve zone of the condylar cartilage in developing rat mandible.

The Distribution of Patients and Treatment Trends in the Department of Pediatric Dentistry, Yonsei University Dental Hospital for Last 5 Years

The aim of this study was to investigate changes in treatment patterns within pediatric dentistry departments by analyzing the distribution of patients and treatment trends. To that end, treatment charts based on electronic medical records (EMR) from the Yonsei University Dental Hospital from 2008 to 2012 were collected and analyzed. The results showed a decrease in the number of new patients and patients cared for by non-specialists, while the number of foreign patients has increased. The under 2 years-old group accounted for a large portion of new patients. Dental caries, dental trauma, and malocclusion ranked as the top complaints. In terms of restoration treatment, the proportion of patients receiving composite resin, amalgam, and sealant has decreased, whereas self-curing glass ionomer and preventive resin restoration have increased. Single-visit endodontic treatment has been increasing, with a decreasing trend in multi-visit endodontic treatment. The rate of conservative pulp treatment, such as pulp capping and pulpotomy, has increased. For reducing patient anxiety, treatments under sedation have increased, especially with the use of nitric oxide. This investigation into the latest treatment trends and patient characteristics is expected to help pediatric dentists to make appropriate treatment plans.

Expression of Ca2+-dependent Synaptotagmin Isoforms in Mouse and Rat Parotid Acinar Cells

Synaptotagmin is a Ca2+ sensing protein, which triggers a fusion of synaptic vesicles in neuronal transmission. Little is known regarding the expression of Ca2+-dependent synaptotagmin isoforms and their contribution to the release of secretory vesicles in mouse and rat parotid acinar cells. We investigated a type of Ca2+-dependent synaptotagmin and Ca2+ signaling in both rat and mouse parotid acinar cells using RT-PCR, microfluorometry, and amylase assay. Mouse parotid acinar cells exhibited much more sensitive amylase release in response to muscarinic stimulation than did rat parotid acinar cells. However, transient [Ca2+]i increases and Ca2+ influx in response to muscarinic stimulation in both cells were identical, suggesting that the expression or activity of the Ca2+ sensing proteins is different. Seven Ca2+-dependent synaptotagmins, from 1 to 7, were expressed in the mouse parotid acinar cells. However, in the rat parotid acinar cells, only synaptotagmins 1, 3, 4 and 7 were expressed. These results indicate that the expression of Ca2+-dependent synaptotagmins may contribute to the release of secretory vesicles in parotid acinar cells.

Comparative Gene-Expression Analysis of Periodontal Ligament and Dental Pulp in the Human Permanent Teeth

There is no genetic activity information with the functions of dental pulp and periodontal ligament in human. The purpose of this study was to identify the gene-expression profiles of, and the molecular biological differences between periodontal ligament and dental pulp obtained from human permanent teeth. cDNA microarray analysis identified 347 genes with a fourfold or greater difference in expression level between the two tissue types 83 and 264, of which were more plentiful in periodontal ligament and dental pulp, respectively. Periodontal ligament exhibited strong expression of genes related to collagen synthesis (FAP), collagen degradation (MMP3, MMP9, and MMP13), and bone development and remodeling (SSP1, BMP3, ACP5, CTSK, and PTHLH). Pulp exhibited strong expression of genes associated with calcium ions (CALB1, SCIN, and CDH12) and the mineralization and formation of enamel and dentin (SPARC/SPOCK3, PHEX, AMBN, and DSPP). Among these genes, SPP1, SPARC/SPOCK3, AMBN, and DSPP were well known in dental research. However, the other genes are the newly found and it may help to find a good source of regenerative therapy if further study is performed.

Effect of Storage Media and Duration on Pulpal Cell Viability in Exfoliated Deciduous Teeth

Abstract Corresponding author : Prof. Heungkyu Son Department of Pediatric Dentistry, Yonsei University College of Dentistry, 250 Seongsanno, Seodaemun-gu, Seoul 120-752, KoreaTel: +82-2-2228-3172 / Fax: +82-2-392-7420 / E-mail: HGSON@yuhs.ac Received July 3, 2013 / Revised November 14, 2013 / Accepted November 14, 2013 Ⅰ. 서 론흡수탈락된유치의치수조직 1) , 발거된선천치의치수 2) 및유치의치주인대 3) 에서줄기세포를얻을수있다고보고되었다. 탈락된유치에서얻은줄기세포는비침습적으로얻을수있으며,영구치의치수에서얻은줄기세포와비교하였을때더높은증식률, 분화능을보였다는보고 4) 가있었다. 이러한유치의장점때문에최근유치에서얻은조직을간엽성줄기세포의원천으로사용하는연구가활발하게이루어지고있다 1,5-7) .치아를용액에보관하는것에대한연구는영구치의이식이나재식을위한치아주변인대세포의생존 8-12) 과관련된연구가선행되었으며, 유치의경우에는재식이나이식하는경우가없어현재까지탈락유치의보관용액및조건에따른추출세포의생존률이나특성에대한보고는없는상태이다. 그러나유치줄기세포에대한관심이증가하면서치과및집에서발거된유치추출세포의생존률을높이는방법에대한연구가필요하다고판단되고, 가정에서불시에유치가탈락하였을경우주변에서쉽게구할수있는저장용액에유치를임시로보관한후줄기세포를추출할수있다면지금보다더많은유치를줄기세포연구에이용할수있을것이라고예상된다. ※This study was supported by a faculty research grant of Yonsei University College of Dentistry for 2013 (No. 6-2013-0096).�These authors equally contributed to this work.J Korean Acad Pediatr Dent 41(1) 2014ISSN (print) 1226-8496 ISSN (online) 2288-3819http://dx.doi.org/10.5933/JKAPD.2014.41.1.1

The Effects of Hydroxyapatite on Demineralization Resistance and Bonding Strength in Light-Curing Glass Ionomer Dental Cement

he aim of this study was to evaluate the effect of HA on the demineralization resistance and bonding strength of light-curing glass ionomer dental cement. Tests were conducted using (1) pure Fuji II LC GIC, (2) 15% micro HA-Fuji II LC GIC. Physical properties, demineralization resistance and bonding strength to dentin of teeth were determined. The curing depth in all groups were satisfied the requirement of curing depth of ISO 9917-2:2004(minimum curing depth = 1mm). The depth of cure was reduced with addition of HA, presumably due to the light scattering effect of HA particles. Regarding sensitivity to ambient light, there were no detectable changes of the homogeneity in any groups. Also all groups were satisfied the requirement of the flexural strength of ISO 9917-2:2004(minimum flexural strength = 20MPa). 15% HA-Fuji II LC GIC group was found to present a greater flexural strength than pure Fuji II LC GIC, as the addition of HA promotes a chemical reaction between the HA, the glass powder, and the polyacid. Observing under the CLSM after 4 days of demineralization, there were significant differences in the CLSM and SEM images. Pure Fuji II LC GIC group showed greater enamel demineralization layer than in 15% HA-Fuji II LC GIC group. In SEM analysis, there was greater enamel demineralization in the pure Fuji II LC GIC group, and less demineralized under the influence of HA particles, 15% HA-Fuji II LC GIC group had more even surface particles. 15% HA-Fuji II LC GIC group was found to present a greater bonding strength than pure Fuji II LC GIC group. Observing the fractured surfaces under SEM after the bonding strength test, the cohesive failure rate was found to be in increasing order of pure Fuji II LC GIC, 15% HA-Fuji II LC GIC group. There were bone-like apatite particles observed to be formed in 15% HA-Fuji II LC GIC group.

A Comparison of the Bone-Like Apatite Formation Potency Between Hydroxyapatite and β-Tricalcium Phosphate in Glass Ionomer Dental Luting Cement

Previous studies have shown that hydroxyapatite increases the bonding strength of dental luting cement with human teeth by forming bone-like apatite when it is added to cement. However, due to the low solubility of the hydroxyapatite, its ability to form bone-like apatite decreases in protein-free acellular simulated body fluid with ion concentrations nearly equal to those of the human blood plasma. The purpose of this experiment was to increase the formation of bone-like apatite by mixing hydroxyapatite with β-TCP of high solubility. RelyXTM glass ionomer cement(3M/ESPE, USA) was used as dental luting cement. Film thickness, setting time, and compressive strength was measured for each group of 15% hydroxyapatite, 15% β-TCP, and 15% mixed hydroxyapatite and β-TCP (85:15). Every specimen of each group was immersed in the simulated body fluid for four week before measuring bonding strength, and then their sectional surface was observed under SEM. The most noteworthy result was that the group containing β-TCP produced more amount of bone-like apatite compared with the group composed of only hydroxyapatite.

DENTAL MANAGEMENT OF A PATIENT WITH PRADER-WILLI SYNDROME : A CASE REPORT

Prader-Willi syndrome (PWS) is a rare neurodevelopmental disease caused by abnormality of chromosome 15q11-13. The estimated prevalence of PWS is 1/10,000-30,000. Most common features of this disease are feeding problems characterized by poor sucking habit related with neonatal or infantile hypotonia and obesity due to early childhood hyperphagia involved with lack of satiety. In the orodental findings, enamel hypoplasia, rampant caries, delayed eruption, poor oral hygiene, hypodontia, supernumerary teeth, increased tooth wear, decreased salivary flow and change in saliva composition were reported. This case report describes the dental treatment of 3-year-9-months-old male patient with PWS. Periodic check-ups and conservative treatments were followed, however, rapid dental caries progression caused by estimating hyposalivation was observed. Because of lack of patient cooperation, dental procedures were performed under general anesthesia. [J Korean Dis Oral Health Vol.10, No.1: 26-30, June 2014]

ALVEOLAR BONE LOSS AFTER THE EARLY LOSS OF UPPER CENTRAL INCISOR IN GROWING CHILDREN

The anterior maxillary incisor is the most traumatized region in the mouth and trauma is frequent between the ages of 8-10. Traumatic loss of teeth, can lead to many complications in children. Thus, as possible to keep traumatic teeth, but if you need extractions There may be. Complications occur and early tooth loss is frequent. Complications of early loss of central incisors are esthetic compromise, loss of vertical and horizontal width, height, contour of alveolar bone, tilting of adjacent teeth, arch length loss. Alveolar bone loss may affect normal function and stability, and results in esthetic problem for future prosthesis restoration. The 9-year-old girl and 6-year-old boy got early loss of upper central incisor. The amount of alveolar bone resorption was measured using cone beam computed tomograph and cast analysis.