Se-Hyun Hahn

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.

Effect of curing method and curing time on the microhardness and wear of pit and fissure sealants

OBJECTIVE To evaluate the effects of a light source, polymerization time and storage time on the microhardness and wear of pit and fissure sealants. METHODS Five commercial pit and fissure sealants (Fissurit F [FF], Teethmate F1 [TF], Apollo Seal [AS], Concise [CC], and Ultraseal XT Plus [US]) were used. Specimens were cured with a conventional visible light curing unit (Curing Light XL 3000) for 10, 20, 30, 40s or with a plasma arc light curing unit (Apollo 95E) for 3, 6, 9, 12s. The specimens were kept dry in light-shielded bottles at 37 degrees C for 1 week, then half of them were thermocycled. The rest of them were stored in distilled water in light-shielded bottles for another 30 days, which were kept in an incubator at 37 degrees C, followed by thermocycling. Microhardness and wear of the specimens were measured. RESULTS Similar degree of microhardness was achieved with the shorter curing time with the plasma arc light curing unit as with the conventional visible light-curing unit. With conventional visible light curing, the microhardness of the top surface was higher than that of the bottom surface (P<0.05). With plasma arc light curing, the microhardness of the top surface was higher than that of the bottom surface for AS and CC, but for FF, TF and US, the microhardness of the top surface was lower than that of the bottom surface, except in the 3-s curing of US. For FF, AS, CC and US, wear in the 6s curing with plasma arc light was similar to or less than that of the 30s curing with conventional visible light, but for TF, wear of the 9s curing with plasma arc light was similar to that of the 20s curing with conventional visible light. After storage in distilled water for 30 days followed by thermocycling, there was a tendency towards a decrease in microhardness and an increase in wear. There was a significant negative correlation between microhardness and wear (P<0.01). SIGNIFICANCE The tested curing methods differed significantly in their curing capacity. This study suggested that a plasma arc light curing unit needs shorter curing time than a visible light curing unit to achieve similar mechanical properties of the pit and fissure sealants tested.

The AC Loss Measurement of the KSTAR PF1 Coils During the First Commissioning

The AC loss in a large superconducting magnet coil shows a tendency to be changed after assembly. For the ac loss measurement of the Korea Superconducting Tokamak Advanced Research (KSTAR) superconducting coils after assembly, several current scenarios, trapezoidal pulses and a DC offset sinusoidal pulses, were applied to the PF1 Upper (U) and Lower (L) coils during the commissioning. The measurement was done once before and once after the plasma discharge experiments. All coil data were obtained by the tokamak monitoring system and helium distribution system which were designed to measure temperature, pressure, and mass-flow at both inlets and outlets of the coils. The PF1 coils of the cable-in-conduit conductor type were made of Nb3Sn superconducting strands, whose winding scheme is 20 layers with each layer having 9 turns. Each has 10 cooling channels for the heat removal by the supercritical helium at 4.5 K. For the trapezoidal pulse tests, the current was increased up to 4 kA with several different ramp rates and a 2 kA DC offset and 0.5 kA sine waves with different frequencies from 0.1 Hz to 0.3 Hz were applied to the coil. According to the analyses, the AC loss was slightly decreased for the same condition after 700 plasma shots. It was believe that such a result was due to reduced inter-strand resistances which changed the transverse resistance between the inter-strands. The coupling time constant was estimated to be 32 ms in the trapezoidal tests and 13.6 ms for the DC offset sinusoidal pulses. The former is larger than the latter because of the effect of the jacket eddy current loss due to Incoloy 908 which is a ferromagnetic material. Considering the jacket eddy current losses, the coupling time constant was recalculated and the value estimated to be about 13 ms for all current wave forms during first commissioning.

KSTAR Magnetic Field Measurement During the Commissioning and Remanent Field Evaluation

An in situ measurement of the magnetic field generated by the assembled superconducting magnet coils was held by using precision Hall sensors during the commissioning of the Korea Superconducting Tokamak Advanced Research (KSTAR) device. This was done in order to investigate the magnetic influence of Incoloy 908, which is the jacket material for the cable-in-conduit conductors (CICCs) of the Nb3Sn coils. After the PF coils were discharged from 1 kA the vertical remanent field at the plasma center was more than 10 G, while the TF coils were not energized. The vertical magnetic field generated by the PF coils had a discrepancy of up to 50 G between measurement and the calculation assuming no magnetic influence of Incoloy 908. Thus, non-negligible ferromagnetism was identified and attributed to Incoloy 908. In contrast, most of the hysteresis observed in the magnetic measurements was eliminated when the Incoloy 908 of the TF windings was saturated by the TF coil charging.

A STUDY OF NEW-PATIENT DISTRIBUTION AND THE MOTIVES FOR VISITING IN THE DEPARTMENT OF PEDIATRIC DENTISTRY AT SEOUL NATIONAL UNIVERSITY DENTAL HOSPITAL

The number of patients requesting services of pediatric dental clinics has been steadily increasing in South Korea. The pediatric dental clinics are comprised of hospital-based clinics and local clinics. The purpose of this study was to analyze new-patient distribution and to survey the motives for visiting the department of pediatric dentistry at Seoul National University Dental Hospital(SNUDH), utilizing questionnaires for parents from May to July 2010. The results are as follows: 1. Age distribution showed that 0-3 year-olds formed the largest group of 29.3%. The average age of patients was 6.2 years old. 2. In the surveys for the parents, the major reason for visiting SNUDH was the referral from other clinics(30.6%). 3. The 75% of patients previously visited other clinics before visiting SNUDH. 1) The greater number of patients(52%) visited general practitioners clinic than pediatric specialists(48%). 2) More than 90% of the patients visited SNUDH after visiting other clinics for reassuring diagnosis and referrals. 3) The crucial deterring factor of being treated at SNUDH was difficult accessibility.

Qualification Test Results of the KSTAR Superconducting Coils From the Construction to the Commissioning Steps

To achieve the first plasma of the Korea superconducting tokamak advanced research (KSTAR), the KSTAR superconducting coils were tested in advance. As they should operate in excessively low temperature of 4.5 K and high magnetic field environment of 7.5 T, it is crucial to monitor the cryogenic and the structural behaviors of KSTAR device during the commissioning period including a cool-down. The temperatures of the KSTAR toroidal field (TF) coil and the poloidal field (PF) coils were measured during the entire operating period. The mechanical stresses on the TF and PF structures were continuously monitored to check if they go beyond the limiting value calculated through the simulation. The alignment of the KSTAR device was checked by using displacement sensors. The TF coils were successfully supplied with 15 kA DC current for 8 hours, and the maximum 5 kA/s current variation of the PF coils were tested. For the main experiment, the interlock test of the quench detection system for the KSTAR coils was carried out at reduced currents of 1 kA. From these results the quench protection circuit, and the current-flow of the KSTAR superconducting coils proved to be well performed for the first plasma operation.

TREATMENT OF TOOTH DISCOLORATION ASSOCIATED WITH TRIPLE ANTIBIOTIC THERAPY: CASE REPORTS

The concept of revascularization of necrotic pulps regained interest and became an alternative conservative treatment option for young permanent teeth with immature roots. Revascularization of immature teeth with apical periodontitis depends mainly on disinfection of the canal. Since the infection of the root canal system is considered to be polymicrobial, a combination of drugs would be needed to treat the diverse flora. A triple antibiotic mixture of metronidazole, ciprofloxacin, and minocycline was used as an intracanal medicament. However, discoloration was developed after applying the triple antibiotic mixture. It is believed that the marked discoloration is related to the use of minocycline. The aim of this article was to present cases of coronal discoloration after triple antibiotic therapy in immature tooth and was treated with bleaching technique to control coronal discoloration. In conclusion, revascularization by using triple antibiotics promotes a paradigm shift in treating endodontically involved permanent teeth. However, we should understand that triple antibiotics containing minocycline induces tooth discoloration. Further research to prevent coronal discoloration should be investigated and suggested for the safe use of triple antibiotics.

SUPPLEMENTAL PERMANENT MAXILLARY LATERAL INCISORS(DOUBLE LATERAL INCISORS) : CASE REPORT

치배형성기 발육 이상으로 유치열이나 영구치열에서 정상보다 많이 발생하게 된 치아를 과잉치라 한다. 과잉치는 형태에 따라 정상 치아와 형태가 비슷한 보충치(supplementary tooth)와 형태가 다른 흔적치(rudimentary tooth)로 나눌 수 있다. 대부분의 과잉치는 흔적치의 형태를 가지며 보충치는 드물게 나타난다. 보충치는 상악 측절치 부위에서 호발하며 정상 전치와 유사한 형태와 크기를 갖기 때문에 진단시 특별히 주의를 기울여야 한다. 미맹출 과잉치는 상악 전치의 맹출 장애 및 전위, 치간 이개, 치근 흡수, 낭종 형성 등의 합병증을 유발할 수 있으므로 조기에 진단하고 치아 배열 상태 및 치아 발육 단계에 따라 적절한 치료를 시행하는 것이 중요하다. 본 3 증례는 상악 측절치부에 편측 혹은 양측으로 보충치 형태의 과잉치를 갖는 증례로서 맹출 관찰 및 외과적 발거, 교정 치료 및 레진 수복을 통해 치료하였다. 【Supernumerary teeth are in excess of the normal number of teeth in either the primary or permanent dentitions. They are classified into supplemental teeth resembling those of the normal series and rudimentary teeth with abnormal shapes, according to their form. Most of the supernumerary teeth are rudimentary form, and supplemental teeth are much less common. Sulppemental teeth are most common in the permanent maxillary lateral incisor area and clinicians should be careful with differential diagnosis from normal teeth. Unerupted supernumerary teeth may produce several complications such as delayed eruption, displacement of permanent teeth, diastema, root resorption and cyst formation. Early detection and proper treatment plan according to the tooth alignment and root formation stage are important. Here we report 3 cases of unilateral or bilateral normal incisor shaped supernumerary lateral incisors treated by eruption observation, surgical extraction and orthodontic treatment with resin build-up.】

MORPHOLOGICAL FEATURES OF THE CROWNS OF MAXILLARY SECOND PRIMARY MOLAR AND FIRST PERMANENT MOLAR: AN ODONTOMETRIC STUDY

유치 치관의 기본적인 구조는 대개 계승 영구치를 닮는다. 그러나 제2유구치는 계승 영구치인 제2소구치보다 오히려 제1대 구치와 더 유사한 경향이 있다. 이에 본 연구는 한국인에서 상악 제2유구치와 제1대구치의 치아계측학적 자료(odontometric data)를 얻어 두 치아의 형태와 크기 사이의 연관성을 살펴보고, 나아가 남녀간의 차이점 유무를 고찰해 보고자 하였다. 남아 150명, 여아 150명 총 300명의 모형을 이용하여 상악 제2유구치와 상악 제1대구치의 근원심 치관 폭경, 협설측 치관 폭경, 각 교두의 직경, 교두정간 거리를 계측하였고, 치관의 교합면 사진을 촬영하여 각 교두정 사이의 각도를 측정하여 다음과 같은 결과를 얻었다. 1. 남아에서 Protocone index, Paraconeindex, Distobuccal cusp(DBC)각, Mesiobuccal cusp(MBC)각은 상악 제1대 구치와 제2유구치 사이에 통계적 유의차가 관찰되지 않았고(p>0.05), 중등도의 상관관계가 확인되었다. 2. 여아에서 crown index, Distobuccal cusp(DBC)각, Mesiobuccal cusp(MBC)각은 상악 제1대구치와 제2유구치 사이에 통계적 유의차가 관찰되지 않았고(p>0.05), 중등도의 상관관계가 확인되었다. 3. 남, 여 모두에서 Distobuccal cusp(DBC)각, Mesiobuccal cusp(MBC)각은 두 치아 사이에 유의할만한 차이를 보이지 않았고(p>0.05), Distolingual cusp(DLC)각에서는 통계적 유의차가 관찰되었다(p 0.05). 【The basic structure of the primary crowns usually resemble their succeeding permanent teeth. However, maxillary second primary molars resemble ipsilateral first permanent molars. Accordingly in this study, odontometric data of the two teeth was obtained, then analyzed to verify the morphological relationship and sex difference between the two teeth. Dental study casts were examined for their mesiodistal and buccolingual width of the crowns, diameter of each cusps, and intercuspal distances. Photographs of the crowns were taken to measure the angles between each cusp tip. The results are as follows : 1. In boys, PrI, PaI, DBC angle, and MBC angle did not show any statistically significant difference between the two teeth(p>0.05), and moderate level of correlations were observed. 2. In girls, crown index, DBC angle, and MBC angle of the two teeth did not show any statistically significant difference(p>0.05), and moderate level of correlations were recognized. 3. Measurements that did not show statistically significant difference between the two teeth in both boys and girls were DBC angle and MBC angle(p>0.05). In DLC angle, however, statistically significant difference was observed(p 0.05).】

A CASE REPORT AND DENTAL TREATMENT CONSIDERATIONS OF FIBRODYSPLASIA OSSIFICANS PROGRESSIVA PATIENT

Fibrodysplasia ossificans progressiva(FOP) is characterized by episodes of permanent heterotopic ossifications of soft tissues throughout the body. FOP is inherited in an autosomal dominant pattern, but most cases result from new mutations in the ACVR1 gene. Even minimal trauma can cause permanent ossifications of soft tissues and give rise to complications following routine dental care. Dental block anesthesia, severe stretching of the jaw and biopsies are all contraindicated in children with FOP. There is no effective treatment. Since the prevalence of FOP is very low and most patients with FOP are misdiagnosed during childhood, they undergo dangerous and unnecessary treatment that can lead to permanent harm. For patients with FOP, early diagnosis and prevention of complications are most important. This study aims at contemplating the characteristic features and consideration factors for the dental treatment of FOP patients in relation to the case of an eight years-and-one month old boy who was referred to Pediatric Dentistry due to prolonged retention of mandibular right and left deciduous central incisors after being diagnosed with sporadic FOP at Pediatric Orthopaedics, Seoul National University Hospital, and received dental treatment without the exacerbation of the FOP symptoms.