• The korean journal of orthodontics
• /
• v.42 no.5
• /
• pp.249-254
• /
• 2012

Objective: To investigate the stem cell-like characteristics of human periodontal ligament (PDL) stromal cells outgrown from orthodontically extracted premolars and to evaluate the potential for myogenic differentiation. Methods: PDL stromal cells were obtained from extracted premolars by using the outgrowth method. Cell morphological features, self-replication capability, and the presence of cell-surface markers, along with osteogenic, adipogenic, and chondrogenic differentiation, were confirmed. In addition, myogenic differentiation was induced by the use of 5-aza-2'-deoxycytidine (5-Aza) for DNA demethylation. Results: PDL stromal cells showed growth patterns and morphological features similar to those of fibroblasts. In contrast, the proliferation rates of premolar PDL stromal cells were similar to those of bone marrow and adipogenic stem cells. PDL stromal cells expressed surface markers of human mesenchymal stem cells (i.e., CD90 and CD105), but not those of hematopoietic stem cells (i.e., CD31 and CD34). PDL stromal cells were differentiated into osteogenic, adipogenic, and chondrogenic lineages. Myotube structures were induced in PDL stromal cells after 5-Aza pretreatment, but not in the absence of 5-Aza pretreatment. Conclusions: PDL stromal cells isolated from extracted premolars can potentially be a good source of postnatal stem cells for oromaxillofacial regeneration in bone and muscle.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.24 no.1
• /
• pp.107-113
• /
• 1994

The purpose of this study was to evaluate the prevalence, distribution, and its relation with adjacent roots of idiopathic osteosclerosis in the jaws by means of the analysis of the 6,220 persons' full mouth periapical radiographs. And the following results were obtained; 1. The prevalence of idiopathic osteosclerosis in the jaws was revealed to be 2.43% in total examined persons, and there was a higher prevalence in females(3.12%) than in males(1.68%). 2. There was a higher prevalence in the mandible(94.3%) than in the maxilla(5.7%), and the most frequently involved area was the mandibular premolar area(51.9%), followed by mandibular molar area(21.52%). 3. According to the types of relation with adjacent roots, separated type(53.8%) in idiopathic osteosclerosis was the most frequent, followed by apical type(40.51%), interradicular type(3.18%), apical and interradicular type(2.51%) in descending order of frequency.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.24 no.1
• /
• pp.129-135
• /
• 1994

This study was performed to evaluate the accuracy of orthopantomogram by measuring the actual and radiographic tooth length and by analyzing the vertical magnification rate. For this study, total 90 teeth of the maxilla and mandible teeth and a dry skull were used. This experiment was attached with metal balls of 1±0.02㎜ at the root and the crown cusp tips of central, 2nd premolar, 1st molar of the maxilla and mandible and the teeth were embedded in dry skull, and then orthopantomogram was taken. The obtained results were as follows: 1. The average of tooth length in orthopantomogram was longer than that of actual tooth length. 2. The average of vertical magnification rate in the orthopantomogram to actual tooth length was 17-26%. 3. Vertical magnification rate of the maxilla teeth was 18-26% and that of mandibular teeth was 17-23%, and the magnification of maxillary teeth was larger than that of mandible teeth(P<0.0l). 4. Vertical magnification rate of posterior area was 22-26% and that of anterior area was 17-18%, and the magnification of anterior area was less than that of posterior area(P<0.01).

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.42 no.4
• /
• pp.231-235
• /
• 2016

A benign cementoblastoma, which is another name for a true cementoma, is a rare neoplasm that develops from odontogenic ectomesenchyme. It is characterized by a mineralized mass attached to the apex of the root produced by neoplastic cementoblasts. More than 75% of cases arise in the mandible, with 90% of them manifesting in the molar and premolar regions. This neoplasm occurs most commonly in children and young adults, with males being affected slightly more than females. Radiographically, the tumor is observed as a well-defined radiopaque mass that is fused to a tooth root and is surrounded by a radiolucent rim. The treatment of benign cementoblastoma consists of removal of the lesion and extraction of the affected tooth. This report presents an unusual case of benign cementoblastoma in a 31-year-old female, presenting as a densely mineralized mass seen at the apex of the impacted right mandibular canine tooth on radiographs.

• The Journal of Advanced Prosthodontics
• /
• v.7 no.1
• /
• pp.15-20
• /
• 2015

PURPOSE. The aim of this study was to evaluate whether the push-out bond strength varies between oval and circular fiber posts, and to examine the effect on the resin cement thicknesses around the posts. MATERIALS AND METHODS. Eighteen mandibular premolar roots were separated into two groups for oval and circular fiber posts systems. Post spaces were prepared and fiber posts were luted to the post spaces. Roots were cut horizontally to produce 1-mm-thick specimens. Resin cement thicknesses were determined with a metallographic optical microscope and push-out tests were done. RESULTS. No significant differences were observed in terms of push-out bond strength between the oval and circular fiber posts (P>.05) The resin cement thicknesses of the oval posts were greater than those of the circular posts group in the coronal, middle and apical specimens (P<.05). CONCLUSION. In the light of these results, it can be stated that resin cement thickness does not affect the push-out bond strength.

• The Journal of Korean Academy of Prosthodontics
• /
• v.38 no.2
• /
• pp.255-263
• /
• 2000

The purpose of this study was to compare the microleakage of the composite resin cores according to surface treatment, dentin bonding agents, and thermocycling. For this study, 120 extracted premolar teeth were used. Flat occlusal surfaces were prepared with diamond disk, and treated with air-abrasion, acid-etching, combination. The composite resin core was built with Z-100 after application of Scotchbond Multi-Purpose and All-Bond 2. Prepared specimens were thermocycled for 2,000 cycles. Specimens were immersed in 1% methylene blue solution for 24hours at $37^{\circ}C$. The microleakage was measured with a inverted metallurgical microscope(BHS313, Olympus, Japan). The following conclusions were drawn from this study: 1. The microleakages in the groups treated with air-abrasion and with acid etching were greater than that of the groups treated with combination method before thermocycling(p<0.05), the microleakages of the groups treated with air-abrasion were greater than that of the groups treated with acid-etching and combination method after thermocycling(p<0.05) 2. There were no significant difference between groups using Scotchbond Multi-Purpose and the groups using All-Bond 2. 3. Thermocycling didn't affect the change of microleakage in all cases.

• Journal of Periodontal and Implant Science
• /
• v.34 no.4
• /
• pp.723-731
• /
• 2004

Helicobacter pylori(H. pylori) has been associated with the cause of chronic gastritis, peptic ulcers and gastric cancer. Although it may be transmitted through the oral cavity, it is unknown whether the oral cavity acts as a reservoir of H. pylori. The purpose of this study was to investigate the mode of detection of H. pylori in oral cavity of adult periodontitis patients with plaque and periodontal pocket which atmosphere is grown well H. pylori. We analysed detection rate of H. pylori in saliva and subgingival plaques of 17 adult periodontitis patients without symptoms of gastroduodenal disease by nested PCR. Samples tested comprised saliva and subgingival plaques from central incisor, 1st premolar and 1st molar. H. pylori DNA was not identified in saliva from all patients. The detection rate in subgingival plaque from incisors, premolars and molars was 5.9%, 5.9% and 17.7%, respectively. In conclusion, the dental plaque and periodontal pocket (especially, of molars) in adult periodontitis can be favorable reservoir of H. pylori and may be the source of infection and transmission of H. pylori.

• The korean journal of orthodontics
• /
• v.23 no.3 s.42
• /
• pp.319-326
• /
• 1993

The purpose of this study was to evaluate the frequency of congenital missing teeth and supernumerary teeth in cleft patients. The subjects were divided into bilateral cleft lip and palate(BCLP), unilateral cleft lip and palate(UCLP) and cleft palate alone(CP alone) groups. 97 cleft patients(BCLP 15, UCLP 70, CP alone 12) between 6-20 years old were evaluated. Panorama film, Orthodontic chart and initial intraoral photogram were employed for this research. The obtained results were as follows. 1. The incidence of congenital missing teeth in total cleft samples was $57.7\%$, and the incidence of supernumerary teeth was $26.8\%$. Each incidence was higher than non-cleft. 2. The incidence of congenital missing teeth was the highest in BCLP and the lowest in CP alone. 3. The number of congenital missing teeth per perso was usually one, and the frequency was higher in the maxillary lateral incisors$(67.8\%)$, and maxillary second premolar$(14.9\%)$ than other teeth. 4. Most of tooth number anomalies in cleft patients were found in maxilla, especially adjacent region to the cleft site.

• The korean journal of orthodontics
• /
• v.23 no.4 s.43
• /
• pp.607-618
• /
• 1993

If the centric prematurity occurs after orthodontic treatment, it creates centric slide regarded as a possible factor in the cause of temporomandibular disorder and/or postorthodontic relapse. The purpose of this study was to investigate the manner of centric prematurity and centric slide in postorthodantic patients. The 36 orthodontic patients who had been treated with edgewise appliance at least 3 mouths previously were used in this study. After recording centric relation by the leaf gauge technique, the centric prematurity and centric slide were studied using SAM2 articulator and mandibular position indicator. The results were as follows : 1. The highest percentage of centric prematurities were found on the second molars. 2. The buccal incline of the palatal cusp was the most frequent area of centric prematurities in the maxilla, while the lingual incline of the buccal cusp was the most frequent area in the mandible. 3. There were no trends in the direction of centric slide on the mandibular position indicator. 4. There were no significant differences in centric discrepancies between the premolar extraction and nonextraction group.

• The korean journal of orthodontics
• /
• v.23 no.4 s.43
• /
• pp.619-631
• /
• 1993

Tooth movement by segment is one of the means which are frequently used in daily orthodontic practice. When we retract or intrude a tooth or teeth, we should recognize the center of resistance of the certain tooth or teeth. There have been many studies about the center of resistance of a single tooth, not so much was about the tooth-segment. At the present study the center of resistance of the maxillary anterior segment is experimentally investigated by using laser reflection technique and metal splints on the human dry skull. The variables of intrusive force magnitude are divided into two groups, 50g and 100g groups. The results were as follows ; 1. The center of resistance of the maxillary anterior segment composed of the central and lateral incisors was at the mesial portion of canine crown at the coronal level. 2. The center of resistance of the maxillary anterior segment composed of the central and lateral incisors and canines is between the canine and the 1st premolar crowns at the coronal level.