• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.2
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• pp.160-167
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• 2021

The purpose of this study was to investigate the prevalence and characteristics of pre-eruptive intracoronal radiolucencies (PEIR) from panoramic radiographs in Korean children and adolescents. This study examined panoramic radiographs of 3,000 patients aged between 5 and 14 years old who visited ten dental hospitals in Korea. The age and gender of the patients, the tooth type, the number of intracoronal radiolucent lesions, and the location and size of the lesions were recorded. The overall prevalence of patients with PEIR was 2.5%. The difference in the presence of PEIR between both genders was not significant. Within each tooth type, the mandibular first molar showed highest prevalence of PEIR (29.6%). The central part of the crown was the most frequently observed location of PEIR (56.8%). The size of the PEIR lesions was mostly limited to less than one-third of the thickness of coronal dentin.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.3
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• pp.277-291
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• 2023

This study aimed to compare the effects of applying different types of dentin bonding agents (DBAs) on tooth and on the sealing ability of CSC in regenerative endodontic procedures (REPs). Specimens were made from 120 human first premolars and categorized into the following groups based on the presence and the type of DBA: Group I, no bonding; Group II, One-Step; Group III, Clearfil SE Bond; and Group IV, Single Bond Universal. Subsequently, the groups were categorized into Subgroup a and Subgroup b, in which Endocem MTA^® Premixed Regular and Biodentine were used, respectively. The CIE L^*a^*b^* on the photos taken prior to TAP placement (S0), 1 week after TAP placement (S1), 2 weeks after TAP placement (S2), 4 weeks after TAP placement (S3) and 2 weeks after CSC placement (S4) was used to assess discoloration. The samples were submerged in a 2% methylene blue solution and magnified by 30 times under a stereomicroscope to assess microleakage. The application of DBA during REP reduced crown discoloration, while Biodentine showed minimal discoloration with or without DBA and regardless of the DBA type. Additionally, the application of DBA did not increase microleakage.

• The korean journal of orthodontics
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• v.39 no.1
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• pp.43-53
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• 2009

Objective: The purpose of this study was to compare the difference in three dimensional tooth movement using three different wire sizes($0.018{\times}0.025-in,\;0.016{\times}0.022-in$ 0.016-in) on a NiTi scissors-bite corrector. Methods: Computed tomography(CT) images of the experimental model before and after tooth movement were taken and reconstructed into three dimensional models for superimposition. The direction and the amount of tooth movement were measured and analyzed statistically. Results: The lingual and intrusive movements of the crown of the maxillary second molar were increased as the size of the NiTi wire increased. The roots of the maxillary second metals moved buccally except for the 0.016-in group. The intrusive movement of the roots of the maxillary second molars was increased as the size of the NiTi wire increased. Due to the use of orthodontic mini-implants, anchorage loss was under 0.2 mm on average. Conclusions: The $0.018{\times}0.025-in$ NiTi wire was most effective in lingual and intrusive movement of the maxillary second molar which was in scissors-bite position. Indirect skeletal anchorage with a single orthodontic mini-implant was rigid enough to prevent anchorage loss.

• Restorative Dentistry and Endodontics
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• v.27 no.4
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• pp.389-393
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• 2002

The marginal integrity of the crown can be broken during endodontic access cavity preparation due to the vibration of burs. Therefore, the purpose of this study was to evaluate the effect of endodontic access cavity preparation on the marginal leakage of full veneer gold crowns. 24 intact molars were mounted in acrylic resin blocks and prepared for crowns by a restorative dentist and crowns were cast with gold alloy. 20 Crowns were cemented with glass ionomer cement and 2 crowns were not cemented for positive control. 200 thermo-cycles from 5$^{\circ}C$ to 5$0^{\circ}C$ with a travel time of 20s were completed. Then samples were randomly divided into 2 experimental groups of 9 each. Endodontic access preparation and zinc-oxide eugenol temporary fillings were done in Group 1. Teeth in Group 2 were not treated. Samples were coated with 2 layers of nail varnish and were immersed in 1% methylene blue dye for 20 hrs. Endodontic access was prepared in 2 samples, which were coated with nail varnish on all surfaces for negative control. After washing in running water gold crowns were cut with a #330 bur. Four buccolingual sections, 2 mm apart, were cut from the central section of each tooth and were examined and scored under the microscope for dye leakage. Score 1: leakage to the cervical 1/3 of the axial wall, Score 2: leakage to the middle 1/3 of the axial wall, Score 3: leakage to the coronal 1/3 of the axial wall, Score 4: leakage to the occlusal surface. The median value for Group 1 is 4 and for Group 2 is 2. The result of this study showed that samples in Group 1 leaked more than those in Group 2. This finding was significant(P<0.001).

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.125-132
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• 2004

Statements of problem: All ceramic fixed partial denture cores can be made by the slip casting method and the advanced alumina tape method. The fracture resistance of these core connector areas is relatively low. Purpose: The purpose of this study is to standardize the appropriate volumetric figure and location of the connectors in the alumina core fabricated in alumina tape to be used in fixed partial dentures by way of topology optimization. Material and method: A maxillary anterior three-unit bridge alumina core with teeth form and surrounding periodontal apparatus model was used to ultimately design the most structurally rigid form of the connector. Loadings from a $0^{\circ}$, $45^{\circ}$ and $60^{\circ}$ to the axis of each tooth were applied and analyzed with the 3-D finite element analysis method. Using the results from these experiments, the topology optimization was applied and the optimal reinforcement layout of connector was obtained and the detail shape in the fixed partial denture core was designed. Results: The modified prosthesis with the form of a bulk in the lower lingual surface of the connector in the event, reduced the stress concentration up to 20% in the 3-D FEA. Conclusion: The formation of a bulk in the lower lingual connector area of an alumina core for a fixed partial denture decreases the stress to a clinically favorable measure but does not harm the esthetic point of view. This result illustrates the possibility of clinical application of the modified form designed by the topology optimization method.

• The Journal of Advanced Prosthodontics
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• v.8 no.3
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• pp.194-200
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• 2016

PURPOSE. The prospective follow-up aimed to assess the performance of lithium disilicate crowns and clinical reasons of adverse events compromising survival and quality. MATERIALS AND METHODS. 58 patients were treated with 375 heat-pressed monolithic crowns, which were bonded with resin cement. Annual recalls up to five years included a complete dental examination as well as quality assessment using CDA-criteria. Any need for clinical intervention led to higher complication rate and any failure compromised the survival rate. Kaplan-Meier-method was applied to all crowns and a dataset containing one randomly selected crown from each patient. RESULTS. Due to drop-outs, 45 patients (31 females, 14 males) with the average age of 43 years (range = 17-73) who had 327 crowns (176 anterior, 151 posterior; 203 upper jaw, 124 lower jaw) were observed and evaluated for between 4 and 51 months (median = 28). Observation revealed 4 chippings, 3 losses of retention, 3 fractures, 3 secondary caries, 1 endodontic problem, and 1 tooth fracture. Four crowns had to be removed. Survival and complication rate was estimated 98.2% and 5.4% at 24 months, and 96.8% and 7.1% at 48 months. The complication rate was significantly higher for root canal treated teeth (12%, P<.01) at 24 months. At the last observation, over 90% of all crowns showed excellent ratings (CDA-rating Alfa) for color, marginal fit, and caries. CONCLUSION. Heat pressed lithium disilicate crowns showed an excellent performance. Besides a careful luting, dentists should be aware of patients' biological prerequisites (grade of caries, oral hygiene) to reach full success with these crowns.

• The Journal of the Korean dental association
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• v.56 no.3
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• pp.159-166
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• 2018

The zirconia-reinforced lithium silicate ceramic material is a material in which lithium silicate glass contains about 10% by weight of zirconia oxide (zirconia oxide). This material has both the advantages of glass ceramics and zirconia, and it is attracting attention as a CADCAM material for single tooth restoration. ZLS materials have improved strength compared to widely used e.max (lithium disilicate ceramic) materials. It can be used for single crown restoration and ensuring a thickness of 1.5 mm is very important for reliable treatment. In the case of Celtra Duo, heat treatment may be helpful in terms of strength and abrasion resistance. Hydrofluoric acid treatment is helpful for bonding and hydrofluoric acid for a short time may not help to improve the bonding strength. Although zirconia-reinforced lithium silicate ceramic materials have been continuously conducted and published in the laboratory, reliable clinical studies are still lacking. Additional clinical studies will be a very important part of establishing a scientific basis.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.4
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• pp.646-650
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• 2007

The purpose of this study was to evaluate the prevalence of mesiodens at pediatric dental clinic in Anyang, Kyeong Gi-Do. From retrospective reviews of all patients who visited Kizwell pediatric dental clinic from 2003.4-2006.4, 241 patients (289 mesiodens) who were shown to have mesiodentes were examed by a periapical radiograph and a panoramic radiograph. The incidence of mesiodens was 3.42% and the ratio of male/female (184/57) was 3.2:1. The number of supernumerary teeth was one in 193 cases (80%), two in 48 cases (20%). The mesiodens was placed at left side more frequently and the most common shape was conical type (208, 78%). Of 289 mesiodens, the direction of the crown of the mesiodens was inverted in 156 (54%), in a normal direction in 104 (36%), in a horizontal direction with regard to the tooth axis in 29 (10%). Early diagnosis of the mesiodens allow the most appropriate treatment, often reducing the extent of surgery, orthodontic treatment and possible complications.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.3
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• pp.239-248
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• 2007

The accuracy and dimensional stability of rubber impression materials are very important for the fitness of the final restoration. The purpose of this investigation was to evaluate the effects of the storage time and pouring frequency of the additional silicone materials on dimensional stability. Total 30 impressions were made of tooth prepared single crown. The dies had 1 buccolingual, 1 mesiodistal and 1 occlusogingival lines. Two additional silicone materials(examixfine, aquasil) were included. 15 specimens were made of each impression material and poured by type IV stone over times(1hour, 24hours, 72hours) after mixing. 5 impressions poured after 1 hour were used for second pouring after 24hours and third pouring after 72hours. The same examiner measured each specimen 3 times after lazer scanning. All statistical tests were performed with the level of significance set at 0.05. The results indicated that significant difference at any measuring point of stone dies except the buccolingual and mesiodistal lines of the specimen made at 1hour after mixing with examixfine when measurements at 1hour, 24hours and 72hours were campared. There were significant difference between two impression materials and at every measuring point of stone dies made at second and third pouring. The length of measuring point increased significantly as time passed by and increase of the pouring frequency. However, this results are clinically acceptable except the dies of the third pouring. Under the conditions of this study, the shrinkage rate of the additional silicone rubber impression materials significantly increased as time passed by and increase of the pouring frequency.

• Journal of Oral Medicine and Pain
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• v.19 no.2
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• pp.221-231
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• 1994

Age determination in children have been criticized because they rely on subjective estimations of tooth development, as seen in radiographs. This study was undertaken to obtain the objective estimation of developing teeth. The panoramic radiograph of 254 males and 254 females ranging from 6 to 14 years of age were studied. The structures measured were crown height, apex width and root length. The data weree statistically investigated with SPSS/PC + package. The results were as follows : 1. With the aid of a multiple regression model, a linear relationship between some of these distances and age was shown. 2. In th total material(6-14yr) and four-yr. intervals, linear equations are as follow : Boys : 6-14 age = 683 + 145.6 44RL + 126.6.45RL + 71.1 46DRL - 161.3 46DAW 6-10 age = 1202 + 72.6 46DRL + 100.2 44RL + 75.1 45RL 8-12 age = 3818 + 75.9 45RL - 190.9 44AW 10-14 age = 4151 + 58.6 45RL - 84.0 45AW - 130.6 44AW Girls : 6-14 age = 1587 + 104.9 45RL + 113.4 44RL - 233.1 46DAW + 81.4 47DRL - 255.9 46MAW 6-10 age = 1821 + 55.8 46DRL + 67.2 45RL - 184.2 46MAW + 56.3 44RL 8-12 age = 2435 + 68.2 45RLL + 71.3 44RL 10-14 age = 3485 + 49.9 47DRL - 51.3 45AW - 179.9 47DAW + 33.4 45RL + 39.4 44RL (DRL, length of distal root in molars. RL, root length in premolars. DAW, width of distal apex in molars. MAW, width of mesial apex in molars. AW, width of apex n molars)