• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.1
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• pp.39-46
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• 2010

To assess the stress distribution of implant prosthesis induced by intentional misfit using photoelastic model. Stress was measured at the surrounding bone after applying vertical load to the implant. Three implants were placed in each of three photoelastic resin blocks. No misfits were used for the control group, while for the experimental group $100{\mu}m$ misfit after cutting the crown was used. The photoelastic stress analysis was performed. In control group, stress concentration was not shown when the load was not applied, whereas stress concentration was shown only in the loaded part even when load was applied and the stress was distributed in anterior-posterior direction when applying a load in the middle. When intentional misfits were given, stress around the fixture was incurred when tightening the screw even if load was not applied. If the load was applied, stress was concentrated around the implants including areas where the load was applied. In particular, the prosthesis made of UCLA showed more stress concentration as compared with a conical abutment. In the UCLA case, concentration was shown from the apex following through the axis to the cervical area. Prosthesis with misfit makes the stress concentrated though the load was not applied and it induces even more severe stress concentration when the load was applied. This founding demonstrates the importance of the correct prosthesis production.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.4
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• pp.673-677
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• 2006

The spectrum of pediatric dentistry has been changing recently, due to many socioeconomic changes and developments in dental materials. The purpose of this study was to recognize the changing pattern in pediatric dental treatment and to present the direction for pediatric dentistry in the future. Patient distribution and practice trends were reviewed based on the patient records of the department of pediatric dentistry, Seoul National University Dental Hospital, from 2000 to 2005. Results were as follows ; 1. In 2000, preventive treatments comprised 14.5%, restorative treatments 52.6%, surgical treatments 11.4% and orthodontic treatments 21.5%. In 2005, the percentages were changed to 12.1%, 38.3%, 13.7%, and 35.9% respectively, showing a decline in preventive and restorative treatments and an increase in surgical and orthodontic treatments. 2. In restorative treatments, the proportion of amalgam, stainless steel crown restoration and pulp treatments decreased, and that of glass ionomer and resin restoration increased. 3. The number of out-patients increased from 2000 to 2002, and decreased thereafter. 4. In 2005, the average age of patients decreased from that of 2000.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.3
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• pp.377-387
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• 2006

The objective of this study was to evaluate the influence of multiple adhesive coatings on the thickness of hybrid and adhesive layer and shear bond strength(SBS) of self-etch adhesives and self-etch primer adhesives. The buccal or lingual crown dentin of extracted human molars was used. Self-etch adhesives or self-etch primer adhesives were applied 1, 2 and 3 times on the dentin before light curing. In another group adhesives were reapplied after light curing first layer. Treated surfaces were prepared to measure the thickness of hybrid and adhesive layer with SEM, and shear bond strength to dentin using an Instron machine. The following results were obtained : 1. The adhesive layers increased with the number of coatings(p<0.05) with all adhesives. Adpor Prompt L-Pop and Xeno III were significantly thinner than self-etch primer adhesives (p<0.05). 2. The thickness of hybrid layers increased with the number of coatings (p<0.05). 3. The shear bonding strength of Unifil Bond and Clearfill SE Bond were higher than Scotchbond Multipurpose Plus and Adpor Prompt L-Pop (p<0.05), and similar with Xeno III. 4. The shear bond strength increased significantly with the number of coatings in Adpor Prompt L-Pop(p<0.05), but decreased at 3 times in AdheSE Bond(p>0.05). 5. In Adpor Prompt L-Pop and Xeno III, the shear bond strength decreased when adhesives were reapplied after curing the first adhesive layer.

• Restorative Dentistry and Endodontics
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• v.11 no.1
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• pp.33-41
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• 1985

The purpose of this study was to determine the extent of tooth structure crazing when pinhole were drilled in dentin at various distances from the dentionenamel junction, and when pins were inserted by hand wrench and Auto-klutch handpiece. Sixty freshly extracted teeth were embedded in blocks of cold-curing acrylic resin to a level 1mm apical to the cementoenamel junction, the crown of the teeth were removed to a level 1.5mm coronal to the cementoenamel junction. After being sectioned, the cut surface of the teeth were smoothed, and they were divided into 4 groups. Group I : 4 pinholes were drilled with self-threading Minim spiral drill and pins were inserted with hand wrench in fifteen teeth. Group II : 4 pinholes were drilled with self-threading Minim spiral drill and pins were inserted with Auto-klutch handpiece in fifteen teeth. Group III : 4 pinholes were drilled with self-threading Regular spiral drill and pins were inserted with hand wrench in fifteen teeth. Group IV : 4 pinholes were drilled with self-threading Regular spiral drill and pins were inserted with Auto-klutch handpiece in fifteen teeth. The cut surface were then examined microscopically for the presence or absence of craze line. The results were as follows: 1. The self-threading Minim pin groups (Group I & II) produced less craze lines than did the self-threading Regular pin groups (Group III & IV). 2. In the self-threading Minim pin groups, there was more craze lines with hand wrench (Group I) than with Auto-klutch handpiece (Group 11). 3. In the self-threading Regular pin groups, there was more craze lines with hand wrench (Group III) than with Auto-klutch handpiece (Group IV). 4. Placement of the pinhole at 0.0mm from the dentionenamel junction produced more craze lines than placed at 0.5mm, 1.0mm (p<0.05), however there was no statistically significant between the 0.5mm and 1.0mm distance.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.2
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• pp.145-156
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• 2010

Loss of posterior support may cause overloading and excessive wear of remaining teeth. Moreover, the extrusion of antagonistic teeth leads to the destruction of the occlusal plane. The loss of vertical dimension of occlusion (VDO) also emerges clinically, which may bring the loss of esthetic appearance and function. These patients who suffer from the loss of posterior support, often require vigorous periodontal treatments (osteotomy, crown lengthening) and extensive oral rehabilitation. Sixty three years old female patient visited for the prosthetic treatment of the posterior edentulous area. She had no other systematic disease and parafuctional habits for prosthetic treatment. Intraoral and radiographic examinations were done. The evaluation of VDO and vertical dimension of rest position were evaluated for proper prosthetic procedures and diagnostic wax up was done. As a result of diagnosis, VDO was increased by 2 mm considering the loss of VDO and space for the prosthetic treatment. After the pretreatments, initial preparation of teeth and provisionalization were carried out. Six weeks later of provisionalizaion, final preparation and impression was performed. Using the duralay resin copings, jaw relation was registered. The master cast was mounted and definitive restoration was fabricated. After the evaluation of esthetic and function, pick up impression for clinical remounting was done. Lucia jig was made for new jaw relation and occlusal adjustment on the articulator. Definitive restoration was delivered and the patient was periodically recalled for additional occlusal adjustment. From this case, the satisfactory functional and esthetic results through full mouth rehabilitation with increase vertical dimension were achieved.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.3
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• pp.224-235
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• 2013

A passively fitting prosthesis is an essential prerequisite to attain long-lasting success and maintenance of osseointegration. However, true "passive fit" can not be achieved with the present implant-supported prosthesis fabrication protocol. Many clinical situations are suitably treated with cantilevered implant-supported fixed restorations. The purpose of this study was to compare the stress distribution pattern and magnitude in supporting tissues around ITI implants with cantilevered, implant-supported, screw-retained fixed prosthesis according to the fitness of superstructures. Photoelastic model was made with PL-2 resin (Measurements, Raleigh, USA) and three ITI implants (${\phi}4.1{\times}10mm$) were placed in the mandibular posterior edentulous area distal to the canine. Anterior and posterior extended 4-unit cantilevered FPDs were made with different misfit in the superstructures. 4 types of prosthesis were made by placing a $100{\mu}m$ gap between the abutment and the crown on the second premolar and/or the first molar. Photoelastic stress analysis were carried out to measure the fringe order around the implant supporting structure under simulated loading conditions (30 lb).

• Restorative Dentistry and Endodontics
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• v.15 no.1
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• pp.57-66
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• 1990

The author conducted a dental survey of college girl students and compared with that of college students 20 years and 10 years ago which based on the same criteria. The items of this survey included the prevalence of dental caries, DMFT and the kinds of restored materials. College girl students 2,294 were examined in May 1988, with the recommended criteria and method of W.H.O.. Among them, the data of 2,243 were analyzed and compared with the data of 1968 and 1978. The following results were obtained : 1. The average number of present teeth was $28.86{\pm}1.65$, which does not show much difference when compared to $29.00{\pm}1.94$ of 1968 and $28.97{\pm}1.64$ of 1978. 2. The prevalence of dental caries was 86.22%, which increased in comparison to 83.25% of 1968 and 84.92% of 1978. 3. DMF index was 19.98, which considerably increased in comparison to 14.56 of 1968 and 15.51 of 1978. 4. The number of DMFT was $5.75{\pm}5.04$ per student. Compared to $4.23{\pm}3.88$ of 1968 and $4.49{\pm}3.69$ of 1978, there is a considerable increase. I) The average number of decayed(D) teeth was $1.14{\pm}1.63$, which decreased from $1.16{\pm}1.57$ of 1968 and $2.09{\pm}2.16$ of 1978. II) The average number of missing(M) teeth was $0.23{\pm}0.73$, which also decreased from $0.69{\pm}1.11$ of 1968 and $0.32{\pm}0.79$ of 1978. III) The average number of filled(F) teeth was $4.39{\pm}4.91$, which increased from $2.38{\pm}3.33$ of 1968 and $2.09{\pm}3.17$ of 1978. 5. According to the analysis of filling material, filling baby including amalgam, gold inlay, resin, silicate cement and paladium inlay was 90.5%, which increased in comparison to 72.8% of 1968 and 83.6% of 1978. Among them, amalgam occupied 62.93%, which showed the most increase. On the other hand, crown and bridge was 6.5%, 3.0%, respectively, which showed continuous decrease from 12.1%, 15.1% of 1968 and 8.7%, 7.7% of 1978. Therefore, the prosthodontic treatment reduced due to the decrease of tooth extraction. In contrast, there is continuous increase of conservative treatment which maintaining natural tooth.

• The Journal of Advanced Prosthodontics
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• v.12 no.2
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• pp.100-106
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• 2020

PURPOSE. The purpose of this in vitro study was to evaluate the fitting accuracy of single crowns made from a novel presintered Co-Cr alloy prepared with a computer-aided design and computer-aided manufacturing (CAD/CAM) technique, as compared with crowns manufactured by other digital and the conventional casting technique. Additionally, the influence of oxide layer on the fitting accuracy of specimens was tested. MATERIALS AND METHODS. A total of 40 test specimens made from Co-Cr alloy were investigated according to the fitting accuracy using a replica technique. Four different methods processing different materials were used for the manufacture of the crown copings (milling of presintered (Ceramill Sintron-group_cer_sin) or rigid alloy (Tizian NEM-group_ti_nem), selective laser melting (Ceramill NPL-group_cer_npl), and casting (Girobond NB-group_gir_nb)). The specimens were adapted to a resin model and the outer surfaces were airborne-particle abraded with aluminum oxide. After the veneering process, the fitting accuracy (absolute marginal discrepancy and internal gap) was evaluated by the replica technique in 2 steps, before removing the oxide layer from the intaglio surface of the crowns, and after removing the layer with aluminum oxide airborne-particle abrasion. Statistical analysis was performed by multifactorial analysis of variance (ANOVA) (α=.05). RESULTS. Mean absolute marginal discrepancy ranged between 20 ㎛ (group_cer_npl for specimens of Ceramill NPL) and 43 ㎛ (group_cer_sin for crowns of Ceramill Sintron) with the oxide layer and between 19 ㎛ and 28 ㎛ without the oxide layer. The internal gap varied between 33 ㎛ (group_ti_nem for test samples of Tizian NEM) and 75 ㎛ (group_gir_nb for the base material Girobond NB) with the oxide layer and between 30 ㎛ and 76 ㎛ without the oxide layer. The absolute marginal discrepancy and the internal gap were significantly influenced by the fabrication method used (P<.05). CONCLUSION. Different manufacturing techniques had a significant influence on the fitting accuracy of single crowns made from Co-Cr alloys. However, all tested crowns showed a clinically acceptable absolute marginal discrepancy and internal gap with and without oxide layer and could be recommended under clinical considerations. Especially, the new system Ceramill Sintron showed acceptable values of fitting accuracy so it can be suggested in routine clinical work.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.1
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• pp.69-75
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• 2002

A number of techniques may be employed to reduce the discomfort of syringe or needle for dental care. The use of topical anesthesia is one such method. Topical anesthetics are applied to alleviate pain during many clinical procedures, such as injection of local infiltration anesthetics, primary tooth extraction, X-ray taking of sensitive patients, reducing gag reflex prior to impression taking. In children, placement of a rubber dam clamp, however, may cause significant discomfort for purpose of pit and fissure sealant and preventive resin restoration(PRR). A topical anesthetic would be beneficial to aid in rubber dam placement for this purpose. It has been suggested that all intra-oral topical anesthetics are equally effective on reflected mucosa, however EMLA(an acronym for eutectic mixture of local anesthetics), which was developed in the 1980s and produces surface anesthesia of skin, has been shown to be more effective than conventional topical anesthetics when used on attached gingivae. This report is topical anesthesized 4 case by EMLA cream, who showed better effect in reducing the pain of infiltration anesthesia, extraction of deciduous teeth, rubber dam clamp placement and reducing the pain of preformed crown adaptation.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.12 no.2
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• pp.96-100
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• 2016

Metachromatic leukodystrophy (MLD) is a progressive and degenerative neurological disease caused by a deficiency of the catabolic enzyme arylsulfatase A. Deficiency of arylsulfatase A results in accumulation of sulfatide in the white matter of the peripheral and central nervous system and it occurs demyelination as a result. The patient gradually goes through mental and motor failure. General symptoms of MLD include gait disturbance, mental deterioration, muscle rigidity and impaired swallowing. Inheritance of the disease is autosomal recessive. We report a dental caries treatment of a 3-year old boy with MLD. The patient underwent hematopoietic stem cell transplantation (HSCT) to slow the progression of the disease. He was suffered from difficulties of mastication and swallowing from the degenerative neurological symptom. He was ingesting food by both oral feeding and tubal feeding after he took percutaneous endoscopic gastrostomy (PEG). The cause of multiple caries was mainly presumed as patient's prolonged time of meal. The treatment was performed under general anesthesia considering patient's incompliance. Severely affected lower primary molars were treated with pulp treatment and restored with stainless steel crown. Others were restored with composite resin. There were no postoperative complications. MLD is life threatening progressive disease and also has an impact on unfavorable condition for oral health. Routine home oral care and periodic professional dental care should be emphasized to the caregiver of patient considering the susceptibility of dental caries. Not only the medical care, but periodic dental office visit would benefit the quality of life of the patient.