• Journal of the Korean Ceramic Society
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• v.39 no.11
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• pp.1028-1034
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• 2002

Spinel/zirconia-glass composites prepared by melt-infiltration were fabricated to investigate the effect of zirconia addition on mechanical and optical properties of the composites. The infiltration distance was parabolic with respect to time as described by the Washburn equation and the penetration rate constant, K, decreased due to the reduction in pore size as the amount of zirconia rose. Although the optimum strength(308 MPa) of the Spinel/zirconia-glass composites was observed when the zirconia was added up to 20 wt%, K and transmittance decreased as the zirconia content rose. In conclusion, it suggested that the positive effect of strength as a result of the addition of zirconia was not effective.

• Journal of Korean Dental Science
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• v.12 no.2
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• pp.48-57
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• 2019

Purpose: To investigate whether there are specific surgical or clinical conditions where the use of autogenous bone (AB) is superior to the use of bone substitutes (BSs) for maxillary sinus floor augmentation (MSFA). Materials and Methods: We retrospectively analyzed 386 implants after MSFA in 178 patients. The implants were divided into five groups according to the sinus graft material used. Risk factors for implant failure in MSFA, and correlation between residual bone height (RBH) and graft materials in terms of implant survival were investigated. To investigate risk factors for implant failure in MSFA, implant survival according to graft materials, patients' sex/age, surgical site, RBH, healing period prior to prosthetic loading, staged- or simultaneous implantation with MSFA, the crown-to-implant ratio, prosthetic type, implant diameter, and opposite dentition were evaluated. Result: The cumulative 2- and 5-year survival rates of implants placed in the grafted sinus (independent of the graft material used) were 98.7% and 97.3%, respectively. None of the investigated variables were identified as significant risk factors for implant failure. There was also no statistical significance in implant survival between graft materials. Conclusion: There were no specific surgical conditions in which AB was superior to BSs in terms of implant survival after MSFA.

• The korean journal of orthodontics
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• v.47 no.5
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• pp.277-288
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• 2017

Objective: Treating Class II subdivision malocclusion with asymmetry has been a challenge for orthodontists because of the complicated characteristics of asymmetry. This study aimed to explore the characteristics of dental and skeletal asymmetry in Class II subdivision malocclusion, and to assess the relationship between the condyle-glenoid fossa and first molar. Methods: Cone-beam computed tomographic images of 32 patients with Class II subdivision malocclusion were three-dimensionally reconstructed using the Mimics software. Forty-five anatomic landmarks on the reconstructed structures were selected and 27 linear and angular measurements were performed. Paired-samples t-tests were used to compare the average differences between the Class I and Class II sides; Pearson correlation coefficient (r) was used for analyzing the linear association. Results: The faciolingual crown angulation of the mandibular first molar (p < 0.05), sagittal position of the maxillary and mandibular first molars (p < 0.01), condylar head height (p < 0.01), condylar process height (p < 0.05), and angle of the posterior wall of the articular tubercle and coronal position of the glenoid fossa (p < 0.01) were significantly different between the two sides. The morphology and position of the condyle-glenoid fossa significantly correlated with the three-dimensional changes in the first molar. Conclusions: Asymmetry in the sagittal position of the maxillary and mandibular first molars between the two sides and significant lingual inclination of the mandibular first molar on the Class II side were the dental characteristics of Class II subdivision malocclusion. Condylar morphology and glenoid fossa position asymmetries were the major components of skeletal asymmetry and were well correlated with the three-dimensional position of the first molar.

• Journal of Technologic Dentistry
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• v.41 no.4
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• pp.271-278
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• 2019

Purpose: To quantify the effect of the crystallization process on lithium disilicate ceramic crowns that are fabricated using a computer-aided design/computer-aided manufacturing(CAD/CAM) system, and to determine whether they are clinically acceptable by comparing values before and after the crystallization process. Methods: The maxillary first molar was selected as the abutment for the experiments. Ten working models were prepared. Marginal and internal gap of 4 groups of lithium disilicate crowns(n=10) fabricated with conventional method. Comparison was performed using the silicone replica technique and 3D superimposition analysis. The marginal and internal gaps of the restoration were measured before and after the crystallization process of this prosthesis. The average value of each part(the average of values measured before and after the crystallization) was statistically analyzed using paired t-test(α=0.05). Results: The results from the second phase of this research, which compared the average value of the gap between the marginal and internal fits of the lithium disilicate single crown before and after the crystallization process, indicated that the marginal gap was larger and the internal gap was smaller after the crystallization process, and this difference was statistically significant (P<0.05) in all the parts evaluated. Conclusion: While the shrinkage that occurs during crystallization does affect the marginal and internal fit of the prosthesis, it cannot be concluded to be a major effect because the resultant distortion was within the clinically acceptable range.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.5
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• pp.234-239
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• 2002

The spinel was calcined at temperatures in the range of $1000^{\circ}C$ to $1300^{\circ}C$ with $100^{\circ}C$ interval to evaluate the effect of calcination temperature on mechanical properties of spinel-glass dental composites. Although the average particle size of spinel calcined at temperatures from $1000^{\circ}C$ to $1200^{\circ}C$ was within 2.8~3.0 $\mu\textrm{m}$, the spinel calcined at $1300^{\circ}C$ was 4.66 $\mu\textrm{m}$ due to abnormal grain growth. Shrinkage and pore size of the spinel preform decreased and increased, respectively, as calcination temperature increased, indicating that the calcination temperature was significant to the powder compaction and the densification of the composites as a result of particle size and distribution. The optimum strength and the fracture toughness of the composite calcined at $1200^{\circ}C$ were 284$\pm$40 MPa, 2.5$\pm$0.1 MPaㆍ$m^{1/2}$ respectively. Optical experimental results showed that transmittance of the spinel-glass composite in the visible region was twice higher than that of the alumina-glass composite, suggesting that the spinel-glass composites possessed better aesthetic properties for all-ceramic dental crown application.

• 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.21 no.1
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• pp.43-57
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• 2005

Temporomandibular disorders have been defined as a collective term embracing a number of clinical problems that involve the temporomandibular joint, the masticatory nuscles, and associated structures. There have been many different contributing factors of TMDs which were traumatic, occlusal, pathophysiological and psychosocial. Among there factors, the effect of occlusion on TMDs have been a controversy for a long time. The purpose of this study was to investigate the effect of occlusal factors and oral habits on TMDs. In this study, 140 subjects with signs and symptoms of TMDs and diagnosed of TMD in the Orofacial Pain clinic of Yonsei University Dental Hospital though March to July 2004 were selected for the TMDs group and 50 subjects without any signs and symptoms of TMDs as the control group. The subjects were evaluated clinically in TMDs' Occlusal and Prosthodontic Restoration examinations. TMDs' examination was composed of the TMJ pain, sound, locking, temporal or masseter muscle palpation, mandibular movement, oral habits and headache. Occlusal examination was made of overjet, overbite, lost teeth number, nonfunctional interference, midline shift, then pattern of lateral movement and attrition. prosthodontic restoration examination had the existence of restoration, placement, then number of crown or bridge and Satisfiable index which estimated the quality of occlusal state of prosthodontic restorations. Following results were obtained : 1. The prevalence of TMDs was higher in their 20s & 30s, female of the TMD patients group. 2. The clenching frequency in the TMDs group(40.71%) was higher than those in the control group(18.00%), and there was a significant statistical difference(p<0.05). 3. The frequency of Nonfunctional interference in the TMDs group(10.00%) was higher than those in then Control group(2.00%), and there was a significant statistical difference(p<0.05). The result of this study indicated TMDs prevalence was higher in their 20s, 30s, female group of TMDs patients similar to the previous studies. Clenching and nonfunctional interference were estimated as the contributing factors of TMDs.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.8 no.2
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• pp.109-112
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• 2012

Epidermolysis bullosa (EB) is an inherited skin disease characterized by blister formation of the skin following just minor trauma or spontaneously. The main classification of EB is based on the localization of the blistering. In epidermolysis bullosa simplex, the blister formation is intraepidermal; in epidermolysis bullosa junctionalis the blister formation in the epidermal-dermal junction; in the dystrophic forms of EB blister formation is intradermal. Oral manifestations of recessive dystrophic EB are characterized by rampant caries, crowding, microstomia, ankyloglossia, vestibular obliteration. Dental therapy may be well provided to patient with recessive dystrophic EB by using general anesthesia especially in case of poor cooperation. A two years old girl with recessive dystrophic EB visited our clinic for rampant caries. She was hospitalized for severe anemia and fever, and we provided dental therapy under general anesthesia. Extraction of incisors and stainless steel crown restoration of primary molars were performed.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.14 no.1
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• pp.31-35
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• 2018

Dentinogenesis imperfecta is a hereditary disorder that causes abnormal dentin formation and tooth morphology. Affected teeth show very thin dentin and large pulp chamber. Immediately after their eruption, the teeth tend to be destroyed rapidly. Early dental intervention is recommended to improve the feeding capacity and quality of life for the child, to maintain vertical dimension, and to promote healthy and functional dentition. This case report describes a treatment for a 4-year-2-month-old girl whose primary and permanent dentition were affected by Dentinogenesis Imperfecta. Shell teeth were observed in the entire primary dentition. The pulp of most teeth was exposed and the patient complained of pain. Most paternal family members were transferred to the Dentinogenesis Imperfecta. She needed an extensive dental treatment, but her compliance could not be expected because she was very young and anxious. So we decided to treat her under general anesthesia. All molar teeth are restored with Stainless Steel crown. Maxillary anterior teeth were extracted and mandibular anterior teeth are restored with composite resin. The patient's pain disappeared and masticatory function was restored.

• Journal of Technologic Dentistry
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• v.15 no.1
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• pp.89-94
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• 1993

The tooth size and shape of the permanent incisor teeth have been studied and analyzed about the mean size, S.D, S.E, etcs and percentage from stone model of 100 Korean male and 74 Korean female. The results were as follows. 1. The crown length of permanent incisor teeth were longer in males than in females statistical differences of males and female were not found. 2. the mesio-distal diameters of permanent incisor teeth were larger in males than in females and statistical differences of males and females were found in mandibular lateral incisor and the bigest were max. central incisor, 2nd max. lateral incisor, 3rd man. lateral incisor and the smallest were man. central incisor. 3. The square form in max. central incisor was the greatest percentage and the tapering form in max. lateral incisor and man, incisor was the greatest percentage but tapering form and ovoid form and other shape were found in max. lateral at the same ratio. 4. Concerning the labial developmental groove "midium" was the greatest percentage in the max. central incisor and "low" was the greatest percentage in the man incisor. Concerning the incisal line, straight line was the greatest percentage in the max, incisor and man, incisor and concerning the lingual tubercle "none" was the greatest percentage in the max. incisor. 5. In comparison between left side and right side of incisor, the ratio of same shape ware 22.4%-36.2% but similar or dissimilar cases were more frequently found.