• 대한기계학회논문집
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• 제9권5호
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• pp.572-578
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• 1985

본 논문에서는 인벌류우트와 원고치형의 단점을 보완하고 양자의 장점을 취한 치형을 얻기위하여 피치점 부근에서는 인벌류우트치형으로 이끝부분에서는 원호로 하 고 이뿌리부분에서는 상대방 기어의 원호부분과 맞물릴 수 있는 곡선으로 하는 치형을 합성하고, 이 합성치형의 유효치형을 가공할 수 있는 랙치형을 이론적인 방법으로 구 하였다. 그리고, 이 합성치형의 유효치형에 대한 이끝과 이뿌리 두께의 변화와 물림 률을 검토하였다.

• 대한치과의사협회지
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• 제54권7호
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• pp.542-550
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• 2016

Recent technological advance have greatly expanded the application of invisible orthodontic treatment using clear thermoplastic materials. However, the final outcomes using clear aligner system do not achieve the level of final goal frequently, which results in case refinement, midcourse correction, or fixed orthodontic treatment. Therefore, mechanical properties of thermoplastic materials should be considered to improve the quality of outcomes. The purposes of this special article were to evaluate the force and stress depending on the materials, deflection and thickness of thermoplastic materials and to evaluate the mechanical properties of thermoplastic materials after repeated loading. Thickness and amount of deflection rather than products and materials showed the largest effect on force and stress. In all products, at least 159 gf of force was required for more than 1.0 mm deflection or when materials with 1.0 mm thickness were deflected. Orthodontic forces delivered by thermoplastic materials depend on the materials, thickness, amount of activation, and intra-oral condition. Proper thickness of thermoplastic materials and deflection level of tooth movement should be decided for the efficient and physiologic tooth movement.

• The Journal of Advanced Prosthodontics
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• 제2권4호
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• pp.122-127
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• 2010

PURPOSE. The aim of this study was to examine the relationship between tooth loss and sub-clinical atherosclerosis in Korean adults. MATERIALS AND METHODS. The subjects were part of a cohort study conducted in Ansan city by the Korea University medical school as part of the Korean Genome project. 749 subjects over than 40 years old were evaluated. After taking panoramic radiography, the amount of tooth loss was calculated. The intima-media thickness (IMT) was assessed by using ultrasonography at the common carotid artery. Traditional cardiovascular risk factors for atherosclerosis were also evaluated. The relationship between tooth loss and the IMT was evaluated using ANOVA with Scheffe's multiple comparison method in univariate analysis. Multiple regression analysis was also performed to determine the significance between the IMT and tooth loss. RESULTS. With age, tooth loss increased, but there was no significant increase in other traditional cardiovascular risk factors. Univariate analysis revealed the IMT to be positively related with the amount of tooth loss. Regression analysis of the IMT in the anterior and posterior tooth loss revealed that only the posterior tooth loss was significantly related with the IMT at all sites of the common carotid artery (right far wall, P = .015; left far wall, P = .008; right near wall, P < .001; left near wall, P = .001). CONCLUSION. This study verified the positive relationship between the increased tooth loss at the posterior area and the accumulation of atheroma in arteries.

• 대한기계학회논문집
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• 제18권5호
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• pp.1347-1354
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• 1994

This paper deals with the experimental research, including measurement and analysis and field survey, on the causes of occurring noise defective gear boxes in hoist production plant in order to reduce the fraction of their occurrence. In this reserch following investigations are performed : measurement and gear-boxes, examination of each machining process of production, measurement and analysis of dimensional accuracy of each part, comparative vibration test with exchanging inaccurate parts. From these investigations, it is found that the machining accuracy of pinion gear tooth thickness is the most sensitive factor of noise problem. By maintaining the tooth thickness error within 0.05 mm tolerance in the gear cutting process, the fraction of noise defective gear-boxes are greatly reduced to less than 2%, where the usual rate of it has been 20-50%.

• Restorative Dentistry and Endodontics
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• 제27권1호
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• pp.16-23
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• 2002

Physical properties of composite resins such as strength, resistance to wear, discoloration, etc depend on the degree of conversion of the resin components. The purpose of this study was to evaluate the degree of conversion of the composite resins according to the thickness of tooth structure penetrated by light and applied light curing time. The coronal portions of extracted human teeth (one anterior tooth, three posterior tooth) was embedded by pink denture material. the mounted teeth were cut into three illumination sections (1mm thickness enamel section, 1mm thickness dentin section, 2mm thicknes dentin section) and one backing section with cutting wheel. Thin resin films were made by using 6kg pressure between slide glass during 5 minutes Thin resin film was light cured on coupled illumination section during 40sec, 80sec and 120sec. each illumination section was coupled as follows; no tooth structure(X), ename section(E), enamel section + 1mm dentin section(ED1), enamel section + 2mm dentin section(ED2), enamel section + 1mm dentin section + 2mm dentin section(EDD). To simulate the clinical situation more closely, thin resin films was cured against a backing section of tooth structure. The degree of conversion of carbon double bonds to single bonds in the resin films were examined by means of Fourier Transform Infrared Spectrometer. The results were obtained as follows ; 1 As curing time was increased, conversion rate was increased and as tooth thickness which was penetrated by curing light was increased, conversion rate was decreased. 2. At all tooth thickness groups, conversion rate between 80sec and 120sec was not significantly increased(P＞0.05). 3. At 40sec group and 80sec, conversion rate between no tooth structure(X) group and 1mm enamel section(E) group was not significantly decreased(P＞0.05). 4. At 80sec group and 120sec, conversion rate between 1mm enamel section(E) group and 1mm enamel section + 1mm dentin section(ED1) group was not significantly decreased(P＞0.05).

• 대한치과기공학회지
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• 제32권4호
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• pp.327-335
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• 2010

Purpose: The purpose of this study was to investigate the correlation between zirconia core thickness and color tone blocking of discolored tooth and metal post. Methods: For this study, we made 20-porcelain sample and 4-metal sample( liechtenstein IPS e.max) bonded to zirconia core of different thickness with cement(Relyx ARC-3M USA)for produce discolored. We measured the color-spectral characteristics, using Shadepilot equipment(Degudent USA).We measured it with Shadepilot equipment set by automated average mode in 3 times And applied the average value obtained from 2 times of measurement in the middle of each sample. Results: As a result of analysing color-spectral characteristics on zirconia core sample, Depending on the thickness of zirconia core, the value of brightness(${\Delta}L*$:color-spectral characteristic) was increased within limited range, value of ${\Delta}a*$, ${\Delta}b*$ was decrease. Conclusion: Consequently, we obtained the following results: Changes of sample color were observed depending on the thickness of zirconia, but the range of change did not exceed the scope range of shade guide. The case of metal posts, shade guide color D2 were observed in 0.5mm of zirconia core thickness. As a result, in case of porcelain, increasing the zirconia thickness of 0.3mm or more is unnecessary for color blocking effect, in case of metal post, considering the discolored tooth, thickness of zirconia with at least 0.5mm or more is recommended.

• Journal of Periodontal and Implant Science
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• 제33권3호
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• pp.519-531
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• 2003

The aim of present investigation was to clinically measure the thickness of palatal masticatory mucosa in the hard palate as potential donor site for mucogingival surgery, to determine the relation to shape of palatal vault, form of tooth, gender, and to serve the clinical criteria t o choose the proper surgical technique. 84(mean age:25yrs) systemically and periodontally healthy volunteers participated in this study and 18 standard measurement points were defined in the hard palate, located on 3 lies which ran at different distances parallel to the gingival margin. 6 positions were designated on each of these 3 lines between the level of canine and 2nd molar and a bone sounding technique using a periodontal probe with minimal local anesthesia was utilized to assess the thickness of palatal masticatory mucosa. Student t-test was used to determine the difference in mucosal thickness between 2 groups gender, shape of palatal vault (high palatal vault vs. low palatal vault), tooth form (short-wide vs. long narrow) The result of this study were as follows: 1. Soft tissue thickness progressively increased in sites further away from the gingival margin (p<0.01). 2. Depending on position, in line a and line c the masticatory mucosal thickness increased from Ca to M2(p<0.01), but in line b the thickness increased from Ca to P2, and decreased to M1 and increased again to M2. 3. Gender did not influence the thickness of masticatory mucosa. 4. Palatal vault shape was associated with the thickness of masticatory mucosa. Thickness of low palatal vault group was thicker than high palatal group between P2 and M2 position. 5. Form of tooth did not influence the thickness of masticatory mucosa. In conclusion, palatal vault shape was associated with the thickness of masticatory mucosa. So, mucogingival surgery can be considered as a treatment modality in high palatal vault group. But, Gender and tooth form did not influence the thickness of masticatory mucosa.

• Journal of Periodontal and Implant Science
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• 제35권2호
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• pp.359-369
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• 2005

It has been suggested that morphologic characteristics of the periodontium are partly related to the shape and form of the teeth. Furthermore, the severity of symptoms of periodontal disease have been proposed to differ among these various morphologic entities or "biotypes". The purpose of the present study was to examine the relationship between the form of the crowns in the maxillary anterior tooth segment and (1) a group of morphological characteristics and (2) the thickness of the gingiva. The thickness of gingiva was measured by ultrasonic device(SDM). 100 subjects devoid of symptoms of destructive periodontal disease were examined regarding, e.g., probing depth, gingival recession, width of keratinized gingiva, thickness of the keratinized gingiva. From maxillary study cast, the width(at the apical third-CW) and the length(CL) of the crowns of the 6 anterior teeth were determined. A CW/CL-ratio was calculated for each tooth and averaged for each tooth region. The individual mean CW/CL-ratio values for the central incisors were ranked. The 10 subjects ranked highest and the 10 ranked lowest were selected as having either a long-narrow(group N) or a short-wide(group W) form of the crown of the tooth. The data for each of the examined parameters were averaged for each tooth region in each subject and mean values for subjects in groups W and N were compared using the Student t-test. Stepwise multiple regression analysis, including data from the whole sample, was performed for each tooth region with the thickness of the free gingiva as the dependent variable. The results from the analyses demonstrated that individuals with a long-narrow form of the central incisors displayed, compared to individuals with a short-wide crown, form (l) a narrow zone of keratinized gingiva, (2) a pronounced "scalloped" contour of the gingival margin. There was no significant difference between groups N and W with respect to the thickness of the keratinized gingiva. The CW/CL-ratio data revealed that a certain form of the crowns in the central incisors was accompanied by a similar form in the lateral incisors and canine tooth region. The regression analyses demonstrated that the thickness of the keratinized gingiva in central, lateral incisors and canines was significantly related to the width of the keratinized gingiva.

• 대한치과보철학회지
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• 제44권5호
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• pp.503-513
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• 2006

Statement of the problem: The cold-cured resins used in fabrication of the provisional crown and fixed partial dentures could cause pulpal damage by heat generated during exothermic polymerization reactions. Purpose: In this in vitro study investigates the how external conditions such as material of the matrix, thickness of the matrix and thickness of dentin affect the temperature of the tooth during polymerization reaction of the cold-cured resins. Material and methods : To measure the temperature of the resin, metal die was maintained to the temperature of $37^{\circ}C$ with water bath to simulate the temperature of thetooth and thermocouple was placed in the center of the metal die. Acrylic pipe was cut in height of 1, 2, 3, 6, 10 mm and placed on the metal die and mixed resin was pored in the acrylic pipe As the resin polymerized temperature was recorded with the thermometer. Temperature of the resin using matrix was recorded by using the individual tray relieved in different thickness 2, 5, 7, 10 mm. The material of the matrix was irreversible hydrocolloid impression material, vinyl polysilloxane impression material and vacuum-formed template Temperature rise of the resin using different thickness of tooth section was record ed by placing tooth section on the metal die and placing resin over the tooth section. Results : Conclusion : 1. Temperature rise increased as the thickness of the resin increased but there was no significant differences over 3 mm thickness of the resin. 2. The lowest temperature rise was showed in irreversible hydrocolloid impression material and vinyl polysilloxane impression material vacuum-formed template as in orders. 3, Temperature rise of the resin decreased regardless of the thickness of the matrix when vinyl polysilloxane impression material was used as the matrix. 4 When irreversible hydrocolloid impression material was used as matrix, the temperature rise of the resin decreased as the thickness of the matrix increased and there was no temperature rise when thickness of the matrix reached 10 mm, 5. The temperature rise of the resin did not decreased when Polypropylene vacuum-formed template was used as the matrix. 6, The temperature of the resin increased as the thickness of the dentin decreased.

• The Journal of Advanced Prosthodontics
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• 제9권6호
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• pp.416-422
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• 2017

PURPOSE. To investigate the effect of reducing tooth preparation and ceramic thickness on fracture resistance of lithium disilicate crowns. MATERIALS AND METHODS. Specimen preparation included a standard complete crown preparation of a typodont mandibular left first molar with an occlusal reduction of 2 mm, proximal/axial wall reduction of 1.5 mm, and 1.0 mm deep chamfer (Group A). Another typodont mandibular first molar was prepared with less tooth reduction: 1 mm occlusal and proximal/axial wall reduction and 0.8 mm chamfer (Group B). Twenty crowns were milled from each preparation corresponding to control group (n=5) and conditioned group of simultaneous thermal and mechanical loading in aqueous environment (n=15). All crowns were then loaded until fracture to determine the fracture load. RESULTS. The mean (SD) fracture load values (in Newton) for Group A were 2340 (83) and 2149 (649), and for Group B, 1752 (134) and 1054 (249) without and with fatigue, respectively. Reducing tooth preparation thickness significantly decreased fracture load of the crowns at baseline and after fatigue application. After fatigue, the mean fracture load statistically significantly decreased (P<.001) in Group B; however, it was not affected (P>.05) in Group A. CONCLUSION. Reducing the amount of tooth preparation by 0.5 mm on the occlusal and proximal/axial wall with a 0.8 mm chamfer significantly reduced fracture load of the restoration. Tooth reduction required for lithium disilicate crowns is a crucial factor for a long-term successful application of this all-ceramic system.