• 전기학회논문지P
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• 제51권2호
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• pp.87-93
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• 2002

Accurate acquisition of surface geometries such as machined surfaces, biological surfaces, and deformed parts have been very important technique in scientific study and engineering, especially for system design, manufacturing and inspection. Two-camera method keeps accuracy more than double than mechanical method. In this paper, a new method is studied to acquire 3D geometric data of the small object such as a die in stone model. When the devices, cameras, laser beam and object are in a perfect plane, the calculation is measured by position error 0.025[mm] within. But this paper shows that arbitrarily positioned system can also be used to obtain 3D data. Also, this paper present a method to generate coping surface data with which CAM system can do for milling work.

• 대한치과기공학회지
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• 제3권1호
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• pp.9-16
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• 1981

A comparative study was conducted to evaluate the relationship of investing medium to the amount of vertical occlusal changes and to the differences of surface smoothness during denture construction. Three groups of 20 dentures, 30 sets of upper and lower were fabricated of conventional heatcuring acrylic denture base resin, using silicone-gypsum molding techniques, with or without covering the occlusal surfaces of the teeth by artificial stone and all-gypsum molding techniques. The distance between the two reference points indented by 1/2 round bur on the upper and lower frontal surfaces of each articulator were measured and recorded before processing and again after processing and remounting of each denture on the articulator. The differences between the two recordings indicated the amount of vertical opening during denture processing. The difference of surface smoothness were investigated and determined by 3 observers continual comparing of the two randomly selected dentures with each other, which were seperately selected as pairs from the different two groups of 20. The results obtained were as follows: 1. During resin processing no statistically significant differences of the amount of vertical occlusal changes were detected between any of the two groups of two silicone-gypsum and one allgypsum molding techniques, although the amount of vertical opening was somewhat increased when silicone-gypsum molding technique was used. 2. Surface smoothness of the processed denture was makedly by increased when silicone-gypsum molding technique was used.

• 대한치과기공학회지
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• 제15권1호
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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.

• The Journal of Advanced Prosthodontics
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• 제6권4호
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• pp.253-258
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• 2014

PURPOSE. To compare marginal and internal gaps of zirconia substructure of single crowns with those of three-unit fixed dental prostheses. MATERIALS AND METHODS. Standardized Co-Cr alloy simulated second premolar and second molar abutments were fabricated and subsequently duplicated into type-III dental stone for working casts. After that, all zirconia substructures were made using $Lava^{TM}$ system. Marginal and internal gaps were measured in 2 planes (mesial-distal plane and buccal-palatal plane) at 5 locations: marginal opening (MO), chamfer area (CA), axial wall (AW), cusp tip (CT) and mid-occlusal (OA) using Replica technique. RESULTS. There were significant differences between gaps at all locations. The $mean{\pm}SD$ of marginal gap in premolar was $43.6{\pm}0.4{\mu}m$ and $46.5{\pm}0.5{\mu}m$ for single crown and 3-unit bridge substructure respectively. For molar substructure the $mean{\pm}SD$ of marginal gap was $48.5{\pm}0.4{\mu}m$ and $52.6{\pm}0.4{\mu}m$ for single crown and 3-unit bridge respectively. The largest gaps were found at the occlusal area, which was $150.5{\pm}0.5{\mu}m$ and $154.5{\pm}0.4{\mu}m$ for single and 3-unit bridge premolar substructures respectively and $146.5{\pm}0.4{\mu}m$ and $211.5{\pm}0.4{\mu}m$ for single and 3-unit bridge molar substructure respectively. CONCLUSION. Independent-samples t-test showed significant differences of gap in zirconia substructure between single crowns and three-unit bridge (P<.001). Therefore, the span length has the effect on the fit of zirconia substructure that is fabricated using CAD/CAM technique especially at the occlusal area.

• 대한치과보철학회지
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• 제31권2호
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• pp.181-190
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• 1993

The purpose of this study was to evaluate the effect of shear bond strength between various percentage of reused dental ceramic alloys and porcelain. One hundred specimens were made of one semiprecious alloy and three nonprecious alloys. Each alloy group was subdevided into five groups according to the additional precentage of new alloy. Group I specimens were made of 100% new alloy and served as the control of the investigation. Group II specimens were made of once-cast alloy with 75% new alloy. Group III specimens were made of once-cast alloy with 50% new alloy. Group IV specimens were made of once-cast alloy with 25% new alloy. Group V specimens were made of 100% recast alloy. Five specimens were made for each group of the alloy combinations. The test specimens were prepared by firing porcelain doughnuts on the alloy rod surface, and invested in dental stone. Bond strengths were measured by Instron universal testing machine at a crosshead speed of 0.5mm/min. The fractured surface of metal specimens were examined under the scanning electron microscope. The obtained results were as follows : 1. The shear bond strength of Albabond showed no significant difference between control group and reused alloy group. 2. The shear bond strength of reused alloy groups of nonprecious alloys were lower than that of control groups. 3. The shear bond strength between porcelain and metal in semiprecious alloy was higher than in nonprecious alloys 4. In nonprecious alloys. Rexillium III showed the highest bond strength value and Excelalloy showed the lowest shear bond strength value. 5. Regardless of the type of alloys and additional proportion of new alloys, scanning electron microscope photographs of the fracture surface between alloy and porcelain revealed simillar semiprecious alloy and nonprecious alloys.

• 대한치과기공학회지
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• 제39권3호
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• pp.137-143
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• 2017

Purpose: The purpose of this study is to analyze the fitness of heat - pressed ceramic laminate veneers fabricated using the additive manufacturing. Methods: Impression was replicated by using light body silicone and heavy body silicone on the custom tray, and it was fabricated using Type IV Stone. The test specimens were prepared by using a dental scanner, a laminating veneer using a dental design program, and a specimen with a 3D printer. The control specimens were prepared by the lost wax technique and heat - pressed to fabricate the specimens. The data of the specimens were measured by the RMS value of the internal fitness a using a 3-dimensional measurement program. Results: The Stereolithography laminate veneer group was measured at $78.10(4.09){\mu}m$ and the LWV group was measured at $31.50(5.10){\mu}m$. There is a significant difference between the two groups (p<0.001) Conclusion : Evaluation of fitness laminate veneers was fabricated by additive manufacturing showed the difference statistically significantly and clinically acceptable result.

• 대한치과보철학회지
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• 제54권3호
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• pp.234-238
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• 2016

목적: 최근 치과 영역에서 CAD-CAM (computer aided design-computer aided manufacturer) 시스템의 이용과 디자인 소프트웨어가 늘어남에 따라 쉽고 빠른 수복물의 디자인이 가능해졌다. 과거에는 치과 기공사의 wax up 기술의 숙련도에 따라 금관의 외형이 결정 되었으나, CAD-CAM 시스템에서는 디자인 소프트웨어에 대한 숙련도가 더 중요한 요인이 되어가고 있다. 이에 치과 기공사와 치과의사간의 결과물의 차이를 알아보고자 한다. 재료 및 방법: 대합치와 인접치가 양호한 환자의 하악 우측 제1대구치를 금관 지대치 형성 한 후 polyether로 인상채득 하였다. 인상재에 초경석고를 이용하여 모형을 제작 하였으며, Trios 구강내 스캐너를 이용하여 STL (stereolithography) 파일을 추출하였다. 3shape dental designer 상에서 5년 이상 경력의 치과 기공사 1명, 2년 이하 경력의 치과 기공사 3명, 4명의 보철과 1년차 전공의가 동일한 STL 파일을 이용하여 금관을 디자인 하였다. CAD-CAM 시스템 경력이 가장 오래된 기공사의 디자인을 기준으로 하여 치과 기공사 그룹 3명(group DT)과 1년차 전공의 그룹 4명(group RT) 의 금관 외형을 비교하였다. 디자인된 금관의 근원심폭, 협설폭, 높이, 교두간 거리, 대합치와의 접촉점의 수를 측정, 비교 하였다. 독립표본 t검정을 시행하여 그룹간의 차이를 비교하였고, 대합치와의 접촉점의 수는 Wilcoxon signed-rank test 를 이용하였다. 결과: 정규성 검정 결과 근원심폭, 협설폭, 높이, 교두간 거리는 정규분포를 보였다. Group DT와 group RT의 금관 디자인상에서 근원심폭, 협설폭, 높이, 교두간 거리에서 통계적으로 유의할만한 차이가 없었다. 대합치와의 접촉점 수는 정규분포를 보이지 않았으며, wilcoxon signed-rank test 결과 통계적으로 유의한 차이를 보이지 않았다. 결론: 금관의 외형의 크기에 있어서는 group DT와 group RT 사이에 통계학적으로 유의할만한 차이가 없었지만 수치화하기 어려운 금관의 해부학적 형태나 주변 치아와의 형태적 유사성 등은 차이가 있었다. 디자인 소프트웨어에 대한 숙련도가 높아진다면 각 술자가 가지고 있는 교합에 대한 개념을 더 구현하기 쉬울 것이다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제36권6호
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• pp.548-552
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• 2010

The submandibular gland is the second largest major salivary gland, which secretes 40% of the total daily saliva. Owing to its anatomic characteristics as well as the high viscosity and basicity of the saliva, sialolithiasis is found most commonly in the submandibular gland. Sialolithiasis that cannot be treated by conservative treatment is conventionally removed by an excision of the submandibular gland. Generally, an excision of the submandibular gland is performed via an extra-oral approach but the disadvantages of this treatment include a risk of injuring the facial nerve and scar formation. Case reports have revealed an even less invasive intraoral surgical technique for the removal of sialolith that does not affect the submandibular gland function. The functional recovery of the gland, complications and recurrence rates after surgery with this conservative intraoral procedure were all successful. We report 5 patients from the department of Oral and Maxillofacial Surgery at Dental Hospital, Yonsei University, who had undergone a resection of the sialolith though the intraoral approach with successful results.

• 대한치과보철학회지
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• 제40권3호
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• pp.236-245
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• 2002

The acrylic resin was first introduced as denture base materials in 1937 and it is commonly used for denture base fabrication nowadays. Three different curing cycles (Conventional curing cycle, short curing cycle and long curing cycle) and three commercially available heat-activated acrylic resins (Vertex RS, Lucitone 199 and ProBase Hot) were investigated to find the curing cycle and material that showed the minimum shrinkage of the resin during polymerization process. A brass master mold was fabricated and duplicated by additional silicone impression material. Stone molds were made by pouring of type III dental stone (SILKY-ROCK YELLOW, Whip-Mix, Louisville, Kentucky). It was embedded in the flask. Strain gauge and thermocouple were embedded in the specimen. Strain gauge and thermocouple were connected to signal conditioning amplifier and data was recorded by pre-programmed software. The parameters ESmax (Maximum expansion strain), Sb (Strain measured just before deflasking procedure), Sa (Strain measured just after deflasking procedure) and Sf (Strain measured at the end of the experiment) were measured. ${\Delta}$S was calculated from Sb and Sa (${\Delta}$S=Sb-Sa). In the experiment concerned about materials, the parameters 90-ESmax (Maximum expansion strain measured during early 90 minutes of curing procedure), 180-ESmax (Maximum expansion strain measured from 90 minutes to 180 minutes), Sb, Sa, ${\Delta}$S and Sf were measured and the following conclusions were made. 1. The ESmax value of conventional curing cycle showed the largest value and the 180-ESmax value of Lucitone 199 showed the smallest value. 90-ESmax values showed no significant difference (p<0.05). 2. ${\Delta}$S values of conventional curing cycle showed the positive values. ${\Delta}$S values of short curing cycle and long curing cycle showed the negative values. All three materials cured by conventional curing cycle showed the positive values. 3. The Sf values of long curing cycle and ProBase Hot (cured by conventional curing cycle) showed the smallest values.

• Imaging Science in Dentistry
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• 제50권4호
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• pp.291-298
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• 2020

Purpose: The detection and exact localization of penetrating foreign bodies are crucial for the appropriate management of patients with dentoalveolar trauma. This study compared the efficacy of cone-beam computed tomography (CBCT) and spiral computed tomography (CT) scans for the detection of different foreign bodies composed of 5 frequently encountered materials in 2 sizes. The effect of the location of the foreign bodies on their visibility was also analyzed. Materials and Methods: In this in vitro study, metal, tooth, stone, glass, and plastic particles measuring 1×1×1 mm and 2×2×2 mm were prepared. They were implanted in a sheep's head in the tongue muscle, nasal cavity, and at the interface of the mandibular cortex and soft tissue. CBCT and spiral CT scans were taken and the visibility of foreign bodies was scored by 4 skilled maxillofacial radiologists who were blinded to the location and number of foreign bodies. Results: CT and CBCT were equally accurate in visualizing metal, stone, and tooth particles of both sizes. However, CBCT was better for detecting glass particles in the periosteum. Although both imaging modalities visualized plastic particles poorly, CT was slightly better for detecting plastic particles, especially the smaller ones. Conclusion: Considering the lower patient radiation dose and cost, CBCT can be used with almost equal accuracy as CT for detecting foreign bodies of different compositions and sizes in multiple maxillofacial regions. However, CT performed better for detecting plastic particles.