• 대한치과보철학회지
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• 제61권1호
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• pp.1-17
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• 2023

목적: 본 연구의 목적은 레이져 신터링, 컴퓨터 밀링, 주조의 세 가지 방법으로 제작된 비귀금속 합금 코핑의 변연 형태에 따른 변연 적합도의 변화를 관찰하는 데 있다. 재료 및 방법: 서로 다른 두 개의 변연 형태를 정확히 재현하기 위해 3D Computer-aided Design을 이용하여 지대치 삭제의 원칙에 따라 지대치를 디자인한 다음, 티타늄 블럭을 컴퓨터 밀링하여 주모델을 제작하였다. 각각의 모델에 대하여 위의 3가지 제작 방식으로 비귀금속 합금 코핑을 12개씩 제작하여, 총 72개의 코핑을 제작하였다. 각 코핑은 지대치에 적합시켜서 공초점 레이저 주사 현미경으로 근심, 협측, 원심, 설측 변연의 변연 적합도를 150배율로 측정하였다. 결과: 레이져 신터링으로 제작한 코핑의 평균 변연 오차는 deep chamfer margin에서 11.8 ± 7.4 ㎛, rounded shoulder margin에서 6.3 ± 3.5 ㎛ 였고, 그 차이는 통계적으로 유의했다 (P < .0001). 컴퓨터 밀링으로 제작한 그룹에서는 deep chamfer margin에서 53.9 ± 27.8 ㎛, rounded shoulder margin에서 48.6 ± 30.0 ㎛였고, 변연 형태에 따른 유의한 차이가 없었다 (P = .279). 주조 방법으로 제작한 그룹은 deep chamfer margin에서 18.8 ± 20.2 ㎛, rounded shoulder margin 에서 30 ± 20.5 ㎛ 였고, 그 차이는 통계적으로 유의했다 (P = .0004). 결론: 이번 실험을 통하여, 다음과 같은 결론을 얻었다. 1. 변연의 형태에 따른 변연 적합도는 레이져 신터링이나 주조 방법으로 제작된 금속 코핑의 경우 변연 형태에 따라 유의한 차이가 있었다. 2. 레이져 신터링으로 제작한 금속 코핑에서 rounded shoulder margin이 deep chamfer margin보다 우수한 변연 적합도를 보였다. 3. 주조 방법으로 제작한 금속 코핑의 경우는 deep chamfer margin이 rounded shoulder margin보다 우수한 변연 적합도를 보였다. 4. 제작 방식에 따른 코핑의 변연 적합도는 레이져 신터링이 가장 양호하였고, 그 다음 주조 방법과 밀링 방법 순으로 변연 적합도 양호하였다. 이번 연구를 통해, 지대치의 변연 형태에 따른 금속 코핑의 변연 적합도의 변화를 관찰하였으며, 레이져 신터링으로 제작하거나 디지털 밀링한 왁스 패턴을 캐스팅한 경우에는 상관 관계가 있음을 확인하였다. 임상에 적용함에 있어 지대치의 변연 형태를 고려하여 제작 방식을 결정하는 것이 추천된다.

• 대한소아치과학회지
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• 제43권1호
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• pp.60-69
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• 2016

영구 전치의 복합 치관-치근 파절은 심미적, 기능적 문제 뿐 아니라 심리적 문제도 발생시킨다. 그러므로 파절에 대한 치료는 매우 중요하며, 여러 분야에 걸친 종합적 치료가 요구된다. 본 증례는 두 환자에서의 외상으로 인한 상악 전치의 복합 치관-치근 파절에 대한 임상적 치료 과정을 서술하였다. 근관치료와 근첨형성술이 각 환자에게 시행되었으며, 파절선을 치은 상방으로 노출시키고 생물학적 폭경을 재확립하기 위해 교정적 정출을 시행하였다. 이후 유지기간을 두었고, 그 기간 동안 치아에 임시수복을 시행하였다. 최종적으로 CAD/CAM을 이용한 세라믹 크라운 수복을 시행하였다. 이후 정기 검진 때에도 해당 치아들은 만족스러운 기능적, 심미적 결과를 보였으며, 두 환자 모두에서 재발은 나타나지 않았다. 치주조직 또한 건강한 상태를 보였다.

• 대한심미치과학회지
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• 제25권2호
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• pp.79-87
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• 2016

당일수복 보철물 제작을 위해 디지털 프로세스 사용은 필수적이다. 이러한 디지털 프로세스는 구강스캔, 컴퓨터를 이용한 보철물을 디자인 과정(CAD)과 보철물을 가공하는 과정(CAM)을 포함한다. 지르코니아의 굴곡강도는 900Mpa로 리튬디실리케이트의 400MPa보다 더 단단하지만, 리튬디실리케이트를 이용한 보철물 기공시간이 지르코니아와 비교하여 더 짧기에 당일수복 보철물 제작시 리튬디실리케이트 사용이 선호되었다. 하지만, TZI C 와 LUXEN Enamel 와 같은 새로운 소재의 지르코니아가 출시되고, 새로운 소결방식이 개발되어 지르코니아 기공시간을 단축시킬수 있게 되었고, 높은 투명도의 풀지르코니아 크라운을 짧은 시간 안에 제작할 수 있게 되었다. 이러한 발전은 당일 풀지르코니아 보철수복을 현실로 이끌고 있다.

• The Journal of Advanced Prosthodontics
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• 제10권4호
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• pp.300-307
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• 2018

PURPOSE. To investigate the fatigue and fracture resistance of computer-aided design and computer-aided manufacturing (CAD/CAM) ceramic molar crowns on dental implants and human teeth. MATERIALS AND METHODS. Molar crowns (n=48; n=8/group) were fabricated of a lithium-disilicate-strengthened lithium aluminosilicate glass ceramic (N). Surfaces were polished (P) or glazed (G). Crowns were tested on human teeth (T) and implant-abutment analogues (I) simulating a chairside (C, crown bonded to abutment) or labside (L, screw channel) procedure for implant groups. Polished/glazed lithium disilicate (E) crowns (n=16) served as reference. Combined thermal cycling and mechanical loading (TC: $3000{\times}5^{\circ}C/3000{\times}55^{\circ}C$; ML: $1.2{\time}10^6$ cycles, 50 N) with antagonistic human molars (groups T) and steatite spheres (groups I) was performed under a chewing simulator. TCML crowns were then analyzed for failures (optical microscopy, SEM) and fracture force was determined. Data were statistically analyzed (Kolmogorow-Smirnov, one-way-ANOVA, post-hoc Bonferroni, ${\alpha}=.05$). RESULTS. All crowns survived TCML and showed small traces of wear. In human teeth groups, fracture forces of N crowns varied between $1214{\pm}293N$ (NPT) and $1324{\pm}498N$ (NGT), differing significantly ($P{\leq}.003$) from the polished reference EPT ($2044{\pm}302N$). Fracture forces in implant groups varied between $934{\pm}154N$ (NGI_L) and $1782{\pm}153N$ (NPI_C), providing higher values for the respective chairside crowns. Differences between polishing and glazing were not significant ($P{\geq}.066$) between crowns of identical materials and abutment support. CONCLUSION. Fracture resistance was influenced by the ceramic material, and partly by the tooth or implant situation and the clinical procedure (chairside/labside). Type of surface finish (polishing/glazing) had no significant influence. Clinical survival of the new glass ceramic may be comparable to lithium disilicate.

• The Journal of Advanced Prosthodontics
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• 제12권4호
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• pp.189-196
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• 2020

PURPOSE. The aim of the present study was to investigate the effects of surface treatments on the bond strengths between polymer-containing restorative materials and two dual-cure resin cements. MATERIALS AND METHODS. In the present study, rectangular samples prepared from Lava Ultimate (LU) and Vita Enamic (VE) blocks were used. The specimen surfaces were treated using CoJet sandblasting, 50 ㎛ Al₂O₃ sandblasting, % 9 HF (hydrofluoric) acid, ER,Cr:YSGG laser treatment, and Z-Prime. Dual-cure resin cements (TheraCem and 3M RelyX U 200) were applied on each specimen's treated surface. A micro-tensile device was used to evaluate shear bond strength. Statistical analysis was performed using the SAS 9.4v3. RESULTS. While the bond strength using TheraCem with LU or VE was not statistically significant (P=.164), the bond strength using U200 with VE was statistically significant (P=.006). In the TheraCem applied VE groups, Z-Prime and HF acid were statistically different from CoJet, Laser, and Sandblast groups. In comparison of TheraCem used LU group, there was a statistically significant difference between HF acid and other surface treatments. CONCLUSION. The bonding performance between the restorative materials and cements were material type-dependent and surface treatment had a large effect on the bond strength. Within the limitations of the study, the use of both U200 and TheraCem may be suggested if Z-prime was applied to intaglio surfaces of VE. The cementation of LU using TheraCem is suitable after HF acid conditioning of the restoration surfaces.

• The Journal of Advanced Prosthodontics
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• 제11권1호
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• pp.55-64
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• 2019

PURPOSE. The accuracy of denture bases was compared among injection molding, milling, and rapid prototyping (RP) fabricating method. MATERIALS AND METHODS. The maxillary edentulous master cast was fabricated and round shaped four notches were formed. The cast was duplicated to ten casts and scanned. In the injection molding method, designed denture bases were milled from a wax block and fabricated using SR Ivocap injection system. Denture bases were milled from a pre-polymerized block in the milling method. In the RP method, denture bases were printed and post-cured. The intaglio surface of the base was scanned and surface matching software was used to measure inaccuracy. Measurements were performed between four notches and two points in the mid-palatal suture to evaluate inaccuracy. The palatine rugae resolution was evaluated. One-way analysis of variance was used for statistical analysis at ${\alpha}=.05$. RESULTS. No statistically significant differences in distances among four notches (P>.05). The accuracy of the injection molding method was lower than those of the other methods in two points of the mid-palatal suture significantly (P<.05). The degree of palatine rugae resolution was significantly higher in the injection molding method than that in other methods (P<.05). CONCLUSION. The overall accuracy of the denture base is higher in milling and RP method than the injection molding method. The degree of fine reproducibility is higher in the injection molding method than the milling or RP method.

• 대한치과교정학회지
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• 제53권1호
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• pp.45-53
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• 2023

Objective: This study aimed to evaluate the shear bond strength (SBS) of orthodontic brackets bonded to three-dimensionally (3D)-printed materials after various surface treatments and artificial aging compared with that bonded to computer-aided design/computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA)-milled materials. Methods: Eighty cylindrical specimens were 3D printed and divided into the following four subgroups (n = 20 each) according to the surface treatment and artificial aging procedure. Group A, sandblasted with 50 ㎛ aluminum oxide particles (SA) and aging; group B, sandblasted with 30 ㎛ silica-coated alumina particles (CO) and aging; group C, SA without aging; and group D, CO without aging. For the control group, 20 CAD-CAM PMMA-milled cylindrical specimens were sandblasted with SA and aged. The SBS was measured using a universal testing machine (0.25 mm/min), examined at ×2.5 magnification for failure mode classification, and statistically analyzed (p = 0.05). Results: The retention obtained with the 3D-printed materials (groups A-D) was higher than that obtained with the PMMA-milled materials (control group). However, no significant difference was found between the study and control groups, except for group C (SA without aging), which showed significantly higher retention than the control group (PMMA-SA and thermocycling) (p = 0.037). Study groups A-D predominantly exhibited a cohesive specimen mode, indicating specimen fracture. Conclusions: Orthodontic brackets bonded to 3D-printed materials exhibit acceptable bonding strengths. However, 3D-printed materials are prone to cohesive failure, which may result in crown fractures.

• 대한치과기공학회지
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• 제45권4호
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• pp.118-123
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• 2023

Purpose: This study proposes measures needed to implement a job-based national practical exam for dental technicians. Methods: For this study, a survey was conducted targeting 244 currently employed individuals. The current national practical test for dental technicians was divided into directions for the job-based practical test, subjects that need improvement among the current practical test subjects, items that need to be reflected in the practical test evaluation for each subject, and subjects that need to be added to the practical test. It comprised ten questions (Cronbach's α=0.801). Results: The following results were obtained. Satisfaction with the current practical test was lower than average. Future improvement should focus on job-based evaluation. The dental ceramic lab technology subject needs to be reorganized urgently, and the tasks that require evaluation for each subject are different. Moreover, if evaluation subjects are added in the future, the introduction of assessment for dental CAD/CAM (computer-aided design/computer-aided manufacturing) subjects was found to be the most urgent. Conclusion: In this study, the most necessary tasks of the current national practical examination for dental technicians were evaluated and the content needed for future reorganization was investigated. Future tests should be expanded to evaluate critical job areas. Furthermore, it is necessary to open new courses in fields such as CAD/CAM, as they are in high demand in the workplace.

• 대한치과보철학회지
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• 제60권4호
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• pp.313-319
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• 2022

총의치는 무치악 환자의 치료에 있어 가장 기본적인 치료방법 중 하나이다. 전통적인 총의치의 제작과정은 예비인상 채득, 최종 인상 채득, 악간관계 채득, 납의치 시적, 의치 장착의 단계를 거치게 된다. 여러 번의 내원 과정과 복잡한 기공 과정이 필요하며, 각 단계별로 오차가 발생할 수 있다. 최근 디지털 기술이 발전함에 따라 총의치 치료과정에도 디지털 기술이 도입되고 있으며, CAD를 이용해 더 정밀한 작업이 가능하며 기공 시간을 단축시키는 것을 물론 환자의 내원 횟수도 줄일 수 있다. 본 증례에서는 디지털 방식을 활용하여 환자의 기존 의치의 전치 배열을 최종 의치로 이행하였다. 3D 프린터를 이용해 시적 의치를 제작하여 환자에게 시적하여 구순 지지도와 전치부 배열을 포함한 심미성 및 구강내 유지력을 평가 후 최종 의치 제작하였다. Computer-Aided Design/Computer-Aided Manufacturing 기술을 활용하여 내원 횟수를 줄이는 동시에, 만족할 만한 의치의 유지력 및 안정성을 얻었으며 심미적인 회복을 이루었기에 본 증례를 보고하고자 한다.

• 대한산업공학회지
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• 제17권1호
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• pp.37-49
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• 1991

This report describes an integrated approach to sculptured surface design and manufacture, and a software package for it on a multi-axis NC milling machine. The integrated software consists of four parts : (1) surface fitting procedure for generating the characteristic polyhedron from 3 dimensional CMM data, (2) surface description for generating the mathematical representation of sculptured surfaces. (3) tool path generation for approximating the surface representation into a sequence of linear cutter paths, and (4) tool control for generating the corresponding joint variable values. This integrated approach is generally applicable to sculptured surface manufacturing where multi-axis milling machines are necessary to produce smooth three-dimensional surfaces.