SPHERICAL CAPS IN A CONVEX CONE

엄태관 충청수학회 2013 충청수학회지 Vol.26 No.3

We show that a compact embedded hypersurface with constant ratio of mean curvature functions in a convex cone C ⊂ Rn+1 is part of a hypersphere if it has a point where all the principal curvatures are positive and if it is perpendicular to C.

임플란트 지대주나사의 조임회전력이 연결부 안정성에 미치는 영향에 관한 3차원 유한요소해석 연구

엄태관,서승우,전계록,신정욱,정창모,Eom, Tae-Gwan,Suh, Seung-Woo,Jeon, Gyeo-Rok,Shin, Jung-Wook,Jeong, Chang-Mo 대한치과보철학회 2009 대한치과보철학회지 Vol.47 No.2

Statement of problem: Loosening or fracture of the abutment screw is one of the common problems related to the dental implant. Generally, in order to make the screw joint stable, the preload generated by tightening torque needs to be increased within the elastic limit of the screw. However, additional tensile forces can produce the plastic deformation of abutment screw when functional loads are superimposed on preload stresses, and they can elicit loosening or fracture of the abutment screw. Therefore, it is necessary to find the optimum tightening torque that maximizes a fatigue life and simultaneously offer a reasonable degree of protection against loosening. Purpose: The purpose of this study was to present the influence of tightening torque on the implant-abutment screw joint stability with the 3 dimensional finite element analysis. Material and methods: In this study, the finite element model of the implant system with external butt joint connection was designed and verified by comparison with additional theoretical and experimental results. Four different amount of tightening torques(10, 20, 30 and 40 Ncm) and the external loading(250 N, $30^{\circ}$) were applied to the model, and the equivalent stress distributions and the gap distances were calculated according to each tightening torque and the result was analyzed. Results: Within the limitation of this study, the following results were drawn; 1) There was the proportional relation between the tightening torque and the preload. 2) In case of applying only the tightening torque, the maximum stress was found at the screw neck. 3) The maximum stress was also shown at the screw neck under the external loading condition. However in case of applying 10 Ncm tightening torque, it was found at the undersurface of the screw head. 4) The joint opening was observed under the external loading in case of applying 10 Ncm and 20 Ncm of tightening torque. 5) When the tightening torque was applied at 40 Ncm, under the external loading the maximum stress exceeded the allowable stress value of the titanium alloy. Conclusion: Implant abutment screw must have a proper tightening torque that will be able to maintain joint stability of fixture and abutment. 연구목적: 임플란트 치료에서 흔히 발생하는 기계적인 문제점을 하나가 지대주나사의 풀림과 파절이다. 일반적으로 나사 연결의 안정성을 위해서는 지대주나사의 조임회전력에 의한 전하중을 나사의 탄성한계까지 증가시킬 필요가 있다. 그러나 저작운동에 의한 기능부하는 전하중이 가해진 지대주나사에 추가적인 인장력을 가하게 되어 나사의 풀림이나 파절의 가능성을 높인다. 이러한 풀림이나 파절을 방지하면서 동시에 최대의 결합 강도를 가지는 조임회전력을 찾는 연구가 필요하다. 본 연구는 지대주나사의 조임회전력이 임플란트-지대주 연결부 안정성에 미치는 영향을 3차원 유한요소 분석을 통하여 확인하고자했다. 연구 재료 및 방법: External butt joint를 가진 임플란트를 기반으로 3차원 유한요소 해석모형을 설계하였다. 조임회전력에 따른 지대주나사의 전하중을 이론치, 실험치 및 해석치를 비교하여 해석모형을 검증하였다. 검증한 해석모형에서 대해 조임회전력을 10 Ncm, 20 Ncm, 30 Ncm, 그리고 40 Ncm로 각각 적용하고 지대주에 30도 경사지게 250 N의 외부하중을 가하여 유산요소 해석을 실시하였다. 그 결과를 통해 지대주나사의 최대 등가응력을 계산하고 고정체와 지대주 연결부의 응력분포 및 이개거리(gap distance)를 산출하였다. 결과 및 결론: 본 연구조건 하에서 다음과 같은 결과를 얻었다. 1. 전하중은 조임회전력이 클수록 증가하였다. 2. 조임회전력 적용 후 최대 등가응력은 지대주나사 경부에서 발생하였으며, 나사산 체결부에서는 주로 경부쪽 네 개의 나사산에 응력이 집중되었다. 3. 외부하중을 가했을 때에도 조임회전력을 적용했을 때와 동일하게 최대 등가응력은 주로 지대주나사 경부에서 발생하였으나, 10 Ncm의 조임회전력을 적용한 경우에서는 지대주나사 두부밑면에서 발생하였다. 4. 외부하중을 가했을 때 10 Ncm와 20 Ncm의 조임회전력을 적용한 경우에서는 연결부 이개(joint opening) 현상이 관찰 되었다. 5. 조임회전력이 40 Ncm인 경우에는 경사하중에 의해 지대주나사의 경부에 발생하는 최대등가응력이 나사의 소재인 티타늄 합금의 허용응력을 초과하였다. 이상의 결과로 볼 때, 조임회전력은 고정체와 지대주 연결부의 안정성에 영향을 미치는 것이 확인되었다. 임플란트 지대주나사는 임상에서 발생하는 기능 하중을 고려하여 고정체와 지대주 연결의 안정성을 유지할 수 있는 적정 조임회전력의 크기가 제안되어야 한다.

유한요소분석을 통한 치과용 임플란트의 길이와 잔존 식립 깊이에 따른 임플란트 및 치조골의 영향 연구

엄태관,서승우,김명덕,김영균,김석규 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.4

수산화인회석 코팅 임프란트의 골치유과정에 관한 실험적 연구

엄태관(Tae-Gwan Eom),김종화(Jong-Hwa Kim),조인희(In-Hee Cho),정창모(Chang-Mo Jeong),조용석(Yong-Seok Cho),김영균(Young-Kyun Kim) 대한구강악안면외과학회 2011 대한구강악안면외과학회지 Vol.37 No.4

Introduction: Hydroxyapatite(HA) coating implant can accelerate osseointegration, however, there are many controversies. Materials and Methods: This study examined the early osseointegration of two types of hydroxyapatite coated implants. Twelve adult male miniature pigs (Medi Kinetics Micropigs, Medi Kinetics Co., Ltd., Busan, Korea) were used in this study. In the implants placed in the mandible, a histomorphometric evaluation was performed to evaluate the bone-implant contact (BIC) ratio. Results: The BIC ratio increased with time. TS III HA and Zimmer HA were not significantly different (P>0.05). At 8 weeks, the BIC of Zimmer HA was higher than TS III HA, but there was no significant difference (P>0.05). Conclusion: HA coated implants will accelerate early osseointegration.

디지털 융합 인공치아 치료지원 시스템 개발

김명덕,엄태관,이인재,강석진,배승배,박강 (사)한국CDE학회 2013 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2013 No.8

The Reidemeister Number and the Extended Jiang Condition

Chung, In-Jae,Ahn, Soo-Youp,Eum, Tae-Koan 건국대학교 교육연구소 1996 論文集 Vol.20 No.-

변연골 흡수가 내측연결 임플란트 매식체의 응력분포에 미치는 영향

윤미정,윤민철,엄태관,허중보,정창모 대한치과보철학회 2012 대한치과보철학회지 Vol.50 No.2

Purpose: The change of the marginal bone around dental implants have significance not only for the functional maintenance but also for the esthetic success of the implant. The purpose of this study was to investigate the load transfer of internal conical joint type implant according to marginal bone resorption by using the three-dimensional finite element analysis model. Materials and methods: The internal conical joint type system was selected as an experimental model. Finite element models of bone/implant/prosthesis complex were constructed. A load of 300 N was applied vertically beside 3 mm of implant axis. Results: The pattern of stress distribution according to marginal bone resorption was similar. The maximum equivalent stress of implant was increase according to marginal bone resorption and the largest maximum equivalent stress was shown at model of 1 mm marginal bone resorption. Although marginal bone loss more than 1mm was occurred increasing of stress, the width of the stress increase was decreasing. Conclusion: According to these results, the exposure of thin neck portion of internal conical joint type implant is most important factor in stress increasing. 연구 목적: 지금까지 성공적인 임플란트 치료를 위해 많은 연구가 진행되어 왔으며, 임플란트 주변 골 흡수 현상에 대한 연구는 매우 관심이 높은 분야 중 하나이다. 이에 본 연구에서는 삼차원 유한요소응력분석을 이용하여 변연골 흡수가 내측연결 임플란트 매식체의 기계적 안정성에 미치는 영향을 간접적으로 확인하고자 하였다. 연구 재료 및 방법: 악골에 식립된 내측연결 형태의 임플란트 매식체에 티타늄 소재의 임플란트 지대주를 지대주 나사로 연결하고 상부에 금합금관을 장착하는 삼차원 유한요소모형을 설계하였다. 0, 1, 2, 3 mm의 변연골 흡수 상태를 적용하고, 교합면 중심에서부터 3 mm 편측에 300 N의 수직 하중을 가하여 임플란트 매식체에 발생하는 최대 주응력을 계산하였다. 결과: 유한요소분석결과 변연골 흡수에 따른 임플란트 매식체의 최대 주응력 분포는 유사한 양상을 보였으며, 임플란트 매식체 상단에서 가장 높은 응력 집중이 나타났다. 최대 주응력은 처음 1 mm 변연골 흡수를 가정하였을 때 가장 크게 증가하였고, 이후 변연골 흡수가 증가할수록 응력은 증가하였지만 응력 증가의 폭은 감소하는 경향을 보였다. 결론: 이러한 결과로부터 내측연결 임플란트에서 매식체 두께가 얇은 경부의 노출은 변연골 흡수로 인한 응력 증가에 가장 큰 원인임을 알 수 있었으며, 매식체의 변형, 균열 및 파절 등의 기계적 실패를 감소시키기 위해서는 이에 대한 외과적, 보철적 고려가 필요할 것으로 생각된다.

양극산화 후 알칼리 처리한 티타늄 표면특성에 관한 연구

김명덕,신지원,김인애,박수아,엄태관,신정욱 한국생체재료학회 2007 생체재료학회지 Vol.11 No.4

The purpose of this study is to evaluate reactions of the MG-63 cells to the changes of the surface characteristics resulting from the alkali treatment on the anodic oxidized titanium (Grade 3) surface. For this study, the groups were classified into three as follows. 1) Group 1: blasted surface with hydroxyapatite powders whose diameters were ranged between 300~600 m. 2) Group 2: anodic oxidized surface in electrolyte of 0.25 M H2SO4 and H3PO4 at 300V and 0.09 A/cm2. 3) Group 3: treated surface in the same way as those in Group 2 followed by alkali treatment of 2 M NaOH for 24 hrs at 60oC . The porous layers were observed in Group 2 while nano-sized radial type cilia structures were observed in Group 3 through the SEM. The measurements of surface roughnesses showed that Group 1 has higher average values of Ra (arithmetical mean deviation of the profile) than the other groups. The Contact angle was measured least in Group 3 (8.1 ± 1.3o). Reactions of MG-63 cells to each group were also evaluated for 4 hrs, 3, 7 and up to 10 days. The results of the DNA contents showed a significant increase of the cell proliferation for all groups with time, and the increases were observable in Group 3. ALP activities were decreased significantly in all groups with time, while the decrease was reduced after 7 days. Significantly more calcium were produced in Group 3 compared to other groups. In this study, alkali treatment of the anodic oxidized titanium surface resulted in ‘the fine nano-sized radial type cilia structures on the porous, micro-sized oxide layer’. From all the data obtained through this study, this nano-sized structure has a potential of promoting the osseointegration in dental implant. However, further studies with animals and histological evaluation about these results are recommended.

Elemental Analysis of the Surface Residues on Dental Implants

김태일,최규옥,김재호,엄태관,변태희 한국생체재료학회 2003 생체재료학회지 Vol.7 No.4

Titanium has been widely used for the raw materials of various biomaterial and biomechanical applications, especially in the dental and orthopedic fields due to the surface cleanness “as delivered state”. To facilitate the osseointegration process and to obtain long-term stability, dental implants are usually subjected to certain types of surface treatments after manufactured with pure titanium. Those surface treatment processes often result in contamination of the implant surface with various elements. In this report, 60 implant samples from 7 different dental implant systems were analyzed to identify elements of surface contaminants by X-ray photoelectron spectroscopy (XPS) and to determine relative amount of residual elements on the surface of each implant system. Analytical data indicates that the majorities of the elemental contamination are the organic carbon and trace amounts of N, Ca, P, Cl, S, Na and Si. Relative amount and identity of the surface residual elements were sensitively varied by the manufacturing process and surface treatment conditions. Analytical methods developed in this study can be applied as one of analytical procedures for the quality control and safety assessment of the dental implants.

백서 두개골 결손에서 rhBMP-2와 다양한 carrier의 골재생 유도효과

이서경,김지선,강은정,엄태관,김창성,조규성,채중규,김종관,최성호,Lee, Seo-Kyoung,Kim, Ji-Sun,Kang, Eun-Jung,Eum, Tae-Kwan,Kim, Chang-Sung,Cho, Kyoo-Sung,Chai, Jung-Kiu,Kim, Chong-Kwan,Choi, Seong-Ho 대한치주과학회 2008 Journal of Periodontal & Implant Science Vol.38 No.2

Purpose: Bone morphogenetic protein (BMP) is a potent differentiating agent for cells of the osteoblastic lineage. It has been used in the oral cavity under a variety of indications and with different carriers. However, the optimal carrier for each indication is not known. This study evaluated the bone regenerative effect of rhBMP-2 delivered with different carrier systems. Materials and Methods: 8 mm critical-sized rat calvarial defects were used in 60 male Sprague-Dawley rats. The animals were divided into 6 groups containing 10 animals each. Two groups were controls that had no treatment and absorbable collagen membrane only. 4 groups were experimentals that contained rhBMP-2 only and applied with absorbable collagen sponge($Collatape^{(R)}$), $MBCP^{(R)}$, Bio-$Oss^{(R)}$ each. The histological and histometric parameters were used to evaluate the defects after 2- or 8-week healing period. The shape and total augmented area were stable in all groups over the healing time. Results: New bone formation was significantly greater in the rhBMP-2 with carrier group than control group. rhBMP-2/ACS was the highest in bone density but gained less new bone area than rhBMP-2/$MBCP^{(R)}$ and rhBMP-2/Bio-$Oss^{(R)}$. The bone density after 8 weeks was greater than that after 2 weeks in all groups. However, rhBMP-2 alone failed to show the statistically significant difference in new bone area and bone density compared to control group. Also $MBCP^{(R)}$ and Bio-$Oss^{(R)}$ particles remained after 8 weeks healing period. Conclusion: These results suggest that rhBMP-2 with carrier system is an excellent inductive agent for bone formation and we can use it as the predictable bone tissue engieering technique. Future study will likely focus on the kinetics of BMP release and development of carriers that is ideal for it.