• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제35권5호
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• pp.367-371
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• 2009

Purpose: The purpose of this study was to evaluate the feasibility of the outfracture osteotomy sinus graft technique with the evaluation of 5-year survival rate of the implants placed in the atrophic edentulous posterior maxillary area. Materials and methods: One hundred and thirteen cases of 96 patients who visited our center from Aug 2004 to July 2009 and were diagnosed as atrophic edentulous maxillary alveolar ridge, were selected and underwent augmentation sinus surgery with outfracture osteotomy technique. Feasibility of the outfracture osteotomy technique was investigated with clinical and radiographic evaluation to assess the survival rate of the total dental implants in augmentation sinus surgery of this new kind. Total fixture number available in follow-up period was 179, in which the lost 10 patients were excluded out of 96 patients. Results: Five-year cumulative survival rate was 97.2% with 5 failures of total 179 fixtures. The average follow-up period was 29 and a half months, with the minimum and maximum follow-up periods of 4 months 21 days and 59 months 14 days, respectively. Conclusion: Traditional infracture technique is a popular method for an augmentation sinus surgery. The authors modified this classical method by outfracturing and readapting the bony window after sinus graft, with excellent treatment results evidenced by high survival rate of 97.2% (174 out of 179 fixtures), which proves the feasibility of the newly-designed outfracture osteotomy sinus graft technique.

• The Journal of Advanced Prosthodontics
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• 제10권4호
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• pp.265-270
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• 2018

PURPOSE. The purpose of this in vitro study was to evaluate the accuracy of a new implant impression technique using bite impression coping and a dual arch tray. MATERIALS AND METHODS. Two implant fixtures were placed on maxillary left second premolar and first molar area in dentoform model. The model with two fixtures was used as the reference. The impression was divided into 2 groups, n=10 each. In group 1, heavy/light body silicone impression was made with pick up impression copings and open tray. In group 2, putty/light body silicone impression was made with bite impression copings and dual arch tray. The reference model and the master casts with implant scan bodies were scanned by a laboratory scanner. Surface tessellation language (STL) datasets from test groups was superimposed with STL dataset of reference model using inspection software. The three-dimensional deviation between the reference model and impression models was calculated and illustrated as a color-map. Data was analyzed by independent samples T-test of variance at ${\alpha}=.05$. RESULTS. The mean 3D implant deviations of pick up impression group (group 1) and dual arch impression group (group 2) were 0.029 mm and 0.034 mm, respectively. The difference in 3D deviations between groups 1 and 2 was not statistically significant (P=.075). CONCLUSION. Within limitations of this study, the accuracy of implant impression using a bite impression coping and dual arch tray is comparable to that of conventional pick-up impression.

• The Journal of Advanced Prosthodontics
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• 제10권5호
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• pp.388-394
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• 2018

PURPOSE. To measure axial displacement of different implant-abutment connection types and materials during screw tightening at the recommended torque by using a contact scanner for two-dimensional (2D) and three-dimensional (3D) analyses. MATERIALS AND METHODS. Twenty models of missing mandibular left second premolars were 3D-printed and implant fixtures were placed at the same position by using a surgical guide. External and internal fixtures were used. Three implant-abutment internal connection (INT) types and one implant-abutment external connection (EXT) type were prepared. Two of the INT types used titanium abutment and zirconia abutment; the other INT type was a customized abutment, fabricated by using a computer-controlled milling machine. The EXT type used titanium abutment. Screws were tightened at $10N{\cdot}cm$, simulating hand tightening, and then at the manufacturers' recommended torque ($30N{\cdot}cm$) 10 min later. Abutments and adjacent teeth were subsequently scanned with a contact scanner for 2D and 3D analyses using a 3D inspection software. RESULTS. Significant differences were observed in axial displacement according to the type of implant-abutment connection (P<.001). Vertical displacement of abutments was greater than overall displacement, and significant differences in vertical and overall displacement were observed among the four connection types (P<.05). CONCLUSION. Displacement according to connection type and material should be considered in choosing an implant abutment. When adjusting a prosthesis, tightening the screw at the manufacturers' recommended torque is advisable, rather than the level of hand tightening.

• Journal of the Korean Wood Science and Technology
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• 제24권2호
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• pp.7-14
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• 1996

이 연구(硏究)는 미국(美國) 남부(南部)의 9개 주(州)에 소재하고 있는 가구공장(家具工場)에 대한 설문조사(設問調査)를 통해 산업구조(産業構造)와 마케팅 전략을 조사(調査) 하였다. 이번 조사 결과를 요약하면 1. 가구공장(家具工場)이 사용하는 원자재(原資材)는 red oak, pine, poplar, maple 등으로 한국 가구공장(家具工場)이 원자재(原資材)의 95% 이상(以上)을 남양재(南洋材)에 의존하고 있는 것과 뚜렷한 차이를 보였다. 2. 가구공장(家具工場)의 68.8%는 주요시장(主要市場)을 자기 주내(州內)에 가지고 있고, 28.8%가 주(州) 밖에 그리고 조사공장(祖師工場)의 2.5%만이 수출(輸出)했다. 아울러 수출(輸出)이나 자기 주외(州外)에 시장(市場)을 가지고 있을 수록 공장규모(工場規模)가 컸다. 3. 주요시장(主要市場)까지의 거리는 50%가 160km 이내(以內)였는데 이것은 활엽수 제재목(製材木) 공장(工場)의 30%가 800km 밖에까지 시장(市場)을 가지고 있는 것에 비해 매우 좁은 시장(市場)을 형성하고 있는 것으로 나타났다. 4. 제품(製品)의 유통(流通)은 직접 소비자(消費者)에게 출하(出荷)하는 것이 3/4로 압도적이었지만, 중간유통기관에 출하(出荷)하는 곳일수록 공장규모(工場規模)도 컸다. 5. 가구산업(家具産業)의 성공에 기여(寄與)하는 요인(要因)으로는 제품품질(製品品質)과 장기적(長期的)인 소비자(消費者)와의 관계(關係) 증진(增進)을 가장 중요한 요인으로 지적하였고, 그 다음으로 기업에 대한 평판(評判)과 높은 소비자(消費者) 서비스를 지적하였다. 반면에 가구산업발전(家具産業發展)의 장애요인(障碍要因)으로는 원자재(原資材)의 품질(品質)과 원료(原料)의 불안정(不安定)한 공급(供給)이 제일 중요하게 인식되어 있었다. 그러나 해외공급자(海外供給者)와의 경쟁(競爭)은 장애요인(障碍要因)으로 거의 인식되고 있지 않았다. 6. 공장(工場)의 확장(擴張)이나 이전(移轉)에 가장 큰 영향을 미치는 요인(要因)으로는 노동력(勞動力) 문제(問題)(생산성(生産性)과 비용(費用))가 가장 중요하게 지적되었고, 그 다음으로 세금구조(稅金構造), 건설비(建設費) 등이 지적되었다.

• The Journal of Advanced Prosthodontics
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• 제8권6호
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• pp.465-471
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• 2016

PURPOSE. The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. MATERIALS AND METHODS. Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of $1.0{\times}10^6$cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. RESULTS. Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups (P>.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. CONCLUSION. Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment.

• Journal of Computational Design and Engineering
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• 제2권3호
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• pp.176-182
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• 2015

Head-and-neck cancer is often treated with intensive irradiation focused on the tumor, while delivering the minimum amount of irradiation to normal cells. Since a course of radiotherapy can take 5-6 weeks or more, the repeatability of the patient posture and the fastening method during treatment are important determinants of the success of radiotherapy. Many devices have been developed to minimize positional discrepancies, but all of the commercial devices used in clinical practice are operated manually and require customized fixtures for each patient. This is inefficient and the performance of the fixture device depends on the operator's skill. Therefore, this study developed an automated head-and-neck immobilizer that can be used during radiotherapy and evaluated the positioning reproducibility in a phantom experiment. To eliminate interference caused by the magnetic field from computed tomography hardware, Ni-Ti shape-memory alloy wires were used as the actuating elements of the fixtures. The resulting positional discrepancy was less than 5 mm for all positions, which is acceptable for radiotherapy.

• 대한치과보철학회지
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• 제29권1호
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• pp.167-213
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• 1991

The successful replacement of missing teeth has been one driving aim behind the emergence of implant dentistry as both a technology and clinical vocation for over four decades. To date, a multitude of dental implant devices had been designed and utilized in the patient population. Most of these devices have been designed without support of the engineering criteria. The long-term success of any dental implant is dependent upon the optimization of stresses which occurs during oral function and parafunction. Although many studies have examined the biologic interactions between dental implants and living tissue, few studies have been reported on the biomechanical aspects of dental implants. The purpose of this study was to analyze the stress distribution of osseointegrated prosthesis on certain conditions, such as amount of load, location of load, length of fixtures, number of fixtures used, arch shape, bone quality, etc. Three dimentional finite element analysis was used for this study. FEM models were created using commercial software(Super SAP. for IBM 16 bit AT computer. All elements were 8-node brick, isoparametric. Mandible and prosthesis was modeled with 780 elements and 1074 nodes. The results were as follows : 1. In case of cantilever extension, there was a compressive stress at the base of the first implant and a tensile stress at the base of the second implant. 2. The stresses were linearly proportional to the amount of load. 3. The stresses were linearly proportional to the length of cantilever. 4. There was a stress concentration at the neck of the implant and bone under horizontal loads.

• 구강회복응용과학지
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• 제18권4호
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• pp.301-311
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• 2002

The purpose of this study was to compare the distributing pattern of stress on the finite element models with the different vertical bone level of implant fixture. The two kinds of finite element models were designed according to vertical bone level around fixture ($4.0mm{\times}11.5mm$). The cemented crowns for mandibular first and second molars were made. Three- dimensional finite element model was created with the components of the implant and surrounding bone. Vertical loads were applied with force of 200N distributed within 0.5mm radius circle from the center of central fossa and distance 2mm and 4 mm apart from the center of central fossa. Von-Mises stresses were recorded and compared in the supporting bone, fixtures, abutment screws, and crown. The results were as following : (1) In vertical loading at the center circle of central fossa on model 1 and 2, the difference from vertical bone in implant placement did not affect the stress pattern on all components of implant except for crown. (2) With offset distance incerasing and the bone level of implant decreasing, the concentration of stress occured in the buccal side of long crown, around the buccal crestal bone, and on the fixture- abutment interface. As a conclusion, the research showed a tendency to increase the stress on the supporting bone, fixture and screw under the offset loads when the vertical level of bone around fixture was different. Since the same vertical bone bed has more benefits than the different bone bed around fixtures, it is important to prepare a same vertical level of bone bed for the success of implants under occlusal loads.

• 구강회복응용과학지
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• 제18권4호
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• pp.251-276
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• 2002

The purpose of this study was to compare and analyze the stress distribution and displacement of the fully bone anchored bridge and implant-supported overdenture in edentulous mandible on certain conditions such as number of implants, different design of superstructure. Three dimensional analysis was used and nine kinds of models designed for this study. FEM models were created using commercial software[$Rhinoceros^{(R)}$ (Ver. 1.0 Robert McNeel & Associates, USA)], and analyze using commercial software [Cosmos/$Works^{TM}$(Ver. 4.0 Structural Research & Analysis Corp., US A)]. A vertical load and $45^{\circ}$ oblique load of 17kgf were applied at the left 1st. molar. The results were as follows : (1) In the group of OVD, the displacement was reduced as increasing the number of fixture under vertical loading but there was no specific difference in Von Mises stress. Under oblique loading, the displacement was same at the vertical loading but Von Mises stress was reduced in order of OVD-3, OVD-4, OVD-2. But, bending moment reduced according to increasing the number of fixture. (2) In the group of FBAB, under vertical and oblique loading, the magnitude of Von Mises stress and displacement reduced according to increasing the number of fixtures. FBAB-4 and FBAB-5 showed similar score and distribution, but FBAB-6 showed lower value relatively. (3) In cantilever design, the maximum displacement reduced under vertical loading but increased under oblique loading. However, von mises stresses on fixtures increased under vertical and oblique loading. (4) In comparing OVD-group with FBAB-group, FBAB showed low magnitude of displacement in respect of oblique loading. However OVD-group was more stable in respect of stress distribution.

• 대한치과의사협회지
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• 제55권11호
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• pp.766-776
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• 2017

This clinical study was conducted to evaluate the clinical effects of a concave neck of external connection type implant fixture designed for platform switching on the peri-implant tissue responses. Two types of implants with different neck designs were implanted in 20 patients. For the experimental group, the bioseal(BS) implant fixtures with 's' shaped concave profile on the neck were used, and non-bioseal(NBS) implant fixtures with a straight profile on the neck were used as control(Total of 40 implants, NBS: n = 19, BS: n=21). During the one-year period after implant placement, implant survival rate, marginal bone resorption, bleeding, plaque, and complications were evaluated. The survival rate of NBS and BS group was 94.74% and 90.48%, respectively. There was no significant difference on marginal bone resorption, bleeding and plaque between the two groups (P>.05). Within the limits of the present study, implants with a concave neck design showed similar clinical results to implants with a straight neck design on the peri-implant tissue responses. Longitudinal clinical studies are necessary to confirm more effective clinical results.