• The Journal of Advanced Prosthodontics
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• 제8권5호
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• pp.388-395
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• 2016

PURPOSE. The purpose of this study was to evaluate the resistance to deformation under static overloading by measuring yield and fracture strength, and to analyze the failure characteristics of implant assemblies made of different titanium grades and connections. MATERIALS AND METHODS. Six groups of implant assemblies were fabricated according to ISO 14801 (n=10). These consisted of the combinations of 3 platform connections (external, internal, and morse tapered) and 2 materials (titanium grade 2 and titanium grade 4). Yield strength and fracture strength were evaluated with a computer-controlled Universal Testing Machine, and failed implant assemblies were classified and analyzed by optical microscopy. The data were analyzed using the One-way analysis of variance (ANOVA) and Student's t-test with the level of significance at P=.05. RESULTS. The group $IT4_S$ had the significantly highest values and group IT2 the lowest, for both yield strength and fracture strength. Groups $IT4_N$ and ET4 had similar yield and fracture strengths despite having different connection designs. Group MT2 and group IT2 had significant differences in yield and fracture strength although they were made by the same material as titanium grade 2. The implant system of the similar fixture-abutment interfaces and the same materials showed the similar characteristics of deformation. CONCLUSION. A longer internal connection and titanium grade 4 of the implant system is advantageous for static overloading condition. However, it is not only the connection design that affects the stability. The strength of the titanium grade as material is also important since it affects the implant stability. When using the implant system made of titanium grade 2, a larger diameter fixture should be selected in order to provide enough strength to withstand overloading.

• 구강회복응용과학지
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• 제25권3호
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• pp.255-265
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• 2009

즉시 하중에 대한 관심과 시도가 증가되고 있지만, 명확한 술식이 정립되어 있지는 않다. 본 연구에서는 상악 전치부 임플란트에서 즉시 하중시에 골과 임플란트에 나타나는 응력분포 양상을 3차원 유한요소법을 이용하여 알아보고자 하였다. 골질이 D3인 상악 전치부의 골모형을 구성하고, 서로 다른 길이(8.5 mm, 10.0 mm, 11.5 mm, 13.0 mm, 15.0 mm)의 직경 4.0 mm 나사형 임플란트를 식립한 모형을 제작하였다. 해석 절차의 간소화를 위하여 모든 물성은 등방성, 선형탄성, 균질성으로 가정하였다. 골-임플란트 계면은 접촉 요소법으로 처리하여 골유착이 일어나기 전 상태로 구성하였다. 지대주 장축에 120도의 각도로 지대주의 구개 절단각 중앙부에 176 N의 정하중을 가하고 응력분포를 관찰하였다. von Mises stress를 이용하여 응력을 분석한 결과 모든 모형에서 순측 피질골에 응력이 집중되었으며 피질골과 망상골의 경계부에서 최대 응력값을 나타내었다. 길이에 따른 비교시 8.5 mm 모형에서 가장 큰 최대 응력값을 나타냈으며, 임플란트 길이가 증가될수록 좀 더 양호한 응력 분포를 나타내었다. 상악 전치부 즉시 하중시에 피질골의 존재 유무는 매우 중요하며, 길이가 긴 임플란트를 식립하는 것이 유리하며, 가능하면 13.0 mm 이상의 임플란트를 식립하는 것이 즉시하중을 시행할 때 응력 분산에 유리한 것으로 판단된다.

• 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.

• 대한치과보철학회지
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• 제45권3호
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• pp.389-400
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• 2007

Statement of problem. Use of the conventional dental impression procedure is problematic in patients who have difficulty opening their mouth, difficulty breathing through their nose or tendency to gag. Purpose. It is necessary to make individual trays more comfortable for patients during impression taking procedure. It was reported at the KAP Annual Meeting 2001 Seoul that an improved impression technique was suitable for this purpose. In this study, the accuracy of the improved dental impression method for implant was compared with the conventional dental impression method. Material and methods. An oral simulator was made from clear acrylic resin block which had similar form of edentulous ridge. For setting up the standard, five fixtures were installed on it. Study casts were made using two kinds of impression techniques. One was the conventional method that was taken using silicone impression material and an individual resin tray under connection of inter-fixture relation. The other was the improved method in which was the connection of the impression coping and the thermoformed polymethyl methacrylate tray. In addition, two different study casts were made from the improved impression body. The coordinates of the fixture on the study model were measured by three-dimensional coordinate measuring equipment. Then the distances between each fixture were calculated and compared with that of oral simulator. Accuracy of the each impression method was also assessed. Results. The differences of inter-fixture dimension between study casts and simulator in the improved impression technique showed $0.014{\pm}0.016mm$ and $0.017{\pm}0.022mm$, respectively and that of the conventional method was $0.017{\pm}0.014mm$. There was no significant difference between the improved impression technique and conventional method. Conclusion. The improved impression technique is useful for multiple support implants.

• 대한치과보철학회지
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• 제45권4호
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• pp.506-521
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• 2007

Statement of problem: The cumulative success rate of wide implant is still controversial. Some previous reports have shown high success rate, and some other reports shown high failure rate. Purpose: The aim of this study was to analyze, and compare the biomechanics in wide implant system embeded in different width of crestal bone under different occlusal forces by finite element approach. Material and methods: Three-dimensional finite element models were created based on tracing of CT image of second premolar section of mandible with one implant embedded. One standard model (6mm-crestal bone width, 4.0mm implant diameter central position) was created. Varied crestal dimension(4, 6, 8 mm), different diameter of implants(3.3, 4.0, 5.5, 6.0mm), and buccal position implant models were generated. A 100-N vertical(L1) and 30 degree oblique load from lingual(L2) and buccal(L3) direction were applied to the occlusal surface of the crown. The analysis was performed for each load by means of the ANSYS V.9.0 program. Conclusion: 1. In all cases, maximum equivalent stress that applied $30^{\circ}$ oblique load around the alveolar bone crest was larger than that of the vertical load. Especially the equivalent stress that loaded obliquely in buccal side was larger. 2. In study of implant fixture diameter, stress around alveolar bone was decreased with the increase of implant diameter. In the vertical load, as the diameter of implant increased the equivalent stress decreased, but equivalent stress increased in case of the wide implant that have a little cortical bone in the buccal side. In the lateral oblique loading condition, the diameter of implant increased the equivalent stress decreased, but in the buccal oblique load, there was not significant difference between the 5.5mm and 6.0mm as the wide diameter implant. 3. In study of alveolar bone width, equivalent stress was decreased with the increase of alveolar bone width. In the vertical and oblique loading condition, the width of alveolar bone increased 6.0mm the equivalent stress decreased. But in the oblique loading condition, there was not a difference equivalent stress at more than 6.0mm of alveolar bone width. 4. In study of insertion position of implant fixture, even though the insertion position of implant fixture move there was not a difference equivalent stress, but in the case of little cortical bone in the buccal side, value of the equivalent stress was most unfavorable. 5. In all cases, it showed high stress around the top of fixture that contact cortical bone, but there was not a portion on the bottom of fixture that concentrate highly stress and play the role of stress dispersion. These results demonstrated that obtaining the more contact from the bucco-lingual cortical bone by installing wide diameter implant plays an important role in biomechanics.

• The Journal of Advanced Prosthodontics
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• 제14권4호
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• pp.236-249
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• 2022

PURPOSE. The present study compared the accuracy between digital and conventional implant impressions. MATERIALS AND METHODS. The experimental models were divided into six groups depending on the implant location and the scanning span. Digital impressions were captured using the intraoral optical scanner TRIOS (3Shape, Copenhagen, Denmark). Conventional impressions were taken with the monophase impression material based on addition-cured silicones, Honigum-Mono (DMG, Hamburg, Germany). A high-precision laboratory scanner D900 (3Shape, Copenhagen, Denmark) was used to obtain digital data of resin models and stone casts. Surface tessellation language (STL) datasets from scanner were imported into the analysis software Geomagic Qualify 14 (3D Systems, Rock Hill, SC, USA), and scan body deviations were determined through two-dimensional and three-dimensional analyses. Each scan body was measured five times. The Sidak t test was used to analyze the experimental data. RESULTS. Implant position and scanning distance affected the impression accuracy. For a unilateral arch implant and the mandible models with two implants, no significant difference was observed in the accuracy between the digital and conventional implant impressions on scan bodies; however, the corresponding differences for trans-arch implants and mandible with six implants were extremely significant (P<.001). CONCLUSION. For short-span scanning, the accuracy of digital and conventional implant impressions did not differ significantly. For long-span scanning, the precision of digital impressions was significantly inferior to that of the traditional impressions.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제38권
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• pp.16.1-16.9
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• 2016

Background: The association of biomaterial combined with repair factor-like platelet-rich plasma (PRP) has prospective values. Bovine-derived xenograft has been identified as an osteoconductive and biocompatible grafting material that provides osseointegration ability. PRP has become a valuable adjunctive agent to promote healing in a lot of dental and oral surgery procedures. However, there are controversies with respect to the regenerative capacity of PRP and the real benefits of its use in bone grafts. The purpose of this study was to assess the influence of PRP combined with xenograft for the repair of peri-implant bone defects. Methods: Twelve rabbits were used in this study, and the experimental surgery with implant installation was performed simultaneously. Autologous PRP was prepared before the surgical procedure. An intrabony defect (7.0 mm in diameter and 3.0 mm deep) was created in the tibia of each rabbit; then, 24 titanium dental implants (3.0 mm in diameter and 8.5 mm long) were inserted into these osteotomy sites. Thus, a standardized gap (4.0 mm) was established between the surrounding bony walls and the implant surface. The gaps were treated with either xenograft alone (control group) or xenograft combined with PRP (experimental group). After healing for 1, 2, 3, 4, 5, and 6 weeks, the rabbits were sacrificed with an overdose of KCl solution. Two rabbits were killed at each time, and the samples including dental implants and surrounding bone were collected and processed for histological analysis. Results: More newly formed bone and a better bone healing process were observed in control group. The histomorphometric analysis revealed that the mean percentage of bone-to-implant contact in the control group was significantly higher than that of the experimental group (25.23 vs. 8.16 %; P < 0.05, independent-simple t test, analysis of variance [ANOVA]). Conclusions: The results indicate that in the addition of PRP to bovine-derived xenograft in the repair of bone defects around the implant, PRP may delay peri-implant bone healing.

• 구강회복응용과학지
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• 제25권2호
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• pp.139-155
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• 2009

연구목적: 원추형(Superline) 임플란트를 발치와에 1회법으로 즉시 식립한 후 주변 조직의 생물학적 안정성을 관찰하는 것이다. 연구 방법: 치근부에 명백한 병적 소견이 있는 경우는 제외한 기타 치아의 발치와에 원추형 임플란트를 즉시 식립한다. 1회법을 식립한 후 임플란트 주변 연조직의 치유를 도모한다. 수술 후 32주에 획득한 표준화된 방사선상에서, 임플란트 주변골의 변화(depth of the distance from the implant shoulder (IS) and from the alveolar crest (AC) to the bottom of the defect (BD)) 등을 관찰했다. 결과 : 13명의 피검자 (남자 10명/ 여자 3명)를 선별하여 15개의 원추형 임플란트를 발치와에 즉시 식힙하였으며 모든 임플란트의 초기 고정은 양호했다. 평균 수술시간은 $41{\pm}10.0$분이었다. 모든 임플란트survival rate 는100% 였다. Mean ISQ values 는 상대적으로 안정했으며, 술 후 32주까지 계속 관찰에, 임플란트 인접 치조골 감소량은 $1.69{\pm}1.2mm$ (mesial), $1.65{\pm}1.2mm$ (distal) 로 나타났다. FMPS, FMBS, PPD와 각 은의 폭의 유의한 변화는 없었다. 결론: 파절이나, 근관치료의 실패 등의 이유로 해서 치아를 발치할 경우 치근형 (Superline)임플란트를 발칭하에 1회법으로 즉시 식립하는 술식은 임상적으로 예지성있는 치료법으로 판단된다.

• 대한치과보철학회지
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• 제45권6호
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• pp.760-768
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• 2007

Statement of problem. Conventional denture treatment for totally edentulous patients is associated with a variety of functional and psychosocial problems. The placement of implants in the anterior region of the maxilla and mandible and the fabrication of an implant-retained overdenture might solve these problems. Purpose. This study compared the marginal bone loss around the implant and evaluated the implant survival rate and complications in patients treated with overdentures retained by implants for 2 years. Material and methods. Patients who had received implant-retained overdentures using a Dolder bar at Samsung Medical Center from January 1999 to June 2005 and had participated in the annual recall programs for two years were selected for this study. A total of 18 patients and 56 $Br{\aa}ne-mark\;system^{(R)}$ implants were used, and their data were reviewed. Evaluations of the survival rate, bone quality, marginal bone loss, and complications were performed. The data on the Dolder bar length and clip length were measured. The change in marginal bone loss and the correlation between the marginal bone loss and bar length, clip length, or bone quality were investigated. Results. Implants placed in this study showed a 100% survival rate. The average annual bone loss was 1.12mm in the first year and 0.27mm in the second year in the maxilla, and 0.58mm in the first year and 0.22mm in the second year in the mandible. The marginal bone loss in the maxilla showed no significant association with those in the mandible. (P>.05). There was no significant difference in marginal bone loss around implants between the first and second year. (P>.05) There was no statistically significant relationship (P>.05) between the marginal bone loss and bone quality, clip length, or Dolder bar length. The Dolder bar length showed a high correlation with the clip length. (P<.05) Various complications were noted. Conclusion. These results confirmed the favorable outcome for patients treated with implant-retained overdentures.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제35권4호
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• pp.221-226
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• 2013

Purpose: This study is to evaluate the efficacy of the autogenous tooth bone graft material, clinically and radiologically, as related to implant installation. Methods: In oral and maxillofacial surgery department of Ajou University Hospital, guided bone regeneration (GBR), implant placement combined with GBR, sinus graft, implant placement combined with sinus graft, and defect filling were performed in 46 patients, using autogenous tooth bone. Among these, 66 implants were inserted with autogenous tooth bone. Implant stability quotient (ISQ) was measured by Osstell Mentor (Integration Diagnostics, Goteborg, Sweden) on 39 implants on the operation date and 4 months later, and on 21 implants 9months on the average at the final setting of restoration. Twenty-eight implants with GBR and sinus graft (GBR group: n=14, sinus graft group: n=14) were evaluated radiologically to measure the resorption of grafted autogenous tooth bone after loading. Results: The average initial stabilization of the installed implants was 67 ISQ, and the average secondary stabilization at 4 months later was 76. The average bone loss of GBR group as measured 8.0 months after application of prosthesis loading was 0.29 mm and the average bone loss of the sinus graft group as measured 7.6 months after application of prosthesis loading was 0.66 mm, respectively. In the histological assessment, formation of the new bone and continuous trabecular bone pattern was identified around autogenous tooth bone. Conclusion: Based on these results, we concluded that autogenous tooth bone is an excellent bone graft material that can substitute the autogenous bone.