• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.1
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• pp.90-94
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• 2008

The purpose of this study was to investigate the effects of immediate non-functional loading by analyzing histomorphology around the implant tissues in dogs. Five eight- to nine-month-old full-grown dogs weighing around 12 kg were used in the study. Group I (control group) comprised those in which delayed loading was applied to the right side of the mandible, and Group II (experimental group) consisted of dogs in which immediate loading was performed on the left side of the mandible. Resorbable blast media (RBM)-treated double-threaded US III implants measuring 3.5 mm in diameter and 11 mm long were used in the study. Each animal received four implants in each group, for a total of 40 implants. Cemented type abutments were used after implantation. An 8-week period was allowed for bone healing and an abutment was placed after exposing the periosteum for loading. An implant sample was obtained from bone blocks taken when the dogs were killed at 16 weeks after loading. A Mann-Whitney U-test was performed to evaluate statistical significance. Student's t-test was used for the histological evaluation. The bone formation ratio in Groups 1 and 2 was 88.23 and 86.41%, respectively. No significant difference in new bone formation was observed in the two groups. As no significant difference was seen in new bone formation between the delayed and immediate loading groups, early loading might be possible after implant placement.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.4
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• pp.414-420
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• 2006

Purpose : The purpose of this study is to use finite element analysis to predict the fatigue life of an implant system subjected to fatigue load by mastication (chewing force). The reliability and the stability of implant system can be defined in terms of the fatigue strength. Not only an implant is expensive but also it is almost impossible to correct after it is inserted. From a bio-engineering standpoint, the fatigue strength of the dental implant system must be evaluated by simulation (FEA). Material and Methods Finite element analysis and fatigue test are performed to estimate the fatigue strength of the implant system. Mesh of implant is generated with the actual shape and size. In this paper, the fatigue strength of implant system is estimated. U-fit (T. Strong, Korea, internal type). The stress field in implant is calculated by elastic-plastic finite element analysis. The equivalent fatigue stress, considering the contact and preload stretching of a screw by torque for tightening an abutment, is obtained by means of Sine's method. To evaluate the reliability of the calculated fatigue strength, fatigue test is performed. Results: A comparison of the calculated fatigue strength with experimental data showed the validity and accuracy of the proposed method. The initiation points of the fatigue failure in the implant system exist in the region of high equivalent fatigue stress values. Conclusion: The above proposed method for fatigue life estimation tan be applied to other configurations of the differently designed and improved implant. In order to prove reliability of prototype implant, fatigue test should be executed. The proposed method is economical for the prediction of fatigue life because fatigue testing, which is time consuming and precision-dependent, is not required.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.6
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• pp.440-448
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• 2012

Purpose: The purpose of this study was to evaluate marginal bone loss of the alveolar crest on implants with or without guided bone regeneration and variables that have influenced. Methods: The clinical evaluation were performed for survival rate and marginal bone loss of 161 endosseous implants installed with guided bone regeneration (GBR) in 83 patients from September 2009 to October 2010 in relation to sex and age of patients, position of implant, implant system, length and diameter of implant. Study group (n=42) implant with GBR procedure, control group (n=41) implant without GBR technique. Simultaneous GBR approach using resorbable membranes combined with autogenous bone graft or freeze-dried bone allograft or combination. Radiographic examinations were conducted at healing abutment connection and latest visit. Marginal bone level was measured. Results: Mean marginal bone loss was 0.73 mm in study group, 0.63 mm in control group. Implants in maxillary anterior area (1.21 mm) were statistically significant in study group (P<0.05), maxillary posterior area (0.81 mm) in control group (P<0.05). Mean marginal bone loss 1.47 mm for implants with diameter 3.4 mm, 0.83 mm for implants of control group with diameter 4.0 mm (P<0.05). Some graft materials showed an increased marginal bone loss but no statistically significant influence of sex, implant type or length. Conclusion: According to these findings, this study demonstrated the amount of marginal bone loss around implant has maintained a relative stable during follow-up periods. We conclude that implants with GBR had similar survival rate and crestal bone level compared with implants in native bone.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.2
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• pp.218-231
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• 2005

Statement of problem. In the partially edentulous patients, removable partial dentures have been working as a important treatment modality. Clasps, a kind of direct retainers, received some amount of stresses during the insertion and removal of partial denture on the abutment tooth. Purpose. The study is to investigate stresses of the different clasps. Material and methods. In order to investigate the degree of stresses, maxillary partial edentulism (Kennedy Class II modification I) was assumed and removable partial dentures were designed on it with three kinds of metallic materials; cobalt-chromium alloy, type IV gold alloy and commercially pure (c.p.) titanium. Aker's clasp was applied on the left second molar. RPA (mesial rest-proximal plate-Aker's) clasp was on the left first premolar and wrought wire clasp was on the right first premolar. Three dimensional, non-linear, dynamic finite element analysis method was run to solve this process. Results. 1. Cobalt-chromium alloy had the highest von Mises stress value and c.p. titanium had the lowest one irrespective of the types of clasps. 2. In the Aker's clasps, stress on the retentive tips was shown shortly after the appearance of stresses of the middle and minor connector areas. These time lag was much shorter in the RPA clasps than in the Aker's clasp. 3. In general. retentive tips of wrought wire clasps had much less amount of stress than other clasps. Conclusion. The amount of stress was the highest in the RPA clasp and the lowest in the wrought wire clasp, in general.

• The Journal of Advanced Prosthodontics
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• v.8 no.1
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• pp.21-29
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• 2016

This in vitro study investigated and compared the durability and retention of three types of attachments. MATERIALS AND METHODS. Three commercially available attachments were investigated: $Clix^{(R)}$, Dalbo-$Plus^{(R)}$ and $Locator^{(R)}$. In total, 72 samples of these attachments were placed in the acrylic resin forms and subjected to mechanical testing (5400 cycles of insertion and removal) over the respective ball or Locator abutments immersed in artificial saliva at pH 7 and $37^{\circ}C$. The abutments were placed at angulations of $0^{\circ}$, $10^{\circ}$ and $20^{\circ}$. The retention force was recorded at the beginning and after 540, 1080, 2160, 3240, 4320 and 5400 insertion-removal cycles. RESULTS. The results revealed that there were significant differences in the average values of the insertion/removal force due to angulation ($F_{(2.48)}=343619$, P<.05) and the type of attachment ($F_{(7.48)}=23.220$, P<.05). CONCLUSION. Greater angulation of the abutments was found to influence the retention capacity of the attachments, and the fatigue test simulating 5 years of denture insertion and removal did not produce wear in the metal abutments.

• Journal of the Korean Institute of Rural Architecture
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• v.12 no.1
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• pp.33-40
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• 2010

HyangGyo had been built for teaching peoples as a place of educational practice, and also for the order and stability of country through Confucianism. This study analyzed and researched the building structure of Daejeong-HyangGyo in Jeju Island In Daejeong-HyangGyo, unique architectural characteristics are shown as they have been built in an island independent from the mainland. Also up-down system was well reflected in detailed architectural styles. The main temple of Daejeong-HyangGyo was built in the type of one-Chulmok(a subsidiary material of Gongpo and a piece of wood to support the eaves) of which ancon supports a purline from the center of a pillar and two-Ikgong(a piece of wood engraved to put on an ancon), but in the case of the lecture hall, its Gongpo(a piece of wood to support the eaves) was inferior in quality. In the case of Jeju abutments were used in main temples and fire walls were mostly used. In particular, their abutments are difficult to be observed in HyangGyo in the mainland. It is presumed that the abutment and the fire wall used in Jeju Island might be the best solution to protect structures from rain and moisture. To sum up, local characteristics and traditional rules were thoroughly reflected in Dajeong-HyangGyos built in Jeju Island from the aspect of arrangement and detailed style. In conclusion, it is significant that architectural styles, not to mention the other aspects of Jeju culture, were suitably adapted to Jeju Island.

• The Journal of Advanced Prosthodontics
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• v.14 no.5
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• pp.273-284
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• 2022

PURPOSE. Computer-aided design and manufacturing (CAD-CAM) of implant abutments has been shown to result in surface contamination from site-specific milling and fabrication processes. If not removed, these contaminants can have a potentially adverse effect and may trigger inflammatory responses of the peri-implant tissues. The aim of the present study was to evaluate the bacterial disinfection and cleaning efficacy of ultrasonic reprocessing in approved disinfectants to reduce the microbial load of CAD-CAM abutments. MATERIALS AND METHODS. Four different types of custom implant abutments (total N = 32) with eight specimens in each test group (type I to IV) were CAD-CAM manufactured. In two separate contamination experiments, specimens were contaminated with heparinized sheep blood alone and with heparinized sheep blood and the test bacterium Enterococcus faecium. Abutments in the test group were processed according to a three-stage ultrasonic protocol and assessed qualitatively and quantitatively by determination of residual protein. Ultrasonicated specimens contaminated with sheep blood and E. faecium were additionally eluted and the dilutions were incubated on agar plates for seven days. The determined bacterial counts were expressed as colony-forming units (CFU). RESULTS. Ultrasonic reprocessing resulted in a substantial decrease in residual bacterial protein to less than 80 ㎍ and a reduction in microbiota of more than 7 log levels of CFU for all abutment types, exceeding the effect required for disinfection. CONCLUSION. A three-stage ultrasonic cleaning and disinfection protocol results in effective bacterial decontamination. The procedure is reproducible and complies with the standardized reprocessing and disinfection specifications for one- or two-piece CAD-CAM implant abutments.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2A
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• pp.131-143
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• 2009

Under transverse earthquake shaking, arching action of bridge structures develops along the deck between the abutments thus providing the so-called deck resistance. The magnitude of the arching action for bridge structures is dependent on the number of spans, connection condition between deck and abutment or piers, and stiffness ratio between superstructure and substructure. In order to investigate the arching action effects for inelastic seismic responses of PSC Box bridges, seismic responses evaluated by pushover analysis, capacity spectrum analysis and nonlinear time-history analysis are compared for 18 example bridge structures with two types of span numbers (short bridge, SB and long bridge, LB), three types of pier height arrangement (regular, semi-regular and irregular) and three types of connection condition between superstructure and substructure (Type A, B, C). The arching action effects (reducing inelastic displacement and increasing resistance capacity) for short bridge (SB) is more significant than those for long bridge (LB). Semi-regular and irregular bridge structures have more significant arching action than regular bridges.

• Journal of Dental Rehabilitation and Applied Science
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• v.38 no.2
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• pp.97-109
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• 2022

Purpose: This study aims to investigate the risk indicators contributing to implant failure, and analyze the relationship between risk indicators and marginal bone loss (MBL) through long-term follow-up over 3 years. Materials and Methods: From 2003 to 2017, patients' medical charts with a history of dental implant surgery at Chonnam National University Dental Hospital were reviewed retrospectively. The patient's demographic variables, and clinical variables were recorded. Periapical radiographs were used to evaluated the changes in MBL around implants. And we analyzed implant survival rates. Multiple regression analysis with backward elimination was conducted to correlate the patient's clinical variables and implant failure and Pearson correlation analysis was performed to the correlated between implant long-term survival rates and MBL and initial stability. Results: In multiple regression analysis, there was a statistically significant negative correlation between abutment connection type (β = -.189, P < .05), with or without SPT (β = -.163, P < .05), diabetes (β = -.164, P < .05), osteoporosis (β = -.211, P < .05) and MBL. Anticoagulant medication influenced the long-term success rate of implants. PTV values at the second implant surgery showed a statistically significant negative correlation with long-term implant survival (P < .05). Conclusion: For the long-term success of the implant, the appropriate abutment connection type must be selected and the periodic SPT is recommended. Systemic diseases such as diabetes and osteoporosis and anticoagulant medication should be considered. Furthermore, since high PTV at the second implant surgery correlated with the long-term survival rates of the implant, initial stability should be carefully considered before undergoing the prosthetic procedure.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.1
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• pp.120-147
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• 1994

This study was performed for the purpose of evaluating the stress distribution around threaded type implants, cylindrical type implants and teeth connected with rigid or non-rigid connector. The stress distribution around the surrounding bone was analyzed by three-dimensional photoelastic method. Twelve mandibular photoelastic epoxy resin models and a circular polariscope were used to record the isochromatic fringes. After the stress distribution around the implant and tooth was observed, the results were as follows ; 1. In threaded type implants, stress concentrated patterns were observed at the neck either vertical or 25 degree lateral force. 2. The stress concentrated patterns were observed at the tooth apical portion and neck portions of the implant and tooth when a threaded implant was connected with the tooth by either a rigid or non-rigid connector. More force was generated at the tooth neck portion by a rigid connector and more force at the implant neck portion by a non-rigid connector. 3. The stress concentrated patterns were observed at the apical portion of the implant and tooth when a cylindrical type ,implant was connected with the tooth either by a rigid or non-rigid connector. More force was generated at the tooth apical portion by a rigid connector and more force at the neck portion of the tooth and implant by a non-rigid connector. 4. The stress around the tooth was more equally distributed in a threaded type implant than in a cylindrical implant when the tooth was connected with either a rigid or non-rigid connector. 5. The stress around a threaded type implant was progressively more equally distributed in the following order : 1) when used a single implant, 2) a non-rigid connection with the implant and tooth, 3) a rigid connection with the implant and tooth, 4) a rigid connection with two implant fixtures.