• Journal of Periodontal and Implant Science
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• v.36 no.2
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• pp.531-554
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• 2006

Oral implants must fulfill certain criteria arising from special demands of function, which include biocompatibility, adequate mechanical strength, optimum soft and hard tissue integration, and transmission of functional forces to bone within physiological limits. And one of the critical elements influencing the long-term uncompromise functioning of oral implants is load distribution at the implant- bone interface, Factors that affect the load transfer at the bone-implant interface include the type of loading, material properties of the implant and prosthesis, implant geometry, surface structure, quality and quantity of the surrounding bone, and nature of the bone-implant interface. To understand the biomechanical behavior of dental implants, validation of stress and strain measurements is required. The finite element analysis (FEA) has been applied to the dental implant field to predict stress distribution patterns in the implant-bone interface by comparison of various implant designs. This method offers the advantage of solving complex structural problems by dividing them into smaller and simpler interrelated sections by using mathematical techniques. The purpose of this study was to evaluate the stresses induced around the implants in bone using FEA, A 3D FEA computer software (SOLIDWORKS 2004, DASSO SYSTEM, France) was used for the analysis of clinical simulations. Two types (external and internal) of implants of 4.1 mm diameter, 12.0 mm length were buried in 4 types of bone modeled. Vertical and oblique forces of lOON were applied on the center of the abutment, and the values of von Mises equivalent stress at the implant-bone interface were computed. The results showed that von Mises stresses at the marginal. bone were higher under oblique load than under vertical load, and the stresses were higher at the lingual marginal bone than at the buccal marginal bone under oblique load. Under vertical and oblique load, the stress in type I, II, III bone was found to be the highest at the marginal bone and the lowest at the bone around apical portions of implant. Higher stresses occurred at the top of the crestal region and lower stresses occurred near the tip of the implant with greater thickness of the cortical shell while high stresses surrounded the fixture apex for type N. The stresses in the crestal region were higher in Model 2 than in Model 1, the stresses near the tip of the implant were higher in Model 1 than Model 2, and Model 2 showed more effective stress distribution than Model.

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.4
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• pp.338-344
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• 2016

Implant supported removable partial denture (ISRPD) using the implants enables favorable rehabilitation by complementing biomechanical limitations of the conventional removable partial denture (RPD). However, continuous recall check is necessary for evaluation of the mechanical and biological complications to ensure good long-term prognosis of ISRPD. This clinical report describes the complication and management in patient of Kennedy class I edentulism with ISRPD using healing abutment. The wear and fracture of healing abutment occurred at 36 months after delivery. So, healing abutment was replaced by connecting $Locator^{(R)}$ abutment for altering into the implant retained partial overdenture.

• Journal of Biomedical Engineering Research
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• v.25 no.6
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• pp.531-536
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• 2004

In fracture treatment with external fixators, the inter-fragmentary movements at the fracture site affect the fracture healing process, and these movements are highly related to the stiffness of external fixation systems. Therefore, in order to provide the optimal fracture healing at the fracture site, it is essential to understand the relationship between the stiffness and the system configurations in external fixation system. In this study we investigated the influences of system configuration parameters on the stiffness in the finite element analysis of an external fixation system of a long bone. The system alignment, the geometric and the material non-linearity of the pin, the joint stiffness and the callus formation were considered in the finite element model. In the first, the system stiffness of the developed finite element model was compared with the experiment data for model validation. The consideration of the joint stiffness and nonlinearity of the model improved the system stiffness results. The joint stiffness, the non-alignment of the system decreased the system stiffness while the callus formation increased the system stiffness. The present results provided the biomechanical basis of rational guidelines for design improvements of external fixators and pre-op. planning to maximize the system stiffness in fracture surgery.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.3
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• pp.517-534
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• 1997

It has been held that excessive mechanical forces to the osseous and soft tissues of the TMJ result in joint dysfunction. Understanding the stress pattern on TMJ is very important in TMJ research. But, it is very difficult to measure directly the biomechanical stress distribution in the TMJ when the mandible is loaded. Therefore, stress distribution in the TMJ during functional movement was studied through animal experiment or mathematical model. It was observed and compared the stress distribution occuring in the working and balancing condyle when lower right canine, lower right first molar and lower right second molar were clenched by the three dimensional finite element analysis. Also, stress distribution in the working and balancing condyles were observed and compared when $20^{\circ}$ forward and buccal bite forces were applied to the first molar. The results were as follows : 1. Stress distribution in the condyles during unilateral clenching of the first molar, second molar, canine showed no difference. In the working condyle, tensile force was concentrated on the lateral aspect of the condylar articular surface and condylar neck. And compressive force was concentrated on the anteromedial and lateral aspect of condyle. In the balancing condyle, tensile and compressive forces were concentrated on the lateral aspect of the condylar articular surface and stress transmission to the temporal bone was not observed. 2. When lateral forces were applied to the first molar, tensile forces were concentrated on the medial aspect of the condylar neck and condylar posterior surface in working and balancing condyle. Compressive force was concentrated on the anteromedial and lateral surface of the condyle and stress transmission to the temporal bone was not observed. 3. During unilateral clenching, stress in the working condyle decreased as the occlusal load moved posteriorly while the stress in the balancing condyle increased. when lateral force was applied to first molar, the incremental amount of stress was greater than vertical load. 4. During unilateral clenching, the average balancing/working condyle stress ratio was 2.52. There was a greater concentration of stress in the balancing condyle. The ratio increased as the occlusal load moved posteriorly and decreased considerably when lateral forces were applied to the first molar.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.4
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• pp.260-269
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• 2019

The prolonged neglect of the posterior teeth missing area may cause mesial drift, extrusion, unexpected movement of the adjacent teeth and alveolar bone loss with occlusion collapse. Therefore it is recommended to treat that area by the prosthesis as soon as possible after tooth missing. However, if orthodontic treatment is applied to move the remained teeth, it can create improved biomechanical dentoalveolar environment. The use of the third molars in teeth missing area provides advantages as optimizing of prosthesis size. However, crown shape, location, soundness of the third molar and possible of eruption failure should be considered. In this case report, two patients closed a second teeth missing site and reduced the size of the first and second teeth missing area for an implant by protraction of impacted third molars. This case reports the considerations for closing or reducing the posterior teeth space with protracting the third molars by comparing two patients.

• Clinics in Shoulder and Elbow
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• v.10 no.2
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• pp.220-226
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• 2007

Purpose: The distal clavicle has a biomechanical structure different from that of the proximal or middle 1/3 clavicle, and delayed union or nonunion occurs frequently in a distal clavicle fracture. The authors obtained favorable results from an open reduction and bone grafting of the distal clavicle nonunion. We report the results together with review of the relevant literature. Materials and Methods: The subjects were 8 patients(average age, 38.9) who had undergone surgery for distal clavicle nonunion from August 2003 to May 2006. Nonunion occurred after surgical treatment in 4 cases, and after conservative treatment in the other 4. In all cases, the patients complained of pain. Results: The mean follow-up duration was 14 months, and radiological union was observed in 8 weeks on average. In all cases, the range of shoulder joint motion was normal at the end of the follow-up observation. In the functional evaluation, 7 cases showed excellent results and 1 case showed good results. Conclusion: Surgical treatment is a safe and reliable treatment for distal clavicle fracture nonunion because it can achieve early rehabilitation and union.

• Journal of Korean Orthopaedic Sports Medicine
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• v.1 no.1
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• pp.55-60
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• 2002

Purpose : To assess the change in the number of mechanoreceptors of posterior cruciate ligament(PCL) after transecting posterior cruciate ligament of the rabbit. Materials and Methods : We selected 10 skeletally-matured New Zealand white rabbits and one of the two posterior cruciate ligaments was transected and the other underwent sham-operation on each rabbit. Afterward, PCLs with synovium were obtained at femoral attach area in both knees in 20 weeks postoperatively, but in one of the cases, the transected PCL did not heal and had to be excluded from this study. Consequently, histologic examination of the ligament for the remaining 9 cases was done after being prepared with modified gold chloride stain. Results : The study showed a little bit more decrease in the number of mechanoreceptors in the transected group compared with that in the sham-operated group, but the number was statistically negligible. Conclusions : It is considered that the knee joint with injured PCL may still maintain proprioception since the decrease in the number of mechanoreceptors is not considerable, but further study on biomechanical role and function of mechanoreceptor of healed PCL is required.

• Korean Journal of Applied Biomechanics
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• v.20 no.4
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• pp.469-477
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• 2010

The purpose of this study was to evaluate the effects of insole-equipped ankle-foot-orthoses (AFO) on gait. 10 healthy males who had no history of injury in the lower extremity participated in this study as the subjects. The foot of each subject was first scanned, and the insole fit to the plantar was made using BDI-PCO(Pedcad Gmbh, Germany). The subject then was made to walk on a treadmill under four experimental conditions: 1) normal walking, 2) walking wearing AFO, 3) walking wearing AFO equipped with the insole, 4) walking wearing pneumatic-ankle-foot-orthosis (pAFO) equipped with the insole. During walking, foot pressure data such as maximum force, contacting area, peak pressure, and mean pressure was collected using Pedar-X system (Novel Gmbh, Germany) and EMG activity of lower limb muscles such as gastrocnemius medial head, gastrocnemius lateral head, and soleus was recorded using MP150 EMG module (BIOPAC System Inc., USA). Collected data was then analyzed using paired t-test in order to investigate the effects of the insole. As a result of the analysis, when insole was equipped, overall contacting area was increased while both the highest peak pressure and the mean pressure were significantly decreased, and EMG activity of the lower limb muscles was decreased. On the contrary, the cases of wearing AFO showed the decreased contacting area and the increased pressures. Therefore, the AFO equipped with a proper insole fit well to the foot can help comfortable walking by spreading the pressure over the entire plantar.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.3952-3958
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• 2011

This study was to investigate the difference in gait pattern between the visual handicap children and non handicap children in by analyze the biomechanical variation and pattern of lower limb. Therefore, we have made a choice of four visually handicapped children and two subjects, who had no medical disorder for the last six months. In order to collect the gait pattern data of each group, we have used six infrared cameras and one forceplate Also, we have used QTM program to collect the raw data and Visual3D program to calculate kinetic variable. The results were as follows, An/Posterior GRF of breaking phase and propulsion phase in stance phase was lower in visual handicapped children than that of non handicapped children and breaking phase was longer than propulsion phase. extension moment at the ankle was quite lower than general gait pattern and there was little variation at the knee joint which makes the results differ from the general gait pattern. However, hip joint moment was relatively higher than that of other joints. Mechanical variation of lower limb, in case of foot and shank, showed similar results. but generated very low mechanical energy. In thigh, the form of mechanical energy generation was slightly different in each group but generated more mechanical energy than other segments.

• Journal of Korean Neurosurgical Society
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• v.60 no.5
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• pp.498-503
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• 2017

Objective : The purpose of the present study was to compare inter-fragmentary compression pressures after fixation of a simulated type II odontoid fracture with the headless compression Herbert screw and a half threaded cannulated lag screw. Methods : We compared inter-fragmentary compression pressures between 40- and 45-mm long 4.5-mm Herbert screws (n=8 and n=9, respectively) and 40- and 45-mm long 4.0-mm cannulated lag screws (n=7 and n=10, respectively) after insertion into rigid polyurethane foam test blocks (Sawbones, Vashon, WA, USA). A washer load cell was placed between the two segments of test blocks to measure the compression force. Because the total length of each foam block was 42 mm, the 40-mm screws were embedded in the cancellous foam, while the 45-mm screws penetrated the denser cortical foam at the bottom. This enabled us to compare inter-fragmentary compression pressures as they are affected by the penetration of the apical dens tip by the screws. Results : The mean compression pressures of the 40- and 45-mm long cannulated lag screws were $50.48{\pm}1.20N$ and $53.88{\pm}1.02N$, respectively, which was not statistically significant (p=0.0551). The mean compression pressures of the 40-mm long Herbert screw was $52.82{\pm}2.17N$, and was not statistically significant compared with the 40-mm long cannulated lag screw (p=0.3679). However, 45-mm Herbert screw had significantly higher mean compression pressure ($60.68{\pm}2.03N$) than both the 45-mm cannulated lag screw and the 40-mm Herbert screw (p=0.0049 and p=0.0246, respectively). Conclusion : Our results showed that inter-fragmentary compression pressures of the Herbert screw were significantly increased when the screw tip penetrated the opposite dens cortical foam. This can support the generally recommended surgical technique that, in order to facilitate maximal reduction of the fracture gap using anterior odontoid screws, it is essential to penetrate the apical dens tip with the screw.