• The korean journal of orthodontics
• /
• v.38 no.6
• /
• pp.376-387
• /
• 2008

Objective: The purpose of this study was to compare the three dimensional changes of tooth movement using four different types of maxillary molar distalization appliances; pendulum appliance (PD), mini-implant supported pendulum appliance (MPD), stainless steel open coil spring (SP) and mini-implant supported stainless steel open coil spring (MSP). Methods: These experiments were performed using the Calorific $machine^{(R)}$ which can simulate dynamic tooth movement. Computed tomography (CT) images of the experimental model were taken before and after tooth movement in 1 mm thicknesses and reconstructed into a three dimensional model using V-works $4.0^{TM}$. These reconstructed images were superimposed using Rapidform $2004^{TM}$ and the direction and amount of tooth movement were measured. Results: The mean reciprocal anchor loss ratio at the first premolar was 17 - 19% for the PD and SP groups. The appliances using mini-implants (MPD or MSP) resulted in less anchorage loss (7 - 8%). On application of a pendulum appliance or MPD, distalization was obtained by tipping rather than by bodily movement. Furthermore, the maxillary second molar tipped distally and bucally. But on application of MSP, distalization was achieved almost by bodily movement. Conclusions: Regarding tooth movement patterns during molar distalization, stainless steel open coil spring with indirect skeletal anchorage was relatively superior to other methods.

• The Journal of Korean Academy of Prosthodontics
• /
• v.47 no.2
• /
• pp.222-231
• /
• 2009

Statements of the problem: Over the past decades, conventional complete dentures were used for various patients although they have incomplete function. Overdentures using dental implants could help the improvement of denture function. Purpose: The purpose of this study was to compare the strains of abutment and bone on implant overdenture between splinted and unsplinted type of prosthesis. Additionally, the strain values of parallel placed implant model and unparallel placed implant model were compared. Material and methods: Two acrylic resin model were prepared and two implants were placed at the canine positions in each model. In the first model, two implant were placed parallel. In the second model, two implants were placed with 10 degree labiolingual divergence. Two types of abutment were connected to the fixtures alternatively. One was splint type of Hader bar, the other was unsplint type of ball abutment. Overdentures were fabricated with corresponding attachment systems and seated on abutments. Strains of abutments and labial bone simulants were measured with electric resistance strain gauges when static load from 100 N to 200 N were applied to overdentures. Results: 1. Splinted type of overdentures using bar and clip showed higher absolute strain values. But the strain was compressive and the load was shared by two implants(P<.05). 2. Unsplinted type overdentures using ball and O-ring showed low absolute strain values(P<.05). 3. Labially inclined implant showed higher tensile strain values in unsplinted type of prosthesis than in splinted type of prosthesis. Lingually inclined implant showed rather low strain values under load(P<.05). 4. Non parallel implant model showed higher absolute strain values than parallel placed implant model comprehensively(P<.05).

• The Journal of Korean Academy of Prosthodontics
• /
• v.58 no.4
• /
• pp.342-348
• /
• 2020

Anatomical changes in the facial and alveolar bones occur after multiple teeth are extracted. In the maxilla, the alveolar bone is absorbed in the direction and inclination of the root, and the remaining alveolar bone becomes shorter, reducing the diameter of the arch. In addition, as the nasolabial angle increases, the support of the lips and the aesthetics of the face are lost. This case reports a functional and aesthetically satisfactory results of full mouth rehabilitation with the implant-supported fixed prosthesis using a zirconia framework.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.35 no.3
• /
• pp.132-142
• /
• 2019

Purpose: The purpose of this finite element analysis study is to introduce the novel Lock screw system and analyze its mechanical property to see if it can prevent abutment screw loosening. Materials and Methods: The Lock screw is a component tightened on the inside of the implant abutment which applies compressive force to the abutment screw head. To investigate the effect, modeling was done using CAD program and it was analyzed by finite element analysis under various load conditions. First, the preload was measured according to the tightening torque of the abutment screw then it was compared with the theoretical value to verify the analytical model. The validated analytical model was then divided into those with no external load and those with 178 N, and the tightening torque of the lock screw was changed to 10, 20, 30 Ncm respectively to examine the property of stress distribution on the implant components. Results: Using Lock screw under various loading conditions did not produce equivalent stresses beyond the yield strength of the implant components. In addition, the axial load was increased at the abutment-abutment screw interface. Conclusion: The use of Lock screw does not exert excessive stress on the implant components and may increase the frictional force between the abutment-abutment screw interface, thus it is considered to prevent loosening of the abutment screw.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.26 no.2
• /
• pp.121-143
• /
• 2010

To investigate the effect of implant types and bone resorption on the fracture characteristics. 4 types of Osstem$^{(R)}$Implant were chosen and classified into external parallel, internal parallel, external taper, internal taper groups. Finite elements analysis was conducted with ANSYS Multi Physics software. Fatigue fracture test was performed by connecting the mold to the dynamic load fatigue testing machine with maximum load of 600N and minimum load of 60N. The entire fatigue test was performed with frequency of 14Hz and fractured specimens were observed with Hitachi S-3000 H scanning electron microscope. The results were as follows: 1. In the fatigue test of 2 mm exposed implants group, Tapered type and external connected type had higher fatigue life. 2. In the fatigue test of 4 mm exposed implants group, Parallel type and external connected types had higher fatigue life. 3. The fracture patterns of all 4 mm exposed implant system appeared transversely near the dead space of the fixture. With a exposing level of 2 mm, all internally connected implant systems were fractured transversely at the platform of fixture facing the abutment. but externally connected ones were fractured at the fillet of abutment body and hexa of fixture or near the dead space of the fixture. 4. Many fatigue striations were observed near the crack initiation and propagation sites. The cleavage with facet or dimple fractures appeared at the final fracture sites. 5. Effective stress of buccal site with compressive stress is higher than that of lingual site with tensile stress, and effective stress acting on the fixture is higher than that of the abutment screw. Also, maximum effective stress acting on the parallel type fixtures is higher. It is careful to use the internal type implant system in posterior area.

• The Journal of the Korean dental association
• /
• v.58 no.9
• /
• pp.583-589
• /
• 2020

If the implant is planted in the wrong position or direction, it is disadvantageous for stress distribution, and it is easy to cause complications such as screw loosening, abutment fracture, and implant fracture. If the position or orientation of the implant is not good, efforts should be made to minimize the problem through proper implant prosthetic treatment. In this article, the prosthetic method for facilitating future maintenance in cases with poor implant placement or orientation will be presented.

• The Journal of Korean Academy of Prosthodontics
• /
• v.53 no.2
• /
• pp.120-127
• /
• 2015

Purpose: The aim was to investigate the effect of implant thread designs on the stress dissipation of the implant. Materials and methods: The threads evaluated in this study included the V-shaped, buttress, reverse buttress, and square-shaped threads, which were of the same size (depth). Building four different implant/bone complexes each consisting of an implant with one of the 4 different threads on its cylindrical body ($4.1mm{\times}10mm$), a force of 100 N was applied onto the top of implant abutment at $30^{\circ}$ with the implant axis. In order to simulate different osseointegration stages at the implant/bone interfaces, a nonlinear contact condition was used to simulate immature osseointegration and a bonding condition for mature osseointegration states. Results: Stress distribution pattern around the implant differed depending on the osseointegration states. Stress levels as well as the differences in the stress between the analysis models (with different threads) were higher in the case of the immature osseointegration state. Both the stress levels and the differences between analysis models became lower at the completely osseointegrated state. Stress dissipation characteristics of the V-shape thread was in the middle of the four threads in both the immature and mature states of osseointegration. These results indicated that implant thread design may have biomechanical impact on the implant bed bone until the osseointegration process has been finished. Conclusion: The stress dissipation characteristics of V-shape thread was in the middle of the four threads in both the immature and mature states of osseointegration.

• The korean journal of orthodontics
• /
• v.39 no.4
• /
• pp.257-272
• /
• 2009

This case report describes the treatment of an adult patient with a Class I canine and molar relationship but a convex profile with a retrognathic mandible and marked lip protrusion, as well as an excessive lower anterior facial height and reduced transverse width on both arches due to a nasal airway obstruction. The constricted arches were expanded by surgically-assisted rapid palatal expansion and the application of a Schwarz appliance to the maxilla and mandible. Acceptable facial balance was obtained using contemporary directional force technology with microimplant anchorage (MIA), which provided horizontal and vertical anchorage in the maxillary and mandibular posterior teeth, as well as intrusion and torque control in the maxillary anterior teeth, resulting in a favorable counterclockwise mandibular response. The total treatment period was 29 months and the results were acceptable for 13 months after debonding.

• Journal of the Korean Academy of Esthetic Dentistry
• /
• v.29 no.1
• /
• pp.54-61
• /
• 2020

Forced orthodontic eruption(FOE) is a non-surgical treatment approach that allows augmenting both soft- and hard-tissue profiles of potential implant sites, by forced orthodontic extrusion of "hopeless" teeth and their periodontal apparatus. By stretching the gingival and periodontal ligament fibers during extrusion, tension is imparted to the entire alveolar socket, stimulating osseous apposition at the alveolar crest. FOE increases the width of the attached gingiva, and the mucogingival junction remains stable when the gingival margin migrates coronally. Based on these effects, FOE of non-restorable teeth prior to implant placement is a viable alternative to conventional surgical augmentative procedures in implant site development. The aim of this case report is to describes coronal soft-tissue augmentation around fractured teeth, which was achieved by FOE before implant placement.

• Proceedings of the Korea Contents Association Conference
• /
• 2011.05a
• /
• pp.267-268
• /
• 2011

본 연구에서는 유한요소 해석 방법을 이용하여 경추 유한요소 모델을 개발하고, 척추 인공디스크 수술 후 경추 분절의 생체역학적 특성을 평가하였다. 반구속 및 비구속 개념의 인공디스크가 삽입된 경추 유한요소 모델의 제 7 경추체를 완전히 고정시키고 추적 경로 방향의 50 N의 압축력을 가한 상태에서 1 Nm의 굴곡과 신전, 측면 굴곡, 비틀림 모멘트를 가하였다. 모든 방향의 하중 조건에서 인공디스크가 삽입된 경추 모델들의 회전량이 정상 경추 모델의 회전량에 비하여 크게 나타났다. 또한 인공디스크를 삽입한 운동 분절에서 정상에 비하여 후관절의 접촉력과 여섯 가지 주요 인대에 걸리는 응력이 높게 나타났다. 본 연구의 결과는 척추 인공디스크 수술 시 수술 방법의 선택뿐만 아니라 새로운 경추 수술용 임플란트 개발을 위한 인체정보 콘텐츠를 구축하는데 유용하게 활용될 수 있을 것으로 기대된다.