• Journal of the Korean Society for Precision Engineering
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• v.25 no.2
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• pp.148-155
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• 2008

The aim of the study is to interpret the distribution of occlusal force by 3-dimensional finite element analysis of ISP(Implant Supported Prosthesis) supported by minimum number of implant to restore the edentulous patients. For this study, the Astra Tech implant system is used. Geometric modeling for 6 and 4 fixture ISP group is performed with respect to the bone, implant and one piece superstructure, respectively. Implants are arbitrarily placed according to the anatomical limit of lower jaw and for the favorable distribution of occlusal force, which is applied at the end of cantilever extension of ISP with 30mm. Element type is tetrahedral for finite element model and the typical mechanical properties, Young's modulus and Poisson's ratio of each material, cortical, cancellous bone and implant material are utilized for the finite element analysis. From this study, we can see the distribution of equivalent stress equal to real situation and speculate the difference in the stress distribution in the whole model and at each implant fixture, From the analysis, the area of maximum stress is distributed on distal contact area between bone and fixture in the crestal bone. The maximum stress is 53MPa at the 0.2mm area from the bone-implant interface in the maximum side for 300N load condition for 4 fixture case, which is slightly less than the stress calculated from allowable strain. This stress has not been deduced to directly cause the loss of crestal bone around implant fixture, but the stress can be much reduced as the old peoples may have lower chewing force. Thus, clinical trial may be performed with this treatment protocol to use 4 fixtured ISP for old patients.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.29 no.2
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• pp.66-74
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• 2020

Communication and cooperation between dentists and dental technicians are two essential elements for the fabrication of high quality 'custom' prosthesis. For successful communication and cooperation between the two groups, however, dentists and dental technicians must share common understanding about clinical dentistry. Ironically, it is often noticed that they are not really sharing the same clinical knowledge. Although there is a strong association between 'Emergence Profile' of implant prostheses and periodontal health or esthetics, no definite guideline has ever been provided for ideal emergence profile of implant prosthesis in literature. Problems resulted from inherent differences between implants and natural teeth must be acknowledged and shared between dentists and dental technicians so that they can come up with desirable clinical results with implant prostheses.

• The Journal of Korean Academy of Prosthodontics
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• v.62 no.1
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• pp.28-37
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• 2024

Severe cases of mandibular prognathism can be treated with orthodontic therapy or surgical correction, but there are situations where only prosthetic improvement is possible. An understanding of class III patients is needed, including a vertical chewing pattern and the absence of anterior guidance. Additionally, it is relatively easy to increase occlusal vertical dimension to correct the anterior crossbite, but this approach can sometimes lead to unfavorable results, necessitating careful diagnosis and treatment planning. In this case report, oral rehabilitation was conducted in a patient with mandibular prognathism and asymmetry, utilizing implants and fixed dental prosthesis. Through a step-by-step treatment approach, the existing occlusal vertical dimension was maintained, and the final fixed dental prosthesis restoration was completed. Accordingly, it shows functional and aesthetically appropriate results, and reports on the patient's diagnosis and treatment process.

• Journal of Dental Rehabilitation and Applied Science
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• v.20 no.2
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• pp.71-81
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• 2004

The purpose of this study was to compare the distributing pattern of stress on the finite element models of two units implant prosthesis with one angulated placement of two implant fixtures. The two unit implant crowns simulated to mandibular first and second molars were made. The two kinds of finite element models were designed according to angulation of fixture ($4.0mm{\times}11.5mm$) : Model 1($15^{\circ}$ buccally angulated placement of one fixture on second molar area), Model 2($15^{\circ}$ lingually angulated placement of one fixture on second molar area). Axial loads of 200N were applied to the center of central fossa and to distance of 2mm and 4mm apart from the center of central fossa. Von-Mises stresses were recorded and compared in the fixtures, and buccolingual section of implants. The results were as follows: 1. Under axial loading at the central fossa, the stress was distributed along the straight fixture except apical portion, while on buccally or lingually angulated placement, the highest stresses were concentrated in the neck portion on the opposite side of the angulated fixture. 2. With offset distance increasing, the stresses were concentrated greater in buccal neck of lingually angulated fixture than in lingual neck of buccally angulated fixture. From the above results, in designing of the occlusal scheme for implant prosthesis with the angulated fixture, occlusal contacts should be placed to distribute stress axially in maximum intercuspation and to avoid offset force during eccentric movements.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.3
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• pp.252-257
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• 2014

It is important to produce a provisional restoration reflecting the patient's jaw relation, occlusal plane, lip support, shape of teeth, and occlusion type for fully edentulous patients before making a definite prosthesis. The patient introduced in this study showed bad prognosis of remained tooth after severe periodontal diseases. Therefore, remaining teeth were extracted and replaced with dental implants. Provisional restorations were fabricated and the the patient's vertical and horizontal jaw relationship, occlusal plane, amount of overjet and overbite, size of teeth, and length of anterior tooth were recorded. Provisional restorations were scanned and CAD/CAM techniques were used to fabricate a monolithic zirconia bridge, which contour is identical with the provisional restorations. The patient was satisfied with the treatment results on functional, esthetic aspects and the prosthesis retained stable during the four-month clinical observation period.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.4
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• pp.767-780
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• 1997

One of the most common problems of implant prosthesis is the screw loosening of abutment screws. This brings on discomfort in mastication, inflammation in the peri-implant tissue due to poor oral hygiene and fracture of prosthesis or loss of osseointegration. To prevent screw loosening, appropriate implantation to direct the occlusal force to the long axis of the implant, accurate design of the superstructure, decrease of the occlusal table, and adequate torque on the abutment screw are necessary. In this study the screw loosening torque was evaluated in implants with dimples or flutes in the internal surface of abutment screw holes. The abutments were fastened with slot type and hexagonal type abutment screws and were sealed with vinyl poly siloxane impression and bite registration material respectively. The screw loosening torque was evaluated after 1,800 and 12,600 times loading under a loading machine. The results were as follows. 1. The flute form group showed significantly higher loosening torque compared to the dimple form group and the group with no inner surface treatment (p<0.05). 2. There was no statistical difference in loosening torque according to the sealing materials. 3. The loosening torque according to the types of abutment screw showed no significant difference. 4. The loosening torque was significantly higher after 1800 times loading compared to 12600 times loading(p<0.05). From the above results. it is thought that formation of a flute in the internal surface of the screw hole decreases the chance of screw loosening, but the sealing materials and types of abutment screw did not show significant difference in prevention of screw loosening.

• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.3
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• pp.246-252
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• 2014

$Br{\aa}nemark^{\prime}s$ original protocol required 4 to 6 months for implant osseointegration before placement of the definitive prosthesis. Although this approach gave very predictable results, it had certain drawbacks. The main disadvantages of this approach were prolonged treatment time, two surgical procedures, placement of a removable prosthesis that required modifications during the course of treatment, and a greater number of appointments. Immediate implant loading is a viable treatment method for selected cases. One of the greatest advantages of this method is the virtual surgery, which precedes the actual clinical treatment and eliminates any need for last minute decisions. The actual surgery time is decreased, since all steps are predetermined. These advantages aren't only more useful for normal patients but also for the mental retardation patients whose cooperation is difficult. This article presents a clinical approach made possible due to the guided implant surgery and CAD/CAM technique.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.31 no.2
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• pp.47-55
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• 2022

Food impaction due to proximal space opening after implant restoration is a very common phenomenon in patients who have implant prosthesis. This occurs because the movement mechanism between the implant and the tooth is different, and it occurs about 30-60% over time. Contributing factors include the arch (mandible), region (posterior teeth), adjacent teeth (non-vital teeth), and antagonist teeth (natural teeth or implants), etc. While this phenomenon cannot be prevented, efforts should be made to minimize it. In order to have an ideal proximal contact as much as possible, the concave shape or the prominent lower proximal shape should be modified to create a symmetrical proximal shape. with the buccal dentate in the upper third height should be adjusted. Other conditions should be modified so that the heights of the marginal ridges are similar. Since an irregular occlusal plane is a cause of poor prognosis, food impaction should be minimized by restoring the ideal occlusal plane by correcting the extruded antagonist and reduction of the disto-buccal cusp.

• The Journal of Korean Academy of Prosthodontics
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• v.62 no.2
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• pp.174-182
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• 2024

In patients with multiple missing molars, wear patterns or displacement of anterior teeth, collapsed occlusal plane, and reduction in vertical dimension may occur. Particularly, in case of a few remaining teeth on one side, a removable partial denture has biomechanical disadvantage. For this reason, an implant-assisted removable partial denture with a few implant surveyed crowns can be an alternative. In this case, due to the right mandibular posterior teeth loss, the anterior teeth were severely worn and the occlusal plane was collapsed. With minimal increasing vertical dimension, oral rehabilitation was performed using a maxillary fixed prosthesis and mandibular implant-assisted removable partial denture. As a result, functional and aesthetic clinical outcomes were obtained.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.2
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• pp.126-133
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• 2018

The development of cone beam computerized tomography (CBCT) allows three-dimensional analysis of the patient's anatomy. The surgical guide is a combination of CBCT, computer-aided design/computer-aided manufacturing (CAD/CAM) and implant diagnostics software, which allows well planned prostheses design and ideal implant placement. Guided surgery minimizes possible anatomical damage and allows for more reproducible treatment planning. In this case, the operation time was shortened by using a surgical guide for multiple implants placement in a fully edentulous patient. Immediate loading were performed more easily using preliminary preparation of provisional prosthesis. The patient was satisfied with improved esthetics and chewing function.