• The Journal of Korean Academy of Prosthodontics
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• v.40 no.2
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• pp.193-200
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• 2002

For the purpose of decreasing the chair time in implant cases, the time needed to loosening and fastening the screw must be shortened. Nowadays, the two typical designs of screw head are slot and hexa form. This study aimed at the shortening of loosening and fastening time by modifying the slot and hexa form. Total of twelve dentists participate in these experiments, four of them were experienced and eight of them were novice dentists. 1. There were many differences in the speeds of screw loosening and fastening between personal experiences. Experienced dentists are faster than novice dentists. 2. There were many differences in the speeds by angulation of the implant, by the conditions of the muscle tonicity. 3. Revised slot and hexa Heads show the slightly shortened time for acrew looseing and fastening.

• Journal of Korean Dental Science
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• v.15 no.1
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• pp.75-83
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• 2022

Crown-type implant-assisted removable partial dentures (CIRPDs) can be a feasible treatment option for partially edentulous patients. Here we report a case with remaining unilateral mandibular teeth. Two implants were placed in the posterior portion of the mandible using a surgical guide, and a distal-extension removable partial denture with implant-supported surveyed crowns was fabricated. After 12 months, both the abutment teeth and implants were in good condition. The treatment outcomes were satisfactory in terms of masticatory function and esthetics. The advantages of CIRPDs and considerations for obtaining successful clinical outcomes with these dentures are also discussed.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.30 no.1
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• pp.52-59
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• 2008

The geometric design of an implant surface may play an important role in affecting early osseointegration. It is well known that the porous surfaced implant had much benefits for the osseointegration and the early stability of implant. However, the porous surfaced implant had weakness from the transgingival contamitants, and it resulted in alveolar bone loss. The other problem identified with porous surface implant is the loss of physical properties resulting from the bead sintering process. In this study, we developed the new bead coating implant to overcome the disadvantages of porous surfaced implant. Ti-6Al-4V beads were supplied from STARMET (USA). The beads were prepared by a plasma rotating electrode process (PREP) and had a nearly spherical shape with a diameter of 75-150 ${\mu}m$. Two types of titanium implants were supplied by KJ Meditech (Korea). One is an external hexa system (External type) and the other is an internal system with threads (Internal type). The implants were pasted with beads using polyvinylalcohol solution as a binder, and then sintered at 1250 $^{\circ}C$ for 2 hours in vacuum of $10^{-5}$ torr. The resulting porous structure was 400-500 ${\mu}m$ thick and consisted of three to four bead layers bonded to each other and the implant. The pore size was in the range of 50-150 ${\mu}m$ and the porosity was 30-40 % in volume. The aim of this study was to evaluate the osseointegration of the newly developed dental implant. The experimental implants (n=16) were inserted in the unilateral femur of 4 mongrel dogs. All animals were killed at 8 weeks after implantation, and samples were harvested for hitological examination. All bead coated porous implants were successfully osseointegrated with peripheral bone. The average bone-implant contact ratios were 84.6 % (External type) and 81.5 % (Internal type). In the modified Goldner's trichrome staining, new generated mature bones were observed at the implant interface at 8 weeks after implantation. Although, further studies are required, we could conclude that the newly developed vacuum sintered Ti-6Al-4V bead coating implant was strong enough to resist the implant insertion force, and it was easily osseointegrated with peripheral bone.

• The korean journal of orthodontics
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• v.37 no.3 s.122
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• pp.171-181
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• 2007

Objective: The present study was aimed at an analytical formulation of the micro-implant related torque as a function of implant size, i.e. the diameter and length, screw size, and the bony resistance at the implant to bone interface. Methods: The resistance at the implant to cancellous bone interface $(S_{can})$ was assumed to be in the range of 1.0-2.5 MPa. Micro-implant model of Absoanchor (Dentos Inc. Daegu, Korea) was used in the course of the analysis. Results: The results showed that the torque was a strong function of diameter, length, and the screw height. As the diameter increased and as the screw size decreased, the torque index decreased. However the strength index was a different function of the implant and bone factors. The whole Absoanchor implant models were within the safe region when the resistance at the implant/cancellous bone $(=S_{can})$ was 1.0 or less. Conclusion: For bone with $S_{can}$ of 1.5 MPa, the cervical diameter should be greater than 1.5 mm if micro-implant models of 12 mm long are to be placed. For $S_{can}$ of 2.0 MPa, micro-implant models of larger cervical diameter than 1.5 mm were found to be safe only if the endosseous length was less than 8 mm.

• Journal of Technologic Dentistry
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• v.43 no.4
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• pp.202-209
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• 2021

By classifying temporary denture production for surgical guides, digital guide-based surgery, and final prosthesis production, the problems of each process were assessed in advance and the factors that could be improved were confirmed in this study. The manufacturing process of fusion dental prosthesis uses virtual programs and computed tomography images to manufacture devices using the latest technologies of computer-aided design/computer-aided manufacturing and three-dimensional printing, which enables implants to be placed in the desired location in advance. Moreover, implant placement is not dependent on the skill and condition of the dentist, and because it uses a computer system, it can always be performed at a constant and optimal position. This can reduce the remanufacturing rate compared with the general method, shorten the treatment period, and eliminate patient discomfort. Unlike the traditional method of using impression materials and plaster models, digital fusion dental prostheses would be evaluated as a technology for producing prosthesis through professional design technology and communication.

• Journal of International Society for Simulation Surgery
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• v.1 no.1
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• pp.13-15
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• 2014

Nowadays, with advanced 3D printing techniques, the custom-made implant can be manufactured for the patient. Especially in skull reconstruction, it is difficult to design the implant due to complicated geometry. In large defect, an autograft is inappropriate to cover the defect due to donor morbidity. We present the process of manufacturing the 3D custom-made implant for skull reconstruction. There was one patient with skull defect repaired using custom-made 3D titanium implant in the plastic and reconstructive surgery department. The patient had defect of the left parieto-temporal area after craniectomy due to traumatic subdural hematoma. Custom-made 3D titanium implants were manufactured by Medyssey Co., Ltd. using 3D CT data, Mimics software and an EBM (Electron Beam Melting) machine. The engineer and surgeon reviewed several different designs and simulated a mock surgery on 3D skull model. During the operation, the custom-made implant was fit to the defect properly without dead space. The operative site healed without any specific complications. In skull reconstruction, autograft has been the treatment of choice. However, it is not always available and depends on the size of defect and donor morbidity. As 3D printing technique has been advanced, it is useful to manufacture custom-made implant for skull reconstruction.

• The Journal of Advanced Prosthodontics
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• v.4 no.4
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• pp.227-234
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• 2012

PURPOSE. The aims of this pilot study were to introduce implant loading devices designed for animal study and to evaluate the validity of the load transmission ability of the loading devices. MATERIALS AND METHODS. Implant loading devices were specially designed and fabricated with two implant abutments and cast metal bars, and orthodontic expansion screw. In six Beagles, all premolars were extracted and two implants were placed in each side of the mandibles. The loading device was inserted two weeks after the implant placement. According to the loading protocol, the load was applied to the implants with different time and method, simulating early, progressive, and delayed loading. The implants were clinically evaluated and the loading devices were removed and replaced to the master cast, followed by stress-strain analysis. Descriptive statistics of remained strain (${\mu}{\varepsilon}$) was evaluated after repeating three cycles of the loading device activation. Statistic analysis was performed using nonparametric, independent t-test with 5% significance level and Friedman's test was also used for verification. RESULTS. The loading devices were in good action. However, four implants in three Beagles showed loss of osseointegration. In stress-strain analysis, loading devices showed similar amount of increase in the remained strain after applying 1-unit load for three times. CONCLUSION. Specialized design of the implant loading device was introduced. The loading device applied similar amount of loads near the implant after each 1-unit loading. However, the direction of the loads was not parallel to the long axis of the implants as predicted before the study.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.192-209
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• 2004

Purpose : The purpose of this study was to evaluate the machining accuracy and consistency of implant/abutment/screw combination or internal connection type. Material and methods: In this study, each two randomly selected internal implant fixtures from ITI, 3i, Avana, Bicon, Friadent, Astra, and Paragon system were used. Each abutment was connected to the implant with 32Ncm torque value using a digital torque controller or tapping. All samples were cross-sectioned with grinder-polisher unit (Omnilap 2000 SBT Inc) after embeded in liquid unsaturated polyester (Epovia, Cray Valley Inc). Then optical microscopic and scanning electron microscopic(SEM) evaluations of the implant-abutment interfaces were conducted to assess quality of fit between the mating components. Results : 1) Generally, the geometry of the internal connection system provided for a precision fit of the implant/abutment into interface. 2) The most precision fit of the implant/abutment interface was provided in the case of Bicon System which has not screw. 3) The fit of the implant/abutment interface was usually good in the case of ITI, 3I and Avana system and the amount of fit of the implant/abutment interface was similar to each other. 4) The fit of the implant/abutment interface was usually good in the case of Friadent, Astra and Paragon system. The case of Astra system with the inclined contacting surface had the most Intimate contact among them. 5) Amount of intimate contact in the abutment screw thread to the mating fixture was larger in assembly with two-piece type which is separated screw from abutment such as Friadent, Astra and Paragon system than in that with one-piece type which is not seperated screw from abutment such as ITI, 3I and Avana system. 6) Amount of contact in the screw and the screw seat of abutment was larger in assembly of Friadent system than in asembly of Astra system of Paragon system. Conclusion: Although a little variation in machining accuracy and consistency was noted in the samples, important features of all internal connection systems were the deep, internal implant-abutment connections which provides intimate contact with the implant walls to resist micro-movement, resulting in a strong stable interface. From the results of this study, further research of the stress distribution according to the design of internal connection system will be required.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.4
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• pp.391-401
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• 2009

The successful outcome of dental implants is mainly the result of intial implant stability following placement. The aim of this study was to investigate the effect of a self-tapping blades and implant design on initial stability of two tapered implant systems in poor bone quality. The two different implant systems included one with self-tapping blades and one without self-tapping blades. D4 bone model using Solid Rigid Polyurethane Form was used to simulate poor bone densities. The insertion torque during implant placement was recorded. Resonance frequency Analysis (RFA), measured as the implant stability quotient (ISQ), was assessed immediately after insertion. Finally, the implant-bone specimen was transferred to an Universal Testing Machine to measure the axial pull-out force. Insertion torque values and maximum pull-out torque value of the non self-tapping implants were significantly higher than those in the self-tapping group (P = 0.008). No statistically differences were noted between the two implant designs in RFA. Within the each implant system, no correlation among insertion torque, maximum pull-out torque and RFA value could be determined. Higher insertion torque of the non-self-tapping implants appeared to confirm higher clinical initial stability. In conclusion, implants without self-tapping blades have higher initial stability than implants with self-tapping blades in poor bone quality.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.2
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• pp.205-220
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• 2010

Purpose : To analyze the effect of implant designs on insertion torque and stress by performing a comparative study on von Mises stress, torque and normal force through a three-dimensional finite element analysis. Materials and methods : Models of the screw type implant were used to model the implant as a form placed in the mandibular premolar region applying a three-dimensional finite element method. Screw type implant designs were classified into 4 types of parallel ones and 7 types of tapered ones. Other factors were simulated to represent clinical environment. Results : In parallel implant designs, higher and wider threads resulted in higher insertion torques and higher stress distributions. In tapered implant designs, changes in the taper led to remarkable differences in the insertion torques. It was difficult to determine a certain tendency of stress distribution around the implants since the stress level was too high around them. In tapered implant designs, smaller implants demonstrated lower insertion torques than the original type and were relatively less dependent on the degree of taper. Tapered implants showed higher insertion torques and higher stress distributions than parallel implants. Conclusion : According to this study, although the tapered implant demonstrated a higher insertion torque than the parallel implant, stress tended to be concentrated in the entire fixture of the tapered implant due to the inefficient stress distribution.