• The Journal of Advanced Prosthodontics
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• v.14 no.1
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• pp.22-31
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• 2022

PURPOSE. The purpose of this study was to investigate the misfit and screw preload at the implant abutment connection of implant supported fixed dental prosthesis with cantilever (ICFDP) manufactured using different digital manufacturing techniques and to compare the screw preload before and after cyclic loading. MATERIALS AND METHODS. Mandibular jaw model with four intra-foraminal implants was scanned using digital scanner. Stereolithography file was used to design a framework with nonengaging (NE) abutments and 10 mm cantilever distal to one terminal implant. Five frameworks were constructed using combined digital-conventional techniques (CAD-cast), and five frameworks were constructed using three-dimensional printing (3DP). Additional CAD-cast framework was constructed in a way that ensures passive fit (PF) to use as control. Scanning electron microscope (SEM) measured the implant abutment connection misfit. Sixty screws were used on the corresponding frameworks. Screws were torqued and pre-cyclic loading reverse torque value (RTV) was recorded. Frameworks were subjected to 200,000 loading cycles with a loading point 9 mm from the center of terminal implants adjacent to the cantilever and post-cyclic loading RTVs were recorded. RESULTS. Microscopic readings showed significant differences between frameworks. PF demonstrated the lowest measurements of 16.04 (2.6) ㎛ while CAD-cast demonstrated the highest measurements of 29.2 (3.1) ㎛. In all groups, RTVs were significantly lower than the applied torque. Post-cyclic loading RTV was significantly lower than pre-cyclic loading RTV in PF and 3DP frameworks. Differences in RTVs between the three manufacturing techniques were insignificant. CONCLUSION. Although CAD-cast and three-dimensionally printed (3DP) both produce frameworks with clinically acceptable misfit, 3DP might not be the technique of choice for maintaining screw's preload stability under an aggressive loading situation.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.4
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• pp.339-346
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• 2022

Compared with traditional full dentures, mandibular implant overdentures have the advantage in that good support and retention can be obtained even with two implants. When manufacturing a mandibular implant overdenture using two implants, it is important to place the implant in the correct position. The long-term prognosis of overdenture is good when two implants are placed in the direction vertical to the occlusal plane and parallel to each other at the canine position. However, it is difficult to place two implants in the correct position in edentulous patients, and if you use surgical guides in these cases, you can get help in placing the implants in a prosthetically advantageous position. This case, a 57-year-old male patient, came to our hospital with all upper and lower teeth removed due to periodontal disease. Therefore, the maxilla was restored with a traditional full denture and the mandible was restored with an implant overdenture using two implants, which resulted in satisfactory functional and esthetic results.

• Journal of Audiology & Otology
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• v.23 no.3
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• pp.145-152
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• 2019

Background and Objectives: The present study aims to investigate whether the cochlear implant electrode array design affects the electrophysiological and psychophysical measures. Subjects and Methods: Eighty five ears were used as data in this retrospective study. They were divided into two groups by the electrode array design: lateral wall type (LW) and perimodiolar type (PM). The electrode site was divided into three regions (basal, medial, apical). The evoked compound action potential (ECAP) threshold, T level, C level, dynamic range (DR), and aided air conduction threshold were measured. Results: The ECAP threshold was lower for the PM than for the LW, and decreased as the electrode site was closer to the apical region. The T level was lower for the PM than for the LW, and was lower on the apical region than on the other regions. The C level on the basal region was lower for the PM than for the LW whereas the C level was lower on the apical region than on the other regions. The DRs on the apical region was greater for the PM than for the LW whereas the DR was narrower on the apical region than on the other regions. The aided air conduction threshold was not different for the electrode design and frequency. Conclusions: The current study would support the advantages of the PM over the LW in that the PM had the lower current level and greater DR, which could result in more localized neural stimulation and reduced power consumption.

• Korean Journal of Audiology
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• v.23 no.3
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• pp.145-152
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• 2019

Background and Objectives: The present study aims to investigate whether the cochlear implant electrode array design affects the electrophysiological and psychophysical measures. Subjects and Methods: Eighty five ears were used as data in this retrospective study. They were divided into two groups by the electrode array design: lateral wall type (LW) and perimodiolar type (PM). The electrode site was divided into three regions (basal, medial, apical). The evoked compound action potential (ECAP) threshold, T level, C level, dynamic range (DR), and aided air conduction threshold were measured. Results: The ECAP threshold was lower for the PM than for the LW, and decreased as the electrode site was closer to the apical region. The T level was lower for the PM than for the LW, and was lower on the apical region than on the other regions. The C level on the basal region was lower for the PM than for the LW whereas the C level was lower on the apical region than on the other regions. The DRs on the apical region was greater for the PM than for the LW whereas the DR was narrower on the apical region than on the other regions. The aided air conduction threshold was not different for the electrode design and frequency. Conclusions: The current study would support the advantages of the PM over the LW in that the PM had the lower current level and greater DR, which could result in more localized neural stimulation and reduced power consumption.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.4
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• pp.349-357
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• 2015

Edentulous patients with a severely resorbed mandible or maxilla often experience problems with conventional dentures, such as insufficient stability and retention, together with a decrease in chewing ability. Because of the good prognosis of dental implants, these patients can be successfully treated with implant-retained or implant-supported prosthesis. Ideally, a maximum number of implants of maximum length are placed in appropriate surgically prepared sites that are surrounded by a maximum amount of bone of favorable quality. The implants are favorably aligned faciolingually and mesiodistally to enhance optimal prosthodontic design. This article describes the clinical problems and complications encountered when treating a consecutive number of edentulous patients with osseointegrated implant-supported prostheses.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.8 no.1
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• pp.96-103
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• 1999

Restoration of missing oral tissues by using implant therapy is one of viable options in prosthodontic treatment. The purpose of oral rehabilitation are function, esthetics and phonetics. Recently, with the increasing esthetic demand of the patient, dentists and laboratory technicians are more concern ed about natural appearance of implant prostheses. There are so many factors which affect final esthetic results of treatment such a shape, color, proportion, gingival contour etc. To provide natural and vivid looking artificial prostheses to a patient, the careful diagnosis, treatment plan and laboratory Support is crucial. Several cases will be reviewed and discussed in terms of material, gingival shape, contour, speech and connection mode etc. to fabricate natural looking implant prostheses.

• The Journal of Advanced Prosthodontics
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• v.7 no.3
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• pp.264-270
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• 2015

This report describes the case of an edentulous patient with an atrophic maxilla and severe class III malocclusion. Prosthetic rehabilitation was performed using CAD/CAM techniques for manufacturing an implant-supported overdenture with horizontal insertion. A vestibulo-lingual insertion overdenture is a precision prosthesis with a fixation system affording a good fit between the primary and secondary structure. Both structures exhibit passive horizontal adjustment. This treatment option requires the same number of implants as implant-supported fixed dentures. The horizontal assembly system prevents the prosthesis from loosening or moving in response to axial and non-axial forces. The technique was used to rehabilitate a patient presenting an atrophic upper maxilla, with the insertion of 8 implants. No complications were reported at follow-up 3, 6 and 12 months after fitting of the prosthesis. This system offers solutions to the clinical and laboratory complications associated with hybrid prostheses, concealing emergence of the chimneys and improving implant-prosthesis hygiene.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.9
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• pp.769-775
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• 2016

Currently, dental implants are widely used as artificial teeth due to their good chewing performance and long life cycle. Generally, a dental implant consists of an abutment as the upper part and a fixture as the lower part. When chewing forces are repeatedly applied to a dental implant, a gap is often generated at the interfacial surface between the abutment and the fixture, and it results in some deterioration such as loosening of the fastening screw, dental retraction and fixture fracture. To enhance the sealing performance for coping with such problems, this study proposes a new sealing-type abutment having a number of grooves along the conical surface circumference, and it carries out finite element analysis in consideration of the external chewing force and pretension between the abutment and the fixture. The result shows that the proposed sealing-type abutment shows an enhanced sealing performance in terms of the contact pressure in comparison with a conventional abutment.

• The Journal of Korean Academy of Prosthodontics
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• v.62 no.1
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• pp.20-27
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• 2024

As a high-performance polymer, Polyetherketoneketone (PEKK) has good biocompatibility and excellent physical properties and is used in several areas, including dentistry. Many successful cases of implant-supported fixed prostheses with a PEKK framework have been reported; however, a long-term observation of the reported cases and discussion of complications are not available. In this case report, we present three cases of implant-supported fixed prostheses with a PEKK framework veneered with composite resin, lithium disilicate crown, and high-impact polymethyl methacrylate (PMMA), and discuss their 6-year follow-up results.

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