• The Journal of Advanced Prosthodontics
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• v.7 no.2
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• pp.160-165
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• 2015

PURPOSE. In this study, a temporal abutment fixation screw, designed to fracture in a controlled way upon application of an occlusal force sufficient to produce critical micromotion was developed. The purpose of the screw was to protect the osseointegration of immediate loaded single implants. MATERIALS AND METHODS. Seven different screw prototypes were examined by fixing titanium abutments to 112 Mozo-Grau external hexagon implants (MG Osseous$^{(R)}$; Mozo-Grau, S.A., Valladolid, Spain). Fracture strength was tested at $30^{\circ}$ in two subgroups per screw: one under dynamic loading and the other without prior dynamic loading. Dynamic loading was performed in a single-axis chewing simulator using 150,000 load cycles at 50 N. After normal distribution of obtained data was verified by Kolmogorov-Smirnov test, fracture resistance between samples submitted and not submitted to dynamic loading was compared by the use of Student's t-test. Comparison of fracture resistance among different screw designs was performed by the use of one-way analysis of variance. Confidence interval was set at 95%. RESULTS. Fractures occurred in all screws, allowing easy retrieval. Screw Prototypes 2, 5 and 6 failed during dynamic loading and exhibited statistically significant differences from the other prototypes. CONCLUSION. Prototypes 2, 5 and 6 may offer a useful protective mechanism during occlusal overload in immediate loaded implants.

• Journal of Biomedical Engineering Research
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• v.19 no.5
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• pp.487-495
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• 1998

In this paper, a new type of implantable middle ear hearing aid, which consists of external loop coil, a small magnet and a simple external device, is proposed. The internal device of proposed type consists of only a small magnet and the external device does not need to be positioned behind the ear or in the ear canal. The proposed type is excellent in cosmetic sides and very convenient to use, because the external device can be hidden in upper garment and collar of clothes. Also, purposely this type doesn't need to be small on the size of battery, which means it has longer battery life. Therefore, the battery is not necessary to be charged frequently. It also can solve the difficulty of gap calibration at surgical operation which conventional Implantable middle. Therefore, the battery is not necessary to be charged frequently. It also can solve the difficulty of gap calibration at surgical operation which conventional implantable middle ear hearing aid has. We investigate the performance of proposed implantable middle ear bearing aid and we analyze that proposed type is appropriate for mild and severe hearing impaired person and the result of experiment showed the accuracy of our analysis. For the validation of our analysis we used the temporal bone at the experiment and confirm that ossicles can be vibrated when the proposed system In startled in the body.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.2
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• pp.240-249
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• 2007

Statement of problem: A phenomenon of screw-loosening in implant abutment is frequently occurred in a single and multiple implant restoration. Purpose: This study was performed to evaluate an effect of abutment material on screw-loosening before and after a cyclic loading. In a single-tooth implant, different materials of abutment, Type III Gold alloy and Zirconium composite$(ZrO_2/Al_2O_3)$ were used. Material and method: The Gold alloy(Type III) and Zirconium composite$(ZrO_2/Al_2O_3)$ were used to make a superstructure of implant, the one of types of UCLA, Each group was constituted of 5 sample with a 30-degree offset angulated loading platform. The external hexagonal fixture was rigidly hel d in a special holding zig to ensure solid fixation without rotation during the tightening and a cyclic loading. A Titanium-alloy screw was used to connect and controlled to be tighten in 20Ncm torque by a digital torque gauge. A 20 times of consecutive closing/opening cycle were performed to evaluate the immediate torque loss. In 5 sample of each material group, an initial opening torque was recorded during 3 closing/opening cycle, then 2Hz, 200N, 1,000,000 cyclic loadings were performed, then a opening torque was evaluated. Result & Conclusion: 1. In this limited study, titanium alloy screw tightened in 20Ncm, a cold-welding phenomen on was not observed during the 20 times of closing/opening cycle(p=0.11, p=0.18). 2. In titanium alloy abutment screw, repeated opening and closing of the screw caused to progressive decrease of opening torque(p=0.014). 3. The difference in preload of screw between gold alloy abutment and ceramic$(ZrO_2/Al_2O_3)$ abutment was not significant(p=0.78). 4. The difference in torque loss of screw between gold alloy abutment and ceramic$(ZrO_2/Al_2O_3)$ abutment was not significant after 2Hz,200N, 1,000,000 cyclic loading(p=0.92). 5. In titanium alloy abutment screw tightened by 20Ncm, the screw loosening was not significant on each group after 2Hz, 200Ncm, 1,000,000 cyclic loading(p=0.59).

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.114-118
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• 2017

Purpose: The aim of this study was to investigate the effects of a titanium component for the zirconia abutment in the internal connection implant system on screw loosening under thermocycling conditions. Materials and Methods: Internal connection titanium abutments and external connection zirconia abutments with titanium sockets were connected respectively to screw-shaped internal connection type titanium implants with 30 Ncm tightening. These implant-screw-abutment assemblies were divided into two groups of five specimens each; titanium abutments as control and zirconia abutments with titanium sockets as experimental group. The specimens were subjected to 2,000 thermocycles in water baths at $5^{\circ}C$ and $55^{\circ}C$, with 60 seconds of immersion at each temperature. The removal torque values (RTVs) of the abutment screws of the specimen were measured before and after thermocycling. RTVs pre- and post-thermocycling were investigated in statistics. Results: There was not screw loosening identified by tactile and visual inspection in any of the specimens during or after thermocycling. The mean RTV difference for the control group and the experimental group were $-1.34{\pm}2.53Ncm$ and $-1.26{\pm}2.06Ncm$, respectively. Statistical analysis using an independent t-test revealed that no significant differences were found in the mean RTV difference of the groups (P > 0.05). Conclusion: Within the limitations of this in vitro study, the titanium socket for the zirconia abutment did not show a significant effect on screw loosening under thermal stress compared to the titanium abutment in the internal connection implant.

• The Journal of the Korean dental association
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• v.53 no.9
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• pp.644-655
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• 2015

Purpose: This study was conducted to evaluate the effect of the fixture abutment connection type and diameter on the screw joint stability in external butt joint for 2nd surgery and internal cone connected type implant system for 1st and 2nd surgery using ultimate fracture strength. Materials and Methods: USII system, SSII system and GSII system of Osstem Implant were used. Each system used the fixture with two different diameters and cement-retained abutments, and tungsten carbide / carbon coated abutment screws were used. Disc shaped stainless steel metal tube was attached using resin-based temporary cement. The experimental group was divided into seven subgroups, including the platform switching shaped specimen that uses a regular abutment in the fixture with a wide diameter in USII system. A static load was increased to the metal tube at 5mm deviated point from the implant central axis until it reached the compression bending strength at a rate of 1mm/min. Then the deformations and patterns of fracture in threaded connection were compared. Results and Conclusion: 1. In the comparison between the Regular diameter, compression bending strength of SSII system was higher than USII system and GSII system. There was no significant difference between USII system and GSII system. 2. In the comparison between wide diameter, compression bending strength was increased in the order of GSII system, USII system, and SSII system. 3. In comparison between the implant diameter, compression bending strength of the wide diameter was greater than the regular diameter in any system(P<0.05). 4. There was no significant difference between the platform switching (III group) and the regular diameter (I group) in USII system. 5. In USII system, fracture of abutment screw and deformation of both fixture and abutment were observed in I, II and III subgroups. 6. Failure pattern of SSII system, which was the fracture of abutment screw and deformation of the abutment and fixture, was observed in both IV and V subgroups. Fracture of some fixtures was observed in subgroup V. 7. Failure pattern of GSII system, which was the fracture of the abutment screw and deformation of the fixture and the abutment, was observed in both VI and VII subgroups. Apart from other subgroups, subgroup VII demonstrated no bending neither the fracture at the top of the fixture. The compressive deformation of internal slope in the fixture was the only thing observed in subgroup VII.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.2
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• pp.127-138
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• 2012

This study is to assess the effect of preload level on the stress development at the marginal cortical bone surrounding implant neck. A finite element model was created for a single implant placed in the lower jaw bone. An external load of 100N was applied on the top of abutment at 30 degree with the implant axis in lingo-buccal direction. Five different preloads, i.e. 0, 200, 400, 600, 800N were applied to the abutment stem to investigate if and/or how the preload affects on the marginal bone stress. Differences in the marginal bone stress were recorded depending on the level of preload. On the other hand, the tensile stress on the marginal cortical bone decreased in models of higher preload. Preloads between abutment/fixture can increase compressive stresses in the marginal cortical bone although the amount may be insignificant as compared to those generated by functional forces.

• Journal of Dental Rehabilitation and Applied Science
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• v.39 no.4
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• pp.267-275
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• 2023

To obtain better esthetic results when immediately placing a dental implant, the soft tissue surrounding the implant must be conditioned during healing of the extraction socket. To this end, the emergence profile can be customized through immediate restoration of the provisional prosthesis, and good clinical results can be obtained at the time of definitive restoration in the future, resulting in high patient satisfaction. In this case, horizontal root fracture occurred after trauma to both maxillary central incisors. Immediate implant placement and loading was planned considering aesthetics and alveolar bone condition. By taking an impression using a digital intraoral scanner, a digital diagnostic wax-up was performed to make a more aesthetic prosthesis without applying external force to the traumatized teeth. Based on this, the ideal placement location was determined and immediate implant placement was performed using a 3D printed surgical guide. The provisional prosthesis was restored 5 days after placement, and the definitive zirconia crown was restored through soft tissue conditioning and customization using the shape of the provisional prosthesis for 3 months.

• Radiation Oncology Journal
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• v.16 no.2
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• pp.167-175
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• 1998

Purpose : It is not a simple task to achieve the ideal isodose curve with a standard vaginal applicator or sing1e plane needle impant in the paravaginal tissue when primary or recurrent gynecological neoplasms(cervical cancers, vaginal cancers and vulvar cancers) are treated as a boost following external beam radiotherapy. The authors introduce the development and construction of a simple, inexpensive, customized applicator for volume implant to maximize the radiation dose to the tumor while minimizing the dose to the rectum and the bladder. Materials and Methods : Nine patients underwent Ir-192 transperineal interstitial implantation for either recurrent(5 cases) or primary(3 cases) cervical cancers or primary vaginal cancer(1 case) between August 1994 and February 1998 at Ajou university hospital. First 3 cases were performed with a sing1e plane implant guided by digital palpation. Because of inadequate isodose coverage in the tumor volume in first 3 cases, we designed and constructed interstitial vaginal applicator for volume implant to improve tumor dose distribution and homogeneity while sparing the surrounding normal tissue. Our applicators consist of vaginal obturator and perineal template that made of the clear acrylamide and dental mold material$(Provil^{(R)})$. The applicators were customized individually according to the tumor size and its location Both HDR and LDR irradiation were given with these applicators accomodating 6 Fr needles(Microselectron Nucletron). The pretreatment planning prior to actual implant was performed whenever possible. Results : Needles can be inserted easily and evenly into the tumor volume through the holes of templates, requiring less efforts and time for the implant procedure. Our applicators made of materials available from commercial vendors. These have an advantage that require easy procedure, and spend relatively short time to construct. Also it was possible to fabricate applicators to individualize according to the tumor size and its location and to achieve the ideal isodose coverage. We found an accurate needle arrangement and ideal dose distribution through the CT scan that was obtained in 3 cases after needle implant. Three patients with primary cervical and vaginal cancers were controlled locally at final follow up. But all recurrent cases failed to do so. Conclusion : The authors introduce inexpensive, simple interstitial vaginal templates which were self-designed and constructed using materials available from commercial vendors such as acrylanide and dental mold material $(Provil^{(R)})$.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.2
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• pp.179-195
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• 2010

In the internal connection system, the loading transfer mechanism within the inner surface of the implant and also the stress distribution occuring to the mandible can be changed according to the abutment form. Therefore it is thought to be imperative to study the difference of the stress distribution occuring at the mandible according to the abutment form. The purpose of this study was to assess the loading distributing characteristics of three different abutments for GS II$^{(R)}$ implant fixture(Osstem, Korea) under vertical and inclined loading using finite element analysis. Three finite element models were designed according to three abutments; 2-piece Transfer$^{TM}$ abutment made of pure titanium(GST), 2-piece GoldCast$^{TM}$ abutment made of gold alloy(GSG), 3-piece Convertible$^{TM}$ abutment with external connection(GSC). This study simulated loads of 100N in a vertical direction on the central pit(load 1), on the buccal cusp tip(load 2) and $30^{\circ}$ inward inclined direction on the central pit(load 3), and on the buccal cusp tip(load 4). The following results were obtained. 1. Without regard to the loading condition, greater stress was concentrated at the cortical bone contacting the upper part of the implant fixture and lower stress was taken at the cancellous bone. 2. When off-axis loading was applied, high stress concentration observed in cervical area. 3. GSG showed even stress distribution in crown, abutment and fixture. GST showed high stress concentration in fixture and abutment screw. GSC showed high stress concentration in fixture and abutment. 4. Maximum von Mises stress in the surrounding bone had no difference among three abutment type. In GS II$^{(R)}$ conical implant system, different stress distribution pattern was showed according to the abutment type and the stress-induced pattern at the supporting bone according to the abutment type had no difference among them.

• Journal of Dental Rehabilitation and Applied Science
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• v.27 no.4
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• pp.343-358
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• 2011

As implant treatment has become popular, lots of different shapes and materials of the implant upper component have been supplied. And there are also diverse reports about failures including loosening of the abutment screw which is one of the most common reason. Purpose : The purpose of this study is to find out how different screw tightening orders and methods influence on screw loosening according to the different connection systems. The upper component was fabricated by casting method. After fabricating master models that are precisely attached to the upper component, 5 experimental models each for the external connection system and internal connection system were fabricated using splinting impression technique. First, to find out the influence of the screw tightening order, screws were tightened in 3 orders; 1-2-3-4, 2-3-1-4, 2-4-3-1. After tightening, removal torque values (RTV) of each group was measured. And also to find out the influence of screw tightening method, a model with 2-3-1-4 screw tightening order was tightened with 30 Ncm at one time(1-step method) and the RTV was compared with the same order group (2-3-1-4) in the 2 step method. In the external connection system, RTV appeared significantly lower in group 2-3-1-4 than group 2-4-3-1 (p<0.05). And also in the internal connection system, the RTV of group 2-3-1-4 appeared significantly lower than that of group 2-4-3-1 and 1-2-3-4 (p<0.05). When comparing the tightening number of the screw without considering the screw tightening order, the first tightened screw appeared significantly higher RTV than the second one in the external connection system (p<0.05), however there was no significant difference from the first tightened screw to the last tightened screw in the internal connection system. And there was no statistically significant difference between the two screw tightening methods in both internal and external connection system. In the comparison of external and internal connection system, each RTV appeared 16.27 Ncm and 14.25 Ncm and appeared as a statistically significant difference (p<0.05). There was a significant difference in RTV measured according to the screw tightening order. The lowest RTV appeared in the groups started tightening from the middle. There was also a significant difference in RTV between the two connection system groups. A further study is needed to find out the influence factors in RTV and also a study is required related to the load condition.