• The korean journal of orthodontics
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• v.36 no.4
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• pp.295-307
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• 2006

Objective: The purpose of this study was to compare the histological and biomechanical characteristics of self-tapping and self-drilling microscrew implants. Methods: 112 microscrew implants (56 self-drilling and 56 self-tapping) were placed into the tibia of 28 rabbits. The implants were loaded immediately with no force, light (100 gm), or heavy force (200 gm) with nickel-titanium coil springs. The animals were sacrificed at 3- and 5-weeks after placement and histologic and histomorphometric analysis were performed under a microscope. Results: All microscrew implants stayed firm throughout the experiment. There was no significant difference between self-drilling and self-tapping microscrew implants both in peak insertion and removal torques. Histologic examinations showed there were more defects in the self-tapping than the self-drilling microscrew implants, and newly formed immature bone was increased at the interface in the self-tapping 5-week group. There was proliferation of bone towards the outer surface of the implant and/or toward the marrow space in the self-drilling group. Histologically, self-drilling microscrew implants provided more bone contact initially but the two methods became similar at 5 weeks. Conclusion: These results indicate the two methods can be used for microscrew implant placement, but when using self-tapping microscrew implants, it seems better to use light force in the early stages.

• 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 Korean Dental Science
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• v.4 no.2
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• pp.52-58
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• 2011

Purpose: Modifications of implant design have been related to improving initial stability. The purpose of this study was to investigate their respective effect on initial stability between two tapered implant systems (self-tapping vs. non-self-tapping) in medium density bone using three different analytic methods. Materials and Methods: Self-tapping implant (GS III$^{(R)}$; Osstem Implant Co., Busan, Korea) and non-self-tapping implant (Replace Select$^{(R)}$; Nobel Biocare, G$\H{o}$teborg, Sweden) were investigated. In Solid rigid polyurethane blocks of artificially simulated Quality 2 bone, each of the 5 implants was inserted according to the manufacturer's instructions for medium-bone drilling protocol. Evaluation of initial stability was carried out by recording the maximum insertion torque (IT) and performing the resonance frequency analysis (RFA), and the pull-out test. Results: The IT and RFA values of self-tapping implant were significantly higher than those of non self-tapping implant (P=.009 and P=.047, respectively). In the pull-out values, no significant differences were found in implants between two groups (P=.117). Within each implant system, no statistically significant correlation was found among three different outcome variables. Conclusions: These findings suggest that design characteristics of implant geometry significantly influence the initial stability in medium bone density.

• The Journal of the Korean dental association
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• v.32 no.2 s.297
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• pp.123-124
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• 1994

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.315-318
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• 1997

In terms of productivity, the speed of machining process has been increasing in most of engineering part. But the tapping process does not reach at enough level compared with other machining processes because of its complicate cutting mechanism. In the high speed tapping process, the one of important elements is tool monitoring system to prevent tool breakage. This paper describes tool monitoring system by acoustic emission(AE) in the tapping process. We used 2 types of AE sensors in this test. The one is commercial sensor which is used in other machining monitoring system like polishing and the other is a self-fabricated sensor for this test. In this test we purpose to find out the frequency of AE signal in tapping process and verify the possibility of applying AE sensor in in-process tapping monitoring system. Also grasp of characteristic of tapping process by AE signal is handled.

• The Journal of Advanced Prosthodontics
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• v.3 no.1
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• pp.10-15
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• 2011

PURPOSE. This study investigated the influence of bone quality and surgical technique on the implant stability quotient (ISQ) value. In addition, the influence of interfacial bone quality, directly surrounding the implant fixture, on the resonance frequency of the structure was also evaluated by the finite element analysis. MATERIALS AND METHODS. Two different types of bone (type 1 and type 2) were extracted and trimmed from pig rib bone. In each type of bone, the same implants were installed in three different ways: (1) Compaction, (2) Self-tapping, and (3) Tapping. The ISQ value was measured and analyzed to evaluate the influence of bone quality and surgical technique on the implant primary stability. For finite element analysis, a three dimensional implant fixture-bone structure was designed and the fundamental resonance frequency of the structure was measured with three different density of interfacial bone surrounding the implant fixture. RESULTS. In each group, the ISQ values were higher in type 1 bone than those in type 2 bone. Among three different insertion methods, the Tapping group showed the lowest ISQ value in both type 1 and type 2 bones. In both bone types, the Compaction groups showed slightly higher mean ISQ values than the Self-tapping groups, but the differences were not statistically significant. Increased interfacial bone density raised the resonance frequency value in the finite element analysis. CONCLUSION. Both bone quality and surgical technique have influence on the implant primary stability, and resonance frequency has a positive relation with the density of implant fixture-surrounding bone.

• Industrial Engineering and Management Systems
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• v.10 no.3
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• pp.209-220
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• 2011

Self-tapping screws have some operational peculiarities. In spite of their economical advantage that requires no prior tapping operation, a weakness of self-tapping screw-tightening operations is that screws can easily be tightened at a non-right angle, thus resulting in an improper tightening strength. Increases in outsourced workers have reduced labor costs, but the accompanying high worker fluidity means that new workers are more frequently introduced into factories. It is necessary to train new workers for self-tapping screw-tightening operations, which occupies a considerable portion of ordinary assembly works. The purpose of this study is to develop and implement a skill transfer system for the operation. This study (1) proposes a set of characteristic values for evaluating the quality of the operation and develops a device that can measure these values; (2) proposes criteria for evaluating the resultant quality of the tightening; and (3) develops a skill training system for better work performance. Firstly, sets of characteristic values for evaluating the quality of the operation, namely, torque, vertical pressure forces and horizontal vibration forces, are proposed. A device that can measure these values is developed. Secondly, criteria for evaluating the resultant quality of the tightening are identified, involving tightening torque, maximum vertical pressure and timing, vibration area during the processing and tightening period, and work angle. By using such parameters, workers with the proper aptitude can be identified. Thirdly, a skill training system for the operation is developed. It consists of screwdriver operation training and screw-tightening training with feedback information about the results of the operation. Finally, the validity of the training system is experimentally verified using new operators and actual workers.

• Steel and Composite Structures
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• v.42 no.3
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• pp.315-323
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• 2022

Shear connectors are key elements that ensure integrity in a composite system. The primary purpose of a shear connector is to bring a high degree of interaction between composite elements. A wide variety of connectors are available for hot-rolled composite construction, connected to the beam through welding. However, with cold-formed members being very thin, welding of shear connectors is not desirable in cold-formed composite constructions. Shear connectors for cold-formed elements are limited in studies as well as in the market. Hence in this study, three different types of shear connectors, namely, single-channel, double channel, and self-tapping screw, were considered, and their performance assessed by the Push-out test as per Eurocode 4. The connection between channel shear connectors and the beam was made using self-tapping screws to avoid welding. The performance of the connectors was analyzed based on their ultimate capacity, characteristic capacity, ductility, and slippage during loading. Strength to weight ratio was also carried out to understand the proposed connectors' suitability for conventional ones. The results showed relatively higher initial stiffness and ductility for double channel connectors than other connectors. Also, self-tapping screws had a higher strength to weight ratio with low ductility.

• The Journal of the Korean dental association
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• v.32 no.4 s.299
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• pp.278-278
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• 1994

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.192-195
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• 2003

There has been increasing interest in the applications of synthesized molecules of nanometer scale in recent years due to their potential utilization in various fields such as biology, optoelectronics and molecular electronics. In this study, the terpyridine-platinum (II) complex on the periphery of the dendritic carbosilane has been prepared from the reaction of Pt(COD)Cl2 and the 4'-functionalized-(2,2':6',2"-terpyridine) on dendrimers. The self-assembly process was carried out to obtain indivially dispersed dendrimer on Au (111) substrate. It was found that STM was unsuitable to obtain a obvious image of dendrimers. Tapping-mode atomic force microscopy(AFM) has been used to investigate the shape and size of dendrimers individually dispersed on Au (111)substrate. As a result, the imaged single dendrimer show that dendrimer is dome shaped and its size can be measured by tapping-mode AFM.