• 대한치과보철학회:학술대회논문집
• /
• 2004.04a
• /
• pp.78-78
• /
• 2004

• The Journal of Korean Academy of Prosthodontics
• /
• v.55 no.3
• /
• pp.251-257
• /
• 2017

Purpose: The purpose of this study was to evaluate whether the internal abutment length affected screw stability in an internal connection implant. Materials and methods: Twenty long internal connection implants (Replus system, $4.7{\times}11.5mm$) were selected for this investigation. Abutments were assigned to four groups depending on the length of the internal connection (abutments with internal lengths of 1, 2, 3, and 4 mm, respectively). Each implant fixture specimen was embedded in resin medium and connected to an abutment with an abutment screw. A load of 100 N, applied at an angle of $30^{\circ}$ to the long axis of the implant, was repeated for $1.0{\times}10^6$ cycles. Reverse torque values (RTV) were recorded before and after loading, and the change in RTV was calculated. Data were analyzed with the Kruskal-Wallis test. Results: The change in RTV was not significantly different among the groups (P>.05). Screw loosening and fractures were not observed in any groups, and joint stability was maintained. Conclusion: The internal length of the abutment may not significantly affect the degree of screw loosening.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.05a
• /
• pp.292-292
• /
• 2004

치과용 임플란트(Implant)란 상실된 자연치아를 대신하여 골 내에 매식하는 인공치근을 말한다. 임플란트는 인접 자연치아의 보호, 심미적 안정 등의 장점으로 인해 그 수요가 늘어나고 있으며, 단일치아 임플란트의 경우, 부분 무치악 환자들에게 있어서 우수한 치의학적 해법이 되어왔다. 대부분의 임플란트는 두 개 이상의 구성요소로 이루어져 있으며, 각각의 구성요소는 나사에 의해 결합되어 있다. 많은 연구결과를 통해, 임플란트의 나사 풀림 현상(Screw loosening)은 임플란트와 관련하여 가장 흔한 문제로 나타나고 있다.(중략)

• The Journal of Korean Academy of Prosthodontics
• /
• v.54 no.4
• /
• pp.387-392
• /
• 2016

Purpose: The aim of this study was to investigate the effects of grooved abutments on abutment screw loosening. Materials and methods: This study was conducted to evaluate the abutment screw loosening after 6 months for 50 patients (51 implants) treated at the department of Prosthodontics in Yonsei University Dental Hospital from March, 2015 to July, 2015. A control group with non-grooved abutment consists of 30 implants, and an experimental group with grooved abutment consists of 21 implants. Astra, Straumann, Implantium, Osstem system were used in the study. The abutments with loose screws cases after a period of 6 months has been investigated, with two kinds of measurements: 1) measuring the additional rotational angle on abutment during placement with the same force, 2) measuring the PTV on bucco-cervical area of implant crown. All data collected has been analyzed by normality test followed by Mann-Whitney test using SPSS program. Results: No complications were reported after 6 months for the 51 implants. Abutment screw loose and crown fracture have not been seen in the study groups. The data collected from the two measurements showed no significant differences between the two groups with P-value 0.576 (average= control group: $7.35^{\circ}$, experimental group: $4.75^{\circ}$) for the additional rotational angle measurement and with P-value 0.767 for PTV. Conclusion: There are no significant differences between the grooved and non-grooved abutment in screw stability. However, further studies with long-term followups and larger group of patients is needed in order to investigate the effects of grooved abutment on screw stability.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.35 no.3
• /
• pp.132-142
• /
• 2019

Purpose: The purpose of this finite element analysis study is to introduce the novel Lock screw system and analyze its mechanical property to see if it can prevent abutment screw loosening. Materials and Methods: The Lock screw is a component tightened on the inside of the implant abutment which applies compressive force to the abutment screw head. To investigate the effect, modeling was done using CAD program and it was analyzed by finite element analysis under various load conditions. First, the preload was measured according to the tightening torque of the abutment screw then it was compared with the theoretical value to verify the analytical model. The validated analytical model was then divided into those with no external load and those with 178 N, and the tightening torque of the lock screw was changed to 10, 20, 30 Ncm respectively to examine the property of stress distribution on the implant components. Results: Using Lock screw under various loading conditions did not produce equivalent stresses beyond the yield strength of the implant components. In addition, the axial load was increased at the abutment-abutment screw interface. Conclusion: The use of Lock screw does not exert excessive stress on the implant components and may increase the frictional force between the abutment-abutment screw interface, thus it is considered to prevent loosening of the abutment screw.

• Proceedings of the KSME Conference
• /
• 2005.11a
• /
• pp.173.2-173.2
• /
• 2005

• The Journal of Korean Academy of Prosthodontics
• /
• v.47 no.2
• /
• pp.125-135
• /
• 2009

Statement of problem: Loosening or fracture of the abutment screw is one of the common problems related to the dental implant. Generally, in order to make the screw joint stable, the preload generated by tightening torque needs to be increased within the elastic limit of the screw. However, additional tensile forces can produce the plastic deformation of abutment screw when functional loads are superimposed on preload stresses, and they can elicit loosening or fracture of the abutment screw. Therefore, it is necessary to find the optimum tightening torque that maximizes a fatigue life and simultaneously offer a reasonable degree of protection against loosening. Purpose: The purpose of this study was to present the influence of tightening torque on the implant-abutment screw joint stability with the 3 dimensional finite element analysis. Material and methods: In this study, the finite element model of the implant system with external butt joint connection was designed and verified by comparison with additional theoretical and experimental results. Four different amount of tightening torques(10, 20, 30 and 40 Ncm) and the external loading(250 N, $30^{\circ}$) were applied to the model, and the equivalent stress distributions and the gap distances were calculated according to each tightening torque and the result was analyzed. Results: Within the limitation of this study, the following results were drawn; 1) There was the proportional relation between the tightening torque and the preload. 2) In case of applying only the tightening torque, the maximum stress was found at the screw neck. 3) The maximum stress was also shown at the screw neck under the external loading condition. However in case of applying 10 Ncm tightening torque, it was found at the undersurface of the screw head. 4) The joint opening was observed under the external loading in case of applying 10 Ncm and 20 Ncm of tightening torque. 5) When the tightening torque was applied at 40 Ncm, under the external loading the maximum stress exceeded the allowable stress value of the titanium alloy. Conclusion: Implant abutment screw must have a proper tightening torque that will be able to maintain joint stability of fixture and abutment.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.31 no.1
• /
• pp.60-66
• /
• 2015

Screw loosening and screw fracture of abutment is one of most frequent mechanical complications in implant restoration. Fractured fragments in implant restoration like abutment and screw should be completely removed and the procedure needs minimal damage to the fixture of implant. In some cases, it could fail to remove fractured fragments and cause a lot of damage to the fixture of implant. These situations could render implant unusable at the worst. This article describes three different situations and simple techniques for successful removal of fractured fragments without damage of implants. The procedures used are described in this clinical report.

• The Journal of the Korean dental association
• /
• v.36 no.10 s.353
• /
• pp.704-704
• /
• 1998

• 대한치과보철학회:학술대회논문집
• /
• 2005.11a
• /
• pp.91-91
• /
• 2005