• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.3
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• pp.189-198
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• 2017

Purpose: This study aims to analyze the stress distribution of mandibular molar restoration supported by the implants with external hex and internal taper abutment connection design. Materials and Methods: Models of external connection (EXHEX) and internal connection (INCON) implants, corresponding abutment/crowns, and screws were developed. Supporting edentulous mandibular bony structures were designed. All the components were assembled and a finite element analysis was performed to predict the magnitude and pattern of stresses generated by occlusal loading. A total of 120 N static force was applied both by axial (L1) and oblique (L2) direction. Results: Peak von Mises stresses produced in the implants by L2 load produced 6 - 15 times greater than those by L1 load. The INCON model showed 2.2 times greater total amount of crown cusp deflection than the EXHEX model. Fastening screw in EXHEX model and upside margin of implant fixture in INCON model generated the peak von Mises stresses by oblique occlusal force. EXHEX model and INCON model showed the similar opening gap between abutment and fixture, but intimate sealing inside the contact interface was maintained in INCON model. Conclusion: Oblique force produced grater magnitudes of deflection and stress than those by axial force. The maximum stress area at the implant was different between the INCON and EXHEX models.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.38
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• pp.42.1-42.7
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• 2016

Background: The purpose of this retrospective study was to evaluate the clinical utility of an implant with a sandblasted, large-grit, acid-etched (SLA) surface and internal connection. Methods: Six patients who received dental implants in the Department of Oral and Maxillofacial Surgery, Chonnam National University Dental Hospital, were analyzed by factors influencing the success rate and marginal bone loss. Factors included patient's age, sex, implant installation site, whether bone graft was done, type of bone graft materials, approaching method if sinus lift was done, and the size of the fixture. In addition, the marginal bone loss was analyzed by using a radiograph. Results: All implants were successful, and the cumulative survival rate was 100 %. Average marginal bone loss of 6 months after the installation was 0.52 mm and 20 months after the functional loading was 1.06 mm. Total marginal bone resorption was 1.58 mm on average. There was no statistically significant difference in mesial and distal marginal bone loss. Conclusions: The short-term clinical success rate of the implant with an SLA surface and internal connection was satisfactory. Moreover, the marginal bone loss was also consistent with the implant success criteria.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.486-491
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• 2004

A comparative study on the implant screw loosening under the initial clamping force and cyclic loads was conducted. The experiments were performed to evaluate the screw loosening behavior of the internal and external implant systems. It was found that the screw loosening torques of implant systems were significantly affected by the way how the abutment and fixture were connected due to the difference in the load transfer mechanism between abutment and fixture.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.2
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• pp.81-91
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• 2002

Dental implant systems have shown many post-surgical problems and One of the most frequent problem is screw loosening. To reduce screw loosening, a number of methods have been tried and recently fundamental modification of fixture-abutment connection structure was developed and used the most frequently. Former implant system structure, such as Br${\aa}$nemark, had external hex with the height of 0.7 mm and later, fixture with external hex of 1.0 mm height and internal hex structure were developed. In addition, the method of morse taper application was introduced to reduce screw loosening. In this study, the level of screw loosening of each implant systems was compared based on the vibration loosening measurement of abutment screw of each implant systems. Analysis of measured value was performed using 3 kinds of methods, (i) Percentage of average of initial 3 times loosening-torque value(initial loosening value) to tightening-torque of 30 Ncm, (ii) Percentage of loosening-torque value after 200 N strength loaded(experimental value) to initial loosening value and (iii) Percentage of experimental value to 30 Ncm of tightening-torque. Each result of analyses shows the value of initial loosening, loosening by repetitive load and final loosening level. The results of this study were as follows. (1) Percentage of initial loosening value to tightening-torque was increased in order of 0.7 mm external hex, 1.0 mm external hex, internal hex and internal taper and all values between each groups showed statistical significance (p<0.05). (2) Percentage of experimental value to initial loosening value was increased in order of internal hex, 0.7 mm external hex, 1.0 mm external hex and internal taper. Value of internal taper showed significant difference with that of 0.7 mm external hex and internal hex (p<0.05). (3) Percentage of experimental value to tightening torque was increased in order of 0.7 mm external hex, 1.0 mm external hex, internal hex and internal taper. Values of all groups showed statistical significance (p<0.05) except between the groups of 1.0 mm external hex and internal hex. Based on those results, there was no significant difference of loosening-torque by repetitive loading except internal taper. It is supposed that implant system with high resistant capability against initial loosening could be recommended for clinical use. In addition, in case of single implant restoration, 1.0 mm external hex or internal hex could be recommended rather than 0.7 mm external hex, and the use of internal taper would be the most useful way to reduce screw loosening.

• The Journal of Korean Academy of Prosthodontics
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• v.59 no.1
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• pp.126-133
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• 2021

Axial displacement of an implant-supported prosthesis is frequently reported in clinical and laboratory studies. However, limited information is available about the behavior of the axial displacement of implant-supported prostheses functioning in intraoral situations. The present case report evaluated the three-dimensional displacement of posterior single implant-supported prostheses in 2 different patients. Internal connection type implants were placed, and screw and cement-retained prosthesis (SCRP) type prosthesis were delivered after an appropriate healing period. Intraoral digital scans were performed using an intraoral scanner (Cerec Omnicam, Dentsply Sirona, USA) on the day of crown delivery and one week, one month, and one year after delivery. The amount of 3-dimensional displacement of the prosthesis was evaluated by using a digital inspection software (Geomagic Control X, 3D systems, USA). The axial displacement of implant-supported prosthesis occurred in both patients. Furthermore, the amount of displacement increased over time.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.3
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• pp.269-281
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• 2008

Fatigue or overload can result in mechanical problems of implant components. The mechanical strength in the implant system is dependent on several factors, such as screw and fixture diameters, material, and design of the fixture-abutment connection and abutment. In these factors, the last rules the strength and stability of the fixture-abutment assembly. There have been some previous reports on the mechanical strength of the fixture-abutment assembly with the compressive bending test or short-term cyclic loading test. However, it is restrictive to predict the long-term stability of the implant system with them. The purpose of this study was to evaluate the influence of the design of the fixture-abutment connection and abutment on the mechanical strength and failure mode by conducting the endurance limit test as well as the compressive bending strength test. Tests were performed according to a specified test(ISO/FDIS 14801) in 4 fixture-abutment assemblies of the Osstem implant system: an external butt joint with Cemented abutment (group BJT), an external butt joint with Safe abutment (group BJS), an internal conical joint with Solid abutment (group CJO), and an internal conical joint with ComOcta abutment (group CJT). The following conclusions were drawn within the limitation of this study. Compressive bending strengths were decreased in order of group BJS(1392.0N), group CJO(1261.8N), group BJT(1153.2N), and group CJT(1110.2N). There were no significant differences in compressive bending strengths between group BJT and group CJT(P>.05). Endurance limits were decreased in order of group CJO(600N), group CJT(453N), group BJS(360N), and group BJT(300N). 3. Compressive bending strengths were influenced by the connection and abutment design of the implant system, however endurance limits were affected more considerably by the connection design.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.4
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• pp.222-231
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• 2020

To use the external connection implant (EXT) appropriately, the inter-implant distance should be carefully considered during placement, and the bones raised above the implants should be trimmed during the second surgery. The hex abutment is more useful than the non-hex abutment. EXT is particularly useful when the inter-arch space is limited. The tissue level (TL, internal butt connection) implant has a biomechanical advantage of coronal wall thickness and a biological advantage of an inherent transmucosal smooth surface. During TL implant restoration, an abutment can be selected using the abutment and fixture margins with considerations for the inter-arch space. Since no single type of implant can satisfy all the cases, it is necessary to select the appropriate type, considering the occlusal force and the bone condition.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.2
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• pp.110-119
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• 2016

Purpose: This study is aimed to assess changes of stress distribution dependent on different connection lengths and placement of the fixture top relative to the ridge crest. Materials and methods: The internal-conical connection implant which has a hexagonal anti-rotation index was used for FEM analysis on stress distribution in accordance with connection length of fixture-abutment. Different connection lengths of 2.5 mm, 3.5 mm, and 4.5 mm were designed respectively with the top of the fixture flush with residual ridge crest level, or 2 mm above. Therefore, a total of 6 models were made for the FEM analysis. The load was 170 N and 30-degree tilted. Results: In all cases, the maximum von Mises stress was located adjacent to the top portion of the fixture and ridge crest in the bone. The longer the connection length was, the lower the maximum von Mises stress was in the fixture, abutment, screw and bone. The reduction rate of the maximum von Mises stress depending on increased connection length was greater in the case of the fixture top at 2 mm above the ridge crest versus flush with the ridge crest. Conclusion: It was found that the longer the connection length, the lower the maximum von Mises stress appears. Furthermore, it will help prevent mechanical or biological complications of implants.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.36 no.3
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• pp.116-123
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• 2014

Purpose: The purpose of this study was to evaluate risks for wound dehiscence after guided bone regeneration (GBR) in dental implant surgery. Methods: Patients who received dental implant therapy with GBR procedure at Seoul National University Bundang Hospital (Seongnam, Korea) from June 2004 to May 2007 were included. The clinical outcome of interest was complications related to dental implant surgery. The factors influencing wound dehiscence, classified into patient-related factors, surgery-related factors and material-related factors, were evaluated. Results: One hundred and fifteen cases (202 implants) were included in this study. Wound dehiscence (19.1%) was considered a major complication. The risk of wound dehiscence was higher in males than in females (odds ratio=4.279, P =0.014). In the main graft, the allogenic group had the lowest risk of wound dehiscence (odds ratio=0.106, P =0.006). Though the external connection group had a higher risk of wound dehiscence than the internal connection group (odds ratio=2.381), the difference was not significant (P =0.100). Conclusion: In this study, male gender and main graft have the highest risk of wound dehiscence. To reduce wound dehiscence after GBR, instructions on postoperative care with supplementary procedure for the protection of the wound dehiscence is recommended, especially to male patients. A main graft with a gel base can reduce the risk of wound dehiscence.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.49 no.1
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• pp.43-48
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• 2023

The biocompatibility and durability of implant fixtures are major concerns for dentists and patients. Mechanical complications of the implant include abutment screw loosening, screw fracture, loss of implant prostheses, and implant fracture. This case report aims to describe management of a case of fixture damage that occurred after screw fracture in a tissue level, internal connection implant and microscopic evaluation of the fractured fixture. A trephine bur was used to remove the fixture, and the socket was grafted using allogeneic bone material. The failed implant was examined by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), which revealed a fractured fixture with both normal and irregular bone patterns. The SEM and EDS results give an enlightenment of the failed fixture surface micromorphology with microfracture and contaminated chemical compositions. Noticeably, the significantly high level of gold (Au) on the implant surface and the trace amounts of Au and titanium (Ti) in the bone tissue were recorded, which might have resulted from instability and micro-movement of the implant-abutment connection over an extended period of time. Further study with larger number of patient and different types of implants is needed for further conclusion.