• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.4
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• pp.403-415
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• 2009

The purpose of the study is to establish the effect of different abutment shapes and types of cements on the retention of the full veneer casted gold crowns. Metal dies that has the similar shape with the implant abutment were manufactured using a short(5mm) and long(10mm) dies with different convergence angles. Metal dies and gold crowns, which were made from the metal dies, were cemented with Temp-bond, Temp-bond mixed with petroleum jelly, ZPC and Premier implant cement. After that, these were tested for tensile force at the point of separation. The effect of convergence angle changes of different cement types on the retention was studied as well as the effects of the cement type changes with different convergence angles on the retention. In addition, study about the marginal gap of Premier implant cement used for this experiment was conducted. The results are as followed under the in-vitro experimental limits; 1. The retention of the Temp-bond mixed with petroleum jelly decreased as the convergence angle increased, and the retention was weakest among the cements. 2. The retention of ZPC decreased as convergence angle increased. When convergence angle was 5 degrees, ZPC showed stronger retention than Premier implant cement. 3. Premier implant cement had the weakest retention when the convergence angle was 5 degrees but when the convergence angle was 10 degrees, it had the strongest retention. As the angle increased more than 10 degrees, the retention decreased. 4. Premier implant cement showed bigger marginal gap when the convergence angle was 5 degrees than 10 degrees under the experimental condition.

• Journal of Periodontal and Implant Science
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• v.51 no.4
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• pp.285-295
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• 2021

Purpose: The aims of the present study were 1) to quantitatively evaluate the extent of sinus pneumatization and 2) to determine the factors affecting sinus pneumatization. Methods: Based on implant treatment records, a list of patients who underwent implant placement on the posterior maxilla was obtained. Among them, patients with pre-extraction and post-extraction (before implant placement) panoramic radiographs were selected. After excluding radiographs with low resolution and image distortion, the radiographs before and after extraction were superimposed using computer software. Subsequently, the extent of sinus pneumatization (the vertical change of the sinus floor) was measured. Simple and multiple mixed models were used to determine the factors affecting sinus pneumatization. Results: A total of 145 patients were eligible for the present investigation. The average extent of sinus pneumatization was 1.56±3.93 mm at 176 tooth sites. Male sex, single tooth extraction, extraction of an endodontically compromised tooth, a class I root-sinus relationship, and sinus membrane thickening >10 mm favored pneumatization, but without statistical significance. The maxillary second molar presented the greatest pneumatization (2.25±4.39 mm) compared with other tooth types. This finding was confirmed in the multiple mixed model, which demonstrated a statistically significant impact of the extraction of a second molar compared with the extraction of a first premolar. Conclusions: Maxillary sinus pneumatization was 1.56±3.93 mm on average. The extraction of a second molar led to the greatest extent of pneumatization, which should be considered in the treatment plan for this tooth site.

• 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.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.6
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• pp.628-633
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• 2008

STATEMENT OF PROBLEM: The application of a simple, clinically applicable noninvasive test to assess implant stability are considered highly desirable. So far there is still a controversy about correlation of various tests and implant stability. PURPOSE: In order to assess implant stability, the development of a new method is critical. It's possible to assess implant stability by calculating energy and angular momentum during implant installation. The purpose of this study is to evaluate the correlation of energy and implant stability. MATERIAL AND METHODS: Twenty three implants were installed in two different types of pig bone. Type I bone was retrieved from the distal aspect of the rib, with more cortical bone. Type II bone came from a more proximal region with less cortical components and a higher content of bone marrow and spongeous trabeculae. Insertion torque, removal torque, ISQ values and angular momentum and energy were measured. Pearson Correlation test was done to analyze the relation between RFA, maximum insertion torque, mean insertion torque, bone type, energy and removal torque. RESULTS: Type I bone showed higher removal torque than type II bone. Energy value was significantly correlated with maximum insertion torque and mean insertion torque. RFA values were related with insertion torques but the significance was lower than Energy value. CONCLUSION: Within the limitation of this study energy values were considered clinically predictable method to measure the implant stability.

• The Journal of Advanced Prosthodontics
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• v.9 no.1
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• pp.14-21
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• 2017

PURPOSE. The aim of this study was to compare the retention of mini implant overdenture by the number, the type of magnetic attachment, and the directions of applied dislodging force. MATERIALS AND METHODS. The experimental groups were designed by the number and type of magnetic attachment. Twenty samples were tested with Magden implants. Each attachment was composed of the magnet assembly in overdenture sample and the abutment keeper in a mandibular model. Dislodging forces were applied to the overdenture samples (50.0 mm/min) in 3 directions. The loading was repeated 10 times in each direction. The values of dislodging force were analyzed statistically using SPSS at 95% level of confidence. RESULTS. The retentive force of group 2 was greater than that of group 1 in both types of attachment in every direction (P < .05). Oblique retentive force of flat type magnetic attachment was higher than that of cushion type attachment in both groups (P < .05). In group 1, oblique retentive force showed the highest and anterior-posterior retentive force showed the lowest value in both attachment types (P < .05). In group 2, both types of attachment showed the lowest retentive force with anterior-posterior direction of dislodging force (P <.05). CONCLUSION. Proper retentive properties for implant overdenture were obtained, regardless of the number and type of magnetic attachment. In both types of magnetic attachment, the greater retentive force was attained with more implants. Oblique retentive force of flat type magnetic attachment was greater than that of cushion type. Among all subgroups, anterior-posterior retentive force was the lowest among three different directions of dislodging force.

• The Journal of Advanced Prosthodontics
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• v.1 no.1
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• pp.19-25
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• 2009

STATEMENT OF PROBLEM. Primary stability at the time of implant placement is related to the level of primary bone contact. The level of bone contact with implant is affected by thread design, surgical procedure and bone quality, etc. PURPOSE. The aim of this study was to compare the initial stability of the various taper implants according to the thread designs, half of which were engaged to inferior cortical wall of type IV bone(Group 1) and the rest of which were not engaged to inferior cortical wall(Group 2) by measuring the implant stability quotient(ISQ) and the removal torque value(RTV). MATERIAL AND METHODS. In this study, 6 different implant fixtures with 10 mm length were installed. In order to simulate the sinus inferior wall of type IV bone, one side cortical bone of swine rib was removed. 6 different implants were installed in the same bone block following manufacturer s recommended procedures. Total 10 bone blocks were made for each group. The height of Group 1 bone block was 10 mm for engagement and that of group 2 was 13 mm. The initial stability was measured with ISQ value using Osstell $mentor^{(R)}$ and with removal torque using MGT50 torque gauge. RESULTS. In this study, we found the following results. 1. In Group 1 with fixtures engaged to the inferior cortical wall, there was no significant difference in RTV and ISQ value among the 6 types of implants. 2. In Group 2 with fixtures not engaged to the inferior cortical wall, there was significant difference in RTV and ISQ value among the 6 types of implants(P < .05). 3. There was significant difference in RTV and ISQ value according to whether fixtures were engaged to the inferior cortical wall or not(P < .05). 4. Under-drilling made RTV and ISQ value increase significantly in the NT implants which had lower RTV and ISQ value in Group 2(P < .05). CONCLUSIONS. Without being engaged to the inferior cortical wall fixtures had initial stability affected by implant types. Also in poor quality bone, under-drilling improved initial stability.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.327-353
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• 1994

This study was performed to evaluate the effects of number and alignment of implant fixture and various bar designs on the retention of denture and the stress distribution. Six kinds of photoelastic mandibular models and nine kinds of overdenture specimens were designed. A unilateral vertical load was gradually applied on the right first molar to calculate the maximal dislodgement load of each specimen. A unilateral vertical load of 17 Kgf was applied on the right first molar and a vertical load of 10 Kgf was applied on the interincisal edge region. The stress pattern which developed in each photoelastic model was analyzed by the reflection polariscope. The results obtained were as follows: 1. The maximal dislodgement load reversely increased with the distance from the loading point to the implant fixture, while it linearly increased with that from the most posterior implant fixture to the mesial clip. The maximal dislodgement load also increased with the use of a cantilever bar. 2. Under the posterior vertical load, the stress to the supporting tissue of the denture base increased with the distance from the loading point to the implant future. The stress concentration on the apical area of the implant future reversely increased with the distance from the loading point to the implant future. 3. In the overdentures supported by two implant fixtures under the posterior vertical load. the specimen implanted on lateral incisor areas with a cantilever bar exhibited more favorable stress distribution than that without a cantilever bar. The specimen implanted on the canine areas without a cantilever bar, however, exhibited more favorable stress distribution. 4. In the overdentures supported by three implant fixtures. the specimen implanted ell the midline and canine areas exhibited more favorable stress distribution than that implanted oil the midline and the first premolar areas. 5. In the overdentures supported by four implant fixtures. the specimen implanted with two adjacent implant fixtures exhibited more favorable stress distribution than that implanted at equal distance under the posterior vertical load. 6. Under the anterior vertical load, the overdentures supported by three implant fixtures exhibited stress concentration on the supporting structure of the middle implant future. In overdentures supported by two or four implant futures, no significant difference was noted in stress distribution between the types of bars. These results indicate that the greater the number of implant fixtures, the better the stress distribution is. A favorable stress distribution may be obtained in the overdentures supported by two or three implant fixtures, if the location and the design of the bar are appropriate.

• The Journal of Advanced Prosthodontics
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• v.12 no.6
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• pp.351-360
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• 2020

PURPOSE. The aim of the present study was to compare the stress distributions on the dental implants, abutments, and bone caused by different overdenture attachment types under functional chewing forces. MATERIALS AND METHODS. The 3D finite element models of the mandible, dental implants, attachment types, and prostheses were prepared. In accordance with a conventional dental implant supported overdenture design, the dental implants were positioned at the bone level in the canine teeth region bilaterally. A total of eight models using eight different attachment systems were used in this study. All the models were loaded to simulate chewing forces generated during the centric relationship (450 N), lateral movement (400 N), protrusive movement (400 N), and also in the presence of a food mass unilaterally (200 N). Stress outputs were obtained as the maximum principal stress and the equivalent von-Mises stress. RESULTS. In all attachment types, higher stress values were observed in the abutments, dental implants, and bone in the magnet attachments in different loading conditions. The highest stress values were observed among the magnet systems in the components of the Titanmagnetics model in all loading conditions (stresses were 15.4, 17.7, and 33.1 MPa on abutment, dental implant, and bone, respectively). The lowest stress value was observed in the models of Zest and O-Ring attachments. CONCLUSION. The results of the present study implied that attachment types permitting rotation and tolerating various angles created lower stresses on the bone, dental implants, and abutments.

• Tribology and Lubricants
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• v.37 no.4
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• pp.136-143
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• 2021

This paper presents the loosening behavior that occurs after the application of an external load to internal and external connection types of dental implants using the finite element method. We use fastening force between an abutment and a fixture to clamp the dental implant system; however, loosening and breakage may occur owing to cyclic external loads. In this study, we considered the initial fastening condition in the pre-load analysis and then investigated the change in stress and contact surface status when applying external loads. After the application of the initial fastening load, we verified that the internal connection-type model exhibited a relatively lower stress distribution than that of the external connection-type one. Moreover, we found that the former model showed a lower stress concentration after the application of the external load. In addition, after the application of this load, we found that the higher the shear load acting on the implant system, the higher the possibility of loosening. The study results showed the change in stress distribution and contact surface according to the connection type of the dental implants and the phenomenon of loosening by cyclic loads. We expect that the results of this study will be useful for the study of reliability and design of dental implant systems.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.35 no.4
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• pp.248-252
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• 2009

Purpose: This retrospective study was performed to analyze the relationship between complications of the posterior mandibular single crowns and distance from the adjacent teeth to the implant. Subjects and Methods: Of the patients who presented Ewha Womans University Mokdong Hospital & Yonsei University Dental Hospital with missing of the posterior mandibular molar and restored with implant-supported 18 Single crowns between 1996 thru 2007, 115 patients had been followed after crown delivery. The subjects were divided into complication-followed group and a control without any problems. The distance from the most distal tooth to the implant were measured. The prosthetic & biologic complications were reviewed by the cantilever distance and analyzed by abutment type, age & gender statistically using SAS version 9.1 (SAS Inc., USA). Results and Conclusion The results were as follows; 1) The posterior mandibular single crown with cantilever showed higher incidence of follow-up complications upon logistic analysis (p<0.05). 2) The prosthetic and biologic complications are related with the cantilever distance with 2.1 odds ratio and 3.39 cut-off value of specificity & sensitivity by SPSS 12.0. 3) The complications are neither significant in abutment types nor age & gender.