• 대한치과보철학회지
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• 제44권2호
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• pp.197-206
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• 2006

Statement of problem: One of common problems associated with single teeth dental implant prosthetic is the loosening of screws that retain the implants. Purpose: The maintenance of screw joint stability is considered a function of the preload achieved in the screw when the suggested initial tightening torque is applied. The purpose of this study was to investigate acquired preload after initial clamping torque for estimating screw joint stability. Material and methods: A comparative study on the effect of initial clamping of two types of implant systems with different connections was conducted Three dimensional non-linear finite element analysis is adopted to compare the characteristics of screw preloads and stress distributions between two different types of implant systems composed with abutment, screw, and fixture under the same loading and boundary conditions. Results: 1. When the initial clamping torque of 32Ncm was applied to the implant systems, all types of implants generated the maximum effective stress at the first helix region of screw. 2. Morse taper connection types of implants generate lower stress distributions compared to those by butt joint connection types or implants due to large contact surface between abutment and fixture. 3. The internal types of implant systems with friction grip type implant systems have higher resistance to screw loosening than that of the external types of implant systems since the internal types of implant systems generated larger preload than that generated by the external types for the same tightening moments.

• The Journal of Advanced Prosthodontics
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• 제3권4호
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• pp.190-195
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• 2011

PURPOSE. This study evaluated the initial stability of different implants placed above the bone level in different types of bone. MATERIALS AND METHODS. As described by Lekholm and Zarb, cortical layers of bovine bone specimens were trimmed to a thickness of 2 mm, 1 mm or totally removed to reproduce bone types II, III, and IV respectively. Three Implant system (Br${\aa}$nemark System$^{(R)}$ Mk III TiUnite$^{TM}$, Straumann Standard Implant SLA$^{(R)}$, and Astra Tech Microthread$^{TM}$-OsseoSpeed$^{TM}$) were tested. Control group implants were placed in level with the bone, while test group implants were placed 1, 2, 3, and 4 mm above the bone level. Initial stability was evaluated by resonance frequency analysis. Data was statistically analyzed by one-way analysis of variance in confidence level of 95%. The effective implant length and the Implant Stability Quotient (ISQ) were compared using simple linear regression analysis. RESULTS. In the control group, there was a significant difference in the ISQ values of the 3 implants in bone types III and IV (P<.05). The ISQ values of each implant decreased with increased effective implant length in all types of bone. In type II bone, the decrease in ISQ value per 1-mm increase in effective implant length of the Br${\aa}$nemark and Astra implants was less than that of the Straumann implant. In bone types III and IV, this value in the Astra implant was less than that in the other 2 implants. CONCLUSION. The initial stability was much affected by the implant design in bone types III, IV and the implant design such as the short pitch interval was beneficial to the initial stability of implants placed above the bone level.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제45권1호
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• pp.29-33
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• 2019

Objectives: Bone density seems to be an important factor affecting implant stability. The relationship between bone density and primary and secondary stability remains under debate. The aim of this study was to compare primary and secondary stability measured by resonance frequency analysis (RFA) between different bone types and to compare implant stability at different time points during 3 months of follow-up. Materials and Methods: Our study included 65 implants (BioHorizons Implant Systems) with 3.8 or 4.6 mm diameter and 9 or 10.5 mm length in 59 patients. Bone quality was assessed by Lekholm-Zarb classification. After implant insertion, stability was measured by an Osstell device using RFA at three follow-up visits (immediately, 1 month, and 3 months after implant insertion). ANOVA test was used to compare primary and secondary stability between different bone types and between the three time points for each density type. Results: There were 9 patients in type I, 18 patients in type II, 20 patients in type III, and 12 patients in type IV. Three implants failed, 1 in type I and 2 in type IV. Stability values decreased in the first month but increased during the following two months in all bone types. Statistical analysis showed no significant difference between RFA values of different bone types at each follow-up or between stability values of each bone type at different time points. Conclusion: According to our results, implant stability was not affected by bone density. It is difficult to reach a certain conclusion about the effect of bone density on implant stability as stability is affected by numerous factors.

• 대한치과보철학회지
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• 제41권5호
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• pp.617-625
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• 2003

Statement of problem : There are many studies focused on the effect of shape of futures on stress distribution in the mandibular bone. However, there are no studies focused on the effect of the abutment types on stress distribution in mandibular bone. Purpose : The purpose of this study is to investigate the effect of three different abutment types on the stress distributions in the mandibular bone due to various loads by performing finite element analysis. Material and method : Three different implant systems produced by Warantec (Seoul, Korea), were modeled to study the effect of abutment types on the stress distribution in the mandibular bone. The three implant systems are classified into oneplant (Oneplant, OP-TH-S11.5). internal implant (Inplant, IO-S11.5) and external implant (Hexplant, EH-S11.5). All abutments were made of titanium grade ELI. and all fixtures were made of titanium grade IV. The mandibular bone used in this study is constituted of compact and spongeous bone assumed to be homogeneous, isotropic and linearly elastic. A comparative study of stress distributions in the mandibular bone with three different types of abutment was conducted. Results : It was found that the types of abutments have significant influence on the stress distribution in the mandibular bone. It was due to difference in the load transfer mechanism and the size of contact area between abutment and fixture. Also the maximum effective stress in the mandibular bone was increased with the increase of inclination angle of load. Conclusion : It was concluded that the maximum effective stress in the bone by the internal implant was the lowest among the maximum effective stresses by other two types.

• 대한치과기공학회지
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• 제28권2호
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• pp.347-353
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• 2006

The Purpose of this study was to compare the distribution of implant fixtures according to length and diameter between screw-retained and cement-retained implant-supported fixed prosthesis and to asses whether prosthesis retained types affected the selection of size of implant fixtures. This study presents a follow-up 2,416 implant-supported fixed type prosthesis that have been screw retained or cemented retained for about 10 years in 14 dental clinics. Included in the study were 458 men and 397 women and implant fixtures used in this study were screw retained type 1,057 and 1,359 of cemented retained type. The statistical results among the diameter types of fixture by prosthesis retained type was no significant difference noted (P= 0.809) and there was significant differences was enough to among the lengths of fixture by prosthesis retained type (P= 0.020). However there were no significant difference among the fixture diameter types and length by prosthesis retained type (P= 0.486). So there was not affected to prostheis fixation mechanism for the size of implant fixtures.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 추계학술대회
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• pp.323-326
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• 1996

Dental implant is increasingly used to recover the mastication function of tooth. Several types of implant were designed to give an optimal stress distribution in surrounding bony regions. In this study, six types of implant were investigated using finite element method and it was studied i) how the variation of cortical bone thickness affects the stress distribution in surrounding bony regions depending upon implant types, ii) which type gives the best characteristics in the sence of stress distribution and stability. The hybrid-type implant with cylinder and screw gave the optimum properties in view of stability and response to the variation of cortical bone thickness.

• The Journal of Advanced Prosthodontics
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• 제10권5호
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• pp.388-394
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• 2018

PURPOSE. To measure axial displacement of different implant-abutment connection types and materials during screw tightening at the recommended torque by using a contact scanner for two-dimensional (2D) and three-dimensional (3D) analyses. MATERIALS AND METHODS. Twenty models of missing mandibular left second premolars were 3D-printed and implant fixtures were placed at the same position by using a surgical guide. External and internal fixtures were used. Three implant-abutment internal connection (INT) types and one implant-abutment external connection (EXT) type were prepared. Two of the INT types used titanium abutment and zirconia abutment; the other INT type was a customized abutment, fabricated by using a computer-controlled milling machine. The EXT type used titanium abutment. Screws were tightened at $10N{\cdot}cm$, simulating hand tightening, and then at the manufacturers' recommended torque ($30N{\cdot}cm$) 10 min later. Abutments and adjacent teeth were subsequently scanned with a contact scanner for 2D and 3D analyses using a 3D inspection software. RESULTS. Significant differences were observed in axial displacement according to the type of implant-abutment connection (P<.001). Vertical displacement of abutments was greater than overall displacement, and significant differences in vertical and overall displacement were observed among the four connection types (P<.05). CONCLUSION. Displacement according to connection type and material should be considered in choosing an implant abutment. When adjusting a prosthesis, tightening the screw at the manufacturers' recommended torque is advisable, rather than the level of hand tightening.

• 한국정밀공학회지
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• 제22권3호
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• pp.179-186
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• 2005

A comparative study of stress distributions in the maxillary bone with three different types of abutment was conducted. Finite element analysis was adopted to determine stress generated in the bone with the different implant systems with micro threads (Onebody type implant, Internal type implant, and External type implant). It was found that the types of abutments and the number of micro threads have significant influence on the stress distribution in the maxillary bone. They were due to the difference in the load transfer mechanism and the size of contact area between abutment and fixture. Also the maximum effective stress in the maxillary bone was increased with increasing inclination angle of load. It was concluded that the maximum effective stress in the bone was the lowest by the internal implant among the maximum effective stresses by other two types of implants and by appropriate number of micro threads, and that the specific number of micro thread was existed to decrease the maximum effective stress in the maxillary bone due to different implant systems and loading conditions.

• Journal of Periodontal and Implant Science
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• 제43권1호
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• pp.41-46
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• 2013

Purpose: The objective of this study was to evaluate the effect of microthreads on removal torque and bone-to-implant contact (BIC). Methods: Twelve miniature pigs for each experiment, a total of 24 animals, were used. In the removal torque analysis, each animal received 2 types of implants in each tibia, which were treated with sandblasting and acid etching but with or without microthreads at the marginal portion. The animals were sacrificed after 4, 8, or 12 weeks of healing. Each subgroup consisted of 4 animals, and the tibias were extracted and removal torque was measured. In the BIC analysis, each animal received 3 types of implants. Two types of implants were used for the removal torque test and another type of implant served as the control. The BIC experiment was conducted in the mandible of the animals. The $P_1-M_1$ teeth were extracted, and after a 4-month healing period, 3 each of the 2 types of implants were placed, with one type on each side of the mandible, for a total of 6 implants per animal. The animals were sacrificed after a 2-, 4-, or 8-week healing period. Each subgroup consisted of 4 animals. The mandibles were extracted, specimens were processed, and BIC was analyzed. Results: No significant difference in removal torque value or BIC was found between implants with and without microthreads. The removal torque value increased between 4 and 8 weeks of healing for both types of implants, but there was no significant difference between 8 and 12 weeks. The percentage of BIC increased between 2 and 4 weeks for all types of implants, but there was no significant difference between 4 and 8 weeks. Conclusions: The existence of microthreads was not a significant factor in mechanical and histological stability.

• 대한치과보철학회지
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• 제32권3호
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• pp.455-469
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• 1994

Regular radiographic examination has been considered an essential diagnositic method for osseointegrated dental implantation. This study investigated marginal bone loss through the measurement on periapical radiographs and changes in bone density through digital subtraction image radiographic method around 88 endoseous root-form dental implants in 43 human subjects. Four types of endosseous dental implants were investigated : Standard series, Mini series and Hex-lock system of Steri-Oss Dental implant system, and $Br{\aa}nemark$-type implant from 3i dental implant system, in a 3 month interval for a total period of 12 months. The results were as follows : 1. Rapid bone loss occurred in the first 3 months in all 4 groups, and the bone level stabilized at the first thread of the implant fixtures. Amount of bone loss for 12 months showed correlation with the length of the polished neck portion. 2. Most of the implant systems showed resorption of alveolar bone up to the polished neck portion although a long polished neck could delay the resolution. 3. Alveolar bone loss apical to the polished neck portion stabilized at the first thread of the fixtures with no correlation to either the time of exposure of the polished neck or types of implant systems. 4. No changes in bone density around the implant threads were observed throughout the experimental period. Bone density decreased at the marginal bone, and increased at the newly-formed alveolar crest. These results indicate that most of the alveolar bone loss occur within the first 12 months after installation of endosseous root-form dental implants resulting in the exposure of polished neck portions, and the bone level stabilizes thereafter at the first thread portions of the implant fixtures. The experimental period of 12 months seems insufficient for observing changes in bone density, and a long-term observation should be needed.