• The Journal of Korean Academy of Prosthodontics
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• v.44 no.4
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• pp.432-442
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• 2006

Statement of problem: One of common problems associated with dental implant is the loosening of abutment screws that retain the implants. Purpose : This study was performed to investigate the influence of abutment screw length and repeated tightening on screw loosening in dental implant. Material and method: Forty nine Hexplants (13mm length, 4.3mm diameter, Ti grade IV, Warantec. Co. Ltd. Seongnam, Korea) and cementation type abutments(straight abutment) and abutment screws (0.4mm/pitch) were divided into 7 groups, depending on abutment screw length. Each implant and abutment was tightened to 30Ncm by torque controller(MGT50, MARK-10 Inc., USA) and the removal torque values were measured during 10 consecutive closure/opening trials. Results and Conclusion: The results of comparing the removal torque value are as follows : 1. There is no significant difference in the removal torque value between groups in 10 consecutive closure/opening trials (p = 0.97). 2. If the fractured abutment screw is engaged in longer than 2.425 thread length, there is no significant difference in the preload between the fractured abutment screw and the new abutment screw when both are equally tightened to 30 Ncm. 3. The removal torque value in the 1st trial(24.510 Ncm) was lower than that in the 2nd, 3rd, 4th, 5th, 6th, 7th trials and the removal torque value in the 2nd trials(25.551 Ncm) was maximum and was decreased in 1311owing trials. The removal torque value in the 1st trial was significantly lower than that in the 2nd, 3rd, 4th trials and was significantly higher than that in the 8th, 9th, l0th trials(p<0.05). 4. In the 2nd, 3rd, 4th, 5th, 6th, 7th trials, the abutment screw was mainly influenced by settling effect and the higher preload was obtained In the 8th, 9th, l0th trials, the abutment screw was mainly influenced by adhesive wear and the progressively lower preload was obtained.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.45 no.1
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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.

• Journal of Periodontal and Implant Science
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• v.54 no.1
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• pp.44-52
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• 2024

Purpose: This study aimed to evaluate the clinical outcomes of a single type of narrow-diameter implant (NDI) by investigating its survival rate and peri-implant marginal bone loss (MBL). In addition, variables possibly related to implant survival and MBL were investigated to identify potential risk factors. Methods: The study was conducted as a retrospective study involving 49 patients who had received 3.0-mm diameter TSIII implants (Osstem Implant Co.) at Seoul National University Dental Hospital. In total, 64 implants were included, and dental records and radiographic data were collected from 2017 to 2022. Kaplan-Meier survival curves and a Cox proportional hazard model were used to estimate the implant survival rate and to investigate the effects of age, sex, jaw, implant location, implant length, the stage of surgery, guided bone regeneration, type of implant placement, and the surgeon's proficiency (resident or professor) on implant survival. The MBL of the NDIs was measured, and the factors influencing MBL were evaluated. Results: The mean observation period was 30.5 months (interquartile range, 26.75-45 months), and 6 out of 64 implants failed. The survival rate of the NDIs was 90.6%, and the multivariate Cox regression analysis showed that age was associated with implant failure (hazard ratio, 1.17; 95% confidence interval, 1.04-1.31, P=0.01). The mean MBL was 0.44±0.75 mm, and no factors showed statistically significant associations with greater MBL. Conclusions: NDIs can be considered a primary alternative when standard-diameter implants are unsuitable. However, further studies are required to confirm their long-term stability.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.49 no.1
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• pp.13-20
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• 2023

Objectives: Ultra-wide implants may be used as a replacement if existing implants fail. This study was conducted to evaluate the factors influencing the prognosis and failure of ultra-wide implants. Patients and Methods: This study evaluated whether sex, age, site, diameter, length, additional surgery, implant stability (primary and secondary), and reason for ultra-wide implant placement affect the 5-year survival and success rates and marginal bone loss (MBL) of ultra-wide implants. Seventy-eight ultra-wide implants that were placed in 71 patients (39 males and 32 females) from 2008 to 2010 were studied. One-way ANOVA analysis was conducted to evaluate the statistical significance of MBL according to the patient's sex, implant site, and diameter. Independent sample t-tests were used to determine the statistical significance of MBL analysis which was used to determine the significance of the 5-year success and survival rates related to the variables. One-way ANOVA was conducted to evaluate the statistical significance of sex, implantation site, diameter, and MBL. Independent sample t-tests were used to evaluate the correlation between implantability and MBL for implantation reasons, while additional surgery, length, and Kaplan-Meier analysis were used to evaluate 5-year survival and success rates. Results: The mean age of patients was 54.2 years with a survival rate of 92.3% and a success rate of 83.3% over a mean 97.8-month period of observation. MBL averaged 0.2 mm after one year of prosthetic function loading and 0.54 mm at the time of final observation. Success rates correlated with primary stability (P=0.045), survival rates correlated with secondary stability (P=0.036), and MBL did not correlate with any variables. Conclusion: Ultra-wide implants can be used to achieve secure initial fixation in the maxillary and mandibular molar regions with poor bone quality or for alternative purposes in cases of previous implant failure.

• Journal of Korean Dental Science
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• v.2 no.2
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• pp.31-34
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• 2009

The survival rate of the OSSTEM GS II Implant 1 year after serving the prosthetic function in 2 domestic and foreign medical institutes was 97.57%; the success rate was 95.7%, and the average alveolar bone resorption was 0.24mm(n=389). In particular, the alveolar bone resorption occurred differently according to the placement location as well as whether or not the patient underwent bone grafting operation, but the implant s length and diameter did not have significant impact on alveolar bone resorption.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.2
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• pp.149-153
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• 2011

Purpose: The aim of the present study was to evaluate the clinical outcome of resorbable blasting media surface tapered implant. Methods: 169 Osstem$^{(R)}$ GS III dental implants in 73 patients who received implant treatments at Seoul National University Bundang Hospital, were included in this study. The incidence of biological and prosthetical complications has been carefully analysed for each implant. Results: The short-term implant survival rate was 97.63%, success rate 94.7%. The prevalence of biological complications was 15.38% and the prevalence of prosthetic complications was 13.04%. The mean value of crestal bone loss was $0.28{\pm}0.57$ mm. The relationship between loading periods and marginal bone loss was small and not statistically significant. In mandible, marginal bone loss was larger than in maxilla, no statistically significant. Also, length and diameter of implant had no relationship with marginal bone loss. Conclusion: We suggest that this implant system could achieve successful and stable results.

• The Journal of the Korean dental association
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• v.38 no.6 s.373
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• pp.558-566
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• 2000

Osseointegrated dental implants have now become and accepted form of treatment for patients with a fully or partially missing dentition. The purpose of this study was to evaluate the performance of AVANA implant-Korea. A total of 323 AVANA implants were placed at 9 centers in the edentulous and partially edentulous jaws of 88 consecutive patients ranging in age form 18 to 79 years. So we get the clinical results. 1. Both patients (94.4%) & doctors (94%) were satisfied with the results, in patient's aspect 'most satisfaction' case were more common(52%) 2. The length of fixture which was frequently used was 13mm (168/319,44.5%) followed by 15mm and 10mm, and 3.75mm width implant (239/319,74.9%) was the most popularly used. 3. Mandibutar posterior was the most common installation site (140/317.43%) 4. A mean implant survival rate was 96.2%. That showed little difference which reported other paper. Cause of failure consisted of inflammation $ infection-36%, fall of osseointegration-18%, paln during masticatory function-9%. improper prosthetic function $ procedure-9%. 5. The most popularly used types of abutment was the UCLA abutment(168/305,55.5%)

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.36 no.2
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• pp.108-118
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• 2010

Introduction: Maxillary posterior region, compared to the mandible or maxillary anterior region, has a thin cortical bone layer and is largely composed of cancellous bone, and therefore, it is often difficult to achieve primary stability. In such cases, sinus elevation with bone graft is necessary. Materials and Methods: In this research, 121 patients who had implant placement after bone graft were subjected to a follow-up study of 5 years from the moment of the initial surgery. The total survival rate, 5-year cumulative survival rate and the influence of the following factors on implant survival were evaluated; the condition of the patient (sex, age, general body condition), the site of implant placement, diameter and length of the implant, sinus elevation technique, closure method for osseous window, type of prosthesis and opposing teeth. Results: 1. The 5-year cumulative survival rate of total implants was 90.5%, there was no significant difference between sex, age, the site of implant placement, diameter and length of the implant, sinus elevation technique, and the type of opposing teeth. 2. Patients with diabetes mellitus < osteoporosis and smooth-surfaced machined group < hydroxyapatite (HA)-treated group and homogenous demineralized freeze dried allogenic bone (DFDB) bone graft only group had significantly lower survival rate. 3. With less than 4 mm of residual alveolar ridge height, lateral approach without closing the osseous window resulted in a significantly lower survival rate. 4. Restoration of a single implant showed a significantly lower survival rate, compared to cases where the superstructure was joined with several implants in the area. Conclusion: Patients with diabetes or osteoporosis need longer period of time for osseointegration compared to the normal, and the dentists must be prudent when choosing a surface treatment type and the bone graft material. Also, as the vertical dimension of the residual alveolar ridge can influence the result, staged implant placement should be considered when it seems difficult for the implant to gain primary stability from the residual bone with less than 4 mm of vertical dimension. It is recommended to obdurate the bone window and that the superstructure be connected with several impants in the peripheral area.

• The Journal of Advanced Prosthodontics
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• v.8 no.2
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• pp.150-157
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• 2016

PURPOSE. The modified lateral-screw-retained implant prosthesis (LSP) is designed to combine the advantages of screw- and cement-retained implant prostheses. This retrospective study evaluated the mechanical and biological complication rates of implant-supported single crowns (ISSCs) inserted with the modified LSP in the posterior region, and determined how these complication rates are affected by clinical factors. MATERIALS AND METHODS. Mechanical complications (i.e., lateral screw loosening [LSL], abutment screw loosening, lateral screw fracture, and ceramic fracture) and biological complications (i.e., peri-implant mucositis [PM] and peri-implantitis) were identified from the patients' treatment records, clinical photographs, periapical radiographs, panoramic radiographs, and clinical indices. The correlations between complication rates and the following clinical factors were determined: gender, age, position in the jaw, placement location, functional duration, clinical crown-to-implant length ratio, crown height space, and the use of a submerged or nonsubmerged placement procedure. RESULTS. Mechanical and biological complications were present in 25 of 73 ISSCs with the modified LSP. LSL (n=11) and PM (n=11) were the most common complications. The incidence of mechanical complications was significantly related to gender (P=.018). The other clinical factors were not significantly associated with mechanical and biological complication rates. CONCLUSION. Within the limitations of this study, the incidence of mechanical and biological complications in the posterior region was similar for both modified LSP and conventional implant prosthetic systems. In addition, the modified LSP is amenable to maintenance care, which facilitates the prevention and treatment of mechanical and biological complications.

• Structural Engineering and Mechanics
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• v.74 no.4
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• pp.567-576
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• 2020

Considerable controversy surrounds the choice of the best abutment type for implant prosthetics. The two most common structures are hex and non-hex abutments. The non-hex abutment typically furnishes a larger contact area between itself and the implant than that provided by a hex structure. However, when a hex abutment is loaded, the position of its contact area may be deeper than that of a non-hex abutment. Hence, the purpose of this study is to determine the different biomechanical behaviors of an internal bone-level implant based on the abutment type-hex or non-hex-and clinical crown length under static and cyclic loadings using finite element analysis (FEA). The hex structure was found to increase the implant and abutment stability more than the nonhex structure among several criteria. The use of the hex structure resulted in a smaller volume of bone tissues being at risk of hypertrophy and fatigue failure. It also reduced micromovement (separation) between the implant components, which is significantly related to the pumping effect and possible inflammation. Both static and fatigue analyses, used to examine short- and long-term stability, demonstrated the advantages of the hex abutment over the non-hex type for the stability of the implant components. Moreover, although its impact was not as significant as that of the abutment type, a large crown-implant ratio (CIR) increased bone strain and stress in the implant components, particularly under oblique loading.