• The Journal of Korean Academy of Prosthodontics
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• v.48 no.3
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• pp.209-214
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• 2010

Purpose: The purpose of this study was to investigate whether the re-osseointegration of the implants that had mechanical unscrewing possibly occurred or not. Furthermore, if it happened, the degree of re-osseointegration was evaluated by comparing with previous osseointegration. Materials and methods: The smooth implant (commercial pure titanium 99%) specimens, whose diameter and length was 3.75 mm, 4 mm, respectively were produced. Two implants were inserted into each tibia of 7 New Zealand female white rabbits weighing at least 3.0 kg. The torque removal force for each implant after 6 weeks of implants placement was measured and included in group I. The torque removal forces were assessed after the fixtures were re-screwed to original position and the subjects were allowed to have 4 more weeks for healing and included in group II. One rabbit was sacrificed after first measurement and produced 4 slide specimens in group I, and two rabbits were sacrificed after 2nd measurement, 7 slide specimens, in group II for histomorphologic investigations. All slide specimens were assessed based on the proportion of BIC (bone-implant contact) as well as CBa (Bone area in the cortical passage) value produced by counting the screw threads embedded in the compact bones under the optical microscopic analysis (${\times}20$). Statistical analysis was conducted to evaluate the torque removal force, BIC and CBa between group I and II. Results: As for the torque removal force, the result was $10.8{\pm}3.6$ Ncm for group I and $20.2{\pm}9.7$ Ncm for group II. Furthermore, the torque removal force of group II increased by 98.1% in average compared to group I (P<.05). On the other hand, histomorphologic analysis displayed that there was no statistical significance in BIC and CBa values between group I and the group II (P>.05), and RT/BIC and RT/CBa between group I and group II were statistically significant (P<.05). Conclusion: It is possible to obtain more substantial re-osseointegration within shorter periods than the period needed for the initial osseointegration in case of iatrogenically unscrewed implants.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.2
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• pp.105-112
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• 2014

Purpose: The aim of present investigation was to find out the influence of several times iatrogenic mobilization in the initial stage of implant installation on bone-implant osteointegration. Materials and methods: The experimental implants (3.75 mm in diameter, 8.0 mm in length) were made of commercially pure (Grade IV) titanium, and were treated with RBM ($MegaGen^{(R)}$: Ca-P) on lower 4.0 mm part. Only lower part of implant was inserted to bone and the implants were nonsubmerged. The 130 implants (two in each tibia) were inserted into the monocortical tibias of 33 rabbits which each weighed more than 3.5 kg (Female, New Zealand White). According to the removal torque interval, the groups were divided into 13 groups, group I (1 day), group II (1 day + 2 days), group III (1 day + 2 days + 3 days), group IV (1 day + 2 days + 3 days + 4 days), group V (2 days), group VI (2 days + 4 days), group VII (2 days + 4 days + 6 days), group VIII (2 days + 4 days + 6 days + 8 days), group IX (4 days), group X (4 days + 7 days), group XI (4 days + 7 days + 10 days), group XII (4 days + 7 days + 10 days + 14 days) and control group. In the control group, the removal torque was measured at 8 weeks with a digital torque gauge (Mark-10, USA). In the experimental groups, the removal torque was given once, twice, three times or four times by experiment design before the final removal torque and the value was measured each time. The implants were then screwed back to their original positions. All the experimental groups were given a final healing time of 8 weeks after placement, in which values were compared with the control groups and the 1st, 2nd, 3rd or 4th removal torque values in each experimental group. Results: In comparison of the final removal torque tests among experimental groups, the removal torque value of experimental groups except group XII were not statistically different that of control group. And the values of group I and II were significantly higher than the values of group VI, VIII, X, XI, and XII. In addition, the values of group III, IV, and V were significantly higher than group XI and XII. In comparison of the removal torque in the each experimental group, the final removal torque were significantly higher in all groups except group VIII, X, XI, and XII. Conclusion: If sufficient healing time was allowed, a few mobilization of fixture at the very early stage after the implant placement in the rabbits didn't interrupt the final bone to implant osseointegration.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.3
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• pp.149-155
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• 2012

Purpose: The purpose of this study was to investigate the influence of mobilization on bone-implant interface prior to osseointegration of fixtures. Materials and methods: The experimental implants (3.75 mm in diameter, 4.0 mm in length) were made of commercially pure (Grade IV) titanium, and were treated with RBM ($MegaGen^{(R)}$: Ca-P). The 80 implants (two in each tibia) were inserted into the monocortical tibias of 20 rabbits which each weighed more than 3.5 kg (Female, New Zealand White). According to the removal torque interval, the groups were divided into 10 groups, Group I (6 wks), Group II (4 days+6 wks), Group III (4 days+1 wk+6 wks), Group IV (1 wk+6 wks), Group V (1 wk+1 wk+6 wks), Group VI (2 wks+6 wks), Group VII (2 wks+ 1 wk+6 wk), Group VIII (3 wks+6 wks), Group IX (3 wks+1 wk+6 wks) and Group X (10 wks). The control groups were Group I and X, the removal torque was measured at 6 wks and 10 wks with a digital torque gauge (Mark-10, USA). In the experimental groups, the removal torque was given once or twice before the final removal torque and the value was measured each time. After which, the implants were put back where they had been except the control groups. All the experimental groups were given a final healing time (6 wks) before the final removal torque test, in which values were compared with the control groups and the 1st and/or 2nd removal torque values in each experimental group. Results: In the final removal torque tests, the removal torque value of Group X (10 wks) was higher than that of Group I (6 wks) in the control groups but not statistically different. There were no significant differences between the experimental groups and control groups (P>.05). In the first removal torque comparison, the experimental groups (4 days or 1 wk) values were significantly lower than the other experimental groups (2 wks or 3 wks). In the comparison of each experimental group according to healing time, the final removal torque value was significantly higher than the 1st torque test value. Conclusion: Once or twice mobilization of fixture prior to osseointegration did not deter the final bone to implant osseointegration, if sufficient healing time was given.

• 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.27 no.2
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• pp.125-140
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• 2011

The remnant of temporary cement on the intaglio surface of cast restoration may have a negative effect on the retentive strength of permanent cement. This study was to evaluate the effect of temporary cement cleaning methods on the retentive strength of cementation type implant prostheses. Prefabricated implant abutments - height 5.5mm, diameter 4.5mm, 6 degree axial wall taper with chamfer margins were used. Forty copings-abutment specimens were divided into four groups(each n=10) according to the cleaning methods for temporary cement(Temp-$Bond^{(R)}$) as follows : no temporary cementation(the control group), orange solvent, ultrasonic cleaning, air borne-particle abrasion. After the application of temporary cement and the separation, the cleaning procedure was performed according to the protocol of each group. The specimens were cemented with $Premier^{(R)}$ Implant $Cement^{TM}$. After the permanent cementation, the specimens were subjected to thermocycling and pulled out from the specimens with a universal testing machine at a cross-head speed of 0.5mm/min. After the retentive strength test, all the specimens were cleaned using ultrasonic cleaning, abraded with air borne-particles, and steam-cleaned. Likewise, the specimens were temporarily cemented(Temp-$Bond^{(R)}$ NE), cleaned according to the protocol of each group, cemented with $Premier^{(R)}$ Implant $Cement^{TM}$ and subjected to thermocycling and measurement of their retentive strength. The mean of group with orange solvent were significantly lower than those of other groups(p<0.05). There was no significance between group with ultrasonic cleaning and group with air borne-particle abrasion. Group with ultrasonic cleaning and group with air-particle abrasion were no significance at control group. There was no significance between group cemented with Temp-$Bond^{(R)}$ and group cemented with Temp-$Bond^{(R)}$ NE. Within the limitation of this study, it can be concluded that the temporary cement cleaning method with only orange solvent may have a negative effect on the retentive strength of permanent cement. Ultrasonic cleaning and air borne-particle abrasion methods are recommended for the temporary cement cleaning method on cementation type implant prostheses.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.31 no.4
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• pp.330-333
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• 2009

Alveolar bone resorption after extraction impairs the necessary bone volume and complicates the case for implant surgery and aesthetic implant prosthesis. Immediate implant surgery after extraction decreases the number of surgical procedures and the duration of treatment, while allowing minimum alveolar bone resorption and preserving the residual bone volume. Although immediate implant holds many advantages such as preservation of hard and soft tissue around the extraction socket, greater implant survival rate and higher patient satisfaction, various complications and high failure rate are discouraging factors for the clinicians. In this case report, severe alveolar bone resorption with soft tissue changes were predicted after the extraction of prolonged retained deciduous incisors and impacted maxillary canines and thus decided on immediate implant procedure. Immediate implant surgery after extraction was carried out with minimal bone reduction and tapered wide-neck implant to establish initial stability. Simultaneous bone graft was done by filling the defect area with iliac cancellous bone with additional onlay-type bone graft and absorbable membrane on the labial bone for upper lip support. A stable and esthetic result was obtained with shortened treatment period.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.157-169
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• 2009

The aim of this study was to evaluate effect of implant abutment screw coating treatment on joint stability, investigating mechanical properties of these. For this study used $ExFeel^{(R)}$ external hexed implant system and $15mm{\times}1mm$ discs. Experimental group was $1{\mu}m$ TiN, TiCN, TiC coated abutment screws and discs. To know mechanical property, i evaluated adhesion strength, surface hardness, using disc, corrosion test using screw. The results were as follows : rotation angle of coated screws increased than that of non-coated screw because of lower friction coefficient, especially TiC coated screw group had the largest value, but removal torque decreased in all coated screws (p<0.05). Torque loss before and after fatigue test was the smallest in TiC-coated screws, and the largest in non-coated screws (p<0.05), and there was no statistically significant difference between dry condition and wet condition of screws because of higher surface hardness and lower friction coefficient. From the above results, TiN, TiCN, TiC coating group had high abrasion resistance, especially TiC coated group which had low torque-consuming, high rotation angle as low friction coefficient will be considered to influence on implant abutment screw joint stability positively.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.130-130
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• 2000

타이타늄(CP Ti)과 타？늄합금은 인체의 골격을 구성하고 있는 물질과 가장 흡사한 물리적 성질과 우수한 생체적합성으로 인해 임플란트용 재료로 많이 사용되고 있으며, 최근에 인공관절이나 치근으로의 사용이 증가하고 있다. 그러나 교합면에서의 취약한 마모특성으로 인해 wear debris에 의한 골 흡수 및 이완 등을 야기하는 문제점으로, 이의 개선에 관한 연구가 활발히 진행되어 왔다. 다이아몬드상 카본 (Diamond-Like-Carbon) 박막은, 다이아몬드와 유사한 높은 경도, 내마모성 그리고 화학적 안정성 등의 매우 우수한 물리화학적 특성을 가지고 있는 박막재료로 고체 윤활박막으로서 hard disk나 VCR head drum의 보호막, 우주항공기의 bearing 재료코팅 등으로의 적용이 최근에 급격히 증가하고 있다. 본 연구에서는 이와 같은 특성을 지닌 다이아몬드상 카본 박막의 생체재료로의 적용을 위해, CP Ti과 Ti-6Al-4V에 13.56MHz를 사용하는 r.f PACVD법으로 DLC를 증착하여 생체적합적 특성을 조사하였다. C6H6 가스를 사용하여 1$\mu\textrm{m}$의 두께로 DLC 박막을 증착하였으며, 기판과의 밀찰력 향상을 위해 Si을 증간층으로 합성하였다. 마모특성은 pin-on-disk type wear tester을 사용하였으며 직경 5mm의 ruby ball로 실험을 수행하였다.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.240-245
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• 2016

In this paper, stress contour plots depending on length, load, and diameter of the implant are presented. Depending on the condition and amount of cortical bone, process of implanting can be difficult and stress becomes important. Therefore deciding the right length and diameter of implant is critical. When analyzing stress in the implant, Von-mises yield criterion is often used; however, due to hardship of acquiring the actual material property of surrounding bones, simplified model of a implant was adapted in finite element analysis program of EDISON. The result acquired from EDISON program was then compared with results of different research papers.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.3
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• pp.245-253
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• 2011

Purpose: The aim of this in vitro study was to estimate surface characteristic after peptide coating and investigate biological response of human mesenchymal stem cell to anodized titanium discs coated with RGD peptide by physical adhesion and chemical fixation. Materials and methods: Fluorescence isothiocyanate (FITC) modified RGD-peptide was coated on the anodized titanium discs (diameter 12 mm, height 3 mm) using two methods. One was physical adhesion method and the other was chemical fixation method. Physical adhesion was performed by dip and dry procedure, chemical fixation was performed by covalent bond via silanization. In this study, human mesenchymal stem cell was used for experiments. The experiments consisted of surface characteristic evaluation after peptide coating, analysis about cell adhesion, proliferation, differentiation, and mineralization. Obtained data are statistically treated using Kruskal-Wallis test and Bonferroni test was performed as post hoc test (P=.05). Results: The evaluation of FE-SEM images revealed no diffenrence at micro-surfaces between each groups. Total coating dose was higher at physical adhesion experimental group than at chemical fixation experimental group. In cell adhesion and proliferation, RGD peptide coating did not show a statistical significance compared with control group (P>.05). In cell differentiation and mineralization, physical adhesion method displayed significantly increased levels compared with control group and chemical fixation method (P<.05). Conclusion: RGD peptide coating seems to enhance osseointegration by effects on the response of human mesenchymal stem cell. Especially physical adhesion method showed more effective than chemical fixation method on response of human mesenchymal stem cell.