• The Journal of Korean Academy of Prosthodontics
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• v.53 no.2
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• pp.120-127
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• 2015

Purpose: The aim was to investigate the effect of implant thread designs on the stress dissipation of the implant. Materials and methods: The threads evaluated in this study included the V-shaped, buttress, reverse buttress, and square-shaped threads, which were of the same size (depth). Building four different implant/bone complexes each consisting of an implant with one of the 4 different threads on its cylindrical body ($4.1mm{\times}10mm$), a force of 100 N was applied onto the top of implant abutment at $30^{\circ}$ with the implant axis. In order to simulate different osseointegration stages at the implant/bone interfaces, a nonlinear contact condition was used to simulate immature osseointegration and a bonding condition for mature osseointegration states. Results: Stress distribution pattern around the implant differed depending on the osseointegration states. Stress levels as well as the differences in the stress between the analysis models (with different threads) were higher in the case of the immature osseointegration state. Both the stress levels and the differences between analysis models became lower at the completely osseointegrated state. Stress dissipation characteristics of the V-shape thread was in the middle of the four threads in both the immature and mature states of osseointegration. These results indicated that implant thread design may have biomechanical impact on the implant bed bone until the osseointegration process has been finished. Conclusion: The stress dissipation characteristics of V-shape thread was in the middle of the four threads in both the immature and mature states of osseointegration.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.4
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• pp.308-314
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• 2010

Purpose: The purpose of this study is to analyze the change in re-osseointegration over time and bone reaction at the interface between implant fixture and the surface of the bone, after destroying re-osseointegration by distorting the bone-implant interface artificially. Materials and methods: Experimental implant fixtures (cp titanium, ${\phi}3.75\;mm{\times}4\;mm$) which didn't have surface treatment were produced. Two or three fixtures were implanted on both tibias of twelve female rabbits (New Zealand white, more than 3.5 kg). Then after six weeks, removal torque (RT) was measured and the results were recorded as the first measurement values. The fixtures were submerged again to get reosseointegration between the bone and fixture. To identify the change in re-osseointegration of submerged fixtures over time, six groups had the healing time for four days (group I), one week (group II), two weeks (group III), three weeks (group IV), four weeks (group V) and five weeks (group VI), and then the secondary removal torque was measured for each group. To identify the bone formation under fluorescent light, tetracycline (15 mg/kg, IM) were treated on the rabbits of each group. After the second measurement, the rabbits were sacrificed, and 16 slides were made, two or three for each group. The slides were observed under the fluorescent light with light microscope. To find out the change in the secondary removal torque over the primary removal torque in progress of time, the averages of the increase rate of the primary and secondary torque removal force were calculated. Then, to find out if there were any critical differences between the primary removal torque and the secondary removal torque in each group and among the groups, the results were analyzed statistically by paired t- test, one-way ANOVA, and Duncan's Multiple Range Test. Results: In group I and II, secondary removal torque decreased, especially in group I. In group III, IV, V, and VI, secondary removal torque increased critically. Comparing the differences among the groups, the critical difference was shown between group I, II and group III, IV, V, VI. Mineralization at the interface between the bone and implant fixture was identified from the first week, and bone formation was shown more clearly from the second week. Conclusion: If the implant fixture remains unforced for a certain period of time after the fixture has had iatrogenic mobility, re-osseointegration occurs at the surface of the fixture, and for tibias of rabbits, higher re-osseointegration was obtained within two weeks.

• 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.

• Journal of Periodontal and Implant Science
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• v.26 no.3
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• pp.579-589
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• 1996

이 연구의 목적은 치주질환에 이환된 성견의 치근을 활택술 후 발치와에 이식하였을 때 calcium sulfate 골이식이 치근흡수와 치근유착을 지연시키는가를 알아보고자 하는 것이다.성견의 제2, 제3 소구치 주위의 치조골을 제거하여 분지부를 노출시키고, 8주간 교정사를 결찰하여 실험적 만성치주염을 유발하였다. 치관을 제거하고, 치근을 반분하고, 활택한 후 발치하였다. 발치된 치근을 둘로 나누어 각각을 우측에는 calcium sulfate와 함께, 좌측에는 이식재 없이 이식하였다. 12주간의 치유 후 조직학적으로 관찰하였다. 대조군에서는 흠의 치관쪽으로 치근흡수와 치근유착이 일어났고, 실험군에서는 성견 결합조직과 calcium sulfate가 위치하였던 공간이 관찰 되었고 치근흡수는 지연되었다. 이 연구에 나타난 바에 의하면, 치근 이식시 calcium sulfate 의 사용은 치조골로부터의 육아조직을 배제하고 치근흡수와 치근유착을 지연할 수 있는 것으로 생각된다.

• Journal of Periodontal and Implant Science
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• v.27 no.2
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• pp.395-409
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• 1997

성견의 2면 골내낭에서 calcium sulfate 이식이 치조골 및 백악질 재생 능력과 접합상피의 근단이동에 미치는 영향에 대해 알아보고자 3마리 성견의 상하악 제3대구치 근심면을 연결하는 깊이 4mm, 너비 4mm의 2면 골내낭을 외과적으로 형성하고 calcium sulfate를 이식한 군을 시험군으로, 치은박리술만을 실시한 군을 대조군으로 설정하였다. 술후 8주후에 치유결과를 접합상피의 길이, 백악질 형성, 치조골 형성, 결합조직 유착으로 나누어 조직학적으로 비교 관찰하여 다음과 같은 결과를 얻었다. 1. 접합상피의 길이는 대조군에서 2.28mm, 실험군에서 0.51mm로 나타났으며, 대조군과 실험군간에 유의성 있는 차이가 있었다(p<0.05). 2. 백악질 형성은 대조군에서 1.33mm, 실험군에서 2.59mm로 나타났으며, 대조군과 실험군간에 유의성 있는 차이가 있었다(p<0.05). 3.치조골 형성은 대조군에서 1.02mm, 실험군에서 2.30mm로 나타났으며, 대조군과 실험군간에 유의성 있는 차이가 있었다(p<0.05). 4. 결합조직 유착은 대조군에서 0.50mm, 실험군에서 1.14mm로 나타났으며, 대조군과 실험군간에 유의성 있는 차이가 있었다(p<0.05). 이상의 결과를 본 실험상의 한계내에서 고려하여 볼 때, calcium sulfate는 2면 골내낭의 치주치료에 치조골 및 백악질 재생 효과가 있으며 안전하고 경제적인 골 이식재 재료로 사용될 수 있으리라 사료된다.

• 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 Periodontal and Implant Science
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• v.33 no.3
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• pp.439-455
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• 2003

연구목적 : SLA surface dental implant 주위의 3면 골내낭에서 xenogeneic demineralized bone matric putty, porous ${\beta}$-tri-calcium phosphate, 새로이 개발된 non-crystalline calcium phosphate glass를 사용한 치료를 조직학적으로 비교 평가하기 위한 것이다. 연구방법 : 실험동물로는 15개월에서 18개월 사이의 12kg에서 15kg 정도되는 성견을 사용하였다. 20개의 SLA surface implant가 사용되었으며, 성견 하악의 양측에 각각 2개씩 사용되었다. 임플란트 식립전에, 각각의 임플란트 근심면에 straight fissure bur를 이용하여 표준화된 3면 골내앙(근원심 5mm ${\times}$협설 3mm ${\times}$깊이 3mm)을 형성하였다. 형성된 골 결손부에는 demineralized bone matrix putty, porous ${\beta}$-tri-calcium phosphate, non-crystalline calcium phosphate glass를 넣은 것을 각각 실험군으로, 이식재를 넣지 않은 것을 대조군으로 사용하였다. 8주 후에 실험 동물을 희생시키고 조직학적 관찰을 하였다. 결과 : 조직학적 소견상 임플란트 주위에 급성 염증 소견은 보이지 않았으며, non-crystalline calcium phosphate glass은 매우 적은량의 신생골을, ${\beta}$-TCP을 이용한 골내낭에서는 약간의 기저부에서 유래된 신생골이 관찰된다. ${\beta}$-TCP granules 가운데로 상당량의 측면의 골에서 유래된 신생골 형성이 보인다. xenogeneic DBM putty에서는 많은 량의 신생골이 기저부에 형성된 것을 볼수 있으나 대조군과의 차이는 크지 않다. 이식재의 종류와 상관없이 흡수되지 않은 이식재를 임플란트 주위에서 관찰할 수 있었다. 골내낭 안의 이식재들은 모두 connective tissue로 둘러 싸여 있었다. 모든 실험군에서 이식재에서 기인한 신생골 형성과 임플란트 표면에 신생 골유착의 조직학적 증거는 발견되지 않았다.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.3
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• pp.319-326
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• 2012

For many years, ceramics have been used in fixed prosthodontics for achieving optimal esthetics. but, they have another use as well. Many studies today show ceramics can be used for biomaterials. In the beginning researchers made a start in the study of aluminium oxide and sapphire for biomaterial. The appearance of Zirconia began a new phase of research. Zirconia was introduced into implantology as an alternative to titanium, because of its white color, good mechanical properties and superior biocompatibility. But it is not easy to surface treatment in comparison with titanium. To overcome the limitation, interconnected porous bodies of zirconia were fabricated by sintering technique. And the technique of coating was developed. Therefore, some zirconia implants are currently available. It is thought that Research of biomaterials as a variety of puposes for the use of zirconia is looking very promising. The purpose of this paper reviews are to evaluation of zirconia as biomaterials.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.729-733
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• 2004

Tooth avulsion usually causes inflammatory root resorption and ankylosis, and ankylosis cause severe functional and esthetic problems, especially in childhood. A 7-year-old female visited the Dept. of Pediatric Dentistry, Yonsei University with the chief complaint of avulsive trauma to the upper right incisor which was left dry for 40 minutes. Tooth was irrigated with saline and replanted immediately and splinted. Anti bacterial agent and anti inflammatory agent were prescribed. After 4 months of replantation slight external root resorption and apical radiolucency was seen at radiographic examination, therfore pulp extirpation and calcium hydroxide($Vitapex^{TM}$) canal filling were carried out. After 16 months, root canal was filled with gutta-percha, and bleaching treatment was done. Treatment results were satisfactory both esthetically and functionally for 8 years and 5 months.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.1
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• pp.9-17
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• 2014

Purpose: The purpose of this study was to compare zirconia implants with titanium implants from the view point of biomechanical stability and histologic response on osseointegration when those were placed with xenograft materials. Materials and methods: Specimens were divided into two groups; the control group was experimented with eighteen titanium implants which had anodized surface and the experimental group was experimented with eighteen sandblasted zirconia (Y-TZP) implants. At the tibias of six pigs, implants were installed into bone defect sites prepared surgically and treated with resorbable membranes and bovine bone. Two pigs were sacrificed after 1, 4 and 12 weeks respectively. Each implant site was sampled and processed for histologic and histomorphometric analysis. The stability of implants was evaluated with a $Periotest^{(R)}$. And the interfaces between bone and the implant were observed with a scanning electron microscope. Results: In stability analysis there was no significant difference between Periotest values of the control group and the experimental group. In histologic analysis with a light microscope after 4 weeks, there was new bone formation with the resorption of bovine bone and the active synthesis of osteoblasts in both groups. In bone-implant contact percentage there was significant difference between both groups (P<.05). In bone area percentage there was no significant difference between both groups. In analysis of both groups with a scanning electron microscope there was a gap between bone and a surface at 4 weeks and it was filled up with bone formed newly at 12 weeks. Conclusion: When accompanied by xenograft using membrane, bone to implant contact percentage of zirconia implants used in this experiment was significantly less than that of the titanium implants by surface treatment of anodic oxidation. So, it is considered that the improvement of zirconia implant is needed through ongoing research on surface treatment methods for its practical use.