Early loading의 난제 stability dip, 어떻게 극복할 것인가?

박창주(Chang-Joo Park) 대한치과의사협회 2013 대한치과의사협회지 Vol.51 No.4

Nowadays, it seems like that the concept of the early loading protocol has been intruded between the concept of the immediate loading supported by advanced clinicians and the concept of the conventional loading supported by the prudent clinicians. In particular, the stability dip, which is found to occur usually at 4~6 weeks after dental implant placement because the decrease of the primary mechanical stability is not compensated by the increase of the secondary biologic stability, is frequently pointed out as one of the major causes of early loading failure. In this article, based on our recent clinical investigation about the crestal bone preservation effect of the early loaded NanoTite™ Tapered Certain Prevail (Biomet 3i, USA), the concept of the early loading is revisited. In addition, various methods to overcome the stability dip are reviewed as the oral and maxillofacial surgeon’s view point.

Histomorphometry and stability analysis of early loaded implants with two different surface conditions in beagle dogs

Dong-Seok Kim,Dae-Gon Kim,Chan-Jin Park,Lee-Ra Cho 대한치과보철학회 2009 The Journal of Advanced Prosthodontics Vol.1 No.1

STATEMENT OF PROBLEM. Despite an improved bone reactions of Mg-incorporated implants in the animals, little yet has been carried out by the experimental investigations in functional loading conditions. PURPOSE. This study investigated the clinical and histologic parameters of osseointegrated Mg-incorporated implants in early loading conditions. MATERIAL AND METHODS. A total of 36 solid screw implants (diameter 3.75 mm, length 10 mm) were placed in the mandibles of 6 beagle dogs. Test groups included 18 Mg-incorporated implants. Turned titanium implants served as control. Gold crowns were inserted 4 weeks after implant placement and the dogs were immediately put on a food diet. Implants were observed for 10 weeks after loading. Radiographic assessments and stability tests were performed at the time of fixture installation, 2nd stage surgery, 4 weeks after loading, and 10 weeks after loading. Histological observations and morphometrical measurements were also performed. RESULTS. Of 36 implants, 33 displayed no discernible mobility, corresponding to successful clinical function. There was no statistically significant difference between test implants and controls in marginal bone levels (P = .46) and RFA values. The mean BIC % in the Mg-implants was 54.5 ± 8.4%. The mean BIC % in the turned implant was 45.3 ± 12.2%. These differences between the Mg-implant and control implant were statistically significant (P = .005). CONCLUSIONS. The anodized, Mg-incorporated implant demonstrated significantly more bone-to-implant contact (BIC) in early loading conditions. CLINICAL IMPLICATIONS. The results of this study in beagle dogs suggest the possibility of achieving predictable stability of early loaded free-standing dental implants with Mg-incorporated surface.

Transient heat transfer analysis using Galerkin finite element method for reinforced concrete slab exposed to high elevated temperature

한병찬,권영진,이병재,Seung-Jun Kwon,채영석 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.18 No.6

Fire loading causes a critical collapse of RC (Reinforced Concrete) Structures since the embedded steels inside are relative week against high elevated temperature. Several numerical frameworks for fire resistance have been proposed, however they have limitations such as unstable convergence and long calculation period. In the work, 2-D nonlinear FE technique is proposed using Galerkin method for RC structures under fire loading. Closed-form element stiffness with a triangular element is adopted and verified with fire test on three RC slabs with different fire loading conditions. Several simulations are also performed considering fire loading conditions, water contents, and cover depth. The proposed numerical technique can handle time-dependent fire loading, convection, radiation, and material properties. The proposed technique can be improved through early-aged concrete behavior like moisture transport which varies with external temperature.

Effect of fiber reinforcing on instantaneous deflection of self-compacting concrete one-way slabs under early-age loading

Behnam Vakhshouri,Shami Nejadi 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.2

The Early-age construction loading and changing properties of concrete, especially in the multi-story structures can affect the slab deflection, significantly. Based on previously conducted experiment on eight simply-supported one-way slabs this paper investigates the effect of concrete type, fiber type and content, loading value, cracking moment, ultimate moment and applied moment on the instantaneous deflection of Self-Compacting Concrete (SCC) slabs. Two distinct loading levels equal to 30% and 40% of the ultimate capacity of the slab section were applied on the slabs at the age of 14 days. A wide range of the existing models of the effective moment of inertia which are mainly developed for conventional concrete elements, were investigated. Comparison of the experimental deflection values with predictions of the existing models shows considerable differences between the recorded and estimated instantaneous deflection of SCC slabs. Calculated elastic deflection of slabs at the ages of 14 and 28 days were also compared with the experimental deflection of slabs. Based on sensitivity analysis of the effective parameters, a new model is proposed and verified to predict the effective moment of inertia in SCC slabs with and without fiber reinforcing under two different loading levels at the age of 14 days.

Effect of fiber reinforcing on instantaneous deflection of self-compacting concrete one-way slabs under early-age loading

Vakhshouri, Behnam,Nejadi, Shami Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.2

The Early-age construction loading and changing properties of concrete, especially in the multi-story structures can affect the slab deflection, significantly. Based on previously conducted experiment on eight simply-supported one-way slabs this paper investigates the effect of concrete type, fiber type and content, loading value, cracking moment, ultimate moment and applied moment on the instantaneous deflection of Self-Compacting Concrete (SCC) slabs. Two distinct loading levels equal to 30% and 40% of the ultimate capacity of the slab section were applied on the slabs at the age of 14 days. A wide range of the existing models of the effective moment of inertia which are mainly developed for conventional concrete elements, were investigated. Comparison of the experimental deflection values with predictions of the existing models shows considerable differences between the recorded and estimated instantaneous deflection of SCC slabs. Calculated elastic deflection of slabs at the ages of 14 and 28 days were also compared with the experimental deflection of slabs. Based on sensitivity analysis of the effective parameters, a new model is proposed and verified to predict the effective moment of inertia in SCC slabs with and without fiber reinforcing under two different loading levels at the age of 14 days.

밀폐형 자외선 광조사 임플란트의 공진 주파수 분석과 조기부하: 증례보고

설현우,박규화,허정욱,손병섭,김승수 대한구강악안면임플란트학회 2017 대한구강악안면임프란트학회지 Vol.21 No.2

Ultraviolet (UV) irradiation enhances the biologic activity of titanium surface without the change of surface topography. UV treated titanium surface is very hydrophilic and chemically clean with low carbon composition on its surface. Also, surface charge of titanium surface is changed from negative to positive by UV treatment. Implants with sealed UV treatment system, were inserted in fresh extraction socket and maxillary molar area with simultaneous sinus elevation. The changes in implant stability quotient (ISQ) values were favorable, and early loading protocol was accepted. In other cases, UV treated implants were loaded one week after installation, and their ISQ values were recorded periodically. UV treated implants showed stable stability even after the loading.

Comparative Study of the Early Loading of Resorbable Blasting Media and Sandblasting with Large-grit and Acid-etching Surface Implants: A Retrospective Cohort Study

Kim, Sung-Beom,Kim, Young-Kyun,Kim, Su-Gwan,Oh, Ji-Su,Kim, Byung-Hoon Korean Association of Maxillofacial Plastic and Re 2014 Maxillofacial Plastic Reconstructive Surgery Vol.36 No.6

Purpose: This study compares the prognosis (the survival rate and marginal bone loss) of resorbable blasting media (RBM) surface implants and sandblasting with large-grit and acid-etching (SLA) surface implants in the early loading. Methods: This study targeted 123 patients treated by implants installation from January 2008 to March 2010. The loading was initiated in the maxilla within three to four months and in the mandible within one to two months. The types of restoration were single crown and fixed partial prosthesis. Those functioned over one year. The implants were classified by the surface of implants as Group 1: RBM surface (GS III; OSSTEM, Busan, Korea) and, Group 2: SLA surface (Superline; Dentium, Seoul, Korea). The groups were categorized by maxilla and mandible and compared by survival rate, marginal bone loss through clinical records evaluation, and radiographic measurements. Results: The marginal bone loss in the maxilla was $0.14{\pm}0.34mm$ (Group 1) and $0.30{\pm}0.37mm$ (Group 2), a statistically significant difference (P<0.05). In the mandible those were $0.28{\pm}0.54mm$ (Group 1) and $0.20{\pm}0.33mm$ (Group 2), not significant (P>0.05). There was no significant difference of marginal bone loss between maxilla and mandible by groups. During observation there was no implant failure, a survival rate of 100%. Conclusion: Both surfaces showed an excellent survival rate, and the marginal bone loss was not substantial.

초기 재령 철근콘크리트 보의 구조 실험을 통한 동바리 되세우기 안전성 평가

천성철(Chun, Sung-Chul),소광호(Sho, Kwang-Ho),이성호(Lee, Sung-Ho) 대한건축학회 2015 大韓建築學會論文集 : 構造系 Vol.31 No.3

Significant concerns of reshores lie in their safety when shores are being replaced while the construction load of the upper floor is applied. Reinforced concrete (RC) beams at early ages were tested to investigate the concerns. Tests on cylinder specimens showed that the compressive strengths and elastic moduli of early-age concrete are reliably predicted using the equations in KCI code and, therefore, the nominal strength and stiffness can also be predicted for RC beams with ages other than 28 days. The RC beams of 2 or 3 days old showed a shear-compression failure and the RC beams of 7 or more days old showed a typical flexural behavior. Because the shear strength of RC beams is more affected by the compressive strength of concrete than their flexural strength is, the shear capacity needs to be checked in case of reshoring. Tests also found that beam-column joints have sufficient stiffness even at early ages and the joints can be safely assumed to be fully restrained regardless of the concrete age. From the test results, it was drawn that reshoring at 5 days of concrete pouring is safer than keeping the shores by 55%.

콘크리트 포장의 교통저방을 위한 강도기준에 관한 연구

Duongdarashy Chheun,김영규,이승우 한국도로학회 2024 한국도로학회 학술대회 발표논문 초록집 Vol.2024 No.03

The strength criteria is the acceptable strength for allowable a vehicle start on a concrete pavement at an early age without causing significant damage. The different agencies have provided the strength criteria based on empirical judgement. To make more comprehensive, the ACI specification provided strength criteria by consideration traffic conditions, slab thicknesses, and slab support based on the concept of damage. However, its neglected to consider the damage caused by curling stress due to temperature gradient in concrete pavement. This research aims to provide a strength criteria for opening traffic on concrete pavements while taking into account the damage caused by curling stress and traffic loading. The tensile stress at critical locations was determine due to curling and traffic loads every hour of early age throughout different seasons. The fatigue damage taken throughout early age was assessed. After this procedure, the strength criteria was established as the evaluated damage that did not exceed an acceptable limit. Accordingly, the strength criteria for opening traffic was determined to ensure that the specified damage level existed subject to the construction season, construction period, traffic type, slab thickness, and slab support of concrete pavement.

초기 재령 철근콘크리트 보의 구조 실험을 통한 동바리 되세우기 안전성 평가

천성철,소광호,이성호,하태훈 대한건축학회 2015 대한건축학회논문집 Vol. No.

<P> Significant concerns of reshores lie in their safety when shores are being replaced while the construction load of the upper floor is applied. Reinforced concrete (RC) beams at early ages were tested to investigate the concerns. Tests on cylinder specimens showed that the compressive strengths and elastic moduli of early-age concrete are reliably predicted using the equations in KCI code and, therefore, the nominal strength and stiffness can also be predicted for RC beams with ages other than 28 days. The RC beams of 2 or 3 days old showed a shear-compression failure and the RC beams of 7 or more days old showed a typical flexural behavior. Because the shear strength of RC beams is more affected by the compressive strength of concrete than their flexural strength is, the shear capacity needs to be checked in case of reshoring. Tests also found that beam-column joints have sufficient stiffness even at early ages and the joints can be safely assumed to be fully restrained regardless of the concrete age. From the test results, it was drawn that reshoring at 5 days of concrete pouring is safer than keeping the shores by 55%. </P>