• Wind and Structures
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• v.16 no.6
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• pp.561-577
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• 2013

Rational Functions are used to express the self-excited aerodynamic forces acting on a flexible structure for use in time-domain flutter analysis. The Rational Function Approximation (RFA) approach involves obtaining of these Rational Functions from the frequency-dependent flutter derivatives by using an approximation. In the past, an algorithm was developed to directly extract these Rational Functions from wind tunnel section model tests in free vibration. In this paper, an algorithm is presented for direct extraction of these Rational Functions from section model tests in forced vibration. The motivation for using forced-vibration method came from the potential use of these Rational Functions to predict aerodynamic loads and response of flexible structures at high wind speeds and in turbulent wind environment. Numerical tests were performed to verify the robustness and performance of the algorithm under different noise levels that are expected in wind tunnel data. Wind tunnel tests in one degree-of-freedom (vertical/torsional) forced vibration were performed on a streamlined bridge deck section model whose Rational Functions were compared with those obtained by free vibration for the same model.

• Journal of Periodontal and Implant Science
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• v.39 no.3
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• pp.339-348
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• 2009

Purpose: The purpose of the present study was to analyze the implant stability quotient(ISQ) values for Korean non-submerged type implant and determine the factors that affect implant stability. Methods: A total of 49 Korean non-submerged type implants were installed in 24 patients, and their stability was measured by resonance frequency analysis(RFA) at the time of surgery, and 1, 2, 3, 4, 8, 12 weeks postoperatively. The data for implant site, age, sex, implant length and diameter, graft performing, bone type, and insertion torque were analyzed. Results: The lowest mean stability measurement was at 3 weeks. There was significant difference between implant placement and 12 weeks. There was significant difference between implant placement and 12 weeks in diameters of 4.1 mm and 4.8 mm. Also, there were significant differences between diameters of 4.1 mm and 4.8 mm at implant placement and 12 weeks after surgery. This result suggests that the factor related to implant diameter may affect the level of implant stability. No statistically significant relationship was found between the resonance frequency analysis and the variables of maxilla/mandible, sex, anterior/posterior, implant length, age of patient, graft performing, bone type, insertion torque during initial healing period. Conclusions: These findings suggest that the factor related to implant diameter may affect the variance of implant stability, and ISQ value of implant was stable enough for proved stability level during initial healing period.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.33 no.4
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• pp.391-396
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• 2007

The aim of this study was to evaluate implant stability placed in the maxillary sinus which was augmented with bovine bone mineral(Bio-$Oss^{(R)}$) mixed with autogenous bone from the maxillary tuberosity. Maxillary sinus floor augmentation with the mixture of bovine bone mineral and autogenous maxillary tuberosity bone was performed in 30 maxillary sinuses, and 68 implants were placed at the time of sinus graft. After 6 months of implant placement abutments were connected and implant stability quotient(ISQ) was measured by radio frequency analysis(RFA). In addition, bone level changes was evaluated by taking periapical radiograph. During surgical procedures, no complication was observed, and all patients healed uneventfully. At 6 months the implant showed stable ISQ values. The marginal bone level changes around the fixtures was stably maintained through out the follow up period. This study confirmed that maxillary sinus floor augmentation with mixture of bovine bone mineral and maxillary tuberosity bone could be reliable for bone regeneration in subantral space.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.8
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• pp.3567-3570
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• 2014

Background: Hepatocellular carcinoma (HCC) is one of the most common cancers in men and the third most common cancer in woman in Thailand. This retrospective study was designed to assess the prevalence, clinical manifestations, treatment outcomes and prognosis of HCC in the central region of Thailand. Materials and Methods: The authors retrospectively reviewed all HCC patients aged more than 15 years old in Thammasat university hospital (TUH) during the period from January 2007 to December 2012. Clinical information, biochemical tests and radiologic findings were collected from review of medical records. Results: There were 308 patients with HCC, which accounted for the prevalence of 5.19% of all cancers diagnosed in TUH during the study period. Of these, 125 (40.5%) had complete information retrievable from their medical records and met the inclusion criteria, 99 (79.2%) were males. The mean age was 57.4 years. A quarter of HCC patients in this study presented without any symptom before diagnosis. The common clinical presentations in the remaining patients were hepatomegaly 64/125 (51.2%), abdominal pain 56/125 (44.8%) and ascites 16/125 (20.8%). Cirrhosis was seen in almost all patients (92.8%). The most common causes of HCC in this study were chronic hepatitis B (49.6%) and C (19.2%). Based on Barcelona Clinic Liver Cancer staging, 75.4% presented at intermediate or late stage. Patients receiving curative therapy with either surgical treatment or radiofrequency ablation had significantly longer survival time after the HCC diagnosis than the palliative therapy group (11.0 months vs 4.0 months, p value= 0.004). The mean survival time after the HCC diagnosis was 10.5 months. Conclusions: The common causes of HCC in central region of Thailand were chronic hepatitis B and C. Surgical therapy or RFA seemed to provide better outcomes than other treatments but only in patients with early stage lesions. Most of the patients in this study presented with advanced diseases and had grave prognosis. Appropriate screening patients at risk for HCC might be an appropriate way to achieve early diagnosis and improve the treatment outcome.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.487-497
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• 2005

Purpose: Resonance frequency analysis (RFA) , a non-invasive technique for the clinical measurement of implant stability, was investigated. Peri-implant bony defect may contribute to implant failure. This in vitro study evaluated the resonance frequencies according to various bony defects and determined whether the directional bone defect can affect the value of frequency analysis. Material and Method: Fifteen 3.75 mm in diameter and 10 mm in length, machined self-tapping implant future were used. Twelve types of bone defects that have different horizontal and vertical dimensions were simulated. Embedded implants were attached to the dental surveyor. Then, the transducer was connected with the implant fixture and the ISQ value was measured at four different directions. Two-way analysis of variance and post hoc $Sch\`{e}ffe'$ test were performed at the 95% significance level. Results: The control group showed the highest ISQ value and 5 thread-$360^{\circ}$ group had the lowest one. As the vertical exposure of implants in each angle was increased, the ISQ value was decreased. Although the horizontal exposure in each thread was increased, the ISQ value was not significantly decreased. Conclusion : Although the simulated defect type was different from each other, the ISQ value was similar among groups.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.6
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• pp.671-678
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• 2004

Statement of problem. Reducing treatment time in implant dentistry is a matter of main concern. There are so many factors affecting the success rate of immediate or early loaded implant for the initial bone response. The especially microscopic properties of implant surfaces playa major role in the osseous healing of dental implant. Purpose. The aims of this study were to perform a histologic and histomorphometric comparison of the healing characteristics anodically roughened surface, HA coated surface and RBM surface implant, and to compare of ISQ values measured by $Osstell^{TM}$ for resonance frequency analysis in dogs mandible during 2 weeks. Material and method. Bone blocks from 2 dogs were caught after covered healing for 0 day(2 h); Group I, 1 week; Group II and 2 weeks; Group III. One longitudinal section was obtained for each implant and stained with hematoxylin and eosin. Histomorphometric analysis was done with Kappa Imagebase system to calculate bone-to-implant contact and bone volumes inside the threads. ISQ values were measured in every time of surgery schedule. Conclusion. The experiment revealed that: 1. The percentages of bone-to-implant contact on the fixture in each group were not significantly different(P > 0.05). 2. The percentages of bone area inside the threads on the fixture in each group were not significantly different(P > 0.05). 3. The ISQ level showed clinical stability of each fixture during 2 weeks(all ISQ level ${\geq}71$ ).

• Journal of Periodontal and Implant Science
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• v.39 no.2
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• pp.185-192
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• 2009

Purpose: The aim of this study was to examine the correlation of the subjective and the objective evaluation of edentulous ridge bone quality, and to evaluate the change of the dental implant stability in each bone density group for early healing period after implant installation. Methods: Sixty-seven implants(Osstem implant$^{(R)}$, Seoul, Korea) were included in this study. We evaluated the bone density by 2 methods. The one was the subjective method which was determined by practitioner s tactile sense, the other was the objective bone type was based on Hounsfield units. The implant stability in each bone type group was assessed by resonance frequency analyzer(Osstell mentor$^{(R)}$). Data were analyzed for the change of the implant stability, and they were compared to verify the difference of groups at the time of installation, 2, 6, 10, 14 weeks postoperatively. Spearman's correlation was used to demonstrate the correlation between the subjective and the objective evaluation of the bone density, and analysis of variance(ANOVA) was used to analyze the differences of implant stability at each time point. Results: There was no close relation between the subjective and the objective evaluation of the bone density(r=0.57). In the subjective groups, there was statistically significant difference between the type 1 and 3 at 10 weeks and between the type 2 and 3 at 14 weeks. In the objective groups, there was no statistically significant difference between the D 1, 2, 3, 4, and 5 group with regard to RFA from baseline to 14 weeks(P>0.1). Conclusions: The implant stability increased over time during the study, and it was improved with bone density proportionally after 2weeks postoperatively. It is recommended that the decision of bone density is base on Hounsfield unit for implant loading time.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.30 no.6
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• pp.518-528
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• 2008

Purpose: The long-term experience of using osseointegrated implants for prosthetic rehabilitation of the edentulous patients shows that high success rates can be predictably achieved. Primary implant stability has been identified to be a prerequisite to achieve osseointegration. In this study, we set up the amount of removed bone so that it differed on implant installation site for each group. The influence of each initial stability on secondary stability and osseointegration was compared with time lapse using resonance frequency analysis and histomorphometric analysis. Materials and methods: A total 27 US $II^{(R)}$ (Osstem, Korea) implants were placed in the mandibular edentulous area of 3 beagle dogs. The implant site was prepared by the conventional technique with drills, and three experimental groups were divided into under-drilling group, normal-drilling group and over-drilling group. The Implant Stability Quotient (ISQ) was measured at intervals of immediately, 4, 8, 12 weeks after placement using $Osstell^{(R)}$ mentor RFA. After the animals were sacrificed, histomorphometric evaluation was executed for measuring BIC and BD. Results: 1) The under-drilled group showed most high ISQ value for whole experiment period. 2) Bone-to-implant-contact(BIC) showed the tendency to be increased gradually as the experiment period passed except the 8 weeks of the normal group. 3) The under-drilled group showed most high bone density(BD) level for whole experiment period, and it was expressed the aspect to be increased gradually according to an experiment period passage in the average of all group. 4) Resonance frequency analysis and histomorphometric analysis are presumed by generally proportional. Conclusions: As this research result, it seems that there are some correlation between resonance frequency analysis and histomorphometric analysis. As are accomplished osseointegration stably so that more superior at the region which the overpressure comes to add, it will be applicable method in clinical field.

• The Journal of Advanced Prosthodontics
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• v.1 no.1
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• pp.10-18
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• 2009

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, $2^{nd}$ 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 $54.5{\pm}8.4%$. The mean BIC % in the turned implant was $45.3{\pm}12.2%$. 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.

• Computers and Concrete
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• v.30 no.6
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• pp.393-407
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• 2022

Due to the enormous cement content, pozzolanic materials, and the use of different aggregates, sustainable controlled low-strength material (CLSM) has a higher material cost than conventional concrete and sustainable construction issues. However, by selecting appropriate materials and formulations, as well as cement and aggregate content, whitethorn costs can be reduced while having a positive environmental impact. This research explores the desire to optimize plastic properties and 28-day unconfined compressive strength (UCS) of CLSM containing powder content from unprocessed-fly ash (u-FA) and recycled fine aggregate (RFA). The mixtures' input parameters consist of water-to-cementitious material ratio (W/CM), fly ash-to-cementitious materials (FA/CM), and paste volume percentage (PV%), while flowability, bleeding, segregation index, and 28-day UCS were the desired responses. The central composite design (CCD) notion was used to produce twenty CLSM mixes and was experimentally validated using MATLAB by an Artificial Neural Network (ANN). Variance analysis (ANOVA) was used for the determination of statistical models. Results revealed that the plastic properties of CLSM improve with the FA/CM rise when the strength declines for 28 days-with an increase in FA/CM, the diameter of the flowability and bleeding decreased. Meanwhile, the u-FA's rise strengthens the CLSM's segregation resistance and raises its strength over 28 days. Using calcareous powder as a substitute for cement has a detrimental effect on bleeding, and 28-day UCS increases segregation resistance. The response surface method (RSM) can establish high correlations between responses and the constituent materials of sustainable CLSM, and the optimal values of variables can be measured to achieve the desired response properties.