1,721,226 research outputs found
Reality of dental implant surface modification: A short literature review
No full textScrew-shaped endosseous implants that have a turned surface of commercially pure titanium have a disadvantage of requiring a long time for osseointegration while those implants have shown long-term clinical success in single and multiple restorations. Titanium implant surfaces have been modified in various ways to improve biocompatibility and accelerate osseointegration, which results in a shorter edentulous period for a patient. This article reviewed some important modified titanium surfaces, exploring the in vitro, in vivo and clinical results that numerous comparison studies reported. Several methods are widely used to modify the topography or chemistry of titanium surface, including blasting, acid etching, anodic oxidation, fluoride treatment, and calcium phosphate coating. Such modified surfaces demonstrate faster and stronger osseointegration than the turned commercially pure titanium surface. However, there have been many studies finding no significant differences in in vivo bone responses among the modified surfaces. Considering those in vivo results, physical properties like roughening by sandblasting and acid etching may be major contributors to favorable bone response in biological environments over chemical properties obtained from various modifications including fluoride treatment and calcium phosphate application. Recently, hydrophilic properties added to the roughened surfaces or some osteogenic peptides coated on the surfaces have shown higher biocompatibility and have induced faster osseointegration, compared to the existing modified surfaces. However, the long-term clinical studies about those innovative surfaces are still lacking. © In-Sung Yeo; Licensee Bentham Open.Y
진공단열재의 열융착 테두리를 통한 가스 투과도 특성에 관한 연구
No full text학위논문(석사) - 한국과학기술원 : 기계공학전공, 2011.2, [ viii, 52 p. ]Not only outstanding insulation performance but also the extended service lifetime is required in vacuum insulation panels (VIPs). Thermal insulation performance of VIPs is degraded with time due to deterioration of the inner vacuum. The main causes are gas permeation and out-gassing in VIPs. Especially, gas permeation in the lateral through heat-sealed flanges has the largest effect. It is thus necessary to investigate the permeation characteristics of the envelope seal materials (linear low density polyethylene, LLDPE, and low density polyethylene, LDPE). A measurement apparatus using multiple radial permeation passages surrounded by the permeation gas jacket is designed to measure the gas permeation rate through the polymer films. The measurement shows reliable accuracy compared with other reported results. Further, to reduce gas permeation through the heat-seal, a novel method of employing metal wire the heat-sealed layers is also investigated in this study.한국과학기술원 : 기계공학전공
Ripply-mediated Xbra inhibition is required for proper head development
No full textSpemann ’ s Organizer induces dorsal and anterior fate to nearby
tissues and make head and body axis in Xenopus embryos. Various
molecules have been discovered to mediate this organizing activity.
We found Ripply as a noble organizer gene through microarray
analysis. Ripply has been reported as a somitogenesis regulating
factor. Ripply binds to Tbx6 and transforms Tbx6 to a transcriptional
repressor in developing somites by recruiting Groucho/TLE corepressors.
However, Ripply was also expressed in dorsal
mesendoderm of early gastrula and in head organizer of late
gastrula. Ectopic expression of Ripply induced blastopore closure
defects and neural tube closure defects, while knockdown of Ripply
induced truncated head. In molecular level, Ripply interacted with
Xbra, and inhibited the target genes of Xbra. Ripply knockdown
resulted in the reduction of head-related genes such as Goosecoid
and Otx2. These result suggest that Ripply maintains the fate of the
head mesoderm by inhibiting Xbra, and this function is necessary for
proper head development.1
Removal torque analysis of chemically modified hydrophilic and anodically oxidized titanium implants with constant angular velocity for early bone response in Rabbit Tibia
No full textImplant geometry and surface properties are important factors for successful osseointegration. The purpose of this study was to compare hydrophilic and hydrophobic implants with different geometries via the continuous measurement of removal torque (RT) and calculation of angular momentum for each implant. Five New Zealand white rabbits were used in the study. Each rabbit received 2 implants. A chemically modified hydrophilic implant with buttress thread was inserted into one tibia, and an anodically oxidized hydrophobic implant with V-shape threads was inserted into the other. After 1 week of healing, RT values were measured continuously in real-time. Using the time-torque curve resulting from the measurements, the maximum values were determined and angular momentums were calculated. The chemically modified hydrophilic implant exhibited significantly higher peak RT and mean torque values before the peak torque (MTBP) than the anodically oxidized hydrophobic implant (p < 0.05). The chemically modified hydrophilic implants exhibited superior early bone response compared to the anodically oxidized implants.N
Three interfaces of the dental implant system and their clinical effects on hard and soft tissues
No full textAnatomically, the human tooth has structures both embedded within and forming part of the exterior surface of the human body. When a tooth is lost, it is often replaced by a dental implant, to facilitate the chewing of food and for esthetic purposes. For successful substitution of the lost tooth, hard tissue should be integrated into the implant surface. The microtopography and chemistry of the implant surface have been explored with the aim of enhancing osseointegration. Additionally, clinical implant success is dependent on ensuring that a barrier, comprising strong gingival attachment to an abutment, does not allow the infiltration of oral bacteria into the bone-integrated surface. Epithelial and connective tissue cells respond to the abutment surface, depending on its surface characteristics and the materials from which it is made. In particular, the biomechanics of the implant-abutment connection structure (i.e., the biomechanics of the interface between implant and abutment surfaces, and the screw mechanics of the implant-abutment assembly) are critical for both the soft tissue seal and hard tissue integration. Herein, we discuss the clinical importance of these three interfaces: bone-implant, gingiva-abutment, and implant-abutment.Y
Comparison of three-dimensional digital analyses and two-dimensional histomorphometric analyses of the bone-implant interface
No full textHistological analysis is considered to be the gold standard method of evaluating osseointegration around a bone-implant. However, this method requires invasive specimen preparation and is capable of representing only one plane. By comparison, micro-computed tomography (μCT) is a fast and convenient method that offers three-dimensional information but is hampered by problems related to resolution and artifacts, making it a supplementary method for osseointegration analysis. To verify the reliability of μCT for osseointegration evaluation, this animal model study compared bone-to-implant contact (BIC) ratios obtained by the gold standard histomorphometric method with those obtained by the μCT method, using a rabbit tibia implant model. A sandblasted, large-grit, acid-etched (SLA) implant and a machined surface implant were inserted into each tibia of two rabbits (giving eight implants in total). Bone-implant specimens were analyzed using μCT with a spiral scan technique (SkyScan 1275) and histological sections were prepared thereafter. Three-dimensional (3D) reconstructed μCT data and four two-dimensional (2D) μCT sections, including one section corresponding to the histologic section and three additional sections rotated 45°, 90°, and 135°, were used to calculate the BIC ratio. The Pearson’s test was used for correlation analysis at a significance level of 0.05. The histomorphometric BIC and the 2D-μCT BIC showed strong correlation (r = 0.762, P = 0.046), whereas the histomorphometric BIC and 3D-μCT BIC did not (r = -0.375, P = 0.385). However, the mean BIC value of three or four 2D-μCT sections showed a strong correlation with the 3D-μCT BIC (three sections: r = 0.781, P = 0.038; four sections: r = 0.804, P = 0.029). The results of this animal model study indicate that μCT can be used to complement the histomorphometric method in bone-implant interface analyses. With the limitations of this study, 3D-μCT analysis may even have a superior aspect in that it eliminates random variables that arise as a consequence of the selected cutting direction
Characteristics of contact and distance osteogenesis around modified implant surfaces in rabbit tibiae
No full textPurpose: Contact and distance osteogenesis occur around all endosseous dental implants. However, the mechanisms underlying these processes have not been fully elucidated. We hypothesized that these processes occur independently of each other. To test this, we used titanium (Ti) tubes to physically separate contact and distance osteogenesis, thus allowing contact osteogenesis to be measured in the absence of possible triggers from distance osteogenesis. Methods: Sandblasted and acid-etched (SLA) and modified SLA (modSLA) implants were used. Both types had been sandblasted with large grit and then etched with acid. The modSLA implants then underwent additional treatment to increase hydrophilicity. The implants were implanted into rabbit tibiae, and half were implanted within Ti tubes. The bone-to-implant contact (BIC) ratio was calculated for each implant. Immunohistochemical analyses of bone morphogenetic protein (BMP)-2 expression and new bone formation (Masson trichrome stain) were performed. Results: The implants outside of Ti tubes were associated with good bone formation along the implant surface. Implantation within a Ti tube significantly reduced the BIC ratio (P<0.001). Compared with the modSLA implants, the SLA implants were associated with significantly higher BIC ratios, regardless of the presence or absence of Ti tubes (P=0.043). In the absence of Ti tubes, the bone adjacent to the implant had areas of new bone formation that expressed BMP-2 at high levels. Conclusions: This study disproved the null hypothesis and suggested that contact osteogenesis is initiated by signals from the old bone that undergoes distance osteogenesis after drilling. This signal may be BMP-2. © 2017. Korean Academy of Periodontology.OAIID:RECH_ACHV_DSTSH_NO:T201717579RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A078517CITE_RATE:1.072FILENAME:065-040 J Periodontal Implant Sci 201706 47(3) 182-92.pdfDEPT_NM:치의학과EMAIL:[email protected]_YN:YFILEURL:https://srnd.snu.ac.kr/eXrepEIR/fws/file/84b0acb5-fcfd-4991-8472-08f57b901d88/linkY
Modifications of Dental Implant Surfaces at the Micro- and Nano-Level for Enhanced Osseointegration
No full textThis review paper describes several recent modification methods for biocompatible titanium dental implant surfaces. The micro-roughened surfaces reviewed in the literature are sandblasted, large-grit, acid-etched, and anodically oxidized. These globally-used surfaces have been clinically investigated, showing survival rates higher than 95%. In the past, dental clinicians believed that eukaryotic cells for osteogenesis did not recognize the changes of the nanostructures of dental implant surfaces. However, research findings have recently shown that osteogenic cells respond to chemical and morphological changes at a nanoscale on the surfaces, including titanium dioxide nanotube arrangements, functional peptide coatings, fluoride treatments, calcium-phosphorus applications, and ultraviolet photofunctionalization. Some of the nano-level modifications have not yet been clinically evaluated. However, these modified dental implant surfaces at the nanoscale have shown excellent in vitro and in vivo results, and thus promising potential future clinical use.Y
Peri-implant bone length changes and survival rates of implants penetrating the sinus membrane at the posterior maxilla in patients with limited vertical bone height
Get PDFPURPOSE: The aim of this study was to measure the peri-implant bone length surrounding implants that penetrate the sinus membrane at the posterior maxilla and to evaluate the survival rate of these implants.METHODS: Treatment records and orthopantomographs of 39 patients were reviewed and analyzed. The patients had partial edentulism at the posterior maxilla and limited vertical bone height below the maxillary sinus. Implants were inserted into the posterior maxilla, penetrating the sinus membrane. Four months after implant insertion, provisional resin restorations were temporarily cemented to the abutments and used for one month. Then, a final impression was taken at the abutment level, and final cement-retained restorations were delivered with mutually protected occlusion. The complications from the implant surgery were examined, the number of failed implants was counted, and the survival rate was calculated. The peri-implant bone lengths were measured using radiographs. The changes in initial and final peri-implant bone lengths were statistically analyzed.RESULTS: Nasal bleeding occurred after implant surgery in three patients. No other complications were found. There were no failures of the investigated implants, resulting in a survival rate of 100%. Significantly more bone gain around the implants (estimated difference=-0.6 mm, P=0.025) occurred when the initial residual bone height was less than 5 mm compared to the >5 mm groups. No significant change in peri-implant bone length was detected when the initial residual bone height was 5 mm or larger.CONCLUSIONS: This study suggests that implants penetrating the sinus membrane at the posterior maxilla in patients with limited vertical bone height may be safe and functional.Purpose : The aim of this study was to measure the peri-implant bone length surrounding implants that penetrate the sinus membrane at the posterior maxilla and to evaluate the survival rate of these implants.
Methods : Treatment records and orthopantomographs of 39 patients were reviewed and analyzed. The patients had partial edentulism at the posterior maxilla and limited vertical bone height below the maxillary sinus. Implants were inserted into the posterior maxilla, penetrating the sinus membrane. Four months after implant insertion, provisional resin restorations were temporarily cemented to the abutments and used for one month. Then, a final impression was taken at the abutment level, and final cement-retained restorations were delivered with mutually protected occlusion. The complications from the implant surgery were examined, the number of failed implants was counted, and the survival rate was calculated. The peri-implant bone lengths were measured using radiographs. The changes in initial and final peri-implant bone lengths were statistically analyzed.
Results : Nasal bleeding occurred after implant surgery in three patients. No other complications were found. There were no failures of the investigated implants, resulting in a survival rate of 100%. Significantly more bone gain around the implants (estimated difference=-0.6 mm, P=0.025) occurred when the initial residual bone height was less than 5 mm compared to the >5 mm groups. No significant change in peri-implant bone length was detected when the initial residual bone height was 5 mm or larger.
Conclusions : This study suggests that implants penetrating the sinus membrane at the posterior maxilla in patients with limited vertical bone height may be safe and functional.This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. 2011-0007662).OAIID:oai:osos.snu.ac.kr:snu2013-01/102/2008003883/6SEQ:6PERF_CD:SNU2013-01EVAL_ITEM_CD:102USER_ID:2008003883ADJUST_YN:NEMP_ID:A078517DEPT_CD:861FILENAME:J Periodontol Implant Sci 201304 43(2) 58-63.pdfDEPT_NM:치의학과EMAIL:[email protected]_YN:NCONFIRM:
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