Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:A7KAX9 (grit)
 1,275 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In a previous experiment, it was demonstrated that a wide marginal defect around an implant can heal with a high degree of osseointegration. The present experiment was performed to evaluate the degree and quality of de novo bone formation and osseointegration in marginal defects adjacent to submerged titanium implants. All mandibular premolars and 1st molars were extracted in four Labrador dogs. Four experimental sites were identified in the right side of the mandible. In two sites, custom-made implants with a sandblasted, large grit, acid-etched (SLA) surface were installed without further ostectomy (control sites). In the two remaining sites (test sites), a specially designed step drill was used to widen the marginal 5 mm of the canal. A barrier membrane was used to cover the implants in the defect sites. All implants were submerged. One month later, an identical procedure, including site preparation and implant installation, was performed in the left side of the mandible. Two months following the first implant installation procedure, biopsies were collected and prepared for sectioning. Ostectomy and implant installation in the control location resulted in a series of bone tissue alterations which eventually allowed newly formed bone to establish contact with the SLA surface. The marginal defect lateral to the implant in the test locations gradually became filled with newly formed bone. De novo bone formation started within the walls of the surgically prepared defect. Bone-to-implant contact was first established in the apical portion of the gap. This new bone tissue was in the coronal direction continuous with a dense, non-mineralized 'implant attached' soft tissue which, over time, also became mineralized to increase the height of the zone of bone-to-implant contact. The results suggest that healing of a wide marginal defect around an implant is characterized by appositional bone growth from the lateral and apical bone walls of the defect.
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PMID:Appositional bone formation in marginal defects at implants. 1256 59

Following tooth extraction, a socket often presents dimensions that may be considerably greater that the diameter of a conventional implant. The present experiment was performed to study the healing that occurred adjacent to implants placed in recipient sites with a wide marginal defect. Four Labrador dogs were used. In the right side of the mandible, four experimental sites were prepared to receive titanium implants [sandblasted, large-grit, acid-etched (SLA) surface]. Traditional implant installation (control) was performed in one site. In the remaining three sites (test), a step drill was used to widen the marginal 5 mm of the canal. Following placement of an implant in a test site, a circumferential gap about 1-1.25 mm wide and 5 mm deep was present lateral to the implant. A resorbable barrier membrane was used to cover the implant and the bone tissue of two sites, while one site was left uncovered. Four months following implant installation, block biopsies of each implant site were obtained and prepared for ground sectioning. After 4 months of healing, the large marginal defect had been filled with newly formed bone. The degree of bone-to-implant contact between the newly formed tissue and the SLA surface was at all test sites high and similar to that obtained at control sites. The placement of a barrier membrane following implant installation did not improve the outcome of healing. We conclude that a marginal defect wider than 1 mm may heal with new bone and a high degree of osseointegration to an implant designed with a SLA surface.
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PMID:The jumping distance revisited: An experimental study in the dog. 1256 63

The objective of this study was to examine the osteoinductive capacity of different concentrations of BMP-2 on bone marrow stromal cells in vitro. Further, we intended to determine whether titanium provided with an increased surface roughness is more efficient in osteoblast differentiation than machined titanium. Therefore, 20,000 cells/ml were seeded and cultured on machined and grit-blasted titanium discs for 4, 8 and 16 days. Different concentrations of rhBMP-2 (0, 10, 100, 1000 ng/ml) were supplemented to the medium for 8 days of culturing. To evaluate cellular proliferation and differentiation, specimens were examined for DNA, alkaline phosphatase activity, and calcium content. Morphological appearance of the specimens at 8 and 16 days of incubation was evaluated using scanning electron microscopy. Two separate experimental runs were performed. Evaluation of the DNA and alkaline phosphatase data revealed that a significant difference existed for these data between both experimental runs. Further analysis of the DNA figures learned that roughening of the titanium surface and addition of BMP-2 had no effect on cell proliferation. The alkaline phosphatase analysis and calcium measurements revealed that BMP-2 stimulated the early differentiation of osteogenic cells on machined titanium substrates in a dose-dependent manner. After 16 days of culture, no significant differences in calcium content could be observed anymore between machined and roughened titanium surfaces. Further, the data revealed that the machined surfaces showed a significant increase in calcium deposition when 100 and 1000 ng/ml BMP-2 were supplemented to the medium. However, the roughened surfaces showed this significant enhancement in calcium content only with 1000 ng/ml BMP-2. In addition, SEM evaluation revealed a dose-dependent response to BMP-2. Increasing BMP-2 concentrations resulted in more calcified globular accretions on bone surfaces than when no BMP-2 was added. On the basis of our results, we conclude that (1) due to the heterogeneous nature of bone marrow, experimental results with primary rat bone marrow cells are difficult to reproduce from one experiment to the other, and (2) addition of rhBMP-2 in the medium stimulates the early differentiation and matrix mineralization of osteogenic cells on machined titanium surfaces in a dose-responsive manner. Further, we concluded that our roughened titanium surfaces had no effect on proliferation and differentiation of primary derived rate bone marrow cells.
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PMID:Observations on the effect of BMP-2 on rat bone marrow cells cultured on titanium substrates of different roughness. 1261 75

The surface conditions of Nitinol wires and tubing were evaluated with the use of X-ray photoelectron spectroscopy, high-resolution Auger spectroscopy, electron backscattering, and scanning-electron microscopy. Samples were studied in the as-received state as well as after chemical etching, aging in boiling water, and heat treatment, and compared to a mechanically polished 600-grit-finish Nitinol surface treated similarly. General regularities in surface behavior induced by the examined surface treatments are similar for wires, tubing, and studied as-cast alloy, though certain differences in surface Ni concentration were observed. Nitinol wires and tubing from various suppliers demonstrated great variability in Ni surface concentration (0.5-15 at.%) and Ti/Ni ratio (0.4-35). The wires in the as-received state, with the exception of those with a black oxide originating in the processing procedure, revealed nickel and titanium on the surface in both elemental and oxidized states, indicating a nonpassive surface. Shape-setting heat treatment at 500 degrees C for 15 min resulted in tremendous increase in the surface Ni concentration and complete Ni oxidation. Preliminary chemical etching and boiling in water successfully prevented surface enrichment in Ni, initially resulting from heat treatment. A stoichiometric uniformly amorphous TiO(2) oxide generated during chemical etching and aging in boiling water was reconstructed at 700 degrees C, revealing rutile structure.
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PMID:Surface conditions of Nitinol wires, tubing, and as-cast alloys. The effect of chemical etching, aging in boiling water, and heat treatment. 1263 90

We report the outcome of a grit-blasted titanium stem designed for press-fit insertion and entirely plasma sprayed with HA. During the years 1988-1993, we performed 323 primary total hip replacements in 276 patients (189 women) with a HA-coated prosthesis. Their mean age was 48 (15-79) years. During the follow-up, 12 patients died. 19 other patients did not attend the follow-up examination, but had no major symptoms according to telephone interviews and written replies. Thus, 245 patients (291 hips) were followed for a mean of 10 (8-12) years with radiographic and clinical examinations. Only 1 stem was revised due to mechanical failure. None were revised because of infection. Osteolysis was significantly associated with wear, and wear was significantly associated with the size of the femoral head. We found a small amount of proximal bone loss (37/291) and a low incidence of distal hypertrophy of the bone (23/291). These observations indicate an essentially physiological weight distribution from the stem to the femoral bone. The changes in the bone confirmed that the femoral component was well fixed in asymptomatic patients. To conclude, we found excellent 8-12-year results with a fully HA-coated femoral prosthesis designed for press-fit insertion.
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PMID:Excellent results of HA coating on a grit-blasted stem: 245 patients followed for 8-12 years. 1280 19

Chemical acid etching alone of the titanium implant surface have the potential to greatly enhance osseointegration without adding particulate matter (e.g. TPS or hydroxyapatite) or embedding surface contaminants (e.g. grit particles). The aims of the present study were to evaluate any differences between the machined and dual acid etching implants with the removal torque as well as topographic analysis. A total of 40 custom-made, screw-shaped, commercially pure titanium implants with length of 5 mm and an outer diameter of 3.75 mm were divided into 4 groups, 10 screws in each, and chemical modification of the titanium implant surfaces were achieved using HF and HCl/H(2)SO(4) dual acid etching. The first exposure was to hydrofluoric acid and the second was to a combination of hydrochloric acid and sulfuric acid. The tibia metaphysics was exposed by incisions through the skin, fascia, and periosteum. One implant of each group was inserted in every rabbit, 2 in each proximal tibia metaphysics. Every rabbit received 3 implants with acid etched surfaces and 1 implant with a machined surface. Twelve weeks post-surgically, 7 rabbits were sacrificed, Subsequently, the leg was stabilized and the implant was removed under reverse torque rotation with a digital torque gauge (Mark-10 Corporation, USA) (Fig. 1). Twelve weeks after implant placement, the removal torque mean values were the dual acid etched implants (24%HF+HCl/H(2)SO(4), group C) required a higher average force (34.7 Ncm), than the machined surface implants (group A) (p=0.045) (Mann-Whiteney test). Scanning electron micrographs of acid etching of the titanium surface created an even distribution of very small (1-2 microm) peaks and valleys, while machining of the titanium surface created typical microscopically grooved surface characteristics. Nonetheless, there was no difference in surface topography between each acid etched implant groups. Therefore, chemically acid etching implant surfaces have higher strengths of osseointegration than machined implant surfaces. There is less correlation between removal torque and the difference in HF volume%.
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PMID:The removal torque of titanium screw inserted in rabbit tibia treated by dual acid etching. 1280 91

Our aims in this study were (1) to develop an electrochemical method of depositing adherent octacalciumphosphate (OCP) and other calcium phosphate coatings on titanium alloy (Ti6Al4V) substrates of different shapes and surface preparations, (2) to determine the properties of the coating (composition, morphology, thickness, dissolution), and (3) to observe transformation of OCP to carbonatehydroxyapatite (CHA) in simulated body fluid (SBF). Titanium (Ti)-alloy plates, tensile bars with four types of surfaces (grit-blasted with apatitic abrasive, chemically textured, arc-deposited, and Co-Cr-beaded) and dissolution cylinders were electrochemically coated with the use of modulated pulse time electric fields programmed with a custom-made dual microprocessor. Modulated electrochemical deposition (MECD) was carried out with pH and temperature conditions favorable for OCP formation. Coatings were characterized using X-ray diffraction, FT-IR, scanning electron microscopy, tensile strength tests, and solubility tests. XRD and FT-IR analyses showed that pure, uniform OCP coatings were produced on Ti6Al4V surfaces with coating-to-substrate tensile strengths greater than 7,000 psi. Coatings on Ti arc-deposited surfaces, chemically textured surfaces, and Co-Cr-beaded surfaces all gave tensile strengths ranging from 5,000 to 7,000 psi, with no coating shadows in the crevices. Dissolution of OCP coating in 100 mL of 0.1 M Tris buffer solution was determined from the amount of calcium (Ca) released onto the buffer, which was 7.7 +/- 1.0 ppm Ca at pH 7.3 after 4 h, and 22 -/+ 1.4 ppm Ca at pH 3 after 2 h. We found that OCP crystal size can be controlled by the current density and relative pulse time modulation. Our study demonstrated the following: (1) Highly adherent calcium phosphate (e.g., OCP) coating of uniform compositions (e.g., OCP) on Ti-alloy substrates can be obtained at low temperatures with the use of MECD by optimizing pulse time modulation of the electric field, reaction pH, temperature, and electrolyte composition; and (2) OCP readily transforms to CHA when exposed to SBF.
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PMID:Adherent octacalciumphosphate coating on titanium alloy using modulated electrochemical deposition method. 1292 34

Scientific evidence that has been gathered in the past 20 years established that certain endosseous dental implants--primarily screw-type implants made of commercially pure titanium can be successfully utilized as anchorage for dental prostheses. In recent years, an effort has been made to simplify the surgical procedure, in order to modify clinical treatment modalities. One of the trends is to increasingly utilize microrough titanium implants. Roughened implant surfaces have a long history in implant dentistry, and the most prominent surface is titanium plasma-sprayed (TPS). In recent years new implant surfaces have emerged, so-called microrough titanium surfaces produced with reducing techniques such as grit-blasting with Al2O3 or TiO2 particles, sandblasting and acid-etching, or acid-etching alone. These different titanium surfaces have been tested in numerous in-vivo studies utilizing different animal models. Summarizing the results of these studies, it can be concluded that there is currently sufficient evidence that titanium implants with a microrough surfaces achieve a faster bone integration, a higher percentage of Bone implant Contact (BIC), and a higher resistance to shear documented with higher Removal Torque Values (RTV) when compared with titanium implants with a polished or machined surface. In order to understand the mechanism through which surface roughness modulates its effects mentioned above, recent studies used in-vitro experimental methods to study cell response to implant surface topography. These studies have shown that osteoblasts are sensitive to surface roughness, exhibiting decreased proliferation and a more differentiated phenotype on rougher surfaces. PGE2 production is enhanced on rough surfaces, as is the production of TGF beta 1, suggesting that surface roughness can mediate autocrine and paracrine regulation of osteogenesis. Moreover, surface roughness was found to modulate the effect of systemic hormones like 1,25-(OH)2D3 on osteoblasts. The clinical advantages of implants with rough surface were observed in recently conducted clinical trials. It was found, in humans, that roughened titanium implants need shorter healing period before loading, 6-8 (SLA and Osseotite respectively) weeks instead of 12 weeks. The clinical advantages of shorter healing periods are obvious. Moreover, it was found that certain roughened implants can be used in shorter sizes (6-8 mm) then accepted today. The utilization of shorter implants offers the avoidance of extensive surgical procedures such as nerve lateralization in the mandible or sinus grafting in the maxilla. However, sufficient long term documentation is still lacking, and the predictability of such modalities has yet to be examined in long term prospective clinical trials.
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PMID:[The role of surface roughness in promoting osteointegration]. 1451 25

In the present study, the effect of a dual treatment of titanium implants and the subsequent bone response after implantation were investigated. Coin-shaped c.p. titanium implants were placed into the tibias of 12 rabbits. The implant, which was dually blasted with TiO2 particles of two different sizes, was compared with implants that were blasted with only one of these particle sizes. Implants in group 1 were grit blasted with small particles, 22-28 microm in size, and group 2 with coarser particles, 180-220 microm size. These two treatments gave different surface micro textures. To test the effect of a combination of two different treatments, group 3 implants were blasted first with the 180- to 220-microm and subsequently with the 22- to 28-microm particles. The surface topography of the implant specimens was examined by scanning electron microscopy and by a confocal laser scanner and a numeric evaluation of S(a), S(t), and S(dr) was recorded. Group 2 implants, which were blasted with only the coarse particles, showed a significantly better functional attachment (p < 0.001) than the other two groups. Group 1, which was blasted with only small particles, showed the lowest retention in bone. There was a positive correlation between the topographical and mechanical evaluation of the surfaces.
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PMID:A study on the effect of dual blasting with TiO2 on titanium implant surfaces on functional attachment in bone. 1456 94

Osteoconductivity of titanium-alloy implants may be improved when surface-modified by calcium ion (Ca2+) implantation. We studied the effects of Ca2+ implantation on osseointegration of a grit-blasted titanium-alloy stem using a canine total hip arthroplasty model. Fifteen dogs underwent bilateral hip arthroplasties and were sacrificed at 1, 6, and 12 months postoperatively. The hip components were evaluated by radiographic, qualitative, and quantitative histology methods. Radiographically and histologically, both Ca(2+)-implanted and non-Ca(2+)-implanted stems were well integrated. Ca(2+)-implanted stems had greater new bone apposition than non-Ca(2+)-implanted stems, although the difference was significant only at 1 month (15.8% +/- 3.5% of the implant perimeter for non-Ca(2+)-implanted, 25.4% +/- 4.7% for Ca(2+)-implanted, P< .05). This result could be related to chronological decrease of the dissolution rate of calcium ions from Ca(2+)-implanted surface. Although further improvement of the Ca2+ implantation technique for a sustained osteoconductive effect is necessary, Ca2+ implantation may be beneficial for early fixation of titanium-alloy implants.
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PMID:Effects of calcium ion implantation on osseointegration of surface-blasted titanium alloy femoral implants in a canine total hip arthroplasty model. 1471 57


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