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)

The aim of this study was to compare the nanoleakage patterns of the resin-dentin interfaces of three dentin bonding systems at both TEM and field emission in lens SEM (FEI-SEM) levels. A standardized smear layer was created with 180-grit silicon carbide paper (SiC) on dentin disks obtained from 18 noncarious human third molars. Specimens were randomly divided into three groups and bonded with a two-step total etching adhesive (Single Bond, SB), a two-step, self-etching adhesive (Clearfil SE BOND, SEB), and a one-step, self-etching adhesive (XENO III, XEIII). Nanoleakage was evaluated by using an ammoniacal silver-nitrate solution. Specimens were processed for TEM and FEI-SEM observation. The TEM of SB revealed silver deposits in adhesive and hybrid layers (HL). High-magnification FEI-SEM micrographs clearly identified these deposits as spherical clusters mainly associated with nonembedded collagen fibrils. TEM and FEI-SEM examination of SEB revealed some clusters of silver deposits within porosities and small channels of the HL. Additional silver deposits were observed between the peritubular dentin walls and the resin tags. XEIII revealed very fine and diffuse silver grains throughout the entire HL. SEM visualization of nanoleakage at a high level of resolution has not been previously described. FEI-SEM technology supported the TEM visualization with three-dimensional morphological data of the relations between the HL constituents and nanoleakage. The results of the present study confirm the hypothesis that both total- and self-etch adhesives are not able to fully infiltrate the dentin substrate.
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PMID:Nanoleakage within the hybrid layer: a correlative FEISEM/TEM investigation. 1567 95

This in vitro study morphologically evaluated the effect of some current surface pre-treatments on dentin, using scanning electron microscopy, and related these morphological alterations to clinical implications. The labial surfaces of 30 bovine lower incisors were ground to obtain a flat dentin surface and were finished with 600-grit SiC paper to produce standardized smear layers. The teeth were randomly divided into six groups of five each. Group 1 was the control group, smear layer covered dentin; Group 2 was etched with 37% phosphoric acid (PA) for 15 seconds; Group 3, 37% PA for 15 seconds, followed by 10% NaOCl for 60 seconds; Group 4, 10% NaOCl for 60 seconds; Group 5, a self-etching primer (Clearfil SE Bond, CSEB-primer) was applied for 20 seconds; Group 6, CSEB-primer for 20 seconds, followed by NaOCl for 60 seconds. The specimens were fixed, dehydrated, dried and analyzed by SEM. Treatment with 37% PA removed the smear layer, funneled the tubules and resulted in a collagen-rich surface which appeared to have collapsed in its outermost part, producing a dense surface layer covered with silica particles. When 37% PA treatment was followed by 10% NaOCl, the collagen network was removed to reveal an eroded, rough mineral surface with numerous lateral branches and larger than normal tubular orifices. The action of 10% NaOCl on the smear layer-covered dentin showed no significant alteration in surface morphology. The treatment with CSEB-primer dissolved the smear layer but only partially dissolved the smear plugs. The tubules did not present the typical funnel shape seen following PA treatment. These morphological aspects on dentin surface must influence bonding results. The dentin surface alterations produced by PA appeared to be a very severe demineralization pattern, quite irregular and less permeable to monomer infiltration, while the surface provided by the self-etching primer appeared to be a more uniform, less porous surface, and the association with simultaneous monomer infiltration may reduce the occurrence of mistakes in clinical bonding procedures.
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PMID:The in vitro morphological effects of some current pre-treatments on dentin surface: a SEM evaluation. 1585 6

Direct bone-to-implant contact, defined as "osseointegration", is considered most optimal for long-term stability and survival of dental implants. However, the possibility of the formation of a tooth-like attachment apparatus around implants has also been demonstrated. The purpose of this study was to explore the formation of periodontal tissues around titanium implants using a novel and unique experimental model. After resection of the crowns of the maxillary canine teeth in nine mongrel dogs, the roots were hollowed to a depth of 5 mm leaving a thin dentinal wall. Slits were prepared in the cavity wall to create passages from the chamber to the periodontal ligament area. A custom-made, titanium implant was placed into the center of each chamber. Machined, titanium plasma sprayed (TPS) and sand blasted with large grit and acid attacked (SLA) surfaces were used. A collagen barrier was placed over the submerged chamber. Following 4 months of healing, jaw sections were processed for histology. Newly formed periodontal ligament, alveolar bone, and root cementum filled the space between the implant and the wall of the chamber. Ingrown bone was neither in contact with dentin nor with the implant. Thus, an interposed soft connective tissue layer was present. Healing by fibrous encapsulation was observed around most implants. However, cellular cementum was deposited on one TPS and one SLA implant and on the dentinal walls of the chamber. This study shows a remarkable capacity for new periodontal tissue formation at a site where no such tissues ever existed. Maintenance of original periodontal tissue domains most likely prevented osseointegration of the implants. The cementum layer deposited on two implants was likely formed through cementoconductivity rather than by differentiation of periodontal ligament cells upon contact with the implant surface.
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PMID:New formation of periodontal tissues around titanium implants in a novel dentin chamber model. 1587 45

Increasing bone formation at endosseous titanium implants may be achieved by modification of topographically enhanced surfaces. The aim of this study was to determine the effect of fluoride ion modification of TiO2 grit-blasted, c.p. titanium implants on osteoblastic differentiation and interfacial bone formation by parallel in vitro and in vivo investigations. Human mesenchymal stem cells (Osiris Therapeutics, Inc.) were cultured on TiO2 grit-blasted c.p.titanium disks with and without fluoride ion modification. Cell adhesion, proliferation, and osteoblastic gene expression was measured by scanning electron microscopy, tritiated-thymidine uptake into insoluble DNA, and reverse transcription polymerase chain reaction detection of mRNAs encoding collagen 1, osteopontin, bone sialoprotein, osteocalcin and BMP-2. After 24 h, there were no differences in cell adhesion among the surfaces tested. Fluoride-treated surfaces supported greater proliferation and increased bone sialoprotein and BMP-2 expression. Additionally, 12 TiO2 grit-blasted and 12 fluoride ion modified implants were placed randomly into medial and distal osteotomies prepared in the tibia of 300 g Sprague Dawley rats. After 21 days, the tibiae were harvested and 100 microm ground sections were examined by backscatter scanning electron microscopy. The bone-to-implant contact formed at TiO2 grit-blasted and fluoride-treated versus TiO2 grit-blasted surfaces was 55.45% versus 34.21% (p<0.027), respectively. Fluoride ion modification of the TiO2 grit-blasted surface enhanced osteoblastic differentiation in vitro and interfacial bone formation in vivo. This parallel in vitro and in vivo investigation demonstrates that fluoride ion modification enhanced osteoblastic differentiation and interfacial bone formation. The mechanism(s) by which fluoride ion modification of c.p.titanium enhanced osteoblastic differentiation and osseointegration merit careful investigation.
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PMID:Fluoride modification effects on osteoblast behavior and bone formation at TiO2 grit-blasted c.p. titanium endosseous implants. 1611 91

The aim of this study was to evaluate the osteogenic properties of magnetron sputtered dicalcium pyrophaosphate (DCPP) and hydroxylapatite (HA) coatings. Therefore, DCPP and HA coatings were deposited on grit-blasted titanium discs. The substrates were used as-prepared or received an additional heat treatment which changed the amorphous coating structure to a crystalline structure. Subsequently, rat bone marrow stromal cells were cultured for 1-24 days on the various substrates. DNA and alkaline phosphatase activity was determined after 1, 3, 5, 8, and 12 days of incubation. Osteocalcin expression was evaluated after 8, 12, 16, and 24 days of incubation. Scanning electron microscopical analysis of cell morphology and coating characteristics was done after 8 and 16 days of incubation. All assays were done in duplicate and in each assay all specimens were present in fourfold. Results demonstrated that the cells did not proliferate and differentiate on all amorphous coatings. SEM revealed that the amorphous coatings showed significant dissolution. On the crystalline DCPP and HA coatings an increase in DNA and alkaline phosphatase activity was seen starting at day 8 of incubation. Osteocalcin expression on the crystalline coatings started to increase at day 16 of incubation. SEM showed that the growth and differentiation of the cells was associated with extensive collagen fiber formation and surface mineralization in the form of globular accretions. Further, statistical testing revealed that proliferation and differentiation of the rat bone marrow stromal cells started significantly earlier on the crystalline HA coatings than that on the crystalline DCPP coatings. These results demonstrate that the rat bone marrow stromal cells proliferated and differentiated only on crystalline magnetron sputtered DCPP as well as HA coatings, which warrants the further in vivo analysis of the bone healing supporting properties of these coatings.
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PMID:Growth behavior of rat bone marrow cells on RF magnetron sputtered hydroxyapatite and dicalcium pyrophosphate coatings. 1660 22

During the process of bone formation, titanium (Ti) surface is an important factor in the modulation of osteoblastic function. This study was conducted in order to determine the effects of different Ti surfaces on the biological responses of a human osteoblast-like cell line (MG63). MG63 cells were cultured on smooth (S), sandblasted large-grit and acid etching (SLA), hydroxyapatite (HA), hydroxyfluoride (HF), titanium nitrate (TIN), and diamond-like carbon (DLC) Ti. The morphology of these cells were assessed by SEM. The cDNAs prepared from the total RNAs of the MG63 were hybridized into a human cDNA microarray (1152 elements). The appearances of the surfaces observed by SEM were different on each of the six dental substrate types. The SLA and HA surfaces were determined to be rougher than the others. MG63 cells cultured on SLA and HA exhibited cell-matrix interactions. In the expression of genes involved in osseointegration, several genes, including bone morphogenetic protein, cadherin, integrin, and insulin-like growth factors, were upregulated on the different surfaces. Several genes, including fibroblast growth factor receptor 4, Bcl 2-related protein, and collagen, were downregulated on the different surfaces. The attachment and expression of key osteogenic regulatory genes were enhanced by the surface roughness of the dental materials used.
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PMID:Effect of various implant coatings on biological responses in MG63 using cDNA microarray. 1662 96

The aim of this study was to evaluate the efficacy of collagen membranes, either alone or combined with a human demineralized freeze-dried bone allograft (DFDBA) or natural bovine bone graft, in bone defects around dental implants with an SLA (sand-blasted, large grit, acid-etched) surface. The experiments were carried out in three beagle dogs using a split-mouth design. On one side of the jaw, three implants were placed and intra-bony defects were created and covered with a collagen membrane, randomly combined in two of the defects with human DFDBA or inorganic bovine bone graft. A control implant, without membrane covering or defect filling, was also placed. On the other side of the jaw, three implants were placed and the bone defects were treated in a similar fashion, but without membrane covering. The studied variables were the percentage of bone-to-implant contact within the limits of the initial bony defect and percentage of the original bony defect occupied by bone tissue. Although no statistically significant differences were found in this study between the membrane and nonmembrane groups, bone defects augmented with anorganic bovine bone and membranes showed the most promising results from a histological and histomorphometric perspective.
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PMID:Histomorphometric evaluation of guided bone regeneration around implants with SLA surface: an experimental study in beagle dogs. 1697 32

The aim of this study was to investigate the influence of hydrophobic acid-etched (A) and coarse-blasted large-grit and acid-etched (SLA) surfaces as well as hydrophilic modified acid-etched (modA) and modified coarse-blasted large-grit and acid-etched (modSLA) surfaces on the behavior of MG63 cells grown on these surfaces through determination of cell attachment and cell proliferation, time-lapse microscopy of fluorescence-labeled cells, and determination of gene expression by reverse transcription-polymerase chain reaction (RT-PCR). No significant difference of cell attachment on various titanium surfaces was found. Increased cell proliferation was observed on the A surface and the SLA surface compared with the modA surface and the modSLA surface. After 2 days of incubation, on modSLA and modA surfaces a tendency of formation of cell clusters has been observed, which was most pronounced on modSLA surface. On the A and the SLA surface, cell cluster formation started after longer incubation periods. The expression level of the bone-associated genes (alkaline phosphatase, osteocalcin, type-I-collagen, osteoprotegerin, and glyceraldehyde-3-phosphate-dehydrogenase) detected by RT-PCR was highest on the modSLA surface. In conclusion it has been demonstrated that the modSLA surface results in an enhanced cluster formation of osteoblasts grown on this surface and in an increased expression of key osteogenic regulatory genes in osteoblasts.
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PMID:The initial attachment and subsequent behavior regulation of osteoblasts by dental implant surface modification. 1732 17

The aim of the present pilot study was to histologically/immunohistochemically investigate initial and early subepithelial connective tissue attachment at transmucosal parts of modified (mod) and conventional sandblasted, large grit and acid-etched (SLA) titanium implants. Implantation of modSLA and SLA implants was performed bilaterally in both the mandible and maxilla of four beagle dogs. The implants were submerged to prevent bacterial contamination. The animals were killed after 1, 4, 7 and 14 days. Peri-implant tissue reactions were assessed histologically (Masson Goldner Trichrome stain-MG) and immunohistochemically (IH) using monoclonal antibodies to fibronectin (FN) and proliferating cell nuclear antigen (PCNA). The surgical procedure of implant submerging resulted in the formation of an artificial gap in the transmucosal area of both types of implants. After 14 days of healing, MG stain revealed the formation of well-organized collagen fibres and numerous blood vessels in a newly formed loose connective tissue zone adjacent to modSLA. While some fibres were oriented in a parallel direction, others have started to extend and attach partially perpendicular to the implant surface. In contrast, SLA implants appeared to be clearly separated by a dense connective tissue zone with parallel-running collagen fibres and rare blood vessel formation. First signs of a positive FN and PCNA staining adjacent to both implant surfaces were observed at day 4. Within the limits of a pilot study, it might be concluded that modSLA titanium surfaces might possess the potential to promote subepithelial connective tissue attachment at the transmucosal part of the implant.
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PMID:Histological and immunohistochemical analysis of initial and early subepithelial connective tissue attachment at chemically modified and conventional SLA titanium implants. A pilot study in dogs. 1736 52

Efforts to improve bone response to biomaterials have focused on ligands that bind alpha5beta1 integrins. However, antibodies to alpha5beta1 reduce osteoblast proliferation but do not affect differentiation when cells are grown on titanium (Ti). beta1-silencing blocks the differentiation stimulus of Ti microtopography, suggesting that other beta1 partners are important. Stably alpha2-silenced MG63 human osteoblast-like cells were used to test whether alpha2beta1 specifically mediates osteoblast response to Ti surface micron-scale structure and energy. WT and alpha2-silenced MG63 cells were cultured on tissue culture polystyrene (TCPS) and Ti disks with different surface microtopographies: machined pretreatment (PT) surfaces [mean peak to valley roughness (R(a)) < 0.02 microm], PT surfaces that were grit-blasted and acid-etched (SLA; R(a) = 4 microm), and SLA with high surface energy (modSLA). Alkaline phosphatase (ALP), alpha2 and beta1 mRNA, but not alpha5, alpha v, beta3, type-I collagen, or osteocalcin, increased on SLA and modSLA at 6 days. Alpha2 increased at 8 days on TCPS and PT, but remained unchanged on SLA and modSLA. Alpha2-protein was reduced 70% in alpha2-siRNA cells, whereas alpha5-mRNA and protein were unaffected. Alpha2-knockdown blocked surface-dependent increases in beta1 and osteocalcin and decreases in cell number and increases in ALP and local factors typical of MG63 cells grown on SLA and modSLA [e.g., prostaglandin E(2), osteoprotegerin, latent and active TGF-beta1, and stimulatory effects of 1alpha,25(OH)(2)D(3) on these parameters]. This finding indicates that alpha2beta1 signaling is required for osteoblastic differentiation caused by Ti microstructure and surface energy, suggesting that conclusions based on cell behavior on TCPS are not predictive of behavior on other substrates or the mechanisms involved.
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PMID:Integrin alpha2beta1 plays a critical role in osteoblast response to micron-scale surface structure and surface energy of titanium substrates. 1884 4


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