|Articles about Biomaterials|
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| Hemoglobin recognition by imprinting in semi-interpenetrating polymer network hydrogel based on polyacrylamide and chitosan
Xia, Y. Q., T. Y. Guo, et al. (2005), Biomacromolecules 6(5): 2601-6.
Abstract: Semi-interpenetrating polymer network (semi-IPN) hydrogel was prepared to recognize hemoglobin, by molecularly imprinted method, in the mild aqueous media of chitosan and acrylamide in the presence of N,N'-methylenebisacrylamide as the cross-linking agent. The hydrogel obtained has been investigated by using thermal analysis, X-ray diffraction, differential scanning calorimetry (DSC), and environmental scanning electron microscope (ESEM). Langmuir analysis showed that an equal class of adsorption was formed in the hydrogel, and the adsorption equilibrium constant and the maximum adsorption capacity were evaluated to be 4.27 g/mL and 36.53 mg/g wet hydrogel, respectively. The imprinted semi-IPN hydrogel has a much higher adsorption capacity for hemoglobin than the nonimprinted hydrogel with the same chemical composition and also has a higher selectivity for the imprinted molecule.
| Hemostatic effects of fibrinogen gamma-chain dodecapeptide-conjugated polymerized albumin particles in vitro and in vivo
Okamura, Y., S. Takeoka, et al. (2005), Transfusion 45(7): 1221-8.
Abstract: BACKGROUND: Prototypes of platelet (PLT) substitutes have been studied and the focus was on a dodecapeptide, HHLGGAKQAGDV (H12), which is a fibrinogen gamma-chain carboxy-terminal sequence (gamma 400-411) and exists only in the fibrinogen domain. STUDY DESIGN AND METHODS: H12 was conjugated to the surface of polymerized albumin particles (polyAlb) as biocompatible and biodegradable particles with a mean diameter of 260 +/- 60 nm, and the hemostatic ability of H12-conjugated polyAlb (H12-polyAlb) under flow conditions and thrombocytopenic rats have been studied. RESULTS: H12-polyAlb enhanced the in vitro thrombus formation of activated PLTs on a collagen-immobilized plate when exposed to the flowing thrombocytopenic imitation blood. Furthermore, the analysis of the tail bleeding time of rats that were made thrombocytopenic by busulfan injection showed that H12-polyAlb had a hemostatic effect. Based on the bleeding time and the amount injected, the hemostatic capacity of 20 H12-polyAlb was estimated to correspond to that of one PLT. CONCLUSION: These results were important first steps toward the development of PLT substitutes and indicated that H12-polyAlb may be a suitable candidate for an alternative to human PLT concentrates transfused into thrombocytopenic patients in the future.
| Hemostatic efficacy of two advanced dressings in an aortic hemorrhage model in Swine
Kheirabadi, B. S., E. M. Acheson, et al. (2005), J Trauma 59(1): 25-34; discussion 34-5.
Abstract: BACKGROUND: An effective hemostatic agent capable of stopping severe arterial bleeding and sustaining hemostasis over a prolonged time is required. The U.S. Army recently distributed fibrin sealant (under an Investigational New Drug-approved protocol) and chitosan dressings among deployed medics for treating severe external hemorrhage on the battlefield. The purpose of this study was to evaluate the efficacy of these dressings, as compared with the standard gauze army field dressing, to provide initial and sustained hemostasis up to 96 hours in a lethal uncontrolled arterial hemorrhage model. METHODS: Anesthetized pigs were splenectomized and chronically instrumented for fluid/drug administration and continuous monitoring of vital signs. An infrarenal aortotomy was created using a 4.4-mm aortic hole punch and free bleeding was allowed for 5 seconds. While bleeding profusely, a dressing was applied and pressed into the wound for 4 minutes (occluding the distal flow) and then released. If hemostasis was not obtained, the dressing was replaced with a new one (maximum, two dressings per experiment) with another 4-minute compression. If hemostasis was achieved, the abdomen was closed; the animal was then recovered and monitored up to 96 hours. Initial hemostasis, duration of hemostasis, survival time, blood loss, and other variables were measured. RESULTS: Application of army field dressing (gauze) did not stop the arterial hemorrhage and led to exsanguination of all the pigs (n = 6) within 10 to 15 minutes of the injury. Chitosan dressing produced initial hemostasis in five of seven pigs. However, the dressings failed to maintain hemostasis for more than 1.6 hours (range, 28-102 minutes), resulting in secondary bleeding and death of the animals. Fibrin sealant dressing produced initial hemostasis in all the pigs (n = 6) and maintained hemostasis in five cases, with one failure at 2.2 hours. These pigs resumed normal activities and lived for the 96-hour experiment duration. Computed tomographic images and histologic sections of the aortas from surviving fibrin sealant dressing-treated animals showed formation of pseudoaneurysms and early granulation tissue at the aortotomy site. The posttreatment blood loss, duration of hemostasis, and survival time were significantly different in the fibrin sealant dressing group than the chitosan dressing and army field dressing groups. CONCLUSION: Both chitosan dressing and fibrin sealant dressing stopped initial arterial bleeding that could not be controlled by the standard army field dressing. However, although the fibrin sealant dressing secured hemostasis for up to 4 days, the chitosan dressing consistently failed within 2 hours after application. There may be a risk of rebleeding for high-pressure arterial wounds treated with chitosan dressings, particularly in situations where definitive care is delayed substantially.
| Hepatocyte viability and protein expression within hydrogel microstructures
Itle, L. J., W. G. Koh, et al. (2005), Biotechnol Prog 21(3): 926-32.
Abstract: Poly(ethylene) glycol (PEG) hydrogels have been successfully used to entrap mammalian cells for potential high throughput drug screening and biosensing applications. To determine the influence of PEG composition on the production of cellular protein, mammalian hepatocytes were maintained in PEG hydrogels for 7 days. Total cell viability, total protein production, and the production of two specific proteins, albumin and fibronectin, were monitored. Studies revealed that while PEG composition has no effect on cell viability, increasing amounts of PEG in the hydrogel decrease the amount of protein production by the cells after 7 days from 1.0 x 10(5) +/- 1.7 x 10(4) to 5.2 x 10(3) +/- 1.3 x 10(3) g accumulated protein/mL/million cells. Additionally, cells entrapped in PEG hydrogels produce greater amounts of protein than traditional monolayer culture (1.5 x 10(3) +/- 1.9 x 10(2) g accumulated protein/mL/million cells after 7 days). The addition of the synthetic peptide RGD to 10% PEG hydrogels altered the production of the proteins albumin and fibronectin. Hydrogels with the RGD sequence produced 287 +/- 27 ng/mL/million cells albumin after 7 days, an order of magnitude greater than monolayer cultures, whereas cells in hydrogels without the RGD sequence produced undetectable levels of albumin. Conversely, cells entrapped in 10% PEG hydrogels without the RGD sequence produced 1014 +/- 328 ng/mL/million cells fibronectin after 7 days, whereas 10% PEG hydrogels with the RGD sequence produced 200 +/- 58 ng/mL/million cells fibronectin after 7 days.
| Heterogeneous photocatalytic degradation of picloram, dicamba, and floumeturon in aqueous suspensions of titanium dioxide
Atiqur Rahman, M. and M. Muneer (2005), J Environ Sci Health B 40(2): 247-67.
Abstract: Heterogeneous photocatalytic degradation of three-selected herbicide derivatives: (1) picloram (4-Amino-3,5,6-trichloropyridine-2-carboxylic acid, (2) dicamba (2-Methoxy-3,6-dichlorobenzoic acid, and (3) floumeturon (N,N-Dimethyl-N-[3-(trifluoromethyl)phenyl]-urea) has been investigated in aqueous suspensions of titanium dioxide under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic technique and decrease in total organic carbon (TOC) content as a function of irradiation time under a variety of conditions. The degradation of the herbicide was studied under different conditions such as pH, catalyst concentration, substrate concentration, different types of TiO2, and in the presence of electron acceptors such as hydrogen peroxide (H2O2), potassium bromate (KBrO3), and ammonium persulphate (NH4)2S2O8 besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalysts in the case of dicamba (2) and floumeturon (3), whereas Hombikat UV100 was found to be better for the degradation of picloram (1). The herbicide picloram (1) was found to degrade faster as compared to dicamba (2) and floumeturon (3). The degradation products were analyzed by gas chromatography-mass spectrometry (GC/MS) technique, and plausible mechanisms for the formation of products have been proposed.
| Hierarchical texture of calcium carbonate crystals grown on a polymerized Langmuir-Blodgett film
Sato, K., Y. Kumagai, et al. (2004), Langmuir 20(7): 2979-81.
| Hierarchy of DNA immobilization and hybridization on poly-L-lysine using an atomic force microscopy study
Sawant, P. D., G. S. Watson, et al. (2005), J Nanosci Nanotechnol 5(6): 951-7.
Abstract: The atomic force microscopy has been used to analyze the immobilization of single stranded DNA on poly-L-lysine-coated glass and subsequent hybridization with complimentary DNA with the Z-threshold parameter and fractal analysis methods. The poly-L-lysine layer, which has a thickness of approximately 7 nm, presents nano-defects that could be critical for DNA immobilization by acting as a nucleation sites for ssDNA and subsequently for dsDNA aggregates. The Z-threshold for the dsDNA aggregates is much larger than for ssDNA, but the statistical fractal dimension is very similar, suggesting a conformal increase of the dimensions of the dsDNA aggregates mainly in the Z-direction, due to an effective ssDNA-ccDNA molecular recognition. This study demonstrates the use of fractal analysis in conjunction with the distribution of heights to evaluate the efficiency of DNA-DNA molecular recognition on surfaces and the impact of nanodefects.
| High complication rate identified in sacrocolpopexy patients attributed to silicone mesh
Govier, F. E., K. C. Kobashi, et al. (2005), Urology 65(6): 1099-103.
Abstract: OBJECTIVES: To report on our experience using a preconfigured Y-shaped silicone-coated polyester mesh and polypropylene mesh for vaginal vault suspension. A variety of materials have been used for both open and laparoscopic sacrocolpopexy in the management of vaginal vault prolapse. Recently, a preconfigured Y-shaped silicone-coated polyester mesh was introduced to facilitate the vaginal cuff suspension to the sacrum. METHODS: We reviewed the data of 45 consecutive patients who underwent abdominal (n = 28) or laparoscopic (n = 17) sacrocolpopexy. Of the 45 patients, 21 underwent silicone mesh suspension of the vaginal cuff to the anterior sacrum, with a mean follow-up of 23 months (range 16 to 41). A comparative analysis was performed of 24 patients who underwent the same procedure with polypropylene mesh. RESULTS: Of the 21 patients in the silicone group, 5 (23.8%) have had a major complication (four vaginal mesh erosions and one mesh infection) after a median follow-up of 9.5 months (range 4 to 20). The presenting symptoms were persistent or new vaginal discharge and/or nonspecific pelvic pain. One patient underwent successful removal of the mesh transvaginally, but the rest required abdominal exploration. To date, the 24 patients who underwent vaginal cuff suspension with polypropylene mesh have had no vaginal mesh extrusions or infections, with a mean follow-up of 12 months (range 1 to 38). CONCLUSIONS: Silicone-coated polyester mesh has recently been associated with a high rate of vaginal erosion when used as a transvaginal suburethral sling. Our experience specifically with vaginal vault suspension corroborates this. We have abandoned the use of silicone mesh because of the unacceptably high extrusion rate and presently use polypropylene mesh.
| High interaction alginate-hyaluronate associations by hyaluronate deacetylation for the preparation of efficient biomaterials
Oerther, S., A. C. Maurin, et al. (2000), Biopolymers 54(4): 273-81.
Abstract: The paper presents fundamental investigations of alginate-hyaluronate association with significant polymer interactions for preparation of efficient biomaterials. For this purpose, acetamide functions of hyaluronate were partly cleaved by hydrazine at high temperature, yielding amino groups accessible to carboxylic functions of the alginate chain. Alginate-hyaluronate association was studied both in dissolved state by rheological measurements and CD, and in the form of gel slabs prepared after calcium diffusion. Appreciable interaction between carboxylic groups of alginate and the released amino groups of hyaluronate was put into evidence by enhanced values of the viscosity of mixed solutions, and by assessment of the properties of the gel formed: moderate deacetylation allowed gels of improved hardness and viscosity. Nevertheless, high deacetylation was observed to hinder the gel formation by Ca(2+) complexation of alginate, by the significant competition of COOH-NH(2) association. Interaction between alginate and modified hyaluronate results in regular gel structure, with small cavities.
| High molecular weight kininogen inhibition of endothelial cell function on biomaterials
Voskerician, G., J. M. Anderson, et al. (2000), J Biomed Mater Res 51(1): 1-9.
Abstract: Synthetic vascular grafts implanted into humans fail to develop a complete endothelial lining. In previous studies, we have shown that high-molecular-weight kininogens (HMWK) adsorb to the surfaces of biomaterials. In addition, it has been demonstrated that these proteins modulate cellular function. In the present study, we report on the adhesion and proliferation of human umbilical-vein endothelial cells (HUVEC) on tissue culture polystyrene, glass, polyurethane, and Mylar(trade mark) surfaces coated with human HMWK, either single-chain HMWK (SC-HMWK) or double-chain HMWK (DC-HMWK). Surfaces coated with fibronectin served as a positive control for these experiments. Parallel experiments were performed in which HUVEC were allowed to migrate from crosslinked dextran microcarrier beads (Cytodex 2) onto HMWK-coated surfaces. Our results indicate that HMWK-coated surfaces inhibit endothelial cell adhesion, proliferation, and migration at 24 and 72 h, and this inhibition is concentration dependent. To determine a potential mechanism for this inhibitory phenomenon, cells were stained for cytoskeletal actin filaments using rhodamine-phalloidin. Endothelial cells on HMWK-coated surfaces displayed F-actin filament reorganization/disassembly, characterized by the absence of peripheral actin bands in focal adhesion contacts. We conclude that HMWK inhibit endothelial cell adhesion, proliferation, and migration on a variety of biomaterial surfaces. This inhibitory effect may play a role in promoting the lack of endothelialization in synthetic vascular grafts, which is thought to play a significant role in the failure of these devices.
| High power light emitting diode (LED) arrays versus halogen light polymerization of oral biomaterials: Barcol hardness, compressive strength and radiometric properties
Mills, R. W., A. Uhl, et al. (2002), Biomaterials 23(14): 2955-63.
Abstract: The clinical performance of light polymerized dental composites is greatly influenced by the quality of the light curing unit (LCU) used. Commonly used halogen LCUs have some specific drawbacks such as decreasing light output with time. This may result in a low degree of monomer conversion of the composites with negative clinical implications. Previous studies have shown that blue light emitting diode (LED) LCUs have the potential to polymerize dental composites without having the drawbacks of halogen LCUs. Since these studies were carried out LED technology has advanced significantly and commercial LED LCUs are now becoming available. This study investigates the Barcol hardness as a function of depth, and the compressive strength of dental composites that had been polymerized for 40 or 20s with two high power LED LCU prototypes, a commercial LED LCU, and a commercial halogen LCU. In addition the radiometric properties of the LCUs were characterized. The two high power prototype LED LCUs and the halogen LCU showed a satisfactory and similar hardness-depth performance whereas the hardness of the materials polymerized with the commercial LED LCU rapidly decreased with sample depth and reduced polymerization time (20 s). There were statistically significant differences in the overall compressive strengths of composites polymerized with different LCUs at the 95% significance level (p = 0.0016) with the two high power LED LCU prototypes and the halogen LCU forming a statistically homogenous group. In conclusion, LED LCU polymerization technology can reach the performance level of halogen LCUs. One of the first commercial LED LCUs however lacked the power reserves of the high power LED LCU prototypes.
| High surface energy enhances cell response to titanium substrate microstructure
Zhao, G., Z. Schwartz, et al. (2005), J Biomed Mater Res A 74(1): 49-58.
Abstract: Titanium (Ti) is used for implantable devices because of its biocompatible oxide surface layer. TiO2 surfaces that have a complex microtopography increase bone-to-implant contact and removal torque forces in vivo and induce osteoblast differentiation in vitro. Studies examining osteoblast response to controlled surface chemistries indicate that hydrophilic surfaces are osteogenic, but TiO2 surfaces produced until now exhibit low surface energy because of adsorbed hydrocarbons and carbonates from the ambient atmosphere or roughness induced hydrophobicity. Novel hydroxylated/hydrated Ti surfaces were used to retain high surface energy of TiO2. Osteoblasts grown on this modified surface exhibited a more differentiated phenotype characterized by increased alkaline phosphatase activity and osteocalcin and generated an osteogenic microenvironment through higher production of PGE2 and TGF-beta1. Moreover, 1alpha,25OH2D3 increased these effects in a manner that was synergistic with high surface energy. This suggests that increased bone formation observed on modified Ti surfaces in vivo is due in part to stimulatory effects of high surface energy on osteoblasts.
| Higher viscous solution induces smaller droplets for cell-enclosing capsules in a co-flowing stream
Sakai, S., K. Kawabata, et al. (2005), Biotechnol Prog 21(3): 994-7.
Abstract: Mechanical strength of cell-enclosing capsules governs the success of the transplantation of enclosed cells in vivo for cell therapy. Mechanical strength closely correlates with the concentration and molecular weight of the polymers present in the aqueous solution that end up in the capsules, and the viscosity of the aqueous polymer solution also depends on these two factors. Three aqueous solutions differing in viscosity (1.0, 36, and 194 mPa s) were extruded from a needle (300 microm inner diameter) at a velocity of 1.2 cm/s into an ambient co-flowing liquid paraffin laminar stream. Smaller droplets were obtained from a higher viscous solution. At a liquid paraffin velocity of 23.5 cm/s, the diameter of droplets obtained from the highest viscous solution (194 mPa s)) was 44 +/- 4 microm, and it represented 40% and 20% of that from droplets in solutions of 36 and 1.0 mPa s viscosity, respectively. The cells enclosed in these droplets maintained more than 95% viability during the droplet breakup process independent of the viscosity of the aqueous solution (p > 0.50). In addition, retrieved cells from the droplets showed the same proliferation profiles as the cells that were not subjected to the droplet breakup process, on tissue culture dishes (p > 0.13).
| Highly efficient molecular delivery into mammalian cells using carbon nanotube spearing
Cai, D., J. M. Mataraza, et al. (2005), Nat Methods 2(6): 449-54.
Abstract: Introduction of exogenous DNA into mammalian cells represents a powerful approach for manipulating signal transduction. The available techniques, however, are limited by low transduction efficiency and low cell viability after transduction. Here we report a highly efficient molecular delivery technique, named nanotube spearing, based on the penetration of nickel-embedded nanotubes into cell membranes by magnetic field driving. DNA plasmids containing the enhanced green fluorescent protein (EGFP) sequence were immobilized onto the nanotubes, and subsequently speared into targeted cells. We have achieved an unprecedented high transduction efficiency in Bal17 B-lymphoma, ex vivo B cells and primary neurons with high viability after transduction. This technique may provide a powerful tool for highly efficient gene transfer into a variety of cells, especially the hard-to-transfect cells.
| Highly selective enrichment of phosphorylated peptides from peptide mixtures using titanium dioxide microcolumns
Larsen, M. R., T. E. Thingholm, et al. (2005), Mol Cell Proteomics 4(7): 873-86.
Abstract: Reversible phosphorylation of proteins regulates the majority of all cellular processes, e.g. proliferation, differentiation, and apoptosis. A fundamental understanding of these biological processes at the molecular level requires characterization of the phosphorylated proteins. Phosphorylation is often substoichiometric, and an enrichment procedure of phosphorylated peptides derived from phosphorylated proteins is a necessary prerequisite for the characterization of such peptides by modern mass spectrometric methods. We report a highly selective enrichment procedure for phosphorylated peptides based on TiO2microcolumns and peptide loading in 2,5-dihydroxybenzoic acid (DHB). The effect of DHB was a very efficient reduction in the binding of nonphosphorylated peptides to TiO2 while retaining its high binding affinity for phosphorylated peptides. Thus, inclusion of DHB dramatically increased the selectivity of the enrichment of phosphorylated peptides by TiO2. We demonstrated that this new procedure was more selective for binding phosphorylated peptides than IMAC using MALDI mass spectrometry. In addition, we showed that LC-ESI-MSMS was biased toward monophosphorylated peptides, whereas MALDI MS was not. Other substituted aromatic carboxylic acids were also capable of specifically reducing binding of nonphosphorylated peptides, whereas phosphoric acid reduced binding of both phosphorylated and nonphosphorylated peptides. A putative mechanism for this intriguing effect is presented.
| High-order aberrations in pseudophakia with different IOLs
Cheng, A. C. and D. S. Lam (2005), J Cataract Refract Surg 31(5): 867; author reply 867-8.
| High-performance liquid chromatographic enantioseparation of flavanones on 2-hydroxy- 3-methacryloyloxypropyl beta-cyclodextrin copolymer coated silica phase
Carbonnier, B., L. Janus, et al. (2005), J Chromatogr Sci 43(7): 358-61.
Abstract: Chromatographic resolution of four flavanones is achieved by reversed-phase high-performance liquid chromatography (HPLC) on a chiral stationary phase based on silica coated with a (2-hydroxy-3-methacryloyloxypropyl beta-cyclodextrin-co-N-vinylpyrrolidone) copolymer. The influence of the mobile phase water content and the nature of the organic modifier on the retention and resolution is evaluated. Monosubstituted flavanones are better resolved than the unsubstituted one. Nevertheless, the 6- and 7-methoxy substituents enhance retention and chiral recognition to polymeric beta-cyclodextrin stationary phase less than the 6-hydroxy group.
| High-resolution 3D scaffold model for engineered tissue fabrication using a rapid prototyping technique
Quadrani, P., A. Pasini, et al. (2005), Med Biol Eng Comput 43(2): 196-9.
Abstract: Rapid prototyping, automatic image processing (computer-aided design (CAD)) and computer-aided manufacturing techniques are opening new and interesting prospects for medical devices and tissue engineering, especially for hard tissues such as bone. The development of a bone high-resolution scaffold prototype using these techniques is described. The results testify to the fidelity existing between microtomographic reconstruction and CAD. Furthermore, stereolithographic manufacturing of this scaffold, which possesses a high degree of similarity to the starting model as monitored by morphological evaluations (mean diameter 569 +/- 147 microm), represents a promising result for regenerative medicine applications.
| Histocompatibility of photocrosslinked polyanhydrides: a novel in situ forming orthopaedic biomaterial
Poshusta, A. K., J. A. Burdick, et al. (2003), J Biomed Mater Res A 64(1): 62-9.
Abstract: Cell-polymer interactions in subcutaneous and bony tissue were examined for a novel class of in situ forming and surface eroding polyanhydride networks. Specifically, photopolymerized disks of several polyanhydride compositions were implanted subcutaneously in rats, and the tissue was analyzed for an inflammatory response. The compositions elicited varied histological responses, ranging from highly active cell layers to moderate fibrous capsules, depending on the degrading polymer composition. Furthermore, one composition was photopolymerized in a model orthopaedic defect in the proximal tibia. The feasibility of photopolymerizing the methacrylated monomers in situ and the adherence of the photocrosslinked polyanhydride to the medullary canal were examined.
| Histologic and histomorphometric analysis of three types of dental implants following 18 months of occlusal loading: a preliminary study in baboons
Watzak, G., W. Zechner, et al. (2005), Clin Oral Implants Res 16(4): 408-16.
Abstract: The purpose of this study was to determine the percentage of 'bone area' (BA) and 'bone-to-implant contact' (BIC) of dental implants with different designs and surface modifications after functional loading. Three types of dental implants with fixed partial dentures were placed in the posterior jaws of adult baboons (commercially pure titanium (CpTi) screws, grit-blasted acid-etched (GBAE) screws, and titanium plasma-sprayed (TPS) cylinders), three of the same design per quadrant. After 18 months of functional loading, all implants investigated were successfully integrated in the jawbone and histologic and histomorphometric analyses were carried out. Statistical evaluation was performed with a mixed model with data given as least-square means and standard errors of the mean (SEM). Histologically, direct BIC without connective tissue interposed between implant surfaces and peri-implant bone was seen. Analysis of BA within 1 mm around implants showed significant differences between CpTi (50.5%) and TPS (39.7%) (+/-2.72 SEM; P<0.01) in the maxilla. To account for the different implant designs, absolute BIC was calculated. Significant differences were found between CpTi (23.9 mm) and TPS (15.1 mm) and between GBAE (27.2 mm) and TPS (15.1 mm) (+/-1.05 SEM; P<0.01) in the maxilla and between GBAE (26.5 mm) and TPS (19.6 mm) (+/-1.42 SEM; P<0.01) in the mandible. Overall, the data indicate that, in the maxilla, screw-shaped implants showed more absolute BIC than cylindrical implants, which had less maxillary than mandibular absolute BIC after 18 months of functional loading.
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