| 61. |
- Kjellin, P., et al.
(författare)
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A nanosized zirconium phosphate coating for PEEK implants and its effect in vivo
- 2020
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Ingår i: Materialia. - : Elsevier BV. - 2589-1529. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Surface treatments and coatings can be applied to polyether ether ketone (PEEK) implants to improve their ability to osseointegrate. A new coating, consisting of amorphous nanosized zirconium phosphate (ZrP) was applied to PEEK and titanium substrates. The coating was applied by using a microemulsion as a carrier for the nanoparticles. It was found that the coating formed a thin continuous porous layer on top of the substrate, with pore diameters of 10–50 nm. The thickness of the coating was estimated to <100 nm. The resistance to acidic (pH = 4) conditions and exposure to ultrasonication was investigated with XPS, which showed no loss of coating. The adherence of the coating was investigated by insertion of implants in simulated bone material, which showed a minor loss in coating. In vitro (SBF) testing showed that the coating promoted crystallization of calcium phosphates, for uncoated PEEK, no crystallization was detected. The in vivo performance of the ZrP coating was examined by coating screw shaped PEEK implants which were implanted in rabbit tibia for 6 weeks. The anchoring strength of the implants was evaluated with removal torque (RTQ) measurements. The average RTQ for the ZrP coated implants was significantly higher compared to the non-coated implants. The results show that a nanosized ZrP coating on PEEK implants can transform the surface from having a low ability to osseointegrate to a surface which stimulates bone tissue growth. This makes the ZrP coating an interesting alternative for coating PEEK implants, such as spinal fusion cages and tendon fixation screws. © 2020
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| 62. |
- Kruger, D., et al.
(författare)
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High-resolution ex vivo analysis of the degradation and osseointegration of Mg-xGd implant screws in 3D
- 2022
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Ingår i: Bioactive Materials. - : Elsevier BV. - 2452-199X. ; 13, s. 37-52
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Tidskriftsartikel (refereegranskat)abstract
- Biodegradable magnesium (Mg) alloys can revolutionize osteosynthesis, because they have mechanical properties similar to those of the bone, and degrade over time, avoiding the need of removal surgery. However, they are not yet routinely applied because their degradation behavior is not fully understood. In this study we have investigated and quantified the degradation and osseointegration behavior of two biodegradable Mg alloys based on gadolinium (Gd) at high resolution. Mg-5Gd and Mg-10Gd screws were inserted in rat tibia for 4, 8 and 12 weeks. Afterward, the degradation rate and degradation homogeneity, as well as bone-to-implant interface, were studied with synchrotron radiation micro computed tomography and histology. Titanium (Ti) and polyether ether ketone (PEEK) were used as controls material to evaluate osseointegration. Our results showed that Mg-5Gd degraded faster and less homogeneously than Mg-10Gd. Both alloys gradually form a stable degradation layer at the interface and were surrounded by new bone tissue. The results were correlated to in vitro data obtained from the same material and shape. The average bone-to-implant contact of the Mg-xGd implants was comparable to that of Ti and higher than for PEEK. The results suggest that both Mg-xGd alloys are suitable as materials for bone implants.
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| 63. |
- Larsen, Olav Inge, et al.
(författare)
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Antimicrobial effects of three different treatment modalities on dental implant surfaces.
- 2017
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Ingår i: The Journal of oral implantology. - 1548-1336. ; 43:6, s. 429-436
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Tidskriftsartikel (refereegranskat)abstract
- Resolution of peri-implant inflammation and re-osseointegration of peri-implantitis affected dental implants seem to be dependent on bacterial decontamination. The aims of the this study were to evaluate the antimicrobial effects of three different instrumentations on a micro-textured dental implant surface contaminated with an avirulent or a virulent Porphyromonas gingivalis strain and to determine alterations to the implant surface following instrumentation. Forty-five dental implants (Straumann SLA) were allocated to three treatment groups: Er:YAG laser, chitosan brush, and titanium curette (10 implants each), a positive (10 implants) and a negative (five implants) control. Each treatment group and the positive control were split into subgroups of five implants subsequently contaminated with either the avirulent or virulent P. gingivalis strain. The antimicrobial effect of instrumentation was evaluated using checkerboard DNA-DNA hybridization. Implant surface alterations were determined using a light interferometer. Instrumentation significantly reduced the number of attached P. gingivalis (p<0.001) with no significant differences among groups (p=0.310). A significant overall higher median score was found for virulent compared with avirulent P. gingivalis strains (p=0.007); the Er:YAG laser uniquely effective removing both bacterial strains. The titanium curette significantly altered the implant surface micro-texture. Neither the Er:YAG laser nor the chitosan brush significantly altered the implant surface. The three instrumentations appear to have a similar potential to remove P. gingivalis. The titanium curette significantly altered the microstructure of the implant surface.
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| 64. |
- Macdonald, Warren, 1954, et al.
(författare)
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Variation in surface texture measurements.
- 2004
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Ingår i: Journal of biomedical materials research. Part B, Applied biomaterials. - : Wiley. - 1552-4973. ; 70:2, s. 262-9
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Tidskriftsartikel (refereegranskat)abstract
- Surface texture influences cellular response to implants, implant wear, and fixation, yet measurement and reporting of surface texture can be confusing and ambiguous. Seven specimens of widely different surface textures were submitted to three internationally renowned laboratories for surface texture characterization. The specimens were from dental implants, orthopedic implants, and femoral heads. Areas to be measured were clearly marked; simplified instructions were supplied but specific measurement parameters were not requested. Techniques used included contact profilometry, two- and three-dimensional laser profilometry, and atomic force microscopy. Four to thirteen parameters were reported, 2D or 3D, including R(a) or S(a); only three were common to all centers. The results varied by as much as +/-300-1000%, depending on technique and surface type. Some surfaces were not measurable by some techniques. One dental implant surface was reported with R(a) of 0.17, 0.85, 1.9, and 4.4 microm. The CoCr femoral head ranged from an R(a) of 0.011 to 0.10 microm; the zirconia head from 0.006 to 0.05 microm. Similar variability was reported for the other parameters. Useful surface texture characterization requires reporting of all measurement parameters. Comparisons between studies may be compromised if differences in technique are not considered.
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| 65. |
- Mahmood, Deyar Jallal Hadi, et al.
(författare)
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Production tolerance of conventional and digital workflow in the manufacturing of glass ceramic crowns
- 2019
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 35:3, s. 486-494
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. To measure and compare the size of the cement gap of wax and polymer copings and final glass-ceramic crowns, produced from conventional and digital workflows, one additive and one subtractive. Methods. Thirty wax copings were made by conventional manual layering technique and modeling wax on stone models with spacer varnish simulating a cement spacer. The wax copings were embedded and press-cast in lithium disilicate glass ceramic. Thirty wax copings were produced by milling from a wax blank, i.e. subtractive manufacturing, and thirty polymer burn-out copings were produced by stereolithography, i.e. additive manufacturing. These copings were embedded and press-cast in lithium disilicate glass ceramic in the same manner as the conventional group. The fit of the wax/polymer copings and subsequent crowns was checked using an impression replica method. Mean values for cement gap for marginal, axial, and occlusal areas were calculated and differences were analyzed using Student's t-test. Results. There were significant differences in mean values for accuracy/production tolerance among different manufacturing techniques for both production stages: wax and polymer copings and final pressed glass-ceramic crowns. In general, crowns produced from a digital additive workflow showed smaller mean cement gaps than crowns produced from a conventional workflow or a digital subtractive workflow. Additive polymer copings showed significantly smaller cement gaps than milled wax copings (p <=.001) and conventional wax copings (p <=.001) in the axial area. In the occlusal area, both additive polymer copings and conventional wax copings showed significantly smaller cement gaps than milled wax copings (p = .002 and p <=.001 respectively). Crowns produced from conventional manual build-up wax copings showed significantly larger mean cement gaps than crowns produced from milled wax and additively manufactured polymer copings in the marginal and axial areas (p <=.001). Among the crowns with smaller cement gaps, crowns produced from additively manufactured polymer copings showed significantly smaller mean cement gaps than crowns produced from milled wax in the marginal and axial areas (p <=.001). In the occlusal areas, the differences in mean cement gaps were only statistically significant between crowns produced from conventional manual build-up wax copings and crowns produced from milled wax where the latter ones showed smaller mean cement gaps (p = .025). Significance. The present study suggests that an additive manufacturing technique produces smaller mean cement gaps in glass-ceramic crowns than a conventional or subtractive manufacturing technique. (C) 2019 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.
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| 66. |
- Meirelles, Luiz, 1974, et al.
(författare)
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A novel technique for tailored surface modification of dental implants - a step wise approach based on plasma immersion ion implantation.
- 2013
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Ingår i: Clinical oral implants research. - : Wiley. - 1600-0501 .- 0905-7161. ; 24:4, s. 461-467
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: A novel technique based on plasma immersion ion implantation (PIII) is presented to modify titanium implant surfaces. MATERIALS AND METHODS: Initially, the implants are cleaned with argon to remove contaminants and the nanostructures are created by the bombardment of the surface with a mix of noble gases. Desired crystal structure of the titanium is obtained by the implantation of oxygen on the contaminant-free surface with particular nanostructures. RESULTS: In this study, turned implants modified by PIII revealed a high density of rutile-TiO(2) nanostructures. Turned implants used as control revealed mainly microstructures and amorphous crystal structure. Surface roughness values were similar at the microscale for both turned and turned + PIII implants. Bone response was evaluated by removal torque tests of implants placed in the rabbit tibia and femur. After 4 weeks of healing, turned + PIII demonstrated higher removal torque values (P = 0.001) compared to turned implants. CONCLUSIONS: The presence of rutile-TiO(2) nanostructures may explain the improved bone formation to turned + PIII implants.
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| 67. |
- Meirelles, Luiz, 1974, et al.
(författare)
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Bone reaction to nano hydroxyapatite modified titanium implants placed in a gap-healing model
- 2008
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Ingår i: Journal Biomedical MAterials Research - A. - : Wiley. - 1549-3296 .- 1552-4965. ; 87:3, s. 624-631
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Tidskriftsartikel (refereegranskat)abstract
- Nanohydroxyapatite materials show similar chemistry to the bone apatite and depending on the underlying topography and the method of preparation, the nanohydroxyapatite may simulate the specific arrangement of the crystals in bone. Hydroxyapatite (HA) and other CaP materials have been indicated in cases in which the optimal surgical fit is not achievable during surgery, and the HA surface properties may enhance bone filling of the defect area. In this study, very smooth electropolished titanium implants were used as substrata for nano-HA surface modification and as control. One of each implant (control and nano HA) was placed in the rabbit tibia in a surgical site 0.7 mm wider than the implant diameter, resulting in a gap of 0.35 mm on each implant side. Implant stability was ensured by a fixating plate fastened with two side screws. Topographical evaluation performed with an optical interferometer revealed the absence of microstructures on both implants and higher resolution evaluation with AFM showed similar nanoroughness parameters. Surface pores detected on the AFM measurements had similar diameter, depth, and surface porosity (%). Histological evaluation demonstrated similar bone formation for the nano HA and electropolished implants after 4 weeks of healing. These results do not support that nano-HA chemistry and nanotopography will enhance bone formation when placed in a gap-healing model. The very smooth surface may have prevented optimal activity of the material and future studies may evaluate the synergic effects of the surface chemistry, micro, and nanotopography, establishing the optimal parameters for each of them.
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| 68. |
- Meirelles, Luiz, 1974, et al.
(författare)
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Effect of hydroxyapatite and titania nanostructures on early in vivo bone response
- 2008
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Ingår i: Clinical Implant Dentistry and Related Research. - : Wiley. - 1708-8208 .- 1523-0899. ; 10:4, s. 245-254
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Hydroxyapatite or titania nano structures were applied on smooth titanium implant cylinders. The aim was to investigate whether nano HA may result in enhanced osseointegration compared to nano titania structures. Material and Methods: Surface topography evaluation included detailed characterization of nano size structures present at the implant surface combined with surface roughness parameters at the micro- and nano- meter level of resolution. Microstructures were removed from the surface to ensure that bone response observed was dependent only on the nanotopography and/or chemistry of the surface. Early in vivo bone response (4 weeks) evaluation was investigated in a rabbit model. Results: In the present study, nano titania coated implants showed an increased coverage area and feature density, forming a homogenous layer compared to nano HA implants. Bone response observed at 4 weeks could not be explained by the surface chemistry. New formed bone connected to the original cortical bone demonstrated an increase of 24% for the nano titania compared to the nano HA implant, although the difference was not statistically significant. Conclusion: Thus, no evidence of enhanced bone formation to nano hydroxyapatite modified implants was observed compared to nano titania modified implants. The presence of specific nano structures; dependent on the surface modification exhibiting different size and distribution did modulate in vivo bone response.
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| 69. |
- Meirelles, Luiz, 1974, et al.
(författare)
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Increased bone formation to unstable nano rough implants
- 2007
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Ingår i: Clin Oral Implants Res. - : Wiley. - 0905-7161. ; 18:3
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Tidskriftsartikel (refereegranskat)abstract
- Early bone response to cylindrical smooth titanium implants (S(a)=0.1 microm) inserted into the rabbit tibia was compared in a stable and nonstable regime. Surface roughness parameters were calculated from measurements obtained with optical interferometry and atomic force microscopy. Contrary to our hypothesis, the nonstable implant showed higher bone to metal contact and increased bone area in the endosteal region compared with the stable implant after 4 weeks of healing. Bone area measurements in the cortical region revealed similar values. Primitive woven bone was found in close contact with both implants, but significantly more with the nonstable implant. Finding more bone-to-implant contact (BIC) need not necessarily indicate that unstable implants were more strongly integrated. Primitive bone stage development observed indicates less strong implant anchorage than could be expected from BIC percentage alone. Stable implant design used in this study is a reliable model to evaluate submicron and nanostructures in vivo, as implant stability was achieved in the absence of microirregularaties.
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| 70. |
- Meirelles, Luiz, 1974, et al.
(författare)
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Nano hydroxyapatite structures influence early bone formation
- 2008
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Ingår i: Journal Biomedical Materials Research - A. - : Wiley. - 1549-3296 .- 1552-4965. ; 87:2, s. 299-307
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Tidskriftsartikel (refereegranskat)abstract
- In a study model that aims to evaluate the effect of nanotopography on bone formation, micrometer structures known to alter bone formation, should be removed. Electropolished titanium implants were prepared to obtain a surface topography in the absence of micro structures, thereafter the implants were divided in two groups. The test group was modified with nanosize hydroxyapatite particles; the other group was left uncoated and served as control for the experiment. Topographical evaluation demonstrated increased nanoroughness parameters for the nano-HA implant and higher surface porosity compared to the control implant. The detected features had increased size and diameter equivalent to the nano-HA crystals present in the solution and the relative frequency of the feature size and diameter was very similar. Furthermore, feature density per m2 showed a decrease of 13.5% on the nano-HA implant. Chemical characterization revealed calcium and phosphorous ions on the modified implants, whereas the control implants consisted of pure titanium oxide. Histological evaluation demonstrated significantly increased bone formation to the coated (p < 0.05) compared to uncoated implants after 4 weeks of healing. These findings indicate for the first time that early bone formation is dependent on the nanosize hydroxyapatite features, but we are unaware if we see an isolated effect of the chemistry or of the nanotopography or a combination of both.
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