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Intervertebral implants should be designed with low load requirements, high friction coefficient and low elastic modulus in order to avoid the stress shielding effect on bone. Furthermore, the presence of a highly interconnected porous structure allows stimulating bone in-growth and enhancing implant-bone fixation. The aim of this study was to obtain bioactive porous titanium implants with highly interconnected pores with a total porosity of approximately 57 %. Porous Titanium implants were produced by powder sintering route using the space holder technique with a binder phase and were then evaluated in an in vivo study. The size of the interconnection diameter between the macropores was about 210 μm in order to guarantee bone in-growth through osteblastic cell penetration. Surface roughness and mechanical properties were analyzed. Stiffness was reduced as a result of the powder sintering technique which allowed the formation of a porous network. Compression and fatigue tests exhibited suitable properties in order to guarantee a proper compromise between mechanical properties and pore interconnectivity. Bioactivity treatment effect in novel sintered porous titanium materials was studied by thermo-chemical treatments and were compared with the same material that had undergone different bioactive treatments. Bioactive thermo-chemical treatment was confirmed by the presence of sodium titanates on the surface of the implants as well as inside the porous network. Raman spectroscopy results suggested that the identified titanate structures would enhance in vivo apatite formation by promoting ion exchange for the apatite formation process. In vivo results demonstrated that the bioactive titanium achieved over 75 % tissue colonization compared to the 40 % value for the untreated titanium.

The aim of this study is to compare the mechanical properties of three different dental restorations’ manufacturing processes (CADCAM milling, casting and laser sintering) generated by only one laboratory scanner focusing on marginal fit analysis and their mechanical properties. A chrome-cobalt (Cr-Co) alloy from the same batch was used for three different methods to make an implant abutment. This simulates a maxillary right first molar that was fixed in a hemi-maxillary stone model. Five scans were performed by each tested framework. Nine frameworks were manufactured for each manufacture procedure. Field-Emission Scanning Electron Microscope (FE-SEM) direct vision was used to marginal gap measurement in five critical points for each specimen. In order to fix the samples in the microscope chamber, the restorations were submitted at a compression load of 50 N. The samples always have the same orientation and conditions. The resolution of the microscope is 4 nm and it is equipped by J image software. The microstructure of the samples was also determined with the FE-SEM equipped with EDS-microanalysis. Roughness parameters were measured using White Light Interferometry (WLI). The arithmetical mean for the Ra and Rq of each sample was calculated. The samples were mechanically characterized by means of microhardness and flexural testing. Servo-hydraulic testing machine was used with cross-head rate of 1 mm/min. Two-way ANOVA statistical analysis was performed to determine whether the marginal discrepancies and mechanical properties were significantly different between each group (significance level p < 0.05). The overall mean marginal gap values were: from 50.53 ± 10.30 µm for the samples produced by CADCAM to 85.76 ± 22.56 µm for the samples produced by the casting method. Laser sintering presents a marginal gap of 60.95 ± 20.66 µm. The results revealed a statistically significant difference (p-value < 0.005) in the mean marginal gap between the CADCAM systems studied. The higher flexure load to fracture for these restorations were for CADCAM restoration and the lower was for the casting samples. For these restorations, CADCAM Restoration yielded a higher flexure load to fracture and Casting ones yielded the lower. Porosity and microstructure play a very important role in the mechanical properties.

In this study, highly-interconnected porous titanium implants were produced by powder sintering with different porous diameters and open interconnectivity. The actual foams were produced using high cost technologies: Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD), and spark plasma sintering, and the porosity and/or interconnection was not optimized. The aim was to generate a bioactive surface on foams using two different strategies, based on inorganic thermo-chemical treatment and organic coating by peptide adsorption, to enhance osseointegration. Porosity was produced using NaCl as a space holder and polyethyleneglicol as a binder phase. Static and fatigue tests were performed in order to determine mechanical behaviors. Surface bioactivation was performed using a thermo-chemical treatment or by chemical adsorption with peptides. Osteoblast-like cells were cultured and cytotoxicity was measured. Bioactivated scaffolds and a control were implanted in the tibiae of rabbits. Histomorphometric evaluation was performed at 4 weeks after implantation. Interconnected porosity was 53% with an average diameter of 210 µm and an elastic modulus of around 1 GPa with good mechanical properties. The samples presented cell survival values close to 100% of viability. Newly formed bone was observed inside macropores, through interconnected porosity, and on the implant surface. Successful bone colonization of inner structure (40%) suggested good osteoconductive capability of the implant. Bioactivated foams showed better results than non-treated ones, suggesting both bioactivation strategies induce osteointegration capability.

This study shows the potential risk of microfiltration between two different types of implant-abutment connections screwed at 45 Ncm: external and internal. For the first time the use of a mechanical artificial mouth is used with the values (compression and torsion loads with a frequency of 2 Hz) of the human chewing. The mechanical tests were performed with an artificial saliva at 37 oC. The microgap in the connection was measured by an Image Analysis software incorporated in a high resolution scanning electron microscopy. Implant connections were filled with methylene blue by using self-adjustable precision pipettes and the quantity of leakage was determined by high sensitivity spectometry. We showed that the internal connection has lower microgaps compared to the external ones and these microgaps increased with the number of mechanical cycles. The leakage of methylene blue was higher when the external connection was performed. Microgaps and the influence of the mechanical loads are very important for the long-term behavior avoiding the bacteria colonization in the dental implants. These aspects should be known by the implantologists.

In the field of implant dentistry there are several mechanisms by which metal particles can be released into the peri-implant tissues, such as implant insertion, corrosion, wear, or surface decontamination techniques. The aim of this study was to evaluate the corrosion behavior of Ti6Al4V particles released during implantoplasty of dental implants treated due to periimplantitis. A standardized protocol was used to obtain metal particles produced during polishing the surface of Ti6Al4V dental implants. Physicochemical and biological characterization of the particles were described in Part I, while the mechanical properties and corrosion behavior have been studied in this study. Mechanical properties were determined by means of nanoindentation and X-ray diffraction. Corrosion resistance was evaluated by electrochemical testing in an artificial saliva medium. Corrosion parameters such as critical current density (icr), corrosion potential (ECORR), and passive current density (iCORR) have been determined. The samples for electrochemical behavior were discs of Ti6Al4V as-received and discs with the same mechanical properties and internal stresses than the particles from implantoplasty. The discs were cold-worked at 12.5% in order to achieve the same properties (hardness, strength, plastic strain, and residual stresses). The implantoplasty particles showed a higher hardness, strength, elastic modulus, and lower strain to fracture and a compressive residual stress. Resistance to corrosion of the implantoplasty particles decreased, and surface pitting was observed. This fact is due to the increase of the residual stress on the surfaces which favor the electrochemical reactions. The values of corrosion potential can be achieved in normal conditions and produce corroded debris which could be cytotoxic and cause tattooing in the soft tissues.

Infections related to dental implants are a common complication that can ultimately lead to implant failure, and thereby carries significant health and economic costs. In order to ward off these infections, this paper explores the immobilization of triethoxysilylpropyl succinic anhydride (TESPSA, TSP) silane onto dental implants, and the interaction of two distinct monospecies biofilms and an oral plaque with the coated titanium samples. To this end, titanium disks from prior machining were first activated by a NaOH treatment and further functionalized with TESPSA silane. A porous sodium titanate surface was observed by scanning electron microscopy and X-ray photoelectron spectroscopy analyses confirmed the presence of TESPSA on the titanium samples (8.4% for Ti–N-TSP). Furthermore, a lactate dehydrogenase assay concluded that TESPSA did not have a negative effect on the viability of human fibroblasts. Importantly, the in vitro effect of modified surfaces against Streptococcus sanguinis, Lactobacillus salivarius and oral plaque were studied using a viable bacterial adhesion assay. A significant reduction was achieved in all cases but, as expected, with different effectiveness against simple mono-species biofilm (ratio dead/live of 0.4) and complete oral biofilm (ratio dead/live of 0.6). Nevertheless, this approach holds a great potential to provide dental implants with antimicrobial properties.