A New Highly Hydrophilic Electrochemical Implant Titanium Surface: A Histological and Biomechanical In Vivo Study.

PURPOSE: The aim was to compare the osseointegration degree and secondary implant stability between implants with different surface treatments. MATERIALS AND METHODS: A novel electrochemical treatment was applied to modify the sandblasted and acid-etched surface (SLA) to obtain the new hydrophilic Feeling (FEL) surface presenting a highly soluble and homogenous film made of calcium and phosphorus nanocrystals. Twenty 3.8 × 10-mm dynamix implants (Cortex) were inserted in sheep iliac crests. Sheep were killed after 2 months. Bone-to-implant contact percentage (%BIC) and biomechanical parameters, such as implant stability quotient (ISQ) and value of actual micromotion (VAM), were evaluated for each implants. RESULTS: No implant failures were observed. Implants of test group showed %BIC value 30% higher in respect with control group (P = 0.001). No statistical differences were detected between the 2 groups in VAM and ISQ values. CONCLUSION: Both surface treatments were highly osteoconductive because they were able to significantly increase the bone density onto implant surface in respect with that in which they were inserted (D4 bone density). The hydrophilic FEL surface demonstrated an increase of about 216% in BIC in respect with host bone density and an additional 30% more in respect with SLA surface. Faster osseointegration process is desirable in case of early implant loading protocol.

Tribological and mechanical performance evaluation of metal prosthesis components manufactured via metal injection molding.

The increasing number of total joint replacements, in particular for the knee joint, has a growing impact on the healthcare system costs. New cost-saving manufacturing technologies are being explored nowadays. Metal injection molding (MIM) has already demonstrated its suitability for the production of CoCrMo alloy tibial trays, with a significant reduction in production costs, by holding both corrosion resistance and biocompatibility. In this work, mechanical and tribological properties were evaluated on tibial trays obtained via MIM and conventional investment casting. Surface hardness and wear properties were evaluated through Vickers hardness, scratch and pin on disk tests. The MIM and cast finished tibial trays were then subjected to a fatigue test campaign in order to obtain their fatigue load limit at 5 millions cycles following ISO 14879-1 directions. CoCrMo cast alloy exhibited 514 HV hardness compared to 335 HV of MIM alloy, furthermore it developed narrower scratches with a higher tendency towards microploughing than microcutting, in comparison to MIM CoCrMo. The observed fatigue limits were (1,766 ± 52) N for cast tibial trays and (1,625 ± 44) N for MIM ones. Fracture morphologies pointed out to a more brittle behavior of MIM microstructure. These aspects were attributed to the absence of a fine toughening and surface hardening carbide dispersion in MIM grains. Nevertheless, MIM tibial trays exhibited a fatigue limit far beyond the 900 N of maximum load prescribed by ISO and ASTM standards for the clinical application of these devices.

Osseointegration of multiphase anodic spark deposition treated porous titanium implants in an ovine model.

Modification of titanium oxide by multiphase anodic spark deposition (ASD) has the potential to increase bioactivity and hasten osseointegration and biological fixation in uncemented arthroplasty. This study assessed the in vivo performance of control (Ti), plasma-sprayed HA-coated (TiHA) and ASD (Biospark) treated (TiAn) porous titanium implants with a solid core using a standard uncemented implant fixation sheep model. Cortical interfacial shear-strength and bone ingrowth in cortical and cancellous sites were quantified following 12 weeks in situ. Ultimate shear-strength for the Ti, TiHA and TiAn coatings was 33±9.5, 35.4±8.4 and 33.8±7.8 MPa, respectively, which was limited by coating delamination. ASD treatment was associated with significantly higher mean bone ingrowth at both sites. These results support the osteoconductive potential of the BioSpark treatment of porous titanium.

Effect of a multiphasic anodic spark deposition coating on the improvement of implant osseointegration in the osteopenic trabecular bone of sheep.

PURPOSE: Anodic spark deposition techniques have been effectively applied to achieve a microporous morphology on metals. To investigate the effect of a new anodic spark deposition-based treatment in the enhancement of titanium implant osseointegration in trabecular bone of aged and ovariectomized sheep, a histomorphometric and microhardness study was carried out. MATERIALS AND METHODS: Ten sheep were divided into 2 groups. Five were submitted to a bilateral ovariectomy to induce an estrogen-deficiency osteopenia (Ovariectomized), and 5 were left untreated (Aged). Twenty-four months later, they underwent a bilateral implantation of commercially pure titanium screw threads in the lateral surface of femoral condyles: electrochemically treated titanium (SP) and acid-etching treated titanium (BioRough). Twelve weeks after the second operation, the animals were sacrificed and femur segments and iliac crest biopsy specimens were examined for histomorphometric and microhardness evaluations. RESULTS: The histomorphometry of the trabecular bone of the iliac crest biopsy specimens and that around screws showed marked signs of bone rarefaction in the Ovariectomized group when compared to the Baseline and Aged groups. Significantly greater bone-implant contact was observed for SP implants in comparison with BioRough implants in both the Aged (P < .001) and Ovariectomized (P < .01) groups. No significant differences in terms of microhardness were found between SP and BioRough implants within the Aged group, while a significantly higher Bone Maturation Index was observed for SP in the Ovariectomized group (P < .05). CONCLUSIONS: The novel electrochemical treatment SP produced the most promising results and was able to introduce substantial improvements in achieving the fast and stable osseointegration of implants in osteopenic bone.

In vitro assessment of the osteointegrative potential of a novel multiphase anodic spark deposition coating for orthopaedic and dental implants.

Hydroxyapatite coatings have been proven to improve the osteointegration of metal implants through a tight binding to the bone mineral phase as well as through favorable osteoblast adhesion and proliferation onto the implant surface. However, hydroxyapatite coatings are not stable and they tend to delaminate from the metal surface when challenged by the mechanical stresses experienced by the implant. Recently, a new multiphase anodic spark deposition (ASD) method has been optimized where the formation of a thick oxide film is followed by the deposition of a calcium phosphate mineral phase and its etching by alkali. The data in this paper demonstrate that this novel type of coating, BioSpark, improves the material osteointegration potential when compared to conventional ASD while offering more mechanical stability. A faster mineralization was obtained by incubation in simulated body fluids and osteoblasts showed better adhesion, proliferation, differentiation, and collagen production. These performances were related to the surface morphology, to the film calcium/phosphate ratio and its surface oxygen content, as well as to a preferential binding of structural proteins such as fibronectin.

Metal injection molding as enabling technology for the production of metal prosthesis components: electrochemical and in vitro characterization.

Industrial manufacturing of prosthesis components could take significant advantage by the introduction of new, cost-effective manufacturing technologies with near net-shape capabilities, which have been developed during the last years to fulfill the needs of different technological sectors. Among them, metal injection molding (MIM) appears particularly promising for the production of orthopedic arthroplasty components with significant cost saving. These new manufacturing technologies, which have been developed, however, strongly affect the chemicophysical structure of processed materials and their resulting properties. In order to investigate this relationship, here we evaluated the effects on electrochemical properties, ion release, and in vitro response of medical grade CoCrMo alloy processed via MIM compared to conventional processes. MIM of the CoCrMo alloy resulted in coarser polygonal grains, with largely varying sizes; however, these microstructural differences between MIM and forged/cast CoCrMo alloys showed a negligible effect on electrochemical properties. Passive current densities values observed were 0.49 µA cm(-2) for MIM specimens and 0.51 µA cm(-2) for forged CoCrMo specimens, with slightly lower transpassive potential in the MIM case; open circuit potential and Rp stationary values showed no significant differences. Moreover, in vitro biocompatibility tests resulted in cell viability levels not significantly different for MIM and conventionally processed alloys. Although preliminary, these results support the potential of MIM technology for the production of CoCrMo components of implantable devices.

A novel multiphase anodic spark deposition coating for the improvement of orthopedic implant osseointegration: an experimental study in cortical bone of sheep.

The effect of a new three-step anodic spark deposition process, labeled TiSpark, including two consecutive treatments performed first in a P solution and second in Ca solution, followed by an additional alkali etching step, was investigated for the improvement of osseointegration of commercial grade 2 titanium, machined (Ti) or Al(2)O(3) sandblasted (Ti-SA), cylindrical implants (12 mm in length and 4 mm in diameter) in cortical bone of 12 adult sheep. Histomorphometric and microhardness measurements were carried out at each experimental time (4, 8, and 12 weeks) to quantify the bone-to-implant contact around the implants as well as the newly bone hardness and bone maturation index. TiSpark treated surfaces were covered by a thick layer of crystalline anatase TiO(2) and by a further Ca/P layer. Bone tissue extends and grows on the surface of the TiSpark treated implants without any fibrous tissue, enhancing the short-term osseointegration properties of implant. Bone mineralization rate was also influenced by the chemical composition of implants and sandblasted materials presented the lowest bone maturation rate at the interface. Data suggests that the TiSpark treatment produces a modification of the Ti surface, which presents good bioactivity and may be suitable for achieving a stable implant osseointegration.

Apatite formation and cellular response of a novel bioactive titanium.

The modification of titanium and titanium alloy surface properties by chemical and electrochemical techniques has opened new possibilities to improve the bioactivity and, in general, the biological performance of the implants once in vivo. One of the main aims is the achievement of a surface oxide layer that stimulates hydroxylapatite mineralization and, also, shows osteoconductive properties once in the host. In the present study, two different bioactive surfaces have been prepared following the method purposed by the group of Kokubo and a new method, BioSpark, involving high voltage anodic polarisation and alkali etching both on surface mineralization potential. The aim of the present work was to evaluate and compare the mineralization capability and the early cell response of titanium modified with a new bioactive method and with a well-known and widely tested biomimetic treatment, both compared to non treated titanium. Physical and chemical (energy dispersion spectroscopy, thin film X-ray diffractometry) and morphological (scanning electron microscopy) characterisation of the novel surface features has been performed. Also the effect of the novel surface properties on both hydroxyapatite precipitation and early cellular response has been investigated using in vitro models. The results have shown that both treatments produce an active outer layer on titanium but do not impair cells activity and support osteoblasts processes. BioSpark showed high bioactivity and good mineral phase deposition even after early incubation time, these properties were found in Kokubo's surface as previously published. Mineralisation mechanisms of the two materials were different, and while this mechanisms was well characterised and reported for Kokubo's surface, it was still unclear for BioSpark. In this paper an explanation was given and catalytic properties of the latter surface was bound to both well known crystal titanium oxide exhibiting anatase lattice and a certain level of calcium and phosphorus doping, which promoted chemical and physical variation in anatase properties. At the same time early osteoblasts response to Kokubo's and BioSpark's surface was characterised and, no significant differences was found.

In vitro and in vivo performance of a novel surface treatment to enhance osseointegration of endosseous implants.

OBJECTIVE: This article shows the in vitro and in vivo characterization of a new biomimetic treatment developed to enhance the osseointegration of titanium dental implants. STUDY DESIGN: A novel biomimetic treatment of titanium was developed. Its physicochemical properties and biologic and in vivo performance were considered and studied. Mineralization capability was assessed by soaking test in simulated body fluid solution, and cytocompatibility was assessed using osteoblast-like MG63 cell culture. Histomorphometric analysis was performed at 3 time points using a sheep animal model. RESULTS: In vitro tests confirmed the biomimetic potential of the considered novel treatment. Histomorphometric analysis indicated its potential for rapid and good-quality osseointegration. CONCLUSION: The in vitro and in vivo test results indicated that the proposed novel treatment possesses a significant potential to increase the rate of osteointegration of titanium for endosseous dental implants.

Physical and biological characterizations of a novel multiphase anodic spark deposition coating to enhance implant osseointegration.

The present study assessed in vitro the short-term cellular response to surface physico-chemical properties of a new, purposed bioactive surface treatment called BioSpark performed on simply machined and on sand-blasted titanium. Material characterisation was carried out using scanning electron microscopy, energy dispersion spectroscopy, laser profilometry, and thin film X-ray diffraction. The in vitro biological study showed a suitable cellular response with adhesion and spreading level comparable for all the tested specimens. The proliferation analysis demonstrated that all the surfaces successfully supported cellular colonisation; in particular, higher cellular proliferation activity was observed on the BioSpark-treated materials, with values higher than machined titanium. The results suggest that the BioSpark treatment represents a smart way to enhance osteoblastic cellular colonisation and thus improve osteointegration processes of machined and sandblasted titanium for orthopaedic and dental implants.