Iñigo Braceras

Improved osseointegration in ion implantation-treated dental implants

Abstract Implants for knee, hip and dental part replacement are becoming increasingly used in surgery. Unfortunately, their use is sometimes accompanied by failure due to infection, inflammation, integration problems with the surrounding tissues or bone, and implant failure due to mishandling. Surface treatment, such as ion implantation, has been identified as a good candidate to modify the surface properties of the implant to significantly improve its osseointegration. This work reports on the ion implantation of light ions in commercial Ti6Al4V dental implants and subsequent osseointegration tests. Various light ions were implanted (C, N, CO, Ne) with energy ranging from 45 to 100 keV and doses up to 5×10 17 ions/cm 2 . Both ion-implanted and control dental implants were inserted in the tibial plateau of adult rabbits, the epiphysis and diaphysis of the tibia for the evaluation of their degree of osseointegration. After 3 months the implants were extracted and several histological sections were prepared from whole bones for evaluation of their osseointegration in the tibia. In addition, the surface of the implant, and the interface between the bone and the implant were examined by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) techniques. Some ion implantation treatments did not significantly change the performance of the dental implants relative to the untreated implants, while tests showed that the ion implantation of CO remarkably improved the osseointegration properties, i.e. the percentage of bone and implant in contact.

In vivo low-density bone apposition on different implant surface materials

During osseointegration, new bone may be laid down on the implant surface and/or on the old bone surface; the former is known as contact osteogenesis and the latter as distance osteogenesis. Implant surface topography and material composition affect this process. The present study evaluates Ca and P apposition onto three different dental implant material surfaces (carbon monoxide (CO) ion implantation on Ti6Al4V, sand blasting and acid etching on commercially pure titanium and untreated Ti6Al4V) on the mandibles of beagles after healing periods of 3 and 6 months. Energy dispersive spectroscopy is useful for identifying low-density bone relative to surrounding mature bone, allowing for discrimination of the osteogenesis source. Low-density bone was only found at the apical end; there was none on the surface of untreated implants. Low-density bone arising from mature bone towards the implant at month 3 (i.e. distance osteogenesis) was only present on the CO ion implanted samples, due to the modification of the surface nano-topography and the chemistry and structure of the material.

Improvement of osseointegration of titanium dental implant surfaces modified with CO ions: a comparative histomorphometric study in beagle dogs ☆

The aim of this study was to compare carbon-oxygen (CO) ion implantation as a surface treatment with diamond-like carbon and commercially treated implants, including double acid-etched (Osseotite), oxidized (TiUnite) and sandblasted and acid-etched (SLA), using machine-turned titanium implants as control. A total of 72 dental implants divided into 6 groups were placed in the mandibles of 12 beagle dogs. Evaluation was performed by conventional light transmission microscopy and environmental scanning electron microscopy (ESEM). The histological results obtained via ESEM demonstrated bone-implant contact percentage (%BIC) for implants treated with CO ion implantation of 61% and 62% at 3 and 6 months, respectively. At the same time points, the values were 48% and 45% for double acid-etched, 46% and 52% for sandblasted and acid-etched, 55% and 46% for oxidized, and 33% and 49% for machine-turned titanium control implants. Values of %BIC were statistically significantly higher in implants treated with CO ion implantation compared to the commercially treated implant group (p=0.002 and p=0.025) and the control implants (p=0.001 and p=0.032) at 3 and 6 months, respectively. No significant differences were observed between the three groups of commercially treated implants. The larger %BIC of the ion-implanted group was observable at an early stage.

Comparison of Physical-chemical and Mechanical Properties of Chlorapatite and Hydroxyapatite Plasma Sprayed Coatings

Chlorapatite can be considered a potential biomaterial for orthopaedic applications. Its use as plasma-sprayed coating could be of interest considering its thermal properties and particularly its ability to melt without decomposition unlike hydroxyapatite. Chlorapatite (ClA) was synthesized by a high-temperature ion exchange reaction starting from commercial stoichiometric hydroxyapatites (HA). The ClA powder showed similar characteristics as the original industrial HA powder, and was obtained in the monoclinic form. The HA and ClA powders were plasma-sprayed using a low-energy plasma spraying system with identical processing parameters. The coatings were characterized by physical-chemical methods, i.e. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, including distribution mapping of the main phases detected such as amorphous calcium phosphate (ACP), oxyapatite (OA), and HA or ClA. The unexpected formation of oxyapatite in ClA coatings was assigned to a side reaction with contaminating oxygenated species (O2, H2O). ClA coatings exhibited characteristics different from HA, showing a lower content of oxyapatite and amorphous phase. Although their adhesion strength was found to be lower than that of HA coatings, their application could be an interesting alternative, offering, in particular, a larger range of spraying conditions without formation of massive impurities.

Risk analysis and implants.

According to the Medical Devices Directive, both the preparation for clinical trials and marketing of implants require that a risk analysis is performed. This paper presents a risk analysis for a dental implant in the framework of the risk management process carried out for the preparation of a multi-centre clinical trial, where likely hazards, failure modes and their severities, probabilities and detectabilities are assessed, together with a review of the related scientific literature. The clinical study aimed to evaluate a new ion implantation-based implant surface designed for the promotion of more extensive and faster osseointegration.

MoSx lubricant coatings produced by PVD technologies

Abstract Among the different options for solid lubrication, MoS2 is probably the most attractive due to its extremely low friction levels. Recent developments in magnetron sputtering physical vapour deposition (PVD) technology have allowed the development of MoS2 composite thin films with more compact structures, low friction behaviour and enhanced wear resistance, reducing degradation by humidity. The present work provides an overview of recent developments in dry lubrication with MoS2 films deposited by modern sputtering PVD and how these MoS2 films alloyed with Ti or WC can outperform conventional unalloyed films not only under vacuum but also under atmospheric high humidity conditions. MoSx–WC composite films outperform MoSx–Ti films, showing endurance at 0·75 GPa as high as 1·2 million wear cycles, also significantly higher than the values obtained from unalloyed, conventional MoS2 thin solid films. The films also exhibit a steady state friction coefficient from 0·02 to 0·04. In addition, these films also show resistance to humid environment when tested under atmospheric conditions.

Degradable poly(ethylene glycol)-based hydrogels: synthesis, physico-chemical properties and in vitro characterization

Designing degradable hydrogels is complicated by the structural and temporal complexities of the gel and evolving tissue. A major challenge is to create scaffolds with sufficient mechanical properties to restore initial function while simultaneously controlling temporal changes in the gel structure to facilitate tissue formation. Poly(ethylene glycol) was used in this work, to form biodegradable poly(ethylene glycol)-based hydrogels with hydrolyzable poly-l-lactide segments in the backbone. Non-degradable poly(ethylene glycol) was also introduced in the formulation to obtain control of the degradation profile that encompasses cell growth and new tissue formation. The dependence on polymer composition was observed by higher degradation profiles and decreased mechanical properties as the content of degradable segments was increased in the formulation. Based on in vitro tests, no toxicity of extracts or biomaterial in direct contact with human adipose tissue stem cells was observed, and the ultraviolet light treatment did not affect the proliferation capacity of the cells.

Human study of ion implantation as a surface treatment for dental implants

This clinical study evaluated a new surface treatment of ion implantation with CO ions which has previously been subjected to extensive study in animal models. The aim of this work was to assess its effect in humans. Experimental mini-implants were used; half of their longitudinal surface was machined and the other half was treated with CO ion implantation. The study was conducted in healthy volunteer patients who required prosthetic treatment with dental implants, and in accordance with the corresponding ethics committees. Coinciding with the insertion of commercial implants for oral restoration, one or two mini-implants were placed in the upper maxillary tuberosity or in the retromolar trigone of the mandible. The mini-implants were removed with a trephine jointly with a small volume of surrounding bone after a 3-month period. Two evaluation methods were used and both showed a greater degree of bone integration in the mini-implant section that underwent CO ion implantation treatment in comparison with the non-treated surface: 62.9% vs. 57.9%, and 54.8% vs. 46.2%. In addition, no adverse reactions were observed in the surface treatment with CO ion implantation. These results confirm the positive benefits in humans, based on the findings obtained from previous animal experiments.

Ion Implantation as Surface Treatment for Osseointegration of Musculoskeletal Implants: From the Lab to the Clinic

A key process in a successful treatment of patients with a great variety of musculoskeletal implants requires a fast, reliable and consistent osseointegration. Among the parameters that affect this process, it is widely admitted that implant surface topography, surface energy and composition play an important role. Different surface modification techniques to improve osseointegration have been proposed and tested to date, but most focus on microscale features, and few control surface modifications at nanoscale. On the other hand, ion implantation modifies the outermost surface properties in relation to the nanotopography, chemical and physical characteristics at nanoscale. The meta-stable surface that results from the treatment, affects the adsorption of bio-molecules in the very first stages of the implant placement, and thus the signaling pathway that promotes the differentiation and apposition of osteoblast cells. This study aimed at assessing the performance, in terms of osseointegration levels and speed, of ion implanted titanium made implants. The study included several in vitro and in vivo tests. The latter, comprised different insertion periods and both experimental and commercial implants as comparative surfaces. The final stage of the study included clinical trials in human patients. In each and every case, bone integration improvement of tested materials/implants was achieved for the CO ion implanted samples. Furthermore, contact osteogenesis was observed in the ion implanted samples, unlike the Ti control samples, where only distance osteogenesis occurred, being this potentially one of the reasons for their faster healing and osseointegration process. Finally, the use of ion implantation as a surface modification tool that allows for evaluating the effects of nanotopography and composition changes independently is presented.