Biological response of laser macrostructured and oxidized titanium alloy: an in vitro and in vivo study.

PURPOSE: To assess both the in vitro and in vivo biological response of a laser modified surface in an integrated manner. A combined innovative approach applies lasers to macrostructure as well as to oxidize the surface of titanium alloy implants. MATERIALS AND METHODS: A Nd:YAG marking and ArF excimer lasers were used for macrostructuring and UV-oxidizing the surface of Ti6Al4V discs, respectively. Human fetal osteoblastic cell culture and a sheep tibia model were used to assess the cell response and the osseogeneration capability of as-machined, laser macrostructured and laser macrostructured and oxidized surfaces. RESULTS: In vitro: Laser macrostructuration alone did not promote cell response. Cellular proliferation was enhanced by the additional UV laser oxidation. In vivo: A greater significant percentage of bone-implant contact was obtained for both laser treated surfaces compared to machine-turned control samples, three months after implantation, in spite of the low cellular response for macrostructured samples. The use of sheep model for six months appears to be less adequate for a comparison because of the high level of bone integration in all samples. In spite of the often reported positive effect of titanium oxidation on the triggering of faster osseointegration, in this experiment the additional UV laser oxidation did not lead to a significant in vivo improvement. CONCLUSIONS: Laser macrostructuration of titanium alloy surfaces appears to promote bone apposition and may therefore constitute a promising surface modification strategy. In animal models, the natural process of titanium surface oxidation, because of physiologic fluids, alters properties observed in vitro with cells.

Effect of nanotubes and apatite on growth factor release from PLLA scaffolds.

There is an evident clinical need for artificial bone restorative materials. In this respect, novel composites based on poly(L-lactic acid) (PLLA) have been described. The bone response of such polymer-based composites is usually improved by the addition of bone morphogenetic protein-2 (BMP-2). However, released BMP-2 is cleared almost immediately from the site of implantation by diffusion, whereas a prolonged retention of BMP-2 onto the scaffold has been suggested to be more favourable. Besides the ability to improve the mechanical strength and osteoconductivity of polymeric scaffolds, both carbon nanotubes (CNTs) and microhydroxyapatite (µHA) have been described to facilitate such retention of BMP-2 when incorporated into a composite scaffold. Therefore, in the current study, radiolabelled BMP-2 was loaded onto plain PLLA and composite PLLA-CNT-µHA scaffolds. Subsequently, the scaffolds were implanted subcutaneously for 5 weeks in rats and BMP-2 release was measured. Release started with an initial phase of quick release, followed by a gradual release of BMP-2. Both scaffold types comprised the same in vivo release properties for BMP-2. The bioactivity of the BMP-2 remained unaltered. It can be concluded that incorporated CNTs and µHA did not affect BMP-2 release from composite scaffold materials.

Genetic profiling of osteoblast-like cells cultured on a novel bone reconstructive material, consisting of poly-L-lactide, carbon nanotubes and microhydroxyapatite, in the presence of bone morphogenetic protein-2.

In bone tissue engineering composite materials have been introduced, combining a degradable polymer matrix with, for instance, carbon nanotubes (CNTs) to improve mechanical properties or with microhydroxyapatite (µHA) to improve osteoconduction. The addition of bone morphogenetic protein-2 (BMP-2) can further improve the biological response to the material. However, the influence of such an elaborate composite formation on osteoprogenitor cells is unknown. To examine this, rat bone marrow (RBM) cells were cultured on porous poly-L-lactic acid and composite scaffolds, with or without added BMP-2. Cell proliferation and differentiation were studied using DNA, alkaline phosphatase and scanning electron microscopic analysis. Further, genetic profiles were examined by microarray investigation. Results showed that the composite scaffold had no significant effect on the proliferation of RBM cells, but indicated a negative effect on cell differentiation. The addition of BMP-2 also had no significant effect on the proliferation of RBM cells, but differentiation towards the osteogenic lineage was confirmed. In the arrays results, the addition of BMP-2 alone led to the expression of genes involved in (minor) inflammation. The composite scaffold, and even more distinctly the combination of the composite scaffold with BMP-2, led to the expression of genes, based on gene ontology, connected to tumorigenesis. Therefore, CNT- and µHA-containing composite materials are not recommended as a bone restorative material.

Histomorphometric study of ion implantation and diamond-like carbon as dental implant surface treatments in beagle dogs.

PURPOSE: Improvements in the bone-implant interface can provide clinical benefits, such as increasing the amount of bone in contact with the implant and shortening the time required to achieve sufficient bone appositioning to allow early prosthetic loading. The present study describes the results obtained with 2 new surface treatments: (a) CO ion implantation; and (b) diamond-like carbon (DLC) coating. MATERIALS AND METHODS: Each group (ion implantation, DLC, and the control group, turned titanium) consisted of 12 samples. Beagle dogs subjected to previous partial edentulation were used. Dual histologic evaluation was made of percentage bone-implant contact (% BIC) of all samples based on conventional histomorphometric analysis and environmental scanning electron microscopy (ESEM). RESULTS: The results obtained after 3 and 6 months of dental implant placement showed greater and faster bone integration in the CO ion implantation group (61% and 62% BIC, respectively) compared with the DLC group (47% and 50%); the data corresponding to the ion implanted samples were statistically significant compared with the control group (33% and 49% BIC after 3 and 6 months, respectively). CONCLUSIONS: The results showed improved % BIC for implants with ion-implanted surfaces in comparison to DLC coating and machined controls. Furthermore, bone integration appeared to be accelerated in the ion implantation group, since high % BIC values were recorded in the early stages after in vivo implantation.

Ion implantation: surface treatment for improving the bone integration of titanium and Ti6Al4V dental implants.

Dental implants subjected to surface treatment have shown better bone integration than implants which have only been turned (machined). Three main types of treatment are presently available: the addition of material or coating, the removal of material, and surface modification. Ion implantation corresponds to the third approach. A histomorphometric study is made following the rabbit tibial bone placement of 88 commercial dental implants of pure titanium and Ti6AI4V subjected to surface treatment in the form of different ion implants (C+, CO+, N+, Ne+). Light microscopic, scanning electron microscopic (SEM), electron microsonde (EDS) and X-ray photoelectron spectroscopy (XPS) studies were made. The results indicate improved bone integration (expressed as percentage bone-implant contact) in those specimens subjected to ion implantation versus the non-treated controls, the difference being statistically significant for the groups treated with C+ and CO+. In these groups, XPS showed a Ti-O-C junction (bone-implant interface) involving covalent type bonds, these being stronger and more stable than the ion-type bonds usually established between the titanium oxide and bone.