Nanostructured titanium has become a useful material for biomedical applications such as dental implants. Certain surface properties (grain size, roughness, wettability) are highly expected to promote cell adhesion and osseointegration. The aim of this study was to compare the biocompatibilities of several titanium materials using human osteoblast cell line hFOB 1.19. Eight different types of specimens were examined: machined commercially pure grade 2 (cpTi2) and 4 (cpTi4) titanium, nanostructured titanium of the same grades (nTi2, nTi4), and corresponding specimens with laser-treated surfaces (cpTi2L, cpTi4L, nTi2L, nTi4L). Their surface topography was evaluated by means of scanning electron microscopy. Surface roughness was measured using a mechanical contact profilometer. Specimens with laser-treated surfaces had significantly higher surface roughness. Wettability was measured by the drop contact angle method. Nanostructured samples had significantly higher wettability. Cell proliferation after 48 hours from plating was assessed by viability and proliferation assay. The highest proliferation of osteoblasts was found in nTi4 specimens. The analysis of cell proliferation revealed a difference between machined and laser-treated specimens. The mean proliferation was lower on the laser-treated titanium materials. Although plain laser treatment increases surface roughness and wettability, it does not seem to lead to improved biocompatibility.

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This paper describes the mechanical properties and microstructure of commercially pure titanium (Grade 2) processed with Conform severe plastic deformation (SPD) and rotary swaging techniques. This technology enables ultrafine-grained to nanocrystalline wires to be produced in a continuous process. A comprehensive description is given of those properties which should enable straightforward implementation of the material in medical applications. Conform SPD processing has led to a dramatic refinement of the initial microstructure, producing equiaxed grains already in the first pass. The mean grain size in the transverse direction was 320 nm. Further passes did not lead to any additional appreciable grain refinement. The subsequent rotary swaging caused fine grains to become elongated. A single Conform SPD pass and subsequent rotary swaging resulted in an ultimate strength of 1060 MPa and elongation of 12%. The achieved fatigue limit was 396 MPa. This paper describes the production possibilities of ultrafine to nanocrystalline wires made of pure titanium and points out the possibility of serial production, particularly in medical implants.

Purpose: At present, materials research in the area of SPD (severe plastic deformation) processes is very intensive. Materials processed by these techniques show better mechanical properties and have finer grain when compared to the input feedstock. The refined microstructure may be ultrafine-grained or nanostructured, where the grain size becomes less than 100 nm. One of the materials used for such processes is CP (commercially pure) titanium of various grades, which is widely used for manufacturing dental implants. The article deals with one of the technologies available for the production of ultrafine-grained titanium: Conform technology. CP titanium processed by CONFORM technology exhibits improved mechanical properties and very favourable biocompatibility, due to its fine-grained structure. The article presents the current experience in the production of ultrafine CP titanium using this technology. The main objective of this article is describing the behaviour of CP titanium during forming in the Conform device and its subsequent use in dental implantology. Design/methodology/approach: In the present study, commercially pure Grade 2 titanium was processed using the CONFORM machine. The numerical simulation of the process was done using FEM method with DEFORMTM software. The evaluation was performed by simple tensile testing and transmission electron microscopy. The first conclusions were derived from the determined mechanical properties and based on analogies in available publications on a similar topic. Findings: This study confirmed that the SPD process improves mechanical properties and does not impair the ductility of the material. The CONFORM process enables the continuous production of ultrafine-grained or nanostructured materials. Research limitations/implications: At the present work, the results show the possible way of continuous production of ultrafine-grained or nanostructured materials. Nevertheless, the further optimization is needed in order to improve the final quality of wires and stabilize the process. As these factors will be solved, the technology will be ready for the industry. Practical implications: The article gives the practical information about the continuous production of ultrafine-grained pure titanium Grade 2 and the possibility of use this material for dental implants. Originality/value: The present paper gives information about the influence of the CONFORM technology on final mechanical and structural properties with the emphasis on technological aspects

SPD (severe plastic deformation) processing of materials provides a great potential associated with the enhancement of their properties by refining the initial grain structure. The present experiments involved mechanical working of commercial-purity titanium (Ti Grade 2) with the CONFORM SPD technique, which is one of the SPD methods, and with rotary swaging. The objective was to process the material at as low temperatures as possible in order to avoid softening processes and, therefore, to achieve the maximum strengthening through a microstructure refinement. Three passes through a CONFORM SPD machine were completed and the resulting ultimate strength was 673 MPa. The average grain size was 330 nm. The greatest improvement of the mechanical properties was achieved in the first pass. In the subsequent passes, the contributions were minor. The processing in the CONFORM SPD machine did not impair the ductility of the material. Subsequently, the wires were rotary swaged. The ultimate strength achieved was 1070 MPa. The response of the properties to this forming method was markedly different. The reason is that rotary swaging does not belong to SPD techniques. It causes rapid work hardening and reduces the ductility of the material. The workpiece was subsequently investigated with the aid of several techniques. Light and transmission electron microscopy and X-ray diffraction were employed for evaluating the grain size, distribution and orientation. Keywords: equal-channel angular pressing, CONFORM SPD technique, rotary swaging, titanium, extrusion Velika plasti~na deformacija (angl. SPD) pri obdelavi materialov omogo~a veliko mo`nosti, povezane z izbolj{anjem njihovih lastnosti z izbolj{avo izvorne strukture zrn. Pri~ujo~i preizkus je vklju~eval mehansko obdelavo komercialno dostopnega~istega titana (Ti Grade 2) s CONFORM SPD-tehniko, ki je ena od SPD-metod, in s kovanjem. Namen je bil, da bi se material obdelalo pri~im ni`jih temperaturah, kot je mogo~e, da bi se izognili procesom meh~anja in, da bi dosegli maksimalno krepitev s prei{~enjem strukture. Narejeni so bili trije nizi v CONFORM SPD-stroju in kon~na mo~je dosegla 673 MPa. Povpre~na velikost zrn je bila 330 nm. Najve~je izbolj{ave mehanskih lastnosti so bile dose`ene v prvem nizu. V slede~ih nizih so bile le-te manj{e. Obdelava v CONFORM SPD-stroju ni {kodovala duktilnosti materiala. Posledi~no so bile`ice zvite. Kon~na mo~je bila 1070 MPa. Odziv lastnosti na to metodo oblikovanja je bil izrazito druga~en. Razlog je v tem, da rotacijsko zvijanje ne sodi v tehnike SPD. Rotacijsko zvijanje povzro~i hitro utrjevanje in zmanj{uje duktilnost materiala. Vzorec je bil nato raziskan s pomo~jo vet ehnik. Za ovrednotenje velikosti, razporeditve in orientacije zrn, sta bili uporabljeni transmisijska elektronska mikroskopija in rentgenska difrakcija.