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The production of osseointegrating (bone bonding) surfaces on titanium screws by laser melt disruption.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development. Laser Nova AB.ORCID iD: 0000-0002-7706-6994
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
Department of Biomaterials, University of Gothenburg.
Department of Orthopaedic Surgery, University of California, San Francisco.
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2018 (English)In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 30, no 4, article id 042009Article in journal (Refereed) Published
Abstract [en]

Several techniques can be used to modify implant surfaces in order to accelerate bone growth around titanium implants. One method is to generate a surface structure which stimulates bone growth and remodelling. This paper describes and explains a non-ablative method for producing osseointegrating (structural and functional bone bonding) surfaces on titanium implants using laser processing. The focus is especially on surface texturing of dental implant screws, where the ability of a Nd:YAG laser to generate ‘splashy’ surfaces covered in resolidified micro scale droplets coated with nano-scale surface oxides is assessed. The surfaces produced were analysed by scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDS). It is concluded that laser processing using Q-pulsed Nd:YAG lasers can generate surfaces which match the demands set by clinical experience. One important characteristic of the surfaces discussed here is that they involve overhanging features which are suitable for trapping red blood cells and which cannot be created by mechanical or chemical roughening techniques.

Place, publisher, year, edition, pages
Melville, NY: American Institute of Physics (AIP), 2018. Vol. 30, no 4, article id 042009
Keywords [en]
Medical implants, dental implants, osseointegration, titanium, laser surface structuring, high speed imaging.
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-71704DOI: 10.2351/1.5078502ISI: 000451729800010Scopus ID: 2-s2.0-85056997363OAI: oai:DiVA.org:ltu-71704DiVA, id: diva2:1265096
Note

Validerad;2018;Nivå 2;2018-12-03 (inah)

Available from: 2018-11-22 Created: 2018-11-22 Last updated: 2019-06-03Bibliographically approved
In thesis
1. Analysis and Monitoring of Laser Welding and Surface Texturing
Open this publication in new window or tab >>Analysis and Monitoring of Laser Welding and Surface Texturing
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Analys och övervakning av lasersvetsning samt ytstrukturering
Abstract [en]

This thesis can be conveniently divided into three sections as follows;

Part I. Monitoring of laser welding 

In laser materials processing there has always been a need for suitable methods to supervise and monitor the processes on-line, to ensure correct production quality or to trigger alarms when failures are detected. Numerous investigations have been made in this field, including experimental and theoretical work. It is common practice in this field to monitor surface temperature, plasma radiation and back-reflected laser light, coaxially with the laser beam.  Traditionally, the monitoring systems involved carry out no statistical analysis of the signals received – they merely involve thresholds.

The first two papers in this thesis look at the feedback collected during laser welding using a co-axial setup from a Digital Signal Processing point of view and also uses high speed video photography to correlate signal perturbations with process anomalies. Digital signal processing techniques such as Kalman filtering, Principal Component Analysis and Cluster Analysis have been applied to on-line measurement data and have generated new ways to describe laser welding behaviour using parameters such as reflected pulse shape. The limitations of commercially available welding supervision systems have been studied and design suggestions for the next generation of on-line weld monitoring equipment have been formulated.

Having progressed from thin section welding with continuous wave lasers to pulsed laser welding, the thesis then moves on to pulsed laser surface melting.

Part II Analysis of surface texturing of titanium.

The second part of the thesis concentrates on laser structuring of titanium surfaces for medical implants. The two papers in this section present an analysis of the laser-material interactions which create surfaces suitable for osseointegration (bone attachment). The work concentrates on a commercially available surface used for screw implants in dentistry; BioHelix™. This surface is generated by an intense bombardment of laser pulses and the surface is thus disrupted during solidification. The formation of various levels and types of roughness are analysed and it is noted that laser generated rough surfaces are fundamentally different from those with a mechanically produced roughness. One key point is that laser generated rough surfaces can include overhanging features. This finding lead to the research carried out in part III of the thesis.

Part III. Analysis and classification of laser generated surfaces.

The final section of the thesis presents research which uses statistical techniques to identify whether or not a roughened surface includes overhanging features. The presence or otherwise of such features is important because they can affect the wettability of surfaces and thus their suitability for implant surfaces, adhesive bonding and lubrication etc. Micro Computer Tomography was used to generate a typical cross section of the surface under investigation. At equally spaced positions the profile of this cross section is then allocated vectors which are normal to the profile at each point. The angles of the vectors can then be analyzed to reveal the presence or otherwise of overhanging features. The presence of overhangs on the material surface is indicated by the existence of normal vectors with angles that exceed 180°. The papers in this section also investigate possibilities and limitations of using statistical methods in conjunction with Micro Computer Tomography.

The papers have in common processing of data for laser materials processing, by advanced methods to identify and extract essential information from the processes and the resulting material properties.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2019
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Laser welding, monitoring, Signal processing, laser texturing, texture analysis
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-74145 (URN)978-91-7790-404-5 (ISBN)978-91-7790-405-2 (ISBN)
Public defence
2019-10-15, E632 - Studion, Luleå tekniska universitet, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2019-06-04 Created: 2019-06-03 Last updated: 2019-09-18Bibliographically approved

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Olsson, RickardPowell, JohnFrostevarg, JanKaplan, Alexander

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