Abstract
Direct laser sintering on hard tissues is likely to open new pathways for personalised medicine. To minimise irradiation damage of the surrounding soft tissues, lasers operating at wavelengths that are ‘safe’ for the tissues and biomaterials with improved optical properties are required. In this work laser sintering is demonstrated with the use of an ultrafast, femtosecond (100fs) pulsed laser operating at a wavelength of 1045nm and two existing calcium phosphate minerals (brushite and hydroxyapatite) which have been improved after doping with iron (10mol%). Femtosecond laser irradiation caused transformation of the Fe3+-doped brushite and Fe3+-doped HAp samples into β-calcium pyrophosphate and calcium-iron-phosphate, respectively, with simultaneous evidence for microstructural sintering and densification. After estimating the temperature profile at the surface of the samples we suggest that soft tissues over 500μm from the irradiated zone would be safe from thermal damage. This novel laser processing provides a means to control the phase constitution and the morphology of the finished surfaces. The porous structure of β-pyrophosphate might be suitable for applications in bone regeneration by supporting osteogenic cell activity while, the densified Fe3+-rich calcium-iron-phosphate may be promising for applications like dental enamel restoration.
Highlights
Personalised or precision medicine and near patient manufacturing are emerging concepts which may influence and define the treatment pathway for certain diseases; e.g. in dentistry and regenerative tissue engineering
In the present work we investigated the laser sintering of calcium phosphate biomaterials with the use of a femtosecond pulsed laser operating at 1045 nm
Undoped HAP crystals remained largely unchanged or unreacted after laser irradiation, whereas, undoped brushite transformed into pyrophosphate without any indications of crystal growth or densification
Summary
Personalised or precision medicine and near patient manufacturing are emerging concepts which may influence and define the treatment pathway for certain diseases; e.g. in dentistry and regenerative tissue engineering. The most efficient way, to date, to achieve this is through Rapid Prototyping (RP) technologies with Selective Laser Sintering (SLS) being one of the most developed and successfully applied methodologies [2]. Anastasiou et al / Materials and Design 101 (2016) 346–354 at visible and infrared regions of the spectrum Taking all these factors into account, we suggest that optimisation for direct sintering on hard tissue would require a short pulsed laser, emitting at wavelengths between the visible and near infrared, where the absorption properties of melanin (N700 nm) and haemoglobin (N600 nm) are neglected and where water's absorption coefficient is still low [4]
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