Femtosecond Laser Modification of Fe3+ doped Calcium Phosphates

Calcium phosphate based biominerals are the main inorganic constituent of bone and teeth. Therefore, the processing of these minerals provides a unique solution for a bioactive, structural material which can be used inside the body instead of typical bioinert materials. Dental enamel, a highly crystalline calcium phosphate, is prone to acid erosion and wear, which affects all ages, an early sign of which is hypersensitivity. Calcium phosphate minerals also play an important role in bone restoration and growth, and with an increased ageing population the number of hip and knee replacement revision surgeries are becoming more common. In this study, the main objective was to investigate the use of femtosecond pulsed lasers for sintering and processing of modified calcium phosphate minerals in order to analyse the efficacy of these methods for interfacial bonding and adhesion to titanium implant materials and dental enamel.
Calcium phosphate minerals, specifically hydroxyapatite (Ca10(PO4)6OH2), were synthesised through the wet chemistry synthesis method, and were modified with the substitution of Fe3+ ions in various doping regimes. These materials were characterised via XRD, SEM, FTIR, Raman spectroscopy, UV-vis-NIR spectroscopy, particle size analysis and TGA/DSC.
The following materials where then irradiated with near infrared sources in a variety of pulse repetition rates ranging from single shot to 1GHz. Ablation thresholds of the materials were found to remain relatively constant despite the addition of Fe3+ impurities into the structure. And working in lower repetition rate regimes, did not allow for successful sintering of the materials, however, it could be bonded to the titanium substrates relatively in this regime. Higher repetition rates regimes allowed for reasonable heat accumulation in the material which then generated more successful sintering and bonding onto dental enamel surfaces.