Occlusion of dentinal tubules by photoactive sintering of calcium phosphate minerals doped with erbium, aluminium and fluoride compounds

Although the principles for the treatment of sensitive teeth are demonstrated successfully by many, the current treatments for tooth hypersensitivity are not effective in the long term or as a permanent solution. The purpose of this research project was to investigate the occlusion of dentinal tubules by calcium phosphate minerals doped with erbium, aluminium, and fluoride compounds under laser irradiation. The investigation included the synthesis and characterisation of calcium phosphate (CaP) powders, preparation of hypersensitive dentine sections, and coating of dentine sections with CaP powders followed by laser irradiation. CaP powders were synthesised by the chemical precipitation and hydrothermal methods. These powders were also chemically modified by the addition of different compounds (dopants) under various conditions to achieve substitutions for calcium, phosphate, and hydroxyl ions in the CaP structure. Dopants’ compounds included erbium compounds (erbium oxide and erbium nitrate) to produce photoactive CaP minerals, aluminium compounds (aluminium phosphate and aluminium nitrate) and fluoride compounds (calcium fluoride and ammonium fluoride) to produce CaP minerals with high mechanical, chemical, and thermal stability. As well as chemically modifying the structure of CaP, the size and shape of CaP particles were investigated by varying pH and temperature of the synthesis method. The chemically modified CaP minerals were applied onto hypersensitive dentine sections by the dip coating method and laser irradiated by CW and pulsed lasers to achieve a complete occlusion of open dentinal tubules. CaP powders in the form of pellets were also prepared for laser irradiation and acid erosion trials to determine their interaction with laser irradiation and solubility behaviour in an acid environment, respectively. CaP powders, CaP pellets, and laser irradiated – coated dentine sections were characterised using various analysis techniques, including SEM, SEM-EDX, static laser scattering, XRD, FTIR, DSC, ICP/MS, Micro – hardness, and Profile roughness.