Thermal analysis of laser densification of a dental porcelain powder bed has been investigated using a three-dimensional thermal finite element model, which encompasses (i) the incoming laser beam power with a Gaussian distribution, (ii) optical pyrometer simulation in addition to the closed-loop temperature control, (iii) powder-to-solid transition, (iv) temperature-dependent thermal convection, and (v) temperature and porosity-dependent thermal conduction and radiation. The simulation results are compared with the experiments. It is found that the predicted temperature distribution in the porcelain body matches the experiments very well. Further, the maximum discrepancy between experimental and simulated pyrometer temperatures is less than 8 percent. The simulation predicts that in order to achieve the desired microstructure of a dense dental porcelain body, the maximum local temperature during laser densification should be below 1573 K or the nominal surface temperature should be below 1273 K. Otherwise, the undesired microstructure (i.e., a leucite-free glass phase) forms.
Issue Section:
Thermal Systems
Keywords:
porcelain,
powders,
thermal analysis,
densification,
laser beam effects,
finite element analysis,
Gaussian distribution,
pyrometers,
closed loop systems,
heat conduction,
heat radiation,
temperature distribution,
natural convection,
glass structure,
biomedical materials,
dentistry,
thermal conductivity,
Dental Restoration,
Laser Processing,
Finite Element Modeling,
Thermal Analyes,
Powder Melting and Solidification
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