THERMAL PARAMETERS OF DENTAL MATERIALS DETERMINED BY PHOTOACOUSTIC PHASE-LAG MEASUREMENTS

A method of measuring the phase lag of the photoacoustic signal obtain ed by rear surface excitation is employed for the determination of the thermal properties of insulating dental materials such as calcium hyd roxide cement, a cavitary varnish and photopolymerized restoration res ins. Disk shaped dental materials were glued to the front surface of t he thin metal foil window of the photoacoustic cell and illuminated by pulsed light. A three layer model was developed to fit the measuremen ts of the phase angle as a function of the frequency of excitation. Th e thermal diffusivity and conductivity of the dental material were det ermined to good precision. The instrumentation employed in the present work is simple and easily obtainable by any laboratory. (C) 1998 Amer ican Institute of Physics. [S0034-6748(95)01109-5]