LASER ACOUSTIC-EMISSION THERMAL TECHNIQUE (LAETT) - A TECHNIQUE FOR GENERATING ACOUSTIC-EMISSION IN DENTAL COMPOSITES

Objectives. This study was designed to investigate a new method for ge nerating interfacial debonding between the resin matrix and filler par ticles of dental composites. Methods. A pilot study was conducted to e valuate laser-induced acoustic emission in dental resins filled with v arying quantities of particles. Model systems of 50/50 BisGMA/TEGDMA r esin reinforced with 0, 25, and 75 wt% 5-10 mu m silanated BaSiO6 were analyzed. The sample size was 3.5 mm diameter x 0.25-0.28 mm thick. A continuous wave CO2 laser (Synrad Infrared Gas Laser Model 48-1) was used to heat the composite samples. Acoustic events were detected, rec orded, and processed by a model 4610 Smart Acoustic Monitor (SAM) with a 1220A preamp (Physical Acoustic Corp.) as a function of laser power . Results. Initially, the acoustic signal from the model composites pr oduced a burst pattern characteristic of fracturing, about 3.7 watts l aser power. Acoustic emission increased with laser power up to about 6 watts. At laser powers above 6 watts, the acoustic emission remained constant. The amount of acoustic emission followed the trend: unfilled resin > composite with 25 wt% BaSiO6 > composite with 75 wt% BaSiO6. Significance. Acoustic emission generated by laser thermal heating Is dependent on the weight percent of filler particles in the composite a nd the amount of laser power. For this reason, laser thermal acoustic emission might be useful as a nondestructive form of analysis of denta l composites.