Measurement of pulse Nd: YAG laser-induced stress and analysis of dental tissue and amalgam plume using uniaxial polyvinylidene fluoride-based photoacoustic sensor and plasma spectroscopy

Abstract A combined technique of photoacoustic sensor and laser-induced plasma spectroscopy is used to investigate the interaction of pulse Nd: YAG laser with healthy, carious dental tissue and amalgam. The results showed that applied force hence the corresponding pressure increases with laser fluence. At low fluences below the threshold ≈20 Jcm−2, a bipolar thermoelastic signal was observed where gradually the amplitude of the compression part increased at higher values. A non-linear behaviour was observed at about threshold. The maximum pressure of ≈8 kPa was measured for healthy tissues. While the transmitted acoustic energy was increased with laser fluence, the corresponding ratio of acoustic to optical energy was decreased. The line emissions distinctly indicated both the matrix and non-matrix elements in healthy, carious and amalgam samples. The temperature of the majority of elements varied between 590 and 15000 K corresponding to tin and silver as lowest and highest respectively except for carbon at ≈4200 K. The high temperature vaporized products can raise some health issues, particularly to the patient if a large amount is inhaled.