The aim was to investigate the effect of the Er-YAG laser radiation on morphology and chemical
composition of enamel, dentin, and bone. The specimens of the three groups were irradiated with a very long pulse mode (VLP) of 2.94 mm Er-YAG laser with 100 mJ pulse energy and energy density of 8.42 J/cm2 for 30 s, at a repetition rate of 15 Hz. The organic and inorganic content of the samples were investigated by Fourier Transforms Infrared spectroscopy (FTIR). The morphological characteristics were investigated with scanning electron microscopy (SEM) and elemental analysis (calcium and phosphorus) with energy-dispersive X-ray spectroscopy (EDX). FTIR data were analysed with a One-Way ANCOVA test and EDX data with the independent sample t-test. Following the laser radiation, FTIR showed a significant decrease in the organic content of all tissues. The weight percentage (wt %) calcium content of dentin and bone increased significantly following irradiation with a p-value of .002 for both tissues, but the wt % of phosphorus content was not influenced significantly. The morphological alterations expressed signs of fusion in all the samples.