Ablation Depth and Surface Morphology of Dentin After Irradiation with a Tunable TEA-CO ₂ Laser in the Wavelength Range of 9.3 – 10.6 µm

Introduction: This study evaluated morphological and structural changes in extracted human dentin following irradiation with a pulsed tunable TEA-CO2 laser (9–11 μm) using scanning electron microscopy (SEM). The ablation rate was quantitatively determined at different wavelengths and pulse numbers while assessing preservation of dentinal tubules. Methods: Nearly flat dentin specimens were irradiated at four wavelengths (9.3, 9.6, 10.3, and 10.6 μm) with a constant energy density of 7.36 J/cm², pulse width of 200 ns, and repetition rate of 1 Hz. Samples were grouped by cooling method (air or water) and exposed to 1, 5, 10, 20, or 30 pulses. Surface morphology was examined by optical microscopy and SEM. Single-pulse ablation depth and ablation rate (μm/pulse) were measured using a profilometer under sub-threshold thermal damage conditions. Dentinal tubule occlusion after single-shot irradiation was compared with untreated dentin controls. Results: Air-cooled samples exhibited thermal damage, including carbonization and cracking. SEM analysis showed that water cooling led to greater thermal damage at high pulse numbers, particularly at wavelengths near 9 μm, corresponding to strong hydroxyapatite absorption and a lower ablation threshold. Up to 10 pulses, no cracks or peripheral thermal damage were observed at any wavelength. For single-pulse irradiation, the greatest ablation depth occurred at 10.3 μm with complete tubule occlusion, followed by 9.6 μm. At five pulses, maximum ablation depth was again observed at 10.3 μm (complete occlusion) and 9.3 μm (partial occlusion). Conclusion: These findings indicate that appropriate selection of wavelength, pulse number, and cooling method enables controlled dentin removal using a pulsed TEA-CO2 laser without peripheral tissue damage. Wavelength-dependent absorption and cooling conditions are critical for optimizing ablation efficiency while preserving dentinal tubule integrity.