In vitro study on selective removal of bovine demineralized dentin using nanosecond pulsed laser at wavelengths around 5.8 μm for realizing less invasive treatment of dental caries

In the treatment of dental caries, less invasive methods are strongly required. However, conventional dental lasers cannot always achieve selective removal of caries or good bonding with a composite resin. Based on the optical absorption characteristics of dentin, wavelengths around 6 μm are promising in this regard. Our previous study indicated the possibility of selective removal of demineralized dentin using a nanosecond pulsed laser at wavelengths around 6 μm. In the present study, the optimal laser irradiation conditions were investigated for achieving selective removal of demineralized dentin. Bovine dentin was used, and its laser ablation characteristics were evaluated. The results indicated that demineralized dentin could be selectively removed, without causing cracking or damage to sound dentin, at laser wavelengths of 5.75 and 5.80 μm and average power densities of 30–40 W/cm². These optimal laser irradiation conditions also realized higher bonding strength with a composite resin than was possible using an Er:YAG laser. The use of nanosecond pulses allowed the thermal confinement condition to be satisfied, leading to a reduction in tissue damage, including degradation of dental pulp vitality. Thus, a nanosecond pulsed laser at 5.8 μm was found to be effective for less invasive caries treatment.