This paper provides an overview of the scientific principles of hard dental tissue laser procedures and discusses the influence of laser wavelength, pulse duration and pulse energy. Erbium lasers have been found to be a safe and efficient technological solution for the manipulation of hard dental tissues. The ability to precisely control laser pulse duration enables the practitioner to determine the nature of the ablation, which can range from cold to hot ablation. To work in a cold ablation regime laser pulse duration and pulse energy must be matched in order to create the right laser action. The latest generation Fidelis laser systems, manufactured by Fotona, feature an Er:YAG laser source that can deliver precisely controlled pulse durations, using Variable Square Pulse (VSP) Technology control. This enables a range of laser drilling techniques including very fine, precise “cold” ablation and MAX mode, enabling the fastest, most efficient hard tissue ablation available. These two new modes, SSP and MAX, mean that dental lasers have finally achieved their original goal; replacing mechanical drills with more precise and less-invasive optical technology, without sacrificing in safety, ease-of-use or operating speed.