Dental lasers are frequently described as a single technology. They are better understood as several distinct instruments, separated by wavelength and by what that wavelength is absorbed by.
Absorption determines the effect
Laser light produces its effect when it is absorbed and converted to heat. Light that passes through tissue without absorption does nothing at all.
Every wavelength is absorbed differently by water, by haemoglobin and pigment, and by the mineral content of hard tissue.
Matching wavelength to the target is therefore the whole design problem, and it is why one device cannot serve every purpose. Practices with lasers often have more than one for this reason.
Soft tissue lasers target pigment and haemoglobin
Diode wavelengths are absorbed strongly by pigment and blood and poorly by water and mineral, which makes them suited to gum tissue.
Because absorption in blood is high, cutting is accompanied by sealing of small vessels, which is why soft tissue procedures with these devices bleed little.
Poor absorption by mineral means the same device cannot cut enamel, and using it near hard tissue risks heating rather than cutting.
Hard tissue lasers target water in the mineral
Erbium wavelengths are absorbed very strongly by water, and enamel and dentine both contain water within their mineral structure.
Rapid heating of that water causes microscopic expansion that breaks the mineral apart, so tissue is removed by micro-explosion rather than by melting.
Water spray during use both cools the site and supplies the absorbing medium, which is why these procedures are not dry.
Heat control is the limiting factor
The pulp tolerates only a modest temperature rise before sustaining damage, and bone is similarly sensitive.
Devices deliver energy in pulses with intervals for cooling, keeping average temperature within safe limits while peak power stays high enough to work.
Settings therefore relate to the tissue and the procedure rather than being a general power level, and eye protection is required for everyone present.
Where lasers do and do not replace conventional methods
Soft tissue contouring, certain periodontal procedures and some surgical exposures are areas where these devices are established.
Cutting large volumes of enamel is slower than with a conventional handpiece, so lasers tend to be used for selected cases rather than routine restorative work.
Whether a laser is appropriate for a given procedure is a clinical judgement, and the presence of the technology says nothing about whether treatment is needed.