root canals • Argon laser Resin curing Tooth bleaching Treatment of ulcers Aesthetic
gingival contouring Fraenectomy and gingivectomy
Lasers produce light energy within a narrow frequency range. They are named after
the active element within them, which determines the wavelength of the light emitted.
So some of the commoner lasers have the following characteristics
- Neodymium : yttrium-aluminium-garnet (Nd : YAG) wavelength = 1.064um
- Carbon dioxide lasers wavelength = 10.6um
- Erbium : YAG = 2.94um
- Argon = 457-502 nm
- Gallium-Arsenide (diode) = 904 nm
- Holmium : YAG = 2.1um
The wavelength of light is the primary determinant of the degree to which the target
material absorbs light. The deeper the laser energy penetrates, the more it scatters and
distributes throughout the tissue, for example, carbon dioxide laser penetrates 0.01-
0.03 mm into the tissue while Nd : YAG laser penetrates 2-5 mm. The light from
dental lasers is absorbed and converted to heat, while the thermal effects caused
depend on the tissue composition and the time the beam is focused on the target
tissue. The increase in temperature may cause the tissue to change in structure and
composition, for example, denaturation, vapourization, carbonization, and melting
followed by recrystallization. The argon laser has a major advantage over the other
lasers in that the wavelength at which it operates is absorbed by haemoglobin and
therefore provides excellent haemostasis.
Let us look first at safety. In order for a procedure to be deemed safe, collateral
damage must be within acceptable limits, that is, the risk-benefit ratio must be small
with the benefit to the patient being significant; for example, laser-induced tissue
trauma to the surgical site can add several more days to the healing process and cause
dramatically abnormal appearances for up to 10-14 days postoperatively. Balanced
against this, postoperative pain is usually minimal.
Using an Er : YAG laser for cavity preparation and caries removal
Proposed advantages:
- Laser use results in clean sharp margins in enamel and dentine.
- The pulp is protected and safe as the depth of energy penetration is negligible.
(There is one study that shows deeper damage to nerve terminals and fibres visible
under electron microscope examination though its clinical significance is unknown.) - Patients report little or no pain with the use of Er : YAG laser in cavity preparation.
- Time taken for cavity preparation is short.
Disadvantages:
- Cost.
- The need to learn a new technique in which there is no proprioceptive feedback
since the laser tip does not impinge dental tissue.