Purpose: The creation of a concrement-, plaque- and toxin-free root surface is a prerequisite for successful periodontal therapy. Since the most significant property of the laser is its bactericidal effect, the purpose of this study was to evaluate the effects of the Er:YAG laser irradiation on root surfaces in vitro and thus its usefulness as a periodontal instrument.
Materials and Methods: A pulsed Er:YAG laser with a handpiece developed especially for periodontal therapy was used. The study was organized into three sections: the first involved root surfaces of 20 extracted human teeth divided into 4 groups. In the first group, the teeth were irradiated at a setting of 100 mJ/15 pps for 5 x 5 s. The second group was subjected to manual scaling. The third received a combination of scaling and laser irradiation. The fourth group was the untreated control. After treatment, the root surfaces were examined with environmental SEM. In the second section of the study, the pulp-cavity temperature was taken in 10 teeth at different laser settings. In the third section, root surfaces and adjacent soft tissues of sheep mandibular teeth were irradiated at different laser settings in order to simulate in vivo treatment. For comparison, one group received manual scaling and another served as untreated control. After treatment, the samples were prepared for light microscopy.
Results: SEM revealed that the Er:YAG laser irradiation results in a significantly rougher surface structure than mechanical scaling alone or in combination with laser irradiation. It proved possible to remove concrements. Temperature measurements indicated that the temperature rise in the pulp cavity does not exceed 4.5°C at a laser setting of 100 mJ/15 pps for 5 x 5 s interspersed with 15-s breaks. Laser irradiation at a setting 100 mJ/15 pps was found to cause almost no damage to soft and hard tissues, while higher pulse energies resulted in roughness of the root surface and damage of the remaining periodontal structures.
Conclusion: The investigations of human teeth showed that it is possible to remove concrements by irradiation with the YAG laser at a setting of 100 mJ/15 pps. The root-surface roughness and overall removal of dental hard tissues were comparable to that obtained with mechanical scaling. The temperature measurements showed that Er:YAG laser irradiation of root surfaces under the given conditions did not provoke an intolerable temperature increase, provided that sufficient water cooling and interval time (at least 15 s) are assured. As shown on the sheep teeth, the damage to the adjacent bone and soft tissues is negligible. Thus, the Er:YAG laser seems to be a very promising tool for the removal of subgingival plaque and calculus.