SEM analysis of enamel surface treated by Er:YAG laser: Influence of irradiation distance

Abstract

Er:YAG laser in defocused mode promoted slight morphological alterations and seems more suitable for enamel conditioning than focused irradiation. The application of phosphoric acid on lased-enamel surface, regardless of the irradiation distance, decreased the superficial irregularities.

Morphological and Structural Changes on Human Dental Enamel After Er:YAG Laser Irradiation: AFM, SEM, and EDS Evaluation

“…It has been reported [4][5][6][7][8][9][10][11][12][13][14] that Er:YAG laser irradiation induces morphological changes in the enamel that include the formation of rough surfaces, cracks, and craters, which seem to be more prone to bacterial accumulation. Such morphological changes create favorable conditions for the development of carious lesions.…”

“…During irradiation, the laser's energy is absorbed selectively by water molecules and hydrous organic components of the biological tissues, which causes the evaporation of water and organic components, resulting in thermal effects caused by the heat generated by this process (called ''photothermal evaporation''). Moreover, in hard-tissue procedures, the water vapor production induces an increase of the internal pressure within the tissue, resulting in an explosive expansion called a ''microexplosion'' 2,3 that produces changes in the morphology of the enamel, [4][5][6][7][8] including undesirable effects that have been described as craters and cracks. [9][10][11][12][13][14] Furthermore, the results in the available literature regarding subablative Er:YAG laser irradiation as a method to increase enamel acid resistance for caries prevention have been contradictory.…”

“…Furthermore, all of the irradiated samples displayed rough areas, craters, and cracks, consistent with the results of previous studies. [4][5][6][7][8][9] The use of SEM has provided relevant findings for the study of enamel morphological changes after laser irradiation. However, the addition of EDS as an analytical technique provides valuable information about the chemical changes on the irradiated enamel surface.…”

Bond Durability of Er:YAG Laser-Prepared Primary Tooth Enamel

“…This is despite the action of acid etching that dissolves the hydroxyapatite (23), which may leave the adhesive interface vulnerable to hydrolytic degradation (10). In addition, chemical reactions have been responsible for the degradation of resin-enamel bonds over time and, consequently, a decrease in bond strength, including a loss of stability in the adhesive systems (10) and the extraction of resin-material from the hybrid layer (24).…”

“…This is likely because the laser-treated surface presents a surface microroughness with an irregular topography with extensive fused areas that could reduce enamel solubility (25). Phosphoric acid application after Er:YAG laser irradiation reduces superficial irregularities, creating a more homogeneous pattern (24), which could explain why some authors suggest their combination for increasing adhesion when treating primary teeth enamel (25).…”