The microstructure of MIH-affected enamel after irradiation with Er, Cr: YSGG laser – a qualitative in vitro study

The present in vitro study aimed at evaluating microstructure and surface roughness of sound and artificially demineralized teeth and teeth with Molar-Incisor Hypomineralization (MIH) after etching with a solid-state Er, Cr: YSGG laser.

Twenty-three recently extracted teeth (10 sound, 10 artificially demineralized and 3 MIH-affected) were irradiated (2.5 W, 50 Hz) for 40 s in one surface and etched with 35-37% phosphoric acid for 60 s in the opposite. Surface microstructure was evaluated under a Scanning Electron Microscope and surface roughness using optical profilometry. Differences in the etching pattern between and within the groups was tested using chi-square test and in surface roughness before and after treatment using paired Wilcoxon test.

Laser irradiation produced an irregular and roughened etching pattern with micro-cracks in areas, as compared to acid-etching that produced a more homogeneous surface. The laser-treated teeth presented various types of etching patterns, while etching pattern II was the most predominant for acid-etched teeth. In both groups MIH teeth presented mainly etching pattern III. Surface roughness was increased after etching, with the differences being significant for sound (p = 0.005) and artificially demineralized teeth (p = 0.005) but not for MIH-affected (p = 0.109). For sound and MIH-affected teeth, surface roughness was higher after laser-etching, as compared to acid-etching, while the opposite was the case for artificially demineralized teeth (p > 0.4).

Er, Cr: YSGG laser, despite producing a different etching patterns, resulted in comparable surface roughness to conventional acid etching. Pre-treatment may alter surface structure and have a substantial influence on the adhesion of porous hypomineralised enamel.