Comparative evaluation of smear layer removal from the root surface following the use of CO2 and Er:YAG lasers for root conditioning using scanning electron microscopy

Root surface preparation refers to removal of the smear layer from the root surface. The aim of this study was to compare the amount of smear layer removal from the root surfaces following root planing alone and the use of CO2 and Er:YAG lasers using scanning electron microscopy
In this experimental in vitro study, 18 root segments from periodontally involved teeth were prepared and distributed into 3 groups (n=6): group A: treated with Er:YAG laser (2.94 micron,120 mj with water and air, 15 seconds, 20 Hz, 7-8 mm from the surface of segment, perpendicular to the root surface); group B: treated whit CO2 laser (10.6 micron, 3 W, 4 seconds, 5 cm from the surface, perpendicular to the surface); group C or control (scaling and root planing with a curette only). The specimens were evaluated under a scanning electron microscope to determine the amount of smear level removed (SLR) and micrographs were taken. Data were analyzed using Mann-Whitney and Kruskal-Wallis tests (α=0.05).
The results showed significant differences in SLR between the three groups, with significantly greater SLR in both Er:YAG (p value = 0.002) and CO2 (p value = 0.026) laser groups compared to the control group. However, there was no significant differences between the two laser groups (p value = 0.937). In the Er:YAG laser group, the smear layer was removed completely, resulting in an irregular surface with partially open tubules. In the CO2 laser group, too, the smear layer was removed completely, resulting in partially open dentinal tubules but the surface in this group was smooth. In the control group, smear layer persisted and some dentinal tubules were opened.
It seems application of both CO2 and Er:YAG laser to root surfaces removes the smear layer and partially opens the dentinal tubules.