To compare and evaluate microcracks and smear layer after root end preparation by laser, ultrasonic tip, and conventional bur in single-rooted teeth: "Scanning electron microscope study".

Aim: Evaluation of root-end cavities for the existence of microcracks and smear layer with laser, ultrasonic tip by conventional bur, and control group in single-rooted tooth by scanning electron microscope (SEM).

Methodology: Fifty-two extracted fully developed single-rooted teeth were decoronated, cleaned, shaped, and obturated with F2 GP, and 3 mm roots were removed. Laser, ultrasonic tip (AS 3Dretro-tip on Newtron-SATELEC, Acteon), and conventional bur (size 010 round) were used to create root-end preparation. No root-end cavities were produced in the control group. SEM was used to check all samples for microcracks and smear layers.

Results: A significant difference was found between microcrack formation in laser and conventional bur preparation (P = 0.002), and ultrasonic and laser (P = 0.015). Nonsignificant difference was found between ultrasonic and conventional bur (P = 0.046). The study concluded that maximum cracks were seen in conventional bur formation at the apical end of the root (0.85 ± 0.36) followed by the ultrasonic method (0.54 ± 0.23).

Conclusion: Root-end cavities prepared with laser give fewer microcracks and less production of smear layer compared to the ultrasonic tip and conventional bur.