Twenty-eight human extracted premolars were randomly divided into the guide and microscope groups. After root canal treatment and fiber post restoration, the fiber posts were removed by using a digital guide and via microscope-assisted ultrasonic instrument, respectively. Mimics 10.0 was used to measure the deviation, and the accuracy of the two fiber post removal systems were compared.

In the guide group, the apical vertical deviation was 0.99 mm±0.52 mm, the apical horizontal deviation was 0.75 mm±0.19 mm, the angle deviation was 2.32°±0.64°, and the volume loss was 8.09 mm³±1.42 mm³. In the microscope group, the apical vertical deviation was 0.44 mm±0.23 mm, the apical horizontal deviation was 0.23 mm±0.07 mm, the angle deviation was 0.64°±0.31°, and the volume loss was 15.25 mm³±3.94 mm³. No significant difference was found in the apical vertical deviation between the two groups (P>0.05), whereas the apical horizontal deviation, the angle deviation, and the volume loss were significantly different between the two groups (P<0.05).

The removal of fiber post supported by a digital guide helped reduce the volume loss of post-core restoration teeth, but its accuracy was lower than that of removal by using a microscope-assisted ultrasonic instrument.