Application of 3D-Printed Resin Guides for the Removal of Molar Fiber Posts

Objective To evaluate the digital guide technique for removing fiber posts from molars and compare it with the conventional microscope-assisted ultrasound method. Methods Two mandibular dentition models, each comprising six extracted molars, were prepared. Two thick and straight canals distributed separately in the distal and mesial roots of each molar were selected for placing the fiber posts. The 24 posts in the two dentition models were removed using 3D-printed resin guides, or a microscope and an ultrasonic device. The time taken to remove the fiber post from each tooth was recorded. The volume loss, deviation values (angular deviation and horizontal and vertical deviations of the tip), and formation of microcracks before and after fiber post removal were determined using micro-computed tomography images. Results The digital guide technique took significantly less time than the microscope-assisted ultrasound technique (p < 0.05). No significant differences in horizontal and vertical tip deviations were observed between the two groups. The angular deviation and volume loss in the guide group were significantly lower than those in the ultrasound group (p < 0.05). New dentin microcracks were formed in the ultrasound group but not in the digital guide group. Conclusion Using a 3D-printed resin guide plate can shorten the fiber post removal time and improve the stability and safety compared to the microscope-assisted ultrasound technique. Clinical significance 3D-printed resin guides can reduce the fiber post removal time and provide better stability and safety than the conventional method.