Impact of magnification and fluorescence guidance on conservative retrieval of failed fiber posts: an in vitro study

Abstract Background Fiber post removal during endodontic retreatment is challenging since fiber posts bond strongly to root dentin, closely matching its color, making the post–cement–dentin interface difficult to distinguish. Consequently, fiber post retrieval may cause unnecessary dentin loss and leave residual material within the canal. There is limited information on whether different visual-guidance approaches influence tissue preservation during fiber post removal. This study aimed to evaluate the effects of different visual-guidance approaches (×2.5 surgical loupes, a dental operating microscope, and fluorescence-assisted magnification with ReVeal™) on tissue preservation and material-removal performance during fiber post removal. Methods Previously seated fiber posts were removed from 35 single-rooted extracted human teeth under a standardized ultrasonic protocol, varying only the imaging conditions: control/naked eye (K), ×2.5 loupes (L), ×6.9 dental operating microscope (M), and ×2.5 loupes with integrated 405 nm fluorescence (R) (ReVeal). Three-dimensional analyses were performed on pre- and postoperative micro-CT datasets. Volumetric dentin loss, residual resin cement in the post space, and remaining dentin thickness (RDT; mesial and distal measurements 1–6 mm from the post tip) were calculated. Two-way repeated-measures ANOVA with Greenhouse–Geisser correction, Welch tests, and Kruskal–Wallis tests were used; reliability was confirmed with the intraclass correlation coefficient. Results Post removal caused significant dentin loss in all groups ( p < 0.001). Magnification groups (L, M, R) showed lower RDT loss when compared to the control group while no significant difference was detected among L, M, and R groups ( p > 0.05). No significant difference was observed among the four groups in terms of residual material ( p = 0.056); in an exploratory pairwise comparison, fluorescence-assisted magnification was associated with significantly fewer remnants than the loupe group ( p < 0.05). RDT decreased at all levels, most markedly in the 2–4 mm band ( p < 0.001). Tooth-structure loss on the mesial surface exceeded that on the distal surface ( p < 0.001); this asymmetry was notably reduced in the microscope group ( p > 0.05). Conclusions Magnification (loupes/microscope) contributed to tissue preservation during fiber post removal, while the fluorescence-assisted approach was associated with lower residual resin cement, mainly relative to loupes. Microscope use facilitated more centered and symmetric tissue removal along the root-canal axis. As this was an in vitro study, these findings require confirmation in clinical settings.