Effects of Immediate Dentin Sealing and Er:YAG Laser Immediate Treatment on the Micro-Tensile Strength of Dental Fluorosis

Abstract Aim: This study investigated the effects of immediate dentin sealing (IDS) and Er:YAG laser treatment on the micro-tensile strength (μTBS) of dentin affected by varying degrees of dental fluorosis. Materials and Methods: Seventy-two extracted human molars were classified by the Thylstrup–Fejerskov index into normal (TFI 0), mild (TFI 1–3), moderate (TFI 4–5), and severe fluorosis (TFI 6–9) groups ( n = 18 each). Each group was further divided into three treatment subgroups: control (saline), IDS (Adper™ Single Bond 2), and Er:YAG laser-treated dentin. Composite resin blocks were bonded using dual-cure resin cement (RelyX™ U200), followed by thermal aging. μTBS was tested, and failure modes were analyzed via stereomicroscopy. Dentin ultrastructure was examined using scanning electron microscopy (SEM). Two-way ANOVA and Tukey’s test were used for statistical analyses ( α = 0.05). Results: IDS significantly enhanced μTBS across all fluorosis severities compared to Er:YAG laser and control groups ( P < 0.05). A significant interaction between fluorosis severity and treatment type was observed (F = 2.96, P < 0.05). IDS-treated normal dentin showed the highest μTBS (19.92 ± 2.60 MPa), while dentin with severe fluorosis treated with Er:YAG laser yielded the lowest (7.60 ± 0.65 MPa). SEM revealed reduced tubule openness and resin tag infiltration in fluorosed dentin, particularly in severe cases. Failure mode shifted from mixed/cohesive to adhesive with increasing fluorosis severity. Conclusion: IDS demonstrated superior bonding performance over Er:YAG laser treatment in managing fluorosed dentin, with the effectiveness diminishing with an increase in fluorosis severity. These findings support the clinical use of IDS in adhesive restorations involving fluorosed teeth, particularly when structural integrity is compromised.