Photodynamic therapy and calcium hydroxide modulate intraradicular dentin mechanical properties and glass-fiber posts bonding interface using distinct photosensitizers across root thirds

Purpose : This study evaluated the influence of photodynamic therapy (PDT) performed with different photosensitizers (PSs), indocyanine green (ICG), curcumin (CUR), and methylene blue (MB), associated or not with calcium hydroxide as intracanal medication (ICM), on the mechanical properties of intraradicular dentin, degree of conversion (DC), and the integrity (voids and bubbles) of the adhesive interface of glass-fiber posts (GFPs). Materials and Methods : 112 bovine incisors were allocated into eight groups (n=14) according to the use of PDT, ICM and PSs, including a negative (no PDT/no ICM) and positive (no PDT/with ICM) control groups. After 14 days, ICM was removed, root canals were obturated, and GFPs were cemented. Hardness, elastic modulus, adhesive integrity, and resin cement DC were evaluated in three root thirds (cervical, middle, and apical). Results : Adhesive integrity analysis revealed a higher incidence of voids in PDT-only groups, whereas the association with ICM reduced void formation in the ICG and MB groups. DC was consistently higher in the cervical third, unrelatedly of the protocol adopted. PDT with CUR without ICM resulted in the highest dentin hardness in the apical third. ICM increased elastic modulus in the middle third of the CUR group but reduced it in the positive control group. Hardness was generally higher in the cervical and apical thirds and became more homogeneous following ICM application. Conclusions : MB-mediated PDT associated with ICM proved to be a suitable protocol yielding favorable mechanical behavior of intraradicular dentin and satisfactory adhesive interface integrity of GFPs across all root thirds.