Two Adhesives Layering Strategy For Root Canal Post Bonding

This study aims to evaluate the effect of combining light-cure and chemical-cure adhesives on the bond strength of root canal posts at different depths of the post space Thirty-six single-rooted human premolars were used for the micro-tensile bond strength (µTBS) test. The teeth were decoronated at the cementoenamel junction, and the pulpal tissue was removed. Post spaces were prepared using FiberKor drills to a depth of 10 mm and a diameter of 1.5 mm. After preparation, root canals were rinsed with 5.25% NaOCl, followed by 17% EDTA, and divided into three groups based on the adhesive application method: Universal Bond Quick (UBQ; Kuraray, Tokyo, Japan), Bondmer Lightless II (BL2; Tokuyama Dental, Ibaraki, Japan ), or a combination (UBQ + BL2). All post spaces were filled with dual-cure resin cement. After 24-hour storage, specimens were sectioned into nine beams (subdivided into coronal, middle, and apical regions), followed by µTBS testing. Data were analyzed using two-way ANOVA and Tukey’s HSD test (α = 0.05). Fracture modes were examined using SEM. Two-way ANOVA revealed a significant interaction between the adhesive type and root region (p < 0.05). UBQ + BL2 exhibited the highest bond strength (p < 0.05). The coronal region had significantly higher bond strength than the middle and apical regions (p < 0.05). These findings suggest that the new strategy of combining two adhesives enhances bond strength in root canal post spaces, particularly in deeper regions where light penetration is limited.