Light transmission through fiber post: the effect on adhesion, elastic modulus and hardness of dual-cure resin cement

OBJECTIVES: The aim of this study was to investigate the effect of fiber post light transmitting ability to the continuity of resin cement-root dentin (C-RD) and resin cement-fiber post (C-FP) interface, elastic modulus and hardness of a dual-cure resin cement. METHODS: Spectrophotometric measurements were applied for the determination of light transmission at coronal, middle and apical level as well as at the apical tip through Tech 21 X-OP (TECH) and DT Light Post (DT). Posts were cemented using dual-cured resin cement (Calibra). Roots were sectioned longitudinally through the post. Epoxy resin replicas were made and used to evaluate C-RD and C-FP interface under SEM. Modulus of elasticity (E) and Vicker's hardness (VH) of the cement layer were assessed. RESULTS: No light transmission was detected through TECH. Light transmission through DT decreased from coronal to apical and rose at the apical tip. TECH presented a significantly lower percentage of continuous C-RD and C-FP interface in comparison to DT. Coronal third of C-RD interface in TECH specimens had a significantly higher percentage of continuity than apical third. No regional differences in continuity of C-RD interface were found in DT specimens. E and VH were significantly lower when TECH was used, and decreased from coronal to apical for both posts. SIGNIFICANCE: Cementation of fiber post with no light transmitting ability using a dual-cured resin cement resulted in lower E and VH of the cement layer, and lower percentage of continuous C-RD and C-FP interface in comparison to cementation of light transmitting fiber post.