Effect of ultraviolet light irradiation on bond strength of fiber post: Evaluation of surface characteristic and bonded area of fiber post with resin cement

OBJECTIVE Fiber post is cemented to a root canal to restore coronal tooth structure. This research aims to evaluate the effect of ultraviolet (UV) irradiation on bond strength of fiber post with resin cement. MATERIALS AND METHODS A total of 40 of the two types of fiber posts, namely, FRC Prostec (FRC) and Fiber KOR (KOR), were used for the experiment. UV irradiation was applied on top of the fiber post surface for 0, 15, 20, and 30 min. The irradiated surface of the fiber posts (n = 5) were immediately bonded with resin cement (Rely X U200) after UV irradiation. Shear bond strength (SBS) MPa was measured, and the dislodged area of post surfaces was examined with scanning electron microscopes. Changes in surface roughness (Ra) of the FRC group after UV irradiation were observed (n = 3) using atomic force microscopy. Data of SBS were statistically analyzed using one-way analysis of variance, followed by multiple comparisons (P < 0.05). RESULTS SBS was significantly higher for 20 min of UV irradiation of the FRC group while significantly higher SBS was observed with 15 min of UV irradiation of the KOR group. Resin cement was more evident (cohesive failure) on the dislodged post surface of the UV treated groups compared with the control. The surface roughness of the FRC post was Ra = 175.1 nm and Ra = 929.2 nm for the control and the 20 min group, respectively. CONCLUSIONS Higher surface roughness of the UV irradiated group indicated formation of mechanical retention on the fiber post surface. Evidence of cohesive failure was observed which indicated higher SBS of fiber post with the UV irradiated group.