Effect of Different Specimen Preparation Methods on Dentin Shear Bond Strength: Polyethylene Tubes vs Jig System

This study evaluated the influence of different specimen preparation methods on the shear bond strength (SBS) of a universal adhesive to dentin, with the aim of identifying a more standardized and reliable protocol for SBS testing.

Thirty-three extracted molars were used to obtain 66 dentin surfaces. After surface preparation with 600-grit silicon carbide paper, specimens were randomly assigned to three groups (n = 22) according to the specimen preparation technique: tube-removed (polyethylene tubes removed before testing), tube-retained (tubes left in place during testing), and jig-based (Ultradent jig system, South Jordan, UT, USA). SBS testing was performed using a universal testing machine at 1 mm/min. Failure modes were analyzed under a stereomicroscope and representative specimens were examined by scanning electron microscopy (SEM). Data were analyzed using one-way ANOVA and Tamhane's T2 post-hoc test (α = 0.05).

Significant differences were found among the groups (P 0.001). The highest mean SBS values were obtained in the jig-based group, followed by the tube-removed and tube-retained groups. Adhesive failure was predominant across all groups, with 100% adhesive failures observed in the jig-based group. SEM analysis revealed a more clearly delineated bonding interface in the jig-based group, while tube-based groups exhibited minor polyethylene residues.

These findings indicate that the specimen preparation method plays a critical role in the reliability and interpretation of SBS testing outcomes. The jig-based approach may provide more consistent and reproducible SBS results compared to tube-based methods, highlighting the importance of standardized specimen fabrication in adhesive dentistry research.