Effects of Isopropyl Alcohol, Tetrahydrofuran, Pyridine, and Acetonitrile on Surface Roughness, Surface Morphology, and Shear Bond Strength Between Composite Resin and Different Provisional Restorative Materials

Background/Objectives: Provisional restorations are essential in prosthodontic treatment, and reliable intraoral repair is clinically important during extended interim use. This in vitro study evaluated the effects of organic solvent pretreatment on surface characteristics and shear bond strength (SBS) of CAD/CAM provisional restorative materials fabricated by milling, stereolithography (SLA), and digital light processing (DLP). Methods: Three materials were assigned to five surface treatment conditions: no solvent (control), isopropyl alcohol (IPA), tetrahydrofuran (THF), acetonitrile (ACN), and pyridine (PYR). After pretreatment, separate specimens were used for surface analysis and SBS testing. Surface roughness was measured by atomic force microscopy using arithmetic mean height (Sa) and root mean square height (Sq), and surface morphology was examined by scanning electron microscopy (SEM). For SBS testing, specimens were repaired using a universal adhesive and a flowable resin composite, followed by failure mode analysis. Data were analyzed using two-way ANOVA and Tukey’s post hoc test (α = 0.05). Results: Material type, solvent treatment, and their interaction significantly affected SBS, Sa, and Sq. The DLP material showed the highest SBS overall, with no significant differences among treatments. In the SLA material, ACN resulted in the lowest SBS, whereas PYR showed the highest mean value. In the milled material, THF, ACN, and PYR produced significantly higher SBS than the control and IPA groups. Conclusions: Within the limitations of this study, the effect of organic solvent pretreatment on repair performance was substrate-dependent.