Self-adhesive flowable resin composites (SAFRCs) offer simplified, single-step placement and are intended to reduce technique sensitivity, but their bonding remains largely inconsistent. Therefore, this study investigated whether pre-cure contact time and dentin surface finish affect immediate bond strength and interfacial morphology of two commercial SAFRCs. Sound human molars were allocated to 12 groups: two SAFRCs (Vertise™ Flow; Constic) × two finishes (fine vs. coarse diamond) × three pre-cure contact times (immediate/0 min, 1 min, 5 min). For positive controls a universal adhesive/conventional composite were applied. Three 2 × 2-mm cylinders/group were bonded to mid-coronal dentin discs and were light-cured (20 s; 950 mW/cm²) and tested in shear bond strength setup (SBS; 24 h at 1 mm/min). One fractured disc/group was examined by SEM and ~ 1-mm interface slices underwent Masson’s trichrome and were imaged at 100× with calibrated scaling. The 12 SAFRC groups were analyzed by three-way ANOVA with Tukey’s (α = 0.05); comparisons with the matched controls were performed separately using one-way ANOVA followed by Dunnett’s test. Material (p = 0.02) and application time (p < 0.0001) significantly affected SBS; surface finish did not (p = 0.97). Five-minute pre-cure contact yielded the highest SBS for both SAFRCs and, in several groups, values not significantly different from the matched controls. SEM showed an application time-dependent improvement of the interface quality: with 0 min application showing no continuous interfacial resin/tubule tags; from 1 to 5 min, progressively continuous resin fronts with tags, most evident at 5 min, irrespective of finish. Masson’s trichrome revealed a more conspicuous dark-pink collagen band at the interface of immediate cure samples and attenuated/discontinuous after 1–5 min. Surface finish mainly altered interfacial contour without qualitative improvement. Prolonged pre-cure contact enhances SAFRC bonding; the tested roughness range was not determinative. Trichrome staining corroborates shallow demineralization with partially exposed collagen, indicating limited monomer infiltration and explaining the material-dependent, low bond efficacy of current SAFRCs.
Miranda et al. (Thu,) studied this question.