Effects of endodontic irrigants on surface roughness of flowable and conventional composite resins

To evaluate the effects of endodontic irrigants on the surface roughness of flowable and conventional composite resins using contact profilometry and atomic force microscopy (AFM). Seventy-two discs were prepared from a flowable and a conventional resin composite (n = 36 each). Specimens were immersed in 5.25% NaOCl, 17% EDTA, or sequential NaOCl + EDTA. Surface roughness (R_a) was measured before and after irrigation with a contact profilometer; nano-topography was quantified on 45 µm × 45 µm areas using AFM. Data were analyzed with mixed-model repeated measures ANOVA and paired t-tests (α = 0.05). Profilometry revealed a significant R_a increase only in the flowable resin composite after NaOCl + EDTA (p = 0.009); no significant changes were detected in the conventional resin composite for any irrigant. AFM showed consistently higher nano-roughness in the conventional resin composite than in the flowable resin composite for all solutions (p < 0.001). NaOCl and NaOCl + EDTA significantly reduced AFM R_a in the flowable resin composite, whereas EDTA significantly decreased R_a in the conventional resin composite. Irrigation-induced surface changes are material- and method-dependent. Flowable resin composites are more susceptible to macro-scale roughening under sequential NaOCl + EDTA, while conventional resin composites exhibit greater chemical stability. Combined use of profilometry and AFM provides a more comprehensive assessment of irrigant-related surface alterations.