Objective The aim of this study was to assess and compare the impact of bulk-fill flowable resin composite liners (BFFL) on the 2-year clinical performance of bulk-fill ormocer (BORC) in comparison to methacrylate-based resin composites (BMRC) in Class II cavities. Materials and Methods Thirty participants, each aged between 18 and 30 years, were included in the study, each presenting four class II cavities. A total of 120 restorations were placed, with participants randomly assigned to one of four restorative systems through a blind drawing: Admira Fusion X-Tra (AFX) alone, AFX after lining with Admira Fusion Xtra-Base (AFB), X-Tra Fill (XF) for complete cavity filling, and XF after lining with Xtra-Base (XB). The universal adhesive system (Futura U bond Voco, Germany) was consistently applied for all restoration techniques using selective enamel etching. A single operator, following the manufacturer's instructions for each material, performed all restorations, and finishing/polishing occurred immediately after placement. Clinical evaluation, based on World Dental Federation (FDI) criteria, was conducted by two blinded examiners at baseline (7 days) and at 6, 12, and 24 months postoperatively. Results The chi-squared test was used to compare the four applied restorative systems within each follow-up period, while the marginal homogeneity test was employed to assess changes over time. No statistically significant differences were observed among the four restorative systems at any evaluation period. Conclusions After 2 years, the clinical performance of BFFL or complete bulk-fill technique remained similar, regardless of the material composition.

In-office bleaching with hydrogen peroxide (HP) is effective, but prolonged application times and multiple sessions may alter the enamel surface and trigger adverse cellular responses. TiO₂-assisted HP bleaching could enhance whitening efficacy while reducing the application time. This study evaluated whether TiO₂ incorporation could improve bleaching efficiency with a shorter application time while limiting adverse enamel and cellular effects. Forty enamel–dentin specimens were assigned to four bleaching protocols (n = 10): 40% HP for 40 min (G1), 40% HP containing 1 wt% TiO₂ for 20 min (G2) or 40 min (G3), and 40% HP for 20 min (G4). All groups received standardized LED irradiation. Evaluations included color change, enamel microhardness, and surface roughness. Conditioned media were applied to human dental pulp stem cells (hDPSCs) and evaluated the cellular oxidative response in hDPSC lysates using a commercial Human ROS ELISA assay. Cellular metabolic activity and morphology were assessed by MTT assay, phase-contrast microscopy, and scanning electron microscopy (SEM), respectively. All protocols resulted in measurable whitening, and G2 showed whitening performance comparable to G1 despite half the application time. G1 showed the lowest post-treatment microhardness and the highest surface roughness, whereas G4 showed the least alteration to enamel. ROS ELISA measurements differed among the experimental conditions, with the highest level observed in G3. All conditioned media reduced hDPSC metabolic activity related to the control, with differences among the bleaching protocols and exposure periods. According to the results of this in-vitro study, incorporating 1 wt% TiO₂ into HP bleaching gel under LED irradiation enabled a shorter application protocol to achieve whitening comparable to the conventional longer-duration protocol while reducing enamel surface alterations. Although TiO₂-assisted protocols produced higher cellular ROS levels, these levels did not show a directly proportional relationship with cellular metabolic activity or morphology.