In Vitro Hydrolytic Degradation of Giomer-Based and Fluoride-Releasing Bulk Fill Composites Simulated for Patients with Gastroesophageal Reflux Disease

Gastroesophageal reflux disease (GERD) often leads to tooth demineralization and degradation of dental restorations, increasing surface roughness and reducing strength. Limited studies have addressed acidic pH effects on fluoride-releasing giomer composites. This in vitro study evaluates surface roughness and flexural strength (FS) of six bulk-fill composites─STARK, Filtek One Bulk Fill Restorative (FBF), SureFil SDR Flow (SDR), Tetric N-Ceram (TNC), X-tra fil VOCO, and Beautifil-Bulk restorative (BBR)─before and after acidic exposure and abrasion caused by brushing cycles. Specimens tested included 60 disks (2 mm thick, 8 mm diameter) for surface roughness and 60 bar (25 mm × 2 mm × 2 mm) for FS. Samples were immersed in hydrochloric acid (pH 1.2) at 37 °C for 24 h, followed by 5000 brushing cycles (100 cycles/min) using medium-bristle toothbrushes. Surface roughness (Ra) and FS were measured at the baseline and post-treatment. Statistical analysis was performed by conducting Shapiro–Wilk tests, one-way ANOVA, and Tukey posthoc tests (α = 0.05). Results showed that BBR exhibited the highest increase in surface roughness after acidic exposure and brushing, followed by SDR, TNC, and VOCO. FBF and STARK demonstrated minimal changes. FS reduction was most significant in BBR (86.11 to 69.79 MPa, 18.95%) and SDR (106.78 to 88.27 MPa, 17.14%). These findings suggest that giomer-based fluoride-releasing composites, such as BBR and SDR, are susceptible to acidic degradation and brushing wear.