Fluoride Release, Recharge, and Microhardness of Bioactive Restorative Materials: An In Vitro Study
Fluoride, vol.59, no.4, 2026 (SCI-Expanded, Scopus)
- Publication Type: Article / Article
- Volume: 59 Issue: 4
- Publication Date: 2026
- Journal Name: Fluoride
- Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, BIOSIS, EMBASE, Directory of Open Access Journals
- Keywords: Bioactive materials, Fluoride release, Fluoride recharge, Microhardness
- Hacettepe University Affiliated: Yes
Abstract
Purpose: The aim of this in vitro study was to evaluate fluoride release, fluoride recharge capacity, and time-dependent changes in surface microhardness of different bioactive restorative materials. Methods: A total of 36 disk-shaped specimens were prepared using three bioactive restorative materials: Equia Forte (E), Riva Light Cure (R), and Beautifil II (B) (n = 12 per group). All specimens were finished using a standardized polishing procedure. Fluoride release was measured spectrophotometrically and expressed in parts per million (ppm) at 1, 3, 7, 14, and 28 days. Following the initial measurement period, specimens were subjected to a fluoride recharge protocol using a fluoride varnish, and fluoride re-release was subsequently evaluated. Surface microhardness was measured using a Vickers microhardness tester at baseline, after 28 days, and after the recharge procedure. Data were analyzed using repeated-measures ANOVA and Tukey’s post hoc test (α = 0.05). Results: Fluoride release was significantly influenced by material type and time (p <0.05). Equia Forte exhibited the highest initial fluoride release, followed by a marked decrease over time, whereas Beautifil II demonstrated lower but more stable release values. Riva Light Cure showed intermediate behavior. Following fluoride recharge, all materials exhibited renewed fluoride release, with significant differences among groups (p <0.05). Microhardness values decreased over time in all materials (p <0.05), with the greatest reduction observed in Equia Forte and the most stable values in Beautifil II. Fluoride recharge did not result in a statistically significant change in microhardness (p > 0.05). Conclusions: Fluoride release, recharge capacity, and microhardness were found to be material-dependent. While fluoride recharge enhanced fluoride re-release, it did not improve mechanical properties. These findings suggest that the long-term performance of bioactive restorative materials is influenced by both their ion release behavior and structural characteristics.