Fluoride Release and Recharge of Orthodontic Adhesives after Exposure to Sodium Fluoride Mouthwash: An In Vitro Study

AimFluoride‑releasing orthodontic adhesives with the ability to recharge fluoride may help prevent white spot lesions during orthodontic treatment. This study aimed to evaluate the effect of sodium fluoride (NaF) mouthwash on the fluoride release and recharge capacity of orthodontic adhesives over a ۲۸‑day period.MethodsIn this in vitro study, ۳۶ extracted sound human maxillary premolars were randomly assigned to three groups (n=۱۲): No‑Mix composite resin (Ortho Organizer Everest, USA) for bracket bonding, resin‑modified glass ionomer (RMGI; GC Corporation, Tokyo, Japan) for bracket bonding, and sound enamel without bracket bonding (control). Each group was further divided into two subgroups (n=۶) based on the storage condition: daily exposure to ۲۵۰ ppm sodium fluoride (NaF) mouthwash or artificial saliva. After bracket bonding, each tooth was individually immersed in artificial saliva and incubated at ۳۷°C. Cumulative fluoride release was measured using a spectrophotometer (InoLab® Multi ۹۴۲۰, WTW, Germany) on days ۱, ۷, ۱۴, and ۲۸. Following the ۲۸‑day period, the fluoride recharge capacity of the materials was evaluated by daily exposure to ۲۵۰ ppm NaF mouthwash for one minute, after which fluoride release was measured again using the same protocol. Data were analyzed using Kruskal–Wallis, repeated‑measures ANOVA, Friedman, and post hoc Tukey tests at a significance level of ۰.۰۵.ResultsFluoride release from all groups showed a significant decreasing trend over the ۲۸‑day period, with the highest levels observed on day ۱ (P<۰.۰۰۱). Daily exposure to ۲۵۰ ppm sodium fluoride mouthwash significantly increased fluoride release from both orthodontic adhesives compared with artificial saliva, particularly during the early evaluation periods. On day ۱, a significant difference in fluoride release was observed among the groups (P<۰.۰۰۱), with sound enamel demonstrating higher fluoride levels than the adhesive groups. A similar significant difference was noted on day ۷ (P<۰.۰۰۱). However, these differences diminished over time, and no statistically significant differences were detected among the groups at ۱۴ days (P=۰.۲۷۸) or ۲۸ days (P=۰.۰۶۱). Both No‑Mix composite resin and RMGI demonstrated fluoride recharge capability following NaF exposure, resulting in higher fluoride release compared with specimens not exposed to fluoride. Over time, the fluoride release patterns of the two adhesives became comparable, with no significant long‑term difference between them.ConclusionDaily exposure to sodium fluoride mouthwash appeared to enhance fluoride uptake and subsequent release in both No Mix composite resin and RMGI specimens. Although differences were observed at early time points, fluoride release patterns between the two adhesives became comparable over time. These findings suggest a potential fluoride recharge capability in both materials; however, the clinical relevance of these results should be interpreted with caution and may require further investigation.

کلیدواژه ها:

Composite resins ، Dental bonding ، Glass-ionomer ، Sodium fluoride