Effects of different fluoride recharging protocols on fluoride ion release from various orthodontic adhesives

Objective

The purpose of this study was to find the most effective fluoride recharging protocol for orthodontic adhesives.

Methods

Five orthodontic adhesives were used: a non-fluoride-releasing composite, a fluoride-releasing composite, a polyacid-modified composite (compomer), and two resin-modified glass-ionomer cements (RMGICs). Each specimen was placed into deionized water (DW) and the initial fluoride ion release was measured for 2 months. Each specimen was then subjected to four different treatments to simulate a fluoride recharge: 1000 ppm NaF solution, acidulated phosphate fluoride gel (APF), fluoride-containing dentifrice and DW (control). After topical fluoride treatment, each specimen was submitted to fluoride re-release tests.

Results

Fluoride-containing adhesives initially showed higher rates of fluoride ion release, but significantly declined to lower levels. The overall cumulative fluoride ion release during the initial period was RMGICs > compomer > fluoride-containing composite > non-fluoride-releasing composite. After topical fluoride treatment, the amount of fluoride ion re-released was proportional to the amount of fluoride ion previously released from the adhesives. However, the amount of fluoride ions released only lasted for 2 days and then returned to the levels before fluoride application. The overall cumulative fluoride ion re-release according to the fluoride treatments was APF and NaF solution > dentifrice.

Conclusion

This study suggests that using the combination of RMGICs and a fluoride-containing mouth rinse solution is the most effective protocol for long-term fluoride re-release from orthodontic adhesives, given the difficulty of routine use of APF at home, although all topical fluoride treatments can recharge fluoride ion in adhesives.