Effects of sodium fluoride mouth rinses on the torsional properties of miniscrew implants

Introduction: Effects of sodium fluoride (NaF) mouth rinse solutions on torsional properties of a miniscrew implant were investigated. Methods: As-received Ti-6Al-4V miniscrew implants (AbsoAnchor [Dentos, Inc., Daigu, Korea]) were immersed in 0.1% or 0.2% NaF mouth rinse solution (pH 5.12 and 5.14, respectively) for 1 hour or 24 hours. Miniscrew implants selected as controls were not immersed. Each implant was subjected to increasing torque until fracture (n = 5 in sample groups). Mean moment and twist angle for fracture were compared using 1-way analysis of variance (ANOVA). Surfaces of implants after immersion were observed with a scanning electron microscope (SEM). Electron microprobe and micro-x-ray diffraction analyses were performed to obtain composition information about deposits on implant surfaces. Results: Pits and cracks formed on the implant surfaces after immersion in both NaF mouth rinse solutions. Corrosion products, probably sodium aluminum fluoride (Na ₃AlF₆), were observed on the implants after immersion in both NaF solutions for both time periods. There were no significant differences for mean torque (P = 0.063) and twist angle (P = 0.696) at fracture compared with control implants. Conclusions: Although titanium alloy miniscrew implants corroded slightly from immersion in 0.1% or 0.2% NaF solutions, mouth rinsing by patients with the same fluoride solution concentrations should not cause deterioration of their torsional performance.