Influence of intraoral application of antiseptics and fluorides during orthodontic treatment on corrosion and mechanical characteristics of nickel-titanium alloy in orthodontic appliances.

OBJECTIVES: To explore whether the commercial agents recommended for controlling dental biofilm formation had a significant effect in vivo on mechanical and corrosion properties of nickel-titanium (NiTi) alloy. MATERIALS AND METHODS: NiTi archwires (dimensions 0.508 × 0.508 mm) were collected from 36 orthodontic patients aged 13-42 years after a 3-month intraoral exposure. Three experimental groups were formed: (1) subjects conducting regular oral hygiene, (2) subjects who used fluorides for intensive prophylaxis for the first month, and (3) subjects who used chlorhexidine in the same manner. Corrosion behavior, surface characteristics, stiffness, hardness, and friction were analyzed. RESULTS: Exposure to intraoral conditions significantly reduced the stiffness and hardness of the NiTi alloy (P ≤ .015). Fluoride tended to reduce stiffness and hardness more than did saliva or antiseptic, but not significantly. Roughness and friction were not significantly influenced by oral exposure. Intraoral aging predominantly produced general corrosion independent of the adjuvant prophylactic agent, although localized corrosion may also have occurred. CONCLUSIONS: Fluorides and the antiseptic chlorhexidine do not increase corrosion more than saliva itself, nor do they further modify the mechanical properties of the NiTi alloy.