OBJECTIVE: This study aimed to investigate the influence of fluoride and an acidic environment on the mechanical properties of NiTi orthodontic wires (NiTiW) in artificial saliva. DESIGN: A prospective laboratory investigation. SETTING: Department of Stomatology, First Affiliated Hospital, Zhejiang University, Hangzhou, China. MATERIALS AND METHODS: Commercial, round 0.016-inch NiTiW were immersed in 0% or 0.05% Natrium-Fluoride-containing artificial saliva at a pH of 4 or 6 for one or three days, respectively. NiTiW were examined with a three-point bending test, Vickers' microhardness tests and surface morphology observation (SEM). RESULTS: A pH of 4 increased microhardness and decreased the three-point bending strength significantly (P≤0.05), whereas immersion time and fluoride concentration had no significant influence on the microhardness or on the three-point bending strength (P>0.05). When examining the test group NiTiWs after three days of immersion at a pH of 4 the SEM revealed a rough surface morphology, a damaged oxide layer and signs of corrosion. CONCLUSIONS: The most influential factor for decreasing the unloading force and increasing the hardness seems to be the pH value, whereas immersion time and NaF addition do not have a major influence.
RCT Entities:
OBJECTIVE: This study aimed to investigate the influence of fluoride and an acidic environment on the mechanical properties of NiTi orthodontic wires (NiTiW) in artificial saliva. DESIGN: A prospective laboratory investigation. SETTING: Department of Stomatology, First Affiliated Hospital, Zhejiang University, Hangzhou, China. MATERIALS AND METHODS: Commercial, round 0.016-inch NiTiW were immersed in 0% or 0.05% Natrium-Fluoride-containing artificial saliva at a pH of 4 or 6 for one or three days, respectively. NiTiW were examined with a three-point bending test, Vickers' microhardness tests and surface morphology observation (SEM). RESULTS: A pH of 4 increased microhardness and decreased the three-point bending strength significantly (P≤0.05), whereas immersion time and fluoride concentration had no significant influence on the microhardness or on the three-point bending strength (P>0.05). When examining the test group NiTiWs after three days of immersion at a pH of 4 the SEM revealed a rough surface morphology, a damaged oxide layer and signs of corrosion. CONCLUSIONS: The most influential factor for decreasing the unloading force and increasing the hardness seems to be the pH value, whereas immersion time and NaF addition do not have a major influence.
Authors: Wojciech Zakrzewski; Maciej Dobrzynski; Wojciech Dobrzynski; Anna Zawadzka-Knefel; Mateusz Janecki; Karolina Kurek; Adam Lubojanski; Maria Szymonowicz; Zbigniew Rybak; Rafal J Wiglusz Journal: Nanomaterials (Basel) Date: 2021-01-28 Impact factor: 5.076