Effect of pH and temperature on orthodontic NiTi wires immersed in acidic fluoride solution.
Orthodontic arch wires can confront diverse pH and temperature conditions in the oral cavity after replacement. The current study evaluated the effect of pH and temperature on orthodontic NiTi arch wires after immersion in an acidic fluoride solution. The acetic acid added for the adjustment of pH forms hydrofluoric acid (HF). More HF was formed in a solution of lower pH with higher temperature than that of the higher pH with lower temperature. Within the same pH value, the temperature of the solution affected the concentration of HF. Each as-received wire exhibited quite different microhardness values. The reduction of microhardness, 1.2-5.7%, occurred after immersion. Within the same product, however, the pH and temperature had minor influence on the reduction. The volumetric weight change, concentration of the released elements, and surface morphology were influenced by pH and temperature. At pH 3.5 of 60 degrees C solution, the greatest weight loss, release of elements, and corrosion of surface occurred from the wires. At pH 6, on the other hand, no such loss or release occurred regardless of temperature. At 5 degrees C solution, the surface exhibited minor corrosion regardless of pH value.
Ahn
Hyung-Soo
HS
Department of Dental Materials, College of Dentistry and Medical Research Institute, Pusan National University, Pusan 602-739 Korea.
Kim
Myong-Jin
MJ
Seol
Hyo-Joung
HJ
Lee
Jung-Hyun
JH
Kim
Hyung-Il
HI
Kwon
Yong Hoon
YH
D000497:Alloys; D003343:Corrosion; D006858:Hydrofluoric Acid; D006863:Hydrogen-Ion Concentration; D009532:Nickel; D009969:Orthodontic Wires; D013696:Temperature; D014025:Titanium
D000497:Alloys; D009532:Nickel; D014025:Titanium; D006858:Hydrofluoric Acid