Nanoindentation of orthodontic archwires: The effect of decontamination and clinical use on hardness, elastic modulus and surface roughness.
OBJECTIVE
The purpose of this research was to investigate the effects of decontamination and clinical exposure on the elastic moduli, hardness and surface roughness of two frequently used orthodontic archwires, namely 0.020in.x0.020in. heat activated (martensitic active) nickel titanium archwires and 0.019in.x0.025in. austenitic stainless steel archwires.


METHODS
This study was a prospective clinical trial in which 20 consecutive patients requiring an archwire change as part of their course of orthodontic fixed appliance therapy, had either a nickel titanium or stainless steel archwire fitted as deemed clinically necessary. The effect of clinical use was determined by comparing distal end cuts of the "as received" archwires before and after decontamination, with the same retrieved archwires following clinical use and decontamination. Hardness, elastic modulus and surface roughness were determined using an atomic force microscope (AFM) coupled with a nanoindenter.


RESULTS
The results showed that the decontamination regimen and clinical use had no statistically significant effect on the nickel titanium archwires, but did have a statistically significant effect on the steel archwires. Decontamination of the steel wires significantly increased the observed surface hardness (p=0.01) and reduced the surface roughness (p=0.02). Clinical use demonstrated a statistically significant increase in the observed elastic modulus (p<0.001) and a decrease in surface roughness (p=0.001).


CONCLUSIONS
At present it is difficult to predict the clinical significance of these statistically significant changes in archwire properties on orthodontic tooth movement.
Alcock
Joseph P
JP
Division of Child Dental Health, Bristol Dental School, University of Bristol, Bristol, UK.
Barbour
Michele E
ME
Sandy
Jonathan R
JR
Ireland
Anthony J
AJ
D003666:Decontamination; D003722:Dental Alloys; D003799:Dental Stress Analysis / Q000379:methods*; D055119:Elastic Modulus; D017743:Equipment Reuse; D006244:Hardness; D006801:Humans; D036103:Nanotechnology; D009532:Nickel; D009969:Orthodontic Wires; D010865:Pilot Projects; D011446:Prospective Studies; D013193:Stainless Steel; D013499:Surface Properties; D014025:Titanium
D003722:Dental Alloys; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium