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Synergistic effect of wire bending and salivary pH on surface properties and mechanical properties of orthodontic stainless steel archwires.

Hobbelink MG, He Y, Xu J, Xie H, Stoll R, Ye Q - Prog Orthod (2015)

Bottom Line: A significant effect was found between Ra-values regarding the main effect of pH, ignoring the influence of shape.Bigger surface irregularities were seen on SEM images of straight wires immersed in artificial saliva at pH 5.6 compared to artificial saliva at other pH values.Ra showed a comparable result of surface roughness to Ra-value measured by the profilometer.

View Article: PubMed Central - PubMed

Affiliation: Orthodontic Department, College of Medicine and Dentistry, James Cook University, Cairns, Australia.

ABSTRACT

Background: The aim of this study was to investigate the corrosive behaviour of stainless steel archwires in a more clinically relevant way by bending and exposing to various pH.

Methods: One hundred and twenty pieces of rectangular stainless steel wires (0.43 × 0.64 mm) were randomly assigned into four groups. In each group, there were 15 pieces of bent wires and 15 straight ones. Prior to measurements of the wires, as individual experimental groups (group 1, 2, and 3), the wires were exposed to artificial saliva for 4 weeks at pH 5.6, 6.6, and 7.6, respectively. A control group of wires (group 4) remained in air for the same period of time before sent for measurements. Surface roughness (Ra-value) was measured by a profilometer. Young's modulus and maximum force were determined by a four-point flexural test apparatus. Scanning electron microscopy was used to observe the surface morphology of straight wire. Differences between groups were examined using a two-way analysis of variance (ANOVA).

Results: Mean surface roughness values, flexural Young's moduli, and maximum force values of bent wires are significantly different from those of the straight wires, which was the main effect of wire bending, ignoring the influence of pH. A significant effect was found between Ra-values regarding the main effect of pH, ignoring the influence of shape. There was a significant interaction effect of bending and pH on flexural Young's moduli of stainless steel archwires, while pH did not show much impact on the maximum force values of those stainless steel wires. Bigger surface irregularities were seen on SEM images of straight wires immersed in artificial saliva at pH 5.6 compared to artificial saliva at other pH values. Surface depth (Rz) was more sensitive than Ra in revealing surface roughness, both measured from 3D reconstructed SEM images. Ra showed a comparable result of surface roughness to Ra-value measured by the profilometer.

Conclusions: Bending has a significant influence on surface roughness and mechanical properties of rectangular SS archwires. pH plays a synergistic effect on the change of mechanical properties of stainless steel (SS) wires along with wire bending.

No MeSH data available.


Related in: MedlinePlus

Comparison of surface roughness, Young’s modulus, and maximum force of bent and straight wires. Surface roughness (Ra-value, μm) of bent and straight SS archwires was measured by a profilometer; flexural Young’s modulus (GPa) and maximum force (N) of bent and straight SS archwires were measured by a four-point bending test; surface roughness (Ra and Rz,μm) of straight SS wires were measured via 3D reconstruction of SEM images. All measured wires were exposed to air or immersed in artificial saliva at pH 5.6, 6.6, and 7.6 for 4 weeks according to protocol
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Fig4: Comparison of surface roughness, Young’s modulus, and maximum force of bent and straight wires. Surface roughness (Ra-value, μm) of bent and straight SS archwires was measured by a profilometer; flexural Young’s modulus (GPa) and maximum force (N) of bent and straight SS archwires were measured by a four-point bending test; surface roughness (Ra and Rz,μm) of straight SS wires were measured via 3D reconstruction of SEM images. All measured wires were exposed to air or immersed in artificial saliva at pH 5.6, 6.6, and 7.6 for 4 weeks according to protocol

Mentions: The Ra-value of the bent wires was significantly higher than that of the straight wires in all three pH groups (p < 0.000), where the straight wires in the control group had the lowest Ra-value (8.2 ± 0.9) × 10−2 μm and the bent wire had the roughest surface (24.1 ± 4.5) × 10−2 μm after being immersed in artificial saliva of pH 5.6 for 4 weeks (Table 1). Surface roughness from different pH groups showed highly varied Ra-values in both the bent and straight wires (p < 0.000) (Fig. 4).Table 1


Synergistic effect of wire bending and salivary pH on surface properties and mechanical properties of orthodontic stainless steel archwires.

Hobbelink MG, He Y, Xu J, Xie H, Stoll R, Ye Q - Prog Orthod (2015)

Comparison of surface roughness, Young’s modulus, and maximum force of bent and straight wires. Surface roughness (Ra-value, μm) of bent and straight SS archwires was measured by a profilometer; flexural Young’s modulus (GPa) and maximum force (N) of bent and straight SS archwires were measured by a four-point bending test; surface roughness (Ra and Rz,μm) of straight SS wires were measured via 3D reconstruction of SEM images. All measured wires were exposed to air or immersed in artificial saliva at pH 5.6, 6.6, and 7.6 for 4 weeks according to protocol
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4621974&req=5

Fig4: Comparison of surface roughness, Young’s modulus, and maximum force of bent and straight wires. Surface roughness (Ra-value, μm) of bent and straight SS archwires was measured by a profilometer; flexural Young’s modulus (GPa) and maximum force (N) of bent and straight SS archwires were measured by a four-point bending test; surface roughness (Ra and Rz,μm) of straight SS wires were measured via 3D reconstruction of SEM images. All measured wires were exposed to air or immersed in artificial saliva at pH 5.6, 6.6, and 7.6 for 4 weeks according to protocol
Mentions: The Ra-value of the bent wires was significantly higher than that of the straight wires in all three pH groups (p < 0.000), where the straight wires in the control group had the lowest Ra-value (8.2 ± 0.9) × 10−2 μm and the bent wire had the roughest surface (24.1 ± 4.5) × 10−2 μm after being immersed in artificial saliva of pH 5.6 for 4 weeks (Table 1). Surface roughness from different pH groups showed highly varied Ra-values in both the bent and straight wires (p < 0.000) (Fig. 4).Table 1

Bottom Line: A significant effect was found between Ra-values regarding the main effect of pH, ignoring the influence of shape.Bigger surface irregularities were seen on SEM images of straight wires immersed in artificial saliva at pH 5.6 compared to artificial saliva at other pH values.Ra showed a comparable result of surface roughness to Ra-value measured by the profilometer.

View Article: PubMed Central - PubMed

Affiliation: Orthodontic Department, College of Medicine and Dentistry, James Cook University, Cairns, Australia.

ABSTRACT

Background: The aim of this study was to investigate the corrosive behaviour of stainless steel archwires in a more clinically relevant way by bending and exposing to various pH.

Methods: One hundred and twenty pieces of rectangular stainless steel wires (0.43 × 0.64 mm) were randomly assigned into four groups. In each group, there were 15 pieces of bent wires and 15 straight ones. Prior to measurements of the wires, as individual experimental groups (group 1, 2, and 3), the wires were exposed to artificial saliva for 4 weeks at pH 5.6, 6.6, and 7.6, respectively. A control group of wires (group 4) remained in air for the same period of time before sent for measurements. Surface roughness (Ra-value) was measured by a profilometer. Young's modulus and maximum force were determined by a four-point flexural test apparatus. Scanning electron microscopy was used to observe the surface morphology of straight wire. Differences between groups were examined using a two-way analysis of variance (ANOVA).

Results: Mean surface roughness values, flexural Young's moduli, and maximum force values of bent wires are significantly different from those of the straight wires, which was the main effect of wire bending, ignoring the influence of pH. A significant effect was found between Ra-values regarding the main effect of pH, ignoring the influence of shape. There was a significant interaction effect of bending and pH on flexural Young's moduli of stainless steel archwires, while pH did not show much impact on the maximum force values of those stainless steel wires. Bigger surface irregularities were seen on SEM images of straight wires immersed in artificial saliva at pH 5.6 compared to artificial saliva at other pH values. Surface depth (Rz) was more sensitive than Ra in revealing surface roughness, both measured from 3D reconstructed SEM images. Ra showed a comparable result of surface roughness to Ra-value measured by the profilometer.

Conclusions: Bending has a significant influence on surface roughness and mechanical properties of rectangular SS archwires. pH plays a synergistic effect on the change of mechanical properties of stainless steel (SS) wires along with wire bending.

No MeSH data available.


Related in: MedlinePlus