|Year : 2019 | Volume
| Issue : 4 | Page : 548-552
|Evaluation and comparison of surface characteristics of commercially available TMA wires using scanning electron microscopy and optical profilometer
Lidhiya Alexander1, Pradeep Babu Kommi1, Nandakumar Arani2, Anoop Mathew1, Anirudh Yashwant1, RS Senkutvan1
1 Department of Orthodontics and Dentofacial Orthopaedics, Indira Gandhi Institute of Dental Sciences, Sri Balaji Vidyapeet University, Puducherry, Tamil Nadu, India
2 Department of Orthodontics and Dentofacial Orthopaedics, Meenakshi Ammal Dental College, Chennai, Tamil Nadu, India
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|Date of Submission||15-May-2018|
|Date of Decision||11-Jul-2018|
|Date of Acceptance||16-Aug-2018|
|Date of Web Publication||18-Nov-2019|
| Abstract|| |
Aim: The aim of this study was to evaluate and compare the surface characteristics of colored titanium molybdenum alloy archwires (purple-coated TMA and honey dew-coated TMA) and the regular titanium molybdenum alloy archwires. Materials and Methods: The experiment comprised three groups, Group I – regular TMA archwires, Group II – purple-coated TMA archwires, Group III – honey dew-coated TMA wires involving 21 samples each. The surface characteristics were assessed using scanning electron microscopy and optical profilometer. Results: The results were statistically analyzed using analysis of variance wherein Group I regular TMA wires exhibited a root mean square value of 148.071 nm and a standard deviation of 9.0027 nm followed by group II (purple-coated TMA wires) which showed a root mean square value of 84.095 nm with a standard deviation of 2.6005 nm, while group III (honey dew-coated TMA wires) was found to have a root mean square value of 71.681 nm with a standard deviation of 1.4645 nm on subjecting to optical profilometry. Conclusion: The surface roughness is higher for regular TMA wire exhibiting superior characteristic of color-coated TMA wires, especially honey dew-coated TMA wires over the regular and purple-coated TMA wires. This property of the archwires details regarding its application in both sliding and frictionless mechanics in retraction phase of fixed orthodontic treatment.
Keywords: Optical profilometer, scanning electron microscopy, titanium molybdenum alloy wires
|How to cite this article:|
Alexander L, Kommi PB, Arani N, Mathew A, Yashwant A, Senkutvan R S. Evaluation and comparison of surface characteristics of commercially available TMA wires using scanning electron microscopy and optical profilometer. Indian J Dent Res 2019;30:548-52
|How to cite this URL:|
Alexander L, Kommi PB, Arani N, Mathew A, Yashwant A, Senkutvan R S. Evaluation and comparison of surface characteristics of commercially available TMA wires using scanning electron microscopy and optical profilometer. Indian J Dent Res [serial online] 2019 [cited 2020 Apr 1];30:548-52. Available from: http://www.ijdr.in/text.asp?2019/30/4/548/271059
| Introduction|| |
Orthodontics is a profession where knowledge of materials plays an important role, as these materials and their characteristics influence the intensity and extent of the tooth movement.
Titanium molybdenum alloy archwires are gaining popularity due to various characteristics such as flexibility, adaptability, and weldability enabling us to utilize them in different stages of orthodontic treatment. One of the significant problems encountered by orthodontists during treatment in retraction phase is friction exerted at the bracket and archwire interface which prevents the tooth movement through binding and notching of archwires, thereby reducing the treatment duration. Hence, there were several attempts to reduce the friction of beta titanium archwires by surface treatment through ion implantation that possessed the properties aiding in the reduction of friction during tooth movement further improving the prime properties of the regular TMA wires and also offered patients exciting new looks.
Optical profilometer has various advantages such as surface independence and lack of modeling with a stylus tip radius of 20 nm which makes its use highly acceptable.
Hence, the purpose of this study is to evaluate and compare the surface characteristics of 0.019″ × 0.025″ regular TMA archwires and color-coated wires, namely, 0.019″ × 0.025″ purple TMA archwires and 0.019″ × 0.025″ honey dew TMA archwires.,
| Materials and Methods|| |
This study involves three different groups of archwires, namely, 0.019″ × 0.025″ regular TMA, 0.019″ × 0.025″ honey dew TMA, and 0.019″ × 0.025″ purple TMA comprising 21 samples each that are tested for surface characteristics after the clearance obtained from the institutional review board and ethical committee of the institute.
The evaluation of surface characteristics was determined by subjecting the samples to scanning electron microscopy (SEM) (FEI Quanta, FEG 200, Hillsboro) and to optical profilometer (Taylor Hobson, Talysurf CCI, Leicester, UK & Taly map software (Talysurf, UK)) to estimate the surface roughness of the samples in order to obtain the corresponding numerical values.
In this study, all the 21 samples are subjected to SEM at 500× magnification [Figure 1]. The mean kinetic friction among normal TMA wire and purple TMA wire was taken as 5.50 ± 0.32 and 5.70 ± 0.07, respectively, from previous literature. The α error is fixed to 0.05 and with a power of 80%, the sample size is calculated using the formula:
|Figure 1: Wire samples placed on the stud of scanning electron microscope (FEI Quanta, FEG 200, Hillsboro) for scanning electron microscopy study|
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n = 21
Each sample is cut to a size of 1 inch and before subjecting to SEM, it is physically checked for any distortions and the surface is cleaned with ethanol to remove any debris present on the surface. These 0.019″ × 0.025″ TMA samples are mounted onto a stud and subjected to SEM. The images obtained from these samples are evaluated.,,
Even though SEM gives us standard high-quality images, quantitative evaluation of these images is difficult and may not be possible. So, optical profilometer was used in this study to get the quantitative measurements which is highly useful and standardized way to compare the surfaces of the different sample groups. The test was done by taking the sample, wherein a probe of the optical profilometer comes in contact with the sample. The 3D instrument measures the height over an area of x and y lateral dimensions. The samples provide the mean roughness (Ra) of specimens in microns [Figure 2]. Surface at three different sites were tested for a particular specimen and the readings were tabulated in micrometers and the evaluation was repeated for all the 21 samples of each group.,
|Figure 2: Optical profilometer (Taylor Hobson, Talysurf) with graphical readings recorded from the monitor|
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The mean and standard deviation were estimated from the sample for each study group and the result was statistically analyzed using one-way analysis of variance followed by post hoc comparison test for multiple comparisons within the groups to evaluate and determine the group of statistical significance. Initial data analysis was used to determine the mean and standard error of the mean.
On multiple comparisons using post hoc test, Bonferroni test was employed for equal variances while Tamhane test was advocated for variances that were not equal resulting in statistically significant data. The data were tabulated and analyzed.
| Results|| |
The data obtained through post-statistical analysis were tabulated and analyzed. SEM evaluation of surface characteristics of the wires for group I under 500× magnification showed multiple small void areas and small craters with few elevated regions and small black patches distributed in the image [Figure 3]. Group II (0.019″ × 0.025″ rectangular purple-coated TMA wires) samples show uniform prominent striations and ridges with little or no voids [Figure 4]. Group III (0.019″ × 0.025″ honey dew-coated TMA wires) exhibited a relatively smooth surface when compared with the two alloys evaluated with horizontal drawing lines with very few voids [Figure 5].
|Figure 3: Scanning electron microscopy image at ×500 magnification and optical profilograph for Group I (0.019″ × 0.025″ regular TMA wires)|
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|Figure 4: Scanning electron microscopy image at ×500 magnification and optical profilograph for Group II (0.019″ × 0.025″ purple TMA wires)|
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|Figure 5: Scanning electron microscopy image at ×500 magnification and optical profilograph for Group III (0.019″ × 0.025″ honey dew TMA wires)|
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On subjecting the samples to optical profilometer, the root mean square values among all the 21 samples for group I (0.019″ × 0.025″ regular TMA wires) were found to be 148.071 nm, group II (0.019″ × 0.025″ purple TMA) had a value of 84.095 nm, and honey dew 0.019″ × 0.025″ TMA wires belonging to group III showed a root mean square value of 71.681 nm.
| Discussion|| |
Our concern after conducting the study was that the values obtained from this study should have a strong scientific support which may help the orthodontic community excel in dispatching their treatment therapy.
The surface characteristics were evaluated by subjecting the wire samples in an as-received condition to SEM and optical profilometry. As the SEM gives a very high contrast detailed images of the surface at 500× magnification, optical profilometeric (manufactured by Taylor Hobson from Talysurf) evaluation suggests root mean square roughness when the surface was scanned to study its topography over an area, when the probe is in contact with the archwire sample.
When subjected to optical profilometer, the root mean square values among all the 21 samples for group I (0.019″ × 0.025″ regular TMA wires) were found to be 148.071 nm with a standard deviation of 9.0027 nm and also a standard error value of 1.964 nm. At 95% confidence interval for mean, the lower bound was 143.973 nm and the upper bound was 152.169 nm. This study shows that there is an increase in surface roughness in uncoated TMA wires [Table 1]. This can be attributed to the results achieved for kinetic friction and we can suggest that increased frictional characteristics are due to increased surface roughness [Figure 3]. These regular TMA wires exhibited multiple small ovoid areas and tiny craters with few elevations on scanning electron microscopic evaluation at 500× magnification. The other two groups, which are 0.019″ × 0.025″ purple-coated and 0.019″ × 0.025″ honey dew-coated TMA wires, exhibited more surface smoothness by obtaining a less root mean square values. The surface characteristic features of these 0.019″ × 0.025″ regular TMA wires as obtained from the scanning electron micrographs were found to be in accordance with the experiments performed by Pradeep Babu et al., Yu and Huang, Agarwal CO and et al., and Krishnan and Kumar.
|Table 1: Mean surface characteristic values for all the 21 samples of all the three groups|
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Among group II (0.019″ × 0.025″ purple TMA), the root mean square values was noticed to be 84.095 nm with a standard deviation of 2.6005 nm and a standard error of 0.5675 nm. The lower and upper bound at 95% was found to be 82.912 and 85.279 nm with a minimum and maximum value readings of 80.4 and 88.9 nm [Table 1]. The group II (0.019″ × 0.025″ purple-coated TMA wires) has showed a drastic decrease in root mean square roughness values [Figure 4]. This can be due to the different process of ion implantation resulting in a layer of coating on the surface of the purple-coated TMA wires as mentioned through the studies performed by Isac et al., Krishnan et al., and Kula et al.
The honey dew 0.019″ × 0.025″ TMA wires belonging to group III shows a root mean square value of 71.681 nm with a standard deviation and standard error of 1.4645 and 0.3196 nm [Table 1]. For a 95% confidence interval, the lower bound was found to be 71.014 and 72.348 nm as the upper bound with a minimum value of 68.1 nm and maximum value of 74.3 nm [Figure 5]. The root mean square value obtained after evaluating with optical profilometry suggests a smooth surface area for honey dew-coated TMA wires. Study by Premanand et al. suggests that thicker coating of ion implantation is done for honey dew-coated wires when compared with the other coated wires. These results may be directly responsible for the low kinetic frictional values obtained while evaluating for frictional characteristics. Honey dew-coated TMA wires which have the least root mean square value with increased smoothness exhibited superior characteristics over the other wires as derived by Krishnan et al., Premanand et al., and Isac et al.
TMA wires with improved surface smoothness and reduced frictional characteristics, a major breakthrough was given by Burstone and Farzin-Nia  who showed that surface roughness of TMA wires was successfully altered by using ion-implantation.
Kusy et al. could not find any difference in surface roughness between colored-low friction and normal TMA wires. They found almost similar surface roughness (0.195 μm) for conventional and low friction types.
A mean difference of 63.9762 nm was evident on comparing group I (0.019″ × 0.025″ regular TMA wires) and group II (0.019″ × 0.025″ purple TMA wires) with a standard error of 2.0449 nm. At 95% confidence interval, the lower bound limit was 58.717 nm and the upper bound limit was 69.235 nm.
The results showed that ion-implanted TMA wires had reduced surface roughness compared to uncoated regular TMA wires which was in concurrence with the results of Burstone and Farzin-Nia, Krishnan and Kumar, D'Antò et al., and Krishnan et al.
When group I (0.019″ × 0.025″ regular TMA) was compared with group III (0.019″ × 0.025″ honey dew TMA), the mean surface characteristic value was -76.3905 nm while standard error was 1.9904 nm with an upper and lower limit of -71.230 and 81.551 nm, respectively.
On comparing the surface characteristics between group II (0.019″ × 0.025″ purple TMA) and group III (0.019″ × 0.025″ honey dew TMA wires), the mean difference of the two groups showed a value of 12.4143 nm with a standard error of 0.6513 nm. At 95% confidence interval, 10.772 nm was estimated to be the lower bound and 14.056 nm as the upper bound reading [Table 2]. Honey-dew-colored ion-implanted TMA wire showed the least surface roughness and found to be having better surface finish than purple-colored TMA wires. Similar results were obtained by Krishnan et al. and Premanand et al.
|Table 2: Comparison of characteristic values for all the 21 samples of all the three groups|
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When the root mean square values for all the three groups of the study were compared, the mean reading was found to be 101.283 nm with a standard deviation of 34.1668 nm and standard error of 4.3046 nm. On evaluation, with the mean values at 95% confidence interval, the lower bound was 92.678 nm with an upper bound of 109.887 nm. The minimum value was 68.1 nm while the maximum value was 174.6 nm. The root mean square value derived for the study done by optical profilometry ,, which is lesser than the group I (regular TMA) suggests a rougher surface characteristic in this group [Table 2].,,,
| Conclusion|| |
Honey dew-coated rectangular 0.019″ × 0.025″ TMA wires exhibited superior quality which has smooth surface characteristics when compared to the other two groups affording efficient retraction of teeth with sliding mechanics. Also, use of these smoother wires may be beneficial in effecting tooth movement in periodontally compromised patients. Purple-coated rectangular 0.019″ × 0.025″ TMA wires exhibited smooth surface characteristics when compared to regular 0.019″ × 0.025″ TMA wires. But the surface properties were inferior (rougher surface) when compared to honey dew 0.019″ × 0.025″ TMA wires. Regular TMA wires exhibited rougher surface when compared to the above two groups.
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Conflicts of interest
There are no conflicts of interest.
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Dr. Lidhiya Alexander
No 544/a, 3rd Cross Street, Kalaivanar Nagar, Danvantri, Gorimedu, Puducherry - 605 006
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]
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