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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 52  |  Issue : 4  |  Page : 238-242

Surface and mechanical properties of different coated orthodontic archwires


1 Senior Lecturer, Department of Orthodontics, SIBAR Institute of Dental Sciences, Guntur, Andhra Pradesh, India
2 Prof. and Head, Department of Orthodontics, SIBAR Institute of Dental Sciences, Guntur, Andhra Pradesh, India
3 Prof., Department of Orthodontics, SIBAR Institute of Dental Sciences, Guntur, Andhra Pradesh, India
4 Reader, Department of Orthodontics, SIBAR Institute of Dental Sciences, Guntur, Andhra Pradesh, India

Date of Submission19-Apr-2018
Date of Acceptance17-May-2018
Date of Web Publication17-Oct-2018

Correspondence Address:
Dr. Aruna Dokku
Department of Orthodontics, SIBAR Institute of Dental Sciences, Guntur, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jios.jios_241_17

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  Abstract 


Objectives: The objective of this study was to evaluate the mechanical properties and surface characteristics of coated superelastic Ni–Ti archwires of three companies with different coatings before and after clinical use. Materials and Methods: Coated 0.016 inch mandibular archwires of three different companies with different coatings (G & H – epoxy coated on all sides, Rocky Mountain Orthodontics (RMO) – Teflon coated on labial surface, and American Orthodontics (AO) – Teflon coated on all sides) were used in this study. Twenty wires from each company, 10 as received and 10 retrieved from patients after 4 weeks of clinical use, were tested for load deflection and surface roughness. An independent sample t-test was done to compare surface roughness and load-deflection characteristics and one-way ANOVA analysis to compare between groups. Results: Both retrieved and as-received G & H wires showed less force levels during loading and unloading compared to RMO and AO wires (P < 0.05). In both test and control groups, G & H wires produced slightly higher surface roughness values compared to AO and RMO. In all the three company wires, roughness values increased significantly before and after clinical use. Conclusion: Retrieved coated archwires of all the three companies produced lower loading and unloading force values compared to as-received coated archwires. Surface roughness of coated archwires increased after use.

Keywords: Archwires, coated wires, epoxy coating, load deflection, Ni–Ti wires, retrieved coated archwires, surface roughness


How to cite this article:
Dokku A, Peddu R, Prakash A S, Padhmanabhan J, Kalyani M, Devikanth L. Surface and mechanical properties of different coated orthodontic archwires. J Indian Orthod Soc 2018;52:238-42

How to cite this URL:
Dokku A, Peddu R, Prakash A S, Padhmanabhan J, Kalyani M, Devikanth L. Surface and mechanical properties of different coated orthodontic archwires. J Indian Orthod Soc [serial online] 2018 [cited 2018 Nov 14];52:238-42. Available from: http://www.jios.in/text.asp?2018/52/4/238/243610




  Introduction Top


There is an increasing demand for esthetics in patients not only after treatment but during treatment as well. To meet their demands, research in material science has progressed in dentistry particularly in orthodontics. Ceramic brackets were introduced long ago, but archwires remained unchanged which has become an esthetic concern.

Coated archwires were thought to be one of the acceptable solutions for this problem. Metallic archwires are coated with tooth-colored polymers such as Teflon or epoxy resin by different manufacturers to meet the demand of esthetics from patients.[1] But to be successful, best possible esthetics should be coupled with efficient performance. There is a possibility that original thickness of the archwire would be decreased to accommodate the surface coating which, in turn, may alter some of the properties of the wire, primarily load deflection.[2],[3]

Surface topography plays an important role to determine the efficiency of the archwire. Coating of archwires with different materials and their loss during clinical use may alter the surface roughness which will affect the frictional properties.[4] This study was undertaken as only limited number of studies [5],[6] was reported comparing the mechanical properties and surface roughness of as-received and retrieved coated archwires with similar coating. In this article, archwires with different coatings from different manufacturers were compared. The aims of the study were as follows:

  1. To investigate three different orthodontic coated archwires, as received and retrieved from patients for surface roughness
  2. To investigate three different orthodontic coated archwires, as received and retrieved from patients for load deflection.



  Materials and Methods Top


Thirty patients who were to undergo orthodontic treatment with fixed appliances were randomly selected with following inclusion criterion:

  1. No congenitally missing or extraction in the anterior region
  2. Pretreatment little's irregularity index >5.0 mm
  3. No congenital clefts or craniofacial syndromes
  4. No blocked out incisors in the mandibular arch.


Ethical approval was obtained from the Institutional Ethical Committee (Ref no: 17/IEC/CIR/14). Coated mandibular archwires of three different companies [Figure 1], [Figure 2], [Figure 3] were divided into six groups (I–III were test group wires retrieved from patient and IV to VI were control group wires as received from the manufacturer) [Table 1]. Randomization was done by submitting three groups of wires to three different operators who were unaware about details of the wire. The selected patients undergoing fixed orthodontic therapy were randomly allocated to each operator, and the archwires were ligated using Teflon-coated ligature wires (Classic Orthodontics, San Diego, CA, USA) [Figure 4] and [Figure 5]. Details of the patient, type of wire, date of insertion, and date of removal of the wires were noted by an observer.
Figure 1: G & H, 0.016 inch ultraesthetic coated archwires

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Figure 2: Rocky Mountain Orthodontics, 0.016 inch coated archwires

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Figure 3: American Orthodontics, 0.016 inch EverWhite coated archwires

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Table 1: Coated mandibular archwires of three different companies divided into six groups

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Figure 4: Teflon-coated ligature wires

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Figure 5: Coated archwire ligated using coated ligature wire

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After 4 weeks of clinical use, the archwires were retrieved and cleaned with distilled water as described by Eliades et al.[5] and were sent to laboratory within 48 h for testing the load deflection and surface roughness using universal testing machine and contact stylus profilometer, respectively. As-received wires from the same companies were also tested for surface roughness and load deflection, and the results were recorded and statistically analyzed.

Load deflection testing procedure

For three-point bending, a custom-made jig was fabricated, and two MBT brackets with a slot size of 0.022 × 0.028 inches were attached on the top of the parallel rods of the jig as proposed by Elayyan et al.[6] The jig was fixed to the base of universal testing machine [Figure 6]. The wire sample was attached to the brackets using ligature wire. The force was applied vertically with a rod attached to the moving part of the universal testing machine at a crosshead speed of 1 mm/min. The wire was deflected first by 1, 2, 3 mm, and loading values were noted at each of these deflections. Unloading was done in the order of 2 and 1 mm, and values were recorded.
Figure 6: Jig with wire under universal testing machine

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Surface roughness testing procedure

A contact stylus profilometer [Figure 7] with a stylus radius of 2.5 μm and tip angle of 90° traversing at a speed of 1 mm/s was used to evaluate the surface roughness of the wire samples. Cutoff length was 0.08 mm and measuring length was 1 mm. The following three readings were recorded Ra (arithmetic mean deviation of the roughness profile), Rq (root-mean-square deviation of the roughness profile) and Rz (10-spot average roughness) using contact stylus profilometer.
Figure 7: Contact stylus profilometer

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Statistical analysis

All the statistical analysis was done in the Statistical Package for the Social Sciences software (version 15, SPSS Inc., Chicago, USA). Descriptive statistics, means, and standard deviations were calculated and the associated P values were listed in tables [Table 2] and [Table 3]. An independent sample t-test was conducted to compare the surface roughness and load-deflection characteristics of as-received and retrieved coated archwires. One-way ANOVA analysis was computed to compare surface roughness and load-deflection characteristics between groups.
Table 2: Mean comparison among loading and unloading deflections of materials in test group and control group

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Table 3: Mean comparison among G and H, Rocky Mountain Orthodontics, and American Orthodontics surface roughness (μm) of RA, RQ, and RZ in test and control groups

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  Results Top


In the retrieved wires, Group I (G & H) wires showed less force levels to deflect the wire at 1, 2, and 3 mm during loading and unloading compared to Group II (Rocky Mountain Orthodontics [RMO) and Group III (American Orthodontics [AO]) wires (P < 0.05) [Table 2]. Group II and III wires required almost similar forces. There was a statistically significant difference between the three groups with P < 0.05.

In the as-received wires, Group IV (G & H) wires required less force levels to deflect the wire at 1, 2, and 3 mm during loading and unloading as compared to Group V (RMO) and Group VI (AO) wires. Group V wires produced slightly higher forces compared to other groups. However, there was no statistically significant difference between the groups with P > 0.05. Intragroup comparison was done between control and test sample [Table 2].

In both test and control groups, epoxy-coated (G & H) wires produced slightly higher surface roughness values compared to Teflon-coated wires (AO and RMO) but with no statistically significant difference between them (P > 0.05). In all the three wires, roughness values increased significantly after clinical use [Table 3].


  Discussion Top


The purpose of this study was to evaluate and compare the surface roughness and load-deflection properties of coated Ni–Ti wires of 0.016” from three different manufacturers under the same testing conditions using a contact stylus profilometer to measure surface roughness and three-point bending test to measure load-deflection properties.

In both retrieved wires and as-received wires, epoxy-coated (G & H) wires showed less force levels to deflect the wire, during loading and unloading compared to Teflon-coated (RMO and AO) wires. This could be due to the fact that the Teflon (RMO and AO) coating adds a minimal thickness (0.0008–0.001 inch) to the archwire, while the epoxy (G & H) coating adds considerable thickness (0.002 inch) to the archwire, so the coating of epoxy is thicker than that of the Teflon layer and may result in a smaller Ni–Ti inner core.[7],[8]

Even though statistically nonsignificant, RMO as-received wires required slightly higher forces during loading and produced slightly higher forces during unloading. This could be due to two reasons. This may be due to the reduced thickness of Teflon coating, allows an increased wire dimension underneath the coating in RMO archwires. The other reason may be RMO wires were coated only on labial side which further decreases the coating and increases the wire dimensions which further decreases the coating thickness and increases the wire dimension which was also in agreement with the study done by da Silva et al.[9]

Results showed that loading and unloading forces were more in as-received wires compared to retrieved wires which are also in agreement with the study conducted by Elayyan et al.[6] This could be due to increased frictional forces between the irregular surface of the coating and brackets, and the forces of mastication may also lead to permanent wire deformation. The increased irregular surface and friction might result in binding of the archwire during testing. Results of this study also suggest that superelastic property of coated Ni–Ti wires was lost significantly after 1 month. Hence, these wires cannot be used for more than 1 month.

In all the three company wires, roughness values increased significantly after clinical use. Abrasive effect of tooth brushing, food consistency, and interaction between the arch wire coating and bracket edges may be the reason for this increase in roughness.[10],[11]


  Conclusion Top


  • In the as received wires there were no significant differences in surface roughness.
  • In all the three companies surface roughness increased in retrieved wires compared to as received wires.
  • In the retrieved wires the epoxy coated (G&H) showed more roughness compared to Teflon coated (AO and RMO).
  • In the as received wires epoxy coated (G&H) wires showed lowest forces compared to Teflon coated (AO and RMO). but with no statistically significant difference.
  • In the retrieved wires epoxy coated (G&H) wires showed lowest forces compared to Teflon coated (AO and RMO).
  • In all the three companies forces decreased in retrieved wires compared to as received wires.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Husmann P, Bourauel C, Wessinger M, Jäger A. The frictional behavior of coated guiding archwires. J Orofac Orthop 2002;63:199-211.  Back to cited text no. 1
    
2.
Krishnan V, Kumar KJ. Mechanical properties and surface characteristics of three archwire alloys. Angle Orthod 2004;74:825-31.  Back to cited text no. 2
    
3.
Kapila S, Sachdeva R. Mechanical properties and clinical applications of orthodontic wires. Am J Orthod Dentofacial Orthop 1989;96:100-9.  Back to cited text no. 3
    
4.
Bourauel C, Fries T, Drescher D, Plietsch R. Surface roughness of orthodontic wires via atomic force microscopy, laser specular reflectance, and profilometry. Eur J Orthod 1998;20:79-92.  Back to cited text no. 4
    
5.
Eliades T, Eliades G, Athanasiou AE, Bradley TG. Surface characterization of retrieved NiTi orthodontic archwires. Eur J Orthod 2000;22:317-26.  Back to cited text no. 5
    
6.
Elayyan F, Silikas N, Bearn D. Ex vivo surface and mechanical properties of coated orthodontic archwires. Eur J Orthod 2008;30:661-7.  Back to cited text no. 6
    
7.
Haryani J, Ranabhatt R. Contemporary esthetic orthodontic archwires – A review. Dent Mater Tech 2016;5:125-30.  Back to cited text no. 7
    
8.
Alavi S, Hosseini N. Load-deflection and surface properties of coated and conventional superelastic orthodontic archwires in conventional and metal-insert ceramic brackets. Dent Res J (Isfahan) 2012;9:133-8.  Back to cited text no. 8
    
9.
da Silva DL, Mattos CT, Anna EF, de Oliveira Ruellas AC, Eliasd CN. Cross section dimensions and mechanical properties of esthetic orthodontic coated archwire. Am J Orthod Dentofacial Orthop 2013;143:S85-91.  Back to cited text no. 9
    
10.
Rongo R, Ametrano G, Gloria A, Spagnuolo G, Galeotti A, Paduano S, et al. Effects of intraoral aging on surface properties of coated nickel-titanium archwires. Angle Orthod 2014;84:665-72.  Back to cited text no. 10
    
11.
Wichelhaus A, Geserick M, Hibst R, Sander FG. The effect of surface treatment and clinical use on friction in NiTi orthodontic wires. Dent Mater 2005;21:938-45.  Back to cited text no. 11
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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