Application of a Molybdenum and Tungsten Disulfide Coating to Improve Tribological Properties of Orthodontic Archwires
Abstract
:1. Introduction
2. Materials and Methods
2.1. Nanoparticles
2.2. Bracket
- 40 In-Ovation (Dentsply Sirona, New York, US) upper right central incisors bracket (tq 12°, tip 5°).
- 40 Damon Q (Ormco, 200 S. Kraemer Blvd., Building E Brea, California 92821) upper right central incisors bracket (tq 15°, tip 5°).
2.3. Artificial Saliva
2.4. Coatings’ Deposition on Orthodontic Wires
- Mechanical abrasion with abrasive paper of silicon carbide (500 grains/unit area), to clean orthodontic wires.
- Solvent degreasing with acetone in an ultrasonic cleaner for 2 min, to remove organic residues and dust of abrasive paper.
- Rinsing with deionized water and drying.
- Positioning of orthodontic wires on a special frame, with the aim of being able to handle more easily without leaving traces on the substrates to be coated.
- Immersion of the frame with the wires in sulfuric acid at 0.5 M with cathodic polarization to −1 V.
- Rinsing with deionized water.
- GROUP 1: control group; wires of this group were not applied any coating.
- GROUP 2: wires of this group were coated with a Ni film by electrochemical co-deposition.
- GROUP 3: wires of this group were coated with a Ni + MoS2 film by electrochemical co-deposition.
- GROUP 4: wires of this group were coated with a Ni + WS2 film by electrochemical co-deposition.
- GROUP 2: wires were inserted in a Watts bath, with a direct current of 0.04 A and starting the process of electrochemical co-deposition for 25 min.
- GROUP 3: wires were inserted in a Watts bath in which 2 g/L of MoS2 NP was dispersed; since MoS2 NP are hardly wettable, a cationic surfactant (CTAB cetyl trimethyl aminobromide) was added to the bath (0.4 gr/L of CTAB). To minimize agglomeration of MoS2 NP, the bath was maintained in constant agitation with the use of a mechanical stirrer (activated 12 h before the deposition and during the entire deposition step) and ultrasound treatment. Electrochemical co-deposition was processed for 25 min with a direct current of 0.04 A.
- GROUP 4: wires were inserted in a Watts bath in which 2 g/L of WS2 NP was dispersed; since WS2 NP are hardly wettable, a cationic surfactant (CTAB cetyl trimethyl aminobromide) was added to the bath (0.2 gr of CTAB). To minimize agglomeration of WS2 NP, the bath was maintained in constant agitation with the use of a mechanical stirrer (activated 12 h before the deposition and during the entire deposition step) and ultrasound treatment. Electrochemical co-deposition was processed for 25 min with a direct current of 0.04 A.
2.5. Analysis of Coated Orthodontic Wires
2.6. Friction Measurements of the Wires
2.7. Data Analysis
2.8. Analysis of Coated and Uncoated Orthodontic Wires after Friction Test
3. Results
3.1. Analysis of Coated Orthodontic Wires
3.2. Friction Measurements of the Wires
3.2.1. “Dry” Conditions
- No significant differences were found between Ni + MoS2 and Ni + WS2 films even if, from a descriptive point of view, wires coated with Ni + MoS2 show lower friction values;
- Wires coated with Ni + MoS2 and Ni + WS2 films have friction values significantly lower than wires coated with Ni;
- If paired to the In-Ovation bracket, SS uncoated wires differ from all others, both from wires coated with Ni (whose friction coefficient is greater) and wires coated with Ni + MoS2 and Ni + WS2 (whose friction coefficients are lower);
- If paired to the Damon Q bracket, SS uncoated wires have lower friction coefficient only for wires coated with Ni, while they do not significantly differ from wires coated with Ni + MoS2 and Ni + WS2.
3.2.2. “Wet” Conditions
- Comparing Ni + MoS2 and Ni + WS2, from a descriptive point of view, wires coated with Ni + MoS2 always show lower friction values. Tukey’s test results state that Ni + MoS2 presents a lower friction coefficient for both Damon 0° and In-Ovation 5°.
- Wires coated with Ni + MoS2 and Ni + WS2 films have friction values significantly lower than wires coated with Ni except for Damon 5°.
- If paired to the In-Ovation bracket, SS uncoated wires differ from wires coated with Ni + MoS2 (whose friction coefficient is lower).
- If paired to the Damon Q bracket, SS uncoated significantly differ from wires coated with Ni + MoS2 and Ni + WS2 (whose friction coefficients are lower) only for angulation of 5°.
3.3. Analysis of Coated and Uncoated Orthodontic Wires after Friction Test
4. Discussion
- Films’ adhesion was homogeneous, with few uncoated areas.
- The coatings’ thickness was contained within values that would allow the insertion of the wires into the slot and the sliding along the bracket.
5. Conclusions
Author Contributions
Funding
Conflicts of Interest
References
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MoS2 | WS2 | |
---|---|---|
Purity | 99.90% | 99.90% |
Color | Black | Black |
Morphology | Spherical | Spherical |
APS | 80–100 nm | 40–80 nm |
Density | 5.06 g/cm3 | ND |
Melting Point | 1185 °C | ND |
Synthesis | MOCVD | MOCVD |
SS | SS + Ni | SS + Ni + MoS2 | SS + Ni + WS2 | |
---|---|---|---|---|
Damon Q/0° | 0.58(0.12) | 3.22(0.92) | 0.42(0.08) | 0.50(0.08) |
Damon Q/5° | 1.27(0.18) | 9.25(4.01) | 0.94(0.11) | 1.19(0.14) |
In-Ovation/0° | 1.24(0.12) | 3.35(0.57) | 0.64(0.06) | 0.79(0.06) |
In-Ovation/5° | 1.43(0.06) | 7.96(0.59) | 1.06(0.07) | 1.06(0.13) |
SS | SS + Ni | SS + Ni + MoS2 | SS + Ni + WS2 | |
---|---|---|---|---|
Damon Q/0° | 0.95(0.09) | 1.01(0.07) | 0.66(0.13) | 0.94(0.07) |
Damon Q/5° | 1.87(0.10) | 1.33(0.10) | 1.16(0.07) | 1.27(0.18) |
In-Ovation/0° | 1.45(0.17) | 1.75(0.11) | 0.91(0.19) | 1.13(0.16) |
In-Ovation/5° | 2.52(0.09) | 4.06(0.45) | 1.46(0.13) | 2.35(0.19) |
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Gracco, A.; Dandrea, M.; Deflorian, F.; Zanella, C.; De Stefani, A.; Bruno, G.; Stellini, E. Application of a Molybdenum and Tungsten Disulfide Coating to Improve Tribological Properties of Orthodontic Archwires. Nanomaterials 2019, 9, 753. https://doi.org/10.3390/nano9050753
Gracco A, Dandrea M, Deflorian F, Zanella C, De Stefani A, Bruno G, Stellini E. Application of a Molybdenum and Tungsten Disulfide Coating to Improve Tribological Properties of Orthodontic Archwires. Nanomaterials. 2019; 9(5):753. https://doi.org/10.3390/nano9050753
Chicago/Turabian StyleGracco, Antonio, Martina Dandrea, Flavio Deflorian, Caterina Zanella, Alberto De Stefani, Giovanni Bruno, and Edoardo Stellini. 2019. "Application of a Molybdenum and Tungsten Disulfide Coating to Improve Tribological Properties of Orthodontic Archwires" Nanomaterials 9, no. 5: 753. https://doi.org/10.3390/nano9050753