Effects of surface roughness on the coefficients of friction in model orthodontic systems

doi:10.1016/0021-9290(90)90356-8

Journal of Biomechanics

Volume 23, Issue 9, 1990, Pages 913-925

https://doi.org/10.1016/0021-9290(90)90356-8 Get rights and content

Abstract

Orthodontists, like others (Engel, P. A. (1976) Impact Wear of Materials. Elsevier Scientific, New York.), often equate the smoothness of surfaces with the absence of friction. To investigate whether the surface roughnesses of opposing materials influence the coefficients of friction and ultimately the movement of teeth, arch wires were slid between contact flats to simulate orthodontic arch wire-bracket appliances. From laser specular reflectance measurements, the RMS surface roughnesses of these arch wires varied from 0.04 μm for stainless steel to 0.23 μm for nickel titanium. Using the same technique, the roughnesses of the contact flats varied from 0.03 μm for the 1 μm lapped stainless steel, to 0.26 μm for the as-received alumina. After each of the arch wire-contact flat couples was placed in a friction tester, fifteen normal forces were systematically applied at 34°C. From plots of the static and kinetic frictional forces vs the normal forces, dry coefficients of friction were obtained that were greater than those reported in the dental literature. The allstainless steel couples had lower kinetic coefficients (0.120–0.148) than the stainless steel-polycrystalline alumina couple (0.187). When pressed against the various flats, the beta-titanium arch wire (RMS = 0.14 μm) had the highest coefficients of friction (0.445–0.658), although the nickel titanium arch wire was the roughest (RMS = 0.23 μm). Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) verified that mass transfer of the beta-titanium arch wire occurred by adhesion onto the stainless steel flats or by abrasion from the sharply faceted polycrystalline alumina flats.

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Cited by (108)

Roughness and humidity effects on contact, friction, and contact plasticity revealed by micromechanical testing and analysis
2023, Tribology International
Understanding the effects of surface roughness, surface lubrication, and environmental conditions on inter-particle contact mechanics is important for a broad range of applications of granular materials. In this paper, a new micromechanical testing apparatus was developed and used to characterize smooth and rough soda lime glass particles in carefully controlled dry, humid, and lubricated environments during normal compression and shearing. From surface profilometry measurements and digital image correlation, we observed a humidity independent correlation between hysteresis, contact plasticity, and surface roughness in normal compression tests. From analysis of shear test data, we observed an increase in friction with increasing surface roughness, contact hold times, and water lubrication. Our work highlights roughness and environmental effects on contact and friction of silicate materials.
A matter of morphology: The role of asperity characteristics in hydrogel friction
2022, Tribology International
Citation Excerpt :
There are several advantages relevant to biomimetic applications when using hydrogels: Hydrogels are biocompatible and biodegradable and their viscoelastic properties as well as their surface properties can be readily modified. The challenge in studying hydrogel friction is that hydrogels often do not follow classic frictional laws, such as Amontons-Coulombs laws, that dictate that the friction coefficient is unaffected by changes in the contact area. [6,7–13] Instead, most hydrogels do provide contact area-dependent frictional behavior.
Hydrogels can be easily modified to have a particular surface roughness. This modularity in hydrogels is an important feature, as roughness affects friction. Here, we systematically vary the surface morphology by separately altering the height, diameter and distance between surface asperities shaped as cylindrical pillars. Using a custom- made 3D-printed tribometer, we show that slender pillars conjure a higher friction coefficient, which we attribute to their bending and hence larger exposed contact area. In contrast, we measure low friction coefficients when the small diameter of asperities or their sparse presence on the surfaces reduces the total effective sliding contact area. We investigate two surface patterns with different spatial symmetry and demonstrate that the mechanisms behind probe-pillar friction depend on the spatial location of the pillars on the surface with respect to the sliding path. Our findings provide a path towards optimization of frictional properties of soft hydrogel surfaces.
The use of attachments in aligner treatment: Analyzing the “innovation” of expanding the use of acid etching–mediated bonding of composites to enamel and its consequences
2020, American Journal of Orthodontics and Dentofacial Orthopedics
Orthodontic treatment with sequential aligners has seen a considerable surge in the last decades, and is currently used to treat malocclusions of varying severity. To enhance tooth movement and broaden the spectrum of malocclusions that can be treated with aligners, composite resin attachments are routinely bonded with the acid-etch technique on multiple teeth, a process known to impose irreversible alterations of the enamel structure, color, gloss, and roughness. Additionally, this clinical setting introduces a unique scenario of different materials applied in a manner that involves the development of friction and attrition between the attachment and the softer aligner material, all performing in the harsh conditions of the oral environment, which impact the aging of these materials. The latter may give rise to alterations of the aligners and the composite attachments and potential intraoral release of Bisphenol A, a known endocrine disrupting agent. Furthermore, at the final stages of contemporary aligner treatment, the removal of multiple, sometimes bulky, composite attachments with a volume and surface far greater than the remnant adhesive after debonding of brackets, through grinding that might be associated with pulmonary effects for the patient or staff. Because of the extensive enamel involvement in bonding, the release of factors from the attachment-aligner complex during service, the aging of these entities in the oral environment, and the laborious debonding/composite grinding process coupled with the hazardous nature of aerosol produced during the removal of these bulky specimens, appropriate risk management considerations should be applied and an effort to confine the application of multiple composite specimens bonded to enamel to the absolutely necessary should be pursued.
Surface topography of plain nickel-titanium (NiTi), as-received aesthetic (coated) NiTi, and aesthetic NiTi archwires sterilized by autoclaving or glutaraldehyde immersion: A profilometry/SEM/AFM study
2019, International Orthodontics
Citation Excerpt :
Therefore, attempts have been made to manufacture aesthetic brackets or archwires from tooth-coloured materials or coating metal archwires with materials such as epoxy resin Teflon [3–7]. Aesthetic archwires might also reduce plaque accumulation and improve sliding mechanics by reducing the frictional force compared to uncoated wires, while removal of the coating film might reduce the aesthetics and increase the friction [3–5,7–12]. Although the coating material is usually inert and bonded with strong adhesives to the underlying metal [12,13], it can be peeled off due to various mechanical/thermal/chemical disturbances.
Surface topography is a crucial factor in bracket sliding mechanics. Literature on surface roughness of aesthetic archwires is scarce, and there is no study on surface topography of such archwires affected by any sterilization methods. The aim of this study was to compare the surface topography of plain nickel-titanium (NiTi) versus as-received aesthetic coated NiTi wires versus aesthetic wires sterilized by autoclaving or glutaraldehyde immersion.
This in vitro study was performed on 80 atomic force microscopy (AFM) observations, 160 profilometry observations, and 40 scanning electron microscopy (SEM) images from rectangular wires of the brands ‘American Orthodontics, Ortho Organizers, SIA, and Gestenco’. AFM consisted of 8 subgroups of NiTi orthodontic wires, consisting of 4 subgroups of 4 brands of coated orthodontic wires and 4 subgroups of 4 brands of uncoated wires from the same brands. Profilometry consisted of 16 subgroups of NiTi orthodontic wires, consisting of 4 subgroups of 4 brands of coated orthodontic wires and 12 subgroups of 4 brands of uncoated wires from the same brands (4 as-received wire subgroups, 4 autoclaved, and 4 cold-sterilized subgroups). Scanning electron microscopy (SEM) and AFM images were subjectively evaluated. AFM and profilometry data were analysed statistically (α = 0.05).
Overall, the difference between surface roughness parameters of coated versus uncoated archwires was not significant (P > 0.05). However, surface roughness of brands differed significantly. Mann-Whitney did not show any significant differences between sterilized wires (both sterilization methods together as one group) and unsterilized wires (both unsterilized coated and uncoated as one group) (P > 0.460). After excluding plain uncoated NiTi group, the coated wires in 3 sterilization groups (no sterilization, autoclaving, glutaraldehyde) were not significantly different in terms of average overall surface roughness (Ra) and maximum roughness depths (Rq) of different sterilization groups (P > 0.1) but the average maximum peak to valley heights (Rz) values of 3 sterilization groups were significantly different (P = 0.0415). Dunn test showed that among three post-hoc pairwise comparisons of Rz values, only the comparison of “no sterilization versus autoclaving” was significant (P < 0.05) and the other two were non-significant.
Coating might not affect the surface roughness considerably. Brands have different surface roughnesses. Autoclaving but not cold sterilization might affect the surface roughness of coated archwires.
La topographie de surface est un facteur crucial dans la mécanique de glissement des attaches. La littérature sur la rugosité de surface des fils orthodontiques esthétiques est rare, et il n’existe aucune étude sur la topographie de surface de ce type de fils lorsqu’ils ont subi différentes méthodes de stérilisation. Le but de cette étude était de comparer la topographie de surface des fils orthodontiques ordinaires en nickel-titane (NiTi) à celle des fils en NiTi esthétique à l’état initial et après stérilisation à l’autoclave ou par immersion dans le glutaraldéhyde.
Cette étude in vitro a été réalisée sur 80 observations au microscope à force atomique (AFM), 160 observations au profilomètre et 40 images au microscope électronique à balayage (SEM) de fils rectangulaires de 4 marques « American Orthodontics, Ortho Organizers, SIA, et Gestenco ». L’AFM a concerné 8 sous-groupes de fils orthodontiques NiTi : quatre avec revêtement et quatre sans revêtement ; chaque sous-groupe présentait des fils des 4 mêmes marques. La profilométrie a concerné 16 sous-groupes de fils orthodontiques NiTi : quatre avec revêtement et 12 sans revêtement (4 sous-groupes de fils à l’état initial, 4 sous-groupes stérilisés à l’autoclave et 4 sous-groupes stérilisés à froid) ; chaque sous-groupe présentait la même représentation des 4 marques. Les images au microscope électronique à balayage (SEM) et les images AFM ont été évaluées subjectivement. Les données d’AFM et de profilométrie ont été analysées statistiquement (α = 0,05).
Dans l’ensemble, la différence entre les paramètres de rugosité de surface des fils orthodontiques avec revêtement et sans revêtement ne présentait pas de différence significative (p > 0,05). Cependant, les rugosités de surface des marques ont été sensiblement différentes. Le test de Mann-Whitney n’a pas montré de différences significatives entre les fils stérilisés (les deux méthodes de stérilisation ont été réunies en un seul groupe) et les fils non stérilisés (les deux groupes de fils non stérilisés avec revêtement et sans revêtement ont été réunis en un groupe) (p > 0,460). Après exclusion des fils NiTi ordinaires sans revêtement, les fils avec revêtement répartis en 3 groupes de stérilisation (sans stérilisation, avec stérilisation à l’autoclave et à froid avec glutaraldéhyde) n’ont pas été significativement différents en termes de rugosité globale moyenne (Ra) et de profondeur maximale (Rq) (p > 0,1). Par contre, les moyennes de hauteur pic-vallée maximale (Rz) des 3 groupes de stérilisation (p = 0,0415) ont été significativement différentes. Le test de Dunn a montré que parmi trois comparaisons post-hoc par paires des valeurs Rz, seule la comparaison entre « sans stérilisation et stérilisation à l’autoclave » a été significative (p < 0,05) et les deux autres n’ont pas été significatives.
Le revêtement pourrait ne pas avoir une incidence considérable sur la rugosité de surface. Les marques ont des rugosités de surface différentes. La stérilisation à l’autoclave aurait une incidence sur la rugosité de surface des fils orthodontiques avec revêtement, ce qui ne serait pas le cas de la stérilisation à froid.
Nanotechnology in orthodontics-1: The past, present, and a perspective of the future
2019, Nanobiomaterials in Clinical Dentistry
Nanotechnology continues to influence new developments within numerous engineering and medical disciplines and its adaptation into the future advancements of orthodontics has already begun. For example, nanoindentation studies with atomic force microscope are being utilized to effectively image and analyze the surface properties and changes taking place on orthodontic wires and brackets during treatment at the nanoscale dimension. Nanoparticle coatings on orthodontic archwires have been evaluated to reduce friction and, if further developed, could influence the speed and/or efficiency of tooth movement. In other research, orthodontic adhesives with nanoparticles have been shown to have improved material characteristics over the conventional adhesives. While some initial studies have evaluated the use of fluoride delivery via orthodontic elastomeric ligatures, additional studies on nanoparticle delivery of anticariogenic, antiinflammatory, and antimicrobial medicaments using orthodontic elastomeric ligatures could provide valuable innovations in the field of orthodontics. This chapter discusses recent studies over the past decade on applications of nanoparticles, nanoscale imaging techniques, and their applications in orthodontics. Future directions on research about shape-memory polymers for orthodontic wires, biological microelectromechanical systems/nanoelectromechanical systems, temporary anchorage devices, and nanorobots for orthodontic applications are discussed.
The effect of food simulating liquids on the static frictional forces and corrosion activity of different types of orthodontic wires
2017, Journal of the World Federation of Orthodontists
The purpose of this study was to investigate the effect of some food stimulating liquids (FSLs) on the static frictional forces and corrosion activity of different orthodontic archwire materials.
Stainless steel (SS), β-titanium (TMA), and nickel titanium (NiTi) archwires were stored in heptane, citric acid, and ethanol each. Every storage combination group consisted of 12 wires. The static frictional forces between the SS brackets and each of the three types of orthodontic wires were measured as received, after 2 weeks and after 4 weeks storage in each FSL. The corrosion activity of the wires in citric acid and ethanol were measured.
For SS wires, citric acid and ethanol 4-week storage showed the highest statistically significant static friction values. For the TMA and NiTi wires, 4-week storage in citric acid showed higher statistically significant static friction values compared with no storage. Citric acid showed the highest corrosion activity for the three types of orthodontic wires. SS showed the highest corrosion activity in both citric acid and ethanol.
Four-week storage in citric acid had the highest deleterious effect, as it significantly increased the static frictional force values of SS, TMA, and NiTi archwires. SS has the highest corrosion activity and thus its frictional force values are affected by 4-week storage in both citric acid and ethanol.

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^†: Present address: Bldg 210-H, Room 313, University of North Carolina, Chapel Hill, NC 27599-7455, U.S.A.

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Journal of Biomechanics

Abstract

References (32)

Evaluation of friction forces in the 0.022″ × 0.028″ edgewise bracket in vitro

J. Biomechanics

Effects of cold disinfectants on the mechanical properties and the surface topography of nickel-titanium arch wires

Am. J. orthod. dent. Orthop.

The segmental arch approach to space closure

Am. J. Orthod.

A comparative study of frictional resistances between orthodontic bracket and arch wire

Am. J. Orthod.

A comparison of frictional forces during simulated canine retraction of a continuous edgewise arch wire

Am. J. orthod. dent. Orthop

Polishing porcelain veneers: an SEM and specular reflectance analysis

Dent. Mater.

Surface roughness of a dental amalgam via a laser scattering test

Dent. Mater.

Coefficient of friction of prosthetic tooth materials

J. prosth. Dent.

Effects of sterilization on the mechanical properties and the surface topography of nickel-titanium arch wires

Am. J. orthod. dent. Orthop.

Comparative friction of orthodontic wires under dry and wet conditions

Am. J. Orthod.

The use of laser light in the study of metal surfaces

Opt. Laser Technol.

A comparison between Tallysurf 10 and optical measurements of roughness and surface slope

Wear

A study of the surface parameters of ground and lapped metal surfaces using specular and diffuse reflection of laser light

Wear

Surface roughness of stainless steel and electro-formed nickel standards using a HeNe laser

Opt. Laser Technol.

Cited by (108)

Roughness and humidity effects on contact, friction, and contact plasticity revealed by micromechanical testing and analysis

A matter of morphology: The role of asperity characteristics in hydrogel friction

The use of attachments in aligner treatment: Analyzing the “innovation” of expanding the use of acid etching–mediated bonding of composites to enamel and its consequences

Surface topography of plain nickel-titanium (NiTi), as-received aesthetic (coated) NiTi, and aesthetic NiTi archwires sterilized by autoclaving or glutaraldehyde immersion: A profilometry/SEM/AFM study

Nanotechnology in orthodontics-1: The past, present, and a perspective of the future

The effect of food simulating liquids on the static frictional forces and corrosion activity of different types of orthodontic wires