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.

BACKGROUND AND AIM: 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. MATERIALS AND METHODS: 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). RESULTS: 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. CONCLUSION: 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.

Effect of esthetic coating on surface roughness of orthodontic archwires.

BACKGROUND AND AIM: Esthetic wires are commonly used in orthodontic treatments. Surface roughness is an important factor in the friction and bacterial adhesion in these wires. Surface roughness of esthetic wires has not been assessed, except in a few recent (mostly qualitative esthetics) studies. The aim of this study was to quantitatively compare the surface roughness of 4 coated esthetic wires with that of a conventional orthodontic wire. MATERIALS AND METHODS: In this in vitro trial, 25 coated and uncoated orthodontic archwires were studied, including: NiTi Memory wire (American Orthodontics, USA) as a control group; Orthocosmetic Elastinol (Ortho Organizers, USA); Perfect (Hubit, Korea); Imagination (Gestenco, Sweden); EverWhite (American Orthodontics, USA). All were .016×.022" rectangular maxillary wires. Fifteen millimeters of wire was cut off at the posterior end and a surface area of 2000×2000nm was probed using a Scanning Probe Microscope (DS95-50E/DME, Denmark) to determine the surface roughness values. The roughness parameters of Sa, Sdq, Sv and Sy were measured and statistically compared by Kruskal-Wallis and Mann-Whitney U tests. RESULTS: The average range of the 4 parameters was the highest for the uncoated Ni-Ti Memory wire (control group) while the Perfect coated wire showed the lowest values. The differences were significant for parameters Sa and Sy (P<0.02 and P<0.023) and non-significant for Sv and Sdq. Significant differences existed between uncoated and coated wires regarding Sa and Sy values (P<0.01), being higher for the uncoated wires. CONCLUSION: Taking into account the study limitations, the surface roughness values of NiTi uncoated archwires were significantly higher than those of the coated wires.

Effect of Deep Cryogenic Treatment on Cyclic Fatigue of Endodontic Rotary Nickel Titanium Instruments.

INTRODUCTION: Cyclic fatigue is the common reason for breakage of rotary instruments. This study was conducted to evaluate the effect of cryogenic treatment (CT) in improving the resistance to cyclic fatigue of endodontic rotary instruments. METHODS AND MATERIALS: In this in vitro study, 20 RaCe and 20 Mtwo files were randomly divided into two groups of negative control and CT. CT files were stored in liquid nitrogen at -196°C for 24 h, and then were gradually warmed to the room temperature. All files were used (at torques and speeds recommended by their manufacturers) in a simulated canal with a 45° curvature until breakage. The time to fail (TF) was recorded and used to calculate the number of cycle to fail (NCF). Groups were compared using independent-samples t-test. RESULTS: Mean NCFs were 1248.2±68.1, 1281.6±78.6, 4126.0±179.2, and 4175.4±190.1 cycles, for the Mtwo-control, Mtwo-CT, RaCe-control, and RaCe-CT, respectively. The difference between the controls and their respective CT groups were not significant (P>0.3). The difference between the systems was significant. CONCLUSION: Deep CT did not improve resistance to cyclic fatigue of the evaluated rotary files.