Characterization and coating stability evaluation of nickel-titanium orthodontic esthetic wires: an in vivo study

Abstract

The objective of this study was to compare coating dimensions and surface characteristics of two different esthetic covered nickel-titanium orthodontic rectangular archwires, as-received from the manufacturer and after oral exposure. The study was designed for comparative purposes. Both archwires, as-received from the manufacturer, were observed using a stereomicroscope to measure coating thickness and inner metallic dimensions. The wires were also exposed to oral environment in 11 orthodontic active patients for 21 days. After removing the samples, stereomicroscopy images were captured, coating loss was measured and its percentage was calculated. Three segments of each wire (one as-received and two after oral exposure) were observed using scanning electron microscopy for a qualitative analysis of the labial surface of the wires. The Lilliefors test and independent t-test were applied to verify normality of data and statistical differences between wires, respectively. The significance level adopted was 0.05. The results showed that the differences between the wires while comparing inner height and thickness were statistically significant (p < 0.0001). In average, the most recently launched wire presented a coating thickness twice that of the control wire, which was also a statistically significant difference. The coating loss percentage was also statistically different (p = 0.0346) when the latest launched wire (13.27%) was compared to the control (29.63%). In conclusion, the coating of the most recent wire was thicker and more uniform, whereas the control had a thinner coating on the edges. After oral exposure, both tested wires presented coating loss, but the most recently launched wire exhibited better results.

Effects of salivary pH on coating durability of two different aesthetic archwire coatings under a simulated intraoral environment

“…An electrochemical characteristic study of PTFE coated NiTi orthodontic wires also supported the finding that the PTFE coated archwires, which were immersed in artificial saliva under a low pH (pH 4), demonstrated lower corrosion rates and passive current densities than uncoated NiTi substrates because of electrolyte penetration in the pore of the PTFE deposits ( Mareci et al, 2015 ). However, this is inconsistent with a previous study that reported that the PTFE coating had poor stability due to thinner coating layer of the as-received PTFE coated aesthetic archwires than what was reported by the manufacturer ( Argalji et al, 2017 ). Another study also reported that PTFE coated archwires showed the highest surface roughness after 28 days of immersion in artificial saliva with pH 6.75 when compared to epoxy resin ( Muayad and Ghaib, 2017 ).…”

“…Clinically, commercially-available coated archwires have demonstrated partial or full coating loss after as few as 21 to 28 days of intraoral exposure ( Argalji et al, 2017 , Ulhaq et al, 2017 ). These losses are noticeable and leave patients feeling dissatisfied ( Bradley et al, 2013 ).…”

Evaluation of nanomechanical properties, surface roughness, and color stability of esthetic nickel-titanium orthodontic archwires

“…Since then many researchers have studied the esthetic archwires evaluating the clinical performance in vivo and in vitro . [21019202122]…”

“…Archwires with uniformly thicker coatings demonstrated better properties than the thinner coated archwires. [10]…”

Attractiveness of different esthetic orthodontic wires

“…In recent years, esthetic brackets and wires have been widely studied, tested and compared in terms of their coefficient of friction, 16 surface roughness, 17 , 18 mechanical properties 17 and esthetic stability during treatment. 12 , 18 , 19 Their advantages and disadvantages have already been described in numerous studies in the literature. 7 , 12 - 14 , 17 Recently, Pinzan-Vercelino et al 21 performed a cross-sectional study to evaluate laypersons’ esthetic perceptions of metal archwires with and without esthetic coating and found that the epoxy resin wire was the most esthetic.…”