A Longitudinal SEM Analysis of Surface Degradation and Microstructural Fatigue in Superelastic NiTi Archwires: A 40-Day Clinical Study
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Abstract
Objectives: This study aimed to evaluate the surface degradation of superelastic Nickel-Titanium (NiTi) orthodontic archwires over 10, 30, and 40-day periods of intraoral exposure using Scanning Electron Microscopy (SEM).
Materials and Methods: Forty maxillary NiTi archwires (0.016-inch) were divided into four groups: as-received (control), and three groups retrieved from patients after 10, 30, and 40 days of clinical use. Following ultrasonic cleaning in ethanol, the wires were analyzed using SEM at magnifications up to x2000. Surface features were qualitatively described and quantitatively assessed using a standardized degradation scoring system (0–4).
Results: Control wires showed typical manufacturing striations with minimal defects (Mean Score: 0.42). By day 10, localized pitting was evident (Mean Score: 1.25). Day 30 samples exhibited significant fatigue, characterized by the coalescence of pits and the initiation of surface delamination (Mean Score: 2.68). At 40 days, severe topographical breakdown was observed, including widespread flaking and deep corrosive craters, particularly in the molar regions (Mean Score: 3.55).
Conclusion: Intraoral exposure leads to rapid and progressive surface degradation of NiTi archwires. The integrity of the wire surface is significantly compromised within 30 to 40 days, which may increase friction and affect the efficiency of orthodontic alignment.
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References
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