# Cytotoxicity of Orthodontic Archives Used in Clinical Practice: In Vitro Study
###### Abstract
This alloy, which can be modified by heat treatment to become malleable and subsequently hard and resilient, has found specific applications in orthodontic, such as palatal transpositions, despite a decline in popularity due to the emergence of newer alloys [2]. Material science advancements have introduced Elgiloy among various alloys crafted for orthodontic wires. Favored by orthodontists, especially in its blue form for its formability and heat treatment-enhanced durability, Elgiloy faces challenges in clinical use \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Archwire** & **Strength** & **Elasticity** & **Bending** & **Joining** & **Friction** & **Biocompatibility** \\ \hline Steel & High & Low & + & + & Lower & +/\(-\) \\ \hline Elgiloy & High & Low & + & + & Lower & +/\(-\) \\ \hline TMA & Medium & Medium & + & + & Higher & + \\ \hline NiTi & Low & High & \(-\) & \(-\) & Higher & +/\(-\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Features of selected orthodontic archives. \begin{table}
\begin{tabular}{c c} \hline \hline
**Type of Alloy** & **Composition** \\ \hline Stainless steel (SS) & 17–20\% Cr, 8–12\% Ni, 0.15\% C balanced with Fe \\ \hline Chromium–cobalt steel (CrCo) & 40\% CO, 20\% Cr, 15\% Ni, 15.8\% Fe, 7\% Mo, 2\% Mn, \\ Elgiloy & 0.15\% C, 0.04\% Be \\ \hline Titanium–molybdenum (TMA) & 77.8\% Ti, 11.3\% Mo, 6.6\% Zr, 4.3\% Sn \\ \hline Nickel–titanium (NiTi) & 55\% Ni, 45\% Ti, (trace amounts Cu) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Percent composition of different types of orthodontic alloys. due to its increased deformation after loading, as revealed by three-point bending tests. This deformation might limit its application, yet Elgiloy's mechanical properties remain consistent across manufacturers. Compared to stainless steel (SS) and titanium-molybdenum alloy (TMA), Elgiloy demonstrates force levels similar to those of SS at lower loadings but shows a decrease at higher loadings. Despite its beneficial flexibility, the tendency of the alloy to deform poses potential challenges in orthodontic practice [6]. Nickel-Titanium Alloy (NiTi): Originating in the 1960s in the United States, the nickel-titanium alloy (NiTi) was introduced to the field of orthodontics by [PERSON]. This alloy is known for its remarkable elasticity, resistance to corrosion, and the ability to recall its shape. Such features enable it to be flexible at cooler temperatures and revert to its initial form when warmed. To tailor its characteristics specifically for orthodontic use, this group of materials has undergone a series of refinements [2,7]. NiTi wires exhibit notable shifts in mechanical behavior and the force they apply in response to temperature variations, which are applicable to both conventional and thermally activated wires. Although exposure to high temperatures may cause irreversible deformation, any temporary strain experienced at cooler temperatures can be reversed as warmth is reintroduced [8]. Allergic reactions, particularly to nickel, are a significant concern in orthodontics due to the widespread use of nickel-containing alloys in braces and other appliances. Nickel allergy, which affects up to 30% of women and 3% of men, can cause various oral and dermal symptoms in orthodontic patients. Although the risk of developing nickel sensitivity from orthodontic treatment is low, a history of exposure to nickel, such as through ear piercing, can increase susceptibility. In general, with adverse reactions in orthodontic practices estimated at 0.3-0.4%, understanding and managing potential allergies is crucial to safe and effective treatment [9]. The aim of this study was to evaluate the biocompatibility of selected orthodontic archives. To achieve this overarching goal, specific objectives were set, including the assessment of the surface structure of the archives using SEM, and the evaluation of cytotoxicity through proliferation tests and cell viability assessments.