Aesthetic orthodontic archwires: Progress in their knowledge

Introduction: In orthodontics, is quickly increasing the demand for treatments with a very low aesthetic impact in the social life. More and more adult patients want satisfy their necessity to have a beautiful smile, with †œinvisible†� appliances. Numerous are the opportunities to perform an aesthetic orthodontic treatment such as lingual orthodontics, clear aligners or clear labial orthodontics. Aesthetic orthodontic archwires are a component of clear labial orthodontics together with aesthetic brackets, but unlike the latter, they have not been extensively studied in literature. Hence the aim of this thesis was to understand more the physical and mechanical properties of the aesthetic orthodontic archwires. Materials and Methods: a literature review was done to collect information on this field. By means of an Atomic Force Microscope (AFM), the surface roughness of 8 aesthetic and metallic orthodontic archwires was assessed to verify the effect of the surface treatments on the wires' roughness. Four nickel-titanium (NiTi) wires (Sentalloy, Sentalloy High Aesthetic, Titanium Memory ThermaTi Lite, and Titanium Memory Esthetic), three ?-titanium (?-Ti) wires (TMA, Colored TMA, and Beta Titanium), and one stainless steel (SS) wire (Stainless Steel) were considered for this study. Successively, a retrieved analysis of NiTi aesthetic archwires was done to evaluate the effect of the clinical use on the mechanical and physical properties of these wires, by means of AFM, Scanning Electron Microscope and Universal Testing Machine Instron. Five NiTi wires were considered for this study (Sentalloy, Sentalloy High Aesthetic, Superelastic Titanium Memory Wire, Esthetic Superelastic Titanium Memory Wire, and EverWhite). Results: The first experimental study highlights how the surface roughness of the wire was affected by the surface treatment but in different way according to the alloys and the technique. Coated NiTi wires were less rough than metallic and ion implanted wires, while ?-Ti ion implanted wires were less rough of normal wire. The AFM was a useful tool to assess surface roughness. The second experimental study showed that the clinical use and the oral cavity altered the physical and mechanical properties of the wires, especially for the aesthetic archwires that worsened considerably. After clinical use at AFM, surface roughness increased significantly. The SEM images showed homogeneity for the as-received control wires; however, after clinical use aesthetic wires exhibited a heterogeneous surface with craters and bumps. All the wires, except Sentalloy, showed a statistically significant increase in friction between the as-received and retrieved wires. Conclusion: Aesthetic orthodontic archwires are improving their properties since their introduction in orthodontics but still they do not have the same physical and mechanical properties of the metallic archwires.