Degradation of lingual orthodontics archwires. The effect of corrosion and nickel release on their properties

• Autores: Carlos Suárez Martínez
• Directores de la Tesis: Francisco Javier Gil Mur (dir. tes.), Mª. Teresa Vilar Martínez (dir. tes.)
• Lectura: En la Universitat de Barcelona ( España ) en 2007
• Idioma: inglés
• Tribunal Calificador de la Tesis: Josep Duran i Carpintero (presid.), Jorge Vilarrasa Adam (secret.), Ignasi Serra (voc.), Mª Nebra Molins (voc.), Josep Maria Manero (voc.)
• Materias:
  • Ciencias médicas
    • Cirugía
      • Ortodoncia-estomatología
• Enlaces
  • Tesis en acceso abierto en:  TDX  Dipòsit Digital de la UB 
• Resumen

  • The purpose of the present thesis is to be a basic and initial contribution to the knowledge about the corrosive behaviour of the archwires commonly used in lingual orthodontics. Once corrosive behaviour is understood, conclusions could be drawn regarding clinical implications both for the progress of the treatment and the patients' safety.The archwires chosen for the study were:1. Respond® 0.0175 inches2. D-Rect® 0.016x0,022 inches3. Stainless Steel 0.016 inches4. Stainless Steel 0.016x0,022 inches5. Ni-Ti® 0.016 inches6. TMA® 0.016 inches7. Copper Ni-Ti® 0.017x0.017 inchesThe objectives of the thesis are:1. To study the as-received microscopical aspect of the lingual orthodontics archwires and the surface structural changes of the archwires after being in contact with a saline preparation for 30 days through scanning electronic microscopy (SEM) and atomic force microscopy (AFM)2. To study the basic corrosive properties of the archwires in order to determine the potential of corrosion and the pitting potential for each archwire and also the microscopical effects of corrosion on archwires with SEM and AFM after anodic potentiostatic polarization.3. To study the ionic release of Ni of the Ni containing archwires to evaluate its potential danger for the patient.4. To evaluate the changes that corrosion may have on the martensitic and austenitic phase transformations of the nickel and titanium containing archwires. The highest tendency to general corrosion was seen for Respond archwires followed by D-Rect and 0.016 inch Stainless Steel archwires. Cyclic Voltammetry results showed that Ecorr values were similar for Respond, D-Rect and 0.016x0.022 Stainless Steel archwires being the 0.016 Stainless Steel archwires the most prone to corrosion processes. It was seen that archwires made of Ti alloys were highly resistant to general corrosion processes. The lowest Eb values were obtained for Respond archwires followed by D-Rect and 0.016 Stainless Steel archwires. Higher values were observed for 0.016x0.022 Stainless Steel archwires.AFM enabled an objective characterisation of surface changes by measuring the Roughness Mean Surface (RMS). This value allowed a comparison between archwires immersed in Hank's Balanced Salt Solution for 30 days and a control group. Results show statistically significant differences after immersion for all archwires with the exception of NiTi archwires. Scanning electronic microscopy did not enable to see differences between both groups.Ni release has been seen to be very low and it is far below the limits set by the European Union legislation and the levels known to inflict cell damage. The highest amount of Ni was released by the Stainless Steel archwires followed by Respond and NiTi archwires. The lowest amounts of Ni released were recorded for CuNiTi and D-Rect archwires.With regards to calorimetry, NiTi archwires showed a clear R-phase while none of the CuNiTi archwires did in the new, polarised and immersed groups.Immersion seems to have no impact on the phase transition temperatures of NiTi archwires while some changes observed in CuNiTi arches should be further studied.