Metal ion quantification in the saliva of patients with lingual arch appliances using silver solder, laser, or TIG welding.

OBJECTIVES: Quantify metal ion release in the saliva, considering that orthodontic appliances with soldered or welded parts may suffer corrosion and release metal ions into saliva, which can trigger adverse effects, such as hypersensitivity. METHODS: Sixty-four patients were distributed into four groups: G1 (control), G2 (silver-soldered lingual arch), G3 (laser-welded lingual arch), and G4 (TIG-welded lingual arch). Saliva samples were collected at four different points and were analyzed for ion release with ICP-MS. RESULTS: For Cr, Fe, Cu, and Sn ion concentrations among groups, there was no difference along collections and no statistically significant difference throughout collections for any group (P > 0.05, with release values between 3.3 and 4.2 µg/L for Cr, 201 and 314.8 µg/L for Fe, 23.1 and 40.7 µg/L for Cu, and 13 and 27.7 µg/L for Sn). For Ni, G4 showed an increased ion release at T2 (14.3 µg/L) and T4 (34.5 µg/L), values with an interaction effect (P < 0.001) comparing the groups and the points of collection. For Zn, Ag, and Cd ions there was no difference along the points in time (P > 0.05). For Zn ions, there was a statistic difference from G4 to G1 and G2 (P = 0.007 and P = 0.019), with median values ranging from 741.7 to 963.4 µg/L for G4, and for Ag ions, from G4 to G2 and G3 (P < 0.001 for both), with lower medians for G4 (3.7-6.1 µg/L). For Cd ions there was a statistic difference from T1 to T4 in all groups (P = 0.016), with lower values for T4. CONCLUSIONS: Different welding procedures may affect salivary ion concentrations. For most ions there was no significant increase comparing welding and comparing throughout points in the same group. Although TIG welding presented greater Ni ion release, this possibly occurred due to a bigger corrosion of the welded. CLINICAL RELEVANCE: Determining the amount of released metal ions from the use of orthodontic appliances is relevant to ensure the safest method for patients. Welding procedures affect salivary ion concentrations, when comparing ion release triggered by one of the most common devices used for preventive/interceptive orthodontic treatments.