Elemental Analysis of Retrieved Orthodontic Space Maintainers

Objective: The purpose of the present study was to assess the elemental alterations of space maintainers after intraoral aging. Methods: Twelve in vivo aged space maintainers (lingual arches) were collected. The intraoral exposure time varied from 12 to 24 months. Ten as received wires and bands of the same brand were used as reference along with ten soldered joints. All the specimens were examined by SEM-EDS microanalysis. The elemental composition between the as received and in vivo aged devices were statistically analyzed by t-test (a=0.05). Results: The elemental compositions of the band and wire are similar to PH 17-4 (nominal composition (%wt): Fe: balance, 16–17.5 Cr, 3.0–5.0 Ni, 3.0–5.0 Cu, 0.70Mn, and 1.00 Si) and 303 stainless steel (nominal composition: (in wt%): Fe: bal., 17-19 Cr, 8-10 Ni, max 2 Mn, max 1 Si, and 0.6 Mo) respectively while soldering alloy comprises mainly of Ag (%wt: Ag:41.8, Zn:20.0, Cu:18.9, Cd:17.8, Mo:1.0 and Fe:0.4). Statistical analysis showed no significant differences in the elemental composition of the bands and wires after intraoral aging. However a significant decrease in the concentration of Zn (reference 20.0, in vivo aged: 9.6) and Cu (reference 18.9, in vivo aged: 8.1) was identified for the soldering alloy implying that this alloy sustained extensive ionic release under oral conditions. This behavior may be associated with the metallurgical structure of soldering alloy or with the galvanic corrosion developed between the stainless steels and soldering alloy in space maintainers. Conclusions: Under the conditions of this study, only the soldering alloy used for the production of space maintainers showed intraoral deterioration. The biological consequences of such alterations are not known. However, release of Zn and Cu have long been associated with the expression of a strong cytotoxic effect.