Effect of toothbrushing on elemental release from dental casting alloys

Purpose: This study assessed the effect of toothbrushing on the elemental release from common dental casting alloys. Materials and Methods: A Au-Pt high-noble alloy, a Au-Pd high-noble alloy, a Pd-Cu-Ga noble alloy, and a Ni-Cr base-metal alloy were placed into a biological medium for 1 week to allow equilibration of elemental release, then brushed for 30 minutes at 90 strokes/min under 200 g of force with a soft toothbrush. The brushing was performed in neutral saline or lactic acid at pH 4 with or without toothpaste. The alloys were then transferred back into a biological medium for 1 week. Atomic absorption spectroscopy was used to measure the mass lost from each alloy during and in the week after brushing. Mass loss was expressed as micrograms per square centimeter of alloy surface, and the various brushing conditions were compared by analysis of variance and Tukey multiple comparison intervals (α = 0.05). Results: During brushing, element release increased significantly over nonbrushed controls for all alloys except the Ni-Cr. Toothpastes, acidic solutions, or combinations of these conditions with toothbrushing further enhanced elemental release, but Ni release from the Ni-Cr alloy increased the most (30-fold). In the week after brushing, brushing alone increased elemental release only from the Ni-Cr alloy. However, toothpastes and acidic solutions increased elemental release for all alloys significantly, except for the Au-Pd alloy. In general, elemental release during brushing was far greater than in the week after brushing. Conclusions: Under the conditions of this study, toothbrushing increased the elemental release from dental casting alloys.