Corrosion of Ferromagnetic Alloys used for Magnetic Retention of Overdentures

Abstract

Three ferromagnetic casting alloys intended for use with magnetically retained overdentures (compositions in wt%: #1, Pd 50, Co 47, Ga 2, Pt 1; #2, Pd 60, Co 37, Ga 2, Pt 2; #3, Pd 49, Co 46, Ga 2, Pt 2) were investigated. A 0.9% saline solution and an artificial saliva (Meyer) were used for evaluation of the electrochemical corrosion behavior of these alloys, utilizing standard potentiodynamic techniques. All alloys investigated possessed a good corrosion resistance in the potential range of the oral environment (from -100 to 300 mV versus SCE). In addition, alloys #1 and 3 appeared to be susceptible to pitting above +300 mV (SCE), while #2 was resistant to pitting and was found to passivate in 0.9% saline solution.

Ion release from metal-ceramic alloys in three different media

“…Chemical composition of alloy Starting with an alloy's chemical composition, some alloying elements are known by their lability more than other elements. Some alloying combinations may result in synergistic effects which alter the elements' lability and thus increase or decrease the ion release rate 2,3,5,6,22,28,29) . Ni, Cr, Mo, and Co had a decreasing effect on the corrosion rate of base metal alloys 5,17,24,[30][31][32] , whereas Fe had an increasing effect 10,24) .…”

“…Many studies have reported on the release of metallic ions from high-noble, noble, and base dental casting alloys under differing pH conditions which simulated the oral cavity 2,3) . A low pH environment (i.e., acidic conditions) increases the release of metallic ions from dental alloys.…”

“…Although Ti and its alloys are hypoallergenic and possess many of the clinically favored properties of type III and type IV Au dental alloys, their use is largely limited by their relatively high cost 16) . Ion release from dental alloys has been evaluated mainly by in vitro studies using these methods: cell culture media 1,8,15,17) , galvanism 18) , electrolyte baths 19) , evaluation of the influence of oral proteins on corrosion behavior 2,20) , exposure to different pH levels 2,3,5,10,20,21) , use of different surface treatments to cast alloys 9,13) , and power toothbrushing with toothpastes of different abrasivities 22) . In general, a static system is the most frequently used method to monitor the elements released from dental casting alloys.…”

Precision Attachments: A Review to Guide Clinicians

“…Systems like the locator and metal bar are less likely to wear over time, even after the simulation of 5000 cycles of insertion [21]. Therefore, they should have a better clinical outcome than ball attachments and magnets [10,11,21,27]. In a clinical trial, it has been reported that the locator and ball attachments need to be replaced with almost the same frequency [24].…”

“…Duomagnetic systems (magnet + magnet) instead are ones in which one magnet (the primary one) is placed on the implant, and a second one (the secondary one) is placed on the prosthesis, as for example the Steco Titanmagnetics ® and MicroPlant ® . Despite the improvements in the structure, in the oral cavity environment they are subject to corrosion, reducing their retentive capabilities in the long-term [10,11]. This system should be limited to use in cases of reduced vertical space available for the attachment.…”