Cobalt Release and Allergic Reactions in Patients Treated with RDPs

Methods:  Sixty-six patients (mean age 67 ± 11 years) treated with 84 RDPs (49 upper, 35 lower RDPs) were clinically examined after 1-5 years. A cobalt (Co) spot test was performed on the 84 RDPs (functional RDPs) and on 33 RDPs under fabrication not yet inserted in the oral cavity (non-functional RDPs). Allergic reactions were tested by cobalt, chrome (Cr), molybdenum (Mo) and methyl methacrylate (MMA) patch tests placed on the upper back of 44 patients. An oral smear was performed in patients showing sign of inflammation in the underlying mucosa and the RDPs were evaluated for complications.

Results: None of the cobalt spot tests performed on the functional RDPs were positive, whereas Co was released in 24 out of the 33 non-functional RDPs. None of the 44 patients showed signs of allergic reactions in the patch test. Of the 66 patients, 11 had inflammation in the underlying mucosa; 2 had candida infection, 7 had ill-fitting RDPs, and for 2 patients the inflammation could not be explained by allergic, candida or technical complications. Complications were registered in 34 patients. The most prominent complication was ill-fitting RDP.

Conclusions: RDPs released cobalt at fabrication stages but did not release cobalt 1-5 years after insertion. No clinical signs of allergic reactions towards Co, Cr, Mo and MMA were registered.