Investigations into the failure of dental magnets

Purpose: The aim of this study was to determine the mechanisms of failure o f magnets used for denture retention. Materials and Methods: Magnets were r etrieved from dentures that had failed after 4 to 18 months of clinical use . The magnets were sectioned and the failure modes were evaluated using opt ical or scanning electron microscopy. Results: The magnetic retention syste m investigated consists of a neodymium-iron-boron magnet sandwiched in a st ainless steel keeper, capped with a titanium dome, and sealed with epoxy re sin. The diffusion of moisture through the epoxy seal and the breakdown of the encapsulating material led to corrosion of the magnet. In both cases, a loss in retention occurred as the corrosion products weakened the overall magnetic attraction. Conclusion: The failure of magnets may occur by either breakdown of the epoxy seal or breakdown of the encapsulating material. Bo th problems need to be addressed to prolong the life span of these magnets.