Factors Affecting the Attractive Force of Dental Magnetic Attachment: A Literature Review for Guiding Dentists in Clinical Application

Abstract

Aim. The aim of this review is to get a comprehensive description of the factors that may influence the attractive force of the dental magnetic attachment. Background. Dental magnetic attachment is a term for a magnet used as an overdenture retainer. Magnets that are widely used are permanent magnets such as neodymium iron boron (NdFeB) and samarium cobalt (SmCo). Theoretically, the magnetic attractive force in a permanent magnet has a constant retentive force, and the magnitude of the force will not decrease over time. However, several studies revealed that the magnetic attractive force can be decreased, resulting in the failure of overdenture retention. Some of the factors of reduced magnetic attraction that have been studied are corrosion and temperature. There are no articles that specifically review the factors that can influence magnetic attraction. Review Results. A total of 25,880 articles were obtained during a search on 3 journal databases: PubMed (2,647), ScienceDirect (23,184), and Scopus (229). From those publications, 15 articles reported relevant outcome data that were then extracted. Magnetic attractive force can be influenced by temperature, corrosion, keeper surface morphology, type of magnet, keeper-assembly size combination, inclination, insertion-removal cycle, gliding/loading cycle, number of magnets, crosshead speed, and force direction. Conclusion. Many factors can affect the magnetic attraction force of the dental magnetic attachment. Corrosion is the most likely factor to occur because the dental magnetic attachment is always in the oral environment which contains corrosive saliva and is susceptible to damage due to mastication forces.

Influence of Coating Material Thickness on the Attraction Force of Dental Magnetic Attachment: An In Vitro Study

“…By applying varnish, it is expected that the magnet can be shielded from fluid exposure, consequently leading to corrosion prevention. Corrosion needs to be prevented because it is recognized as the most significant factor contributing to the decrease in magnetic attraction force [ 17 ]. The limitation of this study was the minimal sample size, and this was due to the difficulty of obtaining samples during the pandemic season.…”

Ideal set-up angle between a pair of oval dental magnetic attachments for suppression of the loss in retentive force associated with horizontal displacement

“…It has been established that the occurrence of a space between the mating faces of a pair of magnetic attachment is associated with decline in retentive force. The space between mating surfaces which is referred to as an air gap may occur due to technical errors during fixation of magnetic assembly into denture base [ 5 , 6 , 7 , 12 ]. However; actual measurements taken and three-dimensional finite element method of analysis indicates that even in the absence of a space between mating surfaces; any horizontal displacement between the magnetic assembly and keeper lowers the retentive force [ 13 , 14 ].…”