European Journal of Prosthodontics and Restorative Dentistry

Force-Distance Relation for Dental Magnets – Fitted Equation

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Cover Date

June 2023

Print ISSN

0965-7452

Electronic ISSN

2396-8893

Vol

31

Issue

2

Abstract

Objective: The force-distance power law for dental magnets had been unresolved
until a theoretical study found that only even inverse powers were allowed; for simple
magnets inverse fourth power was the only possibility. It remained to demonstrate that
this indeed did apply to real magnets, the present purpose. Methods: The force exerted
by a series of real dental magnets to a large steel plate, and in a few cases to dental
magnet keepers, as a function of distance was recorded. Curve-fitting of that data was
explored. using the equation previously used for long dipoles, but allowing the power
to be a free parameter. An index of 4 was the only feasible value. Corresponding fitted
parameter values were then examined in relation to magnet design and each other.
Results: The theoretical power law index was confirmed to be 4. For a satisfactory fit,
a ‘polar offset’ and a ‘stretch power’ were again required to better approximate the
experimental results. Polar offset appears to be a function of apparent pole strength;
stretch power less clearly so. Significance: The motivating question is settled.

ABSTRACT
Keywords
Power Law
Dental Magnets
Force-Distance Equation
Breakaway Force