Force-Distance Relation for Dental Magnets – Fitted Equation

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  • Brian W. Darvell
  • Andrew P. Dias


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.

Power Law
Dental Magnets
Force-Distance Equation
Breakaway Force