Mechanics in the Production of Mandibular Fractures: A Study with the "Stresscoat" Technique. I. Symphyseal Impacts

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Abstract
A non-destructive testing method, involving a brittle sensitive lacquer (Stresscoat) was applied to 27 human mandibles to determine the high tensile strain areas. The condyles of the jaws were either firmly fixed in place, free to move, or one fixed and the other freely moveable. A total of 675 tests were completed. The bones used were of various sizes and states of dentition. Mid-point chin impacts of 0.101 foot pound of energy indicate that high tensile strains, those causing fractures, were found on the lingual aspect of the chin and the lateral sides of the subcondylar areas when the ends of the bones were freely moveable. These indicate a flattening of the chin and an inbending of the condyles. Also patterns on the buccal alveolar walls indicate a mesial-distal compression of the alveoli. When the ends of the bone were firmly fixed, there was, in addition to chin flattening, a vibration of the subcondylar regions. Tensile strain patterns were also noted in some cases about the base of the mandible near the angle, about the mental foramen, lingual tuberosity and coronoid process.