Biomechanical evaluation of the equine masticatory action: calculation of the masticatory forces occurring on the cheek tooth battery.

The forces generated during equine mastication influence the teeth, as well as the periodontium, the jaw bones, the temporomandibular joints and materials used in dental therapy. Due to the limited accessibility of the cheek teeth located farther caudal in the equine oral cavity the measurement of the masticatory forces on these teeth is virtually impossible. The calculation of such forces is an appropriate, indirect alternative to direct measuring. Hence, a mathematical model, which respects several morphological features of the equine dentition, e.g. the Curve of Spee, is presented. The relevant parameters were measured on laterolateral radiographs of 24 cadaver heads and 6 skulls. Our calculations yielded two major results. (1) The masticatory forces increased from rostral to caudal. This increase was due to distinct anatomical features of the equine dentition, i.e. the Curve of Spee, the position of the teeth, and the length of the mandible. (2) The masticatory forces decreased with age. This decrease was due to the reduced height of the Curve of Spee in older horses. These results are discussed in view of veterinary dental treatment, with special reference to the geriatric horse.