A cinefluorographic study of mandibular movement during feeding in the rat (Rattus norvegicus)

Abstract

With 8 plates in the text)The anatomy of the masticatory apparatus, and particularly of the mandibular joints, has led to the view that mandibular movement in the Rodentia is predominantly propalinal, or forwards and backwards in direction. As part of an investigation into the mechanism of function of the mandibular joints in these animals, the feeding behaviour of "August" strain and "Wistar" rats was examined by cinephotography and cinefluorography. The rats were trained to feed on barium sulphate impregnated biscuit and animal cake and to drink radio-opaque liquids. Cinefluorographic recordings of ingestion, mastication, deglutition and of drinking were taken in both the lateral and dorso-ventral projections.Analysis of the recordings has shown a fundamental separation of ingestive and masticatory activity in the rat, which can be attributed to the morphology of the jaws and particularly to the disparity in the lengths of the mandibular and maxillary diastemas. To bring the incisor teeth into occlusion for ingestion, the mandible is brought forward through the rest position and the condyle into articulation with the anterior part of the fossa. In mastication the condyle is moved backwards to bring the molar teeth into occlusion and the condyle into articulation with the posterior articular facet on the fossa. Once the mandible has been moved into the appropriate position for either ingestion or mastication and deglutition, the movements involved in the separation or chewing of the food are cyclical with combined horizontal and transverse movements as well as the fundamental vertical movement acting to open and close the mouth. The basic movement of ingestion carries the mandibular incisors upwards and forwards across the lingual surfaces of the maxillary incisors, so separating the bite. The grinding stroke of mastication is a horizontal movement carrying the mandibular molars anteriorly across the maxillary.

A Bio-Realistic Finite Element Model to Evaluate the Effect of Masticatory Loadings on Mouse Mandible-Related Tissues

“…Due to a misaligned mandible/cranium molars and incisors cannot be in occlusion simultaneously, forcing the mandible into a propalinal movement to activate both biting modes (Becht, 1953; Hiiemae and Ardran, 1968). …”

Plasticity of mandibular biomineralization in myostatin‐deficient mice

“…Among mammals, considerable information is known about murid rodent masticatory patterns (Hiiemä e and Ardran, 1968;Weijs, 1975;Weijs and Dantuma, 1975;Kobayashi et al, 2002) as well as adaptive plasticity of murid craniofacial tissues vis-à -vis altered physiological loads. In particular, early research on masticatory plasticity observed that growing rats raised postnatally on an ''overuse'' diet of hard/resistant items exhibit greater condylar and craniofacial dimensions, increased temporomandibular joint (TMJ) articular cartilage thickness, as well as a higher density of TMJ connective tissue and subchondral bone (Watt and Williams, 1951;Beecher and Corruccini, 1981;Bouvier and Hylander, 1984;Kiliardis et al, 1985;Kiliardis, 1986;Bouvier, 1987Bouvier, , 1988Bouvier and Zimny, 1987).…”

Biplanar X-ray motion analysis of the lower jaw movement during incisor interaction and mastication in the beaver (Castor fiber L. 1758)

“…Analyses of mandibular movement in the rat show a clear separation of ingestive, thus incisor interaction, and masticatory activity. This enables rodents to use incisors in gnawing independently of the oral cavity (Hiiemäe and Ardran 1968). The function of incisor interaction had been assigned to three types: (1) cropping or occlusion of tips of incisors not seen in rodents, (2) gnawing with the mandibular incisors moving upwards and sliding along the posterior or lingual side of the maxillary incisors, and (3) tooth-sharpening or thegosis (Shadle 1936;Every 1975;Krumbach 1904) with the mandibular incisors brought in a position anterior to the maxillary incisors (Druzinsky 1995).…”

“…Hiiemäe 1967;Weijs andDantuma 1975, 1981;Crompton and Hiiemäe 1970;Byrd 1981;Hiiemäe and Crompton 1971;Hiiemäe and Ardran 1968;Hiiemäe and Kay 1973;Luschei and Goodwin 1974;Gans and de Vree 1974;Oron and Crompton 1985), reviewed by Hiiemäe (1978). She distinguished "three components or strokes in a single cycle: a closing stroke (fast close) in which the teeth are converging and the lower jaw is moving rapidly upwards; a power stroke in which work, i.e.…”