Characteristics of the tooth in the initial movement: the influence of the restraint site to the periodontal ligament and the alveolar bone.

It is critical to clarify orthodontic load transfer mechanism from tooth to alveolar bone, and to determine the influence of applied orthodontic force on tooth behaviour. In this study, two dimensional (2-D) finite element (FE) models were constructed to simulate to mechanical behaviour observed during the initial movement of periodontal ligament (PDL) deformation, and to evaluate the effects of the presence of PDL and various restraint sites on tooth behaviour.A 2-D solid FE model of the tooth-PDL-alveolar bone system was constructed and investigated into stress distribution pattern and displacement.

Changes in the properties of secretory granules in the palatine gland acinar cells of the postnatally developing rat.

This study was designed to examine whether or not phospholipid is contained in the secretory granules of the rat palatine gland acinar cells, and if present, to examine the movements of phospholipid in the secretory granules during postnatal development. The palatine glands of male Wistar rats aged 0 to 56 days were used. Acid-hematin staining showed a few positive acinar cells with a faint reaction in the acini on day 0, numerous positive cells with an intense reaction on day 7, a weakening reaction in the cells on day 14, and almost no reactivity on day 35 and after.