FUNCTIONAL INFLUENCE ON SUTURAL GROWTH - A MORPHOMETRIC STUDY IN THE ANTERIOR FACIAL SKELETON OF THE GROWING RAT

The aim of this study was to quantify the sutural response in the vari ous parts of the rat's upper frontal viscerocranium and study the poss ible effects caused by reduced masticatory muscle function. Twenty gro wing male albino rats were randomly divided into two equal groups: one group (Hard Diet group) received the ordinary diet in a hard pellets form, while the other (Soft Diet group) a soft diet. The experimental period started just before the rats' pubertal growth spurt (28 days ol d) and its duration was 28 days. After death, the heads of the animals were taken for preparation of undecalcified frontal sections, 100 mu m thick. Contact microradiographs of six representative homologous sec tions, for every animal in both groups, were prepared. The mean width, length, height, and interdigitation ratio of the internasal, naso-pre maxillary, and interpremaxillary sutures, as well as the orientation o f the bony surfaces of the naso-premaxillary suture were quantified on the contact microradiographs using the IBAS automatic image analysis system. The width of the sutural space was found to be significantly g reater in the Hard Diet group than in the Soft Diet group in all the s utures studied (P<0.01). No differences in the interdigitation of the sutures were found between the two groups, except in the internasal su ture in the middle part of the snout, where the Hard Diet group exhibi ted increased interdigitations. The bony surfaces of the naso-premaxil lary suture were significantly more parallelly-orientated in the anima ls with reduced masticatory muscle function (P<0.01). The above findin gs suggest that the dimensions and morphology of the facial sutures ar e significantly affected by reduced masticatory function. This may be one of the underlying mechanisms in the different growth patterns repo rted in previous studies.