EFFECTS OF SIALOADENECTOMY AND EXOGENOUS EGF ON MOLAR DRIFT AND ORTHODONTIC TOOTH MOVEMENT IN RATS

Effects on bone remodeling have been attributed to epidermal growth fa ctor (EGF). Sialoadenectomy (SX) removes the major source of EGF in ro dents and decreases both salivary and serum EGF levels. EGF effects on rat alveolar bone remodeling manifested by molar drift (MD) and ortho dontic tooth movement (OTM) were examined using the following two appr oaches: 1) EGF depletion by SX and replacement by orally administered EGF (50 mu g . animal(-1) . day(-1)); 2) sham rats supplemented with m atching amounts of EGF. MD and OTM were measured using cephalometric r adiographs; bone formation was measured histomorphometrically using te tracycline labeling. Normal MD was not detected after SX, and alveolar bone formation was significantly reduced both around the tooth and in nondental sites. Replacement EGF given to SX rats and supplemental EG F administered to sham rats changed the direction and enhanced the rat e of MD. A mesially directed orthodontic force applied to the molars o f SX animals increased bone formation on the distal aspect of the toot h roots. Supplemental EGF did not significantly affect OTM. EGF affect s alveolar bone remodeling, as manifested clinically by alterations in normal maxillary MD.