EGF EFFECTS ON RAT ORTHODONTIC TOOTH MOVEMENT AND MOLAR DRIFT

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Many biological effects have been attributed to EGF, including effects on long bone remodeling. The major source of EGF in the rat is the submandibular gland. Sialodenectomy (Sx) has been shown to deplete both salivary and serum EGF levels. This study was done to determine the effects of EGF on alveolar bone as evidenced by: orthodontic tooth movement (OTM) and molar drift (MD). The classical OTM curve has three parts that represents different processes. The initial movement represents tissue deformation. The second phase of delayed movement reflects recruitment of cells and the establishment of microenivronment that well allow the appropriate tissue and remodeling. The final phase of resumed movement represents tissue turnover which allows the reduction of the applied strain. OTM in rats must also contend with the natural tendency of molars to drift distally at the rate of ca. 7 micrometes m/day. The effects of Sx with or without orally administrated EGF on OTM and MD was studied in male Sprague-Dawley rats. Adult rats (400-425g) were divided into the following groups (n=5/group): 1)Sx, force (40 g initial tipping force to maxillary molars); 2) SX no force, EGF; 4) Sham (Sh), force; 5 Sh, force, EGF; 6) Sh, no force: 7) Sh, no force, EGF. OTM and MD were determined, with respect to palatal implants, using extraoral cehpalometrics obtained at appliance to Sx rats restored molar drift, changed its direction and enhanced its rate. Similarly, even accounting for mesial drift, SH animals receiving EGF showed a marked stimulation of the second phase of OTM, exhibiting a two- fold increase in tooth movement over that seen in Sh alone. It appears that EGF may be involved in the second phase of OTM and in normal maxillary molar drift.