Objective    To study the effect of functional mandible shift on mandible development in pubertal rats.     Methods    Forty-eight male Sprague-Dawley rats at the age of 28 d were randomly divided into experimental group (n=24) and control group (n=24). Maxillary occlusal splints were designed to simulate mandible shift in experimental group. Six rats in each group were killed after 7

14

21

and 28 days，respectively. Right and left mandibles were removed for X-ray radiography and localizing points. Distance between the points was measured with an image analyzer.     Results    Fourteen days from experiment

the length parameters of the nonshifted mandible（Cd-Me

Co-Me

Go-Me）were significantly higher than those of the shifted mandible length in rats of experimental group（P0.05）

the height parameters of the non-shifted mandible were lower than those of the shifted mandible height（P0.05）

and the length and height parameters of bilateral mandibles were lower in experimental group than in control group（P0.05）.     Conclusion    The length and height of functionally shifted mandibles in pubertal rats are asymmetry and influence their development

suggesting that patients with functional mandible shift should be treated as early as possible.