5Russell KA, Folwarczrm MA. Mesiodens- diagnosis and management of a common supernumerary tooth[J]. J Can Dent Assoe,2003,69(6) :362-366.
6Jacobs SG. Radiographic localization of unerupted maxil- lary anterior teeth using the vertical tube shift technique:the history and application of the method with some case reports[J].Am J Orthod Dentofacial Orthop, 1999, 116 (4) :415-423.
7Bonder L, Bar ZJ, Becker A. Image accuracy of plain film radiography and computerized tomograthy in assessing morphological abnormality of impacted teeth[J]. Am JOrthod Dentofacial Orthop, 2001,20 (6):623-628.
