征paper 一篇，
Surgical lengthening of the clinical crown.
Bragger J Clin Periodontol. 1992 Jan;19(1):58-63.
http://www.ncbi.nlm.nih.gov/pubmed/?term=Bragger++J+Clin+Periodontol.+1992+Jan%3B19(1)%3A58-63.
麻烦寄到joyce800110@hotmail.com
非常感谢><