4Brown S. The effect of orthodontic therapy on certain types of periodontal defects[J]. Periodol, 1973, 44: 742.
5Gomes SC,Varela CC,da Veiga SL, et al. Periodontal condi- tions in subjects following orthodontic therapy. A preliminary study[J]. Eur J Orthud, 2007. 29(5) :477-481.
6Grossi S, Genco R, Machtei E, et al. Assessment of risk of periodontal disease. Risk indicators for attachment loss[J]. Period, 1994, 65 : 23-29.
7Bakdash B. Oral hygiene and compliance as risk factors in periodontitis[J]. Periodontol, 1994. 65 : 539-44.
8Kokich VG. The role of orthodontics as an adjunct to perio dontal therapy. In Newman MGoTakei H,Carranza FA. Car ranza's Clinical Pcriodontology 9th ed [J]. Philadelphia:W. B. Saunders Co. 2002.
9Saito M,Miura Y,Notani K,et al.Stress distribution of abutments and base displacement with precision attachment andtelescopic crown-retained re-movable partial dentures(J).J Oral Rehabil,2003;30(5):482-7.
10The American Academy of Periodontology. The new classification for periodontal diseases and conditions [J] .Ann Periodontol, 1999, 4 (1) : 1-108.