2Hawley CA. A Removable Retainer[J]. Int J Orthod Oral Surg, 1919, 2:291 - 298.
3Gary GD, Dunn WJ. Wear comparison of thermoplastic material used for orthodontic retainers [J]. Am J Orthod Dentofacial Orthop, 2003, 124 (3) :294 - 297.
4Heier EE, De Smit A A,Wijgaerts IA. Periodontal implication of bonded versus removable retainers [J]. Am J Orthod, 1997,112(6) :607 - 616.
5Loee H, Silness J. Periodontal Disease in pregnancy 1 prevalence and severity[J]. Acta Odontol Stand. 1963,21 (12) : 533 - 551.
6Silness J, Loee H. Periodontal Disease in pregnancy 11 :correlation bettween oral hygiene and periodontal condition[J]. Acta Odontol Scand. 1964,22(2) : 121 - 135.
7Haydar B, Karabulut G, Ozkan S, et al. Effects of retainers on the articulation of speech [ J ], Am J Orthod, 1996,110 ( 5 ) : 535 - 540.
8Sauget E,Covell D Jr, Boero RP, et al . Comparison of occlusal contacts with use of Hawley and clear overlay retainers[J] .The Angle Orthod, 1997,67(3) :223 - 230.