title: Force extension relaxation of medium force orthodontic latex elastics.
abstract: OBJECTIVE
  To evaluate the force extension relaxation of different manufacturers and diameters of latex elastics subjected to static tensile testing under dry and wet conditions.
  
  
  METHODS
  Sample sizes of 15 elastics from American Orthodontics (AO) (Sheboygan, Wis), TP (La Porte, Ind), and Morelli Orthodontics (Sorocaba SP, Brazil) were used. Equivalent medium force products were tested--3/16, 1/4, and 5/16 inch lumen size from each manufacturer--making a total of 1080 specimens. An apparatus was designed to simulate oral environments during elastics stretching. Forces were read after 1, 3, 6, 12, and 24 hour periods using the Emic Testing Machine (Emic Co., Sao Paulo, Brazil) with 30 mm/min cross-head speed and load cell of 20 N (Emic Co). Kruskal-Wallis and Dunn's tests were used to identify statistical significance.
  
  
  RESULTS
  Statistical differences between AO and the other brands were noted for all testing times. Significant variation in mechanical properties was observed in latex elastics from Morelli. Relationships among loads at the 0 hour time period were as follows: Morelli>AO>TP for 3/16 elastics (P = .0016), 1/4 elastics (P = .0016), and 5/16 elastics (P = .0087).
  
  
  CONCLUSIONS
  Significant differences in force extension relaxation were noted for elastics from these manufacturers. Force relaxation over the 24 hour time period was AO>Morelli>TP for 3/16 elastics, AO>TP>Morelli for 1/4 elastics, and TP>AO>Morelli for 5/16 elastics. The force decay pattern showed a notable drop-off of forces during 0 to 3 hours, a slight increase in force values from 3 to 6 hours, and a progressive force reduction over 6 to 24 hours.
authors: Othodontics and in Materials Science, State University of Rio de Janeiro and Military Institute of Engineering, Rio Janeiro, Brazil. fernandes.dj@gmail.com
authors: Daniel J
authors: DJ
authors: Fernandes
authors: Gisele M A
authors: GM
authors: Fernandes
authors: Flavia
authors: F
authors: Artese
authors: Carlos N
authors: CN
authors: Elias
authors: Alvaro M
authors: AM
authors: Mendes
references: Angle Orthod. 2006 May;76(3):475-9
references: 16637730
references: Am J Orthod Dentofacial Orthop. 2004 Jul;126(1):65-70
references: 15224061
references: Angle Orthod. 2007 Jul;77(4):688-93
references: 17605476
references: Angle Orthod. 1970 Oct;40(4):319-28
references: 5272407
references: Angle Orthod. 2004 Apr;74(2):234-9
references: 15132450
references: Angle Orthod. 2003 Apr;73(2):181-6
references: 12725375
references: J Oral Rehabil. 2005 Jan;32(1):72-7
references: 15634305
references: Am J Orthod Dentofacial Orthop. 2003 Apr;123(4):401-7
references: 12695767
references: Am J Orthod. 1977 Sep;72(3):296-302
references: 268941
references: Am J Orthod. 1970 May;57(5):476-8
references: 5265830
references: Eur J Orthod. 1986 Aug;8(3):198-201
references: 3464445
references: Am J Orthod Dentofacial Orthop. 2001 Jul;120(1):36-44
references: 11455375
references: Dent Mater. 1993 Jan;9(1):37-40
references: 8299868
references: Am J Orthod Dentofacial Orthop. 2000 Sep;118(3):280-7
references: 10982928
references: Angle Orthod. 1951 Jul;21(3):151-4
references: 14885796
references: Angle Orthod. 1970 Jul;40(3):151-8
references: 5269949