title: In vitro evaluation of force degradation of elastomeric chains used in orthodontics.
abstract: OBJECTIVE
  To analyze the in vitro force degradation of four different brands of elastomeric chains: American Orthodontics, Morelli, Ormco and TP Orthodontics.
  
  
  METHODS
  The sample consisted of 80 gray elastomeric chains that were divided into four groups according to their respective manufacturers. Chain stretching was standardized at 21 mm with initial force release ranging from 300 g to 370 g. The samples were kept in artificial saliva at a constant temperature of 37°C and the degradation force was recorded at the following time intervals: initial, 1, 3, 5, 7 and 9 hours, and 1, 7, 14, 21, 28, and 35 days.
  
  
  RESULTS
  There was a statistically significant difference between the groups regarding the force degradation, mainly within the first day, as a force loss of 50-55% was observed during that time in relation to the initial force. The force delivered at 35 days ranged from 122 g to 148 g.
  
  
  CONCLUSIONS
  All groups showed force degradation over time, regardless of their trademarks, a force loss of 59-69% was observed in the first hour compared to baseline. However, because the variation in force degradation depends on the trademark, studies such as the present one are important for guiding the clinical use of these materials.
authors.affiliation: PUC-RS.
authors.forename: André
authors.initials: A
authors.lastname: Weissheimer
authors.forename: Arno
authors.initials: A
authors.lastname: Locks
authors.forename: Luciane Macedo
authors.initials: LM
authors.lastname: de Menezes
authors.forename: Adriano Ferreti
authors.initials: AF
authors.lastname: Borgatto
authors.forename: Carla D'Agostini
authors.initials: CD
authors.lastname: Derech
mesh_terms: D000704:Analysis of Variance; D020724:Elastomers / Q000737:chemistry*; D008422:Materials Testing / Q000379:methods*; D009971:Orthodontics, Corrective / Q000295:instrumentation*; D011140:Polyurethanes / Q000737:chemistry*; D012464:Saliva, Artificial; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D020724:Elastomers; D011140:Polyurethanes; D012464:Saliva, Artificial
keywords: Biomedical and dental materials; Elastomers; Shear bond strength.