title: Evaluation of force degradation characteristics of orthodontic latex elastics in vitro and in vivo.
abstract: OBJECTIVE
  To evaluate the characteristics of force degradation of latex elastics in clinical applications and in vitro studies.
  
  
  METHODS
  Samples of 3/16-inch latex elastics were investigated, and 12 students between the ages of 12 and 15 years were selected for the intermaxillary and intramaxillary tractions. The elastics in the control groups were set in artificial saliva and dry room conditions and were stretched 20 mm. The repeated-measure two-way analysis of variance and nonlinear regression analysis were used to identify statistical significance.
  
  
  RESULTS
  Overall, there were statistically significant differences between the different methods and observation intervals. At 24- and 48-hour time intervals, the force decreased during in vivo testing and in artificial saliva (P < .001), whereas there were no significant differences in dry room conditions (P > .05). In intermaxillary traction the percentage of initial force remaining after 48 hours was 61%. In intramaxillary traction and in artificial saliva the percentage of initial force remaining was 71%, and in room conditions 86% of initial force remained. Force degradation of latex elastics was different according to their environmental conditions. There was significantly more force degradation in intermaxillary traction than in intramaxillary traction. The dry room condition caused the least force loss.
  
  
  CONCLUSIONS
  There were some differences among groups in the different times to start wearing elastics in intermaxillary traction but no significant differences in intramaxillary traction.
authors.affiliation: Key Laboratory for Oral Biomedical Engineering of Ministry of Education, Department of Orthodontics, Hospital and School of Stomatology, Wuhan University,Wuhan, Hubei, China.
authors.forename: Tong
authors.initials: T
authors.lastname: Wang
authors.forename: Gang
authors.initials: G
authors.lastname: Zhou
authors.forename: Xianfeng
authors.initials: X
authors.lastname: Tan
authors.forename: Yaojun
authors.initials: Y
authors.lastname: Dong
mesh_terms: D000293:Adolescent; D000388:Air; D000704:Analysis of Variance; D002648:Child; D003799:Dental Stress Analysis; D004548:Elasticity; D005502:Food; D006801:Humans; D019248:Jaw Fixation Techniques / Q000295:instrumentation; D007840:Latex; D008422:Materials Testing; D009967:Orthodontic Appliances; D012044:Regression Analysis; D012463:Saliva; D012464:Saliva, Artificial; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D007840:Latex; D012464:Saliva, Artificial