title: Sixteen-week analysis of unaltered elastomeric chain relating in-vitro force degradation with in-vivo extraction space tooth movement.
abstract: BACKGROUND
  The purposes of this study were to evaluate whether unaltered elastomeric chain can continue to move teeth for 16 weeks and to relate it to the amount of force remaining for the same batch of elastomeric chains.
  
  
  METHODS
  The in-vivo portion of the study had a sample of 30 paired extraction space sites from 22 subjects who were measured for closure of the space every 28 days. The altered side elastomeric chain served as the control and was replaced at 28-day intervals whereas the experimental side remained unaltered. In the in-vitro portion of the study, 100 each of 2-unit and 3-unit segments of the same batch of elastomeric chains were placed in a water bath, and the force was measured for 20 of each segment length at the 28-day measurement points.
  
  
  RESULTS
  Statistically significant amounts of space closure occurred at both the altered and unaltered sites at all measurement time points. The mean space closure at the altered sites was minimally greater than that observed at the paired unaltered sites. The mean differences of space closure between the altered and unaltered sites ranged from a minimum of -0.05 mm at 4 weeks to a maximum of -0.14 mm at 8 weeks. The elastomeric chain force degraded rapidly by 4 weeks but continued a gradual diminution of force to 86 g at 16 weeks.
  
  
  CONCLUSIONS
  Unaltered elastomeric chain continued to move teeth into extraction spaces for 16 weeks in this sample from both statistically and clinically significant standpoints. There were minimal and statistically insignificant differences in the mean space closure measurements between the paired altered and unaltered sites. The elastomeric chain force at 16 weeks was less than 100 g, yet at the same time point, teeth continued to move clinically.
authors.affiliation: Private practice, Dallas, Tex.
authors.forename: Kristin S
authors.initials: KS
authors.lastname: Evans
authors.affiliation: Private practice, Nashville, Tenn.
authors.forename: Cory M
authors.initials: CM
authors.lastname: Wood
authors.affiliation: Division of Orthodontics, Vanderbilt University Medical Center, Nashville, Tenn. Electronic address: ahmgm@aol.com.
authors.forename: Allen H
authors.initials: AH
authors.lastname: Moffitt
authors.affiliation: Network clinician, Paducah, Ky.
authors.forename: John A
authors.initials: JA
authors.lastname: Colgan
authors.affiliation: Network clinician, Tupelo, Miss.
authors.forename: J Kevin
authors.initials: JK
authors.lastname: Holman
authors.affiliation: Network clinician, Chicago, Ill.
authors.forename: Steven D
authors.initials: SD
authors.lastname: Marshall
authors.affiliation: Network clinician, Flossmoor, Ill.
authors.forename: D Spencer
authors.initials: DS
authors.lastname: Pope
authors.affiliation: Network clinician, Decatur, Ala.
authors.forename: Lew B
authors.initials: LB
authors.lastname: Sample
authors.affiliation: Network clinician, Baton Rouge, La.
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Sherman
authors.affiliation: Network clinician, Torrance, Calif.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Sinclair
authors.affiliation: Network clinician, Montgomery, Ala.
authors.forename: Tim S
authors.initials: TS
authors.lastname: Trulove
mesh_terms: D006801:Humans; D066298:In Vitro Techniques; D009967:Orthodontic Appliances; D019516:Orthodontic Space Closure / Q000295:instrumentation / Q000379:methods*; D013997:Time Factors; D014081:Tooth Extraction; D014087:Tooth Movement Techniques