title: A comparative evaluation of rate of space closure after extraction using E-chain and stretched modules in bimaxillary dentoalveolar protrusion cases.
abstract: BACKGROUND
  Aim of this study was to compare the rate of space closure between E-chain mechanics in one side of upper arch and by elastomeric module with ligature wire on the contralateral side in same patient.
  
  
  METHODS
  Thirty bimaxillary dentoalveolar protrusion cases were taken up for comprehensive fixed orthodontic treatment after extraction of all first premolars to retract both upper and lower anterior teeth. After initial alignment and levelling, alginate impressions were made for upper and lower arches and models constructed. In the upper arch model a vernier caliper was used to measure the extraction space in both sides from middle point of distal surface of canine to the middle most point of mesial surface of second premolar. This is the amount of space present before the onset of retraction mechanics. During space closure procedure two different retracting components were applied in right and left sides of each case. On right side elastic chain (E-chain) applied in both upper and lower arches and on left side elastomeric module with steel ligature (0.010") stretched double its diameter fixed in both arches. Both the mechanisms produced approximately 250-300 g of force as measured by a tension gauge. After onset of retraction mechanism all patients were recalled after every six weeks for three visits. In all these three visits modules and E-chains were changed. In all three visits impression was made, models constructed, and the remaining available space was measured by a vernier caliper up to 0.1 mm level variations.
  
  
  RESULTS
  Mean value for total space closure in case of E-chain was 2.777 mm whereas in case of module with ligature wire the value increased to 3.017 mm. Mean value for rate of space closure in case of E-chain was 0.2143 mm, whereas in case of module with ligature wire the value increased to 0.2343 mm with a standard deviation of 0.001104 and 0.001194, respectively. The standard deviation for total space closure was 0.1305 for E-chain and 0.1487 for module with ligature wire.
  
  
  CONCLUSIONS
  Space closure by elastomeric module with ligature wire is better than the E-chain.
authors.affiliation: Associate Professor (Orthodontics), Dept. of Dental Surgery, AFMC, Pune - 40.
authors.forename: Rajat
authors.initials: R
authors.lastname: Mitra
authors.affiliation: DDGDS (E & S), O/o DGDS, IHQ, MOD (Army), L Block, New Delhi - 11001.
authors.forename: S M
authors.initials: SM
authors.lastname: Londhe
authors.affiliation: Classified Specialist Orthodontics, Army Hospital (R & R) Delhi Cantt.
authors.forename: Prasanna
authors.initials: P
authors.lastname: Kumar
keywords: bimaxillary dentoalveolar protrusion; elastic chain; elastomeric module with ligature