Document Detail

Torque capacity of metal and polycarbonate brackets with and without a metal slot.
MedLine Citation:
PMID:  15366389     Owner:  NLM     Status:  MEDLINE    
The aim of the present study was to investigate slot deformation and the equivalent torque capacity of polycarbonate brackets with and without a metal slot in comparison with those of a metal bracket. For this purpose, the expansion characteristics and, in a further investigation, the labial crown torque of an upper central incisor, were measured in a simulated intra-oral clinical situation, using the orthodontic measuring and simulation system (OMSS). Three types of bracket with a 0.018 inch slot were tested: polycarbonate Brillant without a metal slot, Elegance with a metal slot and the metal bracket, Mini-Mono. For testing purposes the brackets were torqued with 0.016 x 0.022 inch (0.41 x 0.56 mm) and 0.018 x 0.022 inch (0.46 x 0.56 mm) ideal stainless steel archwires. In the activating experiments, significantly higher torque losses and lower torquing moments were registered with both rectangular archwires with the polycarbonate brackets than with the metal bracket. In the simulation tests, significantly higher torquing moments were registered with the metal bracket than with the polycarbonate brackets. The values for the Elegance bracket were between those of the Mini-Mono and Brillant brackets. The OMSS model approximates the clinical situation, with the torque loss being notably higher than in the in vitro activating experiments. This is due to the adjacent teeth giving the archwire additional play. In addition, the torquing process may twist the archwire, resulting in subsidiary forces. On the basis of the present results, all three brackets can be recommended for torquing. However, in view of the high torque losses, the torques programmed in the straightwire technique must be seen as questionable. Data should be provided by the manufacturer on the bending to be expected in polycarbonate brackets, which has to be offset by additional torque, or the bracket torque should be omitted from the technical specifications.
Winfried Harzer; Christoph Bourauel; Henner Gmyrek
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  European journal of orthodontics     Volume:  26     ISSN:  0141-5387     ISO Abbreviation:  Eur J Orthod     Publication Date:  2004 Aug 
Date Detail:
Created Date:  2004-09-15     Completed Date:  2004-10-21     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  7909010     Medline TA:  Eur J Orthod     Country:  England    
Other Details:
Languages:  eng     Pagination:  435-41     Citation Subset:  D; IM    
Department of Orthodontics, Technical University of Dresden, Germany.
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MeSH Terms
Dental Alloys / chemistry*
Materials Testing
Orthodontic Appliance Design*
Orthodontic Brackets*
Polymers / chemistry*
Stainless Steel / chemistry
Stress, Mechanical
Surface Properties
Reg. No./Substance:
0/Dental Alloys; 0/Polymers; 12597-68-1/Stainless Steel; 24936-68-3/lexan

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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