Assessment of slot sizes in self-ligating brackets using electron microscopy.
OBJECTIVE
To measure the slot dimensions of 0.022 inch self-ligating upper central incisor brackets from six manufacturers using electron microscopy, to compare the measured dimensions with the manufacturers' published dimensions, and to determine if the walls of the slots were parallel.


METHODS
Six self-ligating upper central incisor brackets from four manufacturers (SmartClip and Clarity SL, 3M Unitek, Monrovia, CA, USA; Speed, Strite Industries Ontario, Canada; Damon MX, Ormco, Orange, CA, USA; In-Ovation R and In-Ovation C, Dentsply GAC, Bohemia NY, USA) were imaged with a scanning electron microscope and the slots heights measured. Intra-operator repeatability and accuracy were determined.


RESULTS
All brackets had slot sizes that were significantly larger (p < 0.05) than the stated 0.022 inch. Speed brackets were 5.1 per cent larger (0.02311 inch) and the closest to the published dimension. The SmartClip brackets were 14.8 per cent larger (0.02526 inch) than the quoted slot size of 0.022 inch. In most brackets the distances between the slot walls was generally greater further from the bracket bases.


CONCLUSIONS
The actual measurements of upper central incisor self-ligating brackets from six manufacturers were larger than the manufacturers' stated dimension, and the walls of the slots diverged from the bracket bases.
Bhalla
Nidhi B
NB
Department of Orthodontics, King's College Hospital, London, United Kingdom. nbbhalla@hotmail.com
Good
Sarah A
SA
McDonald
Fraser
F
Sherriff
Martyn
M
Cash
Alex C
AC
D006801:Humans; D007091:Image Processing, Computer-Assisted; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D013499:Surface Properties