Improper orthodontic bracket position may necessitate bracket removal
and rebonding to establish correct bracket position. This procedure is
necessary to use efficient orthodontic mechanics. The purpose of the
study was to investigate (1) the amount of bonding resin remaining on
single crystal bracket bases following electrothermal debonding, and (
2) the bond strength of,rebonded single crystal ceramic brackets under
different treatment conditions. The bases of debonded, single crystal
ce ram ic brackets (n=100) were inspected for resin, classified with
an adaptation of the adhesive remnant index (ARI), and evenly assigned
to four experimental groups (n=25). Groups were (1) silane coupling a
gent, (2) heat plus silane coupling agent, (3) hydrofluoric acid plus
silane coupling agent, and (4) heat plus hydrofluoric acid plus silane
coupling agent. An additional group of brackets not previously bonded
was used as the control (n=25). The brackets were bonded to 125 fresh
bovine teeth. A force was applied 1 mm from the bracket-resin interfa
ce by a testing machine. The force measured in this experiment was she
ar/peel and the ratio of shear to peel was 0.53. The ARI index showed
79% of the brackets had no resin on their bases. The shear/peel bond s
trength was significantly greater for the control group than all other
groups (P<0.01). Treatment of electrothermally debonded ceramic brack
ets with silane or heat plus silane resulted in bond strength greater
than 9 MPa. The use of hydrofluoric acid significantly reduced the bon
d strength below 2 MPa.