The aim of this study To compare in vitro shear bond strength (SBS) of different
orthodontic adhesives in and rebonding metal brackets after preparing their bases
mechanically.
Material and methods:Sample consisted of 40 extracted first premolars,
randomly
divided into two groups (n=20),.Adhesive removed by tungsten carbide bur later the
brackets were rebonded. The tests were performed in a tecnotest (6kN) SBS testing
machine, at a speed of 1 mm/min.
It was found that the mean shear bond strength of Reseliencewas 19.25 MPa and that
of Heliosit orthodontic was 10.25MPa.We foundthat the mean shear bond strength of
rebonding forReselience was 13.70 and 7.95 forHeliosit.The t-test revealed that there was a
significant difference between the shear bond strength of the two groups.
We found a significant difference between bonding and rebondingfor
Reselience,while there was no significant difference between bonding and rebonding for
Heliosit.
Many techniques have been used in repair and strengthening of
reinforced beam, among which are external steel beams, external
pre- stressing, epoxy injection, additional concrete overlay, external
steel plates, additional longitudinal and transver
se - steel bars.
Fifteen R.C. beams were tested until failure and the deflection,
surface strains, internal steel strains, external steel strains and crack
patterns were measured, the results were analyzed and conclusions
were summarized. Finally, the recommendations were stated with
the needed future work.
