• Preeya Suwanwitid D.D.S.
• Chintana Sirichompun D.D.S., M.D.Sc., Diplomate, The Board of Orthodontics

Objective To compare the shear bond strength and adhesive remnant indices of metal brackets
photo-activated by 2 LED-curing devices with different light intensities.

Materials and methods Sixty first premolars from 30 patients undergoing an orthodontic treatment
(1 from the left and 1 from the right per patient) were extracted. From each patient, the first one was
then randomly allocated into group I and the other was group II. Premolar metal brackets were bonded
to the prepared enamel surfaces of the samples mounted in PVC-tube using a light-cured adhesive
resin named Transbond XT^®. In group I (LED WOODPECKER^® intensity 850 mW/cm²), and in
group II (Mini LED III^® intensity 2,200 mW/cm²), the specimens were light cured perpendicularly to
the metal bracket base for 10 and 3 seconds, respectively. All tooth specimens were then stored in
distilled water at 37°C for 24 hours. Shear bond strength was tested with a universal testing machine
at a crosshead speed of 0.5 mm/min until the bracket was debonded. Adhesive remnant indices
were determined with a stereomicroscope at a 10x magnification. Data of shear bond strength and
adhesive remnant indices were statistically analyzed by an independent t-test and a Chi-square test,
respectively, at a 0.05 statistically significant level.

Results Shear bond strength in group I and II were 21.34 ± 2.45 and 19.32 ± 1.89 MPa, respectively,
which were statistically significant difference. Inter-groupsû adhesive remnant indices were statistically
significant distributed.

Conclusion LED-curing devices with different light intensities significantly affected shear bond strength
of metal brackets and adhesive remnant index.

(CU Dent J. 2014;37:259-66)