the residual adhesive after debonding using two concentrations
of sulfated polyacrylic acid and the conventional acid etchant, and
the topography of treated enamel using Atomic Force Microscopic
examination (AFM).
Methodology: A total of 75 premolars were divided into three
groups; 20 teeth each for shear bond strength test, and 5 teeth each
for AFM. Three solutions were used; Solution I, 37% phosphoric
acid, and two concentrations of sulphated polyacrylic acid
(Solutions II, and III). Brackets were bonded, and the shear bond
strength was measured using a universal testing instrument at a
crosshead speed of 1mm/min. The residual adhesive was explored
using a stereomicroscope at 20 times magnification, and quantified
using the ARI. The topographic pattern of treated enamel was
evaluated, using AFM, and an untreated enamel as a negative
control.
Results: Solutions II and III, demonstrated lower shear bond
strength (10.6MPa, 6.1MPa), compared with that of acid etchant
(17.5 MPa). A significant difference in the distribution of ARI
scores was found between group I and II, III (P ;0.001), with more cement remaining on the teeth of group I. The AFM images
showed a noticeable difference in the surface topography, with
crystal deposits on the enamel surfaces treated with solution II.
Conclusions: The concentration of 30% sulfated polyacrylic
acid can be considered as an alternative to phosphoric acid. The
shear bond strength value obtained was above the minimum of the
clinically accepted for orthodontic use.