The effect of crystal growth on shear bond strength of metallic brackets and atomic force microscope topographic evaluation of treated enamel

Document Type : Original Article

Authors

1 Department of Pediatric Dentistry and Public Health, Faculty of Dentistry, Mansoura University, Mansoura, Egypt

2 Department of Orthodontics, Faculty of Dentistry, Mansoura University, Mansoura, Egypt

Abstract

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.

Keywords