Bond strength to etched and Re-etched enamel, dentin and dentino-enamel junction

Abstract

Etching and re-etching are frequently done technique to alter the tooth surface and
makes it more receptive to adhesion. This study was done to assess the effect of reetching
technique on bond strength to enamel, dentin and dentino-enamel junction.
60 extracted human upper premolars teeth were collected cleaned, sectioned at the
level of cervical line, embedded in acrylic block exposing certain grounded flat
surface of the crown and divided into 2 groups:
Group A (30 etched specimens) etched with total etch (37% phosphoric acid)
for 15 sec.
Group B (30 re-etched specimens) etched and re-etched with total etch
(37% phosphoric acid).
Both groups were subdivided into:
Subgroup 1 10 enamel specimens
Subgroup 2 10 dentin specimens
Subgroup 3 10 dentino-enamel junction specimens
A standardized cylinders of light cure composite resin were bonded, and the
specimens were stored in deionized distilled water for 24 h. and testing was done with
zwick test machine and statistically analyzed using analysis of variance test
(ANOVA) and student t-test.
The results showed non significant difference between all subgroups in group
A(etching group) and between all subgroups in group A Vs. group B subgroup 2(reetched
E), and showed a significant difference between all subgroups in group A Vs
group B subgroup 3 (re- etched EDJ) and between group B sub1&2 (re-etched E & D)
Vs group B sub 3 ( re-etched DEJ) ,furthermore there were a highly significant
differences between all subgroups in group A Vs group B sub 2(re-etched D) and
between group B sub 2(re-etched E) Vs groupB sub 2(re-etched D).
Re-etching the enamel didn’t decrease the shear bond while re-etching dentin
markedly decreased the bond strength. Further more re-etching the dentino-enamel
junction lies in between.