The study aimed to evaluate the quality of the hybrid
layer form by three different adhesive systems. Class V
cavities were prepared on the buccal surface of fourty
extracted human premolars. The prepared teeth were
randomly assigned into four groups according to the
adhesive system and application mode. The systems
were: Optibond S (OS, total-etch); Optibond Versa (OV,
two-bottles, self-etch); Single Bond Universal (SBU,
one-bottle, self-etch) and Single Bond Universal with
etchant (SBU + etchant). All cavities were restored with
composite (Filtek Z350XT). The samples were sectioned,
polished and pretreated to remove minerals, protein
and water prior to SEM evaluation. From the images,
thickness of the hybrid layers was measured. Present of
resin tags and adaptation failure were also recorded. The
data obtained were analyzed using ANOVA, Dunnett’s
T3, Kruskal-Wallis and Mann-Whitney tests. OS group
showed the highest average hybrid layer thickness (4.34
µm), followed by SBU + etchant (3.06 µm), OV (1.91 µm)
and SBU (0.95 µm). Both adhesive and cohesive failures
were observed in SBU group. Present of prominent resin
tags were seen in both OS and OV groups. In conclusion,
all the investigated adhesive systems were able to perform
distinguishable actions as shown in micro-morphological
alteration and hybrid layer thickness. Two-bottles, selfetch
adhesive (OV) was proven to produce negligible
adaptation failure compared to other adhesive systems in
the present study. Combined all-in-one adhesive (SBU)
was found to render a superior bonding performance in
total-etch mode comparing to self-etch mode.