Aim: Restorative dentists employ different bonding systems
between the resin and the dentin and other dentinal tissues to
achieve the goal of micromechanical retention. Studies have
shown that the bond between composite and dentin degrades
over time because of the action of matrix metalloproteinases
(MMPs) on collagen fibrils left unprotected by acid etching. The
MMPs may be partially responsible for hybrid layer degradation.
Since chlorhexidine (CHX) inhibits MMPs, we hypothesized that
CHX would decelerate the loss of resin–dentin bonds. Hence,
this in vitro study is intended to evaluate the effects of 2% CHX
on hybrid layer and bonding interface.
Materials and methods: Totally, 40 freshly extracted molars
were randomly divided into four experimental groups. In all
40 specimens, class II cavities were prepared to a depth of
1 mm below the dentinoenamel junction with no axial wall, but
the elimination of the proximal enamel ridge. The teeth were
then randomly divided into four experimental groups, i.e.,
All Bond 2 without 2% CHX (group I), All Bond 2 with 2%
CHX (group II), One Coat 7.0 without 2% CHX (group III),
and One Coat 7.0 with 2% CHX (group IV). All the specimens
were derooted and sectioned mesiodistally into two halves
and placed under water at 37°C for 3 months and observed
under scanning electron microscope for the hybrid layer and
resin tag formation.
Results: Groups I and II showed statistically significant difference
when the presence/absence of resin tags was compared.
When groups III and IV were compared for the presence/absence of hybrid layer and resin tags, the results were statistically
significant.
Conclusion: Between all the four experimental groups, irrespective
of the bonding systems used, we concluded that groups
with 2% CHX usage showed promising results with presence/
absence of hybrid layer and resin tags formation.
Clinical significance: Studies suggest that the bond between
composite and dentin degrades over time because of the action
of MMPs on collagen fibrils left unprotected by acid etching.
Measures should be taken to prevent this from happening and
thus allow bond between composite and dentin last longer.