الفهرس 
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Abstract
Several studies have shown that nicotine may be one of the
most significant risk factors for the development and progression
of periodontal disease. Smoking is a predisposing factor for
periodontal diseases and gingival recession )Darby and Walsh ,
2003). To overcome the effects of nicotine on the PDL there are
many stratigies, one of them is the smoking cessation. The other is
the use of antioxidants that eliminate prooxidants and scavenge
free radicals. The water-soluble antioxidant vitamin C can reduce
free radicals directly or indirectly (Sies et al., 1992).
Materials and methods:
77 adult male albino rats were used in this study. The rats
were divided into the following groups:
1. Control Group:
28 rats that were injected intraperitoneally with 0.2 ml distilled
water once daily for 2 weeks. The rats of this group were equally
subdivided into 4 subgroups (7 rats each) according to time of
scarification as follows:
Subgroup C 1: sacrificed 1 day after the last injection.
Subgroup C 7: sacrificed 7 days after the last injection.
Subgroup C 14: sacrificed 14 days after the last injection.
Subgroup C28: sacrificed 28 days after the last injection.
2. Nicotine positive control Group (NC):
Consisted of 7 rats each rat was injected intraperitoneally with
nicotine hemi-sulfate (N.H.S.) aqueous solution with a dose of 3.0
milligrams per kilogram (mg/kg) of body weight once daily for
two weeks. The rats of this group were sacrificed 1 day after the
last nicotine injection.
3. Experimental cessation group:(E)
Consisted of 21 rats each rat was injected intraperitoneally with
N.H.S. aqueous solution with a dose of 3.0 mg/kg of body weight
once daily for 2 weeks. The rats of this group were subdivided
into 3 subgroups (each consisted of 7 rats) according to time of
scarification after the nicotine injection has been stopped as
follows:
Group E 7: sacrificed 7 days after the last nicotine injection.
Group E 14: sacrificed 41 days after the last nicotine injection.
Group E 28: sacrificed 28 days after the last nicotine injection.
4. Experimental cessation plus vitamin C group:(EV)
Consisted of 21 rats each rat was injected intraperitoneally with
N.H.S. aqueous solution with a dose of 3.0 mg/kg of body weight
once daily for 2 weeks. On last day of nicotine injection, rats were
concomitantly start daily receiving vitamin C and the nicotine
injection was stopped. The rats of this group were subdivided into
3 subgroups (each consisted of 7 rats) according to time of
scarification as follows:
Group Ec 7: sacrificed after 7 days of vitamin administration.
Group Ec 14: sacrificed after 14 days of vitamin administration.
Group Ec 28: sacrificed after 28 days of vitamin administration.
Preparation of specimens for histological study
The Mandibular molar areas were excised and were
decalcified and processed for Haematoxylin and Eosin (H&E)
staining and immunohistochemical stainin.
Results:
The examination of the H& E in stained sections of the control
group showed that all the subgroups were of almost similar
results. The PDL principal fibers were densely packed and were
arranged in conveniently demonstrated groups: gingival,
interdental and alveolodental. In all of the above groups, there was
no aggregation of inflammatory cell infiltrate, no signs of
degenerated fibers or excessive resorption in cementum or
alveolar bone.
Nicotine control group (NC) revealed several alterations in
many of the structural criteria of the PDL. Wide spaces between
bundles of fibers which were irregularly arranged if compared to
the control group. The oblique fibers revealed detachment of the
PDL fibers from the cementum and aggregation of inflammatory
cells in proximity to these detached fibers. There were some
osteoclastic activities.
E7 group revealed minute changes from the nicotine control
group. The arrangement of the fibers in this group was more dense
and regular in comparison to the nicotine control group. The
oblique group of fibers showed an enhancement in the attachment
to the cementum. Group E14 showed a little improvement in
comparison to group E7 regarding the attachment of the fibers to
cementum and bone as well as the fiber regularity. On the other
hand, group E28 showed further enhancement in the fiber
remodeling and orientation as well as the resorption sites.
Examination of EV 7 group revealed some improvement in
the histological features when compared with both the nicotine
control group and the group E7. The fibers were denser, with
fewer voids observed, as well as they were attached to cementum
to some extent but still the attachment is not as in control group.
Some spacing voids were seen in some samples. The apical
fibers of group EV7 showed almost a similar histological picture
as group C. The interradicular group appeared almost normal
except for minute detachment of the fibers from the cementum.
The groups EV14 showed more improved histological
features with minute defects regarding the fiber orientation,
attachment and density. Group EV28 showed histological
features almost similar to control group except for minute
detachment of the PDL fibers in scattered regions.