الفهرس 
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Abstract
This in-vitro study was conducted to modify conventional glass
ionomer cement(GIC) with Salvadora persica (Miswak) extract (SPE) at
three different concentrations (SPE 8%, SPE 10%, SPE 15%). The
modified groups of glass ionomer cement were evaluated and compared
to the control group (SPE 0%) in terms of compressive strength, bond
strength, fluoride release, film thickness, setting time and antibacterial
activity.
Compressive strength was tested following the ADA specification
no.66 for glass ionomer cements. Cylindrical specimens were prepared
and tested using a universal testing machine. The specimens were placed
in vertical position and compressive load was applied along the long axis
of the specimens until fracture. The maximum load applied when the
specimen fracture was recorded and the compressive strength was
calculated.
The bond strength was evaluated by shear bond strength test to
dentin. Premolar teeth extracted for orthodontic reasons were used after
being flattened and embedded in gypsum. The mixed cement was placed
in a mould that was placed centrally on the dentin surface of the tooth.
All specimens were tested using the universal testing machine.
Fluoride release test was performed by preparing cylindrical
specimens which was then immersed and stored in plastic containers in
deionized water. The amount of released fluoride was evaluated at
different time intervals (1, 4, 7, 14 and 21 days) using an Ion selective
electrode(ISE). Fluoride release was calculated as the amount of fluoride
released per unit surface area of specimen (μg/cm2).
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Film thickness was measured by recording the combined thickness
of two optically flat glass plates stacked in contact and this measurement
was designated as a Reading (A). A standardized amount of each cement
mixture was placed between the two glass plates. Ten seconds before the
end of the manufacturer’s stated working time, a force of (150 ± 2) N was
applied vertically and centrally on the upper glass plate. Ten minutes
later, the overall thickness of the plates and the cement was recorded as a
Reading (B). The difference between readings A and B was considered as
the thickness of the film.
Setting time was measured using an indenter with a mass of 400 ±
5g, it is a needle having a flat end that is perpendicular to the long axis of
the needle. The indenter will be placed on the cement’s surface and the
surface will be inspected for any indentation. The setting time was
measured from the start of mixing till the time when the indenter failed to
make complete circular indentation on the surface
The antibacterial activity of GICs was evaluated using agar
diffusion test against Streptococcus Mutans and Lactobacillus Casei
under aseptic conditions. Specimens were placed in petri dishes
containing the nutrient medium with the bacterial inoculum and incubated
for 24 hours. Positive results were scored when a zone of inhibition is
formed around the specimens where the diameter of the zone was
measured using a digital calliper.
Results of the compressive strength test revealed that the modified
groups were significantly higher compared to the control group. While
for the bond strength test, the three modified groups showed statistically
significant lower mean values compared to the control group. The mean
cumulative fluoride release after 21 days for the each of the modified groups was significantly lower than the control group. However, there
was a rapid initial release rate after 1 day for all the tested groups that
gradually slowed down over the experimental period.
Film thickness test results showed no statistically significant
difference between all the tested groups. However, there was a significant
shortening of the setting time of the modified groups compared to the
control group. Moreover, such effect on setting time was found to be
concentration dependent. The modified groups showed significantly
higher zone of inhibition against Stepptoccous Mutans while no
significant difference in inhibition zones was recorded against
Lactobacillus Casei compared to the control group.
Under the limitations of this study, the following could be
concluded:
1. The addition of Salvadora persica (Miswak) extract
(SPE) had a positive effect on compressive strength of
glass ionomer cement.
2. SPE enhances the antibacterial activity of glass ionomer
cement against Streptococcus Mutans, with no
pronounced effect against Lactobacillus Casei.
3. The addition of SPE to glass ionomer cement shortened
the setting time and did not alter the film thickness.
4. Modification of glass ionomer cement with SPE had a
negative impact on the bond strength and fluoride release
of glass ionomer cements.