مجال
التميز
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تميز دراسي وبحثي
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البحوث المنشورة
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البحث (1):
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عنوان البحث:
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Rheological properties of resin composites
according to variations in composition and temperature
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رابط البحث:
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Click
here
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تاريخ النشر:
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12–03–2014
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موجز عن البحث:
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Objective
To study the effect of compositional variables and temperature
(25 °C and 37 °C) on the rheological properties of contemporary
resin composites.
Methods
Fourteen commercial resin
composites with different resin matrices of Bis-GMA and TEGDMA, different
filler loading (41–65, v/v) and particle sizes (ranging 5 nm to
20 μm) were studied using a parallel plate rheometer. Shear sweep
measurements were made to determine each composite’s viscosity over the
angular frequency range of ω = 10−4–102 rad/s.
Data were analyzed using one way ANOVA, Bonferroni post hoc and t-independent
tests (p < 0.05).
Results
All composites exhibited
viscosity reducing with shear rate (pseudoplasticity). Viscosity averages
were calculated over the shear rate range. These viscosities increased as the
percentage of filler loading (by volume) increased ranging between
0.05–349.33 kPa s at 25 °C and 0.03–132.00 kPa s at
37 °C. Filtek Supreme XTE exhibited the highest viscosity at both
temperatures (p < 0.05). Filtek Bulk Fill on the other
hand, showed the lowest viscosity at both temperatures (p < 0.05).
Viscosity significantly decreased with the increase in the temperatures for
all materials (p < 0.05). The reduction ranged from 40.8%
(for Venus Diamond Flow) to 92.2% (for Spectrum TPH3).
Significances
There was a considerable variation in the resin composite viscosities
measured at 25 °C as an average value for shear-rate sweep. The factor
between the least and highest viscosities was about 7000.
The formulation differences that led to such a great variation were
primarily: (i) volume fraction of fillers and (ii) particle size, the latter
influencing total particle surface area.
Rheological properties such as viscosity
are key parameters influencing perceived differences in handling behavior of
resin composites.
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البحث (2):
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عنوان البحث:
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Polymerization kinetics and impact of post polymerization on the
Degree of Conversion of bulk-fill resin-composite at clinically relevant
depth
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رابط البحث:
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Click
here
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تاريخ النشر:
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19-08-2015
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موجز عن البحث:
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Objective
Since bulk-fill (BF) resin composites should cure efficiently to a
depth up to 4 mm, the aim of the study was to determine the time-dependence
of degree of conversion (DC) at that depth during 24 h post-irradiation.
Methods
Eight representative BF
resin composites were studied [x-tra base (XTB), Venus Bulk Fill (VBF),
Tetric EvoCeram Bulk Fill (TECBF), Sonic Fill (SF), Filtek Bulk Fill (FBF),
everX Posterior (eXP), Beautifil-Bulk Flowable (BBF), Beautifil-Bulk
Restorative (BBR)]. Specimens were fabricated in white Delrin moulds of
4 mm height and 5 mm internal diameter directly on an attenuated
total reflectance (ATR) accessory attachment of an (FTIR) spectrometer
(Nicolet iS50, Thermo Fisher, Madison, USA). Upper specimen surfaces were
irradiated in situ for 20 s with an LED curing unit (Elipar
S10 with average tip irradiance of 1200 mW/cm2). Spectra from the lower
surface were recorded continuously in real-time for 5 min and then at 30
and 60 min and 24 h post irradiation.
Results
Mean ranges of
DC4mm (%) of the materials at 4 mm depth were 39–67; 48–75; 45–74;
and 50–72 at 5, 30 and 60 min and 24 h respectively. DCs for XTB, VBF,
TECBF, FBF, BBR increased significantly 30 min after irradiation (p < 0.05)
and were not affected by subsequent time up to 24 h (p > 0.05).
DC for SF was not affected by subsequent time after 5 min (p > 0.05).
For eXP and BBF, DC increased 24 h after irradiation (p < 0.05).
The data were described by the superposition of two exponential functions
characterising the gel phase (described by parameters a, b) and the glass
phase (described by parameters c and d).
Significance
Post
polymerization impact of bulk-fill composites is material dependent. Five
materials exhibited their maximum DC4mm already 30 min after
starting the irradiation while DC4mmfor two materials optimized after
24 h. BF materials were found to exhibit after 24 h a DC between 50
and 72% at 4 mm depth under the stated irradiation conditions.
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المؤتمرات العلمية:
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المؤتمر (1):
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عنوان المؤتمر:
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22nd European Dental Material Conference
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تاريخ الإنعقاد:
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30 – 31 August 2013
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مكان
الإنعقاد:
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Birmingham, UK
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طبيعة المشاركة:
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Poster presentation
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عنوان المشاركة:
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Determination of stickiness for
resin-composite pastes by a probe method
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ملخص المشاركة:
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Objectives
To
determine the stickiness of unset resin-composites with and without
Speedmixer in terms of maximum probe separation-force (Fmax) and
work-of-separation (W).
Methods
Seven
commercial resin-composites of similar filler loading (54-63.3%) but
different in resin mixtures were selected (n=6). Resin-composite pastes were
placed inside a cylindrical cavity (φ= 8, depth= 4 mm) fixed to the platform
of a texture analyser instrument. A flat-ended stainless-steel probe (φ=5 mm)
was fixed to the upper member of the instrument and lowered into the surface
of the unset specimen at 0.10 mm/s cross head speed to measure the
stickiness. Maximum separation force (Fmax, N) and work done (W, N.mm) were
measured. The same methodology was repeated for a new set of materials except
that they were first placed in a Speedmixer device operated at 1500 RPM for
30 sec before measurement. Data were analysed using one way ANOVA, Dunnetts’s
post-hoc and t independent tests (p<0.05).
Results
The
set of resin composites varied in Fmax and W (p<0.05) with and without
Speedmixer. Fmax and W ranged from 1.18 to 2.01 and 0.45 to 1.30 respectively
without the use of the Speedmixer. Also, they ranged from 1.37 to 2.21 and
0.61 to 1.30 respectively after being placed in the Speedmixer. The
Speedmixer exposed the resin composites to a high speed multi-directional
movement which had an effect on the stickiness of some of the resin
composites expressed by Fmax. While it increased for IPS Empress Direct (1.76
and 2.21 N without and with) and Tetric EvoCeram (1.27 and 1.73 N before and
after); it decreased for Filtek Supreme XTE (2.01 and 1.67 N, without and
with) (p<0.05) and Venus (1.73 and 1.53 N without and with).
Conclusion
Maximum probe separation-force (Fmax) and
work done (W) are appropriate parameters to measure stickiness of resin
composites.
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المؤتمر (2):
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عنوان المؤتمر:
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AADR/CADR Annual Meeting and Exhibition
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تاريخ الإنعقاد:
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19-22 March
2014
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مكان
الإنعقاد:
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Charlotte, N.C., USA
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طبيعة المشاركة:
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Poster presentation
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عنوان المشاركة:
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Rheological
properties of resin composites according to composition and temperature
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ملخص المشاركة:
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Objective
To study the effect of resin matrices
composition, filler and temperature (25°C and 37°C) on the rheological
properties of resin composites.
Methods
Fourteen recent resin composites of
different resin matrices of Bis-GMA and TEGDMA, different filler loading
(41-64%) and sizes (ranging 5nm-20µm) were studied using Bohlin rheometer. It
conducted steady shear sweep test in order to measure the composites
viscosity. The geometry used in this test was an aluminium parallel plate
20mm in diameter. Composite paste was placed on the rheometer lower plate,
after which the upper plate was lowered to adjust the gap to 250µm. After
residual normal stress was relieved, a frequency sweep test was completed
over the angular frequency range of ω=0.1–100 rad/s. Data was analysed using
one way ANOAV, Bonferroni post-hocand t-independent tests (p<0.05).
Results
All composites exhibited pseudoplasticity.
The viscosity increased as the percentage of filler loading (by volume) was
increased, but decreased with increasing temperature (25°C to 37°C). For
similar filler volumes, as the filler size decreased, viscosity increased.
Statistically significant differences in viscosity presented between the
materials at 25°C and 37°C (p<0.05). Viscosity ranged 0.05-349.33 KPas at
25°C and 0.03-132.00 KPas at 37°C. Filtek Supreme XTE exhibited the highest
viscosity at both temperatures (p<0.05). Filtek Bulk Fill on the other
hand, showed the lowest viscosity at both temperatures (p<0.05). Viscosity
significantly decreased with the increase in the temperatures for all
materials (p<0.05). The reduction ranged from 40.81% (for Venus Diamond
Flow) to 92.22% (for Spectrum TPH3).
Conclusion
Composite
resin rheological properties are significantly affected by the composite
resin matrices composition, filler content (size and loading), and
temperature. Filtek Supreme XTE and Filtek Bulk Fill exhibited the highest
and lowest viscosities respectively (p<0.05). Viscosity significantly
decreased with the increase in the temperatures for all materials
(p<0.05).
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المؤتمر (3):
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عنوان المؤتمر:
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The
Academy of Dental Materials 2014 Annual Meeting
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تاريخ الإنعقاد:
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8 – 11 October 2014
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مكان
الإنعقاد:
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Bologna,
Palazzo Re Enzo, Italy
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طبيعة المشاركة:
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Poster presentation
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عنوان المشاركة:
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Effects of composition and temperature
on rheology of model resin-composites
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ملخص المشاركة:
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Purpose
To study the effects of i) different bis-GMA and TEGDMA ratios,
ii) filler loading and iii) temperature (25 ˚C and 37 ˚C) on the rheological
properties of model resin-composites.
Materials
and Methods
Nine model resin-composites with different ratios of Bis-GMA and
TEGDMA, and different filler loading (50-70% w/w) were prepared (Table 1) and
studied using a parallel plate Rheometer. Shear sweep measurements were made
to determine each composite’s viscosity over the angular frequency range of ω
= 0.1–100 rad/s. Data were analysed using one way ANOVA, Dunnett’s post-hoc and t-independent tests
(p<0.05).
Results
Viscosity averages were calculated over the shear rate range
(Table 1). Viscosities increased as the percentage of filler loading
increased ranging between 0.32 to 135.36 Pas at 25 ˚C and 0.14 to 41.54 Pas at 37 ˚C. For the same filler load,
as Bis-GMA concentration increased, viscosity increased. Group 3C which had the highest Bis-GMA and
filler loading (both 70%) exhibited the highest viscosity at both
temperatures (p<0.05). The lowest Bis-GMA and filler loading (40% and 50%
respectively) had the lowest viscosity at both temperatures (p<0.05).
Viscosity significantly decreased with the increase in temperature for all
groups (p<0.05).
Conclusions
There
was a considerable variation in the resin-composite viscosities measured at
25 ˚C and 37 ˚C as an average value for a shear-rate sweep. Resin-composite
rheological properties are significantly affected by their (i) filler loading
and (ii) matrix composition- monomer type and ratio. As filler loading
increased, viscosity increased and as Bis-GMA ratio increased, viscosity
increased. However, as temperature increased, viscosity decreased.
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