الفهرس 
IntroductionOnly 14 pages are availabe for public view
Abstract
This study was conducted to evaluate the effect ofthe
thickness of the material being cured and distance from light cure
on the relative microhardness of three bulk filling resin composite
materials.A total of 90 composite resin samples were prepared for
this study. They were divided into three main groups (n=30)
according to the bulk fill composite used. Each was further
classified into 2 subgroups (n=15) according to the thickness of
sample. Each subgroup was further classified into 3 classes (n=5)
according to the distance between the tip of the light cure to the
under surface of composite samples.Microhardness evaluation of
samples from each group used for the experiment was performed
utilizing Vickers hardness testing. Five hardness measurements
were taken across the top and bottom surfaces using a 500 g load
for 15 s.
The results of this study showed that all the three variables
tested had influence on the depth of cure of composite resin. Both
X-tra base bulk-fill and Filtek bulk fill showed higher bottom to
top microhardness ratio compared to TetricEvoCeram Bulk Fill.
The two millimeter thickness for all materials showed higher
mean bottom to top microhardness ratio than that of the four
millimeter. None of the three materials tested exceeded the 0.8
ratio which is considered by authors as the minimum accepted
bottom to top microhardness ratio when cured in four millimeter
increments. Regarding the three distances evaluated, both the zero
and five millimeter showed higher depth of cure than that of the
ten millimeter.
Summary & Conclusions
61
Conclusions:
Within the limitations of this study, the following
conclusions can be drawn:
1-The depth of cure in terms of relative microhardness of
bulk fill composite resin is affected by composite resin
material, increment thickness and the distance between
light cure tip and composite resin.
2- Two millimeter thick increments achieve better depth of
cure than that of the four millimeter for bulk fill composite
resins.
3-Increasing the distance between the tip of light cure and
composite resin causes a decrease in the depth of cure of
bulk fill composite resins.
Recommendations:
Independent investigations studying the effect ofCuring time of
bulk fill composite resin on the depth of cure would be beneficial
in better understanding their properties and to enhance their
clinical results