Abstract
Aim: To determine the flexural strength of dual cured composite
resin cements polymerized with LED light and Quartz-tungsten
halogen light and to determine the effect of curing and storage time
on the flexural strength. Materials and Methods: feldspathic
porcelain (IPS InLine) used to produce uniform disc-shaped
specimens (10mm diameter and 1.5mm thickness ). An electronic
caliper was used to confirm precise specimen dimensions. Vita
shade 2A was selected. One commercial dual-polymerizing
composite resin cement was used (Variolink II; Ivoclar Vivadent ).
The resin cement was placed in brass molds 8 ×6× 2 mm in size
that lined with a teflon used to prepared the specimens to determine
flexural strength. After insertion of the resin cements a glass slab
was pressed over the mold and removed any expressed materials
around the margins of the mold. A mylar strip (0.07 mm) was used
to prevent adhesion of the resin cement to ceramic disk. Two types
of light source were used: Quartz-tungsten halogen light and LED.
The specimens divided into 8 groups (10 specimens for each). For
each light source the curing time done for 20 and 60 sec. and the
specimens either tested 15min. after curing or after 24hrs.
Measurements for the 3-point flexural strength test were performed
at a constant crosshead speed of 1 mm/min. Statistical data analysis
was performed by three-way ANOVA and Duncan Multiple Range
Tests to determine the significant group. Results: three- way
ANOVA indicated there is no statistical significant differences
between the two light sources (p>0.05), were as there is statistically
significance between the flexural strength of specimen cured for 60
sec. and tested after 24hrs more than other groups (p<0.05).
Conclusions: adequate curing time with 60sec. and instruction for
the patient not to use of the restoration until at least 24hrs after the
insertion of the restoration is advocated.
