الفهرس 
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Abstract
The marginal fit is a crucial aspect for fixed restorations
because large marginal opening allows more plaque accumulation,
gingival sulcular fluid flow, and bone loss resulting in microleakage,
recurrent caries and periodontal disease compromising the longevity
of the restoration. Many studies have been carried out evaluating the
marginal discrepancies of single restorations fabricated using
different systems and materials.
The present investigation was designed to study the effect of
two different porcelain veneer materials - the LUMINEERS and the
IPS Empress pressable porcelain veneers and “the prep.” and “the
No prep technique” - on the marginal accuracy of the final
restorations.
A total of 15 human maxillary upper central incisors mounted in
epoxy resin blocks were constructed to represent the samples. The
samples were divided into three groups of five samples each and
group one and two represented the “prep. ” group while the third
group represented the “No-prep” group.
Group one “pressable IPS Empress Esthetic veneers”:
Teeth in this group received 0.5mm window preparation design
for porcelain laminate veneers.
Group two “LUMINEERS prep.”
Teeth in this group received 0.5mm window preparation design
for porcelain laminate veneers
Group three “LUMINEERS no-prep”:
Teeth in this group received No preparation at all to represent
the “NO prep” technique.
After preparation a poly-vinylsiloxane impression was taken for
all the samples, poured, Porcelain veneers were constructed then
each veneer cemented to its respective tooth with a dual-cured resin
cement material by the aid of a specially designed and constructed
cementing device. Then the samples were evaluated for marginal
accuracy using a scanning electron microscope to assess the
horizontal marginal gap width at six predetermined positions on each
surface of the tooth. A total of 18 measurements per veneer were
recorded. Data were collected, tabulated and statistically analyzed.
In the present study the marginal accuracy results after being
statistically analyzed revealed that the highest mean marginal gap
was obtained by the “No prep LUMINEERS” group (78.56µm)
followed by the “IPS Empress Esthetic” group (55.39µm) while the
“LUMINEERS prep.” group showed the lowest mean marginal gap
(47.28µm).
The SEM results matched the statistical results showing the
least marginal gap width with the “LUMINEERS prep. Group” followed
by “IPS Empress Esthetic group”, then the “LUMINEERS no-prep
“exhibiting variable highest gap measurements