الفهرس 
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Abstract
This study was carried out to evaluate the effect of smoking and different
beverages on the color stability of heat cure and thermoplastic denture bases using
a spectrophotometer assessment.
Poly methyl methacrylate is the most commonly used resin for denture base
fabrication as it is low cost, easy to manipulate, easy of processing and superior
esthetic. However, few undesirable properties of acrylic resin connected to
increased porosity, high water retention, volume variations and irritating effect of
the residual monomer (organic solvent, hepatotoxic), wrapping system, fracture
due to its inherent weak mechanical properties together with the polymer
development, have led to alternative thermoplastic materials.
Thermoplastic resins were introduced which are flexible biocompatible
materials to overcome too much of the limitations found in conventional acrylic
resin, since they offered better denture adaptation as well as denture retention
because of their light weight and because of engaging more desirable undercuts.
Sixty disc-shaped specimens of two different denture base materials were
prepared according to the manufacturer’s recommendations, then were divided into
two main groups: group I: which was formed of thirty disc-shaped specimens of
conventional acrylic resin (Vertex). group II: which was formed of thirty discshaped specimens of thermoplastic resin (Ultra) and immersed in three different
solutions (tea, coffee, coke), in addition to smoke chamber for 30,60 and 90 days.
Statistically significant differences were found in the color change (ÄE)
among both groups (p < 0.005) after 90 days of immersion.