الفهرس 
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Abstract
Summary
This study was conducted to evaluate the color stability and degree of conversion of an amine-free dual cured resin cement (Variolink Esthetic DC) compared to its light cured counterpart (Variolink Esthetic LC) and an amine-containing dual cured resin cement (Variolink N DC) used with two different translucencies of lithium disilicate ultra-thin ceramic veneers (IPS e.max CAD). A total of 120 specimens were prepared, 60 bovine bonded ceramic specimens were prepared for evaluation of color stability and 60 specimens for assessment of degree of conversion. For each test specimens were divided into three main groups according to resin cement type (n=20); G1: amine-free dual cured, G2: light cured and G3: amine-containing dual cured. Each group was further subdivided according to ceramic translucency into two subgroups high translucency (HT) and low translucency (LT) (n=10). Color stability was assessed by spectrophotometer before and after 5000 cycles of thermocycling at 5ºC and 55ºC.
ATR-FTIR was used to assess the degree of conversion. Each resin cement specimen was measured after curing through the ceramic disc without cementation at three different time intervals (immediately after curing, after 24 hours and after 2 weeks). Statistical analysis was performed using a two-way ANOVA for color stability test and three-way mixed model ANOVA for degree of conversion test results. Comparison of simple main effects was done using one-way ANOVA with Bonferroni correction. The significance level was set at P≤0.05.
The results of this study showed that G3 amine-containing dual cured resin cement (Variolink N DC) had significantly higher color change values for both ceramic translucencies than the other tested cements (P≤0.05). Color change mean values for G3 were above acceptability thresholds (AT) and therefore considered clinically unacceptable (ΔEab 4.55±0.36 and 3.88±0.48 and ΔE00 3.56±0.30 3.08±0.30) for high translucency and low translucency ceramic specimens respectively.
Regarding ceramic translucency and its effect on color stability, high translucency (HT) ceramic specimens had significantly higher color change mean values than low translucency (LT) ceramic specimens in all tested groups.
For the degree of conversion results, both the type of resin cements and time revealed significant effect on DOC% however, ceramic translucency showed no statistically significant effect on DOC%. G3 amine-containing dual cured resin cement (Variolink N DC) showed significantly lower mean DOC values (%) for both ceramic translucencies compared to the other tested groups (P≤0.05). The highest DOC% records were shown after 2 weeks followed by 24 hours while immediately after curing records revealed the lowest mean DOC value