الفهرس 
Assessment of Surface Roughness and Color Stability of glazed versus polished pressed zirconia reinforced lithium silicate restorations under different pH oral media (An In-Vitro Study
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Abstract
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ENGLISH SUMMARY
The use of all-ceramic restorations has evolved because of their excellent esthetics,
biocompatibility and enhanced strength. Recently, zirconia reinforced lithium silicate glass ceramic
has been introduced to the dental market. This new glass ceramic is enriched with zirconia (10% by
weight).
The current invitro study assessed Effect of the surface finish protocol of zirconia reinforced
lithium silicate ceramics on the surface roughness & color stability under different PH oral media.
Thirty surfaces of (n=30) pressed zirconia reinforced lithium silicate samples were tested ,
samples were fabricated and divided into two main groups (n=15) according to surface finish
protocol; glazed group and polished group. then each group were further subdivided into three
subgroups according to the media tested (n=5): Artificial saliva, coffee, carbonated orange juice. A
cylinder of 10 mm diameter and 6.5 mm length was designed using Exocad software. five cylinders
were milled from Cad wax blank. then the cylinders were invested for wax burnout procedure then
pressing of zirconia reinforced lithium silicate were made. Each ceramic cylinder was cut into three
samples with 1.5 mm thickness using isomet 4000. All the discs were finished with fine grit diamond
stone on both sides then glazed on one side and polished on the other side resulting in 15 glazed and
15 polished surfaces. a marginal notch with a diamond stone was made on the side that will receive
polishing to be able to differentiate between the polished and the glazed sides. Standardized polishing
of the samples was made on a dental surveyor. Then the surface roughness was measured using optical
profilometer quantitatively and with scanning electron microscope qualitatively and color were
measured using spectrophotometer. Then samples were immersed in the aging solutions for 12 days
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simulating 1 year in vivo. The surface roughness and color stability were remeasured after aging. the
results were analyzed using Graph Pad Instat (Graph Pad, Inc.) software for windows. A value of P
< 0.05 was considered statistically significant. Continuous variables were expressed as the mean and
standard deviation. After homogeneity of variance and normal distribution of errors had been
confirmed, one-way ANOVA was done for compared surfaces.
For surface roughness results, regardless to surface finish protocol, the difference between
immersion solutions was statistically non-significant (P= 0.2059>0.05) as indicated by two-way
ANOVA where (Coffee ≥ Fanta ≥ AS).also , irrespective of immersion solutions the difference
between surface finish protocol was statistically non-significant (P= 0.5209 >0.05) as indicated by
two-way ANOVA where (Glazed ≥ Polished). Regarding the color stability results, regardless to
surface finish protocol the difference between immersion solutions was non-statistically
significant(P= 0.1811>0.05) as indicated by two-way ANOVA where (Coffee > Fanta > A.S),
furthermore, irrespective of immersion solutions the difference between surface finish was
statistically significant (P= 0.0004<0.05) as indicated by two-way ANOVA where (Glazed
>Polished).
Based on the findings of the present study and within its limitations, it was concluded that
Surface finish protocol (glazed vs. polished) as well as tested immersion media(artificial saliva,
coffee &carbonated orange juice) showed no effect on the surface roughness of zirconia reinforced
lithium silicate ceramics. Also, Color stability of zirconia reinforced lithium silicate ceramics was
significantly affected by the surface finish protocol. While the pH immersion media showed no
effect on the color stability. Moreover , Coffee produced significant color change with the glazed
ZLS group compared to polished group with both values were above the clinically acceptable limit
(∆E˃3.7). Finally , no significant direct linear correlation was found between surface roughness and
color stability of zirconia reinforced lithium silicate ceramics.