الفهرس 
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Abstract
Glass ionomer cements have gained popularity in the last few
years, combining the advantages of being aesthetic, adhesive,
biocompatible, and an anticariogenic material.
Poor mechanical properties of these materials have limited there use
in many clinical situations and made them prone to failure under stress. Early
moisture sensitivity is thought to be one of the reasons for physical and
mechanical properties deterioration, among some of the undesirable
properties poor surface roughness and low flexure strength. However, glass
ionomer surface protection seemed to be one of the trials or promising
solutions to limit these drawbacks.
The aim of this study was to investigate the effect of surface
coating and storage time after simulated mechanical tooth brushing on the
flexure strength and surface roughness of both conventional and resin
modified glass ionomer cement.
A total of 180 specimens were used in this study (120 specimens
for flexure strength test were prepared in split stainless steel mold
measuring 25 mm length, 2 mm width and 2 mm thickness, and 60 for
surface roughness test were prepared in cylindrical, split Teflon mold
measuring 5 mm internal diameter and 3 mm thickness). The specimens
were divided into equal two main groups (60 each for flexure strength and
30 each for surface roughness) according to the glass ionomer materials
used. Each of the above main groups was divided into two equal
subgroups (30 each for flexure strength and 15 each for surface
roughness) according to the application of surface protective coat G-Coat
Plus. Each of the above subgroups was further subdivided into 3 equal subdivisions (10 each for flexure strength and 5 each for surface
roughness) according to the storage time 24 hours, 3 months and 6
months. The specimens of the surface roughness were measured using
surface roughness testing machine peizo electric type, while specimens of
the flexure strength were measured using universal testing machine.
Three-Way ANOVA analysis of variance was used to test the
effect of GI, surface coating, immersion time and their interaction on
surface roughness and flexure strength.
Results: regarding flexure strength, for both coated and uncoated
specimens the Fuji II LC displayed the highest statistically significant
mean flexure strength at 24 h, 3 m and 6 m compared to Fuji IX
specimens. Surface coating had a statistically significant effect on the
flexure strength of the Fuji II LC at 24 h and 6 m while on the Fuji IX it
had a statistically significant effect only at 24 h. Immersion time had no
statistically significant effect on the flexure strength of the Fuji II LC
coated and uncoated at 24 h, 3 m and 6 m, on the other hand Fuji IX
coated 24 h specimens displayed the highest statistically significant effect
on the flexure strength while the Fuji IX uncoated 3 m specimens
displayed the highest statistically significant results. Regarding surface
roughness, there was no statistically significant difference between Fuji II
LC and Fuji IX coated samples at 24 h, 3 m and 6 m, while the Fuji II LC
uncoated specimens had the lowest statistically significant difference at
24 h compared to the Fuji IX uncoated specimens at 24 h, surface coating
had no statistically significant effect on the Fuji II LC and the Fuji IX at
24 h, 3 m and 6 m., concerning the immersion time, 6 m had the highest statistically significant mean values compared to the 24 h and the 3 m for
both Fuji II LC and Fuji IX coated and uncoated specimens.