الفهرس 
IntroductionOnly 14 pages are availabe for public view
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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
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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
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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.
Conclusions
Within the limitations of this in vitro study, the following was concluded:
1. The resin modified glass ionomer had the better flexure strength values compared to the conventional glass ionomer at all the storage times in either coated or uncoated conditions.
2. It is necessary to protect Fuji IX during the first 24 h using resin coating to improve the flexure strength of the material.
3. Although resin coating improved the flexure strength of Fuji II LC during its storage periods, the flexure strength of Fuji IX improved by time up to 3 month storage period without using the resin coating.
4. Resin coating has no protecting effect for both Fuji II LC and Fuji IX regarding the surface roughness when the storage period increased more than 3 month.