الفهرس 
Study DesignOnly 14 pages are availabe for public view
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Abstract
Glass-ionomer cements (GICs) were invented in the late 1960s, and are now widely accepted as dental restoratives. They are easily prepared by mixing a powder component with an aqueous solution and allowing the resulting paste to set and harden. However, their brittle nature and low mechanical strength are usually considered to be their most significant disadvantages.
Efforts have been made to improve the physical and mechanical properties of these materials by addition of a variety of fillers. Recently, nanoparticles such as nano- titanium dioxide and nano-hydroxyapatite have been incorporated into glass-ionomers in an attempt to enhance their physical, mechanical and antibacterial properties.
Nanotechnology is a promising molecular-level technology with several applications in scientific, industrial and medical fields. There has been a drastic evolution in recent years for restorative materials using nanotechnology. Nanotechnologies have been applied for the manufacturing of dental composites (nanocomposites), glass ionomer cements, endodontic sealers and tooth regeneration.
The present study investigated the effects of adding nano- hydroxy apatite (nano-HA) and nano- titanium dioxide (nano-TiO2) to GIC and compared with the results to a conventional GIC. The experimental GIC was prepared by mixing 5wt% of nano-HA and 5 wt% of nano-TiO2 with the powder of conventional GIC.The study consisted of in vitro evaluation of antibacterial effect against S. mutans using disk diffusion test, fluoride ion release test at 24 hrs, 48 hrs, 72 hrs, 14 days and 28 days, and compressive strength test.
Results showed that subgroup HAsm (nano-HA) and subgroup Tism (nano-TiO2) showed positive antibacterial effect against S. mutans. However, subgroup Tism (nano-TiO2) showed higher mean value of inhibition zones.
Regarding the fluoride ion release, there was a significant difference between the tested groups at all follow-up intervals.
At 24 hours, subgroup Cf (control) had the significantly highest mean value of fluoride ion release followed by subgroup Tif (nano-TiO2) and then subgroup HAf (nano-HA).
At 48 hours, 72 hours, 14 days, subgroup HAf (nano-HA) showed the significantly highest mean value for fluoride release, yet, there was no significant difference between subgroups Cf (control) and Tif (nano-TiO2).
At 28 days, subgroup HAf (nano-HA) also showed the highest value for fluoride release, this value was significantly higher than subgroup Tif (nano-TiO2), but not significantly different compared to subgroup (Cf).
The mean cumulative fluoride ion release after 28 days was highest in subgroup HAf (nano-HA) followed by subgroup Cf (control) while the lowest mean was scored by subgroup Tif (nano-TiO2).There was no significant difference between subgroups HAf (nano-HA) and Cf (control).
In compressive strength testing, stastistical analysis showed there was a significant difference between the tested groups. Subgroup Tics (nano-TiO2) had the highest mean value of CS followed by a decrease of mean at HAcs (nano-HA) while the lowest mean was recorded by subgroup Ccs (control). There was no significant difference between subgroups HAcs (nano-HA) and Ccs (control).