الفهرس 
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Abstract
This study was conducted to assess the the preventive and remineralizing efficacy of Zinc-Carbonate Nano-Hydroxyapatite (ZnCO3/n-Hap) versus Amorphous Calcium Phosphate-Stannous Fluoride (ACP-SnF) on enamel of primary teeth. The assessment was done using SEM/EDX, FTIR and microhardness.
One hundred twenty recently exfoliated, caries-free primary anterior teeth were collected from the outpatient clinic, Pediatric Dentistry Department, Faculty of Dentistry, Ain Shams University. Teeth were extracted either for shedding or orthodontic reasons. Teeth were cleaned from organic debris and stored in deionized water until used.
Teeth were carefully examined under good illumination (dental unit illumination) Tooth was excluded if any of the following was present: caries, discoloration, white/brown spot lesions, cracks, enamel defects and fluorosis. Acrylic blocks were fabricated with a 4*4mm window exposing the labial surface of each tooth.
Test products were commercially available toothpastes with either ZnCO3/n-HAp or ACP-SnF as active ingredients. Dentifrice slurry was prepared in 3:1 ratio of deionized water to dentifrice. Dentifrice slurry, demineralizing and remineralizing solutions were freshly prepared before each pH cycle.
The teeth were divided into two main groups according to the aim, group A (remineralizing efficacy) and group B (protective efficacy). The groups were further subdivided according to the tested agent used (ZnCO3/n-HAp, ACP-SnF and control). In each subgroup, 10 teeth were tested for mineral content change (SEM/EDX and FTIR) and 10 teeth were tested for microhardness.
The mineral content was assessed by SEM/EDX, (where it measured the Calcium/Phosphorus ratio) and FTIR, measuring the mineral content of the hydroxyapatite crystal (Carbonate B/Phosphate)
In group R, baseline readings were recorded, all samples were demineralized for 96 hours. Readings were recorded after demineralization. The samples then entered a 7-day pH cycle, using the tested toothpastes in their corresponding groups during the pH cycle and the control group entered the pH cycle with no toothpaste used (acid challenged only). Final readings were recorded and the change in mineral content and microhardness measurements were assessed and statistically analyzed.
In group P, baseline readings were recorded, samples were not demineralized. The samples entered a 7-day pH cycle, using the tested toothpastes in their corresponding groups during the pH cycle and the control group entered the pH cycle with no toothpaste used (acid challenged only). Final readings were recorded and the change in mineral content and microhardness measurements were assessed and statistically analyzed.
The results of this study revealed that in group R, The highest mean value of Ca/P ratio change was found in (Zn/Co3 NHA) followed by (ACP SnF) the lowest mean value of Ca/P ratio change was found in (Control).
The highest mean value of CO3 B/ PO4 ratio was found in Zn/Co3 NHA group, followed by ACP-SnF and the lowest mean value of CO3 B/ PO4 ratio was found in Control (negative change)
The highest mean value of microhardness was found in (ACP-SnF) (192.13 ± 77.55) followed by (Control) (124.61 ± 71.37), the lowest mean value of microhardness was found in (Zn/Co3 NHA) (81.09 ± 44.16).
Regarding group P, the highest mean value of Ca/P ratio change was found in (Control) followed by (ACP SnF) the lowest mean value of Ca/P ratio change was found in (Zn/Co3 NHA). The highest mean value of CO3 B/ PO4 ratio change was found in (ACP-SnF) followed by (Control) the lowest mean value of CO3 B/ PO4 ratio change was found in (Zn/Co3 NHA).
Regarding the microhardness in group P, the highest mean value of microhardness was found in (ACP SnF) (174.77 ± 68.56) followed by (Control) (170.87 ± 52.34), the lowest mean value of microhardness was found in (Zn/Co3 NHA) (85.65 ± 61.21).
In other words, we can say that in group R, the Biorepair® group had the highest mean value of Ca/P ratio change, exceeded the baseline Ca/P with 6.67%, while, the Carbonate B/PO4 increased by 25.9254% after ph cycling, exceeding the baseline level by 17.4615%. and it showed the least microhardness readings While, in the Enamelon® group, the Ca/P increased intermediately after ph cycling, yet, exceeded the baseline with 0.01%, while the Carbonate B/PO4 decreased by 9.71% after ph cycling, (18.4232% less than the baseline). And it showed the highest mean value of microhardness
And in group P, the Biorepair® group had the lowest Ca/P, highest Carbonate B/PO4 content (decreased by 13.24%) and the least microhardness. While, Enamelon®group had intermediate Ca/P increase, lowest level of Carbonate content (decreased by 55%) and the highest microhardness readings.