الفهرس 
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Abstract
This randomized controlled in vitro study was conducted to evaluate and compare the effect of application of Er,Cr:YSGG laser irradiation alone, CPP-ACP (GC Tooth Mousse) alone and their combined use on the severity and depth of enamel WSLs.
A sample of 80 freshly extracted human premolar teeth was selected for the study according to clear selection criteria. Teeth were then examined and photographed under the stereomicroscope at the baseline. Each tooth was then assigned a unique identification number and was randomly assigned to four different groups.
group I acted as the control group which received no preventive measures, group II CPP-ACP tooth mousse was applied on teeth before induction of WSL, group III received Er,Cr:YSGG laser irradiation at sub-ablative parameters and group IV received combined Er,Cr:YSGG irradiation followed by the application of CPP-ACP mousse.
Simulation of oral environment was done where teeth were subjected to brushing and thermocycling protocols. All teeth in all groups underwent 9 separate rounds of thermocycling for 110 cycles and 800 brush strokes with a total of 7200 brush strokes and 1000 thermocycling cycles which is equivalent to oral environment for 1 year. For the acid challenge, all teeth were subjected to artificial caries. The teeth were stored in artificial saliva solution, and placed in standard Ten Cate demineralizing solution (pH 5) consisting of 2.20 mM calcium, 2.20 mM phosphate, 50mM buffer (acetic acid/K acetate) at 37°C for 1 hour every 11 hours. Teeth were cycled between artificial saliva and Ten Cate demineralizing solutions for 35 days to perform the acid challenge with each group in a separate container.
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Teeth were washed and dried, then inspected visually and photographed using stereomicroscope to assess the severity of white spot lesion formation. Then the teeth were sectioned longitudinally in a bucco-lingual direction using a diamond disk under water cooling until a thickness of 150μm was reached. Sections were examined under polarized light microscope to obtain average lesion depth for each section. The largest and smallest lesion depths in the lesion were measured and the average depth was calculated accordingly. Statistical analysis was performed.
The stereomicroscopic examination showed that after induction of the WSLs, in the control group (group I) 16 teeth were scored 3 showing WSLs with cavitation and 4 teeth were scored 2 showing excessive WSLs formation. On the other hand, the CPP-ACP group (group II) showed statistically significant difference in the severity of WSLs formation when compared to the control group having 10 teeth with no visible WSLs, 9 teeth scored 1 showing slightly visible WSLs, only 1 tooth with excessively visible WSLs and no teeth in this sample showed WSLs with cavitation. Regarding the Er,Cr:YSGG group (group III), it showed statistically significant difference in the severity of WSLs from the control group, and higher severity but statistically insignificant difference when compared to the CPP-ACP group. Eight teeth showed no visible WSLs formation, 9 teeth scored 1 showing slightly visible WSL, 3 teeth showed excessively visible WSLs and again no teeth in the sample showed WSLs formation with cavitation. Also increased surface roughness was reported in the laser group in comparison to the other 3 groups. Finally, the combined used of laser and CPP-ACP (group IV) showed a statistically significant difference in WSLs severity when compared to all other 3 groups where 18 teeth scored 0 with no visible WSLs formation, only 2 teeth showed slightly visible WSLs and no teeth in this sample showed either excessive WSLs formation nor cavitation.
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The polarized light microscope examination, after simulation of the oral environment equivalent to one year, showed that the control group had the deepest lesion depth followed by the laser group, then follows the CPP-ACP group and the least lesion depth was found in the combined use of laser and CPP-ACP group (328.56μm±127.99m, 180.45μm±24.27m, 168.48μm±28.84 and 24.5 μm±8.6m, respectively).
The CPP-ACP (group II) and the laser (group III) resulted in 48.7% and 45% less lesion depth respectively when compared to the control group. A statistically significant difference was found when comparing each group of them to the control group, however no statistically significant difference was found between the CPP-ACP group alone and the laser group alone. On the other hand, the combined use of laser and CPP-ACP resulted in 92.5% less lesion depth when compared to the control group. A statistically significant difference was found between it and the control group as well as the CPP-ACP group alone and the laser group alone.