الفهرس 
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Abstract
The aim of this study was to evaluate the effect of theobromine and casein phospho-peptides/amorphous calcium phosphate with fluoride (CPP-ACPF) on the resin-dentine bond strength and its durability, dentine microhardness, and morphology.
For the µTBS test, thirty-six recently extracted sound third molars were distributed on the 6 groups (sound dentine, demineralized dentine, and demineralized dentine treated with theobromine and MI paste plus for two-time intervals; 5 min and 1 month). The teeth had their occlusal enamel removed. Dentine was demineralized except for the sound group. Then dentine was acid etched and pre-treatment was applied to the dentine surface for either 5 minutes or 1 month followed by the bonding procedure. Half of the teeth were tested after 24 hours and the other half after 1 year. The teeth were then sectioned into 1mm2 beams and the test was performed using a universal testing machine in tensile mode. Fracture mode analysis was performed using a stereomicroscope at 40X magnification. The bonded interfaces before and after water storage were examined under a scanning electron microscope.
For the dentine microhardness testing, 20 recently extracted sound premolars were distributed into two groups according to the remineralizing agents used. Baseline measurements were done using a Vickers microhardness tester. Dentine demineralization was performed, and the testing was repeated. Remineralizing agents were applied for 5 minutes and left for 24 hours, then tested again. Dentine discs were stored for 1 month and the testing was performed once again.
For the dentine surface morphology, 12 recently extracted sound premolars were distributed into six groups as mentioned for µTBS. The dentine surface was imaged using SEM.
For the Ca/P ratio measurements, 18 recently extracted sound premolars were distributed into two groups according to the remineralizing agents used. Baseline recordings were done followed by the same sequence as mentioned in the microhardness testing.
Results of µTBS showed no difference between different groups except for the demineralized dentine group which showed significantly lower values when tested after 24 hours and after 1 year. When comparing results after 24 hours and 1 year of water storage, no difference was found.
The results of microhardness and Ca/P ratio of sound dentine were the highest and those of demineralized dentine were the lowest. Remineralization of the dentine surface with theobromine for 5 minutes or 1 month increased the microhardness and the Ca/P ratio results to values close to that of sound dentine. Remineralization with MI paste plus for 5 minutes failed to surpass the microhardness and Ca/P ratio results of demineralized dentine while remineralization for 1 month showed results comparable to that of sound dentine.