BackgroundThis study aimed to assess the impact of theobromine and casein phospho-peptides/amorphous calcium phosphate with fluoride (CPP-ACPF) on the resin-dentine bond strength, microhardness, and dentine morphology.MethodsA total of 18 sound human molars for micro-tensile bond strength (µTBS), 20 sound human premolars for microhardness, and 30 premolars for Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) were used. Based on the pre-treatment used, teeth were split into six groups; sound dentine, demineralized dentine, and demineralized dentine treated with theobromine (Sigma Aldrich) and MI paste plus (GC International, USA) for two-time intervals; 5 min and 1 month. The bonded teeth were sectioned to produce 1 mm2resin-dentine sticks which were evaluated for µTBS using a universal testing device (Instron 3365, USA). The dentine microhardness was tested by using the Vickers microhardness tester (Nexus 4000 TM, Netherlands). The pre-treated dentine surface was examined using SEM/EDX (Neoscope JCM-6000 plus Joel benchtop SEM, Japan). µTBS results were analysed with two-way ANOVA. Microhardness and EDX results were analysed with two-way mixed model ANOVA. The significance level was set at (p ≤ 0.05).ResultsWhile both remineralizing materials at the two-time intervals demonstrated µTBS comparable to sound dentine (46.38 ± 12.18), the demineralized group demonstrated statistically the lowest µTBS (p < 0.001). Whether used for 5 min or 1 month, theobromine significantly increased the microhardness (50.18 ± 3.43) and (54.12 ± 2.66) respectively (p < 0.001), whereas MI paste only increased the hardness (51.12 ± 1.45) after 1 month (p < 0.001).ConclusionsThe pre-treatment of demineralized dentine with theobromine for 5 min or 1 month could enhance its bond strength and microhardness while for MI paste plus, only 1-month application was efficient to ensure remineralization.