Effect of xylitol chewing gum enriched with propolis on dentin remineralization in vitro

•Propolis, as a naturel product, has an effective role in dentin remineralization.•Propolis chewing gum leads to the formation of a precipitate different from apatite.•Propolis improves dentinal microhardness and promotes dentinal tubules occlusion. The aim of this study was to evaluate the efficiency of xylitol chewing gums enriched with propolis, remineralizing softly demineralized dentin in vitro. Four groups of chewing gum were developed; Group1: xylitol (1.8 %), Group2: xylitol + casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) (3%), Group3: xylitol+Hydroxyapatite (3%) and Group4: xylitol + propolis (5%). A control group was designed without chewing gum, but with artificial saliva. Sections of embedded crowns and cleaned roots of twenty five bovine incisors were demineralized in carbonated drink. Crown specimens were half-varnished. Remineralization process was run for all the dental specimens in the 4 groups with gum extracts and in the control group with artificial saliva for 20 min at 37 °C three times a day during 7 days. Mineral contents were evaluated by scanning electron microscopy with energy dispersive X-ray spectroscopy (EDX-SEM). Surface morphology and roughness were analyzed using atomic force microscopy (AFM). Micro-hardness was measured using Vickers micro-hardness tester among varnished and unvarnished sides. Calcium/Phosphate mean ratio showed a significant decrease between the control group, group1, group2 and group4. Control group and group3 were not significantly different. Micro-hardness increased significantly for all treated groups. AFM showed obstruction of dentinal tubules in all the groups and roughness decreased in the treated side of the dentin compared to the untreated side for tested groups. Xylitol chewing gum enriched with propolis showed dentinal tubules occlusion, significant improvement of micro-hardness and slight decrease in roughness. Ca/P ratio analysis suggests that a mineral compound other than hydroxyapatite is responsible of tubules occlusion.