Bonding effectiveness of the universal adhesive on caries-affected dentin of deciduous teeth

Abstract The aim of this study was to investigate the bonding effectiveness of the universal adhesive on caries-affected dentin and normal dentin of deciduous teeth. We collected 12 extracted second deciduous molars with adjacent caries on one side. Each tooth was divided into two parts: the carious half was grouped into the caries-affected (CAD) group, whereas the other half was allocated to the normal dentin (ND) group. In the CAD group, carious tissue was removed using a slow-speed ball drill under the indication of the caries maker. In the ND group, dentin was prepared to the similarly deep level. The Single Bond Universal adhesive system using self-etch strategies was applied following the manufacturer's instructions. The defective area was filled with a resin composite Shofu Beautifil II Namer. Electron microscope observation indicated that CAD was partially demineralised and the surface was rougher than ND after acid etching. Transmission electron microscopy images of CAD showed that the hydroxyapatite platelets were distributed sparsely in strips, whereas normal dentin was intact. There was no significant difference between the CAD group and ND group in microtensile bonding strength and failure mode analysis (P > 0.05). What's more, the morphology of hybrid layer was similar in two groups. In conclusion, caries-affected deciduous tooth dentin can achieve similar bonding strength to normal dentin with the application of Single Bond Universal adhesive.