Objectives: To characterize the bonding interfaces of a calcium silicate-based restorative material (Biodentine) and CPP/ACP-modified glass ionomer with dentine. Also, this study was designed to evaluate the influence of dentine-surface treatment with poly acrylic acid on the bonding of both materials to dentine.
Methods: Sixty caries-free human molars were used in this study. Specimens were randomly divided into three groups according to type of restorative material used (n=20); calcium silicate-based (Biodentine, Septodont, France), conventional GIC Fuji VII-EP, GC Corporation, Tokyo, Japan) or CPP/ACP-modified glass ionomer (Fuji VII-EP, GC Corporation, Tokyo, Japan). Each group was divided into 2 sub-groups relative to the dentine surface treatment method (n=10); the dentine in control group was left without treatment, while the dentine surface in test groups was conditioned with poly acrylic acid (PAA) for 10s prior to the application of restorative. In each subgroup,5 specimens were double-labeled with fluorescein and rhodamine-B dyes then observed under a confocal laser scanning microscopy (CLSM). While the remaining 5 specimens were observed under scanning electron microscopy (SEM) then subjected to EDX elemental analysis.
Results: CLSM micrographs showed that the mineral rich zone (MRZ) was obvious in non-conditioned Biodentine groups compared to conditioned groups. Both GICs groups exhibited obvious ion-exchange zones. In the non-conditioned Biodentine groups, polygonal crystal deposition was noticed beneath the hybrid layer. These findings were confirmed by the outcome of micromorphological analysis of restoration/tooth interface using SEM.
Conclusions: Calcium silicate-based restorative material has a great affinity to exchange ions with tooth substrate and to bond chemically with dentine. The results of this study showed that calcium silicate-based restorative material (Biodentine) can be applied directly on dentine surface without any pre-surface treatment.