Application of a graphene nanocoating for the management of microleakage and dentine hypersensitivity
Objectives: To successfully apply a graphene monolayer coating to dentine and investigate its sealing effect by occluding the orifices of the dentinal tubules. Also, to quantify the bonding strength between the graphene nanocoating and the underlying dentinal tissue.
Methods: Dentine discs were obtained from the crowns of intact human premolar and molar teeth. A monoatomic layer of graphene was then transferred to the surface of each dentine disc. Surface microtopography was investigated with scanning electron microscopy (SEM). The bonding strength between graphene and dentine was measured by a pull-off test according to BS EN ISO 4624:2002 using an Instron 5582. The presence of graphene on dentine before and after the pull-off test was further examined by energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy.
Results: EDS analysis confirmed that graphene was successfully transferred to the surface of dentine. Further examination with Raman spectroscopy showed characteristic peaks at 1576 cm-1 (G band) and 2675 cm-1 (2D band) matching the peaks expected in Raman spectra for the graphene monolayer. SEM examination showed dentine coated by a continuous layer of graphene masking the surface microtopography, including the orifices of dentinal tubules. The bonding strength between the graphene coating and dentine was determined by the pull-off test and was found to be 23.56 ± 1.32 MPa (n = 3), two-fold higher when compared to a reference value of 12.90 ± 0.69 MPa (n = 3) for uncoated dentine.
Conclusions: A continuous monoatomic layer of graphene was successfully transferred to dentine and a strong bond was achieved with the underlying surface. It is suggested that application of graphene to dentine can minimise its permeability by creating a physical barrier and therefore provide an alternative strategy for managing microleakage and dentine hypersensitivity.