Incomplete Total-etch / Self-etch Adhesive Polymerisation and Fluid Permeabilty

Objectives: Dentine bonding agents may be used as de-sensitizing agents. This study evaluated the hypothesis that incomplete adhesive polymerization will allow fluid permeabilty. Methods: Twenty teeth were horizontally sectioned to produce a flat occlusal surface. The adhesives selected for this study were Scotchbond 1* (group1) and One Up Bond F** (group 2): they were applied as per the manufacturer’s instructions. Five samples of each group had adhesive layers applied and light cured under a clear matrix and the adhesive layers in five teeth were light-cured with air exposure. The samples were connected to a pressure device at 40 cm H2O for 48 hr, simulating the physiologic pulpal pressure. Examination was performed using reflected light confocal microscopy. They were imaged en face and then longitudinally sectioned and imaged. Results: The samples of group 1 polymerised below the clear matrix showed no blister formation on the surface but there was evidence of interfacial irregularities after 48hrs; comparatively, group 2 showed no blister formation and minimal interfacial irregularities. With an air inhibited layer, group1 showed blister formation on the external surface and many irregularities at the interface. The samples of group 2 showed no external blisters but some interfacial irregularities. Conclusions: Permeability of an adhesive film affects the stability of the interfacial bond. Insufficient polymerisation may allow fluid flux and adhesive breakdown. This study has shown that a self etching adhesive (group 2) can resist fluid transfer from the dentine tubules better than a total-etch adhesive (group 1). Full polymerisation of the adhesive film, excluding air by using a clear matrix, greatly reduces the permeability of both adhesive systems. The use of dentine bonding agents for sealing exposed dentine tubules can be achieved with self etching systems, especially if these can be polymerised without an air inhibited layer. (*3M ESPE, USA) (**TOKUYAMA, JAPAN)