Bonding to worn or fractured incisal edges: shear bond strength of new adhesive systems

Resin composites can be proposed for the restoration of incisal edges. If a progressive wear or an old fracture is responsible for the loss of the incisal edge, the bonding substrate is likely to be sclerotic dentin, surrounded by enamel. The purpose of the study was to measure under laboratory conditions, the shear bond strength of three adhesive systems to the enamel and dentin exposed on the edge of incisors as a result of a long-time wear or an old fracture.

Thirty extracted human incisors were selected. The teeth had to exhibit some exposed dentin on their edges, a result of old fractures or wear. The 30 specimens were randomly divided into three groups. In each group, a different adhesive system was tested for the ability to efficiently bond a resin composite restoration to the dental substrate. A three-step system (Scotchbond Multipurpose Plus), a one-bottle adhesive (Scotchbond 1), and a self-etching adhesive (Prompt-L-Pop) were compared. The shear bond strength of the restored samples was measured under a loading machine. The pattern of failure that each sample underwent as a result of loading was assessed under a stereomicroscope.

The highest values of bond strength were yielded by Scotchbond Multipurpose Plus (28.14 MPa), followed by Scotchbond 1 (16.15 MPa), and Prompt-L-Pop (9.26 MPa). These differences were statistically significant (P < .05). The most frequent pattern of failure was the combined adhesive-cohesive in resin fracture.

Adhesive systems involving phosphoric acid etching of the substrate were more dependable than a self-etch adhesive when bonding a resin composite restoration to worn or fractured incisal edges.