Cohesive Failure

Failure mode where separation occurs within one of the bonded materials (adhesive layer or substrate) rather than at the interface, indicating that internal cohesion is weaker than the interfacial bond.

A failure mode in bonded or layered systems where separation occurs through the bulk of the adhesive, coating, or substrate material (i.e., within one of the adherends) rather than at the adhesive–substrate interface; cohesive failure indicates that interfacial adhesion exceeds the cohesive strength of one of the adherend materials or layers, and is characterized by fracture surfaces that show mat

Fracture or breakage that occurs within a single material (restorative material, luting cement, or native tooth hard tissue) rather than at the interface between two bonded materials; the failure surface traverses the bulk of the material.