Secondary or recurrent caries is defined as a caries lesion developing adjacent to a dental
restoration1 and is along with fracture the predominant reason for failure of posterior
restorations.2,3 It has been proposed that secondary caries lesions develop as outer lesions on
the tooth surface next to the restoration margins and as wall lesions, within the tooth/
restoration interface4,5 While wall lesion formation would occur when interfacial gaps are
present,6,7 outer lesions would develop similarly to primary caries on the tooth surface