Objectives
Identifying additional information obtained by X-rays combined with clinical examination concerning primary caries, caries adjacent to restorations and quality of restorations.

Material and methods
A total of 240 adult patients, equally distributed in gender and six age-groups, were randomly selected from an original study population of 4,402 subjects (DANHES). Clinical and radiographical registrations on occlusal and approximal surfaces in posterior teeth were categorized into unrestored surfaces (sound/primary caries) and restored surfaces (without/with caries adjacent to restorations). Material and quality of restorations were also recorded. Chi-square and Fisher-exact tests were used for statistical analyses.

Results
Of potentially 11,520 surfaces, 3,015 occlusal and 5,112 approximal surfaces were analysed. Occlusal: Of 907 unrestored surfaces, 110 had primary caries and 53% were detected radiographically. A total of 183 of 2,108 restored surfaces had caries adjacent to restorations, and 99% were found radiographically. A total of 190 restorations were over/under-extended, and 89% were registered radiographically. Approximal: Of 2,649 unrestored surfaces 648 had primary caries, and 92% were registered radiographically. A total of 565 of 2,463 restored surfaces had caries adjacent to restorations, and 99% were found radiographically. A total of 638 restorations were over/under-extended, and 98% were found radiographically. For all restorations, material and depth influenced quality of restorations and incidence of caries adjacent to restorations. At least one independent variable (gender/age group/tooth-type/jaw/side/mesial-distal surface) influenced frequencies of primary caries, caries adjacent to restorations and quality of restorations.

Conclusions
First-time clinical examination must be supplemented with X-rays to obtain a complete impression of caries status in posterior regions regarding diagnostics of caries, assessment of lesion depth and quality of restorations.