Observer variation in the assessment of resin composite

Objectives. The aim of this study was to compare the type of information obtained from log-linear modelling vs Cohenʹs kappa statistics on observer variation in the assessment of marginal adaptation in composite inlays and amalgam restorations. Methods. Marginal adaptation of Class II resin composite inlays and amalgam restorations was clinically assessed by two observers, four years after placement. Each of 52 patients received 4 different restorations, three composite (Herculite XR, Clearfil CR Inlay and Visiomolar) inlays and one Tytin restoration. The results were evaluated by Cohens Kappa statistics and log-linear modelling. Results. The overall Cohenʹs kappa was 0.45, ranging from poor to good for the four materials. Log-linear modelling confirmed that the observers agreed beyond chance but this agreement depended on the performance of the material. Marginal adaptation of Visiomolar (ESPE) inlays was somewhat inferior compared to the other materials. The assessment of Clearfil CR (Kuraray) inlay was difficult using this clinical evaluation procedure. Significance. Using log-linear modelling it is possible to look at observer agreement and material performance at the same time. This combined approach is important because agreement may depend on material performance.