The diagnostic evaluation of all the periapical radiographs used the following standards. Direct restorations, such as composite, cement or amalgam restoration, were diagnosed independently from its location, shape and radiopacity in one category as illustrated in Figure 1 a. Indirectly manufactured crowns—detectable as ceramic, porcelain fused to metal or metal crowns—were scored in an additional category (Figure 1 b). Further distinctions between restorative materials or insufficiencies [12 (link),13 (link),14 (link)] were not made in this study. Root canal fillings were recorded independently from the filling material (Figure 1 c). In addition, in this category, no differentiation between a sufficient (full-length, complete and homogenous definitive root canal filling) or an insufficient root canal filling (e.g., over- and underfilling, inconsistencies or voids) was made [15 (link)]. The image set further contained images with implants from several manufacturers (Figure 1 d). Again, each of the abovementioned categories was chosen when at least one dental finding was detectable. This resulted in a dichotomous decision for each restorative procedure. Again, a distinction between different restorative or root canal filling materials, implant types and qualities was not performed.
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