Evaluation of the effect of amalgam fillings on the diagnosis of proximal caries using cone‑beam computed tomography technique

Diagnosis of dental caries using cone‑beam computed tomography (CBCT) may be hindered due to several introduced and inherent artifacts. The aim of this study was to evaluate the effect of amalgam fillings on the accuracy of diagnosis of proximal caries in CBCT.

In this in vitro study, 102 extracted human teeth (mandibular and maxillary molars and premolars) were used. Six molars were chosen for mesio‑occluso‑distal amalgam restorations. Before obtaining the CBCT images, the 96 remaining teeth were stabilized in dental sockets of six dry human skulls in a way that the proximal contacts re‑established. Thereafter, six of the molar teeth were replaced by the amalgam‑restored teeth and the second group of images was then obtained. All images were evaluated by two independent observers in the panorama view and the presence or absence of caries was recorded. For histopathologic investigations, the teeth were cut and assessed by an oral pathologist using a stereomicroscope. The McNemar test was used for comparison between CBCT assessments and histopathologic evaluations (P < 0.05 was considered statistically significant). In addition, the receiver operating characteristics curve was utilized to evaluate the diagnostic accuracy in different sections of imaging.

The result sensitivity and specificity of CBCT imaging in the first group of images before placement of the restored teeth were 0.96 and 0.36, respectively. In the second group of images after placement of the restored teeth, these values were 0.78 and 0.18, respectively. Moreover, statistical analysis showed that there is a good agreement in interproximal caries diagnosis between histopathologic and CBCT imaging findings without placement of amalgam restorations (P < 0.001). However, this agreement does not exist after amalgam restorations (P = 0.84).

Diagnosis of proximal caries using CBCT is not an efficient method where there are amalgam restorations adjacent to the suspected teeth.