Effect of changing the horizontal angle of periapical X- ray radiation on detection of secondary caries under class II amalgam restorations:In vitro

Achieving non-invasive methods for the proper detection of secondary caries adjacent to dental restorations has a great importance. As alterations in horizontal and vertical angles of X-ray beam would affect the detection of dental caries on radiographs, this study was designed to evaluate the effect of changing the horizontal angle of X- ray on detection of dental caries adjacent to class II amalgam restorations in posterior teeth on periapical radiographs.

In this in vitro study, artificial carious lesions were prepared in axial walls of the amalgam restoration cavities in interproximal surfaces of 27 human extracted premolar teeth. Periapical radiographies with different horizontal X- ray angles were obtained, observed, and rated by 5 maxillofacial radiologists for detection of carious lesions. For each observer, the sensitivity, specificity, accuracy, PPV, and NPV of radiographs in the individual horizontal angles were calculated and compared by nonparametric Kruskal Wallis test. Interobserver agreement was assessed by fleiss’ kappa coefficient.

The highest accuracy of periapical radiographs for the detection of secondary caries of mesial dental surfaces was in 5-degree of mesial and distal X- ray angle (86.66%) and for the distal dental surfaces was allocated to 10-degree of distal X- ray angle (85.90%). Also, there was a significant difference in the accuracy between different horizontal angles (mesial and distal 0, 5, 10, 15-degree) (P=0.01). The higher agreement between observers in detecting mesial surface caries was in 10-degree of distal angle (0.86) and in detecting distal caries was in 5-degree of distal angle (0.89).

In the case of doubt in the existence of recurrent caries in the interproximal tooth surface, if the carious lesion is not visible on standard radiographic image with direct angle of X- ray, A 5- 10 degree of x- ray horizontal angle can improve the detection of secondary caries under amalgam restorations in interproximal dental surfaces.