Evaluation of the efficacy of gamma value changes on detection of proximal recurrent caries in digital bitewing radiograph

Today, most digital imaging systems make available a various type of image processing techniques. Hence, the purpose of the present study is to compare the digital Bite-Wing radiographic function with the image's gamma value changes (image gamma is a functional digital imaging feature, so that the image contrast is selectively increased in bright or darker areas by changing the gamma value of the image).

In this laboratory study, a cavity was created for class II amalgam restoration at both proximal surfaces of 80 healthy premolar teeth. Caries lesions were artificially in each tooth and repaired with amalgam. Digital radiographs are processed in three gamma modes (low, medium and high).Then, recurrent caries in conventional digital radiograph with low, medium and high gamma values were investigated by two radiologists with at least 2 years of work experience and the obtained findings were applied in statistical analysis.

Specificity, sensitivity and overall accuracy were calculated using Kappa Test. The results of this study showed that the highest sensitivity and specificity value are related to the images with low gamma and then to medium gamma images .The lowest sensitivity and specificity rate belong to the images with high gamma.

Low-gamma images used to identify proximal recurrent caries can be adopted as a processing filter and images with medium and high gamma also help us to recognize proximal recurrent caries to a lesser extent.