Position Weighted Convolutional Neural Network for Unbalanced Children Caries Diagnosis

Panoramic radiograph is one of the most widely used inspection tools for dentists making caries diagnosis, especially for teeth that are hard to be diagnosed through visual inspection. Recently, several deep learning methods, e.g., based on convolutional neural network (CNN) or transformer network, have been proposed for automatic caries diagnosis on dental panoramic radiographs, and promising results have been achieved. However, current approaches use all the teeth equally when training their models, which results in performance degeneration because of unbalanced classification difficulties for different tooth positions. The objective of this study is to introduce a position weighted CNN to alleviate the above problem for more accurate caries diagnosis. The position weighted module evaluates and revises the output of a specially designed CNN to incorporate position information. In addition, a novel data augmentation method is used to balance data with uneven decayed and normal teeth, which is one of the reasons leading to unbalanced classification difficulty. To verify the proposed method, a children panoramic radiograph database is collected and labeled with more than 6,000 teeth. The proposed approach outperforms the state-of-the-art caries diagnosis methods with the accuracy, precision, recall, F1 and area-under-the-curve being 0.8859, 0.8875, 0.8932, 0.8903 and 0.9315, respectively. Specially, the proposed model displays higher diagnosis performance compared with two attending doctors with more than five-year clinical experience but with different diagnosis patterns, showing a potential tool for assisting dentists.