With the growing application of deep learning (DL) in dental image analysis, numerous datasets and models have been proposed. Periapical radiographs (PR), as one of the most common imaging modalities in clinical dentistry, play a critical role in endodontics. However, due to the high cost of manual annotation and interpretation challenges caused by poor projection and imaging artifacts, publicly available high-quality PR datasets remain scarce, severely limiting the development of DL-based PR analysis models that rely on large-scale annotated data. To address this issue, we introduce PRAD++, a large-scale PR analysis dataset annotated by clinical experts, consisting of 10,000 PR images with multi-level annotations, including 9 pixel-level segmentation categories and 17 image-level classification labels. Building upon PRAD++, we propose PRNet++, an end-to-end PR analysis network. The framework leverages the Multi-scale Wavelet Convolution (MWCN) network and the Channel Fusion Attention (CFA) mechanism to effectively model and integrate multi-scale features. In addition, an Expert Prior Injection (EPI) loss is designed to incorporate domain-specific dental knowledge into the learning process, refining classification predictions based on segmentation outputs to ensure accuracy and clinical interpretability. Extensive experiments on the PRAD++ dataset demonstrate that PRNet++ consistently outperforms state-of-the-art (SOTA) methods, achieving an average DSC of 81.25% for segmentation, alongside macro- and micro-averaged PR-AUCs of 66.58% and 79.10% for classification. Significantly surpassing the runner-up, PRNet++ exhibits enhanced robustness and interpretability in clinically challenging categories. Furthermore, comprehensive ablation and visualization analyses validate the efficacy of individual components and the parameter sensitivity of the EPI loss.

In medical images, various types of lesions often manifest significant differences in their shape and texture. Accurate medical image segmentation demands deep learning models with robust capabilities in multi-scale and boundary feature learning. However, previous models still have limitations in addressing the above issues. The majority of medical image segmentation networks exclusively learn features in the spatial domain, disregarding the abundant global information in the frequency domain. This results in a bias towards low-frequency components, neglecting crucial high-frequency information. To address these problems, we introduce SF-UNet, a spatial-frequency dual-domain attention network. It comprises two main components: the Multi-scale Progressive Channel Attention (MPCA) block, which progressively extract multi-scale features across adjacent encoder layers, and the lightweight Frequency-Spatial Attention (FSA) block, with only 0.05M parameters, enabling concurrent learning of texture and boundary features from both spatial and frequency domains. We validate the effectiveness of the proposed SF-UNet on three public datasets. Experimental results show that compared to previous state-of-the-art medical image segmentation networks, SF-UNet achieves the best performance, and achieves up to 9.4% and 10.78% improvement in DSC and IOU. Codes will be released at https://github.com/nkicsl/SF-UNet.

Germectomy is a common surgery in pediatric dentistry to prevent the potential dangers caused by impacted mandibular wisdom teeth. Segmentation of mandibular wisdom teeth is a crucial step in surgery planning. However, manually segmenting teeth and bones from 3D volumes is time-consuming and may cause delays in treatment. Deep learning based medical image segmentation methods have demonstrated the potential to reduce the burden of manual annotations, but they still require a lot of well-annotated data for training. In this paper, we initially curated a Cone Beam Computed Tomography (CBCT) dataset, NKUT, for the segmentation of pediatric mandibular wisdom teeth. This marks the first publicly available dataset in this domain. Second, we propose a semantic separation scale-specific feature fusion network named WTNet, which introduces two branches to address the teeth and bones segmentation tasks. In WTNet, We design a Input Enhancement (IE) block and a Teeth-Bones Feature Separation (TBFS) block to solve the feature confusions and semantic-blur problems in our task. Experimental results suggest that WTNet performs better on NKUT compared to previous state-of-the-art segmentation methods (such as TransUnet), with a maximum DSC lead of nearly 16%.