Segmentation of dental structures in panoramic radiographs is challenging due to anatomical variability, low contrast, and artifacts. We evaluate whether U-Net-based models, paired with a unified multi-strategy optimization pipeline, can deliver accurate and robust performance for this task. Using a curated dataset of 361 annotated orthopantomograms (OPGs), we benchmark five architectures: Vanilla U-Net, Attention U-Net, UNet++, SegNet, and TransUNet, and apply a single pipeline that combines CLAHE, edge enhancement, denoising, stochastic augmentation, and boundary-aware loss optimization to emphasize crisp boundaries and stable predictions. In our comparative evaluation, U-Net variants consistently lead. Vanilla U-Net achieves 91.38% Dice and 84.13% IoU, while UNet++ achieves 91.06% Dice and 83.59% IoU; thus, Vanilla U-Net is ahead by 0.32% in Dice and 0.54% in IoU, and both outperform the non-U-Net baselines. Step-wise ablation quantifies the marginal contribution of each strategy (∆Dice/∆IoU) and shows that the entire pipeline sharpens the boundaries and stabilizes performance in variations in image quality, patient age, and tooth count. Taken together, our comparisons and ablations establish U-Net variants augmented by our pipeline as a strong, reproducible baseline for panoramic dental segmentation and a reliable foundation for future model development.