Microorganisms are closely associated with human health, and their pathogenicity is a key factor in various infectious diseases, particularly in dentistry, where they contribute to common conditions such as dental caries, periodontitis, and oral mucosal diseases. Accurate and rapid microbial detection is crucial for early diagnosis, targeted therapy, and disease prevention. Conventional methods, including bacterial culture and molecular biological assays, offer specificity but are limited by long detection cycles, complex procedures, and dependence on laboratory conditions. Terahertz (THz) spectroscopy has emerged as a promising tool in microbial detection due to its non-ionizing nature, high sensitivity, and specific responses to water molecules and biomacromolecules. Integrating THz time-domain spectroscopy, near-field imaging, and metamaterial-enhanced techniques, studies have demonstrated the ability of this approach to effectively distinguish bacteria, fungi, and yeast, differentiate gram-positive and gram-negative bacteria, and even assess bacterial viability. Machine learning has further enhanced feature extraction and classification accuracy, and THz-based methods have shown notable advantages in multi-class microbial identification, detection of antibiotic-resistant strains, and quantitative analysis of microbial concentrations. However, current THz technologies are still constrained by strong water absorption, limited penetration depth, and the lack of standardized spectral databases. Future efforts should focus on mitigating water background interference, improving detection in complex samples, and establishing unified microbial spectral standards. This review systematically summarizes the latest advances of THz technologies in microbial detection, analyzes their mechanisms, advantages, and translational challenges, and proposes directions for future research.