Abstract Purpose of Review Confusion exists on the correct terminology and definitions associated with biocompatibility, including terms such as toxicity, health effects, and allergies. Therefore, this review aims to provide clarity by structuring and summarizing the current terminology, outlining the existing testing methods for each concept, and offering examples within dental material groups. Recent Findings New materials, such as nanomaterials and engineered living materials (ELM), have entered the dental field, requiring a deeper understanding of their biocompatibility. Additionally, recent regulatory changes, such as the European Medical Device Regulation (EU MDR), underscore the importance of standardized terminology and testing methods in this evolving landscape. Summary Measurements in biocompatibility are essential in biomedical applications, involving the interaction between materials and living tissues (host). Testing methods include in vitro, in vivo, clinical, and ex vivo approaches. While thresholds and guidelines, such as NOEL and LOAEL, ensure safe biomaterial use, dental materials, such as alloys, polymers, ceramics, and nanomaterials, exhibit varying biocompatibility and toxicity levels influenced by factors such as release rates, degradation, and chemical interactions. Nanoparticles hold promise but raise concerns about oxidative stress and long-term health effects. Regulatory bodies (i.e., FDA and EU MDR) play crucial roles in ensuring product safety. In conclusion, the dynamic field of dental materials requires ongoing adaptation, rigorous testing, and adherence to regulations for the safe and effective use of emerging technologies in dentistry.