Research in (medical) terminological knowledge representation is showing an increased interest in the family of Description Logics (DLs), as they allow for automatic reasoning. This interest is driven by an increase in demands on the quality of and reasoning ability with medical terminological knowledge. Recent advances in Computer Science have demonstrated the computational decidability and empirical tractability of quite expressive DLs. The question arises whether this expressivity is usable and useful. This paper motivates and describes an exploratory study to address this question by examining the surplus value of individual DL constructors based on an investigation of UMLS terms. Our study indicates that the disjunction and negation operators comprise very valuable extensions to current DLs. The impact of formalization depends on the involved semantic type; "Injury and Poisoning" is one of the semantic types in which a large portion of concepts will benefit from the extension.