Mixed reality (MR) is an emerging technology which could potentially shape the future of our everyday lives by its unique approach to presenting information. Technology is changing rapidly and information can be presented on traditional computer screens following a WIMP (Windows, Icons, Menus, and Pointing) interface model, by using a head-mounted display to present virtual reality, or by MR which the process of presenting information through a combination of both virtual and physical elements. This paper classifies MR interfaces by applying a text mining method to a data base of 4296 relevant research papers published over the last two decades. The classification reveals the trends relating to each topic and the relations between them. This paper reviews the earlier studies and discusses the recent developments in each topic area and summarizes the advantages and disadvantages of the MR interface. Our objective is to assist researchers understand the trend for each topic and allows them to focus on the research challenges where technological advancements in the MR interface are most needed.