Tooth wear is recognized as an increasing clinical problem due to increases in life expectancy and the duration of tooth retention. The aim of this study was to assess various methods for evaluating dimensional changes in worn human incisors over different time periods. In total, 100 extracted human incisors were divided into two groups, termed “enamel” and “enamel-dentin.” The incisal edges of the teeth were abraded gradually four successive times in a specially modified mechanical two-body surface grinder. Before and after each grinding, the dimensional changes in the teeth were evaluated by an ultrasonic system, digital radiography, digital photography, and digital modeling. A digital micrometer was used as the control method. The control method and the ultrasonic system were able to diagnose worn enamel accurately and reproducibly in both the laboratory and clinical practice over different time periods to a depth of 50 µm (p < 0.01). Digital radiography, digital photography, and digital modeling methods could only diagnose dimensional differences at 100 µm or greater (p > 0.05). As a non-destructive, sensitive, and accurate method, the ultrasonic system seems to be a promising diagnostic tool for measuring early stages of tooth wear and tracking dimensional changes.