How can I differentiate between dental e-dentulous and dentulous trays?

Shape. Edentulous trays look, well, like the inside of a denture. The tissue facing side is rounded. Dentulous trays are more rectangular in shape and allow for the height of teeth in their structure. They less closely resemble the shape of a dental arch without teeth. Combo trays also exist for impressions of arches that are missing some but not all teeth.