<prompt> The mantle dentin found alon DEJ is20 μm30 μm40 μm50 μm  <response>: The mantle dentin found along the DEJ is about 20μm thick and it contains larger-diameter argyrophilic silver stained collagen fibers arranged perpendicularly to the DEJ. The circumpulpal dentin contains smaller-diameter closely packed collagen fibers. The dentin which forms after root completion is called secondary dentin. 