A disperser apparatus includes: a first disperser assembly configured to rotate around an axis; and a second disperser assembly facing the first disperser assembly. The first and second disperser assemblies each have a plurality of disperser-refiner plate segments annularly arranged. Each of the disperser-refiner plate segments includes a substrate having teeth extending from the substrate and arranged in rows disposed at radial intervals defining a dispersion section. Each tooth has a tooth height; and walls; and edges at junctions of adjacent walls. Each of the disperser-refiner plate segments further includes a refining section of refiner bars extending from the substrate, wherein adjacent refiner bars and the substrate define a groove between the adjacent refiner bars; and a plurality transition bars disposed between radially outermost teeth and the refining section.