Fig. 7.

Representative SEM images and energy dispersive spectroscopy (EDS) spectra (insets) obtained from stones overgrown on implants – ethylene glycol water group. (a & b) BRP-PA group: Agglomerates of calcium oxalate crystals covered the implant. In (a), calcium oxalate monohydrate (COM) crystals are prevalent, many of which are loose and random, while some are layered and in dumbbell form (arrowhead). A few large calcium oxalate dihydrate crystals (COD) crystals are present and have adopted the common habit of tetragonal bipyramid (thick arrow). In (b), the surface of the stone is compact (thick arrow), as might occur on the surface of a spherulite. Although some regions are comprised of radially arranged crystals as expected for a spherulite (arrowhead), other regions consist of less organized but densely stacked (long arrow) COM crystals. BRP organic matrix is also visible toward the interior (short arrow). (c & d) BRP-OPN group: In (c), one region consists of a compact calcium oxalate stone surface morphology (thick arrow), with more faceted COM crystals being visible internally, often forming dumbbells (arrowhead). BRP fibers are also visible (thin arrow). At higher magnification in (d), the dumbbells are seen to be comprised of stacked aggregates of thickly layered COM tablets. Scale bars are as follows: (a) 50 μm, (b) 50 μm, (c) 200 μm, (d) 100 μm