Fig. 1

Sample preparation and POBS device. a Circular steel frame with a stem (1) to centre the dentin disc. b Schematic view of a specimen, consisting of a resin cylinder with the tooth slice on the upper surface and with the perforation centred and aligned with the axis. c Lateral view of the specimen with a metal cylinder (2) to prevent extrusion while filling the perforation. d Specimen with perforation filled with CSBC and covered with the RCI (3). e POBS device 4: upper piece holding the cylindrical punch (5), 6: lower piece—specimen holder, 7: cover, 8: hole to centre the punch during the test). f POBS device located in the testing machine (9: alignment device)