Fig. 5

a–c Compressive strength test. a The sample was secured so that the holes did not contact the load surface. b Representative load-displacement curve of the compressive strength test. The solid line shows the load-displacement curve of D-L spacer and the dotted line shows that of PMMA spacer. These curves indicate the failure mechanisms. c Compressive strength of the D-L spacer (black triangle) and PMMA spacer (black circle). Dotted and solid bars show the averages of compressive strength of PMMA and D-L spacers, respectively. Compressive strength was significantly greater (P < 0.01) in the PMMA spacer than in the D-L spacer