Table 3.

Mean and standard deviation (SD) of flexural strength (MPa) in different hydrofluoric (HF) concentrations and etching times

Time (s)	5% HF	10% HF
20	347.53±43.63 aA	300.57±33.64 aB
60	302.27±30.85 bA	268.54±29.67 abB
120	271.99±22.29 bA	244.95±34.66 bA

Different lowercase letters indicate a significant difference (P<0.05) among etching times with the same acid concentration. Different capital letters indicate a significant difference (P<0.05) among acid concentrations at the same time point