Flexural Strength of Glass Fiber Post Following Conditioning with Various Chemical Solutions Running Title: Flexural Strength of Fiber Post with Different Chemical Treatments

The aim of this study was to assess various chemical solutions on the surfaces of glass fiber post could affect its flexural strength. A total of 80 Glass Fiber posts were divided into eight groups (n=10) based on surface treatment, untreated surface (control), 10% hydrofluoric acid (HF) for 1 minutes, 10% HF for 2 min, 24% hydrogen peroxide (H2O2) for 4 min, 24% H2O2 for 10 min, 35% H2O2 for 4 min, 35% H2O2 for 10 min, and chloroform solution for 1 hour. Fiber posts were immersed in the solutions for the required amount of time and then rinsed and dried. Fiber posts were loaded in three-point bending test using a mechanical testing machine, data recorded and Flexural strength (σ) was measured. Statistical analysis revealed that the highest value of flexural strength was shown in the group treated with 24% H2O2for 4minfollowed by Chloroform group, so they have no significant effect on flexural strength. While the least value was shown in group treated with10% HF for 2min.Treatment with HF significantly decrease flexural strength for both application times. Treatment with H2O2 showed significant decrease only in group treated with 35% H2O2 for 10 min. It was concluded that strong acid etching of HF and long application time of higher concentration of H2O2 had adverse effect on fiber post flexural strength.