Objective The purpose of this study was to assess the effects of differently synthesized diamonds on the flexural strength of dental resins. Methods Three groups resins were prepared in the same modify and compound process respectively with uniform quantity of detonation nanodiamond（DND）, still pressure diamond（SPD）, and polycrystalline diamond（PCD）. Resin without diamond was prepared as reference sample. Flexural strength of the four groups resins were measured by the method outlined in YY1042-2003. Results Flexural strength increases by 117.2% and 103.1% with the accession of DND and SPD. PCD unsignificantly enhances resin’s flexural strength. Conclusion Obvious increases in flexural strength are observed separately in resins with DND and SPD, and both the two flexural strengthes increase more than double; PCD has no remarkable effect on flexural strength of resin.
