The objective of this investigation was to observe the impact of altering surface topography on the biaxial flexural strength (BFS) of four dental ceramics namely Chameleon (CH), Mirage (MI), Optec-HSP (OP) and Flexoceram (FL). A hundred and sixty samples (sixteen groups of ten discs 12´3mm) were fabricated and fired according to the suppliers' procedures.  Ten samples of each material were exposed to three surface treatments, polished, grit blasted and etched with 10% hydrofluoric acid (HF) for 30 s and 2 min.  Some samples were gold coated for investigation using Back Scattering Imaging (BSI) and Scanning Electron Microscope (SEM).  BFS was evaluated using Lloyd M5K universal testing machine at a cross-head speed of 0.5 mm/min. The statistical results of differences between groups were determined using  one-way ANOVA. The results acquired exhibited that the only significant difference in the BFS was the 10% HF for CH, OP, and FL (One-way ANOVA, P<0.05).  The decrease in BFS is most likely due to an increased surface flaw size, such that surface initiated crack growth dominates over the bulk internal flaw size of the dental porcelains. The BFS of dental porcelain examined in this investigation may be administrated either by the internal or surface flaws depending on the manner of surface groundwork.  Specimens etched with 10% HF (2 min) became weaker for CH, OP and FL ceramics.