b obtained in example 1 were treated with a 5 0 w v dipotassium oxalate solution ph 9 0 using a cotton pledget for approximately 2 min next the discs were rinsed under running distilled water for 30 sec air dried and prepared for sem analysis also for comparison protect u2122 i e a 3 0 w v monopotassium hydrogen oxalate solution ph 2 0 was applied to the dentin discs both sample a and sample b obtained in example 1 for 2 min actively with a cotton pledget according to the manufacturer 39 s instructions next the discs were rinsed under running distilled water for 30 sec air dried and prepared for sem analysis the results of the sem analysis for dentin either left with the 600 grit smear layer sample a or etched with 37 v v phosphoric acid to remove the smear layer sample b and subsequently treated with the 10 w v cacl 2 solution ph 6 0 and then with 3 0 w v monopotassium hydrogen oxalate solution ph 2 0 showed copious surface crystal formation on the other hand only a relatively few calcium oxalate crystals were formed when the dentin discs both sample a and sample b were treated with only the 5 0 w v dipotassium oxalate solution ph 9.