The effects of citric acid 50%, glumma and GC dentin conditioner on dentin were evaluated in different stages and compared to normal dentinal surface. The results obtained by SEM showed that smear layer is formed following cavity preparation can be removed by citric acid 50%. It can also widens dentinal tubules. On the other hand, glumma and GC conditioner can only remove smear layer without affecting dentinal tubules. These results were similar to the results announced by producing companies.