When restoring deciduous teeth with extensive lesions, preformed stainless steel crowns are increasingly used in addition to resin-based materials. The aim of the present clinical study was to examine the influence of composites and stainless steel crowns on the cariogenic bacteria S. mutans and Lactobacilli by means of a commercially available salivary test (CRT® bacteria) in 100 children. For 50 children (30 boys, 20 girls, mean age 5.7 ± 2.4 years) only composites have been used as a restorative material (an average of 9 fillings per child, total number: n=450), which had been in situ for an average of 15.9 months at the time of the examination. In another group of 50 children (33 boys, 17 girls, mean age 5.9 ± 2.5 years), stainless steel crowns and composites have been used for restorations (an average of 3.5 stainless steel crowns per child, total number: n=174, an average of 7 composite fillings per child, total number n=348), which had been in place for a mean period of 17.2 months. The salivary examination of the children with composite restorations showed a high proportion of patients (64%, n=32) with high numbers (>=10 5) of S. mutans and Lactobacilli (54%, n=27). Only 22% (n=11) of the children with additional stainless steel crown restorations were found to have high numbers (>=10 5) of S. mutans and Lactobacilli (34%, n=17). This study shows a potential positive inhibitory effect of stainless steel crown restorations as compared to composite fillings with respect to the oral bacterial colonization. Keywords: restorations of the primary dentition, composite, preformed steel crowns, salivary tests