Oral Lactobacilli and salivary acidic proline-rich proteins (APRP-1/2) in dental caries.

A previous study shows that levels of acidic salivary proline-rich phosphoproteins-1/2 (APRP-1/2) increase with caries severity. The aim of this study was to examine whether this relationship also depends on the presence of H2O2-producing strains of Lactobacillus spp. Adults with severe caries (decayed, missing, and filled teeth (DMFT) > 13.9, n = 28) were compared with similarly aged adults who had minimal caries (DMFT < 5, n = 20). A total of 48 samples of whole unstimulated saliva were collected in the morning and centrifuged. Lactobacillus spp. were isolated from the sediment in Rogosa agar and peroxide (H2O2) production was determined by growing the isolates on TMB-Plus agar. Salivary APRP-1/2 content in the saliva supernatant was estimated using an enzyme-linked immunosorbent sandwich assay (ELISA). Lactobacilli were present in 67% of both caries groups but were H2O2 positive only in the minimal caries group. Irrespective of the presence of Lactobacilli, the total content of APRP-1/2 proteins was 34.5 ± 4.9 ng/ml in severe caries but just under half this in minimal caries. We conclude that Lactobacillus spp. was absent from about a third of the severe and minimal caries groups, and H2O2-producing strains were present only in the minimal caries group. The severe caries group possessed twice the content of salivary APRP 1/2 proteins as the minimal caries group. The implications of these findings for caries development are discussed.