The red complex, which includesPorphyromonas gingivalis,Treponema denticola, andTannerella forsythia(formerlyBacteroides forsythus), are recognized as the most important pathogens in adult periodontal disease. These bacteria are usually found together in periodontal pockets, suggesting that they may cause destruction of the periodontal tissue in a cooperative manner. This article discusses the interspecies pathogenic interactions within the red complex.

To evaluate the effects of the lactic acid bacterium Lactobacillus salivarius on caries risk factors. The study was performed in 64 healthy volunteers to evaluate the effects of L. salivarius-containing tablets on caries risk factors. The participants were divided randomly into four groups, and took tablets containing L. salivarius WB21, L. salivarius TI 2711, Ovalgen® DC (antibody against glucosyltransferase from Streptococcus mutans), or xylitol. Levels of mutans streptococci and lactobacilli, amount of salivary flow, salivary pH, and salivary buffering capacity were assessed before and after taking the tablets. Subsequently, a short-term administration trial using L. salivarius WB21-containing tablets was performed in eight healthy volunteers. The participants took L. salivarius WB21-containing tablets (2.0 × 10⁹ colony forming units/day) for 2 weeks, and the numbers of mutans streptococci in saliva were counted. The levels of mutans streptococci seemed to decrease in the L. salivarius WB21, TI 2711, and Ovalgen® DC groups compared to the xylitol group, with no significant differences between the groups. Lactobacilli levels significantly increased in the L. salivarius WB21 and TI 2711 groups compared to the other groups. Concerning salivary flow and salivary pH, no significant differences were observed between the groups. The salivary buffering capacity significantly increased in the L. salivarius TI 2711 group (P = 0.003) and Ovalgen® DC group (P = 0.002) compared to the xylitol group. The short-term administration trial showed that the L. salivarius WB21-containing tablets significantly decreased the number of mutans streptococci (P = 0.039). L. salivarius-containing tablets were suggested to increase resistance to caries risk factors. UMIN000013160 (registration date: February 14, 2014).

Objectives: It has been suggested that smoking affects the oral microbiome, but its effects on sites other than the subgingival microbiome remain unclear. This study investigated the composition of the salivary and tongue bacterial communities of smokers and nonsmokers in periodontally healthy adults.Methods: The study population included 50 healthy adults. The bacterial composition of resting saliva and the tongue coating was identified through barcoded pyrosequencing analysis of the 16S rRNA gene. The Brinkman index (BI) was used to calculate lifetime exposure to smoking. The richness and diversity of the microbiome were evaluated using thet‐test. Differences in the proportions of bacterial genera between smokers and nonsmokers were evaluated using the Mann–WhitneyUtest. The quantitative relationship between the proportions of genera and the BI was evaluated using Pearson's correlation analysis.Results: The richness and diversity of the oral microbiome differed significantly between saliva and the tongue but not between smokers and nonsmokers. The saliva samples from smokers were enriched with the generaTreponemaandSelenomonas. The tongue samples from smokers were enriched with the generaDialisterandAtopobium. The genusCardiobacteriumin saliva, and the genusGranulicatellaon the tongue, were negatively correlated with BI values. On the other hand, the generaTreponema,Oribacterium,Dialister,Filifactor,Veillonella, andSelenomonasin saliva andDialister,Bifidobacterium,Megasphaera,Mitsuokella, andCryptobacteriumon the tongue were positively correlated with BI values.Conclusions: The saliva and tongue microbial profiles of smokers and nonsmokers differed in periodontally healthy adults. The genera associated with periodontitis and oral malodor accounted for high proportions in saliva and on the tongue of smokers without periodontitis and were positively correlated with lifetime exposure to smoking. The tongue might be a reservoir of pathogens associated with oral disease in smokers.

Recently, the antibacterial activity of a composite resin containing prereacted glass ionomer (S-PRG) filler was revealed. We examined the effect of an S-PRG eluate on various biologic activities ofStreptococcus mutansandPorphyromonas gingivalis. Adherence ability ofS. mutanswas evaluated by microtiter plate assay; protease and gelatinase activities ofP. gingivaliswere examined by synthetic substrate hydrolysis and gelatin film spot assay, respectively. Coaggregation ofP. gingivaliswithFusobacterium nucleatumwas also examined. S-PRG eluate was found to suppress streptococcal adherence. S-PRG eluate inhibited the protease and gelatinase activities ofP. gingivalisand the coaggregation betweenP. gingivalisandF. nucleatum. These results indicate that S-PRG eluate suppresses streptococcal adherence and inhibits the protease and coaggregation activities ofP. gingivalis. These findings may prompt research into novel strategies for preventing caries and periodontitis.