Saliva Decreases Sucrose-Induced Cariogenicity in an Experimental Biological Caries Model.

OBJECTIVE: Whether a minimum quantity of saliva inhibit the caries process remains uncertain. This study aimed to investigate the impact of saliva dilutions on an in vitro caries model using Streptococcus mutans (S. mutans) biofilms. METHODS: S. mutans biofilms were cultivated on enamel and root dentin slabs, in culture media containing different proportions of saliva (v/v): 0%, 5%, 10%, 25%, 50%, 75%, and 100% saliva, and exposed to a 10% sucrose solution (5 min, 3x/day), with appropriate controls. After 5 (enamel) and 4 (dentin) days, demineralization, biomass, viable bacteria, and polysaccharide formation were analyzed. The acidogenicity of the spent media was monitored overtime. Each assay was performed in triplicate across two independent experiments (n = 6). RESULTS: In both enamel and dentin, an inverse relationship was observed between acidogenicity, demineralization, and the proportion of saliva. Even small quantities of saliva incorporated into the media led to a noticeable reduction in enamel and dentin demineralization. Saliva presence resulted in significant reductions in biomass, viable S. mutans cells, and polysaccharides, with the effects being concentration-dependent for both tissues. CONCLUSIONS: High quantities of saliva can almost completely inhibit sucrose-induced cariogenicity, while even small amounts exhibit a dose-dependent caries-protective effect.

Medium-chain fatty acids as an alternative treatment for denture stomatitis in older people.

OBJECTIVE: To determine the effect of medium-chain fatty acids (MCFA) on the severity of denture stomatitis (DS) and the counts of Candida spp. in older people (OP) wearing removable prostheses (RP). MATERIALS AND METHODS: This randomized, controlled and triple-blind study included forty-three OP presenting DS. The control group was treated with 0.12% chlorhexidine (CHX) and the experimental group with MCFA, 2 × /day for 15 days. Intraoral examination and counts of Candida spp. were performed at 0, 7, and 15 days. The differences between both groups in the decrease of the severity of DS and the viability of Candida spp. were determined clinically and microbiologically, respectively. RESULTS: OP carriers of RP treated with MCFA presented remission of the clinical signs of DS, but the Candida spp. counts only decreased significantly in the CHX-treated group at 7 days of treatment (p < 0.05). Besides, MCFA was shown to reduce the clinical signs of DS after the first week of application, while CHX after the second week. CONCLUSIONS: The MCFA is effective in reducing the clinical signs of DS associated with oral candidiasis in subjects with RP. Both treatments showed a significant decrease in severity, for MCFA after the first week and for CHX two weeks after starting the corresponding treatment. CLINICAL RELEVANCE: The MCFA is an effective, harmless, and accessible treatment alternative against DS, since it manages to reduce the severity of the lesion in the milder cases of DS in the oral mucosa of OP carriers of RP.

In Vitro Effect of Copper (I) Complex [Cu(NN1)2](ClO4) on Vibrio harveyi BB170 Biofilm Formation.

Biofilm formation in pathogenic bacteria is an important factor of resistance to antimicrobial treatments, allowing them to survive for a long time in their hosts. In the search for new antibiofilm agents, in this work we report the activity of a copper (I) complex, [Cu(NN1)2]ClO4, synthesized with Cu (I) and NN1, an imine ligand 6-((quinolin-2-ylmethylene)amino)-2H-chromen-2-one, a derivate of natural compound coumarin. The antibacterial and antibiofilm capacity was evaluated in Vibrio harveyi BB170 used as model bacteria. Antibacterial activity was measured in vitro by minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and half-maximal inhibitory concentration (IC50) determination. Antibiofilm capacity of copper (I) complex was analyzed by different concentrations of IC50 values. The results showed that the sub-IC50 concentration, 12.6 µg/mL of the copper (I) complex, was able to reduce biofilm formation by more than 75%, and bacterial viability was reduced by 50%. Inverted and confocal laser scanning microscopy showed that the [Cu(NN1)2]ClO4 complex affected the biofilm structure. Therefore, the copper (I) complex is effective as an antibiofilm compound in V. harveyi BB170.

Micro-tomographic characterization of the root and canal system morphology of mandibular first premolars in a Chilean population.

This study aimed to analyze the root anatomy and root canal system morphology of mandibular first premolars in a Chilean population. 186 teeth were scanned using micro-computed tomography and reconstructed three-dimensionally. The root canal system morphology was classified using both Vertucci's and Ahmed's criteria. The radicular grooves were categorized using the ASUDAS system, and the presence of Tomes' anomalous root was associated with Ahmed's score. A single root canal was identified in 65.05% of teeth, being configuration type I according to Vertucci's criteria and code 1MP1 according to Ahmed's criteria. Radicular grooves were observed in 39.25% of teeth. The ASUDAS scores for radicular grooves were 60.75%, 13.98%, 12.36%, 10.22%, 2.15%, and 0.54%, from grade 0 to grade 5, respectively. The presence of Tomes' anomalous root was identified only in teeth with multiple root canals, and it was more frequently associated with code 1MP1-2 of Ahmed's criteria. The root canal system morphology of mandibular first premolars showed a wide range of anatomical variations in the Chilean population. Teeth with multiple root canals had a higher incidence of radicular grooves, which were closely related to more complex internal anatomy. Only teeth with multiple root canals presented Tomes' anomalous root.

Competition and Caries on Enamel of a Dual-Species Biofilm Model with Streptococcus mutans and Streptococcus sanguinis.

Imbalances within the dental biofilm trigger dental caries, currently considered a dysbiosis and the most prevalent noncommunicable disease. There is still a gap in knowledge about the dynamics of enamel colonization by bacteria from the dental biofilm in caries. The aim, therefore, was to test whether the sequence of enamel colonization by a typically commensal and a cariogenic species modifies biofilm's cariogenicity. Dual-species biofilms of Streptococcus mutans and Streptococcus sanguinis on saliva-coated enamel slabs were inoculated in different sequences: S. mutans followed by S. sanguinis (Sm-Ss), S. sanguinis followed by S. mutans (Ss-Sm), S. mutans and S. sanguinis inoculated at the same time (Sm=Ss), and the single-species controls S. mutans followed by S. mutans (Sm-Sm) and S. sanguinis followed by S. sanguinis (Ss-Ss). Biofilms were exposed to 10% sucrose 3 times per day for 5 days, and the slabs/biofilms were retrieved to assess demineralization, viable cells, biomass, proteins, polysaccharides, and H2O2 production. Compared with Sm-Sm, primary inoculation with S. sanguinis reduced demineralization (P < 0.05). Both Ss-Sm and Sm=Ss sequences showed reduction in biomass, protein, and polysaccharide content (P < 0.05). The highest S. sanguinis viable count and H2O2 production level and the lowest acidogenicity were observed when S. sanguinis colonized enamel before S. mutans (P < 0.05). Initial enamel adherence with commensal biofilms seems to induce more intense competition against more typically cariogenic species, reducing cariogenicity.IMPORTANCE The concept of caries as an ecological disease implies the understanding of the intricate relationships among the populating microorganisms. Under frequent sugar exposure, some bacteria from the dental biofilm develop pathogenic traits that lead to imbalances (dysbiosis). Depending on which microorganism colonizes the dental surface first, different competition strategies may be developed. Studying the interactions in the entire dental biofilm is not an easy task. In this study, therefore, we modeled the interplay among these microorganisms using a caries-inducing species (S. mutans) and a health-associated species (S. sanguinis). Initial enamel adherence with S. sanguinis seems to induce more intense competition against typically caries-inducing species. Besides continuous exposure with sugars, early colonization of the enamel by highly cariogenic species like S. mutans appears to be needed to develop caries lesions as well. Promoting early colonization by health-associated bacteria such as S. sanguinis could help to maintain oral health, delaying dysbiosis.

Streptococcus mutans and Streptococcus sanguinis Expression of Competition-Related Genes, Under Sucrose.

Streptococcus mutans synthesizes 3 glucosyltransferases (Gtfs) associated with cariogenic biofilms, while commensal Streptococcus sanguinis produces only one; gtfP and hydrogen peroxide (H2O2) by SpxB. The aim was to test the hypothesis that under a sucrose-induced cariogenic challenge, the expression of competition-related genes is differentially regulated depending on whether S. sanguinis or S. mutans primarily colonize enamel. Dual-species biofilms of S. sanguinis and S. mutans were formed under different colonization sequences on enamel slabs and exposed to 10% sucrose for 5 min, 3×/day for 5 days. Biofilms were analyzed for the transcriptional response of competition-related genes encoding gtfB, gtfC, and gtfD for S. mutans and gtfP and spxB for S. sanguinis. In addition, acidogenicity (pH) and viable cells in each of the conditions were determined. For all the genes, a downregulation was observed during simultaneous colonization by both bacterial species. In contrast, gtfB was upregulated when S. sanguinis was the first colonizer (p < 0.05). Both gtfC and gtfD were upregulated during sequential inoculation with S. sanguinis as the first colonizer. An eleven-fold upregulation of gtfP was observed in biofilms with S. mutans as initial colonizer (p < 0.05), with a moderate increase in spxB expression. The lowest pH values and viable cells of S. sanguinis were observed when S. mutans first colonized the enamel slabs, compared to the other conditions (p < 0.05). Demanding sucrose-challenged oral environment requires increased expression of virulence traits to effectively compete and thrive in the dental biofilm, especially when the competitor has already colonized the ecological niche.