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In this essay we propose an extension of the caries ecological hypothesis to explain the relation between dynamic changes in the phenotypic/genotypic properties of plaque bacteria and the demineralization/remineralization balance of the caries process. Dental plaque represents a microbial ecosystem in which non-mutans bacteria (mainly non-mutans streptococci and Actinomyces) are the key microorganisms responsible for maintaining dynamic stability on the tooth surface (dynamic stability stage). Microbial acid adaptation and subsequent acid selection of ‘low-pH’ non-mutans bacteria play a critical role for destabilizing the homeostasis of the plaque by facilitating a shift of the demineralization/remineralization balance from ‘net mineral gain’ to ‘net mineral loss’ (acidogenic stage). Once the acidic environment has been established, mutans streptococci and other aciduric bacteria may increase and promote lesion development by sustaining an environment characterized by ‘net mineral loss’ (aciduric stage). Hence, high proportions of mutans streptococci and/or other aciduric bacteria may be considered biomarkers of sites of particularly rapid caries progression. This cascade of events may change the surface texture of caries lesions from smooth to rough (enamel) or hard to soft (dentin). These clinical surface features can be reversed at any stage of lesion development provided that the acidogenic/aciduric properties of the biofilm are resolved. From an ecological point of view it is therefore not only important to describe which bacteria are involved in caries, but also to know what the bacteria are doing.

The aim of this study was to evaluate the effect on oral health, at age 9 years, of daily oral supplementation with the probiotic Lactobacillus reuteri, strain ATCC 55730, to mothers during the last month of gestation and to children through the first year of life. The study was a single-blind, placebo-controlled, multicenter trial involving 113 children: 60 in the probiotic and 53 in the placebo group. The subjects underwent clinical and radiographic examination of the primary dentition and carious lesions, plaque and gingivitis were recorded. Saliva and plaque were sampled for determination of mutans streptococci (MS) and lactobacilli (LB) in saliva and plaque as well as salivary secretory IgA (SIgA). Forty-nine (82%) children in the probiotic group and 31 (58%) in the placebo group were caries-free (p < 0.01). The prevalence of approximal caries lesions was lower in the probiotic group (0.67 ± 1.61 vs. 1.53 ± 2.64; p < 0.05) and there were fewer sites with gingivitis compared to the placebo group (p < 0.05). There were no significant differences between the groups with respect to frequency of toothbrushing, plaque and dietary habits, but to intake of fluoride supplements (p < 0.05). There were no intergroup differences with respect to L. reuteri, MS, LB or SIgA in saliva. Within the limitation of this study it seems that daily supplementation with L. reuteri from birth and during the first year of life is associated with reduced caries prevalence and gingivitis score in the primary dentition at 9 years of age.

Fourier transform infrared (FT-IR) and Raman spectroscopy and mapping were applied to the analysis of biofilms produced by bacteria of the genus Streptococcus. Bacterial biofilm, also called dental plaque, is the main cause of periodontal disease and tooth decay. It consists of a complex microbial community embedded in an extracellular matrix composed of highly hydrated extracellular polymeric substances and is a combination of salivary and bacterial proteins, lipids, polysaccharides, nucleic acids, and inorganic ions. This study confirms the value of Raman and FT-IR spectroscopies in biology, medicine, and pharmacy as effective tools for bacterial product characterization.

The mutans streptococci were once the primary focus of research dedicated to understanding the etiology of dental caries. That focus has now shifted to an emphasis on the ecological balances and complexities within the entirety of the plaque microbiome. Within that framework there are considerable differences of opinion regarding the importance and relative contributions of the mutans streptococci. This article explores the basis for the various viewpoints, the limitations of current knowledge, and the confounders that make it difficult to arrive at a consensus.

Objectives The aim was to evaluate the effects of orally administered Lactobacillus rhamnosus GG (LGG) and Bifidobacterium animalis subsp. lactis BB-12 (BB-12) on the number of salivary mutans streptococci (MS), amount of plaque, gingival inflammation and the oral microbiota in healthy young adults. Materials and methods The study was a randomised, controlled, double-blind trial. Healthy volunteers used lozenges containing a combination of LGG and BB-12 (test group, n  = 29) or lozenges without added probiotics (control group, n  = 31) for 4 weeks. At baseline and at the end of the test period, the plaque index (PI) and gingival index (GI) were determined, and stimulated saliva was collected. The microbial composition of saliva was assessed using human oral microbe identification microarray ( n  = 30). MS and lactobacilli (LB) were plate cultured. Results The probiotic lozenge decreased both PI and GI ( p  < 0.05) while no changes were observed in the control group. However, no probiotic-induced changes were found in the microbial compositions of saliva in either group. Conclusions The probiotic lozenge improved the periodontal status without affecting the oral microbiota. Clinical relevance Short-term consumption of LGG and BB-12 decreased the amount of plaque which was associated with a clinical impact: a decrease in gingival inflammation.

Background The purpose of the study was to investigate the effect of probiotics on biofilm acidogenicity and on the number of salivary Streptococcus mutans and lactobacilli in orthodontic patients. Methods This RCT was conducted on 28 young adults who were undergoing orthodontic treatment. The short-term prospective clinical trial lasted for three weeks. The test group rinsed daily with drops containing two Lactobacillus reuteri strains diluted in water, while the placebo group used drops without probiotics. The subjects were enrolled eight months since the beginning of orthodontic treatment. Plaque-pH, saliva and dental biofilm samples were obtained at baseline, one week and three weeks post intervention. Results Twenty-seven subjects successfully completed the trial period, only one drop out in the test group. No side effects were reported. A statistically significant increase in plaque pH at three weeks post-intervention was found for the test group ( p  < 0.05), while insignificant changes in the pH value were found for the placebo group in comparison to baseline ( p  > 0.05). In addition, the AUC 7.0 showed a significant difference at three weeks between the test and placebo ( p  = 0.00002). The three-week samples of stimulated whole saliva showed a statistically insignificant difference in the number of S. mutans and lactobacilli between the two groups ( p  > 0.05). The qPCR analysis showed the ability of the two strains to get colonized in the dental biofilm without a significant effect on the microbial counts. Conclusion/clinical implications A mixture of Lactobacillus reuteri has the ability to reduce the pH fall at the three-week follow-up. However, the short-term use of probiotics does not appear to have an effect on the number of salivary Streptococcus mutans and lactobacilli in saliva and on the dental biofilm. Trial registration Clinicaltrial.gov (Identifier: NCT04593017 / (19/10/2020)).

Objectives Systematically review the available literature regarding the caries-preventive effect of probiotics. Data, sources and study selection An electronic search was conducted in three databases (PubMed MEDLINE, ISI Web of Science and Cochrane Library) to identify all suitable studies. The outcomes had to be presented as the effect of probiotics on the incidence of caries or on the levels of mutans streptococci and/or Lactobacillus species. Human studies, written in English, with at least 15 participants, comparing a probiotic product with a placebo/no probiotic were included. Where possible, a meta-analysis was performed to obtain quantitative data. Results Since only two articles presented useful data on the caries incidence, we focused on the surrogate endpoints: mutans streptococci and/or Lactobacillus counts. The meta-analysis showed that when the probiotic and control group are compared after treatment, significantly more patients in the probiotic group had low mutans streptococci (<10 5  CFU/ml) counts and significantly less patients had high (>10 6  CFU/ml) counts. Regarding the Lactobacillus counts, comparing the probiotic and control group at the end of the probiotic use, no significant differences could be observed, neither in low (<10 4  CFU/ml) nor in high Lactobacillus (>10 6  CFU/ml) counts. Conclusions Within the limitations of the available data, it may be concluded that probiotics decrease the mutans streptococci counts. This suggests that probiotics could have a positive effect in the prevention of caries. Clinical relevance There is insufficient evidence that probiotics can prevent caries, but they can reduce the mutans streptococci counts.

Shikonin is extracted from the roots of Lithospermum erythrorhizon, and shikonin extracts have been shown to have inhibitory effects on several bacteria. However, shikonin extracts are difficult to formulate because of their poor water solubility. In the present study, we prepared a shikonin dispersion, which was solubilized by the inclusion of β-1,3-1,6 glucan, and analysed the inhibitory effects of this dispersion on Streptococcus mutans and non-mutans streptococci. The shikonin dispersion showed pronounced anti-S. mutans activity, and inhibited growth of and biofilm formation by this bacterium. The shikonin dispersion also showed antimicrobial and antiproliferative effects against non-mutans streptococci. In addition, a clinical trial was conducted in which 20 subjects were asked to brush their teeth for 1 week using either shikonin dispersion-containing or non-containing toothpaste, respectively. The shikonin-containing toothpaste decreased the number of S. mutans in the oral cavity, while no such effect was observed after the use of the shikonin-free toothpaste. These results suggest that shikonin dispersion has an inhibitory effect on S. mutans and non-mutans streptococci, and toothpaste containing shikonin dispersion may be effective in preventing dental caries.

Background Xylitol is widely used in caries prevention and has been shown to reduce cariogenic activity in children. However, limited evidence exists regarding the effectiveness of xylitol wipes in infants and toddlers. Objective To investigate the effect of xylitol wipes on cariogenic activity in infants and toddlers. Materials and methods This prospective, longitudinal, single–arm interventional study included 20 healthy, caries–free children aged 9 months to 1.5 years. Mothers were instructed to wipe their children’s teeth with xylitol wipes (Spiffies Baby Tooth Wipes™) three times daily for four weeks. Salivary samples were collected at baseline and weekly follow–up visits. Cariogenic activity was assessed by measuring lactic acid production using a chairside kit (Clinpro Cario L–Pop), and salivary mutans streptococci (MS) levels were determined using the CRT bacteria caries risk test. Results A highly significant reduction in salivary lactic acid levels was observed after one week of xylitol wipe use ( P  < 0.0001). A significant reduction in MS counts was observed by the fourth week ( P  = 0.02). Conclusions Daily application of xylitol wipes reduced cariogenic activity in young children, suggesting that this delivery method may be a practical preventive approach during early childhood. Trial registration This trial was registered at ClinicalTrials.gov (Identifier: NCT07245433) on 14 November 2025.

Objective The short-term effect (60 days) of Lactobacillus brevis CD2 lozenges vs placebo on variables related to caries and gingivitis in type 1 diabetic children was evaluated. Material and methods Eight diabetics (4–14 years old) were assigned to two groups ( n = 34 subjects each), probiotic lozenges and placebo. Stimulated saliva for microbiological analysis and plaque pH were assessed at baseline ( t 0 ), 30 days ( t 1 ), 60 days ( t 2 ) and in the follow-up period (90 days from baseline, t 3 ). Gingival status was assessed at t 0 , t 2 and t 3 . Two-way ANOVA assessed differences between groups. Results In the probiotic group, Streptococcus mutans bacterial density mean scores dropped from 3.11 ± 1.13 at baseline to 1.82 ± 0.72 ( t 2 ) and to 2.06 ± 0.56 ( t 3 ), while in the placebo group, the scores were 3.09 ± 0.8 ( t 0 ), 2.82 ± 0.47 ( t 2 ) and 3.11 ± 0.43 ( t 3 ) ( p < 0.01). Lowest and maximum pH fall increased in the probiotic group, from 5.37 ± 0.41 at baseline to 5.49 ± 0.24 at t 3 ( p < 0.01) and from 1.20 ± 0.46 to 0.98 ± 0.29 ( p = 0.02). Bleeding score decreased significantly in both groups, showing a statistically significant lower bleeding score at t 2 in the probiotic group (25.6%, 95% CI 21.5–32.7 vs 29.5%, 95% CI 25.2–34.9, p = 0.02). Conclusions Lactobacillus brevis CD2 has shown to improve caries-related risk factors and gingival health in diabetic children. Clinical relevance Lactobacillus brevis CD2 might contribute to improved oral health in type 1 diabetic children.