Comparison of biofilm models for producing artificial active white spot lesions.

OBJECTIVE: This study compared three protocols for developing artificial white spot lesions (WSL) using biofilm models. METHODOLOGY: In total, 45 human enamel specimens were sterilized and allocated into three groups based on the biofilm model: Streptococcus sobrinus and Lactobacillus casei (Ss+Lc), Streptococcus sobrinus (Ss), or Streptococcus mutans (Sm). Specimens were incubated in filter-sterilized human saliva to form the acquired pellicle and then subjected to the biofilm challenge consisting of three days of incubation with bacteria (for demineralization) and one day of remineralization, which was performed once for Ss+Lc (four days total), four times for Ss (16 days total), and three times for Sm (12 days total). After WSL creation, the lesion fluorescence, depth, and chemical composition were assessed using Quantitative Light-induced Fluorescence (QLF), Polarized Light Microscopy (PLM), and Raman Spectroscopy, respectively. Statistical analysis consisted of two-way ANOVA followed by Tukey's post hoc test (α=0.05). WSL created using the Ss+Lc protocol presented statistically significant higher fluorescence loss (ΔF) and integrated fluorescence (ΔQ) in comparison to the other two protocols (p<0.001). RESULTS: In addition, Ss+Lc resulted in significantly deeper WSL (137.5 µm), followed by Ss (84.1 µm) and Sm (54.9 µm) (p<0.001). While high mineral content was observed in sound enamel surrounding the WSL, lesions created with the Ss+Lc protocol showed the highest demineralization level and changes in the mineral content among the three protocols. CONCLUSION: The biofilm model using S. sobrinus and L. casei for four days was the most appropriate and simplified protocol for developing artificial active WSL with lower fluorescence, higher demineralization, and greater depth.

In Vivo Rodent Models for Studying Dental Caries and Pulp Disease.

Dental caries is an infectious oral disease caused primarily by complex interactions of cariogenic oral flora (biofilm) with dietary carbohydrates on the tooth surface over time. Streptococcus mutans and Streptococcus sobrinus (S. mutans and S. sobrinus) are the most prevalent cariogenic species within the oral biofilm and considered the main etiological agents of caries. Pulp exposure and infection can be caused by trauma, carious lesion, and mechanical reasons. Pulp response to these exposures depends on the state of the pulp as well as the potential bacterial contamination of pulp tissue. Herein, we describe the process of using two in vivo rodent models to study the progression of dental caries and pulp disease: a nutritional microbial model and a pulp disease induction model. The progression of the carious lesion and pulpal infections in both models was assessed by micro-CT imaging and histomorphometric analysis. Moreover, the pulp disease induction models can be used to compare and assess the antibacterial and reparative properties of the different pulp capping materials.

Antimicrobial effects of the ginsenoside Rh2 on monospecies and multispecies cariogenic biofilms.

AIMS: To investigate the effects of the ginsenoside Rh2 on monospecies and multispecies cariogenic biofilms and explore the mechanism of the antibiofilm effect of Rh2 in vitro. METHODS AND RESULTS: Streptococcus mutans, Streptococcus sobrinus and Streptococcus sanguinis were chosen to form the monospecies or multispecies biofilms. Crystal violet staining and laser scanning confocal microscopy were used to observe the effect of Rh2 on biofilms in vitro. Cytotoxicity was examined by the Cell Counting Kit-8. The effects of Rh2 on bacterial membranes were observed via transmission electron microscopy (TEM). The isobaric tags for relative and absolute quantification (iTRAQ) method were used to profile the common differentially expressed proteins. Gene expression was analysed by reverse transcription quantitative polymerase chain reaction. In general, the treatment of cariogenic biofilms with Rh2 significantly decreased biomass accumulation by inhibiting bacterial growth and extracellular polysaccharide synthesis without any cytotoxic effects. TEM imaging showed that Rh2 could disrupt the cell membranes of these bacteria. The iTRAQ results indicated that the levels of mannose-specific IIC/D and acetaldehyde/alcohol dehydrogenase were substantially down-regulated, while the mRNA expression of the corresponding genes were significantly changed. CONCLUSIONS: Our data revealed a potential application for Rh2 in the protection against dental caries via the inhibition of cariogenic biofilms. SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes the first application of a ginsenoside against multispecies cariogenic biofilms. Rh2 may serve as an alternative agent to prevent dental caries by effectively modulating the pathogenic potentials of oral biofilms.

Antimicrobial and Antibiofilm Activities of Sulfated Polysaccharides from Marine Algae against Dental Plaque Bacteria.

Dental plaque biofilms cause various dental diseases; therefore, inhibiting the growths of the dental plaque bacteria which produce biofilms can be a strategy for preventing dental disease. Certain sulfated polysaccharides from marine algae exert antimicrobial activities against human bacterial pathogens in addition to their physiological benefits. On the basis of these observations, the antimicrobial and antibiofilm activities of sulfated polysaccharides from different marine algae were evaluated against dental plaque bacteria. Among the sulfated polysaccharides, a fucoidan from Fucus vesiculosus showed notable antimicrobial activities against the selected dental plaque bacteria, including some foodborne pathogenic bacteria. The minimum inhibitory concentrations were of 125 to 1000 µg mL-1. Regarding the antibiofilm activity, the fucoidan at the concentrations of above 250 µg mL-1 completely suppressed the biofilm formations and planktonic cell growths of Streptococcus mutans and S. sobrinus. However, no eliminative effect on the completed biofilm was observed. The fucoidan consisted of almost fucose base polysaccharide containing approximately 14.0% sulfate content. The average molecular weight of the fucoidan was changed by heat treatment (121 °C for 15 min) and it affected the antimicrobial activity.

Bacterial reduction in sealed caries lesions is strain- and material-specific.

Sealing can arrest caries lesions. We aimed to evaluate if sealing effects and kinetics are bacterial-strain and sealing-material specific. Human dentin discs were mounted in a dual-chamber device. Caries lesions were induced chemically and contaminated with either Lactobacillus rhamnosus (LR) or Streptococcus sobrinus (SS). For (1) kinetics assessment, the initial bacterial load and the sealing period were varied, and lesions sealed using a self-etch adhesive and composite. For (2) comparing materials, six sealing protocols (#1-#6) were evaluated: 1# Self-etch adhesive plus composite placed without a liner, or #2 calcium hydroxide, or #3 mineral trioxide aggregate, or #4 Biodentine liners; #5 antibacterial adhesive plus composite; #6 glass ionomer cement. Pulpal fluid flow was simulated during sealing. The outcome was the number of surviving bacteria (CFU) per g dentin. For LR, bacterial survival increased significantly with increasing initial bacterial load and decreased with longer sealing periods. The relative reduction followed a first-order kinetics. More LR survived under calcium hydroxide or MTA than other materials (p < 0.001). For SS, nearly no bacteria survived sealing regardless of sealing period, initial bacterial load or sealing material. In conclusion, sealing effects and kinetics were strain- and material-specific.

Penetration of Streptococcus sobrinus and Streptococcus sanguinis into dental enamel.

The aim of this pilot study was to assess the difference in virulence of acidogenic and aciduric oral streptococci in an in vitro caries model using their penetration depths into dental enamel. 30 caries-free extracted molars from 11- to 16-year-olds were cleaned ultrasonically for 1 min with de-ionized water and, after air-drying, embedded in epoxy resin. After 8-h of setting at room temperature, the specimens were ground on the buccal side with SiC-paper 1200 (particle size 13-16 µm). Enamel was removed in circular areas sized 3 mm in diameter; the mean depth of removed enamel was 230 ± 60 µm. 15 specimens each were incubated anaerobically under standardized conditions with 24 h-cultures of Streptococcus sanguinis 9S or Streptococcus sobrinus OMZ 176 in Balmelli broth at 37 ± 2 °C; the pH-values of the broths were measured at the beginning and end of each incubation cycle. After 2, 4, 6, 8, and 10 weeks 3 teeth each were fixed in 2.5% glutaraldehyde in cacodylate buffer for 24 h, washed 3× and dehydrated 30-60min by sequential washes through a series of 30-100% graded ethanol. The teeth were cut in half longitudinally; afterward, two slits were made to obtain fracture surfaces in the infected area. After critical-point-drying the fragments were gold-sputtered and viewed in a scanning electron microscope at magnifications of ×20-20,000. After 10 weeks of incubation, penetration of S. sanguinis of 11.13 ± 24.04 µm below the break edges into the enamel was observed. The invasion of S. sobrinus reached depths of 87.53 ± 76.34 µm. The difference was statistically significant (paired t test: p = 0.033). The experimental penetration depths emphasize the importance of S. sanguinis versus S. sobrinus in the context of the extended ecological plaque hypothesis.

Adhesion of mutans streptococci to self-ligating ceramic brackets: in vivo quantitative analysis with real-time polymerase chain reaction.

OBJECTIVE: To analyze in vivo mutans streptococci (MS) adhesion to self-ligating ceramic brackets [Clarity-SL (CSL) and Clippy-C (CC)] and the relationships between bacterial adhesion and oral hygiene indices. MATERIALS AND METHODS: Four central incisor brackets from the maxilla and mandible were collected from 40 patients (20 patients per each bracket type) at debonding immediately after plaque and gingival indices were measured. Adhesions of Streptococcus mutans, S. sobrinus, and total bacteria were quantitatively determined using real-time polymerase chain reaction after genomic DNA was extracted. Factorial analysis of variance was used to analyze bacterial adhesion to the brackets with respect to the bracket type and jaw position. Correlation coefficients were calculated to determine the relationships of bacterial adhesion to oral hygiene indices. RESULTS: Adhesion of total bacteria and S. mutans to CSL was higher than that to CC (P < 0.001). Adhesion of total bacteria to the mandibular brackets was higher than that to the maxillary ones (P < 0.001), while adhesion of S. mutans to the maxillary brackets were higher than that in the mandibular ones (P < 0.001). In particular, the proportion of S. mutans to total bacteria in CSL was higher than CC (P < 0.05) in the maxillary anterior teeth (P < 0.001). There were no significant differences in adhesion of S. sobrinus between the brackets and jaw positions. Interestingly, no significant relationships were found between bacterial adhesions and oral hygiene indices. LIMITATIONS: Complex bracket configurations may significantly influence bacterial adhesion to orthodontic brackets. Further in vivo study using bracket raw materials will help to define the relationships between bacteria adhesion and enamel demineralization. CONCLUSIONS: Because oral hygiene indices were not significantly correlated with adhesions of MS to self-ligating ceramic brackets, careful examinations around the brackets should be needed to prevent enamel demineralization, regardless of oral hygiene status.

Comparative short-term in vitro analysis of mutans streptococci adhesion on esthetic, nickel-titanium, and stainless-steel arch wires.

OBJECTIVE: To test the hypothesis that there are no differences in mutans streptococci (MS) adhesion between esthetic and metallic orthodontic arch wires based on their surface characteristics. MATERIALS AND METHODS: Surface roughness (Ra) and apparent surface free energy (SFE) were measured for six wires-four esthetic, one nickel-titanium (NiTi), and one stainless-steel (SS)-using profilometry and dynamic contact angle analysis, respectively. The amount of MS (Streptococcus mutans and Streptococcus sobrinus) adhering to the wires was quantified using the colony-counting method. The surfaces, coating layers, and MS adhesion were also observed by scanning electron microscopy. Statistical significance was set at P < .05. RESULTS: The Ra values of the esthetic wires were significantly different from one another depending on the coating method (P < .05). The NiTi wire showed the highest SFE, followed by the SS wire and then the four esthetic wires. The NiTi wires produced a significantly higher MS adhesion than did the SS wires (P < .05). The esthetic wires showed significantly lower MS adhesions than did the NiTi wire (P < .05). Pearson correlation analyses found moderate significant positive correlations between the SFE and the S mutans and S sobrinus adhesions (r  =  .636/.427, P < .001/P  =  .001, respectively). CONCLUSIONS: The hypothesis is rejected. This study indicates that some esthetic coatings on NiTi alloy might reduce MS adhesion in vitro in the short term.

Adhesion forces and composition of planktonic and adhering oral microbiomes.

The oral microbiome consists of a planktonic microbiome residing in saliva and an adhering microbiome (the biofilm adhering to oral hard and soft tissues). Here we hypothesized that possible differences in microbial composition of the planktonic and adhering oral microbiome on teeth can be related to the forces by which different bacterial species are attracted to the tooth surface. The relative presence of 7 oral bacterial species in saliva and biofilm collected from 10 healthy human volunteers was determined twice in each volunteer by denaturing-gradient-gel electrophoresis. Analysis of both microbiomes showed complete separation of the planktonic from the adhering oral microbiome. Next, adhesion forces of corresponding bacterial strains with saliva-coated enamel surfaces were measured by atomic force microscopy. Species that were found predominantly in the adhering microbiome had significantly higher adhesion forces to saliva-coated enamel (-0.60 to -1.05 nN) than did species mostly present in the planktonic microbiome (-0.40 to -0.55 nN). It is concluded that differences in composition of the planktonic and the adhering oral microbiome are due to small differences in the forces by which strains adhere to saliva-coated enamel, providing an important step in understanding site- and material-specific differences in the composition of biofilms in the oral cavity.

Monitoring the prevalence of viable and dead cariogenic bacteria in oral specimens and in vitro biofilms by qPCR combined with propidium monoazide.

BACKGROUND: Streptococcus mutans and Streptococcus sobrinus are associated with the development of dental caries in humans. However, previous diagnostic systems are unsuitable for monitoring viable cell numbers in oral specimens. Assessing the relationship between the numbers of viable and dead bacterial cells and oral status is important for understanding oral infectious diseases. Propidium monoazide (PMA) has been reported to penetrate dead cells following membrane damage and to cross-link DNA, thereby inhibiting DNA amplification. In the present study, we established an assay for selective analysis of two viable human cariogenic pathogens, S. mutans and S. sobrinus, using PMA combined with real-time PCR (PMA-qPCR). RESULTS: We designed species-specific primer sets for S. mutans and S. sobrinus, generated standard curves for measuring cell numbers, and evaluated the dynamic range of the assay. To determine the effectiveness of the assay, PMA was added to viable and autoclave-killed cell mixtures. PMA treatment effectively prevented DNA amplification from dead cells. No amplification of DNA from dead cells was observed in these organisms. In addition, we applied this assay to analyze viable cell numbers in oral specimens. A significant correlation was found between the number of viable S. mutans cells in saliva and that in plaque among caries-free patients, whereas no correlation was observed between saliva and carious dentin. The total and viable cell numbers in caries-positive saliva were significantly higher than those in caries-free saliva. Finally, we analyzed the usefulness of this assay for in vitro oral biofilm analysis. We applied PMA-qPCR for monitoring viable S. mutans cell numbers in vitro in planktonic cells and oral biofilm treated with hydrogen peroxide (H2O2). In planktonic cells, the number of viable cells decreased significantly with increasing H2O2 concentration, whereas only a small decrease was observed in biofilm cell numbers. CONCLUSIONS: PMA-qPCR is potentially useful for quantifying viable cariogenic pathogens in oral specimens and is applicable to oral biofilm experiments. This assay will help to elucidate the relationship between the number of viable cells in oral specimens and the oral status.

Adhesion and biofilm formation by oral streptococci on different commercial brackets.

AIM: To compare early bacterial adhesion and biofilm formation in vitro by different oral streptococci on a variety of commercial brackets. METHODS: Adhesion and biofilm formation in vitro of 6 Streptococcus spp. on 15 different commercial brackets, in standard culture medium and in human saliva were evaluated by the MTT reduction assay. RESULTS: Significant differences were evidenced in both early adhesion and biofilm formation among the studied brackets and between the two conditions of growth. Gold brackets resulted less prone to colonisation compared to composite brackets. The growth rates of the tested species on the different tested materials were significantly different. CONCLUSION: The adopted experimental plan, dissecting the two phases of plaque formation on different brackets in different conditions, showed that composite brackets are more susceptible to adhesion and colonisation by streptococci, while the remaining tested brackets did not show differences that could be clinically relevant. Data suggest that different personal behaviours affecting the oral environment could significantly affect colonisation of brackets by oral streptococci.

Adhesion of Streptococci to various orthodontic composite resins.

BACKGROUND: This investigation aimed to determine quantitatively the adhesion of Streptococcus mutans and Streptococcus sobrinus to orthodontic composite resins that were tested simultaneously using radio-markers. METHODS: Seven orthodontic composite resins were classified into seven groups: BeautyOrtho Bond (GI), Blugloo (GII), Enlight (GIII), Grengloo (GIV), Kurasper F (GV), Transbond CC (GVI) and Turbo Bond II (GVII). Thirty 4 x 4 x 1 mm blocks of each orthodontic composite resin were made (a total of 210 blocks). Both Streptococcus species were cultivated independently. For the quantitative analysis, radioactive markers were used to codify the bacteria ((3) H for Streptococcus mutans and (14) C for Streptococcus sobrinus). The blocks were submerged in a solution with microorganisms previously radiolabelled for 2 hours at 37 °C in constant movement. The blocks were placed in a combustion system to quantify the Streptococcus adhering to the surface of the materials by capturing the residues and measuring the radiation. RESULTS: Significant differences in bacterial adhesion were found among the groups. The lowest significant scores for both microorganisms were observed in GIII. CONCLUSIONS: The orthodontic composite resin evaluated in GIII exhibited the lowest adhesion of Streptococcus mutans and Streptococcus sobrinus, which may reduce enamel demineralization and the risk of white spot lesion formation.

Mode of delivery, mutans streptococci colonization, and early childhood caries in three- to five-year-old Thai children.

OBJECTIVE: To investigate whether mode of delivery is associated with mutans streptococci (MS) colonization and early childhood caries (ECC) in preschool Thai children. METHODS: Three hundred and fifty mothers and their 3- to 5-year-old children (184 born vaginally and 166 born by Caesarean section) participated in the study. Data included a dental examination, MS colonization assessed by the Dentocult(®) SM Strip Mutans method, and a questionnaire survey of family socio-demographic information, as well as children's birth history, dietary habits, and oral health practices. RESULTS: Overall, ECC prevalence was 56% in 3-year-old and 78% in 5-year-old Thai children. Compared to children delivered by C-section, vaginally born children experienced increased ECC prevalence (73.8% versus 59.6%; P = 0.009) and were more likely to have higher MS scores (OR = 1.8, 95% CI = 1.1-2.9), adjusting for mother's gestational age, MS score, feeding practice habits; child's age and tooth brushing habits. Children's MS scores were highly correlated with their mothers' MS scores (P < 0.001). Additionally, children's age, MS colonization, and mothers' prechewing feeding habits were the most significant risk indicators for ECC in Thai children. CONCLUSION: Our findings suggest that mode of delivery is significantly correlated with MS colonization and caries outcomes in young Thai children. Future studies are needed to further understand the possible biological mechanisms linking mode of child delivery to the colonization of cariogenic microbiota and development of ECC.

Effects of Withania somnifera on the growth and virulence properties of Streptococcus mutans and Streptococcus sobrinus at sub-MIC levels.

The aim of this study was to evaluate the effect of the methanol extract of Withania somnifera (MEW) on the growth and virulence properties of Streptococcus mutans and Streptococcus sobrinus at sub-minimum inhibitory concentration (MIC) levels and to identify the main components of MEW. First, antibacterial activity of MEW against oral bacteria was determined using a micro-dilution method. Then, the effect of MEW on the growth of S. mutans and S. sobrinus was investigated at sub-MIC levels. To test the effect of MEW on the virulence properties of S. mutans and S. sobrinus, assays for acid production, acid tolerance, and biofilm formation were performed at sub-MIC levels. A GC-MS analysis for the main components of MEW was also carried out. MEW showed a broad antibacterial range against oral bacteria (MIC: 0.125-2 mg/mL). At sub-MIC levels, MEW dose-dependently increased doubling times of S. mutans and S. sobrinus up to 258% and 400%, respectively. Furthermore, MEW inhibited acid production, acid tolerance, and biofilm formation of S. mutans and S. sobrinus at sub-MIC levels. The GC-MS analysis revealed the presence of mono- and disaccharides, sugar alcohols, and organic acids as main components. These data suggest that MEW might be useful for restraining physiological activities of cariogenic bacteria.

Bifidobacterium animalis subsp. lactis BB-12 administration in early childhood: a randomized clinical trial of effects on oral colonization by mutans streptococci and the probiotic.

A randomized clinical trial studied the effects of early administration of Bifidobacterium animalis subsp. lactis BB-12 (BB-12) on oral colonization of (1) mutans streptococci (MS), and (2) BB-12. In this double-blind, placebo-controlled study, infants (n = 106) received probiotic bacteria (BB-12 group), xylitol (X group), or sorbitol (S group). Test tablets were administered twice a day (from the age of 1-2 months) with a novel slow-release pacifier or a spoon (daily dose of BB-12 10(10) CFU, polyol 200-600 mg). Samples were collected from mucosa/teeth at the age of 8 months and 2 years for BB- 12 determination (qPCR) and plate culturing of MS (MSB, TYCSB), lactobacilli (Rogosa) and yeasts (Sabouraud). The MS levels of the mothers were determined (Dentocult SM Strip Mutans). The baseline characteristics of the three groups were similar. Mean duration of tablet delivery was 14.9 ± 6.7 months. In all groups, >90% of the mothers showed high MS counts (log CFU ≥5). MS colonization percentages of the children at the age of 2 years were rather low (BB-12 group: 6%; X group: 31%; S group: 10%; p < 0.05). The levels of lactobacilli and yeasts did not differ between the groups. BB-12 cell counts barely exceeding the detection limit were found in three of the oral samples of the 8-month-old children; however, the 2-year samples did not contain BB-12. The early administration of BB-12 did not result in permanent oral colonization of this probiotic or significantly affect MS colonization in the children.

Antimicrobial activity of Bifidobacterium spp. isolated from healthy adult Koreans against cariogenic microflora.

OBJECTIVE: Dental caries is the main common infectious disease in the human oral cavity. Streptococcus mutans and Streptococcus sobrinus were reported to be the most important etiological factors in human dental caries. Thus, we examined the inhibitory effects of Bifidobacterium spp. cells and culture supernatants against S. mutans and S. sobrinus, including Streptococcus gordonii, and Aggregatibacter actinomycetemcomitans, which is associated with periodontal disease. METHODS: Mutans streptococci or A. actinomycetemcomitans and lactic acid bacteria (LAB) were mixed in 1:1 ratio and then incubated for 90 min at 37°C. After the incubation, the viability of mutans streptococci or A. actinomycetemcomitans was determined by plate count technique. We also investigated the morphological changes of S. mutans treated with LAB using scanning electron microscopy (SEM). RESULTS: In vitro viability of S. mutans, S. sobrinus, S. gordonii, and A. actinomycetemcomitans was affected by human intestinal LAB identified as Bifidobacterium adolescentis SPM1005 and Bifidobacterium longum SPM1207. Especially, B. adolescentis SPM1005 cells at 1.0 × 10(8) CFU had a strong growth-inhibiting effect against S. mutans and induced a 64% loss of its viability (p<0.05). In addition, swollen and disrupted S. mutans were observed after incubation with B. adolescentis SPM1005. However, the culture supernatant of this strain did not show such inhibitory activity. CONCLUSION: B. adolescentis SPM1005 cells decreased the growth of S. mutans, which is a risk factor for dental caries. Therefore, we suggest that this Bifidobacterium strain may be a useful probiotic microorganism for prevention of dental caries that does not have adverse effects.

An artificial biofilm induced secondary caries model for in vitro studies.

BACKGROUND: The aim of this study was to establish a new in vitro model for biofilm induced secondary caries studies using an oral biofilm reactor. METHODS: An approximately 2 × 3 × 2 mm(3) sized dentino-enamel Class I cavity was prepared in the middle of a square-shaped specimen from the mid-labial portion of bovine incisors. The cavities were partially filled with either Clearfil AP-X with SE-Bond or Clearfil AP-X without any bond. Artificial biofilms were then formed on the resin composite filled surfaces using three species of oral bacteria in an oral biofilm reactor for 20 hours followed by 7- or 30-day incubation periods. RESULTS: The lesions were clearly visible on fluorescence microscopy and by scanning electron microscopy in the enamel at the interface of resin restorations in all samples. The data from image analysis showed that the lesion size was largest in the No-bond samples with statistically significant differences (p < 0.05). Demineralization along the cavity wall extended deeper in No-bond compared to SE-Bond samples and penetration was significantly deeper in No-bond 30-day samples. CONCLUSIONS: A primary artificial secondary caries model was established using biofilms for in vitro studies and the significance of using a bonding system could also be verified.

Bovine milk fermented with Lactobacillus rhamnosus L8020 decreases the oral carriage of mutans streptococci and the burden of periodontal pathogens.

AIM: The aim of this study was to find the oral isolate of lactobacilli, which has the potential to inhibit either periodontal, cariogenic, or fungal pathogens in vitro, and to examine the effects of bovine milk fermented with the isolate on the oral carriage of cariogenic and periodontal pathogens. METHODS: The inhibitory effects of the supernatant of Man-Rogosa-Sharpe broth, in which each of 42 oral isolates of lactobacilli grown, was examined. One isolate, Lactobacillus rhamnosus L8020, that showed the potential to inhibit either periodontal, cariogenic, or fungal pathogens in vitro, was used to examine the effects of fermented milk on the oral carriage of cariogenic and periodontal pathogens, which was examined by a placebo-controlled and cohort trial using 50 participants. RESULTS: Edible yogurt containing Lactobacillus rhamnosus L8020 significantly reduced the oral carriage of mutans streptococci (P < 0.01) and four periodontal pathogens examined: Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, and Fusobacterium spp. (P < 0.01), but the phenomenon were not observed with the placebo yogurt (P > 0.05). CONCLUSION: These results suggest that yogurt with Lactobacillus rhamnosus L8020 could reduce the risk of dental caries and periodontal disease.

Hydrophobicity test in mutans Streptococci

Kinetic hydrophobic measurements were performed by confronting 40 mutans streptococci from thirty 10- to 20-year-old patients with 200 ml hexadecane (Sigma). Fourteen patients had high dental caries risk (Group A), dmft + DMFT >5 with 3 or more active caries, and 16 had low dental caries risk (Group B), dmft + DMFT <3 without active caries. Twenty bacteria from Group A and 20 bacteria from Group B were typed using De La Higuera's procedure and confirmed by API strip (bio- Merieux). From the 14 patients in Group A we obtained 12 S. mutans (8 hydrophobic/ 4 non-hydrophobic), 5 S. sobrinus (4 hydrophobic/ 1 non-hydrophobic) and 3 S. rattus (hydrophobic). From the 16 patients in Group B we obtained 11 Streptococcus mutans (10 non-hydrophobic/ 1 hydrophobic), 7 Streptococcus sobrinus (6 non-hydrophobic/ 1 hydrophobic) and 2 Streptococcus rattus (hydrophobic). Patients with high dental caries risk have a higher prevalence of hydrophobic bacteria than patients with low dental caries risk (p=0.0003). All typed S. rattus were hydrophobic.

Con el objeto de evaluar una posible relacion entre hidrofobicidad y caries dental, se estudiaron 40 cepas de Streptococcus grupo mutans provenientes de 30 pacientes de entre 10 y 20 anos, 14 pacientes con tres o mas caries activas e indice ceod mas CPOD > 5 (Grupo A) y 16 pacientes sin caries activas, con ceod mas CPOD < 3 (Grupo B). Las cepas fueron aisladas a partir de muestras de saliva en AMS-BT y tipificadas por pruebas bioquimicas y API-strep realizandose la medicion cinetica de hidrofobicidad, enfrentandolas con 200 ml de hexadecano (Sigma). En el grupo A se caracterizaron 12 cepas Streptococcus mutans: 8 hidrofobicas y 4 no hidrofobicas, 5 cepas de Streptococcus sobrinus: 4 hidrofobicas y 1 no hidrofobica y 3 cepas Streptococcus rattus hidrofobicas. En el grupo B, se caracterizaron 11 cepas de S. mutans, 10 no hidrofobicas y 1 hidrofobica, 7 cepas de S. sobrinus: 6 no hidrofobicas y 1 hidrofobica y 2 cepas de S. rattus hidrofobicas. Todos los pacientes del grupo A presentaron al menos 1 cepa hidrofobica. En las cepas aisladas de estos pacientes se demostro la existencia de una alta prevalencia de Streptococcus grupo mutans con caracteristicas hidrofobicas p=0,0003. Estos resultados indicarian la relacion entre la capacidad de adherencia a hexadecano y caries activa. Todas las cepas tipificadas como S. rattus fueron hidrofobicas independientemente del grupo de origen.

Effect of biofilm on the repair bond strengths of composites.

Composite restorations degrade during wear, but it is unknown how wear affects the composite surface and influences composite-to-composite bonding in minimally invasive repair. Here, it is hypothesized that in vitro exposure of composites to oral biofilm yields clinically relevant degradation of composite surfaces, and its influence on composite-to-composite bonding is determined. Biofilms on composite surfaces in vitro increased their roughness and decreased filler particle exposure, except for a microhybrid composite, similar to effects of clinical wear in palatal appliances. Failure shear stresses after intermediate-adhesive-resin application were significantly lower after aging by in vitro exposure to biofilms, while silica-coating maintained the same failure stress levels as in non-aged composites. Failure modes were predominantly cohesive after silica-coating, while intermediate-adhesive-resin application yielded more adhesive failure. It is concluded that in vitro exposure to oral biofilm is a clinically relevant aging condition, and that silica-coating is to be preferred for the repair of aged composites.