Cariogenic Biofilms: Development, Properties, and Biomimetic Preventive Agents

Trans, Trans-Farnesol Enhances the Anti-Bacterial and Anti-Biofilm Effect of Arachidonic Acid on the Cariogenic Bacteria Streptococcus mutans and Streptococcus sobrinus

BACKGROUND

Streptococcus mutans and Streptococcus sobrinus are Gram-positive bacteria involved in the development of dental caries, as they are able to form biofilms on tooth enamel, ferment sugars into acids, and survive under acidic conditions. This ultimately leads to a local lowering of the pH value on the tooth surface, which causes enamel cavities.

HYPOTHESIS

One measure to reduce caries is to limit the growth of cariogenic bacteria by using two anti-bacterial agents with different mechanisms of action. The hypothesis of this study was that the anti-bacterial activity of ω-6 polyunsaturated arachidonic acid (AA) against S. mutans and S. sobrinus can be enhanced by the sesquiterpene alcohol trans, trans-farnesol (t,t-farnesol).

METHODS

The anti-bacterial activity of single and combined treatment was determined by the checkerboard assay. Bacterial viability was assessed by live/dead SYTO 9/propidium iodide (PI) staining on flow cytometry. Anti-biofilm activity was determined by MTT metabolic assay, crystal violet staining of biofilm biomass, SYTO 9/PI staining by spinning disk confocal microscopy (SDCM) and high-resolution scanning electron microscopy (HR-SEM).

RESULTS

t,t-Farnesol lowered the minimum inhibitory concentration (MIC) and the minimum biofilm inhibitory concentration (MBIC) of AA at sub-MICs. AA reduced the metabolic activity of preformed mature biofilms, while t,t-farnesol had no significant effect. The enhanced anti-bacterial effect of the combined t,t-farnesol/AA treatment was further evidenced by increased PI uptake, indicating membrane perforation. The enhanced anti-biofilm effect was further verified by SDCM and HR-SEM. Gene expression studies showed reduced expression of some biofilm-related genes.

CONCLUSIONS

Altogether, our study suggests a potential use of the two naturally occurring compounds arachidonic acid and t,t-farnesol for preventing biofilm formation by the cariogenic bacteria S. mutans and S. sobrinus. These findings have implications for caries prevention.

Clinical evidence of caries prevention by hydroxyapatite: An updated systematic review and meta-analysis

OBJECTIVES

A systematic review and meta-analysis were undertaken to update our 3-year-old meta-analysis to include RCTs, in vivo, and in situ clinical evidence that showed hydroxyapatite in oral care products can reduce dental caries.

DATA

Using the PICO guide, published clinical trials were searched where subjects (P) of all ages, with primary, mixed or permanent dentitions, using toothpastes, mouthwashes or gels containing hydroxyapatite as an active ingredient (I) were compared to subjects who used placebo or no intervention, or fluoride-containing positive controls (C), and the outcomes (O) were direct measurement of reduced dental caries or suitable proxy for reduced caries risk.

SOURCES

PubMed, Scopus, EMBASE, and Web of Science databases were searched using search terms from previous searches.

STUDY SELECTION

All authors collectively agreed which studies to include after applying the exclusion/inclusion criteria. Eighteen studies were retrieved and analyzed. The studies were graded according to a National Institutes of Health grading system. Three authors decided on the final list of publications suitable for meta-analysis, and the meta-analysis was carried out using the public domain R statistical program.

RESULTS

After applying more specific inclusion criteria and assessment, out of 18 retrieved studies, 5 clinical trials and 8 in situ trials were included in the meta-analysis.

CONCLUSIONS

The evidence for the effectiveness of fluoride-free, hydroxyapatite-containing oral care products in reducing dental caries, both from RCTs and in situ clinical trials, has expanded. More studies now show that hydroxyapatite is effective as an anti-caries active ingredient in the absence of fluoride.

CLINICAL SIGNIFICANCE

As a sole active ingredient, considered safe if swallowed, hydroxyapatite is an ideal substitute for fluoride in toothpaste and mouthwash tailored for young children, and new data as presented in this review, demonstrated that hydroxyapatite-based oral care products can be used by people of all ages.

An In Vitro and In Silico Study of Luteolin-Loaded Zinc Oxide Nanoparticles: Enhancing Bioactivity and Efficacy for Advanced Therapeutic Applications Against Cariogenic Microorganisms

Introduction Recent studies have explored alternative methods to enhance caries prevention and treatment. Luteolin compound has been noted for its antimicrobial properties, while zinc nanoparticles (Zn NPs) are recognized for their potent antibacterial effects. This study investigates the synthesis, characterization, and antimicrobial efficacy of luteolin-loaded Zn oxide NPs (Luteo-ZnONPs) against cariogenic bacteria. By combining the biofilm-targeting capabilities of luteolin with the antimicrobial properties of Zn NPs, we aim to explore a novel approach for dental caries management. Methods Luteo-ZnONPs were synthesized and characterized using ultraviolet-visible (UV-vis) and Fourier transform infrared (FTIR) spectroscopy, confirming their successful formation and stability. Antimicrobial efficacy was assessed through minimum inhibitory concentration (MIC), demonstrating effectiveness against cariogenic bacteria such as Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, and Streptococcus mutans in different concentrations. The agar well plate method was employed to analyze the growth inhibitory effect of Luteo-ZnONPs (50 and 100 µg/ml, respectively). Streptomycin (100 µg/ml) was used as a positive control. The results (zone of inhibition (ZOI) in millimeter, mm) were represented as mean ± standard deviation. One-way analysis of variance (ANOVA) was employed to detect the significance (p < 0.05) between the groups. Cytotoxicity was analyzed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay against MG63 cells, and doxorubicin was used as a positive control. Wilcoxon rank test was used for the statistical method. Gyrase B was downloaded from Protein Data Bank (PDB id: 6F86) and docked against luteolin using Autodock software (version 4.2). The binding score was presented as kcal/mol in table format. Results Characterization results showed that UV-vis spectroscopy revealed characteristic peaks, indicating the successful synthesis and stability of Luteo-ZnONPs. FTIR spectroscopy confirmed the presence of functional groups from luteolin compound interacting with the Zn NPs. It showed effective inhibition against E. coli on 50 µg/ml as 12.45 mm as ZOI and increased with concentration (100 µg/ml as 17.13 mm). It showed minimal ZOI on E. faecalis (8.12, 12.21 on 50 and 100µg/ml, respectively). The cytotoxicity of Luteo-ZnONPs was lesser than doxorubicin on MG63 cells with statistical high significance (p < 0.0014). These results showed that Luteo-ZnONPs had effective antimicrobial nature against Enterococcus family. Thus, gyrase B from E. coli was selected for the molecular docking analysis. The catalytic tunnel in gyrase B (E. coli, PDB: 6F86), influenced by Luteo-ZnONPs, indicated potential for novel, broad-spectrum antimicrobials via selective inhibition at conserved active sites.  Conclusion The agar well plate and MIC confirmed that Luteo-ZnONPs exhibited potent antibacterial activity, especially at higher concentrations compared to streptomycin. One- way ANOVA demonstrated significant differences in antibacterial efficacy between treatments, validating its superior performance. Its strong interaction on in silico level showed the targeted mechanism of action. Luteo-ZnONPs showed lesser toxicity than doxorubicin on MG63 cells. These findings underscore the potential of its broad spectrum antimicrobial nature paving the way for its development into innovative, nontoxic therapeutic solutions.

Caries Etiology and Preventive Measures

Caries is a widespread disease in both children and adults. Caries is caused by the conversion of fermentable carbohydrates by plaque bacteria into acids on the tooth surface. Thus, it is important to focus on sugar reduction and plaque control. For efficient plaque removal/control, state-of-the-art toothpastes contain various active ingredients such as antimicrobial agents (e.g., chlorhexidine, stannous salts, and zinc salts), abrasives (e.g., calcium carbonate, calcium phosphates, and hydrated silica), surfactants (e.g., sodium lauryl sulfate and sodium methyl cocoyl taurate), and natural compounds (e.g., polyphenols and xylitol). Agents with pH-buffering and calcium-releasing properties (e.g., calcium carbonate and calcium phosphates) and biomimetic actives (e.g., hydroxyapatite) reverse the effects of the acids. Additionally, modern toothbrushes (i.e., electric toothbrushes) as well as dental floss and interdental brushes significantly help remove plaque from dental surfaces including interproximal surfaces. In conclusion, modern concepts in caries prevention should focus not only on tooth remineralization alone but also on the control of all the key factors involved in caries development.

Natural, biphasic calcium phosphate from fish bones for enamel remineralization and dentin tubules occlusion

OBJECTIVES

A calcium phosphate extracted from fish bones (CaP-N) was evaluated for enamel remineralization and dentinal tubules occlusion.

METHODS

CaP-N was characterized by assessing morphology by SEM, crystallinity by PXRD, and composition by ICP-OES. CaP-N morphology, crystallinity, ion release, and pH changes over time in neutral and acidic solutions were studied. CaP-N was then tested to assess remineralization and dentinal tubules occlusion on demineralized human enamel and dentin specimens (n = 6). Synthetic calcium phosphate in form of stoichiometric hydroxyapatite nanoparticles (CaP-S) and tap water were positive and negative controls, respectively. After treatment (brush every 12 h for 5d and storage in Dulbecco's modified PBS), specimens' morphology and surface composition were assessed (by SEM-EDS), while the viscoelastic behavior was evaluated with microindentation and DMA.

RESULTS

CaP-N consisted of rounded microparticles (200 nm - 1 µm) composed of 33 wt% hydroxyapatite and 67 wt% β-tricalcium phosphate. In acidic solution, CaP-N released calcium and phosphate ions thanks to the preferential β-tricalcium phosphate phase dissolution. Enamel remineralization was induced by CaP-N comparably to CaP-S, while CaP-N exhibited a superior dentinal tubule occlusion than CaP-S, forming mineral plugs and depositing new nanoparticles onto demineralized collagen. This behavior was attributed to its bigger particle size and increased solubility. DMA depth profiling and SEM showed an excellent interaction between the newly formed mineralized structures and the pristine tissue, particularly at the exposed collagen fibrils.

SIGNIFICANCE

CaP-N demonstrated very good remineralizing and occlusive activity in vitro, comparable to CaP-S, thus could be a promising circular economy alternative therapeutic agent for dentistry.

Analysis of Spatial and Biochemical Characteristics of In Vitro Cariogenic Biofilms

Background Dental caries is the most common bacterial disease of calcified tissues of teeth. Cariogenic biofilms formed on the tooth surface secrete organic acids and thus result in demineralization. Delving into the depth of biofilms is crucial to understand the pathogenic mechanisms and design improved therapeutic approaches. The aim of the study is to analyze the spatial and biochemical characteristics of cariogenic biofilms. Materials and methods Pulp tissue samples sourced from freshly extracted third molars were incubated with oral cariogenic bacteria namely Streptococcus mutans, Staphylococcus aureus, Escherichia coli, Entamoeba faecalis, and Candida albicans to form the biofilm. Spatial assessment of biofilms was done under FESEM (field emission scanning electron microscope, JSM-IT800, JEOL, Tokyo, Japan). FTIR (Fourier transform infrared spectroscopy, Alpha II, Bruker, Germany) spectra were assessed for chemical molecular interactions in 24- and 48-hour time periods.  Results Morphological assessment with FESEM revealed rapid growth and aggregation within a short time period. FTIR spectra to analyze chemical constituents of biofilm presented with varied peaks of water, amide A, amide I, water, lipids, and phospholipids. Conclusion Further validation with more advanced imaging for an extended time period is vital to derive better conclusive evidence.

Novel Remineralizing and Antibiofilm Low-Shrinkage-Stress Nanocomposites to Inhibit Salivary Biofilms and Protect Tooth Structures

Recurrent caries remain a persistent concern, often linked to microleakage and a lack of bioactivity in contemporary dental composites. Our study aims to address this issue by developing a low-shrinkage-stress nanocomposite with antibiofilm and remineralization capabilities, thus countering the progression of recurrent caries. In the present study, we formulated low-shrinkage-stress nanocomposites by combining triethylene glycol divinylbenzyl ether and urethane dimethacrylate, incorporating dimethylaminododecyl methacrylate (DMADDM), along with nanoparticles of calcium fluoride (nCaF2) and nanoparticles of amorphous calcium phosphate (NACP). The biofilm viability, biofilm metabolic activity, lactic acid production, and ion release were evaluated. The novel formulations containing 3% DMADDM exhibited a potent antibiofilm activity, exhibiting a 4-log reduction in the human salivary biofilm CFUs compared to controls (p < 0.001). Additionally, significant reductions were observed in biofilm biomass and lactic acid (p < 0.05). By integrating both 10% NACP and 10% nCaF2 into one formulation, efficient ion release was achieved, yielding concentrations of 3.02 ± 0.21 mmol/L for Ca, 0.5 ± 0.05 mmol/L for P, and 0.37 ± 0.01 mmol/L for F ions. The innovative mixture of DMADDM, NACP, and nCaF2 displayed strong antibiofilm effects on salivary biofilm while concomitantly releasing a significant amount of remineralizing ions. This nanocomposite is a promising dental material with antibiofilm and remineralization capacities, with the potential to reduce polymerization-related microleakage and recurrent caries.

The composition of the dental pellicle: an updated literature review

Background

The dental pellicle is a thin layer of up to several hundred nm in thickness, covering the tooth surface. It is known to protect the teeth from acid attacks through its selective permeability and it is involved in the remineralization process of the teeth. It functions also as binding site and source of nutrients for bacteria and conditioning biofilm (foundation) for dental plaque formation.

Methods

For this updated literature review, the PubMed database was searched for the dental pellicle and its composition.

Results

The dental pellicle has been analyzed in the past years with various state-of-the art analytic techniques such as high-resolution microscopic techniques (e.g., scanning electron microscopy, atomic force microscopy), spectrophotometry, mass spectrometry, affinity chromatography, enzyme-linked immunosorbent assays (ELISA), and blotting-techniques (e.g., western blot). It consists of several different amino acids, proteins, and proteolytic protein fragments. Some studies also investigated other compounds of the pellicle, mainly fatty acids, and carbohydrates.

Conclusions

The dental pellicle is composed mainly of different proteins, but also fatty acids, and carbohydrates. Analysis with state-of-the-art analytical techniques have uncovered mainly acidic proline-rich proteins, amylase, cystatin, immunoglobulins, lysozyme, and mucins as main proteins of the dental pellicle. The pellicle has protective properties for the teeth. Further research is necessary to gain more knowledge about the role of the pellicle in the tooth remineralization process.

Hydrogel-Encapsulated Biofilm Inhibitors Abrogate the Cariogenic Activity of Streptococcus mutans

We designed and synthesized analogues of a previously identified biofilm inhibitor IIIC5 to improve solubility, retain inhibitory activities, and to facilitate encapsulation into pH-responsive hydrogel microparticles. The optimized lead compound HA5 showed improved solubility of 120.09 μg/mL, inhibited Streptococcus mutans biofilm with an IC50 value of 6.42 μM, and did not affect the growth of oral commensal species up to a 15-fold higher concentration. The cocrystal structure of HA5 with GtfB catalytic domain determined at 2.35 Å resolution revealed its active site interactions. The ability of HA5 to inhibit S. mutans Gtfs and to reduce glucan production has been demonstrated. The hydrogel-encapsulated biofilm inhibitor (HEBI), generated by encapsulating HA5 in hydrogel, selectively inhibited S. mutans biofilms like HA5. Treatment of S. mutans-infected rats with HA5 or HEBI resulted in a significant reduction in buccal, sulcal, and proximal dental caries compared to untreated, infected rats.

Addition of cariogenic pathogens to complex oral microflora drives significant changes in biofilm compositions and functionalities

BACKGROUND

Dental caries is a microbe and sugar-mediated biofilm-dependent oral disease. Of particular significance, a virulent type of dental caries, known as severe early childhood caries (S-ECC), is characterized by the synergistic polymicrobial interaction between the cariogenic bacterium, Streptococcus mutans, and an opportunistic fungal pathogen, Candida albicans. Although cross-sectional studies reveal their important roles in caries development, these exhibit limitations in determining the significance of these microbial interactions in the pathogenesis of the disease. Thus, it remains unclear the mechanism(s) through which the cross-kingdom interaction modulates the composition of the plaque microbiome. Here, we employed a novel ex vivo saliva-derived microcosm biofilm model to assess how exogenous pathogens could impact the structural and functional characteristics of the indigenous native oral microbiota.

RESULTS

Through shotgun whole metagenome sequencing, we observed that saliva-derived biofilm has decreased richness and diversity but increased sugar-related metabolism relative to the planktonic phase. Addition of S. mutans and/or C. albicans to the native microbiome drove significant changes in its bacterial composition. In addition, the effect of the exogenous pathogens on microbiome diversity and taxonomic abundances varied depending on the sugar type. While the addition of S. mutans induced a broader effect on Kyoto Encyclopedia of Genes and Genomes (KEGG) ortholog abundances with glucose/fructose, S. mutans-C. albicans combination under sucrose conditions triggered unique and specific changes in microbiota composition/diversity as well as specific effects on KEGG pathways. Finally, we observed the presence of human epithelial cells within the biofilms via confocal microscopy imaging.

CONCLUSIONS

Our data revealed that the presence of S. mutans and C. albicans, alone or in combination, as well as the addition of different sugars, induced unique alterations in both the composition and functional attributes of the biofilms. In particular, the combination of S. mutans and C. albicans seemed to drive the development (and perhaps the severity) of a dysbiotic/cariogenic oral microbiome. Our work provides a unique and pragmatic biofilm model for investigating the functional microbiome in health and disease as well as developing strategies to modulate the microbiome. Video Abstract.

Toothpaste Abrasion and Abrasive Particle Content: Correlating High-Resolution Profilometric Analysis with Relative Dentin Abrasivity (RDA)

In this in vitro study, the influence of the concentration of abrasive particles on the abrasivity of toothpastes was investigated using laser scan profilometry on polymethyl methacrylate (PMMA) surfaces with the aim of providing an alternative method to developers for screening of new toothpaste formulations. PMMA plates were tested in a toothbrush simulator with distilled water and four model toothpastes with increasing content of hydrated silica (2.5, 5.0, 7.5, 10.0 wt%). The viscosity of the model toothpaste formulations was kept constant by means of varying the content of sodium carboxymethyl cellulose and water. The brushed surfaces were evaluated using laser scan profilometry at micrometer-scale resolutions, and the total volume of the introduced scratches was calculated along with the roughness parameters Ra, Rz and Rv. RDA measurements commissioned for the same toothpaste formulations were used to analyze the correlation between results obtained with the different methods. The same experimental procedure was applied to five commercially available toothpastes, and the results were evaluated against our model system. In addition, we characterize abrasive hydrated silica and discuss their effects on PMMA-sample surfaces. The results show that the abrasiveness of a model toothpaste increases with the weight percentage of hydrated silica. Increasing roughness parameter and volume loss values show good correlation with the likewise increasing corresponding RDA values for all model toothpastes, as well as commercial toothpastes without ingredients that can damage the used substrate PMMA. From our results, we deduce an abrasion classification that corresponds to the RDA classification established for marketed toothpastes.

[Distinctions in molecular composition of the dental biofilm depending on the method of exo-/endogeneous caries prevention and cariogenic condition of a patient]

PURPOSE OF THE STUDY

For the first time distinctions of molecular composition of the dental biofilm at the stages of exo- and endogeneous caries prevention were studied for persons with different cariogenic conditions involving synchrotron molecular spectroscopy techniques.

MATERIAL AND METHODS

The samples of the dental biofilm collected from participants of the research were studied at the different stages of experiment. The studies of molecular composition of the biofilms were employed involving the equipment set in the Infrared Microspectroscopy (IRM) laboratory of Australian synchrotron.

RESULTS

Basing on the data obtained by synchrotron infrared spectroscopy with Fourier transform as well as using the calculations of the ratios between organic and mineral components and also statistical analysis of the data we could estimate the changes proceeding in the molecular composition of dental biofilm in a dependence of homeostasis conditions in the oral cavity at the stages of exo- and endogeneous caries prevention.

CONCLUSION

Observed changes in the values of phosphate/protein/lipid, phosphate/mineral and phospholipid/lipid ratios as well as the presence of statistically significant intra- and intergroup in these coefficients mean that mechanisms of adsorption for the ions, compounds and molecular complexes incoming from the oral fluid into the dental biofilm at the stage of exo-/endogeneous caries prevention are different for the patients in normal condition and for those ones with the developing caries.

Potential Effect of Giant Freshwater Prawn Shell Nano Chitosan in Inhibiting the Development of Streptococcus mutans and Streptococcus sanguinis Biofilm In Vitro

An oral biofilm comprises a variety of bacteria including Streptococcus mutans and Streptococcus sanguinis that cause human infections, such as caries and periodontitis. Thus, biofilm management plays an important part in the prevention and treatment of oral diseases. Nano chitosan is a bioactive material that has antimicrobial activities. This in vitro study aimed to evaluate the effect of nano chitosan synthesized from giant freshwater prawn shells (PSNC) on S. mutans and S. sanguinis biofilm development. PSNC was prepared from the extracted chitosan of giant freshwater prawn (Macrobrachium rosenbergii) shells using the ionic gelation method. The effect of PSNC on S. mutans ATCC 25175 and S. sanguinis ATCC10556 biofilm formation was evaluated using the crystal violet assay. Both bacteria were inoculated in the presence of various concentrations (5, 2.5, and 1.25 mg/ml) of PSNC for 24 h and 48 h. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy were performed to visualize and study the biofilm architectural features. The biofilms were stained with the BacLight Bacterial Viability Kit prior to CLSM observation to monitor the viability of the biofilm. The results showed that PSNC exposure for 24 h and 48 h inhibited the formation of S. mutans and S. sanguinis biofilms. The biofilm formation inhibition percentage increased with an increase in the PSNC concentration (p < 0.05). The highest inhibitory activity was shown at 5 mg/ml PSNC (p < 0.05). Those findings were confirmed by the subsequent findings using the CLSM and SEM analyses. The biofilm architecture was strongly disrupted upon treatment with PSNC. After exposure to 5 mg/ml PSNC, the number of bacteria significantly decreased. The remaining bacteria were seen as individual cells, showing damaged cells. In conclusion, PSNC inhibits the development of S. mutans and S. sanguinis biofilm in vitro, indicating the potential of PSNC in clinical application for oral bacterial infection, prevention, and treatment.

Development and Physicochemical Characterization of Eugenia brejoensis Essential Oil-Doped Dental Adhesives with Antimicrobial Action towards Streptococcus mutans

Dental caries is a multifactorial, biofilm-dependent infectious disease that develops when detrimental changes occur in the oral cavity microenvironment. The antimicrobial and antivirulence properties of the essential oil obtained from the leaves of Eugenia brejoensis Mazine (EBEO) have been reported against Gram-positive and Gram-negative bacteria. Herein, the antimicrobial action of EBEO towards Streptococcus mutans is reported, along with the development and characterization of dental adhesives doped with. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of EBEO were determined against S. mutans, while its toxicity was analyze using Tenebrio molitor larvae. EBEO (MIC and 10×MIC) was incorporated into the Ambar Advanced Polymerization System® (Ambar APS), a two-step total-etch adhesive system (FGM Dental Group), and the antibiofilm action was evaluated. The reflective strength, modulus of elasticity, degree of conversion, and maximum rate of polymerization of each adhesive were also determined. The MIC and MBC values of EBEO against S. mutans were 62.5 µg/mL. The tested concentrations of EBEO were non-toxic to T. molitor larvae. The formation of S. mutans biofilms was significantly inhibited by EBEO and EBEO-coated resin discs (p < 0.05). Importantly, EBEO incorporation did not affect the mechanical and physicochemical properties in relation to oil-free adhesive version. EBEO showed strong antibacterial and antibiofilm activity against S. mutans, no toxicity effect against T. molitor larvae, and did not jeopardize the physical-chemical properties tested.

Incorporation of Fluoride into Human Teeth after Immersion in Fluoride-Containing Solutions

Toothpastes and mouth rinses contain fluoride as a protective agent against caries. The aim of this study was to determine the degree of fluoride-uptake by human tooth mineral during immersion into fluoride-containing aqueous solutions as different pH. Human teeth were immersed in fluoride-containing solutions to assess the extent of fluoride incorporation into tooth enamel. A total of 16 extracted teeth from 11 patients were immersed at 37 °C for one minute into aqueous fluoride solutions (potassium fluoride; KF) containing either 250 ppm or 18,998 ppm fluoride (1-molar). Fluoride was dissolved either in pure water (neutral pH) or in a citrate buffer (pH 4.6 to 4.7). The elemental surface composition of each tooth was studied by energy-dispersive X-ray spectroscopy in combination with scanning electron microscopy and X-ray powder diffraction. The as-received teeth contained 0.17 ± 0.16 wt% fluoride on average. There was no significant increase in the fluoride content after immersion in 250 ppm fluoride solution at neutral or acidic pH values. In contrast, a treatment with a 1-molar fluoride solution led to significantly increased fluoride concentrations by 0.68 wt% in water and 9.06 wt% at pH 4.7. Although such fluoride concentrations are far above those used in mouth rinses or toothpastes, this indicates that fluoride can indeed enter the tooth surface, especially at a low pH where a dynamic dissolution-reprecipitation process may occur. However, precipitations of calcium fluoride (globuli) were detected in no cases.

Influence of the Amount of Toothpaste on Cleaning Efficacy: An In Vitro Study

OBJECTIVES

 The aim of this in vitro study was to test the influence of the amount of toothpaste on enamel cleaning efficacy.

MATERIALS AND METHODS

 The hydrated silica-based test toothpaste (radioactive dentin abrasion: 60.19 ± 1.35) contained all ingredients of a regular fluoride toothpaste. The cleaning efficacy of four different toothpaste amounts (1.00 g, 0.50 g [both "full length of brush"], 0.25 g ["pea-size"], and 0.125 g ["grain of rice-size"]) diluted in 1.00 mL water were each tested for different brushing times (10, 30, 60, 120, 180, and 300 seconds) using a standardized staining model on human molars with a brushing machine. Photographic documentation and colorimetric measurements were conducted, respectively, initially, after staining and after each brushing step. Colorimetric measurements were used to calculate the stain removal (in %).

STATISTICAL ANALYSIS

 Results were analyzed by one-way analysis of variance with post hoc Tukey test and Levene's test for analysis of homogeneity of variance. The level of significance α was set at ≤ 0.05.

RESULTS

 The cleaning efficacy decreased significantly when using smaller toothpaste amounts. Stain removal after 120 seconds brushing time was: 77.4 ± 5.0% (1.00 g toothpaste), 75.7 ± 3.4% (0.50 g toothpaste), 54.1 ± 6.7% (0.25 g toothpaste), and 48.2 ± 7.1% (0.125 g toothpaste), respectively.

CONCLUSION

 In this in vitro study the cleaning efficacy of a medium-abrasive, hydrated silica-based toothpaste was analyzed. Note that 1.00 g toothpaste showed for all brushing times a significantly higher cleaning efficacy than 0.25 g toothpaste and 0.125 g toothpaste.

Effect of Exo/Endogenous Prophylaxis Dentifrice/Drug and Cariogenic Conditions of Patient on Molecular Property of Dental Biofilm: Synchrotron FTIR Spectroscopic Study

(1) Objectives: This study is the first one to investigate the molecular composition of the dental biofilm during the exogenous and endogenous prophylaxis stages (use of dentifrice/drug) of individuals with different cariogenic conditions using molecular spectroscopy methods. (2) Materials and Methods: The study involved 100 participants (50 males and 50 females), aged 18–25 years with different caries conditions. Biofilm samples were collected from the teeth surface of all participants. The molecular composition of biofilms was investigated using synchrotron infrared microspectroscopy. Changes in the molecular composition were studied through calculation and analysis of ratios between organic and mineral components of biofilm samples. (3) Results: Based on the data obtained by synchrotron FTIR, calculations of organic and mineral component ratios, and statistical analysis of the data, we were able to assess changes occurring in the molecular composition of the dental biofilm. Variations in the phosphate/protein/lipid, phosphate/mineral, and phospholipid/lipid ratios and the presence of statistically significant intra- and inter-group differences in these ratios indicate that the mechanisms of ion adsorption, compounds and complexes arriving from oral fluid into dental biofilm during exo/endogenous prophylaxis, differ for patients in norm and caries development. (4) Conclusions: The conformational environment and charge interaction in the microbiota and the electrostatic state of the biofilm protein network in patients with different cariogenic conditions play an important role. (5) Clinical Significance: Understanding the changes that occur in the molecular composition of the dental biofilm in different oral homeostasis conditions will enable successful transition to a personalised approach in dentistry and high-tech healthcare.

Hydroxyapatite as Remineralization Agent for Children's Dental Care

Children are prone to develop dental caries. This is supported by epidemiological data confirming early childhood caries (ECC) as a highly prevalent disease affecting more than every second child worldwide. ECC is known to result from an imbalance between re- and demineralization where demineralization dominates due to frequent acid production by cariogenic bacteria present in oral biofilms. The application of oral care formulations containing remineralizing agents helps to prevent dental caries. As young children are sensitive and usually swallow (intended or unintended) a majority of toothpaste or other oral care products during daily dental care, all ingredients, especially the actives, should be non-toxic. Biomimetic hydroxyapatite [HAP; Ca5(PO4)3(OH)] is known to have favorable remineralizing properties combined with an excellent biocompatibility, i.e., it is safe if accidently swallowed. Several clinical trials as well as in situ and in vitro studies have shown that HAP remineralizes enamel and dentin. Remineralization occurs due to deposition of HAP particles on tooth surfaces forming mineral-mineral bridges with enamel crystals, but also indirectly through calcium and phosphate ions release as well as HAP's buffering properties in acidic environments (i.e., in plaque). HAP induces a homogenous remineralization throughout the subsurface enamel lesions. This review summarizes the current evidence showing HAP as an effective remineralizing agent in oral care products for children. Additional studies showing also further beneficial effects of HAP such as the reduction of biofilm formation and the relief of hypersensitivity in children with molar incisor hypomineralization (MIH). It can be concluded that HAP is an effective and safe remineralizing agent for child dental care.

Plant Extract-Synthesized Silver Nanoparticles for Application in Dental Therapy

Oral diseases are the most common non-communicable diseases in the world, with dental caries and periodontitis causing major health and social problems. These diseases can progress to systematic diseases and cause disfigurement when left untreated. However, treatment of oral diseases is among the most expensive treatments and often focus on restoration of form and function. Caries prevention has traditionally relied on oral hygiene and diet control, among other preventive measures. In this paper, these measures are not disqualified but are brought into a new context through the use of nanotechnology-based materials to improve these conventional therapeutic and preventive measures. Among inorganic nanomaterials, silver nanoparticles (AgNPs) have shown promising outcomes in dental therapy, due to their unique physicochemical properties and enhanced anti-bacterial activities. As such, AgNPs may provide newer strategies for treatment and prevention of dental infections. However, numerous concerns around the chemical synthesis of nanomaterials, which are not limited to cost and use of toxic reducing agents, have been raised. This has inspired the green synthesis route, which uses natural products as reducing agents. The biogenic AgNPs were reported to be biocompatible and environmentally friendly when compared to the chemically-synthesized AgNPs. As such, plant-synthesized AgNPs can be used as antimicrobial, antifouling, and remineralizing agents for management and treatment of dental infections and diseases.

Bone Regeneration and Oxidative Stress: An Updated Overview

Bone tissue engineering is a complex domain that requires further investigation and benefits from data obtained over past decades. The models are increasing in complexity as they reveal new data from co-culturing and microfluidics applications. The in vitro models now focus on the 3D medium co-culturing of osteoblasts, osteoclasts, and osteocytes utilizing collagen for separation; this type of research allows for controlled medium and in-depth data analysis. Oxidative stress takes a toll on the domain, being beneficial as well as destructive. Reactive oxygen species (ROS) are molecules that influence the differentiation of osteoclasts, but over time their increasing presence can affect patients and aid the appearance of diseases such as osteoporosis. Oxidative stress can be limited by using antioxidants such as vitamin K and N-acetyl cysteine (NAC). Scaffolds and biocompatible coatings such as hydroxyapatite and bioactive glass are required to isolate the implant, protect the zone from the metallic, ionic exchange, and enhance the bone regeneration by mimicking the composition and structure of the body, thus enhancing cell proliferation. The materials can be further functionalized with growth factors that create a better response and higher chances of success for clinical use. This review highlights the vast majority of newly obtained information regarding bone tissue engineering, such as new co-culturing models, implant coatings, scaffolds, biomolecules, and the techniques utilized to obtain them.

Prevention of Caries and Dental Erosion by Fluorides-A Critical Discussion Based on Physico-Chemical Data and Principles

Dental erosion is a common problem in dentistry. It is defined as the loss of tooth mineral by the attack of acids that do not result from caries. From a physico-chemical point of view, the nature of the corroding acids only plays a minor role. A protective effect of fluorides, to prevent caries and dental erosion, is frequently claimed in the literature. The proposed modes of action of fluorides include, for example, the formation of an acid-resistant fluoride-rich surface layer and a fluoride-induced surface hardening of the tooth surface. We performed a comprehensive literature study on the available data on the interaction between fluoride and tooth surfaces (e.g., by toothpastes or mouthwashes). These data are discussed in the light of general chemical considerations on fluoride incorporation and the acid solubility of teeth. The analytical techniques available to address this question are presented and discussed with respect to their capabilities. In summary, the amount of fluoride that is incorporated into teeth is very low (a few µg mm-2), and is unlikely to protect a tooth against an attack by acids, be it from acidic agents (erosion) or from acid-producing cariogenic bacteria.

The Effect of Parental Education and Socioeconomic Status on Dental Caries among Saudi Children

Parental attitudes toward the importance of oral hygiene have an impact on the formation of their children’s oral habits and the prevalence of oral diseases. Our aim was to assess the association between parents’ education and socioeconomic status and their children’s oral health. A cross-sectional study was conducted between the years of 2018 and 2020 in the eastern province of Saudi Arabia among primary school children. Two pre-calibrated dentists performed the clinical examination of the children, and a self-administered validated questionnaire was obtained from their parents. Clinical examination was performed on 589 children with an age range of 3 to 14 years, where 47% were males and 53% were females, 70% with dental caries. Both parents with higher education and a high monthly income were significantly associated with lower prevalence of decayed teeth in their children, respectively. Mother’s education, age, gender and application of sealant were found significantly associated with the high prevalence of caries. High prevalence of tooth decay was reported among school children in the eastern province of Saudi Arabia. A high educational level of parents and high income were correlated with a lower prevalence of decayed teeth, similarly to the situation in the case of presence of medical insurance.

Susceptibility of Dental Caries Microcosm Biofilms to Photodynamic Therapy Mediated by Fotoenticine

Photodynamic therapy (PDT) mediated by Fotoenticine^® (FTC), a new photosensitizer derived from chlorin e-6, has shown in vitro inhibitory activity against the cariogenic bacterium Streptococcus mutans. However, its antimicrobial effects must be investigated on biofilm models that represent the microbial complexity of caries. Thus, we evaluated the efficacy of FTC-mediated PDT on microcosm biofilms of dental caries. Decayed dentin samples were collected from different patients to form in vitro biofilms. Biofilms were treated with FTC associated with LED irradiation and analyzed by counting the colony forming units (log10 CFU) in selective and non-selective culture media. Furthermore, the biofilm structure and acid production by microorganisms were analyzed using microscopic and spectrophotometric analysis, respectively. The biofilms from different patients showed variations in microbial composition, being formed by streptococci, lactobacilli and yeasts. Altogether, PDT decreased up to 3.7 log10 CFU of total microorganisms, 2.8 log10 CFU of streptococci, 3.2 log10 CFU of lactobacilli and 3.2 log10 CFU of yeasts, and reached eradication of mutans streptococci. PDT was also capable of disaggregating the biofilms and reducing acid concentration in 1.1 to 1.9 mmol lactate/L. It was concluded that FTC was effective in PDT against the heterogeneous biofilms of dental caries.