Inhibition of nicotine-induced Streptococcus mutans biofilm formation by salts solutions intended for mouthrinses

Tobacco-enhanced biofilm formation by Porphyromonas gingivalis and other oral microbes

Microbial biofilms promote pathogenesis by disguising antigens, facilitating immune evasion, providing protection against antibiotics and other antimicrobials and, generally, fostering survival and persistence. Environmental fluxes are known to influence biofilm formation and composition, with recent data suggesting that tobacco and tobacco-derived stimuli are particularly important mediators of biofilm initiation and development in vitro and determinants of polymicrobial communities in vivo. The evidence for tobacco-augmented biofilm formation by oral bacteria, tobacco-induced oral dysbiosis, tobacco-resistance strategies, and bacterial physiology is summarized herein. A general overview is provided alongside specific insights gained through studies of the model and archetypal, anaerobic, Gram-negative oral pathobiont, Porphyromonas gingivalis.

Effect of eucalyptus oil on Streptococcus mutans and Enterococcus faecalis growth

OBJECTIVES

There is a significant apprehension in medicine and dentistry concerning the emergence of antibiotic-resistant pathogens, as it composes a significant threat to global health, particularly oral health. The growing concern that oral pathogens may develop resistance against standard preventive measures raises the need for alternative measures to prevent these pathogens' growth without inducing microbial resistance. Therefore, this study aims to assess the antibacterial properties of eucalyptus oil (EO) against two main oral disease pathogens, Streptococcus mutans, and Enterococci faecalis.

METHODS

S. mutans and E. faecalis biofilms were initiated using brain-heart infusion (BHI) broth supplemented with 2% sucrose with and without diluted EO. After 24 h of biofilm formation, total absorbance was measured via spectrophotometer; then, the biofilm was fixed, stained with crystal violet dye, and measured at 490 nm. An Independent t-test was used to compare the outcomes.

RESULTS

Diluted EO revealed significant total absorbance reduction against S. mutans and E. faecalis compared to the control (p ≤ 0.001). For the biofilm measurement, S. mutans and E. faecalis biofilms were reduced by around 60- and 30-fold, respectively, compared to the group with no EO (p ≤ 0.001).

CONCLUSION

Based on this study's results, using EO as an organic compound could be considered an adjunctive tool in preventing the growth of oral pathogens causing dental caries and endodontic infection.

Antibacterial Activities of Methanol and Aqueous Extracts of Salvadora persica against Streptococcus mutans Biofilms: An In Vitro Study

The use of herbal products in oral hygiene care has a long history, and their use is popular today. A tree stick, named Salvadora persica (S. persica), is commonly used to remove dental plaque and clean teeth in many countries. In addition, extracts of S. persica can be used as a mouthwash, as they demonstrate antimicrobial properties. This study aimed to investigate the antibacterial effect of S. persica methanol and aqueous extracts against Streptococcus mutans (S. mutans) biofilm. A S. mutans biofilm formation assay was conducted using different concentrations of S. persica methanol or water extracts in tryptic soy broth (TSB) supplemented with 1% sucrose. The biofilm was stained with crystal violet dye, and the absorbance was assessed to examine biofilm formation. One-way analysis of variance (ANOVA) and Tukey tests were used to analyze the results. The S. persica methanol extract displayed a significant inhibition (p ≤ 0.001) against the S. mutans biofilm. The 10 mg/mL concentration of the S. persica methanol extract was determined as the minimum biofilm inhibitory concentration (MBIC). The used methanol concentration, mixed with TSB supplemented with 1% sucrose and without the S. persica extract, did not inhibit the S. mutans biofilm. The S. persica aqueous extract did not demonstrate any biofilm inhibition at any concentration (p ≥ 0.05). The findings of this study suggest the potential of using S. persica methanol extract as a mouthwash or adjunctive to oral hygiene tools.

Microorganisms: crucial players of smokeless tobacco for several health attributes

Global consumption of smokeless tobacco (SLT) reached 300 million users worldwide majorly from middle-income countries. More than 4000 chemical compounds represent it as one of the noxious consumable products by humans. Besides toxicants/carcinogens, the heavy microbial load on smokeless tobacco further keeps human health at higher risk. Several of these inhabitant microbes participate in biofilm formation and secrete endotoxin/mycotoxins and proinflammatory-like molecules, leading to several oral diseases. Tobacco-associated bacteria exhibit their role in tobacco-specific nitrosamines (TSNAs) formation and acetaldehyde production; both are well-documented carcinogens. Moreover, tobacco exhibits the potential to alter the oral microbiome and induce dysbiotic conditions that lead to the onset of several oral and systemic diseases. Traditional cultivation approaches of microbiology provide partial information of microbial communities of a habitat; therefore, microbiomics has now been employed to study the metagenomes of entire microbial communities. In the past 5 years, few NGS-based investigations have revealed that SLT harbors four dominant phyla (Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes) dominating Bacillus spp. and/or Pseudomonas spp. However, functional characterization of their genetic elements will be a more informative attribute to understand the correlation between inhabitant microbial diversity and their relatedness concerning abundance and diseases. This review provides an update on the microbial diversity of SLT and its associated attributes in human health. KEY POINTS: • Heavy microbial load on smokeless tobacco alarms for poor oral hygiene. • Inhabitant microorganisms of SLT participate in TSNA and biofilm formation. • SLTs alter the oral microbiome and causes oral dysbiosis.

Microbiology of the American Smokeless Tobacco

Smokeless tobacco products (STP) contain diverse microbial communities that contribute to the formation of harmful chemical byproducts. This is concerning since 300 million individuals around the globe are users of smokeless tobacco. Significant evidence has shown that microbial metabolic activities mediate the formation of carcinogens during manufacturing. In recent years, studies have revealed a series of additional health impacts that include lesions and inflammation of the oral mucosa and the gastrointestinal tract, as well as alterations of the endogenous microbiota. These findings are due to recent developments in molecular technologies that allowed researchers to better examine the microbial component of these products. This new information illustrates the scale of the STP microbiota and its diversity in the finished product that is sold for consumption. Additionally, the application of metagenomics and metatranscriptomics has provided the tools to look at phylogenies across bacterial, viral, and eukaryotic groups, their functional capacities, and viability. Here we present key examples of tobacco microbiology research that utilizes newer approaches and strategies to define the microbial component of smokeless tobacco products. We also highlight challenges in these approaches, the knowledge gaps being filled, and those gaps that warrant further study. A better understanding of the microbiology of STP brings vast public health benefits. It will provide important information for the product consumer, impact manufacturing practices, and provide support for the development of attainable and more meaningful regulatory goals. KEY POINTS: Newer technologies allowed quicker and more comprehensive identification of microbes in tobacco samples, encapsulating microorganisms difficult or impossible to culture. Current research in smokeless tobacco microbiology is filling knowledge gaps previously unfilled due to the lack of suitable approaches. The microbial ecology of smokeless tobacco presents a clearer picture of diversity and variability not considered before.

The burden of root caries: Updated perspectives and advances on management strategies

BACKGROUND

Root caries has gained much attention in the last few years. As the world's population is ageing and people currently tend to retain more teeth compared with older generations, there is an increased prevalence of periodontal disease and gingival recession, which may accelerate the onset of root caries.

OBJECTIVE

This review aims to summarise recent findings related to the diagnosis, prevention and treatment of root caries.

MATERIALS AND METHODS

MEDLINE (OVID) and Scopus (Elsevier) searches were performed to identify and discuss articles that address the pathogenicity and clinical management of root caries.

RESULTS

Root caries is a multifactorial disease. Cariogenic species involved in root caries are less dependent on carbohydrates since collagen degradation inside the dentinal tubules can provide nutrients and microcavities for the invading microorganisms. Furthermore, the root surface has fewer minerals in comparison with enamel, which may accelerate the onset of demineralisation. Root caries could be prevented by patient education, modification of risk factors, and the use of in-office and home remineralisation tools. The use of non-invasive approaches to control root caries is recommended, as the survival rate of root caries restorations is poor. When plaque control is impossible and a deep/large cavity is present, glass ionomer or resin-based restorations can be placed.

CONCLUSION

The assessment of root carious lesions is critical to determine the lesion activity and the required intervention. Dental practitioners should also be aware of different prevention and treatment approaches to design optimum oral health care for root caries-affected patients.

In-Vitro Model of Scardovia wiggsiae Biofilm Formation and Effect of Nicotine

Recently, Scardovia wiggsiae has been reported to be strongly associated with caries formation. This study aimed to establish an in vitro model of S. wiggsiae biofilm and to investigate the effect of nicotine on S. wiggsiae colony-forming units (CFUs) growth. S. wiggsiae biofilm was grown overnight using brain-heart infusion (BHI) broth supplemented with 5 g of yeast extract/L (BHI-YE). The overnight culture was used as an inoculum to grow S. wiggsiae biofilm on standardized enamel and dentin samples. Samples were incubated with different nicotine concentrations (0, 0.5, 1, 2, 4, 8, 16 and 32 mg/mL) for 3 days. The dissociated biofilms were diluted, spiral plated on blood agar plates, and incubated for 24 h. CFUs/mL were quantified using an automated colony counter. A two-way ANOVA was used to compare the effect of different nicotine concentrations on S. wiggsiae CFUs. This study demonstrated that S. wiggsiae biofilm could be initiated and formed in vitro. Increased CFUs was observed through 0.5-4 mg/mL and 0.5-8 mg/mL of nicotine using enamel and dentin substrates, respectively. 16 and 32 mg/mL of nicotine were determined as the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC), respectively. S. wiggsiae formed greater biofilm on enamel than dentin specimens in response to the nicotine stimulus. This study demonstrated the negative effect of smoking on increasing S. wiggsiae biofilm. Establishing S. wiggsiae biofilm in vitro may allow researchers in the future to have a better understanding of caries pathogenesis and bacterial interaction.

The Impact of Photosensitizer Selection on Bactericidal Efficacy Of PDT against Cariogenic Biofilms: A Systematic Review and Meta-Analysis

BACKGROUND

There are investigations on multiple photosensitizers for modulation of caries-related biofilms using PDT. However, much controversy remains about recommended parameters mostly on the selection of an efficient photosensitizer.

OBJECTIVE

The study performed a systematic review to identify the answer to the following question: What photosensitizers present high bactericidal efficacy against cariogenic biofilms?

METHODS

Systematic review with meta-analyses were carried out for English language articles from October to December 2019 (PRISMA standards) using MEDLINE, Scopus, Biomed Central, EMBASE, LILACS, and Web of Science. Information on study design, biofilm model, photosensitizer, light source, energy delivery, the incubation time for photosensitizer, and bacterial reduction outcomes were recorded. We performed two meta-analyses to compare bacterial reduction, data was expressed by (1) base 10 Logarithm values and (2) Log reduction RESULTS: After the eligibility criteria were applied (PEDro scale), the selected studies showed that toluidine Blue Ortho (TBO) and methylene blue (MBO) (5-min incubation time and 5-min irradiation) demonstrated better bacterial reduction outcomes. For the data expressed by Log TBO, MBO, curcumin, and Photogem® presented a significant bacterial decrease in comparison to the control (p = 0.042). For the data represented by Log reduction, the bacterial reduction toward S.mutans was not significant for any photosensitizer (p = 0.679).

CONCLUSION

The lack of methodological standardization among the studies still hinders the establishment of photosensitizer and bactericidal efficiency. TBO, MBO, curcumin, and photogem generate greater PDT-based bacterial reduction on caries-related bacteria.. Further clinical studies are necessary in order to obtain conclusive results.

Emerging Contact-Killing Antibacterial Strategies for Developing Anti-Biofilm Dental Polymeric Restorative Materials

Polymeric materials are the first choice for restoring tooth cavities, bonding tooth-colored fillings, sealing root canal systems, and many other dental restorative applications. However, polymeric materials are highly susceptible to bacterial attachment and colonization, leading to dental diseases. Many approaches have been investigated to minimize the formation of biofilms over polymeric restorative materials and at the tooth/material interfaces. Among them, contact-killing compounds have shown promising results to inhibit dental biofilms. Contact-killing compounds can be immobilized within the polymer structure, delivering a long-lasting effect with no leaching or release, thus providing advantages compared to release-based materials. This review discusses cutting-edge research on the development of contact-killing compounds in dental restorative materials to target oral pathogens. Contact-killing compounds in resin composite restorations, dental adhesives, root canal sealers, denture-based materials, and crown cements have all demonstrated promising antibacterial properties. Contact-killing restorative materials have been found to effectively inhibit the growth and activities of several oral pathogens related to dental caries, periodontal diseases, endodontic, and fungal infections. Further laboratory optimization and clinical trials using translational models are needed to confirm the clinical applicability of this new generation of contact-killing dental restorative materials.

Antibacterial efficacy and remineralization capacity of glycyrrhizic acid added casein phosphopeptide-amorphous calcium phosphate

The aim was to evaluate remineralization capacity and antibacterial efficiency of Tooth Mousse and various amounts of glycyrrhizic acid added Tooth Mousse on primary tooth enamel. Three groups were formed; Group 1 (CPP-ACP), Group 2 (CPP-ACP + 5% glycyrrhizic acid), and Group 3 (CPP-ACP + 10% glycyrrhizic acid) in order to evaluate remineralization capacity. Enamel samples were immersed in demineralization solution and then remineralization agents were applied. Surface microhardness and SEM analyses were performed at the beginning, after demineralization and remineralization. For antibacterial tests, four groups were formed; Group 1, Group 2 and Group 3 and Group 4 (control). Biofilms were then exposed to 10% sucrose eight times per day for 7 days. After biofilm growth period, samples were treated with materials to evaluate antibacterial efficiency except control group. After application of materials, samples were incubated 2 more days at 37°C and at the end of this period, absorbance values of biofilms were determined and data were analyzed. An increase in microhardness values was Group 2 > Group 3 > Group 1, respectively, but there were no significant differences. After remineralization, microhardness values showed significant increases when compared to demineralized groups, but there was no significant difference. All groups showed decreased absorbance value of biofilm when compared with control group but they were insignificant. It was observed that both in Group 2 and Group 3, glycyrrhizic acid did not have a negative effect on remineralization and although they have an increase, it was insignificant. Although glycyrrhizic acid added CPP-ACP groups showed increased antibacterial activity, they were not statistically significant.