Structural changes in the oral microbiome of the adolescent patients with moderate or severe dental fluorosis

Gut microbiome and function are altered for individuals living in high fluoride concentration areas in Pakistan

BACKGROUND

Endemic fluorosis refers to the condition when individuals are exposed to excessive amounts of fluoride ion due to living in a region characterized by elevated levels of fluorine in the drinking water, food, and/or air. In Pakistan, a substantial proportion of the population is thereby affected, posing a public health concern.

OBJECTIVES

Assessing how the gut microbiota and its metabolic profiles are impacted by chronic exposure to fluoride in drinking water (that caused Dental Fluorosis) as well as to perceive how this microbiota is connected to adverse health outcomes prevailing with fluoride exposure.

METHODS

Drinking water (n=27) and biological samples (n=100) of blood, urine and feces were collected from 70 high fluoride exposed (with Dental Fluorosis) and 30 healthy control (without Dental Fluorosis) subjects. Water and urinary fluoride concentrations were determined. Serum/plasma biochemical testing was performed. Fecal DNA extraction, 16S rRNA analysis of microbial taxa, their predicted metabolic function and fecal short chain fatty acids (SCFAs) quantification were carried out.

RESULTS

The study revealed that microbiota taxonomic shifts and their metabolic characterization had been linked to certain host clinical parameters under the chronic fluoride exposure. Some sets of genera showed strong specificity to water and urine fluoride concentrations, Relative Fat Mass index and SCFAs. The SCFAs response in fluoride-exposed samples was observed to be correlated with bacterial taxa that could contribute to adverse health effects.

CONCLUSIONS

Microbial dysbiosis as a result of endemic fluorosis exhibits a structure that is associated with risk of metabolic deregulation and is implicated in various diseases. Our results may form the development of novel interventions and may have utility in diagnosis and monitoring.

Does fluoride exposure impact on the human microbiome?

Fluoride is added to drinking water in some countries to prevent tooth decay (caries). There is no conclusive evidence that community water fluoridation (CWF) at WHO recommended concentrations for caries prevention has any harmful effects. However, research is ongoing regarding potential effects of ingested fluoride on human neurodevelopment and endocrine dysfunction. Simultaneously, research has emerged highlighting the significance of the human microbiome in gastrointestinal and immune health. In this review we evaluate the literature examining the effect of fluoride exposure on the human microbiome. Unfortunately, none of the studies retrieved examined the effects of ingested fluoridated water on the human microbiome. Animal studies generally examined acute fluoride toxicity following ingestion of fluoridated food and water and conclude that fluoride exposure can detrimentally perturb the normal microbiome. These data are difficult to extrapolate to physiologically relevant human exposure dose ranges and the significance to humans living in areas with CWF requires further investigation. Conversely, evidence suggests that the use of fluoride containing oral hygiene products may have beneficial effects on the oral microbiome regarding caries prevention. Overall, while fluoride exposure does appear to impact the human and animal microbiome, the long-term consequences of this requires further study.

Saliva microbiome alterations in dental fluorosis population

Background

We aimed to explore saliva microbiome alterations in dental fluorosis population.

Methods

The prevalence of dental fluorosis was examined in 957 college students. Dean's fluorosis index was used to evaluate the dental fluorosis status. Changes in the composition of the salivary microbiome were assessed in a subset of these patients (100 healthy controls, 100 dental fluorosis patients).

Results

Dental fluorosis affected 47% of the student sample, and incidence was unrelated to gender. Compared with healthy controls, the microbiota of patients with dental fluorosis exhibited increased diversity, with increased abundance of Treponema lecithinolyticum, Vibrio metschnikovii, Cupriavidus pauculus, Pseudomonas, Pseudomonadaceae, Pseudomonadales, and decreased abundance of Streptococcus mutans, Streptococcus sanguinis, Gemella, and Staphylococcales. Function analyses showed increases in arginine biosynthesis in patients affected by dental fluorosis, together with reductions in amino sugar and nucleotide sugar metabolism, fructose and mannose metabolism, and starch and sucrose metabolism.

Conclusions

These results suggest that there are striking differences in salivary microbiome between healthy controls and dental fluorosis patients. Dental fluorosis may contribute to periodontitis and systemic lung diseases. There is a need for cohort studies to determine whether altering the salivary microbiota in dental fluorosis patients can alter the development of oral or systemic diseases.

A Qualitative and Comprehensive Analysis of Caries Susceptibility for Dental Fluorosis Patients

Dental fluorosis (DF) is an endemic disease caused by excessive fluoride exposure during childhood. Previous studies mainly focused on the acid resistance of fluorotic enamel and failed to reach a consensus on the topic of the caries susceptibility of DF patients. In this review, we discuss the role of DF classification in assessing this susceptibility and follow the “four factors theory” in weighing the pros and cons of DF classification in terms of host factor (dental enamel and saliva), food factor, bacteria factor, and DF treatment factor. From our analysis, we find that susceptibility is possibly determined by various factors such as the extent of structural and chemical changes in fluorotic enamel, eating habits, fluoride levels in diets and in the oral cavity, changes in quantity and quality of saliva, and/or oral hygiene. Thus, a universal conclusion regarding caries susceptibility might not exist, instead depending on each individual’s situation.

How Do Polymer Coatings Affect the Growth and Bacterial Population of a Biofilm Formed by Total Human Salivary Bacteria?-A Study by 16S-RNA Sequencing

Antimicrobial surface modifications are required to prevent biomaterial-associated biofilm infections, which are also a major concern for oral implants. The aim of this study was to evaluate the influence of three different coatings on the biofilm formed by human saliva. Biofilms grown from human saliva on three different bioactive poly(oxanorbornene)-based polymer coatings (the protein-repellent PSB: poly(oxanorbornene)-based poly(sulfobetaine), the protein-repellent and antimicrobial PZI: poly(carboxyzwitterion), and the mildly antimicrobial and protein-adhesive SMAMP: synthetic mimics of antimicrobial peptides) were analyzed and compared with the microbial composition of saliva, biofilms grown on uncoated substrates, and biofilms grown in the presence of chlorhexidine digluconate. It was found that the polymer coatings significantly reduced the amount of adherent bacteria and strongly altered the microbial composition, as analyzed by 16S RNA sequencing. This may hold relevance for maintaining oral health and the outcome of oral implants due to the existing synergism between the host and the oral microbiome. Especially the reduction of some bacterial species that are associated with poor oral health such as Tannerella forsythia and Fusobacterium nucleatum (observed for PSB and SMAMP), and Prevotella denticola (observed for all coatings) may positively modulate the oral biofilm, including in situ.

Comparative Analyses of the Subgingival Microbiome in Chronic Periodontitis Patients with and without Gingival Erosive Oral Lichen Planus Based on 16S rRNA Gene Sequencing

The aim of the study was to compare the microbiota composition and bacterial diversity of subgingival plaque in chronic periodontitis patients with and without gingival erosive oral lichen planus. The subgingival plaque samples of 20 chronic periodontitis patients with gingival erosive oral lichen planus (CP-OLP group) and 19 chronic periodontitis patients without gingival erosive oral lichen planus (CP group) were analyzed by 16S rRNA gene high-throughput sequencing. Compared with the CP group, the richness and diversity of subgingival plaque microflora in the CP-OLP group decreased significantly. There were some differences between the two groups in the composition of microflora on the levels of phylum and genus. Distributions of Prevotella and Leptotrichia in the CP-OLP group were significantly lower than those in the CP group. The dominant genera in CP-OLP group were Pseudomonas and Granulicatella. These results indicated that gingival erosive oral lichen planus may influence the structure and proportion of subgingival plaque microflora.