Intraoral appliances for in situ oral biofilm growth: a systematic review

Microbial composition and diversity in intraradicular biofilm formed in situ: New concepts based on next-generation sequencing

This study aimed to characterize the taxonomic composition of intraradicular multispecies biofilms (IMBs) formed in situ in a model to reproduce clinical conditions. Twelve palatal roots of maxillary molars had its canals prepared. Two roots were randomly selected to sterility control. Ten intraoral prosthetic appliances with lateral slots were fabricated. The roots were positioned in the slots with the canal access open to the oral cavity. Eight volunteers wore the appliance for 21 days, and two wore it at two different time points. One root from each appliance was removed and stored at -20°C until DNA extraction and sequencing (n = 10). Biofilm was analyzed using next-generation sequencing and bioinformatics. The V4 hyper-variable region of the 16SrRNA gene was amplified and sequenced. For data analyses, the mothur pipeline was used for 16SrRNA processing, and subsequent analyses of the sequence dataset were performed in R using the MicrobiomeAnalyst R package. The taxonomy-based analysis of bacterial communities identified 562 operational taxonomic units (OTUs), which belonged to 93 genera, 44 families, and 8 phyla. Bacterial colonization was different for each biofilm, and samples did not have the same group of bacteria. Alpha and beta diversity analysis revealed some general patterns of sample clustering. A core microbiome of prevalent OTUs and genera was identified. IMBs were heterogeneous when analyzed individually, but some diversity patterns were found after sample clustering. The experimental model seemed to reproduce the actual biofilm composition in endodontic infections, which suggests that it may be used to evaluate disinfection protocols.

Lactobacillus-derived components for inhibiting biofilm formation in the food industry

Biofilm, a microbial community formed by especially pathogenic and spoilage bacterial species, is a critical problem in the food industries. It is an important cause of continued contamination by foodborne pathogenic bacteria. Therefore, removing biofilm is the key to solving the high pollution caused by foodborne pathogenic bacteria in the food industry. Lactobacillus, a commonly recognized probiotic that is healthy for consumer, have been proven useful for isolating the potential biofilm inhibitors. However, the addition of surface components and metabolites of Lactobacillus is not a current widely adopted biofilm control strategy at present. This review focuses on the effects and preliminary mechanism of action on biofilm inhibition of Lactobacillus-derived components including lipoteichoic acid, exopolysaccharides, bacteriocins, secreted protein, organic acids and some new identified molecules. Further, the review discusses several modern biofilm identification techniques and particularly interesting new technology of biofilm inhibition molecules. These molecules exhibit stronger inhibition of biofilm formation, playing a pivotal role in food preservation and storage. Overall, this review article discusses the application of biofilm inhibitors produced by Lactobacillus, which would greatly aid efforts to eradicate undesirable bacteria from environment in the food industries.

Antibiofilm and antimicrobial activity of temporary filling materials on root canals: an in situ acid challenge

The present study evaluated the antibiofilm and antimicrobial effects of temporary restorative materials on root canals after an intra-oral challenge. Seventy roots were endodontically treated and divided into 5 groups: high-viscosity glass ionomer (HV-GIC), light-activated glass ionomer (RM-GIC), zinc-oxide cement without eugenol (ZO), zinc-oxide cement with eugenol (ZOE), and unsealed roots (negative control). For 28 days, 14 participants used intra-oral devices with five roots, and drops of sucrose were applied onto them. The amount of biofilm and the bacterial counts were analyzed by Kruskal-Wallis and Dunn, and by two-way ANOVA and Tukey (α = 0.05). HV-GIC and RM-GIC better inhibit biofilm, followed by ZO and ZOE. Unsealed roots had the largest biofilm accumulation (p = 0.002) and higher bacterial penetration than restored roots (p = 0.023). A low amount of Streptococcus was found in RM-GIC and ZOE-restored roots without difference from HV-GIC (p = 0.021). The low amount of Enterococcus (p = 0.003) was found in the ZOE-restored roots, without difference from GICs.

Deciphering salivary microbiome signature in Crohn's disease patients with different factors contributing to dysbiosis

Crohn's disease (CD) is a chronic inflammatory bowel disease. An imbalanced microbiome (dysbiosis) can predispose to many diseases including CD. The role of oral dysbiosis in CD is poorly understood. We aimed to explore microbiome signature and dysbiosis of the salivary microbiome in CD patients, and correlate microbiota changes to the level of inflammation. Saliva samples were collected from healthy controls (HC) and CD patients (n = 40 per group). Salivary microbiome was analyzed by sequencing the entire 16S rRNA gene. Inflammatory biomarkers (C-reactive protein and calprotectin) were measured and correlated with microbiome diversity. Five dominant species were significantly enriched in CD, namely Veillonella dispar, Megasphaera stantonii, Prevotella jejuni, Dolosigranulum pigrum and Lactobacillus backii. Oral health had a significant impact on the microbiome since various significant features were cariogenic as Streptococcus mutans or periopathogenic such as Fusobacterium periodonticum. Furthermore, disease activity, duration and frequency of relapses impacted the oral microbiota. Treatment with monoclonal antibodies led to the emergence of a unique species called Simonsiella muelleri. Combining immunomodulatory agents with monoclonal antibodies significantly increased multiple pathogenic species such as Salmonella enterica, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. Loss of diversity in CD was shown by multiple diversity indices. There was a significant negative correlation between gut inflammatory biomarkers (particularly calprotectin) and α-diversity, suggesting more inflammation associated with diversity loss in CD. Salivary dysbiosis was evident in CD patients, with unique microbiota signatures and perturbed species that can serve as disease biomarkers or potential targets for microbiota modulation. The interplay of various factors collectively contributed to dysbiosis, although each factor probably had a unique effect on the microbiome. The emergence of pathogenic bacteria in the oral cavity of CD patients is alarming since they can disturb gut homeostasis and induce inflammation by swallowing, or hematogenous spread of microbiota, their metabolites, or generated inflammatory mediators.

Evaluation of a protocol to assess a novel artificial biofilm equivalent for dentures-A prospective clinical pilot study

OBJECTIVES

This pilot study aimed to carry out preliminary tests of the removability of an artificial biofilm equivalent (ABE) and to verify the reproducibility of the ABE testing protocol for a planned main study.

BACKGROUND

There is a lack of data to develop suitable artificial biofilm substitutes, which may be helpful to perform denture hygiene education and to carry out in vitro examinations of oral hygiene products.

MATERIALS AND METHODS

This single-group, prospective, longitudinal, interventional pilot study was conducted in Dresden (Germany) from February until December 2020. Participants were recruited who wore fully functional upper complete dentures. Denture biofilm was grown on acrylic specimens by wearing dentures for 12 h and 36 h using intraoral appliances. Acrylic specimens were coated with ABEs of three compositions: chitosan (ChS) 0.3 g, methylcellulose (MC) 1.7 g; ChS 0.2 g, MC 1.8 g; ChS 0.1 g, MC 1.9 g (labelled 1.7MC, 1.8MC and 1.9MC, respectively). All specimens underwent standardised mechanical brushing. The percentages of remaining biofilm (POB) were measured.

RESULTS

Thirty-one participants were prescreened, and eight (26%) were included. The appliances were well tolerated, and biofilm was collected. ABE was prepared and brushed as planned. Three and six brushing strokes were needed to remove 12-h and 36-h natural denture biofilm, respectively. Correspondingly, three brushing strokes were needed to remove 1.9MC ABE and six brushing strokes to remove 1.8MC and 1.7MC ABE. A reproducibility of ABE removal was indicated.

CONCLUSION

The removability of ABE and the ABE testing protocol were feasible and reproducible for conducting the future main study.

Unraveling the Impact of Gut and Oral Microbiome on Gut Health in Inflammatory Bowel Diseases

Inflammatory bowel disease (IBD) is a complex disorder characterized by chronic inflammation of the gastrointestinal tract (GIT). IBD mainly includes two distinct diseases, namely Crohn's disease and ulcerative colitis. To date, the precise etiology of these conditions is not fully elucidated. Recent research has shed light on the significant role of the oral and gut microbiome in the development and progression of IBD and its collective influence on gut health. This review aims to investigate the connection between the oral and gut microbiome in the context of IBD, exploring the intricate interplay between these microbial communities and their impact on overall gut health. Recent advances in microbiome research have revealed a compelling link between the oral and gut microbiome, highlighting their pivotal role in maintaining overall health. The oral cavity and GIT are two interconnected ecosystems that harbor complex microbial communities implicated in IBD pathogenesis in several ways. Reduction in diversity and abundance of beneficial bacterial species with the colonization of opportunistic pathogens can induce gut inflammation. Some of these pathogens can arise from oral origin, especially in patients with oral diseases such as periodontitis. It is essential to discern the mechanisms of microbial transmission, the impact of oral health on the gut microbiome, and the potential role of dysbiosis in disease development. By elucidating this relationship, we can enhance our understanding of IBD pathogenesis and identify potential therapeutic avenues for managing the disease. Furthermore, innovative strategies for modulating the oral and gut microbiome can promote health and prevent disease occurrence and progression.

Influence of different zirconia surface treatments on biofilm formation in vitro and in situ

OBJECTIVES

To determine if the surface treatment of zirconia affects biofilm formation in an in vitro three-species biofilm model and in situ.

MATERIAL AND METHODS

Zirconia surfaces considered for the transmucosal portion of a zirconia implant were compared with polished pure titanium grade 4 (Tp). Discs 13 mm in diameter of either polished (Zp), polished and heat-treated (Zpt), machined (Zm), machined and heat-treated (Zmt) and sandblasted, etched and heat-treated (Z14) zirconia were fabricated. Surface roughness and wettability of specimens was measured. Biofilm formation was evaluated by safranin staining and scanning electron microscopy (SEM) using a three-species model, and intraorally with 16 volunteers carrying oral splints in two independent experiments. Relative biofilm formation was compared with Kruskal-Wallis followed by Bonferroni post-hoc test (α=0.05).

RESULTS

In vitro biofilm formation with optical density values on Zp (0.14±0.01), Zpt (0.14±0.02), Zm (0.13±0.01) and Zmt (0.13±0.01) was significantly lower than on Tp (0.21±0.05) and Z14 (0.20±0.04) (p<0.05). In situ biofilm formation was significantly higher on Z14 (0.56±0.45) (p<0.05), while no significant differences in optical density were observed among Zp (0.25±0.20), Zm (0.36±0.34) and Tp (0.28±0.22). SEM analysis supported quantitative findings.

CONCLUSIONS

In the in vitro three-species biofilm model differences in material and surface roughness affected biofilm formation. In situ biofilm formation was mainly affected by the surface roughness of the specimens. Polishing of zirconia is recommended to reduce biofilm formation while heat-treatment has no significant effect.

Mapping of a Subgingival Dual-Species Biofilm Model Using Confocal Raman Microscopy

Techniques for continuously monitoring the formation of subgingival biofilm, in relation to the determination of species and their accumulation over time in gingivitis and periodontitis, are limited. In recent years, advancements in the field of optical spectroscopic techniques have provided an alternative for analyzing three-dimensional microbiological structures, replacing the traditional destructive or biofilm staining techniques. In this work, we have demonstrated that the use of confocal Raman spectroscopy coupled with multivariate analysis provides an approach to spatially differentiate bacteria in an in vitro model simulating a subgingival dual-species biofilm. The present study establishes a workflow to evaluate and differentiate bacterial species in a dual-species in vitro biofilm model, using confocal Raman microscopy (CRM). Biofilm models of Actinomyces denticolens and Streptococcus oralis were cultured using the “Zürich in vitro model” and were analyzed using CRM. Cluster analysis was used to spatially differentiate and map the biofilm model over a specified area. To confirm the clustering of species in the cultured biofilm, confocal laser scanning microscopy (CLSM) was coupled with fluorescent in vitro hybridization (FISH). Additionally, dense bacteria interface area (DBIA) samples, as an imitation of the clusters in a biofilm, were used to test the developed multivariate differentiation model. This confirmed model was successfully used to differentiate species in a dual-species biofilm and is comparable to morphology. The results show that the developed workflow was able to identify main clusters of bacteria based on spectral “fingerprint region” information from CRM. Using this workflow, we have demonstrated that CRM can spatially analyze two-species in vitro biofilms, therefore providing an alternative technique to map oral multi-species biofilm models.

Efficacy of 0.05% Chlorhexidine and 0.05% Cetylpyridinium Chloride Mouthwash to Eliminate Living Bacteria on In Situ Collected Biofilms: An In Vitro Study

Chlorhexidine (CHX) mouthwashes are frequently used as an adjunctive measure for the treatment of periodontitis and peri-implantitis, as well as in patients on maintenance therapy. However, their prolonged use is associated with several side effects. This study aimed at evaluating if a mouthwash with a reduced concentration of CHX combined with cetylpyridnium chloride (CPC) was as effective as a conventional CHX mouthwash in the reduction in living cells in oral biofilms attached to hydroxyapatite (HA) and micro-rough titanium (Ti) surfaces. Four healthy volunteers wore a customized acrylic appliance containing HA and Ti discs for in situ plaque accumulation. Biofilms were grown on the discs for 24 or 48 h and then randomly exposed for 60 s to: 0.05% CHX + 0.05% CPC, 0.1% CHX (positive control) or sterile saline (negative control). Viability assay and live-dead staining were performed to quantify bacterial viability and to distinguish live and dead cells, respectively. At both time points, contrary to saline, CHX, both alone and in combination with CPC, exhibited high antibacterial properties and induced a significant reduction in biofilm viability. This study demonstrates the potential of mouthwashes containing a low concentration of CHX combined with CPC as effective antibacterial agents for long-term applications with reduced undesired side effects.

Next-Generation Sequencing for Determining the Effect of Arginine on Human Dental Biofilms Using an In Situ Model

Oral biofilms are associated with caries, periodontal diseases, and systemic diseases. Generally, antimicrobial therapy is used as the first line of treatment for infectious diseases; however, bacteria in biofilms eventually develop antibiotic resistance. This study aimed to apply our in situ biofilm model to verify whether an arginine preparation is useful for plaque control. Ten healthy subjects who did not show signs of caries, gingivitis, or periodontitis were recruited. The dental biofilms from the subjects were obtained using our oral device before and after gargling with arginine solution for 4 weeks. We found that 8% arginine solution significantly increased the concentration of ammonium ions (NH₄ ⁺) in vitro and in vivo in saliva (p < 0.05) and decreased the proportions of the genera Atopobium and Catonella in vivo. However, the viable count was unaffected by the mouthwash. Further, oral populations of the genera Streptococcus and Neisseria tended to increase with the use of arginine. Therefore, we concluded that using an 8% arginine solution decreased the NH₄ ⁺ concentration in the oral cavity without affecting the number of viable bacteria, and that the diversity of oral bacterial flora changed. We suggest that arginine might help prevent mature biofilm formation.

Bio-Interactive Zwitterionic Dental Biomaterials for Improving Biofilm Resistance: Characteristics and Applications

Biofilms are formed on surfaces inside the oral cavity covered by the acquired pellicle and develop into a complex, dynamic, microbial environment. Oral biofilm is a causative factor of dental and periodontal diseases. Accordingly, novel materials that can resist biofilm formation have attracted significant attention. Zwitterionic polymers (ZPs) have unique features that resist protein adhesion and prevent biofilm formation while maintaining biocompatibility. Recent literature has reflected a rapid increase in the application of ZPs as coatings and additives with promising outcomes. In this review, we briefly introduce ZPs and their mechanism of antifouling action, properties of human oral biofilms, and present trends in anti-biofouling, zwitterionic, dental materials. Furthermore, we highlight the existing challenges in the standardization of biofilm research and the future of antifouling, zwitterated, dental materials.

The antibacterial efficacy of silver diamine fluoride (SDF) is not modulated by potassium iodide (KI) supplements: A study on in-situ plaque biofilms using viability real-time PCR with propidium monoazide

Silver diamine fluoride (SDF) is commonly used to arrest caries lesions, especially in early childhood caries. Recently, it was suggested that SDF can be combined with potassium iodide (KI) to minimize the discoloration of demineralized dentine associated with SDF application. However, the antibacterial efficacy of SDF alone or combined with KI on in-situ biofilm is unknown. Hence, we compared the anti-plaque biofilm efficacy of two different commercially available SDF solutions, with or without KI, using an in-situ biofilm, analysed using viability real-time PCR with propidium monoazide (PMA). Appliance-borne in-situ biofilm samples (n = 90) were grown for a period of 6 h in five healthy subjects who repeated the experiment on three separate occasions, using a validated, novel, intraoral device. The relative anti-biofilm efficacy of two SDF formulations; 38.0% Topamine (SDFT) and 31.3%, Riva Star (SDFR), KI alone, and KI in combination with SDFR (SDFR+KI) was compared. The experiments were performed by applying an optimized volume of the agents onto the biofilm for 1min, mimicking the standard clinical procedure. Afterwards the viability of the residual biofilm bacteria was quantified using viability real-time PCR with PMA, then the percentage of viable from total bacteria was calculated. Both SDF formulations (SDFT and SDFR) exhibited potent antibacterial activities against the in-situ biofilm; however, there was non-significant difference in their efficacy. KI alone did not demonstrate any antibacterial effect, and there was non-significant difference in the antibacterial efficacy of SDF alone compared to SDF with KI, (SDFT v SDFR/KI). Thus, we conclude that the antibacterial efficacy of SDF against plaque biofilms is not modulated by KI supplements. Viability real-time PCR with PMA was successfully used to analyze the viability of naturally grown oral biofilm; thus, the same method can be used to test the antimicrobial effect of other agents on oral biofilms in future research.