Removal of oral biofilms by bubbles

Effect of Dentifrice Ingredients on Volume and Vitality of a Simulated Periodontal Multispecies Biofilm

The aim of this in vitro study was to investigate the effect of different toothpaste ingredients on biofilm volume and vitality in an established non-contact biofilm removal model. A multi-species biofilm comprising Porphyromonas gingivalis, Streptococcus sanguinis, and Fusobacterium nucleatum was grown on protein-coated titanium disks. Six disks per group were exposed to 4 seconds non-contact brushing using a sonic toothbrush. Four groups assessed slurries containing different ingredients, i.e., dexpanthenol (DP), peppermint oil (PO), cocamidopropyl betaine (CB), and sodium hydroxide (NaOH), one positive control group with the slurry of a toothpaste (POS), and a negative control group with physiological saline (NEG). Biofilm volume and vitality were measured using live-dead staining and confocal laser scanning microscopy. Statistical analysis comprised descriptive statistics and inter-group differences. In the test groups, lowest vitality and volume were found for CB (50.2 ± 11.9%) and PO (3.6 × 105 ± 1.8 × 105 µm3), respectively. Significant differences regarding biofilm vitality were found comparing CB and PO (p = 0.033), CB and NEG (p = 0.014), NaOH and NEG (p = 0.033), and POS and NEG (p = 0.037). However, no significant inter-group differences for biofilm volume were observed. These findings suggest that CB as a toothpaste ingredient had a considerable impact on biofilm vitality even in a non-contact brushing setting, while no considerable impact on biofilm volume was found.

Effect of different hydrogen evolution rates at cathode on bioelectrochemical reduction of CO2 to acetate

Microbial electrosynthesis (MES) offers a promising approach for converting CO2 into valuable chemicals such as acetate. However, the relative low conversion rate severely limits its practical application. This study investigated the impact of different hydrogen evolution rates on the conversion rate of CO2 to acetate in the MES system. Three potentials (-0.8 V, -0.9 V and -1.0 V) corresponding to various hydrogen evolution rates were set and analyzed, revealing an optimal hydrogen evolution rate, yielding a maximum acetate formation rate of 1410.9 mg/L and 73.5 % coulomb efficiency. The electrochemical findings revealed that an optimal hydrogen evolution rate facilitated the formation of an electroactive biofilm. The microbial community of the cathode biofilm highlighted key genera, including Clostridium and Acetobacterium, which played essential roles in electrosynthesis within the MES system. Notably, a low hydrogen evolution rate failed to provide sufficient energy for the electrochemical reduction of CO2 to acetate, while a high rate led to cathode alkalinization, impeding the reaction and causing significant energy wastage. Therefore, maintaining an appropriate hydrogen evolution rate is crucial for the development of mature electroactive biofilms and achieving optimal performance in the MES system.

Influence of the amplitude of different side-to-side toothbrushes on noncontact biofilm removal

OBJECTIVES

To investigate the impact of the lateral deflection of toothbrush bristles (amplitude) of three side-to-side toothbrushes for noncontact biofilm removal in an artificial interdental space model.

MATERIALS AND METHODS

A three-species biofilm (Porphyromonas gingivalis, Fusobacterium nucleatum, Streptococcus sanguinis) was formed in vitro on protein-coated titanium disks. A flow chamber system was combined with a static biofilm growth model. The amplitudes of three commercial side-to-side toothbrushes were evaluated by means of a dose response analysis. The amplitudes were decreased in steps (100%, 85%, 70%, 55%, and 40%). Subsequently, the biofilm-coated substrates were exposed to the toothbrushes. The biofilms were analyzed with confocal laser scanning microscope images and measured using volumetric analyses.

RESULTS

The predictability of interdental biofilm reduction differed among the toothbrushes. A lower variety in the results of repeated experiments occurred in toothbrush C compared to toothbrushes A and B. Toothbrush C obtained highest percentage of biofilm reduction by 85% of amplitude power setting (median biofilm reduction 76%). Decreasing the amplitude from 85 to 40% resulted in reduced biofilm reduction (p = 0.029). In contrast, no significance could be observed for the differences of the tested amplitudes within toothbrushes A and B (p > 0.05). Between the toothbrushes, a significant difference in interdental biofilm reduction was found between C-A (p = 0.029) and C-B (p = 0.029) with amplitude of 85%.

CONCLUSIONS

The amplitude of one of the investigated side-to-side toothbrushes affected the biofilm reduction predictably in an interdental space model.

CLINICAL RELEVANCE

Within certain toothbrushes, a specific amplitude power setting may demonstrate beneficial effects on noncontact biofilm removal.

Carbon dioxide reduction by mixed and pure cultures in microbial electrosynthesis using an assembly of graphite felt and stainless steel as a cathode

Carbon dioxide (CO2) reduction to multi-carbon compounds at the cathode using chemolithoautotrophs is an emerging application of microbial electrosynthesis (MES). In this study, CO2 reduction in MES was investigated at hydrogen evolving potentials, separately by a mixed culture and Clostridium ljungdahlii, using a graphite felt and stainless steel assembly as cathode. The mixed culture reactor produced acetate at the maximum rate of 1.3 mM d(-1), along with methane and hydrogen at -1.1 V/Ag/AgCl. Over 160 days of run-time in four fed-batches, 26% of bicarbonate was converted to acetate between day 28 and 41, whereas in the late batches, methane production prevailed. Out of 45 days of run-time in the C. ljungdahlii reactor, 2.4 mM d(-1) acetate production was achieved at -0.9 V/Ag/AgCl in Batch 1. Simultaneous product degradation occurred when the mixed culture was not selectively enriched. Hydrogen evolution is potentially the rapid way of transferring electrons to the biocatalysts for higher bioproduction rates.

Removal of Dental Biofilms with an Ultrasonically Activated Water Stream

Acidogenic bacteria within dental plaque biofilms are the causative agents of caries. Consequently, maintenance of a healthy oral environment with efficient biofilm removal strategies is important to limit caries, as well as halt progression to gingivitis and periodontitis. Recently, a novel cleaning device has been described using an ultrasonically activated stream (UAS) to generate a cavitation cloud of bubbles in a freely flowing water stream that has demonstrated the capacity to be effective at biofilm removal. In this study, UAS was evaluated for its ability to remove biofilms of the cariogenic pathogen Streptococcus mutans UA159, as well as Actinomyces naeslundii ATCC 12104 and Streptococcus oralis ATCC 9811, grown on machine-etched glass slides to generate a reproducible complex surface and artificial teeth from a typodont training model. Biofilm removal was assessed both visually and microscopically using high-speed videography, confocal scanning laser microscopy (CSLM), and scanning electron microscopy (SEM). Analysis by CSLM demonstrated a statistically significant 99.9% removal of S. mutans biofilms exposed to the UAS for 10 s, relative to both untreated control biofilms and biofilms exposed to the water stream alone without ultrasonic activation ( P < 0.05). The water stream alone showed no statistically significant difference in removal compared with the untreated control ( P = 0.24). High-speed videography demonstrated a rapid rate (151 mm2 in 1 s) of biofilm removal. The UAS was also highly effective at S. mutans, A. naeslundii, and S. oralis biofilm removal from machine-etched glass and S. mutans from typodont surfaces with complex topography. Consequently, UAS technology represents a potentially effective method for biofilm removal and improved oral hygiene.

A new horizon in the treatment of biofilm-associated tonsillitis

Objective:

To demonstrate the efficacy of tonsil brushing in patients with chronic tonsillitis to remove the microbial biofilm on the tonsil surface using an in vitro model.

Design:

Specimens from patients undergoing tonsillectomy were evaluated prior to and following surface cleaning methods, including rinsing and brushing, using scanning electron microscopy (SEM).

Patients:

The study population consisted of 25 randomly selected patients with chronic tonsillitis.

Interventions:

Specimens were collected and divided into four portions. Each portion received distinct surface cleaning methods and was immediately fixed for SEM examination.

Outcome measures:

The biofilm layer on the surface of the tonsils was examined using SEM. The density of the biofilm layer and the degree of persistence of the biofilm after rinsing and brushing were measured.

Results:

The surface biofilm of the tonsils in the first group, which were neither brushed nor rinsed, revealed a thick layer of biofilm on the mucosal surface. The second group of tonsils, which were only rinsed, also showed a thick layer of biofilm. The third group of tonsils, which were rinsed following gentle brushing using a soft toothbrush, showed a reduction in the thickness of the biofilm layer. The fourth group of tonsils, which were brushed with a hard brush, was almost devoid of a biofilm layer.

Conclusion:

Our results demonstrate that rinsing does not effectively remove the biofilm layer on the tonsil surface. The use of a harder brush was identified as a more powerful means of removing biofilm compared with a soft brush.

Advances in microbial biofilm prevention on indwelling medical devices with emphasis on usage of acoustic energy

Microbial biofilms are a major impediment to the use of indwelling medical devices, generating device-related infections with high morbidity and mortality. Major efforts directed towards preventing and eradicating the biofilm problem face difficulties because biofilms protect themselves very effectively by producing a polysaccharide coating, reducing biofilm sensitivity to antimicrobial agents. Techniques applied to combating biofilms have been primarily chemical. These have met with partial and limited success rates, leading to current trends of eradicating biofilms through physico-mechanical strategies. Here we review the different approaches that have been developed to control biofilm formation and removal, focusing on the utilization of acoustic energy to achieve these objectives.

Dynamic removal of oral biofilms by bubbles

A novel approach to the removal of biofilms from solid surfaces is to pass large numbers of air bubbles over the surfaces. Such a phenomenon occurs when teeth are brushed with some types of powered toothbrushes that accelerate bubbly fluid against or across teeth surfaces. Video recordings of air bubbles propelled against a mature biofilm of Streptococcus mutans showed that the bubbles removed the biofilm at the point of collision. A mathematical model of the removal process was proposed and was able to simulate the kinetics of the biofilm removal process. Removal rate was modeled to be proportional to the bubble footprint area and the number of collisions per time. The fraction of biofilm removed per bubble collision is on the order of 0.4, a value much larger than would have been expected based on previous research employing bubbles that moved slowly along a surface that was partially covered with adherent bacteria. The higher removal efficiency is attributed to fluid dynamic shear forces that occur in conjunction with the thermodynamic forces that pull bacteria from a surface as a bubble contacts the biofilm. Fast bubbly flow is expected to remove bacterial biofilm from hard surfaces such as teeth.