The Effectiveness of Manual versus High-Frequency, High-Amplitude Sonic Powered Toothbrushes for Oral Health: A Meta-Analysis.

OBJECTIVES: Evaluate the short-term clinical efficacy of high-frequency, high-amplitude sonic powered toothbrushes compared to manual toothbrushes on plaque removal and gingivitis reduction in everyday use through a meta-analysis of randomized controlled trials. METHODS: Embase, MEDLINE, BIOSIS, Inspec, PQ SciTech, Compendex, SciSearch and IADR abstracts databases were searched. Eligible were clinical trials comparing at least one manual to one sonic powered toothbrush on plaque or gingivitis reduction over four weeks to three months in subjects without disability that could affect tooth brushing. Two authors selected and extracted data from eligible studies. When insufficient information was available, researchers were contacted. Data were pooled using random-effects models to compute standardized mean differences (SMD) and 95% confidence intervals (95% CI) quantifying differences in plaque or gingivitis reduction. Risk for bias and sources of heterogeneity were assessed. RESULTS: The combined results of 18 studies comprising 1,870 subjects showed that sonic powered toothbrushes had statistically significantly greater plaque removal (SMD = -0.89, 95%CI = [-1.27, -0.51]) and gingivitis reduction (-0.67, [-1.01, -0.32]). Heterogeneity was large and bias was not apparent. CONCLUSIONS: High-frequency, high-amplitude sonic powered toothbrushes decreased plaque and gingivitis significantly more effectively than manual toothbrushes in everyday use in studies lasting up to three months.

High-Velocity Microsprays Enhance Antimicrobial Activity in Streptococcus mutans Biofilms.

Streptococcus mutans in dental plaque biofilms play a role in caries development. The biofilm's complex structure enhances the resistance to antimicrobial agents by limiting the transport of active agents inside the biofilm. The authors assessed the ability of high-velocity water microsprays to enhance delivery of antimicrobials into 3-d-old S. mutans biofilms. Biofilms were exposed to a 90° or 30° impact, first using a 1-µm tracer bead solution (109 beads/mL) and, second, a 0.2% chlorhexidine (CHX) or 0.085% cetylpyridinium chloride (CPC) solution. For comparison, a 30-s diffusive transport and simulated mouthwash were also performed. Confocal microscopy was used to determine number and relative bead penetration depth into the biofilm. Assessment of antimicrobial penetration was determined by calculating the killing depth detected by live/dead viability staining. The authors first demonstrated that the microspray was able to deliver significantly more microbeads deeper in the biofilm compared with diffusion and mouthwashing exposures. Next, these experiments revealed that the microspray yielded better antimicrobial penetration evidenced by deeper killing inside the biofilm and a wider killing zone around the zone of clearance than diffusion alone. Interestingly the 30° impact in the distal position delivered approximately 16 times more microbeads and yielded approximately 20% more bacteria killing (for both CHX and CPC) than the 90° impact. These data suggest that high-velocity water microsprays can be used as an effective mechanism to deliver microparticles and antimicrobials inside S. mutans biofilms. High shear stresses generated at the biofilm-burst interface might have enhanced bead and antimicrobial delivery inside the remaining biofilm by combining forced advection into the biofilm matrix and physical restructuring of the biofilm itself. Further, the impact angle has potential to be optimized both for biofilm removal and active agents' delivery inside biofilm in those protected areas where some biofilm might remain.

Streptococcus mutans biofilm transient viscoelastic fluid behaviour during high-velocity microsprays.

Using high-speed imaging we assessed Streptococcus mutans biofilm-fluid interactions during exposure to a 60-ms microspray burst with a maximum exit velocity of 51m/s. S. mutans UA159 biofilms were grown for 72h on 10mm-length glass slides pre-conditioned with porcine gastric mucin. Biofilm stiffness was measured by performing uniaxial-compression tests. We developed an in-vitro interproximal model which allowed the parallel insertion of two biofilm-colonized slides separated by a distance of 1mm and enabled high-speed imaging of the removal process at the surface. S. mutans biofilms were exposed to either a water microspray or an air-only microburst. High-speed videos provided further insight into the mechanical behaviour of biofilms as complex liquids and into high-shear fluid-biofilm interaction. We documented biofilms extremely transient fluid behaviour when exposed to the high-velocity microsprays. The presence of time-dependent recoil and residual deformation confirmed the pivotal role of viscoelasticity in biofilm removal. The air-only microburst was effective enough to remove some of the biofilm but created a smaller clearance zone underlying the importance of water and the air-water interface of drops moving over the solid surface in the removal process. Confocal and COMSTAT analysis showed the high-velocity water microspray caused up to a 99.9% reduction in biofilm thickness, biomass and area coverage, within the impact area.

An experimental and computational study of the hydrodynamics of high-velocity water microdrops for interproximal tooth cleaning.

The flow field and local hydrodynamics of high-velocity water microdrops impacting the interproximal (IP) space of typodont teeth were studied experimentally and computationally. Fourteen-day old Streptococcus mutans biofilms in the IP space were treated by a prototype AirFloss delivering 115 µL of water at a maximum exit-velocity of 60 ms(-1) in a 33-ms burst. Using high-speed imaging, footage was generated showing the details of the burst, and demonstrating the removal mechanism of the biofilms. Footage was also generated to characterize the viscoelastic behavior of the biofilms when impacted by an air-only burst, which was compared to the water burst. Image analysis demonstrated the importance of fluid forces on the removal pattern of interdental biofilms. X-ray micro-Computed Tomography (µ-CT) was used to obtain 3D images of the typodont and the IP spaces. Computational Fluid Dynamics (CFD) simulations were performed to study the effect of changing the nozzle position and design on the hydrodynamics within the IP space. Results confirmed our previous data regarding the wall shear stress generated by high-velocity water drops which dictated the efficacy of biofilm detachment. Finally, we showed how CFD models could be used to optimize water drop or burst design towards a more effective biofilm removal performance.

Removal of interproximal dental biofilms by high-velocity water microdrops.

The influence of the impact of a high-velocity water microdrop on the detachment of Streptococcus mutans UA159 biofilms from the interproximal (IP) space of teeth in a training typodont was studied experimentally and computationally. Twelve-day-old S. mutans biofilms in the IP space were exposed to a prototype AirFloss delivering 115 µL water at a maximum exit velocity of 60 m/sec in a 30-msec burst. Using confocal microscopy and image analysis, we obtained quantitative measurements of the percentage removal of biofilms from different locations in the IP space. The 3D geometry of the typodont and the IP spaces was obtained by micro-computed tomography (µ-CT) imaging. We performed computational fluid dynamics (CFD) simulations to calculate the wall shear stress (τw ) distribution caused by the drops on the tooth surface. A qualitative agreement and a quantitative relationship between experiments and simulations were achieved. The wall shear stress (τw ) generated by the prototype AirFloss and its spatial distribution on the teeth surface played a key role in dictating the efficacy of biofilm removal in the IP space.