In vivo biofilm formation on stainless steel bonded retainers during different oral health-care regimens

Retention wires permanently bonded to the anterior teeth are used after orthodontic treatment to prevent the teeth from relapsing to pre-treatment positions. A disadvantage of bonded retainers is biofilm accumulation on the wires, which produces a higher incidence of gingival recession, increased pocket depth and bleeding on probing. This study compares in vivo biofilm formation on single-strand and multi-strand retention wires with different oral health-care regimens. Two-centimetre wires were placed in brackets that were bonded to the buccal side of the first molars and second premolars in the upper arches of 22 volunteers. Volunteers used a selected toothpaste with or without the additional use of a mouthrinse containing essential oils. Brushing was performed manually. Regimens were maintained for 1 week, after which the wires were removed and the oral biofilm was collected to quantify the number of organisms and their viability, determine the microbial composition and visualize the bacteria by electron microscopy. A 6-week washout period was employed between regimens. Biofilm formation was reduced on single-strand wires compared with multi-strand wires; bacteria were observed to adhere between the strands. The use of antibacterial toothpastes marginally reduced the amount of biofilm on both wire types, but significantly reduced the viability of the biofilm organisms. Additional use of the mouthrinse did not result in significant changes in biofilm amount or viability. However, major shifts in biofilm composition were induced by combining a stannous fluoride- or triclosan-containing toothpaste with the mouthrinse. These shifts can be tentatively attributed to small changes in bacterial cell surface hydrophobicity after the adsorption of the toothpaste components, which stimulate bacterial adhesion to the hydrophobic oil, as illustrated for a Streptococcus mutans strain.

Osteoblast integration of dental implant materials after challenge by sub-gingival pathogens: a co-culture study in vitro

Sub-gingival anaerobic pathogens can colonize an implant surface to compromise osseointegration of dental implants once the soft tissue seal around the neck of an implant is broken. In vitro evaluations of implant materials are usually done in monoculture studies involving either tissue integration or bacterial colonization. Co-culture models, in which tissue cells and bacteria battle simultaneously for estate on an implant surface, have been demonstrated to provide a better in vitro mimic of the clinical situation. Here we aim to compare the surface coverage by U2OS osteoblasts cells prior to and after challenge by two anaerobic sub-gingival pathogens in a co-culture model on differently modified titanium （Ti）, titanium-zirconium （TiZr） alloys and zirconia surfaces. Monoculture studies with either U2OS osteoblasts or bacteria were also carried out and indicated significant differences in biofilm formation between the implant materials, but interactions with U2OS osteoblasts were favourable on all materials. Adhering U2OS osteoblasts cells, however, were significantly more displaced from differently modified Ti surfaces by challenging sub-gingival pathogens than from TiZr alloys and zirconia variants. Combined with previous work employing a co-culture model consisting of human gingival fibroblasts and supra-gingival oral bacteria, results point to a different material selection to stimulate the formation of a soft tissue seal as compared to preservation of osseointegration under the unsterile conditions of the oral cavity.

Recent advances and future challenges in the use of nanoparticles for the dispersal of infectious biofilms

Increasing occurrence of intrinsically antimicrobial-resistant,human pathogens and the protective biofilm-mode in which they grow,dictates a need for the alternative control of infectious biofilms.Biofilm bacteria utilize dispersal mechanisms to detach parts of a biofilm as part of the biofilm life-cycle during times of nutrient scarcity or overpopulation.We here identify recent advances and future challenges in the development of dispersants as a new infection-control strategy.Deoxyribonuclease(DNase)and other extracellular enzymes can disrupt the extracellular matrix of a biofilm to cause dispersal.Also,a variety of small molecules,reactive oxygen species,nitric oxide releasing compounds,peptides and molecules regulating signaling pathways in biofilms have been described as dispersants.On their own,dispersants do not inhibit bacterial growth or kill bacterial pathogens.Both natural,as well as artificial dispersants,are unstable and hydrophobic which necessitate their encapsulation in smart nanocarriers,like p H-responsive micelles,liposomes or hydrogels.Depending on their composition,nanoparticles can also possess intrinsic dispersant properties.Bacteria dispersed from an infectious biofilm end up in the blood circulation where they are cleared by host immune cells.However,this sudden increase in bacterial concentration can also cause sepsis.Simultaneous antibiotic loading of nanoparticles with dispersant properties or combined administration of dispersants and antibiotics can counter this threat.Importantly,biofilm remaining after dispersant administration appears more susceptible to existing antibiotics.Being part of the natural biofilm life-cycle,no signs of"dispersant-resistance"have been observed.Dispersants are therewith promising for the control of infectious biofilms.

Possibilities and impossibilities of magnetic nanoparticle use in the control of infectious biofilms

Targeting of chemotherapeutics towards a tumor site by magnetic nanocarriers is considered promising in tumor-control.Magnetic nanoparticles are also considered for use in infection-control as a new means to prevent antimicrobial resistance from becoming the number one cause of death by the year 2050.To this end,magnetic nanoparticles can either be loaded with an antimicrobial for use as a delivery vehicle or modified to acquire intrinsic antimicrobial properties.Magnetic nanoparticles can also be used for the local generation of heat to kill infectious microorganisms.Although appealing for tumor-and infectioncontrol,injection in the blood circulation may yield reticuloendothelial uptake and physical obstruction in organs that yield reduced targeting efficiency.This can be prevented with suitable surface modification.However,precise techniques to direct magnetic nanoparticles towards a target site are lacking.The problem of precise targeting is aggravated in infection-control due to the micrometer-size of infectious biofilms,as opposed to targeting of nanoparticles towards centimeter-sized tumors.This review aims to identify possibilities and impossibilities of magnetic targeting of nanoparticles for infection-control.We first review targeting techniques and the spatial resolution they can achieve as well as surface-chemical modifications of magnetic nanoparticles to enhance their targeting efficiency and antimicrobial efficacy.It is concluded that targeting problems encountered in tumor-control using magnetic nanoparticles,are neglected in most studies on their potential application in infection-control.Currently biofilm targeting by smart,self-adaptive and pH-responsive,antimicrobial nanocarriers for instance,seems easier to achieve than magnetic targeting.This leads to the conclusion that magnetic targeting of nanoparticles for the control of micrometer-sized infectious biofilms may be less promising than initially expected.However,using propulsion rather than precise targeting of magnetic nanoparticles in a magnetic field to traverse through infectious-biofilms can create artificial channels for enhanced antibiotic transport.This is identified as a more feasible,innovative application of magnetic nanoparticles in infection-control than precise targeting and distribution of magnetic nanoparticles over the depth of a biofilm.

In-biofilm generation of nitric oxide using a magnetically-targetable cascade-reaction container for eradication of infectious biofilms

Cascade-reaction chemistry can generate reactive-oxygen-species that can be used for the eradication of infectious biofilms.However,suitable and sufficient oxygen sources are not always available near an infection site,while the reactive-oxygen-species generated are short-lived.Therefore,we developed a magnetic cascade-reaction container composed of mesoporous Fe_(3)O_(4)@SiO_(2) nanoparticles containing glucose-oxidase and L-arginine for generation of reactive-oxygen-species.Glucose-oxidase was conjugated with APTES facilitating coupling to Fe_(3)O_(4)@SiO_(2) nanoparticles and generation of H_(2)O_(2) from glucose.L-arginine was loaded into the nanoparticles to generate NO from the H_(2)O_(2) generated.Using an externally-applied magnetic field,cascade-reaction containers could be homogeneously distributed across the depth of an infectious biofilm.Cascade-reaction containers with coupled glucose-oxidase were effective in killing planktonic,Gram-positive and Gram-negative bacteria.Additional efficacy of the L-arginine based second cascade-reaction was only observed when H_(2)O_(2) as well as NO were generated in-biofilm.In vivo accumulation of cascade-reaction containers inside abdominal Staphylococcus aureus biofilms upon magnetic targeting was observed real-time in living mice through an implanted,intra-vital window.Moreover,vancomycin-resistant,abdominal S.aureus biofilms could be eradicated consuming solely endogenous glucose,without any glucose addition.Herewith,a new,non-antibiotic-based infection-control strategy has been provided,constituting a welcome addendum to the shrinking clinical armamentarium to control antibiotic-resistant bacterial infections.