Effect of molecular mass and degree of deacetylation of chitosan on adsorption of Streptococcus sobrinus 6715 to saliva treated hydroxyapatite

Biofilm formation following chitosan-based varnish or chlorhexidine-fluoride varnish application in patients undergoing fixed orthodontic treatment: a double blinded randomised controlled trial

BACKGROUND

Orthodontic treatment poses an increased risk of plaque accumulation and demineralisation of enamel leading to white spot lesion around the brackets. This parallel arm trial aims to assess the degree of bacterial plaque formation adjacent to orthodontic brackets, following the application of a chitosan-based varnish or chlorhexidene-fluoride varnish.

METHODS

A total of 200 teeth from 20 patients undergoing fixed orthodontic therapy were assessed and biofilm formation around the brackets were recorded using the Bonded Bracket Index (Plaque index) at baseline and weekly for 6 weeks. The bacterial count and plaque pH at corresponding weekly intervals were also recorded. Following bracket bonding, the patients were cluster randomised to receive chitosan-based varnish-CHS (UNO Gel Bioschell, Germiphene corp., Brantford, Canada) or chlorhexidine-fluoride varnish-CFV (Cervitec F, Ivoclar Vivadent, Schaan, Liechtenstein) every week on the representative teeth respectively. BBI proportions were compared between groups at all time intervals using Chi square test. Mean plaque bacterial count and plaque pH were compared using Mann Whitney U test and Tukey's HSD test respectively.

RESULTS

Baseline characteristics were similar between the groups: Mean age was CHS = 23 and CFV = 21; male to female ratio was CHS = 5/5, CFV = 7/3. At the end of 6 weeks, chitosan-based varnish performed equal to chlorhexidine-fluoride varnish (P > 0.05) with 98% and 95% of teeth with acceptable scores respectively. The plaque bacterial count significantly reduced at 6 weeks for both varnish compared to the baseline; The value for CHS was 0.43 ± 0.4 × 104 and CFV was 0.77 ± 0.64 × 104 CFU (P < 0.05), with no difference between both the varnishes. Both varnishes had no effect on the plaque pH that remained neutral.

CONCLUSION

This trial showed that both chitosan-based varnish and chlorhexidine-fluoride varnish reduced bacterial count, while the plaque pH remained neutral over a period of six weeks in patients undergoing fixed orthodontic therapy. The anti-plaque effects of the natural biopolymeric chitosan-based varnish was similar to that of chlorhexidine-fluoride varnish, a known chemotherapeutic agent. Registration: This trial protocol was registered with https://www.ctri.nic.in (CTRI/2019/05/018896). (Date of registration 02/05/2019).

PROTOCOL

The protocol was not published before trial commencement.

Anti-Biofouling Coatings on the Tooth Surface and Hydroxyapatite

Dental plaque is one type of biofouling on the tooth surface that consists of a diverse population of microorganisms and extracellular matrix and causes oral diseases and even systematic diseases. Numerous studies have focused on preventing bacteria and proteins on tooth surfaces, especially with anti-biofouling coatings. Anti-biofouling coatings can be stable and sustainable over the long term on the tooth surface in the complex oral environment. In this review, numerous anti-biofouling coatings on the tooth surface and hydroxyapatite (as the main component of dental hard tissue) were summarized based on their mechanisms, which include three major strategies: antiprotein and antibacterial adhesion through chemical modification, contact killing through the modification of antimicrobial agents, and antibacterial agent release. The first strategy of coatings can resist the adsorption of proteins and bacteria. However, these coatings use passive strategies and cannot kill bacteria. The second strategy can interact with the cell membrane of bacteria to cause bacterial death. Due to the possibility of delivering a high antibacterial agent concentration locally, the third strategy is recommended and will be the trend of local drug use in dentistry in the future.

Antifungal activity of different molecular weight chitosans against planktonic cells and biofilm of Sporothrix brasiliensis

Sporotrichosis, caused by Sporothrix schenckii complex species, is the most prevalent subcutaneous mycosis in many areas of Latin America. Chitosan has been used as an antifungal agent; however the effects of the molecular weight (MW) of chitosan (i.e. high (HMW), medium (MMW) and low (LMW) molecular weight chitosan) on S. brasiliensis has not been well described, particularly on biofilms. Effects on the planktonic form activity of S. brasiliensis were quantified by broth microdilution, while anti-biofilm activity was quantified by measuring metabolic activity via XTT (2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide and biomass formation (crystal violet). The molecular weight of chitosan modulated its effect on the planktonic form of S. brasiliensis, presenting lower MIC values for LMW chitosan. With regards both the adhesive and mature phases of biofilm, the LMW chitosan reduced biomass and metabolic activity most effectively. This study confirms the effects of the molecular weight and deacetylation degree of chitosan on its antifungal properties for potentially pathogenic fungi.

Novel Approaches to the Control of Oral Microbial Biofilms

Effective management of biofilm-related oral infectious diseases is a global challenge. Oral biofilm presents increased resistance to antimicrobial agents and elevated virulence compared with planktonic bacteria. Antimicrobial agents, such as chlorhexidine, have proven effective in the disruption/inhibition of oral biofilm. However, the challenge of precisely and continuously eliminating the specific pathogens without disturbing the microbial ecology still exists, which is a major factor in determining the virulence of a multispecies microbial consortium and the consequent development of oral infectious diseases. Therefore, several novel approaches are being developed to inhibit biofilm virulence without necessarily inducing microbial dysbiosis of the oral cavity. Nanoparticles, such as pH-responsive enzyme-mimic nanoparticles, have been developed to specifically target the acidic niches within the oral biofilm where tooth demineralization readily occurs, in effect controlling dental caries. Quaternary ammonium salts (QAS) such as dimethylaminododecyl methacrylate (DMADDM), when incorporated into dental adhesives or resin composite, have also shown excellent and durable antimicrobial activity and thus could effectively inhibit the occurrence of secondary caries. In addition, custom-designed small molecules, natural products and their derivatives, as well as basic amino acids such as arginine, have demonstrated ecological effects by modulating the virulence of the oral biofilm without universally killing the commensal bacteria, indicating a promising approach to the management of oral infectious diseases such as dental caries and periodontal diseases. This article aims to introduce these novel approaches that have shown potential in the control of oral biofilm. These methods may be utilized in the near future to effectively promote the clinical management of oral infectious diseases and thus benefit oral health.

Cosmetics and Cosmeceutical Applications of Chitin, Chitosan and Their Derivatives

Marine resources are well recognized for their biologically active substances with great potential applications in the cosmeceutical industry. Among the different compounds with a marine origin, chitin and its deacetylated derivative—chitosan—are of great interest to the cosmeceutical industry due to their unique biological and technological properties. In this review, we explore the different functional roles of chitosan as a skin care and hair care ingredient, as an oral hygiene agent and as a carrier for active compounds, among others. The importance of the physico-chemical properties of the polymer in its use in cosmetics are particularly highlighted. Moreover, we analyse the market perspectives of this polymer and the presence in the market of chitosan-based products.

Chitosan adsorption to salivary pellicles

The salivary pellicle is a negatively charged protein film, to which oral bacteria readily adhere. Chitosans are cationic biomolecules with known antimicrobial properties that can be modified in different ways to enhance its antimicrobial activity. Here, we determined the changes in surface chemical composition using X-ray photoelectron spectroscopy (XPS), in hydrophobicity by analyzing water contact angles, in charge through measuring streaming potentials, and evaluated morphology using atomic force microscopy (AFM), of salivary pellicles upon adsorption of different chitosans. The adsorption of chitosans to pellicles was chemically evident from altered carbon functionalities and the presence of an N(1s) peak at 401.1 eV as a result of protonated amines in XPS. Chitosan adsorption made the pellicle (zeta potential of untreated pellicles 29 mV) positively charged and more hydrophobic. A chemically modified chitosan (CL) and an unmodified chitosan (UC) caused aggregation of adsorbed salivary proteins, and AFM revealed clumps of protein after treatment with these chitosans, yielding an increase in pellicle surface roughness from 5.1 nm to between 16.3 and 35.6 nm for CL and UC, respectively. In summary, chitosans have a clear tendency to adsorb to salivary pellicles with a profound effect on the surface properties of the pellicle. Therefore, chitosans may provide anchoring molecules to affix antimicrobials to pellicle surfaces.

Effect of chitosan rinsing on reduction of dental plaque formation

The purpose of the present study was to investigate whether the use of a chitosan mouthrinse could be efficacious in reducing plaque and saliva mutans streptococci level. A randomized crossover clinical trial was performed to evaluate the effect of a rinse with 0.5% chitosan for 14 days on plaque formation and mutans streptococci counts in saliva. Twenty-four subjects were randomly assigned either the chitosan rinse or a placebo rinse in addition to their usual oral hygiene procedures. Following the baseline examination, each subject was given a prophylaxis. They were instructed to rinse with 20 ml of the mouthrinse twice daily for 30 seconds. Plaque scores were measured after a 14-day rinsing period, and mutans streptococci counts in saliva were also determined at the start and the end of the each rinsing period. The procedures were repeated with the alternate rinse after a 14-day washout period. Rinsing with 0.5% chitosan was significantly more effective in plaque reduction using the Quigley & Hein Index (chitosan: 1.44, placebo: 1.62, p < 0.001) and Plaque Severity Index (chitosan: 0.138, placebo: 0.186, p = 0.003). The mutans streptococci count in saliva was less after the chitosan rinsing (chi 2 cal = 13.51, p = 0.035) than placebo rinsing. In conclusion, the chitosan rinsing was effective in reducing plaque formation and counts of salivary mutans streptococci after a 14-day rinsing period. These results would appear to warrant further investigation into the potential value of chitosan as an effective anti-plaque agent for use in oral hygiene products.