Dynamic killing effectiveness of mouthrinses and a D-enantiomeric peptide on oral multispecies biofilms grown on dental restorative material surfaces

Constructing two bifunctional tooth-targeting antimicrobial peptides for caries management: an in vitro study

OBJECTIVES

Caries is a significant public health challenge. Herein, novel tooth-targeting antimicrobial peptides (HABPs@AMPs) were developed by combining the antimicrobial peptide DJK-5 with hydroxyapatite (HA) binding peptides, providing a potential new strategy for caries management.

MATERIALS AND METHODS

The minimal inhibitory concentration (MIC100) and minimal biofilm inhibitory concentration (MBIC100) values of HABPs@AMPs were determined via micro-broth dilution and crystal violet staining. The affinities of the peptides for HA were measured by mass depletion, and the abilities of peptides to inhibit Streptococcus mutans (S. mutans) biofilm formation and kill 3-day-old S. mutans biofilms were evaluated in HA disk and tooth slice biofilm models through confocal laser scanning microscopy. Biocompatibility with human gingival fibroblasts was evaluated via CCK8 assays.

RESULTS

The best performing peptides, DJK-5@SVA and SVA@DJK-5 exhibited MIC100 and MBIC100 values of 31.25 µg/mL, similar to DJK-5. DJK-5@linker2@YSL had the highest affinity for HA, followed by YSL@DJK-5, DJK-5@linker1@YSL, and DJK-5@SVA. Moreover, the biofilms on HABPs@DJK-5 coated surfaces had more dead bacteria by volume than those in the DJK-5 and SVA groups (p < 0.05). DJK-5@SVA outperformed SVA@DJK-5 and DJK-5 in killing 3-day-old S. mutans biofilms (p < 0.05). With the exception of established biofilms on tooth slices, DJK-5@SVA exhibited greater killing efficiency in the bottom half of the biofilms than in the top half. The CCK-8 assay results confirmed peptides' biocompatibility.

CONCLUSIONS

DJK-5@SVA with good affinity for HA, has excellent biocompatibility and efficacy against S. mutans biofilms.

CLINICAL RELEVANCE

HABPs@AMPs with effective inhibitory effects on the growth of S. mutans and biofilm formation, contributing to intraoral targeted application AMPs and providing a new strategy for caries management.

Natural Antimicrobial Peptides and Their Synthetic Analogues for Effective Oral Microflora Control and Oral Infection Treatment-The Role of Ceragenins in the Development of New Therapeutic Methods

Oral diseases, both acute and chronic, of infectious or non-infectious etiology, represent some of the most serious medical problems in dentistry. Data from the literature increasingly indicate that changes in the oral microbiome, and therefore, the overgrowing of pathological microflora, lead to a variety of oral-localized medical conditions such as caries, gingivitis, and periodontitis. In recent years, compelling research has been devoted to the use of natural antimicrobial peptides as therapeutic agents in the possible treatment of oral diseases. This review focuses on the potential of ceragenins (CSAs), which are lipid analogs of natural antimicrobial peptides, as molecules for the development of new methods for the prevention and treatment of oral diseases. Studies to date indicate that ceragenins, with their spectrum of multidirectional biological activities, including antimicrobial, tissue regeneration-stimulating, anti-inflammatory, and immunomodulatory properties, are strong candidates for further development of oral formulations. However, many of the beneficial properties of ceragenins require confirmation in experimental conditions reproducing the oral environment to fully determine their application potential. Their transition to practical use also requires more advanced testing of these molecules in clinical trials, which have only been conducted in limited numbers to date.

The effects of antimicrobial peptides buCaTHL4B and Im-4 on infectious root canal biofilms

Purpose

The primary cause of pulp and periapical diseases is the invasion of bacteria into the root canal, which results from the continuous destruction of dental hard tissues. Effective management of infections during root canal therapy necessitates effectively irrigation. This study aims to investigate the effects of two antimicrobial peptides (AMPs), buCaTHL4B and Im-4, on root canal biofilms in vitro.

Methods

Two-species biofilms (Enterococcus faecalis and Fusobacterium nucleatum) were selected and anaerobically cultivated. The following treatments were applied: 10 μg/mL buCaTHL4B, 10 μg/mL Im-4, 5 μg/mL buCaTHL4B, 5 μg/mL Im-4, 1 μg/mL buCaTHL4B, 1 μg/mL Im-4, 1% NaOCl, and sterile water. Each group was treated for 3 min. Subsequently, the two strains were co-cultured with 10 μg/mL buCaTHL4B, 10 μg/mL Im-4, 1% NaOCl, and sterile water for 24, 48, and 72 h. The biofilms were examined using confocal laser scanning microscopy (CLSM) with fluorescent staining, and the percentages of dead bacteria were calculated. Quantitative real-time PCR (qRT-PCR) was employed to assess the variations in bacterial proportions during biofilm formation.

Results

Compared to 1% NaOCl, 10 μg/mL buCaTHL4B or Im-4 exhibited significantly greater bactericidal effects on the two-species biofilms (p < 0.05), leading to their selection for subsequent experiments. Over a 48-hour period, 10 μg/mL Im-4 demonstrated a stronger antibiofilm effect than buCaTHL4B (p < 0.05). Following a 24-hour biofilm formation period, the proportion of F. nucleatum decreased while the proportion of E. faecalis increased in the sterile water group. In the buCaTHL4B and 1% NaOCl groups, the proportion of F. nucleatum was lower than that of E. faecalis (p < 0.05), whereas in the Im-4 group, the proportion of F. nucleatum was higher than that of E. faecalis (p < 0.05). The proportions of bacteria in the two AMPs groups gradually stabilized after 24 h of treatment.

Conclusion

buCaTHL4B and Im-4 exhibited remarkable antibacterial and anti-biofilm capabilities against pathogenic root canal biofilms in vitro, indicating their potential as promising additives to optimize the effectiveness of root canal treatment as alternative irrigants.

Trans-Cinnamaldehyde Inhibition of Pyruvate Dehydrogenase: Effects on Streptococcus mutans Carbohydrate Metabolism

Dental caries is a chronic oral infectious disease, and Streptococcus mutans (S. mutans) plays an important role in the formation of dental caries. Trans-cinnamaldehyde (CA) exhibits broad-spectrum antibacterial activity; however, its target and mechanism of action of CA on S. mutans needs to be further explored. In this study, it was verified that CA could inhibit the growth and biofilm formation of S. mutans. Further proteomic analysis identified 33, 55, and 78 differentially expressed proteins (DEPs) in S. mutans treated with CA for 1, 2, and 4 h, respectively. Bioinformatics analysis showed that CA interfered with carbohydrate metabolism, glycolysis, pyruvate metabolism, and the TCA cycle, as well as amino acid metabolism of S. mutans. Protein interactions suggested that pyruvate dehydrogenase (PDH) plays an important role in the antibacterial effect of CA. Moreover, the upstream and downstream pathways related to PDH were verified by various assays, and the results proved that CA not only suppressed the glucose and sucrose consumption and inhibited glucosyltransferase (GTF) and lactate dehydrogenase (LDH) activities but also decreased the ATP production. Interestingly, the protein interaction, qRT-PCR, and molecular docking analysis showed that PDH might be the target of CA to fight S. mutans. In summary, the study shows that CA interferes with the carbohydrate metabolism of bacteria by inhibiting glycolysis and the tricarboxylic acid (TCA) cycle via binding to PDH, which verifies that PDH is a potential target for the development of new drugs against S. mutans.

Antimicrobial effects of surface pre-reacted glass-ionomer (S-PRG) eluate against oral microcosm biofilm

This study investigated the antimicrobial activity of surface pre-reacted glass ionomer eluate (S-PRG) against oral microcosm biofilms collected from the oral cavity of patients. Dental biofilm samples were collected from three volunteers to form microcosm biofilms in vitro. Initially, screening tests were carried out to determine the biofilm treatment conditions with S-PRG eluate. The effects of a daily treatment for 5 min using three microcosm biofilms from different patients was then evaluated. For this, biofilms were formed on tooth enamel specimens for 120 h. Biofilms treated with 100% S-PRG for 5 min per day for 5 days showed a reduction in the number of total microorganisms, streptococci and mutans streptococci. SEM images confirmed a reduction in the biofilm after treatment. Furthermore, S-PRG also reduced lactic acid production. It was concluded that S-PRG eluate reduced the microbial load and lactic acid production in oral microcosm biofilms, reinforcing its promising use as a mouthwash agent.

Design and evaluation of an MMP-9-responsive hydrogel for vital pulp therapy

OBJECTIVE

To design and evaluate a matrix metalloproteinase 9 (MMP-9)-responsive hydrogel for vital pulp therapy.

METHODS

A peptide linker with optimized sensitivity toward MMP-9 was crosslinked with 4-arm poly (ethylene glycol)-norbornene (PEG-NB) by thiol-norbornene photo-polymerization. This resulted in the formation of a hydrogel network in which the peptide IDR-1002 was incorporated. Hydrogel characterization and gelation kinetics were examined with Fourier-transform infrared spectroscopy, scanning electron microscopy, rheological testing, and swelling evaluation. Hydrogel degradation was examined through multiple exposure to pre-activated MMP-9, to simulate flare-ups of dental pulp inflammation. The IDR-1002 released from degraded hydrogels was measured with high-performance liquid chromatography. Effect of IDR-1002 released from hydrogels on one-week-old multispecies oral biofilms was evaluated using confocal laser scanning microscopy.

RESULTS

MMP-9-responsive, injectable, and photo-crosslinkable hydrogels were successfully synthesized. When hydrogel degradation and release of IDR-1002 were examined with exposure to pre-activated MMP-9, IDR-1002 release was significantly correlated with elevated levels of MMP-9 (p < 0.05). The effectiveness of IDR-1002 in killing bacteria in multispecies oral biofilms was significantly enhanced when the hydrogels were immersed in 10 nM or 20 nM pre-activated MMP-9, compared to immersion in phosphate-buffered saline (p < 0.05).

CONCLUSIONS

The MMP-9-responsive hydrogel is a promising candidate for on-demand delivery of bioactive agent in vital pulp therapy.

CLINICAL SIGNIFICANCE

MMP-9 is one of the most important diagnostic and prognostic biomarkers for pulpitis. An MMP-9-responsive hydrogel has potential to be used as an in-situ on-demand release system for the diagnosis and treatment of dental pulp inflammation.

Antibiofilm peptides enhance the corrosion resistance of titanium in the presence of Streptococcus mutans

Titanium alloys have gained popularity in implant dentistry for the restoration of missing teeth and related hard tissues because of their biocompatibility and enhanced strength. However, titanium corrosion and infection caused by microbial biofilms remains a significant clinical challenge leading to implant failure. This study aimed to evaluate the effectiveness of antibiofilm peptides 1018 and DJK-5 on the corrosion resistance of titanium in the presence of Streptococcus mutans. Commercially pure titanium disks were prepared and used to form biofilms. The disks were randomly assigned to different treatment groups (exposed to S. mutans supplied with sucrose) including a positive control with untreated biofilms, peptides 1018 or DJK-5 at concentrations of 5 μg/mL or 10 μg/mL, and a negative control with no S. mutans. Dynamic biofilm growth and pH variation of all disks were measured after one or two treatment periods of 48 h. After incubation, the dead bacterial proportion, surface morphology, and electrochemical behaviors of the disks were determined. The results showed that peptides 1018 and DJK-5 exhibited significantly higher dead bacterial proportions than the positive control group in a concentration dependent manner (p < 0.01), as well as far less defects in microstructure. DJK-5 at 10 μg/mL killed 84.82% of biofilms and inhibited biofilm growth, preventing acidification due to S. mutans and maintaining a neutral pH. Potential polarization and electrochemical impedance spectroscopy data revealed that both peptides significantly reduced the corrosion and passive currents on titanium compared to titanium surfaces with untreated biofilms, and increased the resistance of the passive film (p < 0.05), with 10 μg/mL of DJK-5 achieving the greatest effect. These findings demonstrated that antibiofilm peptides are effective in promoting corrosion resistance of titanium against S. mutans, suggesting a promising strategy to enhance the stability of dental implants by endowing them with antibiofilm and anticorrosion properties.

An In Vitro Study: Does Adding Iodine Potassium Iodide and Cetrimide to Calcium Hydroxide Paste Enhance Its Antimicrobial Effect Against Oral Biofilms?

Objectives This study aimed to evaluate the antibiofilm effect of calcium hydroxide (CH), 0.5% iodine potassium iodide (IKI), and 0.5% cetrimide (CTR), alone and in combinations on one-week and three-week-old biofilms. Materials and methods Gingival plaque was collected, and biofilms were grown in vitro anaerobically. Biofilms were exposed to each of the three medicaments and their combinations for one day, one week, and two weeks. Proportions of dead and live bacteria in the biofilms were evaluated. Results The killing of bacteria by different medicaments in the three-week-old biofilm was lower than in the one-week-old biofilm (p<0.05). The efficacy of IKI and CTR in killing bacteria was weaker than that of CH, but the highest efficacy in killing was achieved when all three were combined (p<0.05). There was no significant difference in the antibiofilm effect between a day's exposure to the mixture of the three medicaments and one or two weeks of treatment with CH alone (p>0.05). Conclusions Three-week-old biofilms are more resistant to medicaments than one-week-old biofilms. Combining IKI and CTR with CH resulted in a stronger antibiofilm effect than using CH alone. Mixing the three medicaments may enable obtaining the desired clinical effect in a shorter exposure time.

Influence of a D-enantiomeric peptide on the anticorrosion ability of titanium with different surface roughness against Streptococcus mutans biofilms

OBJECTIVE

To investigate the effectiveness of a d-enantiomeric antibiofilm peptide (DJK-5) on the anticorrosion ability of titanium (Ti) with different surface roughness against Streptococcus mutans biofilms.

METHODS

Commercially pure Ti disks with machined (MA, smooth) or sandblasted + acid-etched (SLA, rough) surfaces were prepared and characterized. All disks were divided into three groups: a positive control (PC) group with S. mutans, a DJK-5-treated group, and a negative control (NC) group without S. mutans. Biofilm formation and corrosion on Ti surfaces were determined by confocal laser scanning microscopy and scanning electron microscopy after 2 and 6 days, and the electrochemical properties were evaluated.

RESULTS

Ten μg/mL of DJK-5 killed 83.3 % and 87.4 % of biofilms on SLA and MA Ti surfaces, respectively after 2 days, and 72.9 % and 77.7 % after 6 days, with more bacteria surviving on SLA surfaces with higher roughness (p < 0.05). DJK-5 treatment induced less surface defects with tiny pit corrosion than PC. DJK-5 treatment when compared to PC, led to electrochemical properties more reflecting NC surfaces, including significantly less negative corrosion potential, lower corrosion current, and higher passive film resistance (p < 0.05). SLA surfaces exhibited higher current density and lower resistance than MA surfaces (p < 0.05).

CONCLUSION

DJK-5 effectively enhanced the corrosion resistance of Ti with different surface roughness while killing S. mutans biofilms, and smooth surfaces were more susceptible to peptide treatment.

CLINICAL SIGNIFICANCE

The antibiofilm peptide is promising for promoting the anticorrosion ability of Ti against biofilms, thereby preventing biofilm-related infections.

Effects of DJK-5 and chlorhexidine on exopolysaccharide volume and pH in oral biofilms

BACKGROUND

Exopolysaccharides (EPS) are essential constituents of the extracellular matrix within oral biofilms and are significantly influenced by the local microenvironment. This study aimed to investigate the impact of two distinct antimicrobial agents, DJK-5 and chlorhexidine (CHX), on the EPS volume and pH levels in oral biofilms.

METHODS

Oral biofilms obtained from two donors were cultured on hydroxyapatite discs for durations of 3 days, 1 week, 2 weeks, 3 weeks, and 4 weeks. Subsequently, these biofilms were subjected to treatment with 10 µg/mL DJK-5 or 2% CHX for 3 min. The impact of these antimicrobial treatments on factors such as the proportion of dead bacterial, in situ pH, and EPS volume within the biofilms was assessed using corresponding fluorescent probes. The examination was carried out utilizing confocal laser scanning microscopy, and the resulting images were analyzed with a focus on the upper and lower layers of the biofilm, respectively.

RESULTS

DJK-5 exhibited a more potent bactericidal effect compared to CHX across the 3-day to 4-week duration of the biofilm (P < 0.05). The biofilms were acidic, with the upper layer being less acidic than the lower layer (P < 0.05). Both antimicrobial agents increased the pH, but DJK-5 had a greater effect than CHX (P < 0.05). The volume of EPS was significantly lower in DJK-5 treated biofilms compared to that of CHX, regardless of age or layer (P < 0.05).

CONCLUSION

DJK-5 exhibited superior effectiveness in reducing viable bacteria and EPS volume, as well as in raising extracellular pH, as compared to chlorhexidine.

Trans-cinnamaldehyde loaded chitosan based nanocapsules display antibacterial and antibiofilm effects against cavity-causing Streptococcus mutans

Background

Dental caries is a multifactorial disease, and the bacteria such as Streptococcus mutans (S. mutans) is one of the risk factors. The poor effect of existing anti-bacterial is mainly related to drug resistance, the short time of drug action, and biofilm formation.

Methods

To address this concern, we report here on the cinnamaldehyde (CA) loaded chitosan (CS) nanocapsules (CA@CS NC) sustained release CA for antibacterial treatment. The size, ζ-potential, and morphology were characterized. The antibacterial activities in vitro were studied by growth curve assay, pH drop assay, biofilm assay, and qRT-PCR In addition, cytotoxicity assay, organ index, body weight, and histopathology results were analyzed to evaluate the safety and biocompatibility in a rat model.

Results

CA@CS NC can adsorb the bacterial membrane due to electronic interaction, releasing CA slowly for a long time. At the same time, it has reliable antibacterial activity against S. mutans and downregulated the expression levels of QS, virulence, biofilm, and adhesion genes. In addition, it greatly reduced the cytotoxicity of CA and significantly inhibited dental caries in rats without obvious toxicity.

Conclusion

Our results showed that CA@CS NC had antibacterial and antibiofilm effects on S. mutans and inhibit dental caries. Besides, it showed stronger efficacy and less toxicity, and was able to adsorb bacteria releasing CA slowly, providing a new nanomaterial solution for the treatment of dental caries.

Dual effectiveness of a novel all-in-one endodontic irrigating solution in antibiofilm activity and smear layer removal

The continuous destruction of dental hard tissues increases the risk of bacterial invasion, which leads to pulp infections. Irrigation is critical for successful root canal treatment in terms of infection control. However, no single irrigant covers all of the functions demanded, including antibiofilm and tissue-dissolving activities. The aim of this study was to investigate the antimicrobial properties of Triton, an all-in-one irrigant, on Enterococcus faecalis and multispecies oral biofilms in dentin canals, as well as its ability to remove the smear layer. Dentin blocks (192 specimens) were prepared from single-root human teeth and then assigned to 48 groups (24 groups for each biofilm type). Serial centrifugation was used for bacterial introduction into dentinal tubules. After 3 weeks, half of the specimens were created a uniform smear layer. The following treatments were applied: short time (separate): Triton, 6% NaOCl, 2% NaOCl, and water (all for 3 min); short time (combined): Triton (3 + 1 min), 6% NaOCl +17% EDTA (3 + 1 or 2 + 1 min), and 2% NaOCl +17% EDTA (3 + 1 min); and long time: Triton (3 + 3 min), 6% NaOCl (5 min), 6% NaOCl +17% EDTA (5 + 1 min), and water (3 + 3 min). Confocal laser scanning microscopy and scanning electron microscopy were employed to examine the antimicrobial activity and smear layer removal, respectively. The results revealed that despite the absence or presence of the smear layer, Triton (3 + 3 min) showed the highest killing for both tested biofilms (61.53%-72.22%) among all groups (p < 0.05). Furthermore, the smear layer was removed by Triton after 3 + 3 min, exposing open dentin canals. These findings demonstrated that Triton can provide dual benefits of antibiofilm and smear layer removal capabilities simultaneously, indicating a simplified and effective strategy for application in root canal treatment.

Evaluation of the Prevalence of White Spot Lesions During Fixed Orthodontic Treatment Among Patients Reporting for Correction of Malocclusion: A Prevalence Study

BACKGROUND

Despite recent breakthroughs in caries preventive measures, one of the biggest issues clinicians confront is preventing demineralization while undergoing orthodontic therapy. The buildup of plaques around orthodontic brackets over time causes white spot lesions (WSLs). The goal of the present research was to assess the prevalence of WSLs in patients undergoing orthodontic treatment before starting therapy and at six and 12 months into therapy, adopting the visual examination approach.

MATERIALS AND METHODS

We looked for WSLs on tooth surfaces gingival to an archwire because this is the area most likely to experience enamel demineralization during orthodontic treatment. The visual assessment was conducted using the following scale at baseline, six months, and 12 months for orthodontic patients: score 0: no demineralization or noticeable white patches on the surface; score 1: mild demineralization with a visible white spot but no surface disruption; score 2: moderate demineralization with a noticeable WSL that has a roughened surface but does not need repair; and score 3: severe demineralization with a noticeable WSL that needs repair. Fisher's exact test was used after a chi-square analysis to determine whether there were any differences between all three categories (six months, 12 months, and control).

RESULTS

The frequency of WSL in patients at 12 months of orthodontic treatment was 46.57%, while it was 11.86% in patients who just started orthodontic treatment. The difference was statistically significant (p = 0.01), showing that the frequency was greater in patients at 12 months of orthodontic treatment as compared to patients who had just started undergoing orthodontic treatment. The frequency of WSL in patients at six months of orthodontic treatment was 37.34%, while it was 11.86% in patients who just started orthodontic treatment. The difference was statistically significant (p = 0.03), showing that the frequency was greater in patients at six months of orthodontic treatment as compared to patients who had just started undergoing orthodontic treatment. The frequency of WSL in patients at six months of orthodontic treatment was 37.34%, while it was 46.57% in patients at 12 months of orthodontic treatment. The frequency was greater in patients at 12 months of orthodontic treatment as compared to patients at six months of orthodontic treatment; however, the difference was non-significant statistically (p = 0.76).

CONCLUSION

This clinical investigation revealed that the number of WSLs increased significantly during the first six months of treatment and then increased gradually until the final 12 months. During the first few months of treatment, doctors should assess the patients' dental hygiene habits and, if necessary, take further precautions to prevent demineralization.