Toxicity of chlorhexidine on odontoblast-like cells

Insights into the Cytotoxicity and Irritant Potential of Chlorhexidine Digluconate: An In Vitro and In Ovo Safety Screening

Chlorhexidine (CHX) represents one of the most commonly used antiseptics in dentistry and other medical-pharmaceutical fields due to its broad-spectrum antimicrobial activity. However, the potential toxic events arising from its common use in practice has become a subject of increasing concern. Thus, the present study was designed to investigate the potential toxicity of CHX digluconate at concentrations covering its antibacterial properties (0.0002-0.2%) in HGF primary gingival fibroblasts, HaCaT immortalized human keratinocytes, and JB6 Cl 41-5a epidermal cells, as well as its irritant action in ovo. Our results indicate that CHX exerted a concentration- and time-dependent cytotoxicity in all cell lines, which was evidenced by the reduction in cell viability, number, and confluence, damaged cell membrane integrity, impaired cell morphology, and specific apoptotic nuclear shape. The highest cytotoxicity was caused by CHX digluconate 0.02% and 0.2%, concentrations, at which an irritant effect on the chorioallantoic membrane was also observed. The novel findings revealed in this research contribute to the overall safety profile of CHX and stand as a basis for further investigations in this regard.

Efficacy and safety of erythritol air-polishing in implant dentistry: A systematic review

OBJECTIVES

Professional oral hygiene is essential to prevent peri-implant disease. Appropriate instruments should be employed for implant-supported restorations: they should effectively remove deposits without damaging dental implant surface. The aim of the present systematic review is to investigate the efficacy and safety of erythritol air-polishing in implant-supported rehabilitations, compared to alternative hygienic techniques.

MATERIALS AND METHODS

The guidelines reported in the indications of the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) were employed for this systematic review. The focused question was: 'what is the effect of erythritol air-polishing on dental implant surfaces regarding its cleansing efficacy and/or safety?' The final online search was conducted on 13 August 2023; MEDLINE-PubMed, Scopus and Cochrane Library were employed. Comparative in vitro or in vivo original studies were included.

RESULTS

The initial database search yielded 128 entries; the final selection comprised 15 articles. The risk of bias was evaluated using the Newcastle Ottawa scale (NOS), the Cochrane Handbook for Systematic Reviews of Interventions, GRADE method. Ultrasonic scaling with PEEK tips, glycine air-polishing and cold atmospheric plasma were the devices most frequently compared to erythritol powder in the included studies. Erythritol air-polishing appeared to be significantly more effective in reducing biofilm compared to other treatments, without causing any significant damage to the implant surface and peri-implant tissues, promoting a good biological response.

CONCLUSION

Erythritol air-polishing showed promising results for professional oral hygiene in implant-supported restorations. According to this systematic review, it is effective and safe for removing biofilm from titanium dental implants.

Anti-Candida activity and in vitro toxicity screening of antifungals complexed with β-cyclodextrin

The emergence of resistant fungal species and the toxicity of currently available antifungal drugs are relevant issues that require special consideration. Cyclodextrins inclusion complexes could optimize the antimicrobial activity of such drugs and create a controlled release system with few side effects. This study aimed to assess the in vitro toxicity and antifungal effectiveness of nystatin (Nys) and chlorhexidine (Chx) complexed or not with β-cyclodextrin (βCD). First, a drug toxicity screening was performed through the Artemia salina bioassay. Then, the minimum inhibitory concentrations (MICs) against Candida albicans were determined with the broth microdilution test. After MICs determination, the cytotoxicity of the drugs was evaluated through the methyl-thiazolyl-tetrazolium (MTT) and neutral red (NR) assays and through cell morphology analysis. The PROBIT analysis was used to determine the median lethal concentration (LC50), and the cell viability values were submitted to one-way analysis of variance(ANOVA)/Tukey (α = 0.05). Overall, the βCD-complexed antifungals were less toxic against A. salina than their raw forms, suggesting that inclusion complexes can reduce the toxicity of drugs. The MICs obtained were as follows: Nys 0.5 mg/L; Nys:βCD 4 mg/L; Chx 4 mg/L; and Chx:βCD 8 mg/L. Chx showed significant cytotoxicity (MTT: 12.9 ± 9.6%; NR: 10.6 ± 12.5%) and promoted important morphological changes. Cells exposed to the other drugs showed viability above 70% with no cellular damage. These results suggest that antifungals complexed with βCD might be a biocompatible option for the treatment of Candida-related infections.

Preventive strategies to reduce the rate of periprosthetic infections in total joint arthroplasty; a comprehensive review

The increasing frequency of total hip (THA) and knee arthroplasties (TKA) is marred by the rise in periprosthetic joint infections (PJIs) and surgical site infections (SSIs), with PJIs incurring costs over $1.62 billion as of 2020 and individual case management averaging $90,000. SSIs additionally burden the U.S. healthcare economy with billions in expenses annually. PJI prevalence in primary THA and TKA ranges from 0.5% to 2.4%, spiking to 20% in revisions and representing 25% of TKA revision causes. Projections estimate up to 270,000 annual PJI cases by 2030. Often caused by gram-positive bacteria, particularly methicillin-resistant staphylococci, these infections demand preventive measures. This review dissects PJI prevention across preoperative, intraoperative, and perioperative phases, aligning with evidence-based CDC and WHO guidelines. Preoperative measures include managing diabetes, obesity, tobacco use, Staphylococcus aureus screening and nasal decolonization, nutritional optimization, and management of inflammatory arthropathies. Intraoperatively, antibiotic prophylaxis, skin preparation, operative room environmental controls, surgical technique precision, and irrigation options are scrutinized. Perioperative concerns focus on anticoagulation, blood management, and infection risk mitigation. Integrating these strategies promotes a patient-centric care model, aiming to reduce PJI incidence, improve patient outcomes, and increase care cost-effectiveness in joint arthroplasty.

Implant Surface Technologies to Prevent Surgical Site Infections in Spine Surgery

Spine surgeries are occurring more frequently worldwide. Spinal implant infections are one of the most common complications of spine surgery, with a rate of 0.7% to 11.9%. These implant-related infections are a consequence of surface polymicrobial biofilm formation. New technologies to combat implant-related infections are being developed as their burden increases; however, none have reached the market stage in spine surgery. Conferring antimicrobial properties to biomaterials relies on either surface coating (physical, chemical, or combined) or surface modification (physical, chemical, or combined). Such treatment can also result in toxicity and the progression of antimicrobial resistance. This narrative review will discuss "late-stage" antimicrobial technologies (mostly validated in vivo) that use these techniques and may be incorporated onto spine implants to decrease the burden of implant-related health care-acquired infections (HAIs). Successfully reducing this burden will greatly improve the quality of life in spine surgery. Familiarity with upcoming surface technologies will help spine surgeons understand the anti-infective strategies designed to address the rapidly worsening challenge of implant-related health care-acquired infections.

Effect of Commercial Children's Mouthrinses and Toothpastes on the Viability of Neonatal Human Melanocytes: An In Vitro Study

In this study, we examined the cytotoxic effects of six commercial children's mouthrinses (designated as #1, #2, #3, #4, #5, and #6) and four commercial children's toothpastes (designated as #1, #2, #3, and #4) on primary human neonatal melanocytes that were used as a representative model for oral melanocytes. Mouthrinses diluted directly with culture medium (1:2, 1:5, 1:10, 1:100, and 1:1000) were added to monolayers of melanocytes for 2 min, followed by 24 h recovery, after which MTS cytotoxicity assay was conducted. The extracts of each toothpaste were prepared (50% w/v), diluted in culture medium (1:2, 1:5, 1:10, 1:50, 1:100, and 1:1000), and added to cell monolayers for 2 min (standard brushing time), followed by an analysis of cell viability after 24 h. Results showed that all mouthrinses except mouthrinse #4 showed significantly greater loss of cell viability, ascribed to cetylpyridinium chloride (CPC) that induced significant cytotoxicity to melanocytes (IC50 = 54.33 µM). In the case of toothpastes, the examination of cellular morphology showed that a 2 min exposure to all toothpaste extracts induced a concentration-dependent decline in cell viability, pronounced in toothpaste containing sodium lauryl sulfate (SLS) detergent. Further results suggested SLS to be the critical driver of cytotoxicity (IC50 = 317.73 µM). It is noteworthy that toothpaste #1 exhibited much lower levels of cytotoxicity compared to the other three toothpastes containing SLS. Taken together, these findings suggest that the melanocytotoxicity of children's mouthrinse (#4) and toothpaste (#1) is comparatively low. To the best of our knowledge, this is the first study to examine the impact of children's toothpastes and mouthrinses on neonatal primary human melanocytes. Future studies to investigate these findings in a realistic scenario replicating oral cavity conditions of the presence of microbiota, pellicle layer and saliva, and other cell types are warranted.

Augmented antiviral activity of chlorhexidine gluconate on herpes simplex virus type 1, H1N1 influenza A virus, and adenovirus in combination with salicylic acid

BACKGROUND

The excessive usage of chlorhexidine gluconate (CHG) as a broad-spectrum antimicrobial reagent can have a negative impact on the environment and on human health. The aim of this study was to investigate the effectiveness of some plant-derived compounds in reducing the CHG concentration required to exert its antiviral activity.

METHODS

Antiviral assays were conducted according to EN 14476 (2019) against herpes simplex virus type 1 (HSV-1), H1N1 influenza A virus, and adenovirus type 5 (Ad-5) as enveloped and non-enveloped viral models to assess the synergistic interaction of CHG and natural additive compounds.

RESULTS

The effective concentration of 0.247 mM CHG against HSV-1 was decreased tenfold in combination with 0.0125 mM salicylic acid, with a titer reduction of 1.47 ⋅ 104 CCID50/ml. The time required for complete inactivation of HSV-1 particles was reduced to 15 min when the virus was exposed to 0.061 mM CHG and 0.0125 mM salicylic acid. Additionally, the presence of salicylic acid protected the CHG activity against interfering substances.

CONCLUSION

Our supplemented CHG formulation showed immediate antiviral effectiveness, which is important for management of the infections. CHG can be combined with salicylic acid to exhibit synergistic antiviral activity at lower concentrations and reduce the time required for inactivation. Furthermore, in the presence of interfering substances, the combination has higher antiviral activity than CHG alone.

Sweet Orange Juice Processing By-Product Extracts: A Caries Management Alternative to Chlorhexidine

Dental caries is one of the most prevalent chronic diseases globally in both children and adults. This study investigated the potential of industrial sweet orange waste extracts (ISOWE) as a substitute for chlorhexidine (CHX) in managing dental caries. First, the cytotoxicity of ISOWE (40, 80, 120 mg/mL) and CHX (0.1 and 0.2%) on buccal epithelial cells was determined. ISOWE exhibited no overall toxicity, whereas CHX strongly affected cell viability. The combination of ISOWE and CHX significantly enhanced cell proliferation compared to CHX alone. Next, the antimicrobial efficacy of ISOWE, CHX, and their combination was assessed against a 7-day complex biofilm model inoculated with oral samples from human volunteers. CHX exhibited indiscriminate antimicrobial action, affecting both pathogenic and health-associated oral microorganisms. ISOWE demonstrated lower antimicrobial efficacy than CHX but showed enhanced efficacy against pathogenic species while preserving the oral microbiome's balance. When applied to a cariogenic biofilm, the combined treatment of ISOWE with 0.1% CHX showed similar efficacy to 0.2% CHX treatment alone. Overall, the findings suggest that ISOWE is a promising natural anti-cariogenic agent with lower toxicity and enhanced selectivity for pathogenic species compared to CHX.

Cytotoxic effects of different mouthwash solutions on primary human articular chondrocytes and normal human articular cartilage - an in vitro study

OBJECTIVES

To compare the cytotoxicity of octenidine dihydrochloride and chlorhexidine gluconate at different concentrations on primary human articular chondrocytes and cartilage.

MATERIALS AND METHODS

Primary cultures of human normal adult articular chondrocytes were exposed to octenidine dihydrochloride (0.001562%, 0.003125%, 0.00625%, 0.0125%, 0.025%, 0.05%, and 0.1%), chlorhexidine gluconate (0.003125%, 0.00625%, 0.0125%, 0.025%, 0.05%, 0.1%, and 0.2%), and control (Dulbecco's modified Eagle medium or phosphate-buffered saline) for 30 s. Normal human articular cartilage explants were exposed to octenidine dihydrochloride (0.1% versus control) and chlorhexidine gluconate (0.1% versus control) for 30 s. The viability of human articular chondrocytes was measured by Trypan blue staining, Cell Proliferation Reagent WST-1, and Live/Dead staining. The proliferation of human chondrocytes was measured using the Cell Proliferation Reagent WST-1. The viability of human articular cartilage explants was measured by using Live/Dead staining.

RESULTS

Octenidine dihydrochloride and chlorhexidine gluconate exposure decreased cell viability and proliferation in a dose-dependent manner in primary human articular chondrocytes. Octenidine dihydrochloride and chlorhexidine gluconate exposure decreased cell viability in human articular cartilage explant cultures.

CONCLUSION

The degree of toxicity varied between octenidine dihydrochloride and chlorhexidine gluconate, with chlorhexidine gluconate being less toxic than octenidine dihydrochloride at the same concentration. Additionally, both octenidine dihydrochloride and chlorhexidine gluconate evaluation had cytotoxic effects on human articular cartilage. Therefore, dosing for the antimicrobial mouthwash ingredients administration would ideally be determined to remain below IC50.

CLINICAL RELEVANCE

These data support the in vitro safety of antimicrobial mouthwashes on primary adult human articular chondrocytes.

Antibacterial Activity of Dissolved Silver Fractions Released from Silver-Coated Titanium Dental Implant Abutments: A Study on Streptococcus mutans Biofilm Formation

(1) Background: The aim of this research was to investigate the antibacterial activity of dissolved silver from silver-coated titanium implants against Streptococcus mutans. (2) Methodology: Silver-coated titanium implant discs were immersed in 1.8 mL of brain heart infusion broth (BHIB) and incubated for 24 h in order to release the silver ions into the broth. The coating quality was confirmed via EDS, and the dissolved silver was measured via inductively coupled plasma mass spectrometry (ICP-MS). The experimental design used unconditioned broth (control) and broth conditioned with silver released from silver-coated titanium implants (n = 6). Regarding the antibacterial activity, isolated Streptococcus mutans was used. A turbidity test and lactate production test were performed to determine the effect of dissolved silver on bacterial growth in a suspension and biofilm formation. (3) Result: The results showed that the coating was successfully applied on the substrate. There was around 0.3 mg/L of silver released into the BHIB, and the turbidity of the control group was significantly higher than the treatment, with measured absorbance values of 1.4 and 0.8, respectively, indicating that the dissolved silver ions from the silver-coated titanium discs exhibited some degree of antibacterial activity by preventing the growth of Streptococcus mutans. However, the results of the antibiofilm activity test did not show any significant difference between the groups. (4) Conclusion: The dissolved silver from silver-coated titanium implants has an antibacterial activity but not a significant antimicrobial activity, indicating that the dissolved silver from silver-coated titanium abutments can significantly reduce the incidence of peri-implant mucositis.

Prevention of surgical site infection: a ten-step approach

Surgical site infection (SSI) is a common cause of morbidity and mortality in patients undergoing surgery. Similarly, periprosthetic joint infection (PJI), is a major cause of failure after total joint arthroplasty (TJA). As the annual volume of TJA procedures is projected to rise, so will the rate of subsequent SSI and PJI. Currently, prevention has been identified as the single most important strategy for combating SSI/PJI. Hence, the present article will serve as a summary of an evidence-based ten-step approach for SSI/PJI prevention that may help orthopedic surgeons with their infection prevention strategies.

Lippia origanoides derivatives in vitro evaluation on polymicrobial biofilms: Streptococcus mutans, Lactobacillus rhamnosus and Candida albicans

OBJECTIVE

This work evaluated the Lippia origanoides derivatives in vitro effect on polymicrobial biofilms of Streptococcus mutans, Lactobacillus rhamnosus and Candida albicans. Additionally, the cytotoxic effect of the oils on human skin keratinocytes (HaCaT) and fibroblasts of the periodontal ligament (FLP) cell lines was evaluated.

DESIGN

The minimum inhibitory concentration, the inhibitory activity on monomicrobial (S. mutans) and polymicrobial biofilm (S. mutans, L. rhamnosus and C. albicans) of L. origanoides four essential oils and terpenes (thymol and carvacrol) were evaluated. The cytotoxic effect of each one of the compounds was measured, and all the tests were compared against chlorhexidine.

RESULTS

All the evaluated compounds reached an inhibition percentage of S. mutans monomicrobial biofilms formation of 100 % at 600 µg/mL (p < 0.0001). The highest concentration (2 MIC) eradicated 100 % of S. mutans-preformed biofilms after 5 min L. origanoides carvacrol + thymol and thymol chemotypes showed marked reductions in topography, the number of microbial cells and extracellular matrix on polymicrobial biofilm. The cytotoxic effect of the compounds was very similar to chlorhexidine.

CONCLUSIONS

L. origanoides essential oils have an inhibitory effect on mono and polymicrobial biofilms. The oils present a similar cytotoxic effect to chlorhexidine on HaCaT and FLP cell lines. However, including these compounds in formulations for clinical use is an exciting proposal yet to be investigated.

Natural Bioactive Epigallocatechin-Gallate Promote Bond Strength and Differentiation of Odontoblast-like Cells

The (-)-Epigallocatechin-gallate (EGCG) metabolite is a natural polyphenol derived from green tea and is associated with antioxidant, biocompatible, and anti-inflammatory effects.

OBJECTIVE

To evaluate the effects of EGCG to promote the odontoblast-like cells differentiated from human dental pulp stem cells (hDPSCs); the antimicrobial effects on Escherichia coli, Streptococcus mutans, and Staphylococcus aureus; and improve the adhesion on enamel and dentin by shear bond strength (SBS) and the adhesive remnant index (ARI).

MATERIAL AND METHODS

hDSPCs were isolated from pulp tissue and immunologically characterized. EEGC dose-response viability was calculated by MTT assay. Odontoblast-like cells were differentiated from hDPSCs and tested for mineral deposition activity by alizarin red, Von Kossa, and collagen/vimentin staining. Antimicrobial assays were performed in the microdilution test. Demineralization of enamel and dentin in teeth was performed, and the adhesion was conducted by incorporating EGCG in an adhesive system and testing with SBS-ARI. The data were analyzed with normalized Shapiro-Wilks test and ANOVA post hoc Tukey test.

RESULTS

The hDPSCs were positive to CD105, CD90, and vimentin and negative to CD34. EGCG (3.12 µg/mL) accelerated the differentiation of odontoblast-like cells. Streptococcus mutans exhibited the highest susceptibility < Staphylococcus aureus < Escherichia coli. EGCG increased (p < 0.05) the dentin adhesion, and cohesive failure was the most frequent.

CONCLUSION

(-)-Epigallocatechin-gallate is nontoxic, promotes differentiation into odontoblast-like cells, possesses an antibacterial effect, and increases dentin adhesion.

2022 American Association of Hip and Knee Surgeons Symposium: Periprosthetic Joint Infection

Periprosthetic joint infection (PJI) is the leading cause of failure in patients undergoing total joint arthroplasty. This article is a brief summary of a symposium on PJI that was presented at the annual AAHKS meeting. It will provide an overview of current technqiues in the prevention, diagnosis, and management of PJI. It will also highlight emerging technologies in this setting.

Exploring the potential of eco-friendly silver nanoparticles to inhibit azole-resistant clinical isolates of Candida spp

The antimicrobial activity and biological efficiency of silver nanoparticles (AgNps) have been widely described and can be modeled through stabilizing and reducing agents, especially if they exhibit biocidal properties, which can enhance bioactivity against pathogens. The selective action of AgNps remains a major concern. In this regard, the use of plant extracts for the green synthesis of nanoparticles offers advantages because it improves the toxicity of Nps for microorganisms and is harmless to normal cells. However, biological evaluations of the activity of AgNps synthesized using different reducing agents are determined independently, and comparisons are frequently overlooked. Thus, we investigated and compared the antifungal and cytotoxic effects of two ecological AgNps synthesized from Moringa oleifera aqueous leaf extract (AgNp-M) and glucose (AgNp-G) against azole-resistant clinical isolates of Candida spp. and nontumor mammalian cells. Synthesized AgNps exhibited an antifungal effect on planktonic cells of drug-resistant C. albicans and C. tropicalis (MIC 0.21-52.6 µg/mL). The toxicity was influenced by size. However, the use of M. oleifera extracts allows us to obtain AgNps that are highly selective and nongenotoxic to Vero cells due to modifications of the shape and surface. Therefore, these results suggest that AgNp-M has antimicrobial potential and deserves further investigation for biomedical applications.

Advanced materials and technologies for oral diseases

Oral disease, as a class of diseases with very high morbidity, brings great physical and mental damage to people worldwide. The increasing burden and strain on individuals and society make oral diseases an urgent global health problem. Since the treatment of almost all oral diseases relies on materials, the rapid development of advanced materials and technologies has also promoted innovations in the treatment methods and strategies of oral diseases. In this review, we systematically summarized the application strategies in advanced materials and technologies for oral diseases according to the etiology of the diseases and the comparison of new and old materials. Finally, the challenges and directions of future development for advanced materials and technologies in the treatment of oral diseases were refined. This review will guide the fundamental research and clinical translation of oral diseases for practitioners of oral medicine.

Microbiological Properties and Cytotoxicity of PNVCL Hydrogels Containing Flavonoids as Intracanal Medication for Endodontic Therapy

This study aimed to evaluate the cytotoxicity and microbiological properties of poly (N-vinylcaprolactam)-PNVCL hydrogels containing flavonoids as intracanal medication for endodontic therapy. Antimicrobial activity of ampelopsin (AMP), isoquercitrin and rutin was determined against Enterococcus faecalis, Actinomyces israelii, Lactobacillus casei, Streptococcus mutans, and Fusobacterium nucleatum by the microdilution method. After synthesis and characterization by rheology, PNVCL hydrogels were loaded with AMP and controls calcium hydroxide (CH) and chlorhexidine (CHX), and determined the compounds release profile. PNVCL+AMP, PNVCL+CH, PNVCL+CHX were evaluated on multi-species biofilms and analyzed by Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM). Cytotoxicity was determined after fibroblasts exposure to serial dilutions of AMP and PNVCL hydrogel extracts. AMP was effective against all of the bacteria tested, especially against S. mutans, A. israelli and F. nucleatum. SEM and CLSM analysis showed that PNVCL + AMP caused a significant decrease and disorganization of multi-species biofilms and reduction of intracanal viable cells, superior to the other groups. AMP affected fibroblast viability at concentrations above 0.125 mg/mL, and extracts of PNVCL+AMP showed low cytotoxicity. In conclusion, PNVCL containing AMP demonstrated cytocompatibility and potent effect against multi-species biofilms and could be potential intracanal medication for endodontic purposes.

Characterization of polymethylmethacrylate microspheres loaded with silver and doxycycline for dental materials applications

OBJECTIVES

The manufacturing of polymethylmethacrylate(PMMA) microspheres loaded with doxycycline(DOX) and/or silver sulfate(Ag₂SO₄) to be incorporated into glass ionomer cement(GIC).

METHODS

PMMA microspheres were manufactured with Ag₂SO₄(1-5%) and/or DOX(5-15%). Particle size, encapsulation efficiency and drug release were measured by light microscope, ICP, and HPLC. Microspheres were added to a dental GIC(20%w/w). Drug release and DTS were investigated. Minimum inhibitory concentration and antibacterial effects of PMMA microspheres into GIC materials were tested.

RESULTS

The median diameter of 50 µm was obtained for microspheres. DOX was encapsulated at an efficiency of 8.3% using a theoretical loading of 15%DOX + 5%Ag₂SO₄. The Ag₂SO₄ encapsulation efficiency was 0.63% using a theoretical loading of 5%AgSO₄. All groups showed burst release within the first day and continued released up to 15 days, with 60-83% of DOX and approximately 30% of silver. For GIC, approximately 15% of DOX and 0.18% of silver were released in a 7-day period. Microbiological results showed an antimicrobial effect against S. mutans when the lead formulation of microspheres was added. The DTS was reduced by the inclusion of microspheres.

SIGNIFICANCE

PMMA microspheres containing DOX and Ag₂SO₄ offer a sustained antimicrobial activity for dental applications and promising potential for the biomedical field.

Influence of chlorhexidine digluconate on biocompatibility of cements: Morphological and immunohistochemistry analysis

In this study, the in vivo biocompatibility was evaluated by using conventional ionomer cements modified with Chlorhexidine (CHX) in different time intervals. In total, 105 male Wistar rats were randomized into seven groups: control, groups M, M10, M18 and groups RL, RL10, RL18 (M-Meron and RL-RivaLuting, and added CHX-10% and CHX-18%, respectively). Histological analyses of inflammatory infiltrate and collagen fibers, and immunohistochemistry of CD68+ for macrophages (MOs) and multinucleated giant cells (MGCs) were performed. Data were analyzed using the Kruskal-Wallis and Dunn (p < .05) tests. Intense inflammatory infiltrate was demonstrated in Group Riva CHX-18% within 7 and 15 days (p < .05), without differences after 30 days. For collagenization, healing of the groups was compatible with that of control in 15 and 30 days (p > .05). Immunomarking of CD68+ was more significant in the groups with higher concentration of CHX. There was significant difference in quantity of MGCs in groups with 18% CHX, Meron (p = .001) in 7 days, and in Riva at 30 days (p = .001). Significant difference was also found in quantities of MOs in Groups Meron and Riva in 7 days (p = .001), and only in Riva at 15 and 30 days (p = .001). The cements with addition of CHX demonstrated biocompatibility with tissues. Riva CHX-18% had the most effect on cells of the inflammatory process but showed satisfactory tissue repair.

Effect of dental antiseptic agents on the viability of human periodontal ligament cells

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Cell viability is key for tissue regeneration.

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Dental antiseptics were cytotoxic in periodontal ligament cells.

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Real-time impedimetry proved to be a non-invasive method to monitor cell viability.

Objectives

We aimed to study whether or not various dental antiseptic agents affect the viability and proliferation of human periodontal ligament cells (PDLCs).

Materials and methods

Human PDLCs were isolated from a total of 10 surgically extracted impacted third molars and were.

cultured in-vitro. The cells were exposed to commonly used dental antiseptics, including chlorhexidine, cetylpyridinium chloride, triclosan, povidone-iodine and sodium bicarbonate for ultra-short-term (10, 20, 30 sec), short-term (10, 20, 30 min) and long-term (24, 48 h) at various concentrations. Cell morphology was observed with light microscopy. Cell viability was studied with impedimetric real-time xCELLigence and resazurin-based alamarBlue® assays. We used one-way ANOVA with Tukey’s and Bonferroni test (p < 0.05) for statistical analysis.

Results

Both alamarBlue® and xCELLigence analysis results were in agreement that ultra-short-term contact with cetylpyridinium chloride ≥ 0.01 mg/ml, chlorhexidine ≥ 1 mg/ml, triclosan ≥ 1 mg/ml and povidone-iodine ≥ 1 mg/ml as well as long-term exposure to cetylpyridinium chloride ≥ 0.001 mg/ml, chlorhexidine ≥ 0.01 mg/ml, triclosan ≥ 1 mg/ml, povidone-iodine ≥ 1 mg/ml and sodium bicarbonate ≥ 10 mg/ml was able to reduce the viability of human PDLCs significantly. According to the half-maximal inhibitory concentration (IC50) the rank of cytotoxicity was cetylpyridinium chloride > chlorhexidine > triclosan > povidone-iodine > sodium bicarbonate.

Conclusions

Our findings suggest that the tested antiseptic agents were cytotoxic to human PDLCs at lower than practically applied concentrations in dental interventions.

Cytotoxicities and wound healing effects of contact lens multipurpose solution on human corneal epithelial cell

CLINICAL RELEVANCE

Contact lens multipurpose solutions (MPSs) contain several components that have the potential to cause corneal epithelial cell toxicity. Evaluating the components and the toxic effect of MPS should be considered for effective eye care.

BACKGROUND

The cytotoxic and wound healing effects of five commercially available MPSs on human corneal epithelial cells (HCECs) are is investigated.

METHODS

The following commercially available MPSs were used: Queen's PLURISOL®, Frenz®, Boston SIMPLUS®, DL+PLUS EYE® (DL), and NEW YORK DEFINE® (NY). The proliferation of HCECs exposed to each MPS for 1, 6, and 24 h and the cytotoxicity of these solutions were analyzed using methyl thiazolyl tetrazolium-based colorimetric and lactate dehydrogenase leakage assays, respectively. The cellular morphology was evaluated by inverted phase-contrast and electron microscopy. A scratch-wound assay was performed to measure wound widths 24 h after confluent HCEC monolayers were scratch-wounded.

RESULTS

The tested MPS had a time-dependent inhibitory effect on HCEC proliferation and cytotoxicity, significantly at 24 h after exposure (p< 0.05 in all MPSs). HCECs exposed to MPS detached from the bottom of the culture dishes, showed degenerative changes such as loss of microvilli, cytoplasmic vacuole formation and nuclear condensation, and decreased wound healing, compared to the controls (p< 0.001 in Boston, DL and NY). Among the tested MPS, DL and NY were more cytotoxic and showed less wound healing.

CONCLUSION

MPS has a toxic effect on HCECs, which is dependent on the concentration of the disinfecting component. Since the components that constitute the MPS are absorbed and retained in the lens, cautious scrutiny of the concentration and attention to lens cleaning are warranted to mitigate the related cytotoxicity.

A mussel glue-inspired monomer-etchant cocktail for improving dentine bonding

OBJECTIVES

The humid oral environment adversely affects the interaction between a functionalised primer and dentine collagen after acid-etching. Robust adhesion of marine mussels to their wet substrates instigates the quest for a strategy that improves the longevity of resin-dentine bonds. In the present study, an etching strategy based on the incorporation of biomimetic dopamine methacrylamide (DMA) as a functionalised primer into phosphoric acid etchant was developed. The mechanism and effect of this DMA-containing acid-etching strategy on bond durability were examined.

METHODS

Etchants with different concentrations of DMA (1, 3 or 5 mM) were formulated and tested for their demineralisation efficacy. The interaction between DMA and dentine collagen, the effect of DMA on collagen stability and the collagenase inhibition capacity of the DMA-containing etchants were evaluated. The effectiveness of this new etching strategy on resin-dentine bond durability was investigated.

RESULTS

All etchants were capable of demineralising dentine and exposing the collagen matrix. The latter strongly integrated with DMA via covalent bond, hydrogen bond and Van der Waals' forces. These interactions significantly improve collagen stability and inhibited collagenase activity. Application of the etchant containing 5 mM DMA achieved the most durable bonding interface.

CONCLUSION

Dopamine methacrylamide interacts with dentine collagen in a humid environment and improves collagen stability. The monomer effectively inactivates collagenase activity. Acid-etching with 5 mM DMA-containing phosphoric acid has the potential to prolong the longevity of bonded dental restorations without compromising clinical operation time.

CLINICAL SIGNIFICANCE

The use of 5 mM dopamine methacrylamide-containing phosphoric acid for etching dentine does not require an additional clinical step and has potential to improve the adhesive performance of bonded dental restorations.

Enhanced antibacterial effect against Enterococcus faecalis by silver ions plus Triton X-100 with low concentrations and cytotoxicity

Enterococcus faecalis (E. faecalis) is commonly considered to be one of chief culprits of secondary and persistent root canal infections. As antibiotic resistance has become a global issue, in order to reduce the use of antibiotics, metal ions have recently been widely used as an alternative. Silver ions (Ag⁺) have been proved to be a strong bactericide but with high cytotoxicity and discoloration property. Triton X-100 (TX-100) and Ag⁺ were co-used for the first time as a clinical intracanal medication to obtain both enhanced antibacterial effect and low cytotoxicity. The synergistic antibacterial effect of TX-100 + Ag⁺ was tested on both planktonic and biofilm-resident E. faecalis on dentine. And the cytotoxicity was tested on MC3T3-E1 cells. Results confirmed the antibacterial activity against both planktonic and biofilm-resident E. faecalis was dramatically improved after TX-100 incorporation. TX-100 and Ag⁺ mixture demonstrated a similar inhibitory effect as the 2% chlorhexidine (CHX), while the cytotoxicity was much lower than 2% CHX (p < 0.05). In conclusion, TX-100 + Ag⁺ mixture might be developed into a new effective intracanal medication as the 2% CHX.

Strategies toward development of antimicrobial biomaterials for dental healthcare applications

Several approaches for elimination of oral pathogens are being explored at the present time since oral diseases remain prevalent affecting approximately 3.5 billion people worldwide. Need for antimicrobial biomaterials in dental healthcare include but is not restricted to designing resin composites and adhesives for prevention of dental caries. Constant efforts are also being made to develop antimicrobial strategies for clearance of endodontic space prior root canal treatment and for treatment of periimplantitis and periodontitis. This article discusses various conventional and nanotechnology-based strategies to achieve antimicrobial efficacy in dental biomaterials. Recent developments in the design and synthesis of antimicrobial peptides and antifouling zwitterionic polymers to effectively lessen the risks of antimicrobial drug resistance are also outlined in this review. Further, the role of contemporary strategies such as use of smart biomaterials, ionic solvent-based biomaterials and quorum quenchers incorporated biomaterials in the elimination of dental pathogens are described in detail. Lastly, we mentioned the approach of using polymers to print custom-made three-dimensional antibacterial dental products via additive manufacturing technologies. This review provides a critical perspective on the chemical, biomimetic, and engineering strategies intended for developing antimicrobial biomaterials that have the potential to substantially improve the dental health.

Interaction of epigallocatechin-gallate and chlorhexidine with Streptococcus mutans stimulated odontoblast-like cells: Cytotoxicity, Interleukin-1β and co-species proteomic analyses

OBJECTIVES

The dentin therapeutic agent chlorhexidine has inflammatory and cytotoxic characteristics urging investigation of alternatives like the natural compound epigallocatechin-gallate. The aim is to verify the effect of epigallocatechin-gallate and chlorhexidine on viability, interleukin-1β (IL-1β) and differential protein expression of MDPC-23 odontoblast-like cells stimulated by Streptococcus mutans.

DESIGN

Cells were stimulated with heat-killed S. mutans at multiplicity of infection (MOI) of 100-1000 and subsequently treated with 100-1 µM of epigallocatechin-gallate. Cells with no treatment or chlorhexidine were controls. Combined stimulated/treated cells were tested for cytotoxicity (Alamar-Blue, N = 3, n = 3), total protein (N = 3, n = 3), IL-1β (ELISA, N = 3, n = 3), and differential protein expression by liquid chromatography-tandem mass spectrometry (LC-MS/MS, n = 2).

RESULTS

Cells stimulated at MOI 100/1000 and treated with 10 µM epigallocatechin-gallate and chlorhexidine did not present cytotoxicity. IL-1β significantly increased in both un-stimulated and stimulated chlorhexidine 10 µM groups when compared to un-treated control (p < 0.05). MOI 100 chlorhexidine 10 µM group significantly increased IL-1β compared to un-stimulated chlorhexidine 10 µM and epigallocatechin-gallate 10 µM groups, as well as to MOI 100 epigallocatechin-gallate 10 µM group (p < 0.05). LC-MS/MS revealed S. mutans and mammalian proteins, with tooth-specific proteins exhibiting different abundance levels, depending on the tested condition.

CONCLUSIONS

Odontoblast-like cells stimulated with S. mutans at different MOI combined with epigallocatechin-gallate treatment did not cause cytotoxicity. S. mutans stimulation combined with chlorhexidine 100 µM treatment decreased cell viability, while treatment with chlorhexidine 10 µM concentration significantly increased IL-1β. S. mutans stimulation and treatment of cells resulted in varied protein expression.

Mesoporous Calcium-Silicate Nanoparticles Loaded with Low-Dose Triton-100+Ag+ to Achieve Both Enhanced Antibacterial Properties and Low Cytotoxicity for Dentin Disinfection of Human Teeth

Mesoporous calcium-silicate nanoparticles (MCSNs) are excellent biomaterials for controlled drug delivery and mineralization induction. In this study, MCSNs were loaded with low-dose silver ion (Ag⁺) and Triton X-100 (TX-100) as the M-AgTX to achieve both enhanced antibacterial properties and low cytotoxicity for dentin disinfection. The physicochemical property, biocompatibility, infiltration ability into dentinal tubules, anti-bacterial ability against both planktonic Enterococcusfaecalis (E. faecalis) and its biofilm on dentin, effects on dentin microhardness and in vitro mineralization property were systematically investigated. Results confirmed that the MCSNs and M-AgTX nanoparticles showed typical morphology of mesoporous materials and exhibited sustained release of chemicals with an alkaline pH value over time. M-AgTX also exhibited excellent biocompatibility on MC3T3-E1 cells and could eliminate 100% planktonic E. faecalis after 48-h treatment. On dentin slices, it could enter dentinal tubules by ultrasonic activation and inhibit the growth of E. faecalis on dentin. M-AgTX could completely inactive 28-day E. faecalis biofilm. TEM confirmed the destruction of cell membrane integrity and Ag⁺ infiltration into bacteria by M-AgTX. Besides, dentin slices medicated with M-AgTX nanoparticles displayed an increased microhardness. After being immersed in SBF for 7 days, apatite crystals could be observed on the surface of the material tablets. M-AgTX could be developed into a new multifunctional intra-canal medication or bone defect filling material for infected bone defects due to its sustained release profile, low cytotoxicity, infiltration ability, enhanced anti-bacterial and mineralization features.

Evaluation of Inhibitory Effect of Self-Etch Adhesives Incorporated with Proanthocyanidin on Cysteine Cathepsins Present in Dentin Hybrid Layer Using Gelatin Zymography: An In vitro Study

Aim:

The aim of the study is to evaluate the inhibitory effect of single-bottle and two-bottle self-etch adhesive system after surface pretreatment with 6.5% proanthocyanidin (PA) on cysteine cathepsins (CCs) present in dentin hybrid layer using gelatin zymography.

Materials and Methods:

Thirty-five samples of dentin measuring 3 mm × 3 mm were obtained from 35 caries-free human third molars which were divided into seven groups. The bonded specimens were cut vertically into 1 mm thick adhesive/dentin interfaces with microtome and were pulverized into powder and subjected to zymography analysis for enzymatic activity.

Results:

Group VI and VII which were positive control groups had shown thicker clear bands of 50 kDa. Group IV and V which had the administration of chlorhexidine showed thicker clear bands of 50 kDa which indicated slight activity of CCs. Group II in which PA used along with single-bottle system also showed thicker clear band of 59 kDa. CCs could be active due to strong acidic nature of monomer in this group. Group III in which PA used along with two bottle system had no band formation where there is crosslinking of catalytic and allosteric domains of enzymes by PA.

Conclusion:

Under the limitations of this study, PA proved as a non-specific natural inhibitor of CCs. Two-bottle system showed inhibition of CCs and single bottle system failed to inhibit their activity. Future research have to be done on the bond strength and durability of self-etch adhesives after using PA and its effect on long term survival of the restorations.

Analysis of Chlorhexidine Modified Cement in Orthodontic Patients: A Double-Blinded, Randomized, Controlled Trial

OBJECTIVES

The aim of this study was to evaluate the microbiological and mechanical properties of glass ionomer cement (GIC) modified by chlorhexidine (CLX) for the purpose of cementing bands to the teeth of orthodontic patients.

MATERIALS AND METHODS

Ten patients, between the ages of 19 and 33 years, in the initial stage of orthodontic treatment, were randomly designated to two groups using the split-mouth design (n = 10). One group (GICEX) had bands cemented with GIC modified by CLX and a Control group (GIC), evaluated at time intervals before (T0), 3 months (T3), and 6 months (T6) after cementation. Total microbiological counts were performed, and color stability of tooth enamel, salivary pH, and the adhesive remnant index (ARI) were evaluated.

STATISTICAL ANALYSIS

The Friedman and Dunn's tests, Mann-Whitney, one-way analysis of variance, and Tukey, and paired and non-paired t-tests (p< 0.05) were used.

RESULTS

In T3, there was evidence of significant reduction in the quantity of colony forming unit (CFU) in GICEX group in comparison with the Control (p = 0.041). In T6, the quantity of CFU was similar to the quantity in T3 and significantly different to control (p = 0.045); Control group demonstrated a similar quantity of CFU between the experimental time intervals (p = 0.066). Salivary pH demonstrated significant difference only between the time intervals T0 and T6 (p = 0.022). The tooth enamel color (p = 0.366) and ARI (p = 0.343) values demonstrated no significant changes.

CONCLUSION

The incorporation of CLX into GIC demonstrated effective antibacterial action, allowed a good bond of the cement to the enamel, a high rate of survival of the bands, did not change the color of the tooth enamel, and maintained the salivary pH at physiological levels.

Integration of Dental Implants in Conjunction with EDTA-Conditioned Dentin Grafts: An Experimental Study

This study was undertaken to investigate the integration of titanium micro-implants installed in conjunction with previously dentin-grafted areas and to study the morphological appearance, mineral content, and healing pattern of xenogenic EDTA-conditioned dentin blocks and granules grafted to cavities in the tibial bone of rabbits. Demineralized and non-demineralized dentin blocks and granules from human premolars were implanted into cavities prepared on the lateral aspects of the tibias of rabbits. After a healing period of six months, micro-implants were installed at each surgical site. Histological examinations were carried out after 24 weeks. Characterization of the EDTA-conditioned dentin blocks was performed by means of light microscopy, dental X-rays, scanning electron microscopy, and energy dispersive X-ray analysis (EDX). No implants were found to be integrated in direct contact with the dentin particles or blocks. On the EDTA-conditioned dentin surface, the organic marker elements C and N dominated, as revealed by EDX. The hydroxyapatite constituents Ca and P were almost absent on the dentin surface. No statistically significant difference was observed between the EDTA-conditioned and non-demineralized dentin, as revealed by BIC and BA. The bone-inductive capacity of the dentin material seemed limited, although demineralization by means of EDTA indicated higher BIC and BA values in conjunction with the installed implants in the area. A 12 h EDTA treatment did not fully decalcify the grafts, as revealed by X-ray analysis.

A novel antimicrobial-containing nanocellulose scaffold for regenerative endodontics

Objectives

The aim of this study was to evaluate bacterial nanocellulose (BNC) membranes incorporated with antimicrobial agents regarding cytotoxicity in fibroblasts of the periodontal ligament (PDLF), antimicrobial activity, and inhibition of multispecies biofilm formation.

Materials and Methods

The tested BNC membranes were BNC + 1% clindamycin (BNC/CLI); BNC + 0.12% chlorhexidine (BNC/CHX); BNC + nitric oxide (BNC/NO); and conventional BNC (BNC; control). After PDLF culture, the BNC membranes were positioned in the wells and maintained for 24 hours. Cell viability was then evaluated using the MTS calorimetric test. Antimicrobial activity against Enterococcus faecalis, Actinomyces naeslundii, and Streptococcus sanguinis (S. sanguinis) was evaluated using the agar diffusion test. To assess the antibiofilm activity, BNC membranes were exposed for 24 hours to the mixed culture. After sonicating the BNC membranes to remove the remaining biofilm and plating the suspension on agar, the number of colony-forming units (CFU)/mL was determined. Data were analyzed by 1-way analysis of variance and the Tukey, Kruskal-Wallis, and Dunn tests (α = 5%).

Results

PDLF metabolic activity after contact with BNC/CHX, BNC/CLI, and BNC/NO was 35%, 61% and 97%, respectively, compared to BNC. BNC/NO showed biocompatibility similar to that of BNC (p = 0.78). BNC/CLI showed the largest inhibition halos, and was superior to the other BNC membranes against S. sanguinis (p < 0.05). The experimental BNC membranes inhibited biofilm formation, with about a 3-fold log CFU reduction compared to BNC (p < 0.05).

Conclusions

BNC/NO showed excellent biocompatibility and inhibited multispecies biofilm formation, similarly to BNC/CLI and BNC/CHX.

Identification and Characterization of New Bacteriophages to Control Multidrug-Resistant Pseudomonas aeruginosa Biofilm on Endotracheal Tubes

Studies involving antimicrobial-coated endotracheal tubes are scarce, and new approaches to control multidrug-resistant Pseudomonas aeruginosa biofilm on these devices should be investigated. In this study, five new P. aeruginosa bacteriophages from domestic sewage were isolated. All of them belong to the order Caudovirales, Myoviridae family. They are pH and heat stable and produce 27 to 46 particles after a latent period of 30 min at 37°C. Their dsDNA genome (ranging from ∼62 to ∼65 kb) encodes 65 to 89 different putative proteins. They exhibit a broad lytic spectrum and infect 69.7% of the P. aeruginosa strains tested. All the bacteriophages were able to reduce the growth of P. aeruginosa strains in planktonic form. The bacteriophages were also able to reduce the biofilm viability rates and the metabolic activity of P. aeruginosa strains in a model of biofilms associated with endotracheal tubes. In addition, scanning electron microscopy micrographs showed disrupted biofilms and cell debris after treatment of bacteriophages, revealing remarkable biofilm reduction. The lytic activity on multidrug-resistant P. aeruginosa biofilm indicates that the isolated bacteriophages might be considered as good candidates for therapeutic studies and for the application of bacteriophage-encoded products.

Antimicrobial, antibiofilm and cytotoxic effects of a colloidal nanocarrier composed by chitosan-coated iron oxide nanoparticles loaded with chlorhexidine

OBJECTIVES

This study evaluated the antimicrobial and antibiofilm effects of a colloidal nanocarrier for chlorhexidine (CHX) on Candida glabrata and Enterococcus faecalis, as well as tested its cytotoxic effect on murine fibroblasts.

METHODS

Iron oxide nanoparticles (IONPs) were coated with chitosan (CS) and loaded with CHX at 31.2, 78 and 156 μg/mL. Antimicrobial effects were assessed by determining the minimum inhibitory concentration (MIC), using the broth microdilution method, and fractional inhibitory concentration index (FICI). Preformed biofilms (48 h) were treated with different concentrations of the nanocarrier (24 h) and quantified by colony-forming units (CFUs), total biomass and metabolic activity. For cytotoxicity, the viability of L929 cells was evaluated by MTT assay after 24 and 48 h of exposure to the nanocarrier. Data were submitted to ANOVA and Fisher LSD or Tukey post-hoc tests (α = 0.05).

RESULTS

MIC and FICI results showed an indifferent interaction among the components of the nanocarrier for all strains evaluated. CHX alone and nanocarrier containing 156 μg/mL CHX did not differ from each other in reducing the number of CFUs. However, the nanocarrier containing 156 μg/mL CHX promoted the highest reductions in total biofilm biomass and metabolism, surpassing the effect of CHX alone. After 24 and 48 h of exposure, the nanocarrier reduced CHX toxicity to the L929 cell at low concentrations.

CONCLUSION

These findings suggest that the CHX nanocarrier has potential to be used in the control of oral diseases associated with C. glabrata and E. faecalis.

CLINICAL RELEVANCE

CHX has improved the antibiofilm effect and reduced the cytotoxicity (at low concentrations) when conjugated to CS-coated IONPs. This new colloidal formulation has potential as an alternative antimicrobial agent to pure CHX for the control of biofilm-related oral diseases, such as oral candidiasis and endodontic infections.

Effects of resveratrol/ethanol pretreatment on dentin bonding durability

To determine the effects of resveratrol/ethanol solution on the durability of resin-dentin bonding interfaces. Sixty-four non-caries third molars were randomly divided into four groups (n = 16) after sectioning, and then pretreated with one of the following concentrations of resveratrol/ethanol solutions: 0 (control group), 1, 10 and 20 mg/mL, followed by a universal adhesive and resin composites. All microtensile samples were divided into three subgroups: immediate group, collagenase ageing group and thermocycled group. The microtensile bond strength (MTBS), failure modes, interfacial nanoleakage and in situ zymography were measured, whereas the inhibitory effects of pretreated dentin slices on S. mutans biofilms were determined by confocal laser scanning microscopy and MTT assay. The results indicated that bonding strength was not only influenced by pretreatment factors (P < 0.05) but also ageing factors (P < 0.05). Regardless of collagenase ageing or thermocycling, the 10 mg/mL resveratrol/ethanol pretreatment group presented significantly higher (P < 0.05) MTBS and lower (P < 0.05) expression of nanoleakage than the control group, showed better inhibitory effect of matrix metalloproteinases and S. mutans activity with acceptable cytotoxicity. Meanwhile, cohesive failure in dentin decreased gradually with increasing resveratrol concentration. Therefore, the resveratrol/ethanol solution had the potential to serve as a versatile dentin primer, which can effectively improve dentin bonding durability and prevent secondary caries.

Injectable MMP-Responsive Nanotube-Modified Gelatin Hydrogel for Dental Infection Ablation

A photocrosslinkable gelatin methacryloyl (GelMA) hydrogel has been widely examined in regenerative engineering because of its good cell-tissue affinity and degradability in the presence of matrix metalloproteinases. A halloysite aluminosilicate nanotube (HNT) is a known reservoir for the loading and sustained delivery of therapeutics. Here, we formulate injectable chlorhexidine (CHX)-loaded nanotube-modified GelMA hydrogel that is cytocompatible and biodegradable and provides sustained release of CHX for infection ablation while displaying good biocompatibility. The effects of HNTs and CHX on hydrogel degradability and mechanical properties, as well as on the kinetics of CHX release, and on the antimicrobial efficacy against oral pathogens were systematically assessed. Cytocompatibility in stem cells from human exfoliated deciduous teeth and inflammatory response in vivo using a subcutaneous rat model were determined. Our hydrogel system, that is, (CHX)-loaded nanotube-modified GelMA showed minimum localized inflammatory responses, supporting its ability for drug delivery applications. Moreover, we showed that the incorporation of CHX-loaded nanotubes reduces the mechanical properties, increases the swelling ratio, and diminishes the degradation rate of the hydrogels. Importantly, the presence of CHX-loaded nanotubes inhibits bacterial growth with minimal cell toxicity. Our findings provide a new strategy to modify GelMA hydrogel with chlorhexidine-loaded nanotubes for clinical use as an injectable drug delivery strategy for dental infection ablation.

Antimicrobial, mechanical and biocompatibility analysis of chlorhexidine digluconate-modified cements

Background

The focus of this study was to evaluate the antimicrobial, mechanical properties and biocompatibility of glass ionomer (GICs) modified by Chlorhexidine (CHX).

Material and Methods

For biocompatibility, 105 male Wistar rats were used, divided into 7 groups (n=15): Group C (Control,Polyethylene), Groups M, M10, M18, and Groups RL, RL10, RL18 (M-Meron and RL-Riva Luting: conventional, and modified with 10%, and 18% CHX, respectively). The tissues were analyzed under optical microscope for different cellular events and time intervals. Antibacterial effect and Shear Bond Strength Test (SBST) were also analyzed. Biocompatibility was analyzed by the Kruskal-Wallis and Dunn tests; SBST one-way ANOVA and Tukey test (P<0.05). For the antibacterial effect, the Kruskal-Wallis and Friedman, followed by Dunn (P<0.05) tests were used.

Results

Morphological study of the tissues showed inflammatory infiltrate with significant differences between Groups C and RL18, in the time intervals of 7(P=0.013) and 15(P=0.032) days. The antimicrobial effects of the cements was shown to be CHX concentration-dependent (P=0.001). The SBST showed no significant difference between the Groups of Meron cement (P=0.385), however, there was difference between Group RL and Groups RL10 and RL18 (P=0.001).

Conclusions

The addition of CHX did not negatively influence the SBST. Meron-CHX-10% was the most biocompatible, and Riva-CHX-18% had more influence on the inflammatory process and presented slower tissue repair.

Key words:Glass ionomer, chlorhexidine, biocompatibility, antimicrobial properties, microscope.

Cytotoxicity of universal dental adhesive systems: Assessment in vitro assays on human gingival fibroblasts

Universal adhesives are the most important innovation in restorative dentistry. They are composed of different monomers, solvents and fillers. The potential cytotoxic effect of these materials is an important scientific aspect in recent literature. The aim of this study was to determine, using different in vitro techniques, the cytotoxicity evaluation of seven universal enamel-dental adhesives on human gingival fibroblasts. For this purpose, seven universal dental enamel adhesives have been evaluated by in vitro cytotoxicity tests using direct contact tests (an unpolymerized and a polymerized method) and an indirect contact test: preparation of extracts. The polymerized method showed a cytotoxicity range from 36% (G-PremioBond, GPB) to 79% (FuturaBond M+, FB). With the unpolymerized direct methods the range was from 4% (Prime&Bond Active, PBA) to 40% (Ibond Universal, IB) for undiluted adhesives; generally passing to the major dilutions the test showed a strong inhibitory activity by all the adhesives. Whereas with the indirect method by diluting the extracts of all dental adhesives the cell viability increased. The data obtained from the work has shown a lower cytotoxic effect of Optibond Solo Plus (OB) and Adhesive Universal (AU) with more reliable results with the extracts technique. The choice of reliable in vitro cytotoxic technique could represent, in dental practice, an important aid for clinical procedures in the use of adhesive systems.

Antibacterial and Cytotoxic Activities of Pinus tropicalis and Pinus elliottii Resins and of the Diterpene Dehydroabietic Acid Against Bacteria That Cause Dental Caries

Considering the impact of dental caries on public health and the wide biological potential described for species belonging to the genus Pinus, here we investigate the antibacterial activity of the P. elliottii and P. tropicalis resins and of the diterpene dehydroabietic acid (DHA) against cariogenic bacteria. For this purpose, we have determined the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of the resins and of the diterpene. We have also investigated the biofilm inhibition ability (through MBIC50 determination), as well as the synergistic effect (through fractional inhibitory concentration index) and the cytotoxic potential (through XTT assay) of the P. elliottii and P. tropicalis resins. The resins gave promising MIC and MBC values, which ranged from 12.5 to 400 μg/mL; DHA provided MIC and MBC values ranging from 25 to 400 μg/mL. The MICB50 values ranged from 0.78 to 400 μg/mL for the resins. Neither additive nor synergistic effects emerged for the combinations of one of the resins with chlorhexidine. The cytotoxic activity was ≥312.5 and ≥156.3 μg/mL for the P. elliottii and P. tropicalis resins, respectively. The resins showed antibacterial activity against planktonic and sessile cariogenic bacteria. These data are relevant and encourage further research into these plants, which may contribute to the discovery of new substances that can inhibit the growth of cariogenic microorganisms and reduce the incidence of dental caries.

Experimental study on the use of a chlorhexidine-loaded carboxymethylcellulose gel as antibacterial coating for hernia repair meshes

PURPOSE

Biomaterials with an antimicrobial coating could avoid mesh-associated infection following hernia repair. This study assesses the use of a chlorhexidine-loaded carboxymethylcellulose gel in a model of Staphylococcus aureus mesh infection.

METHODS

A 1% carboxymethylcellulose gel containing 0.05% chlorhexidine was prepared and tested in vitro and in vivo. The in vitro tests were antibacterial activity (S. aureus; agar diffusion test) and gel cytotoxicity compared to aqueous 0.05% chlorhexidine (fibroblasts; alamarBlue). For the in vivo study, partial abdominal wall defects (5 × 2 cm) were created in New Zealand white rabbits (n = 15) and inoculated with 0.25 mL of S. aureus (10⁶ CFU/mL). Defects were repaired with a lightweight polypropylene mesh (Optilene) without coating (n = 3) or coated with a carboxymethylcellulose gel (n = 6) or chlorhexidine-loaded carboxymethylcellulose gel (n = 6). Fourteen days after surgery, bacterial adhesion to the implant (sonication, immunohistochemistry), host tissue incorporation (light microscopy) and macrophage reaction (immunohistochemistry) were examined.

RESULTS

Carboxymethylcellulose significantly reduced the toxicity of chlorhexidine (p < 0.001) without limiting its antibacterial activity. While control and gel-coated implants were intensely contaminated, the chlorhexidine-gel-coated meshes showed a bacteria-free surface, and only one specimen showed infection signs. The macrophage reaction in this last group was reduced compared to the control (p < 0.05) and gel groups.

CONCLUSIONS

When incorporated in the carboxymethylcellulose gel, chlorhexidine showed reduced toxicity yet maintained its bactericidal effect at the surgery site. Our findings suggest that this antibacterial gel-coated polypropylene meshes for hernia repair prevent bacterial adhesion to the mesh surface and have no detrimental effects on wound repair.

Short-Time Antibacterial Effects of Dimethylaminododecyl Methacrylate on Oral Multispecies Biofilm In Vitro

Quaternary ammonium compounds constitute a large group of antibacterial chemicals with a potential for inhibiting dental plaque. The aims of this study were to evaluate short-time antibacterial and regulating effects of dimethylaminododecyl methacrylate (DMADDM) on multispecies biofilm viability, reformation, and bacterial composition in vitro. DMADDM, chlorhexidine (CHX), and sodium fluoride (NaF) were chosen in the present study. Streptococcus mutans, Streptococcus sanguinis, and Streptococcus gordonii were used to form multispecies biofilm. Cytotoxicity assay was used to determine the optimal tested concentration. 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and resazurin test of biofilm were conducted to study the biomass changes and metabolic changes of controlled multispecies biofilm. Scanning electron microscopy (SEM) was used to observe biofilm images. TaqMan real-time polymerase chain reaction was performed to evaluate the proportion change in multispecies biofilm of different groups. Cytotoxicity assay showed that there existed a certain concentration application range for DMADDM, CHX, and NaF. MTT assay and resazurin test results showed that DMADDM and CHX groups decreased multispecies biofilm growth and metabolic activity (p < 0.05), no matter after 1 min or 5 min direct contact killing or after 24 h regrowth. The proportion of S. mutans decreased steadily in DMADDM and CHX groups after 1 min and 5 min direct contact killing and 24 h regrowth, compared to control groups. A novel DMADDM-containing solution was developed, achieving effective short-time antibacterial effects and regulation ability of biofilm formation.

The Effects of Various Mouthwashes on Osteoblast Precursor Cells

This study examined whether or not various mouthwashes have significant effects on the viability or morphology of mouse osteoblast-like cells. Mouse calvarial preosteoblast cells were cultured and prepared, then treated with a 0.12% chlorhexidine digluconate solution containing essential oils with or without alcohol, and a cetylpyridinium chloride solution, and sodium fluoride, respectively. Each well was treated with one of six mouthwashes for either 30 sec, 1.5 min, or 4.5 min. The viability of the treated cells was quantitatively analyzed by a Cell Counting Kit-8. The viability of osteogenic progenitor cells decreased significantly irrespectively of the types of mouthwashes. The changes of cell morphology were seen in all groups of mouthwashes; however, they were more noticeable on the chlorhexidine digluconate-treated group. A progressive increase in treatment time over 30 sec did not seem to deteriorate cellular viability. There was no significant difference in viability or morphological change between different formulations of the same brand. Although various mouthwashes without alcohol as an ingredient are available, nonalcoholic mouthwashes were not likely to be less harmful to the cells. Collectively, commercially available mouthwashes could inhibit cell viability and alter the morphology of osteoblastic precursor cells irrespectively of brands, treatment time, or alcohol content.

Downregulated microRNA-488 enhances odontoblast differentiation of human dental pulp stem cells via activation of the p38 MAPK signaling pathway

Human dental pulp stem cells (hDPSCs) are primarily derived from the pulp tissues of permanent third molar teeth. They were widely used in human bone tissue engineering. It was previously indicated that microRNA (miR) expressions are closely associated with hDPSCs development. However, the specific effect of miR-488 on hDPSCs still remains unclear. In this study, we aimed to investigate effects of miR-488 on the differentiation of hDPSCs into odontoblast cells through the p38 mitogen-activated protein kinases (MAPK) signaling pathway by binding to MAPK1. The hDPSCs were isolated and cultured in vitro. Dual-luciferase reporter gene assay was performed to test the relationship between MAPK1 (p38) and miR-488. Reverse transcription quantitative polymerase chain reaction and western blot analysis were used to detect the mRNA and protein expressions of p38 MAPK signaling pathway-related genes (MAPK1, Ras, and Mitogen-activated protein kinase kinase 3/6 [MKK3/6]), along with expressions of dentin Sialophosphoprotein (DSPP), alkaline phosphatase (ALP), and osteonectin (OCN). ALP staining and alizarin red staining were conducted to detect ALP activity and degree of mineralization. Initially, we found that MAPK1 was the target gene of miR-488. Besides, downregulation of miR-488 was observed to stimulate the p38 MAPK signaling pathway and to increase the messenger RNA and protein expressions of DSPP, ALP, and OCN. Furthermore, ALP activity and formation of a mineralized nodule in hDPSCs were enhanced upon downregulation of miR-488. The aforementioned findings provided evidence supporting that downregulation of miR-488 promotes odontoblastic differentiation of hDPSCs through the p38 MAPK signaling pathway by targeting MAPK1, paving the basis for further study about hDPSCs.

The antimicrobial and antiadhesion activities of micellar solutions of surfactin, CTAB and CPCl with terpinen-4-ol: applications to control oral pathogens

The oral pathogen Streptococcus mutans is involved in tooth decay by a process that initiates with biofilm adhesion and caries development. The presence of other microbes such as Candida albicans may worsen the demineralization process. Since both microbes are virulent to the host and will proliferate under specific host immune deficiencies and systemic diseases, it is important to study antimicrobial substances and their effects on both pathogens. There are several antiseptic agents used to reduce plaque biofilm and its outcome (dental caries and/or periodontal disease). However, some of these have undesired effects. In the current study we investigated the antimicrobial and anti-adhesion properties of micellar solutions of surfactants and the plant natural product terpinen-4-ol (TP). The results revealed an increase in antimicrobial properties of the synthetic surfactants, cetylpyridinium chloride (CPC) and cetyltrimethylammonium bromide (CTAB), when mixed with TP. In addition, although surfactin, a biosurfactant, has little antimicrobial activity, it was demonstrated that it enhanced the effect of TP both as antimicrobial and anti-adhesion compound. Surfactin and the synthetic surfactants promote the antimicrobial activity of TP against S. mutans, the causal agent of tooth decay, suggesting specificity for membrane interactions that may be facilitated by surfactants. This is the first report on the successful use of surfactin in association with TP to inhibit the growth and adhesion of microbial pathogens. Surfactin has other beneficial properties besides being biodegradable, it has antiviral and anti-mycoplasma activities in addition to adjuvant properties and encapsulating capacity at low concentration.

Demineralized Xenogenic Dentin and Autogenous Bone as Onlay Grafts to Rabbit Tibia

PURPOSE

The present study was undertaken to evaluate the healing pattern of xenogenic demineralized dentin onlay grafts in comparison with autogenous bone grafts to the rabbit tibia.

MATERIAL AND METHODS

Eight 6-month-old New Zealand male rabbits were used in the experiments. Standardized sized dentin blocks from human premolars and similar autogenous bone blocks harvested from tibia were grafted as onlay blocks on each tibia (n = 8 × 2). All animals were killed after a healing period of 12 weeks.

RESULTS

Healing was uneventful for all animals. In general, both the dentin and bone block grafts were fused to the bone, resorbed, and replaced by bone and connective tissue to a varying degree. Both types of grafts were still present after 12 weeks, on an average to approximately one third of the original sizes. Resorption cavities could be seen in the dentin with bone formation. Zones of osseous replacement resorption of the dentin could be noted. In both graft types, higher rate of bone formation was seen at the interface between graft and recipient site.

CONCLUSION

Demineralized xenogenic dentin onlay grafts showed similar resorption characteristics as autogenous bone onlay grafts, being resorbed in a similar rate during 12 weeks. New bone formation occurred mainly in terms of replacement resorption in the interface between dentin/bone graft and native bone.

Monomer conversion, dimensional stability, strength, modulus, surface apatite precipitation and wear of novel, reactive calcium phosphate and polylysine-containing dental composites

Purpose

The aim was to assess monomer conversion, dimensional stability, flexural strength / modulus, surface apatite precipitation and wear of mono / tri calcium phosphate (CaP) and polylysine (PLS)—containing dental composites. These were formulated using a new, high molecular weight, fluid monomer phase that requires no polymerisation activator.

Materials and methods

Urethane and Polypropylene Glycol Dimethacrylates were combined with low levels of an adhesion promoting monomer and a light activated initiator. This liquid was mixed with a hybrid glass containing either 10 wt% CaP and 1 wt% PLS (F1) or 20 wt% CaP and 2 wt% PLS (F2). Powder to liquid mass ratio was 5:1. Commercial controls included Gradia Direct Posterior (GD) and Filtek Z250 (FZ). Monomer conversion and polymerisation shrinkage were calculated using Fourier Transform Infrared (FTIR). Subsequent volume increases in water over 7 weeks were determined using gravimetric studies. Biaxial flexural strength (BFS) / modulus (BFM) reduction and surface apatite precipitation upon 1 and 4 weeks immersion in water versus simulated body fluid (SBF) were assessed using a mechanical testing frame and scanning electron microscope (SEM). Mass / volume loss and surface roughness (R_a) following 7 weeks water immersion and subsequent accelerated tooth-brush abrasion were examined using gravimetric studies and profilometer.

Results

F1 and F2 exhibited much higher monomer conversion (72%) than FZ (54%) and low calculated polymerization shrinkage (2.2 vol%). Final hygroscopic expansions decreased in the order; F2 (3.5 vol%) > F1 (1.8 vol%) ~ Z250 (1.6 vol%) > Gradia (1.0 vol%). BFS and BFM were unaffected by storage medium type. Average BFS / BFM upon 4 weeks immersion reduced from 144 MPa / 8 GPa to 107 MPa / 5 GPa for F1 and 105 MPa / 6 GPa to 82 MPa / 4 GPa for F2. Much of this change was observed in the first week of immersion when water sorption rate was high. Surface apatite layers were incomplete at 1 week, but around 2 and 15 micron thick for F1 and F2 respectively following 4 weeks in SBF. Mass and volume loss following wear were equal. Average results for F1 (0.5%), F2 (0.7%), and FZ (0.5%) were comparable but lower than that of GD (1%). R_a, however, decreased in the order; F1 (15 μm) > F2 (11 μm) > GD (9 μm) > FZ (5 μm).

Conclusions

High monomer conversion in combination with large monomer size and lack of amine activator should improve cytocompatibility of the new composites. High monomer molecular weight and powder content enables low polymerisation shrinkage despite high conversion. Increasing active filler provides enhanced swelling to balance shrinkage, which, in combination with greater surface apatite precipitation, may help seal gaps and reduce bacterial microleakage. High monomer conversion also ensures competitive mechanical / wear characteristics despite enhanced water sorption. Furthermore, increased active filler could help reduce surface roughness upon wear.

KR-12-a5 is a non-cytotoxic agent with potent antimicrobial effects against oral pathogens

This study evaluated the cytotoxicity and antimicrobial activity of analogs of cationic peptides against microorganisms associated with endodontic infections. L-929 fibroblasts were exposed to LL-37, KR-12-a5 and hBD-3-1C^V and chlorhexidine (CHX, control), and cell metabolism was evaluated with MTT. The minimal inhibitory concentration (MIC) and the minimal bactericidal/fungicidal concentration (MBC/MFC) of the peptides and CHX were determined against oral pathogens associated with endodontic infections. Enterococcus faecalis and Streptococcus mutans biofilms were cultivated in bovine dentin blocks, exposed to different concentrations of the most efficient antimicrobial peptide and analyzed by confocal laser scanning microscopy. CHX and peptides affected the metabolism of L-929 at concentrations > 31.25 and 500 μg ml^-1, respectively. Among the peptides, KR-12-a5 inhibited growth of both the microorganisms tested with the lowest MIC/MBC/MFC values. In addition, KR-12-a5 significantly reduced E. faecalis and S. mutans biofilms inside dentin tubules. In conclusion, KR-12-a5 is a non-cytotoxic agent with potent antimicrobial and anti-biofilm activity against oral pathogens associated with endodontic infections.