Flow Cytometry Analysis of Antibacterial Effects of Universal Dentin Bonding Agents on Streptococcus mutans

Effect of Modified Triple-Layer Application on the Bond Strength of Different Dental Adhesive Systems to Dentin

The goal of this article was to assess the effect of modified triple-layer application (MTLA) in conjunction with the active bonding technique on the bond strength of four adhesive systems to dentinal substrate. The adhesives tested were Prime&Bond Universal (PBU), OptiBond Universal (OBU), OptiBond FL (OBFL), and Clearfil SE (CSE). The adhesives were applied according to the following strategies: single active application (A) and triple adhesive layer application including Active-Passive-Passive (APP); AAP; and AAA. The micro-tensile bond strength test was evaluated following 24 h or 6 months of storage. The composite-dentin interface morphology was investigated using scanning electron microscopy. The data were statistically analyzed with a significance level of α = 0.05. At 24 h of aging, all of the factors tested were not significant (p > 0.05) for CSE. For OBFL, OBU, and PBU, statistically higher values were observed for the A technique (p < 0.05). Plus, there were no significant variances between the APP, AAP, and AAA techniques (p > 0.05) for OBFL and PBU. However, for OBU, there were no significant differences between the A and AAA techniques (p > 0.05). After 6 months of aging, the A technique showed statistically higher values when compared to the other techniques (p < 0.01), except for OBFL, where the A and AAA techniques showed promising outcomes. When comparing the bond strength values of 24 h and 6 months, only for PBU, all of the techniques used resulted in bond strength stability over time (p > 0.05). Thicker adhesive layers were observed when MTLA was applied. Only the OBFL adhesive showed the formation of resin tags in all of the modalities tested. The bonding performances of the different application techniques used were material-dependent.

Convergence of flow cytometry and bacteriology. Current and future applications: a focus on food and clinical microbiology

Since its development in the 1960s, flow cytometry (FCM) was quickly revealed a powerful tool to analyse cell populations in medical studies, yet, for many years, was almost exclusively used to analyse eukaryotic cells. Instrument and methodological limitations to distinguish genuine bacterial signals from the background, among other limitations, have hampered FCM applications in bacteriology. In recent years, thanks to the continuous development of FCM instruments and methods with a higher discriminatory capacity to detect low-size particles, FCM has emerged as an appealing technique to advance the study of microbes, with important applications in research, clinical and industrial settings. The capacity to rapidly enumerate and classify individual bacterial cells based on viability facilitates the monitoring of bacterial presence in foodstuffs or clinical samples, reducing the time needed to detect contamination or infectious processes. Besides, FCM has stood out as a valuable tool to advance the study of complex microbial communities, or microbiomes, that are very relevant in the context of human health, as well as to understand the interaction of bacterial and host cells. This review highlights current developments in, and future applications of, FCM in bacteriology, with a focus on those related to food and clinical microbiology.

Inactivation of Salmonella using ultrasound in combination with Litsea cubeba essential oil nanoemulsion and its bactericidal application on cherry tomatoes

The presence of Salmonella in nature poses a significant and unacceptable threat to the human public health domain. In this study, the antibacterial effect and mechanism of ultrasound (US) combined with Litsea cubeba essential oil nanoemulsion (LEON) on Salmonella. LEON + US treatment has a significant bactericidal effect on Salmonella. Reactive oxygen species (ROS), malondialdehyde (MDA) detection, N-phenyl-l-naphthylamine (NPN) uptake and nucleic acid release assays showed that LEON + US exacerbated cell membrane lipid peroxidation and increased the permeability of the cell membrane. The results of field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) showed that LEON + US treatment was able to alter cell morphology. It can be observed by flow cytometry (FCM) that LEON + US treatment can cause cell apoptosis. In addition, bacterial counts of cherry tomatoes treated with LEON (0.08 μL/mL) + US (345 W/cm²) for 9 min were reduced by 6.50 ± 0.20 log CFU/mL. This study demonstrates that LEON + US treatment can be an effective way to improve the safety of fruits and vegetables in the food industry.

Shear Bond Strength and Fluoride Release of a Universal Adhesive: An In-Vitro Study on Primary Teeth

This investigation aimed to assess the shear bond strength and fluoride-releasing capabilities of Clearfil Universal Bond Quick (Kuraray Noritake Dental Inc., Tokyo, Japan). Forty-four extracted primary molars were divided into two groups, and the enamel substrate was prepared for evaluating shear bond strength. Scotchbond (3M ESPE) and Clearfil UBQ were used to bond composite-to-enamel substrates in each group (n = 22). Shear bond strength was measured using a universal testing device and compared. Sixteen discs (6 mm diameter and 3 mm thickness) were fabricated from each Clearfil UBQ, Fuji IX, and Fuji II LC. Over the course of 30 days, each materials' fluoride release was examined and compared using ion analysis. Results revealed that Clearfil UBQ had statistically similar shear bond strength to Scotchbond. Between the three materials, Clearfil UBQ had the lowest fluoride release at baseline (0.11 ± 0.25) and the lowest cumulative fluoride release (0.12-0.27 ppm) over 30 days. Fuji IX had the highest fluoride release at baseline (19.38 ± 2.50) and cumulatively (40.87 ± 4.03 ppm), followed by Fuji II LC. We conclude that Clearfil UBQ and Scotchbond showed comparable bond strengths to the enamel. Fluoride release was seen in Clearfil UBQ in the initial two days of the 30-day period. The amount of fluoride release was significantly less than with glass ionomer cements.

Triclosan to Improve the Antimicrobial Performance of Universal Adhesives

To solve the proble ms of composite restoration failure caused by secondary caries, this study reports a light curable antibacterial triclosan derivative (TCS-IH), which was synthesized and added to the existing commercial universal adhesive to achieve a long-term antibacterial effect The effect of mixing different mass percentages of TCS-IH on the bond strength of dentin was also investigated.TCS-IH was synthesized by solution polymerization and characterized by nuclear magnetic resonance hydrogen spectroscopy (1H NMR) and Fourier transform infrared (FTIR) spectroscopy. Two commercial universal adhesives, Single Bond Universal and All Bond Universal, were selected and used as the control group, and universal adhesives with different mass percentages (1 wt%, 3 wt%, 5 wt% and 7 wt%) of TCS-IH were used as the experimental group. The antibacterial properties were analysed by means of colony count experiments, biofilm formation detection, plotting of growth curves, biofilm metabolic activity detection, insoluble extracellular polysaccharide measurements and observations by confocal laser scanning microscopy and scanning electron microscopy (SEM). The effect of adhesives on biofilm formation, metabolism, extracellular matrix production, distribution of live and dead bacteria, and bacterial morphology of Streptococcus mutans (S. mutans) was analysed. The mechanical properties were evaluated by the degree of conversion and microtensile bonding strength under different conditions. Its biosafety was tested. We found that the addition of TCS-IH significantly improved the antibacterial performance of the universal adhesive, with the 5 wt% and 7 wt% groups showing the best antibacterial effect and effectively inhibiting the formation of biofilm. In addition, the adhesive strength test results showed that there was no statistical difference (p < 0.05) in the microtensile bond strength measured under various factors in all experimental groups except for the 7 wt% group in the self-etch bonding mode, and all of them had good biosafety. In summary, the 5 wt% group of antibacterial monomer TCS-IH was selected as the optimum addition to the universal adhesive to ensure the antimicrobial properties of the universal adhesive and the stability and durability of the adhesive interface. This study provides a reference for the clinical application of adhesives with antimicrobial activity to improve the stability and durability of adhesive restorations.

Streptococcus mutans levels in patients who received orthodontic brackets bonded using probiotic impregnated resin composite - a randomized clinical trial

To evaluate the effect of impregnating an orthodontic resin composite with probiotic bacteria (Lactobacillus rhamnosus GG) on the levels of Streptococcus mutans (S. mutans) in patients undergoing orthodontic treatment. Thirty patients were randomly selected and allotted by block randomization to two groups: an experimental group, who received brackets bonded with probiotic impregnated resin composite and a control group, who received brackets bonded with conventional light cure resin composite. Plaque samples were collected before (ET0 and CT0) and two months (ET1 and CT1) after bonding. Levels of S. mutans were assessed using the colony count method. Two months after bonding of the brackets, the S. mutans levels had decreased with statistical significance in the experimental group (p = 0.001), but not in the control group (p = 0.137). Impregnation of resin composite with probiotic bacteria for the purpose of preventing formation of white spot lesions on enamel holds promise. Long-term evaluation would be necessary to provide confirmatory results.

L-arginine-containing mesoporous silica nanoparticles embedded in dental adhesive (Arg@MSN@DAdh) for targeting cariogenic bacteria

Dental caries is the major biofilm-mediated oral disease in the world. The main treatment to restore caries lesions consists of the use of adhesive resin composites due to their good properties. However, the progressive degradation of the adhesive in the medium term makes possible the proliferation of cariogenic bacteria allowing secondary caries to emerge. In this study, a dental adhesive incorporating a drug delivery system based on L-arginine-containing mesoporous silica nanoparticles (MSNs) was used to release this essential amino acid as a source of basicity to neutralize the harmful acidic conditions that mediate the development of dental secondary caries. The in vitro and bacterial culture experiments proved that L-arginine was released in a sustained way from MSNs and diffused out from the dental adhesive, effectively contributing to the reduction of the bacterial strains Streptococcus mutans and Lactobacillus casei. Furthermore, the mechanical and bonding properties of the dental adhesive did not change significantly after the incorporation of L-arginine-containing MSNs. These results are yielding glimmers of promise for the cost-effective prevention of secondary caries.

The Toxicity of Universal Dental Adhesives: An In Vitro Study

There is no consensus in the literature regarding the potential toxicity of universal dental adhesives (UDA). Being used in close proximity to the pulp, their biocompatibility should be an important factor in dental research. The aim of the present study was to evaluate the biocompatibility of UDA in an in vitro model. The study was performed using a monocyte/macrophage peripheral blood SC cell line (ATCC CRL-9855) on four specific UDA, namely: All-Bond Universal (Bisco); CLEARFIL Universal Bond Quick (Kuraray); G-Premio BOND (GC); Single Bond Universal (3M ESPE). The cytotoxicity of the investigated UDA was measured using the XTT colorimetric assay. The genotoxicity of the analyzed compounds was evaluated using an alkaline version of the comet assay. Furthermore, flow cytometry (FC) apoptosis detection was performed using the FITC Annexin V Apoptosis Detection Kit I. FC cell-cycle arrest assessment was performed using propidium iodide staining. The study observed significant differences in the toxicity of the UDA that were tested, as G-Premio BOND showed significant in vitro toxicity in all of the tests performed, while All-Bond Universal, CLEARFIL Universal Bond Quick and Single Bond Universal did not present any significant toxic effects toward SC cell line. The in vitro toxicity of UDA should be taken into consideration prior to in vivo and clinical studies. The flow cytometry could improve the accuracy of dental materials research and should be incorporated into the standardization criteria.

The Bond Strength and Antibacterial Activity of the Universal Dentin Bonding System: A Systematic Review and Meta-Analysis

Streptococcus mutans (S. mutans) is a group of viridans mostly located in oral flora among the wide and biodiverse biofilm. It plays a significant role not only in caries formation but also triggering intracerebral haemorrhage. The durable and stable bond interface, besides bacteria elimination, is one of the crucial factors influencing the resin composite restoration performance. This study aimed to evaluate universal adhesives (UAs) with regard to in vitro bond strength to dentin, and the inhibition of the S. mutans growth and compare them with UAs modified with antimicrobial agents through a systematic review and meta-analysis. Two reviewers performed a literature search up to April 2021 in 5 electronic databases: PubMed MedLine, Scielo, ISI Web of Science, Scopus, and EMBASE. Only in vitro studies reporting the effect of modifying UAs with antimicrobial agents on the bond strength to dentin and/or on the inhibition of the S. mutans were included. Analyses were carried out using Review Manager Software version 5.3.5 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark). The methodological quality of each in vitro study was evaluated following the parameters of a previous systematic review. A total of 1716 potentially relevant publications were recognized. After reviewing the title and abstract, 16 studies remained in the systematic review. From these, a total of 3 studies were included in the meta-analysis. Since data from the studies included in the antimicrobial outcome included zero values, they could not be meta-analysed. Including 0 values in the analysis will lead to several biases in the analysis, so these data were discarded. The antibacterial effect against S. mutans of UAs modified with antimicrobial agents was higher than the non-modified adhesive systems. Within the limitations of the present study, the bond strength of UAs to dentin could be improved by using antimicrobial agents. The UAs modified with antibacterial agents showed a decrease in the viability of S. mutans biofilm, among the adhesives tested. However, there are not enough valid data on antibacterial properties of modified UAs; therefore, more well-designed research on these materials is needed.

Antibacterial and Bonding Properties of Universal Adhesive Dental Polymers Doped with Pyrogallol

This study investigated the antibacterial activity, bond strength to dentin (SBS), and ultra-morphology of the polymer-dentin interface of experimental adhesive systems doped with pyrogallol (PY), which is a ubiquitous phenolic moiety that is present in flavonoids and polyphenols. A universal adhesive containing 4-META and 10-MDP was used in this study. PY behaves as an antioxidant and anti-cancerogenic agent and it was incorporated into the adhesive at different concentrations (0.5 and 1 wt.%). The antibacterial activity and SBS were analyzed and the results were statistically analyzed. The ultra-morphology of the polymer-dentin interface was assessed using scanning electron microscopy (SEM). At 24 h, a lower antibacterial activity was observed for the control adhesive compared to those with 0.5% and 1% PY. No difference was seen in SBS between the three groups at 24 h. After 6 months, the SBS of the 0.5% PY adhesive was significantly lower than the other tested adhesives. The specimens created with 1% PY adhesive presented a higher bond strength at six months compared with that found at 24 h. No morphological differences were found at the polymer-dentin interfaces of the tested adhesives. Pyrogallol may be incorporated into modern universal adhesive systems to preserve the polymer-dentin bonding interface and confer a certain degree of antibacterial activity.

Bibliometric Analysis of Literature Published on Antibacterial Dental Adhesive from 1996-2020

This study aimed to investigate the current state of research on antibacterial dental adhesives. The interest in this field can be drawn from an increasing number of scholarly works in this area. However, there is still a lack of quantitative measurement of this topic. The main aim of this study was to consolidate the research published on the antibacterial adhesive from 1996 to 2020 in Web of Science indexed journals. The bibliometric method, a quantitative study of investigating publishing trends and patterns, was used for this study. The result has shown that a gradual increase in research was found, whereby a substantial increase was observed from 2013. A total of 248 documents were published in 84 journals with total citations of 5107. The highly cited articles were published mainly in Q1 category journals. Most of the published articles were from the USA, China, and other developed countries; however, some developing countries contributed as well. The authorship pattern showed an interdisciplinary and collaborative approach among researchers. The thematic evaluation of keywords along with a three-factor analysis showed that 'antibacterial adhesives' and 'quaternary ammonium' have been used commonly. This bibliometric analysis can provide direction not only to researchers but also to funding organizations and policymakers.

An In Vitro Study on the Antimicrobial Properties of Essential Oil Modified Resin Composite against Oral Pathogens

Modifying the composition of dental restorative materials with antimicrobial agents might induce their antibacterial potential against cariogenic bacteria, e.g., S. mutans and L. acidophilus, as well as antifungal effect on C. albicans that are major oral pathogens. Essential oils (EOs) are widely known for antimicrobial activity and are successfully used in dental industry. The study aimed at evaluating antibacterial and antifungal activity of EOs and composite resin material (CR) modified with EO against oral pathogens. Ten EOs (i.e., anise, cinnamon, citronella, clove, geranium, lavender, limette, mint, rosemary thyme) were tested using agar diffusion method. Cinnamon and thyme EOs showed significantly highest antibacterial activity against S. mutans and L. acidophilus among all tested EOs. Anise and limette EOs showed no antibacterial activity against S. mutans. All tested EOs exhibited antifungal activity against C. albicans, whereas cinnamon EO showed significantly highest and limette EO significantly lowest activity. Next, 1, 2 or 5 µL of cinnamon EO was introduced into 2 g of CR and microbiologically tested. The modified CR showed higher antimicrobial activity in comparison to unmodified one. CR containing 2 µL of EO showed the best antimicrobial properties against S. mutans and C. albicans, while CR modified with 1 µL of EO showed the best antimicrobial properties against L. acidophilus.

Clinical Effectiveness of Bulk-Fill and Conventional Resin Composite Restorations: Systematic Review and Meta-Analysis

The objective of this systematic review and meta-analysis was to determine the clinical effectiveness of bulk-fill and conventional resin in composite restorations. A bibliographic search was carried out until May 2020, in the biomedical databases Pubmed/MEDLINE, EMBASE, Scopus, CENTRAL and Web of Science. The study selection criteria were: randomized clinical trials, in English, with no time limit, with a follow-up greater than or equal to 6 months and that reported the clinical effects (absence of fractures, absence of discoloration or marginal staining, adequate adaptation marginal, absence of post-operative sensitivity, absence of secondary caries, adequate color stability and translucency, proper surface texture, proper anatomical form, adequate tooth integrity without wear, adequate restoration integrity, proper occlusion, absence of inflammation and adequate point of contact) of restorations made with conventional and bulk resins. The risk of bias of the study was analyzed using the Cochrane Manual of Systematic Reviews of Interventions. Sixteen articles were eligible and included in the study. The results indicated that there is no difference between restorations with conventional and bulk resins for the type of restoration, type of tooth restored and restoration technique used. However, further properly designed clinical studies are required in order to reach a better conclusion.

Dental adhesive microtensile bond strength following a biofilm-based in vitro aging model

OBJECTIVE

Laboratory tests are routinely used to test bonding properties of dental adhesives. Various aging methods that simulate the oral environment are used to complement these tests for assessment of adhesive bond durability. However, most of these methods challenge hydrolytic and mechanical stability of the adhesive- enamel/dentin interface, and not the biostability of dental adhesives. To compare resin-dentin microtensile bond strength (μTBS) after a 15-day Streptococcus mutans (SM) or Streptococcus sobrinus (SS) bacterial exposure to the 6-month water storage (WS) ISO 11405 type 3 test.

METHODOLOGY

A total of 31 molars were flattened and their exposed dentin was restored with Optibond-FL adhesive system and Z-100 dental composite. Each restored molar was sectioned and trimmed into four dumbbell-shaped specimens, and randomly distributed based on the following aging conditions: A) 6 months of WS (n=31), B) 5.5 months of WS + 15 days of a SM-biofilm challenge (n=31), C) 15 days of a SM-biofilm challenge (n=31) and D) 15 days of a SS-biofilm challenge (n=31). μTBS were determined and the failure modes were classified using light microscopy.

RESULTS

Statistical analyses showed that each type of aging condition affected μTBS (p<0.0001). For Group A (49.7±15.5MPa), the mean μTBS was significantly greater than in Groups B (19.3±6.3MPa), C (19.9±5.9MPa) and D (23.6±7.9MPa). For Group D, the mean μTBS was also significantly greater than for Groups B and C, but no difference was observed between Groups B and C.

CONCLUSION

A Streptococcus mutans- or Streptococcus sobrinus-based biofilm challenge for 15 days resulted in a significantly lower μTBS than did the ISO 11405 recommended 6 months of water storage. This type of biofilm-based aging model seems to be a practical method for testing biostability of resin-dentin bonding.

The Cytotoxicity and Genotoxicity of Three Dental Universal Adhesives-An In Vitro Study

Dental universal adhesives are considered an useful tool in modern dentistry as they can be used in different etching techniques, allow for simplified protocol and provide sufficient bond strength. However, there is still no consensus as to their toxicity towards pulp. Thus, the present study aimed to evaluate the cytotoxicity and genotoxicity of three universal adhesives: OptiBond Universal, Prime&Bond Universal and Adhese in an in vitro experimental model, monocyte/macrophage cell line SC (ATCC CRL-9855). The cytotoxicity was measured by means of XTT assay, whereas the genotoxicity (comet assay) was evaluated based on the percentage of DNA present in the comet tail. Furthermore, the ability of the adhesives to induce apoptosis was analyzed using flow cytometry (FC) with the FITC annexin V/propidium iodide (PI) double staining. The analysis of the cell cycle progression was performed with FC using PI staining. OptiBond Universal presented significant, while Prime&Bond Universal and Adhese Universal had minimal cytotoxicity and genotoxicity towards human SC cells. Moreover, only OptiBond Universal increased the level of apoptosis in SC cell line. None of the adhesives showed significant cell cycle arrest, as revealed by FC analysis. Due to substantial differences in toxicity in in vitro studies of dental adhesives, there is a great need for further research in order to establish more reliable test protocols allowing for standardized methodology.

Novel Bioactive and Therapeutic Root Canal Sealers with Antibacterial and Remineralization Properties

According to the American Dental Association Survey of Dental Services Rendered (published in 2007), 15 million root canal treatment procedures are performed annually. Endodontic therapy relies mainly on biomechanical preparation, chemical irrigation and intracanal medicaments which play an important role in eliminating bacteria in the root canal. Furthermore, adequate obturation is essential to confine any residual bacteria within the root canal and deprive them of nutrients. However, numerous studies have shown that complete elimination of bacteria is not achieved due to the complex anatomy of the root canal system. There are several conventional antibiotic materials available in the market for endodontic use. However, the majority of these antibiotics and antiseptics provide short-term antibacterial effects, and they impose a risk of developing antibacterial resistance. The root canal is a dynamic environment, and antibacterial and antibiofilm materials with long-term effects and nonspecific mechanisms of action are highly desirable in such environments. In addition, the application of acidic solutions to the root canal wall can alter the dentin structure, resulting in a weaker and more brittle dentin. Root canal sealers with bioactive properties come in direct contact with the dentin wall and can play a positive role in bacterial elimination and strengthening of the root structure. The new generation of nanostructured, bioactive, antibacterial and remineralizing additives into polymeric resin-based root canal sealers are discussed in this review. The effects of these novel bioactive additives on the physical and sealing properties, as well as their biocompatibility, are all important factors that are presented in this article.

The Influence of Application Protocol of Simplified and Universal Adhesives on the Dentin Bonding Performance

Contemporary adhesives use etch-and-rinse, self-etch, and multimode adhesive strategies. Simplified and universal adhesives present lower bond strength to dentin than conventional, two-bottle etch-and-rinse adhesives. The purpose of this study was to evaluate bonding performance of simplified and universal adhesives to dentin after modifying their application protocol (multiplying applications and extending application time). Adhesive layer thickness (ALT) and shear bond strength (SBS), as well as the correlation between these parameters was calculated. Two universal (Single Bond Universal and Prime & Bond One Select) and two self-etch adhesives (Adper Easy One and Xeno V) were tested. Significant differences in ALT were detected between the adhesives, as well as within the same adhesive between study groups. Tested adhesives presented the thinnest adhesive layer when applied 2 times in 20 s. Single Bond Universal obtained the highest SBS results of all adhesives. Most adhesives (except for Prime & Bond One Select) obtained the highest SBS, when applied two or three times in 40 or 60 s, respectively. No correlation between the ALT and SBS was found. The study showed that increasing the number of applications and extending the application time of self-etch and universal adhesives can be recommended to improve their performance.