Human neutrophils degrade methacrylate resin composites and tooth dentin

Altered Surrogate Markers of Inflammation in Perinatal HIV-Exposed Children with Caries

OBJECTIVE

Dental caries is associated with immunologic response, yet its association with hematologic parameters and inflammatory markers is unclear. This study aimed to examine the relationship between some surrogate markers of inflammation and dental caries in the context of perinatal exposure to human immunodeficiency virus (HIV).

METHODS

This cross-sectional study involved 2 groups of children aged 4 to 11 y who were (1) HIV exposed but uninfected (HEU) and (2) HIV unexposed/uninfected (HUU) and recruited from HIV pediatric and child outpatient clinics, respectively, at a tertiary health facility in Nigeria. Medical records were reviewed, and trained dentists conducted oral and dental examinations. Five milliliters of EDTA blood was obtained and used for CD4 and CD8 and complete blood analysis, from which other inflammatory markers such as the neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), systemic inflammatory index (SII), CD4/CD8 ratio were calculated using referenced formulas.

RESULTS

In total, 245 (125 HEU and 120 HUU) children with a mean (standard deviation) age of 7 (2) y were included in this study. No differences in caries experience were observed in both groups of children (38 children [16%] were caries affected; 19 [16%] and 19 [15%] from the HEU and HUU groups, respectively). Examining the relationship between studied inflammatory markers and caries showed that leucocyte counts were slightly lower in caries-affected children compared with their caries-free counterparts (P = 0.05). Lower levels of neutrophils (P = 0.04) and higher levels of lymphocytes (P = 0.02) were associated with caries prevalence. Although not significant, NLR, PLR, and SII were lower in caries-affected children.

CONCLUSION

Caries is associated with leucocytes and some of its subsets in both groups of children and independent of perinatal HIV exposure, highlighting the potential of evaluating inflammatory markers in caries prevention, treatment, and research.

KNOWLEDGE TRANSFER STATEMENT

This study provides evidence that a relationship exists between dental caries, HIV exposure, and inflammation using affordable methods and advocates the inclusion of these markers in caries care in resource-limited settings.

Synthesis and challenges of fluorinated divinyl urethane monomers as a strategy for masking hydrolytic sensitive methacrylate groups in resin composites

OBJECTIVE

The biodegradation of methacrylate (MA)-based dental restoratives has been suggested to contribute to a loss of adhesion and subsequent detachment, or secondary caries, both major causes of restoration failure. Previous studies have demonstrated that intermolecular interactions between resin monomers may affect the hydrolytic-susceptibility of composites. Altering the intermolecular interactions by shielding or masking the hydrolytically-susceptible ester groups found in MA monomers could be an effective strategy to mitigate the biodegradation of resin composites. The objective of this work was to assess whether shielding/masking MAs using fluorinated groups could improve the biostability of experimental composites.

METHODS

Eight fluorinated monomers (FM) were synthesized, characterized (1H NMR), and formulated into experimental resin composites (FC, 65 wt%, microfill). FCs were assessed for interactions with water (water contact angle, water sorption, gel fraction), mechanical properties (both compressive and flexural strength and modulus), cytocompatibility, resistance to biodegradation using simulated human salivary esterase (SHSE) and compared to a control composite (CC) without FM.

RESULTS

Integration of FMs was found to generally decrease both the physical and mechanical properties under all incubation conditions when compared to the CC. Additionally, all FCs had a negative influence on composite biodegradation following immersion in SHSE when compared to the CC.

SIGNIFICANCE

Shielding/masking MA-esters inherently inserts molecular spaces between the polymer chains within the resin network, and shielding is likely not possible while also maintaining the necessary cohesive forces that regulate the physical and mechanical properties of resin composites. Novel dental resin development should seek to remove/replace vulnerable ester-containing MAs rather that adopting a shielding/masking approach.

Enterococcal-host interactions in the gastrointestinal tract and beyond

The gastrointestinal tract (GIT) is typically considered the natural niche of enterococci. However, these bacteria also inhabit extraintestinal tissues, where they can disrupt organ physiology and cause life-threatening infections. Here, we discuss how enterococci, primarily Enterococcus faecalis, interact with the intestine and other host anatomical locations such as the oral cavity, heart, liver, kidney, and vaginal tract. The metabolic flexibility of these bacteria allows them to quickly adapt to new environments, promoting their persistence in diverse tissues. In transitioning from commensals to pathogens, enterococci must overcome harsh conditions such as nutrient competition, exposure to antimicrobials, and immune pressure. Therefore, enterococci have evolved multiple mechanisms to adhere, colonize, persist, and endure these challenges in the host. This review provides a comprehensive overview of how enterococci interact with diverse host cells and tissues across multiple organ systems, highlighting the key molecular pathways that mediate enterococcal adaptation, persistence, and pathogenic behavior.

Intraoral ageing of aligners and attachments: Adverse effects on clinical efficiency and release of biologically-active compounds

The clinical application of aligners is accompanied by the ageing of the polymer appliances and the attachments used, which may result in inefficiency in reaching the predicted range of tooth movement, and release of compounds and microplastics in the oral cavity as a result of the friction, wear and attrition of the aligner and composite attachment. The purpose of this review is to present the mechanism and effects of in vivo ageing; describe the hydrolytic degradation of aligners and enzymatic degradation of composite attachments; examine the ageing pattern of aligners in vivo, under actual clinical scenarios; and identify a link to the discrepancy between predicted and actual clinical outcome. Lastly, strategies to deal with three potentially critical issues associated with the use of aligners, namely the necessity of weekly renewal, the dissimilar mechanical properties of aligner and attachment resulting in wear and plastic deformation of the aligner, and the development of integuments and biofilms with microbial colonization of the appliance, are discussed.

Biodegradation of Urethane Dimethacrylate-based materials (CAD/CAM resin-ceramic composites) and its effect on the adhesion and proliferation of Streptococcus mutans

OBJECTIVE

To investigate whether urethane dimethacrylate (UDMA) -based dental restorative materials biodegrade in the presence of Streptococcus mutans (S. mutans) and whether the monomers affect the adhesion and proliferation of S. mutans in turn.

METHODS

Cholesterol esterase and pseudocholinesterase-like activities in S. mutans were detected using p-nitrophenyl substrate. Two UDMA-based CAD/CAM resin-ceramic composites, Lava Ultimate (LU) and Vita Enamic (VE), and a light-cured UDMA resin block were co-cultured with S. mutans for 14 days. Their surfaces were characterized by scanning electron microscopy and laser microscopy, and the byproducts of biodegradation were examined by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS). Then, the antimicrobial components (silver nanoparticles with quaternary ammonium salts) were added to the UDMA resin block to detect whether the biodegradation was restrained. Finally, the effect of UDMA on biofilm formation and virulence expression of S. mutans was assessed.

RESULTS

Following a 14-day immersion, the LU and UDMA resin blocks' surface roughness increased. The LU and VE groups had no UDMA or its byproducts discovered, according to the UPLC-MS/MS data, whereas the light-cured UDMA block group had UDMA, urethane methacrylate (UMA), and urethane detected. The addition of antimicrobial agents showed a significant reduction in the release of UDMA. Biofilm staining experiments showed that UDMA promoted the growth of S. mutans biofilm and quantitative real-time polymerase chain reaction results indicated that 50 μg/mL UDMA significantly increase the expression of gtfB, comC, comD, comE, and gbpB genes within the biofilm.

CONCLUSIONS

UDMA in the light-cured resin can be biodegraded to produce UMA and urethane under the influence of S. mutans. The formation of early biofilm can be promoted and the expression of cariogenic genes can be up-regulated by UDMA.

CLINICAL SIGNIFICANCE

This study focuses for the first time on whether UDMA-based materials can undergo biodegradation and verifies from a genetic perspective that UDMA can promote the formation of S. mutans biofilms, providing a reference for the rational use of UDMA-based materials in clinical practice.

Considerations about Cytotoxicity of Resin-Based Composite Dental Materials: A Systematic Review

The dental material industry is rapidly developing resin-based composites (RBCs), which find widespread use in a variety of clinical settings. As such, their biocompatibility has gained increasing interest. This literature review presents a summary of research into the cytotoxicity of methacrylate-based composites published from 2017 to 2023. Subject to analysis were 14 in vitro studies on human and murine cell lines. Cytotoxicity in the included studies was measured via MTT assay, LDH assay, and WST-1 assay. The QUIN Risk of Bias Tool was performed to validate the included studies. Included studies (based entirely on the results of in vitro studies) provide evidence of dose- and time-dependent cytotoxicity of dental resin-based composites. Oxidative stress and the depletion of cellular glutathione (GSH) were suggested as reasons for cytotoxicity. Induction of apoptosis by RBCs was indicated. While composites remain the golden standard of dental restorative materials, their potential cytotoxicity cannot be ignored due to direct long-term exposure. Further in vitro investigations and clinical trials are required to understand the molecular mechanism of cytotoxicity and produce novel materials with improved safety profiles.

The Role of Bacterial, Dentinal, Salivary, and Neutrophil Degradative Activity in Caries Pathogenesis

Until recently, it was widely accepted that bacteria participate in caries pathogenesis mainly through carbohydrate fermentation and acid production, which promote the dissolution of tooth components. Neutrophils, on the other hand, were considered white blood cells with no role in caries pathogenesis. Nevertheless, current literature suggests that both bacteria and neutrophils, among other factors, possess direct degradative activity towards both dentinal collagen type-1 and/or methacrylate resin-based restoratives and adhesives, the most common dental restoratives. Neutrophils are abundant leukocytes in the gingival sulcus, where they can readily reach adjacent tooth roots or gingival and cervical restorations and execute their degradative activity. In this review, we present the latest literature evidence for bacterial, dentinal, salivary, and neutrophil degradative action that may induce primary caries, secondary caries, and restoration failure.

Degradation and Failure Phenomena at the Dentin Bonding Interface

Damage in the bonding interface is a significant factor that leads to premature failure of dental bonded restorations. The imperfectly bonded dentin-adhesive interface is susceptible to hydrolytic degradation and bacterial and enzyme attack, severely jeopardizing restorations' longevity. Developing caries around previously made restorations, also called "recurrent or secondary caries," is a significant health problem. The replacement of restorations is the most prevailing treatment in dental clinics, leading to the so-called "tooth death spiral". In other words, every time a restoration is replaced, more tooth tissue is removed, increasing the size of the restorations until the tooth is eventually lost. This process leads to high financial costs and detriment to patients' quality of life. Since the complexity of the oral cavity makes prevention a challenging task, novel strategies in Dental Materials and Operative fields are required. This article briefly overviews the physiological dentin substrate, features of dentin bonding, challenges and clinical relevance. We discussed the anatomy of the dental bonding interface, aspects of the degradation at the resin-dentin interface, extrinsic and intrinsic factors affecting dental bonding longevity, perspectives on resin and collagen degradation and how these subjects are connected. In this narrative review, we also outlined the recent progress in overcoming dental bonding challenges through bioinspiration, nanotechnology and advanced techniques to reduce degradation and improve dental bonding longevity.

Dental Implants and Implant Coatings: A Focus on Their Toxicity and Safety

Dental implants are medical devices that are surgically inserted into the patient's jawbone by an orthodontist to act as roots of missing teeth. After the implantation, the maxilla or mandible integrates with the surface of the dental implant. This process, called "osseointegration," is an important period to ensure the long-term use of dental implants and prevent implant failures. Metal implants are the most used implant materials. However, they have disadvantages such as corrosion, metal ion release from metal implant surfaces and associated toxicity. To avoid these adverse effects and improve osseointegration, alternative dental implant materials such as ceramics, polymers, composites, and novel surface modification technologies have been developed. The safety of these materials are also of concern for toxicologists. This review will give general information about dental implant materials, osseointegration and successful implantation process. Moreover, we will focus on the new surface coatings materials for of dental implants and their toxicity and safety concerns will be discussed.

Streptococcus mutans Proteases Degrade Dentinal Collagen

Here, we explored the role of S. mutans’s whole cell and discrete fractions in the degradation of type I collagen and dentinal collagen. Type I collagen gels and human demineralized dentin slabs (DS) were incubated in media alone or with one of the following: overnight (O/N) or newly inoculated (NEW) cultures of S. mutans UA159; intracellular proteins, supernatant or bacterial membranes of O/N cultures. Media from all groups were analyzed for protease-mediated release of the collagen-specific imino acid hydroxyproline. Images of type I collagen and DS were analyzed, respectively. Type I collagen degradation was highest for the supernatant (p < 0.05) fractions, followed by intracellular components and O/N cultures. Collagen degradation for DS samples was highest for O/N samples, followed by supernatant, and intracellular components (p < 0.05). There was lower detectable degradation for both type I collagen and DS from NEW culture samples (p < 0.05), and there was no type I collagen or DS degradation detected for bacterial membrane samples. Structural changes to type I collagen gel and dentinal collagen were observed, respectively, following incubation with S. mutans cultures (O/N and NEW), intracellular components, and supernatant. This study demonstrates that intracellular and extracellular proteolytic activities from S. mutans enable this cariogenic bacterium to degrade type I and dentinal collagen in a growth-phase dependent manner, potentially contributing to the progression of dental caries.

Biodegradation of Dental Resin-Based Composite—A Potential Factor Affecting the Bonding Effect: A Narrative Review

In recent years, although resin composite has played an important role in the restoration of tooth defects, it still has several disadvantages, including being biodegraded by saliva, bacteria and other enzymes in the oral cavity, which may result in repair failure. This factor is not conducive to the long-term survival of the prosthesis in the mouth. In this article, we review the causes, influencing factors and prevention methods of resin biodegradation. Biodegradation is mainly caused by esterase in saliva and bacteria, which breaks the ester bond in resin and causes the release of monomers. The mechanical properties of the prosthesis can then be affected. Meanwhile, cathepsin and MMPs are activated on the bonding surface, which may decompose the dentin collagen. In addition, neutrophils and residual water on the bonding surface can also aggravate biodegradation. Currently, the primary methods to prevent biodegradation involve adding antibacterial agents to resin, inhibiting the activity of MMPs and enhancing the crosslinking of collagen fibers. All of the above indicates that in the preparation and adhesion of resin materials, attention should be paid to the influence of biodegradation to improve the prosthesis’s service life in the complex environment of the oral cavity.

Features of the content of matrix metalloproteinases ММР-9 and ММР-2 in mixed saliva of young individuals with dental caries against the background of different level of 25(OH) vitamin D in the body

The content ofММР-9 and ММР-2 in oral fluid of 105 individuals between the ages of 19 and 23 has been researched.Of these, 42 people are individuals with dental caries and normal level of the active form of vitamin Din serum (25(OH)D >30ng/mL) and 42 people - with 25(OH)D <30 ng/mL level.The control group was composed of 21 individuals with low DMFt index (1,5) and a normal level of 25(OH)D in blood. It has been established that the level of ММР-9 in mixed salivaincreases against the background of dental caries,while the content of ММР-9 and ММР-2 increasessignificantlyamidthe lack and deficiency of25(OH)Din the body. Inverse correlations between the 25(OH)D level in serum and the value ofmatrix metalloproteinasesin saliva have been revealed: noticeable - with the amount of MMP-9 and moderate- with the concentration of MMP-2.

Racial/ethnic inequality in the association of allostatic load and dental caries in children

OBJECTIVES

Allostatic load (AL), defined as the overtime "wear and tear" on biological systems due to stress, disproportionately affects racial/ethnic minorities and has been shown to associate with racial inequality in oral health in the adult population. This study aims to assess racial/ethnic inequality in AL and untreated dental caries (UD) in children, and to assess the association between allostatic load and UD, and whether it varies by race/ethnicity.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) (2001-2010) for 8-17-year-old children (n = 11,378) was used. AL scores were generated using cardiovascular, metabolic and immune biomarkers. Multivariable log binomial regression models adjusted for age, sex, poverty: income ratio (PIR), health insurance status and the frequency of healthcare visits, were used to assess the relationships of interest.

RESULTS

Racial/ethnic inequality was evident in UD and AL, where Mexican American and black children exhibited more UD and a higher AL score than white. AL was associated with UD in fully adjusted models. This association was significant across all racial/ethnic groups, but was stronger in Mexican American and black children, compared to their white counterparts.

CONCLUSIONS

Similar racial inequality is evident in AL and UD that is not explained by poverty and/or behavioral factors. Racial/ethnic inequality is also evident in the association between AL and UD.

Interfacial Biomaterial-Dentin Bacterial Biofilm Proliferation and Viability Is Affected by the Material, Aging Media and Period

Biomaterial−dentin interfaces undergo degradation over time, allowing salivary, tissue fluid, and bacterial movement between the root filling or restoration and dentin. This study aims to investigate the effect of aging in simulated human salivary/bacterial/blood esterases (SHSE) on proliferation and viability of Enterococcus faecalis biofilm within the dentin interface with four materials used to fill/restore the endodontic space. Root canals of human anterior teeth were prepared and filled with gutta-percha and one of the following: self-cured resin composite (BisfilTM 2B, Bisco, Schaumburg, IL, USA) with either self-etch (SE) (EasyBond) or total-etch (TE) (ScotchbondTM, 3M, Saint Paul, MN, USA) methacrylate-based adhesives, epoxy-resin sealer (AH Plus®, Dentsply Sirona, York, PA, USA), or bioceramic sealer (EndoSequence® BC Sealer™, Brasseler USA, Savannah, GA, USA). Specimens were aged in SHSE or phosphate-buffered saline (PBS) for up to 360 days, followed by cultivation of steady-state E. faecalis biofilm. Depth and viability of interfacial bacterial biofilm proliferation were assessed by confocal laser scanning microscopy and live/dead staining. Data were analyzed using three-way ANOVA and Scheffe’s post hoc analyses. Initial depths of biofilm proliferation were similar among material groups (p > 0.05). All groups showed significantly deeper biofilm proliferation with increased aging period (p < 0.05). SHSE aging increased interfacial biofilm depth for TE, SE and BC (p < 0.05) but not AH. For unaged interfaces, BC exhibited the lowest ratio of live bacteria, followed by AH, TE, and SE (p < 0.05). Interfacial bacterial biofilm proliferation and viability were dependent on the biomaterial, aging media, and period.

Simulating the Intraoral Aging of Dental Bonding Agents: A Narrative Review

Despite their popularity, resin composite restorations fail earlier and at higher rates than comparable amalgam restorations. One of the reasons for these rates of failure are the properties of current dental bonding agents. Modern bonding agents are vulnerable to gradual chemical and mechanical degradation from a number of avenues such as daily use in chewing, catalytic hydrolysis facilitated by salivary or bacterial enzymes, and thermal fluctuations. These stressors have been found to work synergistically, all contributing to the deterioration and eventual failure of the hybrid layer. Due to the expense and difficulty in conducting in vivo experiments, in vitro protocols meant to accurately simulate the oral environment’s stressors are important in the development of bonding agents and materials that are more resistant to these processes of degradation. This narrative review serves to summarize the currently employed methods of aging dental materials and critically appraise them in the context of our knowledge of the oral environment’s parameters.

In vitro Study of the Role of Human Neutrophil Enzymes on Root Caries Progression

The role of the host immune system in caries progression is mainly speculative, and it is believed that it entails the enzymatic degradation of the dentin organic matrix. The aim of this study was to evaluate the proteolytic effect of human neutrophil enzymes on root caries progression. For this, specimens of bovine root dentin were divided into 4 groups (n = 30): caries (C), caries + neutrophils (C + N), no caries (Control), and no caries + neutrophils (Control + N). Streptococcus mutans biofilm (105 CFU/mL) was grown on the root surface to artificially induce root carious lesions (C and C + N groups). Specimens were then exposed to neutrophils (5 × 106 cells/mL) for 48 h (C + N and Control + N groups). Caries development and neutrophil exposures were repeated a 2nd and 3rd time. Caries depth (CD) and dentin demineralization (DD) were assessed by infiltration of rhodamine B using fluorescence microscopy. Collagen fibril ultrastructure was characterized under a polarized microscope with Picrosirius red staining. There were no significant differences (p > 0.05) in CD and DD between the C and C + N groups for 1, 2, and 3 caries-neutrophil exposures. Immature collagen was significantly less present in the carious groups (C, p = 0.003; C + N, p = 0.01) than in the noncarious groups in the most superficial 200 µm. We thus concluded that human neutrophil enzymes did not influence short-term root caries progression, and immature collagen fibrils were more susceptible to degradation during S. mutans-induced root caries progression.

Current status on the biodegradability of acrylic polymers: microorganisms, enzymes and metabolic pathways involved

Abstract

Acrylic polymers (AP) are a diverse group of materials with broad applications, frequent use, and increasing demand. Some of the most used AP are polyacrylamide, polyacrylic acid, polymethyl methacrylates, and polyacrylonitrile. Although no information for the production of all AP types is published, data for the most used AP is around 9 MT/year, which gives an idea of the amount of waste that can be generated after products’ lifecycles. After its lifecycle ends, the fate of an AP product will depend on its chemical structure, the environmental setting where it was used, and the regulations for plastic waste management existing in the different countries. Even though recycling is the best fate for plastic polymer wastes, few AP can be recycled, and most of them end up in landfills. Because of the pollution crisis the planet is immersed, setting regulations and developing technological strategies for plastic waste management are urgent. In this regard, biotechnological approaches, where microbial activity is involved, could be attractive eco-friendly strategies. This mini-review describes the broad AP diversity, their properties and uses, and the factors affecting their biodegradability, underlining the importance of standardizing biodegradation quantification techniques. We also describe the enzymes and metabolic pathways that microorganisms display to attack AP chemical structure and predict some biochemical reactions that could account for quaternary carbon-containing AP biodegradation. Finally, we analyze strategies to increase AP biodegradability and stress the need for more studies on AP biodegradation and developing stricter legislation for AP use and waste control.

Key points

• Acrylic polymers (AP) are a diverse and extensively used group of compounds.

• The environmental fates and health effects of AP waste are not completely known.

• Microorganisms and enzymes involved in AP degradation have been identified.

• More biodegradation studies are needed to develop AP biotechnological treatments.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-020-11073-1.

Antimicrobial antidegradative dental adhesive preserves restoration-tooth bond

OBJECTIVE

Assess the ability of an antimicrobial drug-releasing resin adhesive, containing octenidine dihydrochloride (OCT)-silica co-assembled particles (DSPs), to enhance the biostability and preserve the interfacial fracture toughness (FT) of composite restorations bonded to dentin. Enzyme-catalyzed degradation compromises the dental restoration-tooth interface, increasing cariogenic bacterial infiltration. In addition to bacterial ingress inhibition, antimicrobial-releasing adhesives may exhibit direct interfacial biodegradation inhibition as an additional benefit.

METHODS

Mini short-rod restoration bonding specimens with total-etch adhesive with/without 10% wt. DSPs were made. Interfacial fracture toughness (FT) was measured as-manufactured or post-incubation in simulated human salivary esterase (SHSE) for up to 6-months. Effect of OCT on SHSE and whole saliva/bacterial enzyme activity was assessed. Release of OCT outside the restoration interface was assessed.

RESULTS

No deleterious effect of DSPs on initial bonding capacity was observed. Aging specimens in SHSE reduced FT of control but not DSP-adhesive-bonded specimens. OCT inhibited SHSE degradation of adhesive monomer and may inhibit endogenous proteases. OCT inhibited bacterial esterase and collagenase. No endogenous collagen breakdown was detected in the present study. OCT increased human saliva degradative esterase activity below its minimum inhibitory concentration towards S. mutans (MIC), but inhibited degradation above MIC. OCT release outside restoration margins was below detection.

SIGNIFICANCE

DSP-adhesive preserves the restoration bond through a secondary enzyme-inhibitory effect of released OCT, which is virtually confined to the restoration interface microgap. Enzyme activity modulation may produce a positive-to-negative feedback switch, by increasing OCT concentration via biodegradation-triggered release to an effective dose, then subsequently slowing degradation and degradation-triggered release.

Human neutrophils compromise the restoration-tooth interface

Neutrophils, cells of the innate immune system, enter the mouth and release factors that are hypothesized to contribute to the degradation of tooth dentin, methacrylate resin composites, and adhesives at the restoration-tooth-dentin interface. The objectives were to characterize neutrophils' degradation towards resin composite, self-etch (SE) and total-etch (TE) adhesives, SE and TE resin-dentin interfaces and to identify proteins that could contribute to the degradation process. Neutrophils' degradation of cured resin composite, and SE and TE adhesives, was quantified by measuring the specific resin degradation by-product, bishydroxy-propoxy-phenyl-propane (bisHPPP), released after 30 days incubation of the materials with the cells. Neutrophils' degradative effect on resin-dentin interfaces was examined by recording the interfacial fracture toughness (FT), and surface analysis of the fracture mode following incubation of SE and TE miniature short-rod (mini-SR) specimens with the cells. Neutrophils increased degradation of polymerized resin composite, and TE adhesive, but not SE adhesive over 30 days (p < 0.05). Incubation of SE and TE resin-dentin interfaces with neutrophils led to a reduction in FT over time (p < 0.05). The effect was more pronounced for TE interfaces. Neutrophils also affected the fracture mode of SE and TE resin-dentin interfaces. Several proteins that could contribute to the degradative activity of neutrophils, including Neutrophil collagenase (MMP-8), Matrix metalloproteinase- 9 (MMP-9), Cathepsin G, Neutrophil- gelatinase associated lipocalin (NGAL) and Myeloperoxidase, were isolated. The ability of neutrophils to degrade resin, tooth dentin, and reduce the bond strength of resin-dentin interfaces suggest neutrophils' potential role in primary and recurrent caries and dental restoration failure.

18-month clinical evaluation of a copper-containing universal adhesive in non-carious cervical lesions: A double-blind, randomized controlled trial

OBJECTIVE

This study aimed to evaluate the addition of copper nanoparticles (CuNp) on the clinical performance of a universal adhesive system used as etch-and-rinse (ER) and self-etch (SE).

METHODS

216 restorations were randomly placed in 36 subjects according to the following groups: ERcu = etch-and-rinse with 0.1% CuNp; ERct = etch-and-rinse without CuNp; SEcu = self-etch with 0.1% CuNp; SEct = self-etch without CuNp. Resin composite was placed incrementally and light-cured. The restorations were evaluated at baseline and 6, 12 and 18 months using the FDI and USPHS criteria. Statistical analyses were performed using appropriate tests (α = 0.05).

RESULTS

The addition of CuNp did not increase the clinical performance (FDI / USPHS) of the universal adhesive tested after 18-month when applied in the ER mode (p > 0.05). The addition of CuNp in SE restorations increased the retention rate significantly and decreased the marginal discrepancies after 18 months (p < 0.05).

CONCLUSION

The clinical performance of universal adhesive was significantly increased when applied in the SE mode with the addition of copper nanoparticles.

CLINICAL RELEVANCE

This is the first study that demonstrates a slight improvement in the clinical performance of universal adhesive systems in non-carious cervical lesions when added CuNp in lower concentration.

Insights From Dynamic Neuro-Immune Imaging on Murine Immune Responses to CNS Damage

Evolving technologies and increasing understanding of human physiology over the past century have afforded our ability to intervene on human diseases using implantable bio-materials. These bio-electronic devices present a unique challenge through the creation of an interface between the native tissue and implantable bio-materials: the generation of host immune response surrounding such devices. While recent developments in cancer immunology seek to stimulate the immune system against cancer, successful long-term application of implantable bio-material devices need to durably minimize reactive immune processes at involved anatomical sites. Peripheral immune system response has been studied extensively for implanted bio-materials at various body sites. Examples include tooth composites (Gitalis et al., 2019), inguinal hernia repair (Heymann et al., 2019), and cardiac stents and pacemaker leads (Slee et al., 2016). Studies have also been extended to less well-studied immune reactivity in response to CNS neural-electronic implant devices. Recent technological advances in 2-Photon Laser Scanning Microscopy (2P-LSM) have allowed novel insights into in vivo immune response in a variety of tissue microenvironments. While imaging of peripheral tissues has provided an abundance of data with regards to immune cell dynamics, central nervous system (CNS) imaging is comparatively complicated by tissue accessibility and manipulation. Despite these challenges, the results of dynamic intravital neuro-immune imaging thus far have provided foundational insights into basic CNS biology. Utilizing a combination of intravital and ex vivo 2P-LSM, we have observed novel pathways allowing immune cells, stromal cells, cancer cells and proteins to communicate between the CNS parenchyma and peripheral vasculature. Similar to what has been reported in the intestinal tract, we have visualized myeloid cells extend dendritic processes across the blood brain barrier (BBB) into pial blood vessels. Furthermore, transient vessel leaks seen during systemic inflammation provide opportunities for cellular protein to be exchanged between the periphery and CNS. These insights provide new, visual information regarding immune surveillance and antigen presentation within the CNS. Furthermore, when combining intravital 2P-LSM and microfluidic devices complexed with mathematical modeling, we are gaining new insights into the intravascular behavior of circulating immune cells. This new knowledge into the basic mechanisms by which cells migrate to and interact with the CNS provide important considerations for the design of neuro-electronic biomaterials that have the potential to connect the peripheral-neural microenvironments into a unique, artificial interface.