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Background Peri-implant health depends on the complex interactions between the dental implant, surrounding soft/hard tissues and the oral microbial environment. However, existing 2D and monoculture models fail to replicate this complexity, limiting their clinical relevance. Therefore, this study aimed to develop a clinically relevant 3D in vitro model that integrates oral soft tissue, hard tissue and a titanium implant in a 3D setup to accurately replicate the peri-implant environment. In addition, the model was designed to integrate bacterial biofilms, in order to mimic incipient peri-implant infections. Methods As a hard tissue component, osteoblast-covered HA/TCP scaffold structures were developed and merged with peri-implant mucosa, resulting in a 3D in vitro peri-implant bone-mucosa composite model. The composite model was then cultivated for 2, 7 and 14 days. At each time point, histological analysis, live/dead staining and collagen immunofluorescence staining were performed to assess its structural integrity, osteoblast viability and bone ECM characteristics. To demonstrate proof-of-concept for suitability in simulating implant infection, an oral multispecies biofilm was integrated on top of the implant in the peri-implant bone-mucosa model. Results Cell viability and osteoblastic phenotype were maintained throughout the study period. Microscopic and histological analyses confirmed a homogenous structure, with a stratified epithelium overlying collagen-embedded human gingival fibroblasts closely connected to the underlying scaffold structure interspersed with bone cells. Combined with a living multispecies biofilm, this model represents several essential components observed in peri-implant interaction. Conclusions By combining oral soft tissue, hard tissue and a titanium implant in a 3D setup, this model represents the first and most complex model for evaluating innovative implant materials and novel treatment strategies as well as studying the development of peri-implant diseases. Incorporating different biofilms could enhance the model’s clinical relevance, enabling the study of pro-inflammatory responses to bacterial infections in a setting that includes both soft and hard tissue.

Staphylococcus aureus biofilm-associated infections are a common complication in modern medicine. Due to inherent resilience of biofilms to antibiotics and the rising number of antibiotic-resistant bacterial strains, new treatment options are required. For this purpose, ultrapure, spherical silver–gold-alloy nanoparticles with homogenous elemental distribution were synthesized by laser ablation in liquids and analyzed for their antibacterial activity on different stages of S. aureus biofilm formation as well as for different viability parameters. First, the effect of nanoparticles against planktonic bacteria was tested with metabolic activity measurements. Next, nanoparticles were incubated with differently matured S. aureus biofilms, which were then analyzed by metabolic activity measurements and three dimensional live/dead fluorescent staining to determine biofilm volume and membrane integrity. It could be shown that AgAu NPs exhibit antibacterial properties against planktonic bacteria but also against early-stage and even mature biofilms, with a complete diffusion through the biofilm matrix. Furthermore, AgAu NPs primarily targeted metabolic activity, to a smaller extend membrane integrity, but not the biofilm volume. Additional molecular analyses using qRT-PCR confirmed the influence on different metabolic pathways, like glycolysis, stress response and biofilm formation. As this shows clear similarities to the mechanism of pure silver ions, the results strengthen silver ions to be the major antibacterial agent of the synthesized nanoparticles. In summary, the results of this study provide initial evidence of promising anti-biofilm characteristics of silver–gold-alloy nanoparticles and support the importance of further translation-oriented analyses in the future.

Bacterial biofilms on dental implants can lead to peri-implant infections and demonstrate a remarkable ability to evade host immunity and resist antibiotics. Advanced in vitro models, such as the three-dimensional implant-tissue-oral-bacterial-biofilm model (INTER b ACT), are essential to evaluate antibiofilm efficacy. The INTER b ACT model, effectively reproduces the complex triangular interactions between an organotypic oral mucosa, an integrated implant and an oral multispecies biofilms, in the peri-implant situation. Here, we investigated the effect of antibacterial agents (chlorhexidine, amoxicillin, ciprofloxacin, doxycycline, and metronidazole) on biofilm-tissue interactions in the INTER b ACT model. While the antibacterial interventions had no effect on biofilm volume, all agents decreased the proportion of viable bacteria, underscoring their effect on bacterial viability despite biofilm resilience. Biofilm exposure to untreated tissues caused epithelial damage, whereas all antibacterial agents preserved epithelial integrity. However, the modulation of pro-inflammatory response differed between the various agents. All antibacterial treatments reduced hBD-2 and TIMP-1 levels. While doxycycline decreased IL-1β and CCL20, chlorhexidine lowered TNF-α level. In conclusion, the INTER b ACT model allowed the successful assessment of antibacterial efficacy, elucidation of biofilm resistance and characterization of inflammation during peri-implant tissue-biofilm interactions. This validation highlights the model’s potential as a platform for developing and evaluating new therapeutic strategies for peri-implant diseases.

Regulation at the RNA level by RNA-binding proteins (RBPs) and microRNAs (miRNAs) is key to coordinating eukaryotic gene expression. In plants, the importance of miRNAs is highlighted by severe developmental defects in mutants impaired in miRNA biogenesis. MiRNAs are processed from long primary-microRNAs (pri-miRNAs) with internal stem-loop structures by endonucleolytic cleavage. The highly structured stem-loops constitute the basis for the extensive regulation of miRNA biogenesis through interaction with RBPs. However, trans-acting regulators of the biogenesis of specific miRNAs are largely unknown in plants. Therefore, we exploit an RNA-centric approach based on modified versions of the conditional CRISPR nuclease Csy4* to pull down interactors of the Arabidopsis pri-miR398b stem-loop (pri-miR398b-SL) in vitro. We designed three epitope-tagged versions of the inactive Csy4* for the immobilization of the protein together with the pri-miR398b-SL bait on high affinity matrices. After incubation with nucleoplasmic extracts from Arabidopsis and extensive washing, pri-miR398b-SL, along with its specifically bound proteins, were released by re-activating the cleavage activity of the Csy4* upon the addition of imidazole. Co-purified proteins were identified via quantitative mass spectrometry and data sets were compared. In total, we identified more than 400 different proteins, of which 180 are co-purified in at least two out of three independent Csy4*-based RNA pulldowns. Among those, the glycine-rich RNA-binding protein AtRZ-1a was identified in all pulldowns. To analyze the role of AtRZ-1a in miRNA biogenesis, we determined the miR398 expression level in the atrz-1a mutant. Indeed, the absence of AtRZ-1a caused a decrease in the steady-state level of mature miR398 with a concomitant reduction in pri-miR398b levels. Overall, we show that our modified Csy4*-based RNA pulldown strategy is suitable to identify new trans-acting regulators of miRNA biogenesis and provides new insights into the post-transcriptional regulation of miRNA processing by plant RBPs.

Periodontitis is one of the most common infectious diseases in humans. It is characterized by a chronic inflammation of the tooth-supporting tissue that results in bone loss. However, the role and source of the pro-inflammatory cytokine interleukin-17 (IL-17) and of the cells producing it locally in the gingiva is still controversial. Th17 αβ T cells, CD4 + exFoxP3 + αβ T cells, or IL-17-producing γδ T cells (γδ17 cells) seem to be decisive cellular players in periodontal inflammation. To address these issues in an experimental model for periodontitis, we employed genetic mouse models deficient for either γδ T cells or IL-17 cytokines and assessed the bone loss during experimental periodontal inflammation by stereomicroscopic, histological, and μCT-analysis. Furthermore, we performed flow-cytometric analyses and qPCR-analyses of the gingival tissue. We found no γδ T cell- or IL-17-dependent change in bone loss after four weeks of periodontitis. Apart from that, our data are complementary with earlier studies, which suggested IL-17-dependent aggravation of bone loss in early periodontitis, but a rather bone-protective role for IL-17 in late stages of experimental periodontitis with respect to the osteoclastogenicity defined by the RANKL/OPG ratio.

Even though metagenomics have revolutionized the characterization of the human microbiome, detailed mechanistic studies are impracticable, as there is a dearth of robust culture collections. We now describe the development and use of a laser-assisted culturomics platform, incorporating the elements of a bioprinter, the culture conditions, the methods to characterize the microorganisms and a biobank. With laser-assisted bioprinting, the microorganisms can be rapidly and precisely transferred from clinical biofilms to highly organized arrays of microbial colonies, which are suitable for co-culturing and molecular analyses. The presented technique has propagated 99 of 100 microbial species and recovered 79% of abundant species from dental plaque in accordance with full 16S rRNA gene profiling of 691,199 sequences. Microscopy, spectroscopy and enzyme assays have been used to guide isolations. Processing of oral biofilms from four individuals has yielded 249 representative isolates, from 14 classes and 124 species in total. Functional profiling with bioprinting has indicated commensals which could potentially contribute to disease development. Isolates from peri-implantitis cover 85.4% of the transcriptionally active clinical biofilms at genus level. Taken together, this work provides the basis for generating on-demand culture collections and biofilms for research and clinical use. Representative microbial isolates and patient-specific biobanks are crucial for microbiome investigation and management. Here, authors develop laser-assisted microbial culturomics, combining high-throughput, precise bioprinting on diverse media with rapid, non-invasive analyses.

Smoking, a risk factor for periodontitis and peri-implantitis, is associated with shifts in the oral microbiome (OM) composition. Although smoking habits are almost always established before adulthood, data on effects of smoking on the OM in adolescents is rare. The aim of this study was to investigate the early impact of smoking on the OM composition in pupils. The adolescent cohort, aged 14–20, comprised 98 smokers and 98 non-smokers matched for several physiological co-variates. Buccal swabs were analysed for OM composition using high-throughput sequencing of the full-length 16 S rRNA gene targeting species-level resolution. Parameters of bacterial diversity and abundance of individual bacterial taxa were related to information on smoking. The microbiome dataset contained 733 species-level taxa. Streptococcus , Rothia , and Haemophilus dominated both groups, smokers and non-smokers. Smoking exerted a discernible influence on the overall microbial composition as measured by weighted UniFrac distances. The number of species-level bacterial taxa was significantly higher in individual smokers compared to non-smokers. Furthermore, several taxa, including known pathogens, exhibited significant differences in abundance between the two groups. The genera Veillonella , and Actinomyces , as well as and multiple Actinomyces species, Dialister invisus , Atopobium parvulum , Streptococcus mutans and Prevotella melaninogenica were significantly more abundant in smokers. Our findings indicated an early onset of smoking-related changes already in the oral microbiome of adolescents.

Background Peri-implant mucositis and peri-implantitis are highly prevalent biofilm-associated diseases affecting the tissues surrounding dental implants. As antibiotic treatment is ineffective to fully cure biofilm mediated infections, antimicrobial modifications of implants to reduce or prevent bacterial colonization are called for. Preclinical in vivo evaluation of the functionality of new or modified implant materials concerning bacterial colonization and peri-implant health is needed to allow progress in this research field. For this purpose reliable animal models are needed. Methods Custom made endosseous dental implants were installed in female Sprague Dawley rats following a newly established three-step implantation procedure. After healing of the bone and soft tissue, the animals were assigned to two groups. Group A received a continuous antibiotic treatment for 7 weeks, while group B was repeatedly orally inoculated with human-derived strains of Streptococcus oralis , Fusobacterium nucleatum and Porphyromonas gingivalis for six weeks, followed by 1 week without inoculation. At the end of the experiment, implantation sites were clinically assessed and biofilm colonization was quantified via confocal laser scanning microscopy. Biofilm samples were tested for presence of the administered bacteria via PCR analysis. Results The inner part of the custom made implant screw could be identified as a site of reliable biofilm formation in vivo . S. oralis and F. nucleatum were detectable only in the biofilm samples from group B animals. P. gingivalis was not detectable in samples from either group. Quantification of the biofilm volume on the implant material revealed no statistically significant differences between the treatment groups. Clinical inspection of implants in group B animals showed signs of mild to moderate peri-implant mucositis (4 out of 6) whereas the mucosa of group A animals appeared healthy (8/8). The difference in the mucosa health status between the treatment groups was statistically significant ( p  = 0.015). Conclusions We developed a new rodent model for the preclinical evaluation of dental implant materials with a special focus on the early biofilm colonization including human-derived oral bacteria. Reliable biofilm quantification on the implant surface and the symptoms of peri-implant mucositis of the bacterially inoculated animals will serve as a readout for experimental evaluation of biofilm-reducing modifications of implant materials.

Although implants have undergone a remarkable development over the past decades, modern implants still show complications that make the improvement of materials necessary. The presented study investigates the load-bearing capacity of an experimental dental implant made of a niobium alloy (Nb1Zr) compared to identical implants made of Ti6Al4V using chewing simulation for artificial aging. Eight implants each with an experimental design were manufactured from Nb1Zr and Ti6Al4V. A standardized abutment made of Ti6Al4V was fabricated for each implant and screwed into the implant with a screw made of the same material. A shape-identical crown for an upper first molar was fabricated for all implants using the CAD/CAM technique. All specimens were artificially aged using chewing simulation for 1 × 10 6 cycles and thermocycling between 5 °C and 55 °C for 4 × 10 3 cycles. After that, all specimens were loaded until failure. This was followed by a 3D analysis of the deformation of the samples. 100% of the samples survived the artificial aging. The Nb1Zr samples failed at 2595 ± 1069 N. In the Ti6Al4V group, failure occurred at 2958 ± 1058 N. The first deformations occurred in both groups from a load of at least 1114 N. The 3D analysis revealed deformations of 0.08 mm in the implant shoulder area of the Nb1Zr implants and of 0.04 mm in the Ti6Al4V implants. This difference was significant ( p  = 0.016). The investigated Nb1Zr alloy appears to be suitable for implants. The measured load-bearing capacity is significantly higher than the expected intraoral masticatory forces. Graphical Abstract

Peri-implantitis caused by multispecies biofilms is a major complication in dental implant treatment. The bacterial infection surrounding dental implants can lead to bone loss and, in turn, to implant failure. A promising strategy to prevent these common complications is the development of implant surfaces that inhibit biofilm development. A reproducible and easy-to-use biofilm model as a test system for large scale screening of new implant surfaces with putative antibacterial potency is therefore of major importance. In the present study, we developed a highly reproducible in vitro four-species biofilm model consisting of the highly relevant oral bacterial species Streptococcus oralis, Actinomyces naeslundii, Veillonella dispar and Porphyromonas gingivalis. The application of live/dead staining, quantitative real time PCR (qRT-PCR), scanning electron microscopy (SEM) and urea-NaCl fluorescence in situ hybridization (urea-NaCl-FISH) revealed that the four-species biofilm community is robust in terms of biovolume, live/dead distribution and individual species distribution over time. The biofilm community is dominated by S. oralis, followed by V. dispar, A. naeslundii and P. gingivalis. The percentage distribution in this model closely reflects the situation in early native plaques and is therefore well suited as an in vitro model test system. Furthermore, despite its nearly native composition, the multispecies model does not depend on nutrient additives, such as native human saliva or serum, and is an inexpensive, easy to handle and highly reproducible alternative to the available model systems. The 96-well plate format enables high content screening for optimized implant surfaces impeding biofilm formation or the testing of multiple antimicrobial treatment strategies to fight multispecies biofilm infections, both exemplary proven in the manuscript.