Repeated Application and Removal of Polyisocyanopeptide Hydrogel Wound Dressings in a Splinted Full-Thickness Wound Model.

Polyisocyanopeptide (PIC) hydrogels are proposed as promising wound dressings. These gels are thermo-sensitive, allow application as a cold liquid, and rely on gelation through body heat. It is supposed that the gel can be easily removed by reversing the gelation and washing it away with a cold irrigation solution. The impact on wound healing of the regular application and removal of PIC dressings is compared to a single application of PIC and the clinically used Tegaderm™ in murine splinted full-thickness wounds for up to 14 days. SPECT/CT analysis of 111In-labelled PIC gels showed that, on average, 58% of the PIC gel could be washed out of the wounds with the employed method, which is, however, heavily influenced by personal technique. Evaluation with photography and (immuno-)histology showed that wounds in which PIC dressings were regularly removed and replaced were smaller at 14 days post-injury but performed on par with the control treatment. Moreover, the encapsulation of PIC in wound tissue was less severe and occurred less often when PIC was regularly refreshed. In addition, no morphological damage related to the removal procedure was observed. Thus, PIC gels are atraumatic and perform similarly to currently employed wound dressing materials, offering possible future benefits for both clinicians and patients.

Application of specialized pro-resolving mediators in periodontitis and peri-implantitis: a review.

Scaling and root planning is a key element in the mechanical therapy used for the eradication of biofilm, which is the major etiological factor for periodontitis and peri-implantitis. However, periodontitis is also a host mediated disease, therefore, removal of the biofilm without adjunctive therapy may not achieve the desired clinical outcome due to persistent activation of the innate and adaptive immune cells. Most recently, even the resident cells of the periodontium, including periodontal ligament fibroblasts, have been shown to produce several inflammatory factors in response to bacterial challenge. With increased understanding of the pathophysiology of periodontitis, more research is focusing on opposing excessive inflammation with specialized pro-resolving mediators (SPMs). This review article covers the major limitations of current standards of care for periodontitis and peri-implantitis, and it highlights recent advances and prospects of SPMs in the context of tissue reconstruction and regeneration. Here, we focus primarily on the role of SPMs in restoring tissue homeostasis after periodontal infection.

The effect of lipoxin A4 on E. coli LPS-induced osteoclastogenesis.

OBJECTIVES: The objective of the present study was to investigate the effect of lipoxin-type A4 (LXA4) on bacterial-induced osteoclastogenesis. MATERIAL AND METHODS: Human periodontal ligament cells (PDLCs) in coculture with osteoclast precursors (RAW264.7 cells) were exposed to bacterial stimulation with lipopolysaccharide (LPS) to induce inflammation. After 24 h, cells were treated to 100 ng/ml of LXA4 and 50 ng/ml of forymul peptide receptor 2 (FPR2/ALX) receptor antagonist (Boc-2). After 5 days, osteoclastic resorptive activity was assessed on calcium phosphate (CaP) synthetic bone substitute. Additionally, osteoclastic differentiation was evaluated using tartrate-resistant acid phosphatase (TRAP) staining, TRAP enzymatic activity assay, and on the expression of osteoclast-specific genes. RESULTS: We found that stimulation of in the osteoclasts with LPS-stimulated PDLCs induced a significant increase in tartrate-resistant acid phosphatase (TRAP) positive cells, higher resorptive activity, and enhanced expression of specific genes. Meanwhile, LXA4-treatment exhibited strong anti-inflammatory activity, and was able to reverse these inflammatory effects. CONCLUSIONS: We conclude that (1) PDLCs are a potential target for treating bacterial-induced bone resorption in patients with periodontal disease, and (2) LXA4 is a suitable candidate for such therapy. CLINICAL RELEVANCE: The results prove that lipoxins have a protective role in bacterial-induced periodontal inflammation and alveolar bone resorption, which can be translated into a clinical beneficial alterative treatment.

Lipoxin suppresses inflammation via the TLR4/MyD88/NF-κB pathway in periodontal ligament cells.

OBJECTIVE: The objective of the present study was to evaluate the anti-inflammatory effects of lipoxin A4 (LXA4) for the treatment of periodontitis in an in vitro model. METHODS: Human PDLCs were challenged with Escherichia coli (E. coli) lipopolysaccharide (LPS) to evoke an inflammatory response. This was done either in monoculture or in coculture with THP-1, a monocytic cell line. Thereafter, cytokine expression was measured by ELISA, with or without LXA4. In addition, the effects of LXA4 were analyzed on the TLR-MyD88-NF-κB (TMN)-mediated intracellular signal pathway using immunocytochemistry. RESULTS: In response to LPS, the level of the pro-inflammatory cytokine tumor necrosis factor alpha increased, whereas the anti-inflammatory cytokine interleukin-4 decreased significantly (p < .05). These effects were consistently reversed when LPS-challenged PDLCs were also treated with LXA4. The results in the coculture system were comparable to the monoculture. Immunohistochemistry and quantitative assessment confirmed the importance of the TMN signal pathway in these processes. CONCLUSION: These results corroborate earlier findings that PDLCs play an important role in inflammation. Moreover, LXA4 might offer new approaches for the therapeutic treatment of periodontal disease.

Visualization of calcium phosphate cement in teeth by zero echo time 1 H MRI at high field.

1 H magnetic resonance imaging (MRI) by a zero echo time (ZTE) sequence is an excellent method to image teeth. Calcium phosphate cement (CPC) materials are applied in the restoration of tooth lesions, but it has not yet been investigated whether they can be detected by computed tomography (CT) or MRI. The aim of this study was to optimize high-field ZTE imaging to enable the visualization of a new CPC formulation implanted in teeth and to apply this in the assessment of its decomposition in vivo. CPC was implanted in three human and three goat teeth ex vivo and in three goat teeth in vivo. An ultrashort echo time (UTE) sequence with multiple flip angles and echo times was applied at 11.7 T to measure T1 and T2 * values of CPC, enamel and dentin. Teeth with CPC were imaged with an optimized ZTE sequence. Goat teeth implanted with CPC in vivo were imaged after 7 weeks ex vivo. T2 * relaxation of implanted CPC, dentin and enamel was better fitted by a model assuming a Gaussian rather than a Lorentzian distribution. For CPC and human enamel and dentin, the average T2 * values were 273 ± 19, 562 ± 221 and 476 ± 147 µs, respectively, the average T2 values were 1234 ± 27, 963 ± 151 and 577 ± 41 µs, respectively, and the average T1 values were 1065 ± 45, 972 ± 40 and 903 ± 7 ms, respectively. In ZTE images, CPC had a higher signal-to-noise-ratio than dentin and enamel because of the higher water content. Seven weeks after in vivo implantation, the CPC-filled lesions showed less homogeneous structures, a lower T1 value and T2 * separated into two components. MRI by ZTE provides excellent contrast for CPC in teeth and allows its decomposition to be followed.

Periodontal regeneration via chemoattractive constructs.

AIM: Chemoattractants, such as stromal cell-derived factor-1α (SDF-1α), can offer an advantage for periodontal regeneration by recruiting the patient's own stem cells to stimulate self-repair. We here developed a chemoattractive construct for periodontal regeneration using SDF-1α and evaluated its efficacy in vivo. MATERIALS AND METHODS: SDF-1α was loaded on gelatin sponge and tested in vitro for SDF-1α release. Subsequently, SDF-1α constructs were implanted into rat periodontal defects for 1 and 6 weeks, with unloaded materials and empty defects as controls. The regenerative efficacy was evaluated by micro-CT, histological and histomorphometrical analyses. RESULTS: In vitro results showed limited SDF-1α release up to 35 days. In contrast, SDF-1α constructs significantly improved periodontal defect regeneration in terms of alveolar bone height, new bone area and functional ligament length. Additionally, SDF-1α constructs decreased the inflammatory response at Week 6. CONCLUSION: Chemoattractive constructs significantly improved periodontal regeneration in terms of alveolar bone height, new bone area and functional ligament length.

Nanometer-grooved topography stimulates trabecular bone regeneration around a concave implant in a rat femoral medulla model.

In the present study, a method was developed to reproduce two nanogrooved patterns (groove width/ridge width/depth: 150/150/50 nm and 200/800/70 nm) into cylindrical epoxy resin implants, which were subsequently coated with 20 nm of titanium. Also, implants with a conventional surface roughness (Rq=1.6 µm) were produced. After cytocompatibility analysis of the produced surfaces, implants were installed into the femoral condyle of rats for 4 and 8 weeks. The histomorphometrical analysis of bone volume in a 100 µm wide zone close to the implant surface showed that only for the 200/800 grooves the amount of bone increased significantly between 4 and 8 weeks of implantation. In addition, at the late time point only implants with the 200/800 pattern revealed a significantly higher bone volume compared to the rough controls. In conclusion, the 200/800 grooved pattern can positively influence bone volume adjacent to the implant surface, and should be evaluated and optimized in further (pre-)clinical studies.

Antibacterial effects of electrospun chitosan/poly(ethylene oxide) nanofibrous membranes loaded with chlorhexidine and silver.

To prevent percutaneous device associated infections (PDAIs), we prepared electrospun chitosan/poly(ethylene oxide) (PEO) nanofibrous membrane containing silver nanoparticles as an implantable delivery vehicle for the dual release of chlorhexidine and silver ions. We observed that the silver nanoparticles were distributed homogeneously throughout the fibers, and a fast release of chlorhexidine in 2days and a sustained release of silver ions for up to 28days. The antibacterial efficacy of the membranes against Staphylococcus aureus showed that the membranes exhibited an obvious inhibition zone upon loading with either chlorhexidine (20µg or more per membrane) or AgNO3 (1 and 5wt% to polymer). Furthermore, long-term antibacterial effect up to 4days was verified using membranes containing 5wt% AgNO3. The results suggest that the membranes have strong potential to act as an active antibacterial dressing for local delivery of antibacterial agents to prevent PDAIs.

Bone-forming capacity of adult human nasal chondrocytes.

Nasal chondrocytes (NC) derive from the same multipotent embryological segment that gives rise to the majority of the maxillofacial bone and have been reported to differentiate into osteoblast-like cells in vitro. In this study, we assessed the capacity of adult human NC, appropriately primed towards hypertrophic or osteoblastic differentiation, to form bone tissue in vivo. Hypertrophic induction of NC-based micromass pellets formed mineralized cartilaginous tissues rich in type X collagen, but upon implantation into subcutaneous pockets of nude mice remained avascular and reverted to stable hyaline-cartilage. In the same ectopic environment, NC embedded into ceramic scaffolds and primed with osteogenic medium only sporadically formed intramembranous bone tissue. A clonal study could not demonstrate that the low bone formation efficiency was related to a possibly small proportion of cells competent to become fully functional osteoblasts. We next tested whether the cues present in an orthotopic environment could induce a more efficient direct osteoblastic transformation of NC. Using a nude rat calvarial defect model, we demonstrated that (i) NC directly participated in frank bone formation and (ii) the efficiency of survival and bone formation by NC was significantly higher than that of reference osteogenic cells, namely bone marrow-derived mesenchymal stromal cells. This study provides a proof-of-principle that NC have the plasticity to convert into bone cells and thereby represent an easily available cell source to be further investigated for craniofacial bone regeneration.

Reduced Euchromatin histone methyltransferase 1 causes developmental delay, hypotonia, and cranial abnormalities associated with increased bone gene expression in Kleefstra syndrome mice.

Haploinsufficiency of Euchromatin histone methyltransferase 1 (EHMT1), a chromatin modifying enzyme, is the cause of Kleefstra syndrome (KS). KS is an intellectual disability (ID) syndrome, with general developmental delay, hypotonia, and craniofacial dysmorphisms as additional core features. Recent studies have been focused on the role of EHMT1 in learning and memory, linked to the ID phenotype of KS patients. In this study we used the Ehmt1(+/-) mouse model, and investigated whether the core features of KS were mimicked in these mice. When comparing Ehmt1(+/-) mice to wildtype littermates we observed delayed postnatal growth, eye opening, ear opening, and upper incisor eruption, indicating a delayed postnatal development. Furthermore, tests for muscular strength and motor coordination showed features of hypotonia in young Ehmt1(+/-) mice. Lastly, we found that Ehmt1(+/-) mice showed brachycephalic crania, a shorter or bent nose, and hypertelorism, reminiscent of the craniofacial dysmorphisms seen in KS. In addition, gene expression analysis revealed a significant upregulation of the mRNA levels of Runx2 and several other bone tissue related genes in P28 Ehmt1(+/-) mice. Runx2 immunostaining also appeared to be increased. The mRNA upregulation was associated with decreased histone H3 lysine 9 dimethylation (H3K9me2) levels, the epigenetic mark deposited by Ehmt1, in the promoter region of these genes. Together, Ehmt1(+/-) mice indeed recapitulate KS core features and can be used as an animal model for Kleefstra syndrome. The increased expression of bone developmental genes in the Ehmt1(+/-) mice likely contributes to their cranial dysmorphisms and might be explained by diminished Ehmt1-induced H3K9 dimethylation.

Influence of bone marrow-derived mesenchymal stem cells pre-implantation differentiation approach on periodontal regeneration in vivo.

AIM: The implantation of bone marrow-derived mesenchymal stem cells (MSCs) has previously been shown successful to achieve periodontal regeneration. However, the preferred pre-implantation differentiation strategy (e.g. maintenance of stemness, osteogenic or chondrogenic induction) to obtain optimal periodontal regeneration is still unknown. This in vivo study explored which differentiation approach is most suitable for periodontal regeneration. MATERIALS AND METHODS: Mesenchymal stem cells were obtained from Fischer rats and seeded onto poly(lactic-co-glycolic acid)/poly(ɛ-caprolactone) electrospun scaffolds, and then pre-cultured under different in vitro conditions: (i) retention of multilineage differentiation potential; (ii) osteogenic differentiation approach; and (iii) chondrogenic differentiation approach. Subsequently, the cell-scaffold constructs were implanted into experimental periodontal defects of Fischer rats, with empty scaffolds as controls. After 6 weeks of implantation, histomorphometrical analyses were applied to evaluate the regenerated periodontal tissues. RESULTS: The chondrogenic differentiation approach showed regeneration of alveolar bone and ligament tissues. The retention of multilineage differentiation potential supported only ligament regeneration, while the osteogenic differentiation approach boosted alveolar bone regeneration. CONCLUSION: Chondrogenic differentiation of MSCs before implantation is a useful strategy for regeneration of alveolar bone and periodontal ligament, in the currently used rat model.

Evaluation of primary and secondary stability of titanium implants using different surgical techniques.

OBJECTIVE: To investigate the influence of different surgical techniques on the primary and secondary implant stability using trabecular bone of goats as an implantation model. MATERIAL AND METHODS: In the iliac crest of eight goats, 48 cylindrical-screw-type implants with a diameter of 4.2 mm (Dyna(®) ; Bergen op Zoom, the Netherlands) were installed, using three different surgical techniques: (i) 5% undersized, using a final drill diameter of 4 mm; (ii) 15% undersized, using a final drill diameter of 3.6 mm; and (iii) 25% undersized, using a final drill diameter of 3.2 mm. Peak insertion torque values were measured by a Digital(®) (MARK-10 Corporation, New York, NY, USA) torque gauge instrument during placement. At 3 weeks after implantation, removal torque was measured. Histomorphometrically, the peri-implant bone volume was measured in three zones; the inner zone (0-500 µm), the middle zone (500-1000 µm) and the outer zone (1000-1500 µm). RESULTS: Evaluation of the obtained data demonstrated no statistically significant difference between different surgical techniques regarding removal torque values. With respect to the percentage peri-implant bone volume (%BV), also no significant difference could be observed between all three applied surgical techniques for both the inner, middle and outer zone. However, irrespective of the surgical technique, it was noticed that the %BV was significantly higher for the inner zone as compared to middle and outer zone (P < 0.05) around the implant. CONCLUSION: At 3 weeks after implant installation, independent of the used undersized surgical technique, the %BV in the inner zone (0-500 µm) peri-implant area was improved due to both condensation of the surrounding bone as also the translocation of host bone particles along the implant surface. Surprisingly, no mechanical beneficial effect of the 25% undersized surgical technique could be observed as compared to the 5% or 15% undersized surgical technique to improve primary or secondary implant stability.

In vivo comparison between laser-treated and grit blasted/acid etched titanium.

OBJECTIVE: Laser profiling of titanium has been of considerable interest in the field of oral implantology. However, very few pre-clinical and clinical studies have been performed with laser-treated implants, especially focusing on isotropic roughness topography. The aim of the study was to compare the cortical bone response of Ti-implants discs treated with pico-sec pulsed laser (LAS) and conventional grit-blasted/acid-etched (GAE) method. MATERIALS AND METHODS: Prior to the in vivo experiment, in vitro cell viability testing of the LAS surface treatment was preformed. Then, 5 mm diameter Titanium (Ti) discs treated with LAS and GAE method were implanted in a pre-validated rabbit tibia cortical bone model and assessed with histology and histomorphometric measurements. In total, eight New Zealand White adult female rabbits were used. RESULTS: The in vitro cell viability testing with osteoblast-like cells confirmed cytocompatibility of the LAS surface treatment. Further, the rabbit experiment demonstrated a bone-to-implant contact of 68% (±17) for the laser-treated discs and 49% (±21) for the GAE discs 8 weeks after the implantation, which was statistically not different. CONCLUSION: Laser surface treatment gives the same results to the grit-blasting/acid-etched method and thus is a valid alternative to conventional roughening for dental implant materials.

Resolution, sensitivity, and in vivo application of high-resolution computed tomography for titanium-coated polymethyl methacrylate (PMMA) dental implants.

OBJECTIVES: The aims of this study were (i) to determine the spatial resolution and sensitivity of micro- versus nano-computed tomography (CT) techniques and (ii) to validate micro- versus nano-CT in a dog dental implant model, comparative to histological analysis. MATERIAL AND METHODS: To determine spatial resolution and sensitivity, standardized reference samples containing standardized nano- and microspheres were prepared in polymer and ceramic matrices. Thereafter, 10 titanium-coated polymer dental implants (3.2 mm in Ø by 4 mm in length) were placed in the mandible of Beagle dogs. Both micro- and nano-CT, as well as histological analyses, were performed. RESULTS: The reference samples confirmed the high resolution of the nano-CT system, which was capable of revealing sub-micron structures embedded in radiodense matrices. The dog implantation study and subsequent statistical analysis showed equal values for bone area and bone-implant contact measurements between micro-CT and histology. However, because of the limited sample size and field of view, nano-CT was not rendering reliable data representative of the entire bone-implant specimen. CONCLUSIONS: Micro-CT analysis is an efficient tool to quantitate bone healing parameters at the bone-implant interface, especially when using titanium-coated PMMA implants. Nano-CT is not suitable for such quantification, but reveals complementary morphological information rivaling histology, yet with the advantage of a 3D visualization.

The influence of electrospun fibre scaffold orientation and nano-hydroxyapatite content on the development of tooth bud stem cells in vitro.

In stem cell-based dental tissue engineering, the goal is to create tooth-like structures using scaffold materials to guide the dental stem cells. In this study, the effect of fiber alignment and hydroxyapatite content in biodegradable electrospun PLGA scaffolds have been investigated. Fiber orientation of the scaffolds was random or aligned in bundles. For scaffolds with prefabricated orientation, scaffolds were fabricated from PLGA polymer solution containing 0, 10 or 20 % nano-hydroxyapatite. The scaffolds were seeded with porcine cells isolated from tooth buds (dental mesenchymal, dental epithelial, and mixed dental mesenchymal/epithelial cells). Samples were collected at 1, 3 and 6 weeks. Analyses were performed for cell proliferation, ALP activity, and cell morphology. Fiber alignment showed an effect on cell orientation in the first week after cell seeding, but had no long-term effect on cell alignment or organized calcified matrix deposition once the cells reach confluency. Scaffold porosity was sufficient to allow migration of mesenchymal cells. Hydroxyapatite incorporation did not have a positive effect on cell proliferation, especially of epithelial cells, but seemed to promote differentiation. Concluding, scaffold architecture is important to mesenchymal cell morphology, but has no long-term effect on cell alignment or organized ECM deposition. nHA incorporation does have an effect on cell proliferation, differentiation and ECM production, and should be regarded as a bioactive component of dental bioengineered scaffolds.

Biocompatible adipose extracellular matrix and reduced graphene oxide nanocomposite for tissue engineering applications.

Despite the immense need for effective treatment of spinal cord injury (SCI), no successful repair strategy has yet been clinically implemented. Multifunctional biomaterials, based on porcine adipose tissue-derived extracellular matrix (adECM) and reduced graphene oxide (rGO), were recently shown to stimulate in vitro neural stem cell growth and differentiation. Nevertheless, their functional performance in clinically more relevant in vivo conditions remains largely unknown. Before clinical application of these adECM-rGO nanocomposites can be considered, a rigorous assessment of the cytotoxicity and biocompatibility of these biomaterials is required. For instance, xenogeneic adECM scaffolds could still harbour potential immunogenicity following decellularization. In addition, the toxicity of rGO has been studied before, yet often in experimental settings that do not bear relevance to regenerative medicine. Therefore, the present study aimed to assess both the in vitro as well as in vivo safety of adECM and adECM-rGO scaffolds. First, pulmonary, renal and hepato-cytotoxicity as well as macrophage polarization studies showed that scaffolds were benign invitro. Then, a laminectomy was performed at the 10th thoracic vertebra, and scaffolds were implanted directly contacting the spinal cord. For a total duration of 6 weeks, animal welfare was not negatively affected. Histological analysis demonstrated the degradation of adECM scaffolds and subsequent tissue remodeling. Graphene-based scaffolds showed a very limited fibrous encapsulation, while rGO sheets were engulfed by foreign body giant cells. Furthermore, all scaffolds were infiltrated by macrophages, which were largely polarized towards a pro-regenerative phenotype. Lastly, organ-specific histopathology and biochemical analysis of blood did not reveal any adverse effects. In summary, both adECM and adECM-rGO implants were biocompatible upon laminectomy while establishing a pro-regenerative microenvironment, which justifies further research on their therapeutic potential for treatment of SCI.

Enhanced periodontal tissue regeneration by periodontal cell implantation.

AIM: Due to a lack of regenerative potential, current treatments for periodontal defects do not always provide satisfactory clinical results. Previously, the implantation of a biomaterial scaffold-cell construct has been suggested as a clinically achievable approach. In this study, it was aimed to investigate the contribution of implanted periodontal ligament (PDL) cells to periodontal tissue regeneration. MATERIALS & METHODS: Gelatin sponges were seeded with green fluorescent protein (GFP) transfected PDL or gingival fibroblasts (GF) cells, and implanted into a surgically created rat intrabony periodontal defect model. After six weeks, decalcified maxillae were used for histomorphometrical and immunohistochemical analyses. RESULTS: After six weeks, animals that had received the PDL cells exhibited significantly more functional bone and ligament. Furthermore, there were remarkable differences in the distribution of the transplanted cells. Periodontal ligament cells were always located directly lining the newly regenerated areas. In contrast, GF cells dispersed over the whole defect area, and did not provide a favourable effect on the regeneration of the periodontal tissues. CONCLUSION: We concluded that PDL cells transplanted into a periodontal defect survive and favour regeneration of periodontium, possibly in a paracrine manner.

Regeneration of the periodontium using enamel matrix derivative in combination with an injectable bone cement.

OBJECTIVES: Enamel matrix derivative (EMD) has proven to enhance periodontal regeneration; however, its effect is mainly restricted to the soft periodontal tissues. Therefore, to stimulate not only the soft tissues, but also the hard tissues, in this study EMD is combined with an injectable calcium phosphate cement (CaP; bone graft material). The aim was to evaluate histologically the healing of a macroporous CaP in combination with EMD. MATERIALS AND METHODS: Intrabony, three-wall periodontal defects (2 × 2 × 1.7 mm) were created mesial of the first upper molar in 15 rats (30 defects). Defects were randomly treated according to one of the three following strategies: EMD, calcium phosphate cement and EMD, or left empty. The animals were killed after 12 weeks, and retrieved samples were processed for histology and histomorphometry. RESULTS: Empty defects showed a reparative type of healing without periodontal ligament or bone regeneration. As measured with on a histological grading scale for periodontal regeneration, the experimental groups (EMD and CaP/EMD) scored equally, both threefold higher compared with empty defects. However, most bone formation was measured in the CaP/EMD group; addition of CAP to EMD significantly enhanced bone formation with 50 % compared with EMD alone. CONCLUSIONS: Within the limits of this animal study, the adjunctive use of EMD in combination with an injectable cement, although it did not affect epithelial downgrowth, appeared to be a promising treatment modality for regeneration of bone and ligament tissues in the periodontium. CLINICAL RELEVANCE: The adjunctive use of EMD in combination with an injectable cement appears to be a promising treatment modality for regeneration of the bone and ligament tissues in the periodontium.

Association between salivary characteristics and tooth wear: A systematic review and meta-analysis.

OBJECTIVE: Literature was systematically reviewed to identify salivary characteristics and their association with tooth wear. DATA: A protocol was developed a priori (PROSPERO CRD42022338590). Established systematic review methods were used for screening, data extraction, and synthesis. Risk of bias and the certainty of evidence were assessed using the JBI tools and GRADE, respectively. Direct and indirect association between tooth wear and salivary components and characteristics were assessed. SOURCES: MEDLINE, Embase, SCOPUS, Web of Science, CINAHL, and additional sources were searched. STUDY SELECTION: Studies reporting salivary characteristics in patients with tooth wear or models thereof were included. Animal and in-vitro studies and case reports were excluded. RESULTS: One-hundred eleven studies were included. Qualitative analyses showed a negative association between tooth wear and salivary pH and flow rate in many studies. The higher the study size the higher the chances that an association with pH and flow rate was found. Xerostomia, buffer capacity and salivary consistency/viscosity had also some degree of association with tooth wear in fewer studies. Associations with the 39 salivary components were scarcer. Random effects meta-analyses (7 studies) showed that pH levels in stimulated whole saliva were lower in patient with tooth wear compared to controls (-0.07 [-0.10 to -0.04]). However, there was not enough evidence to establish a quantitative association with flow rate. The general risk of bias was unclear and the certainty of evidence was low or very low. A large diversity of methodologies limited the inclusion of all studies in quantitative synthesis. CONCLUSION: From all potential risk factors, stimulated whole saliva pH showed a negative association, both quantitatively and qualitatively with tooth wear, indicating potential usefulness of pH monitoring in these patients. Moreover, associations between flow rate and tooth wear were observed qualitatively. However, in both cases the risk of bias was mostly unclear, and the certainty of evidence was low. No causal associations could be observed. CLINICAL SIGNIFICANCE: Tooth wear is a prevalent condition that may lead to functional or esthetic impairments and pain. Knowing the potential risk factors like salivary pH or flow rate and their dynamics could be relevant during tooth wear monitoring and to intervene accordingly, especially in conditions like gastroesophageal reflux disease.

Cellular Uptake of Modified Mesoporous Bioactive Glass Nanoparticles for Effective Intracellular Delivery of Therapeutic Agents.

Introduction: There has recently been a surge of interest in mesoporous bioactive glass nanoparticles (MBGNs) as multi-functional nanocarriers for application in bone-reconstructive and -regenerative surgery. Their excellent control over their structural and physicochemical properties renders these nanoparticles suitable for the intracellular delivery of therapeutic agents to combat degenerative bone diseases, such as bone infection, or bone cancer. Generally, the therapeutic efficacy of nanocarriers strongly depends on the efficacy of their cellular uptake, which is determined by numerous factors including cellular features and the physicochemical characteristics of nanocarriers, particularly surface charge. In this study, we have systematically investigated the effect of the surface charge of MBGNs doped with copper as a model therapeutic agent on cellular uptake by both macrophages and pre-osteoblast cells involved in bone healing and bone infections to guide the future design of MBGN-based nanocarriers. Methods: Cu-MBGNs with negative, neutral, and positive surface charges were synthesized and their cellular uptake efficiency was assessed. Additionally, the intracellular fate of internalized nanoparticles along with their ability to deliver therapeutic cargo was studied in detail. Results: The results showed that both cell types internalized Cu-MBGNs regardless of their surface charge, indicating that cellular uptake of nanoparticles is a complex process influenced by multiple factors. This similarity in cellular uptake was attributed to the formation of a protein corona surrounding the nanoparticles when exposed to protein-rich biological media, which masks the original nanoparticle surface. Once internalized, the nanoparticles were found to mainly colocalize with lysosomes, exposing them to a more compartmentalized and acidic environment. Furthermore, we verified that Cu-MBGNs released their ionic components (Si, Ca, and Cu ions) in both acidic and neutral environments, leading to the delivery of these therapeutic cargos intracellularly. Conclusion: The effective internalization of Cu-MBGNs and their ability to deliver cargos intracellularly highlight their potential as intracellular delivery nanocarriers for bone-regenerative and -healing applications.