PURPOSE:This study evaluated the antibacterial activity of two hydraulic calcium silicate-based sealers, NeoSealer Flo and AH Plus Bioceramic, against Enterococcus faecalis (E. faecalis) biofilm and their biocompatibility with pre-osteoblastic cells. METHODS:Thirty-one extracted human lower incisors with single canals were inoculated with E. faecalis, and their root canals were subjected to three types of filling: A) NeoSealer Flo (n = 10), B) AH Plus Bioceramic (n = 10), and C) positive control (n = 10), as well as one negative control. The teeth were embedded in resin and sectioned at their coronal, middle, and apical thirds, yielding 160 sections. Bacterial viability was assessed by confocal laser scanning microscopy using LIVE/DEAD staining. Biocompatibility was evaluated using the bicinchoninic acid protein assay and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. RESULTS:NeoSealer Flo and AH Plus Bioceramic showed comparable antibacterial activity. In the coronal third of the tooth, viable bacteria were estimated at 44.1 ± 4.0% and 43.5 ± 4.0%, respectively, versus 85.7 ± 5.2% in controls. Similar results were obtained in the middle and apical thirds. Viability was significantly higher in the coronal third (P < 0.05). No significant differences in cell number or protein expression were observed between the sealers and the controls (P > 0.05). CONCLUSION:Both sealers demonstrated similar antibacterial effectiveness and biocompatibility, with greater bacterial viability in the coronal region.

PEL is a B-cell non-Hodgkin lymphoma, occurring predominantly as a lymphomatous effusion in body cavities, characterized by aggressive clinical course, with no standard therapy. Based on previous reports that PEL cells display a Warburg phenotype, we hypothesized that the highly hypoxic environment in which they grow in vivo makes them more reliant on glycolysis, and more vulnerable to drugs targeting this pathway. We established here that indeed PEL cells in hypoxia are more sensitive to glycolysis inhibition. Furthermore, since PI3K/Akt/mTOR has been proposed as a drug target in PEL, we ascertained that pathway-specific inhibitors, namely the dual PI3K and mTOR inhibitor, PF-04691502, and the Akt inhibitor, Akti 1/2, display improved cytotoxicity to PEL cells in hypoxic conditions. Unexpectedly, we found that these drugs reduce lactate production/extracellular acidification rate, and, in combination with the glycolysis inhibitor 2-deoxyglucose (2-DG), they shift PEL cells metabolism from aerobic glycolysis towards oxidative respiration. Moreover, the associations possess strong synergistic cytotoxicity towards PEL cells, and thus may reduce adverse reaction in vivo, while displaying very low toxicity to normal lymphocytes. Finally, we showed that the association of 2-DG and PF-04691502 maintains its cytotoxic and proapoptotic effect also in PEL cells co-cultured with human primary mesothelial cells, a condition known to mimic the in vivo environment and to exert a protective and pro-survival action. All together, these results provide a compelling rationale for the clinical development of new therapies for the treatment of PEL, based on combined targeting of glycolytic metabolism and constitutively activated signaling pathways.

Silver nanoparticles (AgNPs) hold great promise in biomedical applications due to their unique properties and potential for specific tissue targeting. However, the clinical translation of nanoparticle-based therapeutics remains challenging, primarily due to an incomplete understanding of how nanoparticle properties influence interactions at the nano-bio interface, as well as the role of surface-adsorbed proteins (i.e., protein corona) in modulating nanoparticle-cell interactions. This study demonstrates that the surface charge has a greater influence than protein corona formation in determining the cytotoxicity, cellular uptake, and biodistribution of AgNPs. Using negatively and positively charged AgNPs, we show that while protein corona formation is essential for ensuring nanoparticle availability for cellular interactions, the adsorption of biomolecules is nonspecific and independent of surface charge. Conversely, the surface charge significantly influences the interactions of AgNPs with cells. Positively charged nanoparticles exhibit enhanced cellular uptake, preferential accumulation in lysosomes, and pronounced mitochondrial damage compared to their negatively charged counterparts, resulting in greater cytotoxic effects. This effect is particularly evident in human breast cancer cells, where negatively charged nanoparticles show minimal uptake and cytotoxicity. These findings demonstrate that surface charge is the primary factor governing nanoparticle-cell interactions rather than protein corona formation. Nonetheless, the protein corona plays a critical role in stabilizing nanoparticles in physiological environments.

Atomic force microscopy (AFM)-based nanoindentation enables investigation of the mechanical response of biological materials at a subcellular scale. However, quantitative estimates of mechanical parameters such as the elastic modulus (E) remain unreliable because the influence of sample roughness on E measurements at the nanoscale is still poorly understood. This study re-examines the interpretation of roughness from a more rigorous perspective and validates an experimental methodology to extract roughness at each nanoindentation site—i.e., the local roughness γs—with which the corresponding E value can be accurately correlated. Cortical regions of a murine tibia cross-section, characterized by complex nanoscale morphology, were selected as a testbed. Eighty non-overlapping nanoindentations were performed using two different AFM tips, maintaining a maximum penetration depth of 10 nm for each measurement. Our results show a slight decreasing trend of E versus γs (Spearman’s rank correlation coefficient ρ = −0.27187). A total of 90% of the E values are reliable when γs < 10 nm (coefficient of determination R2 > 0.90), although low γs values are associated with significant dispersion around E (γs = 0) = E0 = 1.18 GPa, with variations exceeding 50%. These findings are consistent with a qualitative tip-to-sample contact model that accounts for the pronounced roughness heterogeneity typical of bone topography at the nanoscale.

Background/Objectives: Engineered nanomaterials, particularly silver nanoparticles (AgNPs), have emerged as promising tools in oncology due to their ability to enhance tumor targeting and minimize off-target effects. This study investigates the cytotoxic effects of two different types of AgNPs—citrate-coated (AgNPs-cit) and EG6OH-coated (AgNPs-EG6OH)—on colorectal cancer (CRC) cell lines and healthy colonocytes, aiming to assess their potential as selective therapeutic agents. Methods: AgNPs-cit and AgNPs-EG6OH were synthesized and characterized for size and surface properties. LoVo (microsatellite instability-high) and HT-29 (microsatellite stable) CRC cell lines, along with primary colonocyte cultures from healthy mucosal tissues, were exposed to these nanoparticles. Cytotoxicity was assessed through MTT assays, while morphological changes were observed using fluorescence microscopy. Internalization of the nanoparticles was evaluated by confocal microscopy. Results: AgNPs-cit exhibited significant cytotoxicity in LoVo cells, reducing viability and inducing morphological changes indicative of programmed cell death, especially after 48 h of exposure. In contrast, AgNPs-EG6OH showed minimal effects on LoVo cells and no significant toxicity on HT-29 cells or primary colonocytes. Confocal microscopy confirmed nanoparticle internalization, with surface functionalization influencing the distribution patterns within cells. Conclusions: This study demonstrates that surface functionalization significantly influences the cytotoxicity of AgNPs, with citrate-coated nanoparticles showing selective effects on microsatellite instability-high CRC cells. These findings underscore the potential of surface-modified nanoparticles for targeted cancer therapy and highlight the importance of tailoring nanoparticle design to optimize therapeutic efficacy while minimizing off-target effects.

Ankrd2, a mechanoresponsive protein primarily studied in muscle physiology, is emerging as a player in cancer progression. This study investigates the functional role of Ankrd2 in osteosarcoma cells, revealing its critical involvement in cell proliferation and response to chemotherapeutic drugs. We showed that Ankrd2 knockdown impairs the activation of PI3K/Akt and ERK1/2 pathways, reduces levels of cell cycle regulators including cyclin D1 and cyclin B, and counteracts the expression of nuclear lamin A and lamin B, disrupting nuclear morphology and DNA integrity. Strikingly, the loss of Ankrd2 enhances the sensitivity of osteosarcoma cells to doxorubicin and cisplatin, highlighting Ankrd2 potential as a therapeutic target to improve chemotherapeutic efficacy. Defining a novel mechanistic role for Ankrd2 in promoting tumor progression, we propose that Ankrd2 reduction could be exploited as an adjuvant strategy to enhance the efficacy of chemotherapy, offering new therapeutic opportunities for OS treatment.

Galectin-3 (Gal-3) is a pleiotropic lectin produced by most cell types, which regulates multiple cellular processes in various tissues. In bone, depending on its cellular localization, Gal-3 has a dual and opposite role. If, on the one hand, intracellular Gal-3 promotes bone formation, on the other, its circulating form affects bone remodeling, antagonizing osteoblast differentiation and increasing osteoclast activity. From an analysis of the secretome of cultured differentiating myoblasts, we interestingly found the presence of Gal-3. After that, we confirmed that Gal-3 was expressed and released in the extracellular environment from myoblast cells during their differentiation into myotubes, as well as after mechanical strain. An in vivo analysis revealed that Gal-3 was triggered by trained exercise and was specifically produced by fast muscle fibers. Speculating a role for this peptide in the muscle-to-bone cross talk, a direct co-culture in vitro system, simultaneously combining media that were obtained from differentiated myoblasts and osteoblast cells, confirmed that Gal-3 is a mediator of osteoblast differentiation. Molecular and proteomic analyses revealed that the secreted Gal-3 modulated the biochemical processes occurring in the early phases of bone formation, in particular impairing the activity of the STAT3 and PDK1/Akt signaling pathways and, at the same time, triggering that one of Notch. Circulating Gal-3 also affected the expression of the most common factors involved in osteogenetic processes, including BMP-2, -6, and -7. Intriguingly, Gal-3 was able to interfere with the ability of differentiating osteoblasts to interact with the components of the extracellular bone matrix, a crucial condition required for a proper osteoblast differentiation. All in all, our evidence lays the foundation for further studies to present this lectin as a novel myokine involved in muscle-to-bone crosstalk.

Hydroxyapatite scaffolds obtained from the biomorphic transformation of wood are characterized from a fluid dynamic point of view. Such material of recent introduction offers great advantages for the in vitro study of bone cells, mostly in virtue of its peculiar porous structure. Determining the flow resistance and morphological parameters of these scaffolds is an essential step towards their practical use in bioreactors and microfluidic devices. To this aim, a series of tests involving a draining fluid are performed on a set of disc-shaped scaffolds, followed by the microscopy analysis of the pores visible on the sample faces. Contrarily to what expected, a temperature dependence is observed for the flow resistance, even after normalizing it by the fluid properties. The interpretation of the experimental results is assisted by numerical outcomes from Computational Fluid Dynamics modelling, which underline some limitations in the application of classical laws to the present problem. While the complex and variable internal structure of the scaffolds prevents the systematic use of simplified formulae, a correlation is found between the flow resistance and the pore geometry, which can facilitate the characterization of further samples.

The use of piezoelectric nanomaterials combined with ultrasound stimulation is emerging as a promising approach for wirelessly triggering the regeneration of different tissue types. However, it has never been explored for boosting chondrogenesis. Furthermore, the ultrasound stimulation parameters used are often not adequately controlled. In this study, we show that adipose-tissue-derived mesenchymal stromal cells embedded in a nanocomposite hydrogel containing piezoelectric barium titanate nanoparticles and graphene oxide nanoflakes and stimulated with ultrasound waves with precisely controlled parameters (1 MHz and 250 mW/cm2, for 5 min once every 2 days for 10 days) dramatically boost chondrogenic cell commitment in vitro. Moreover, fibrotic and catabolic factors are strongly down-modulated: proteomic analyses reveal that such stimulation influences biological processes involved in cytoskeleton and extracellular matrix organization, collagen fibril organization, and metabolic processes. The optimal stimulation regimen also has a considerable anti-inflammatory effect and keeps its ability to boost chondrogenesis in vitro, even in an inflammatory milieu. An analytical model to predict the voltage generated by piezoelectric nanoparticles invested by ultrasound waves is proposed, together with a computational tool that takes into consideration nanoparticle clustering within the cell vacuoles and predicts the electric field streamline distribution in the cell cytoplasm. The proposed nanocomposite hydrogel shows good injectability and adhesion to the cartilage tissue ex vivo, as well as excellent biocompatibility in vivo, according to ISO 10993. Future perspectives will involve preclinical testing of this paradigm for cartilage regeneration.

Dental implants are regularly employed in tooth replacement, the good clinical outcome of which is strictly correlated to the choice of an appropriate implant biomaterial. Titanium-based implants are considered the gold standard for rehabilitation of edentulous spaces. However, the insurgence of allergic reactions, cellular sensitization and low integration with dental and gingival tissues lead to poor osseointegration, affecting the implant stability in the bone and favoring infections and inflammatory processes in the peri-implant space. These failures pave the way to develop and improve new biocompatible implant materials. CERID dental implants are made of a titanium core embedded in a zirconium dioxide ceramic layer, ensuring absence of corrosion, a higher biological compatibility and a better bone deposition compared to titanium ones. We investigated hDPSCs’ biological behavior, i.e., cell adhesion, proliferation, morphology and osteogenic potential, when seeded on both CERID and titanium implants, before and after cleansing with two different procedures. SEM and AFM analysis of the surfaces showed that while CERID disks were not significantly affected by the cleansing system, titanium ones exhibited well-visible modifications after brush treatment, altering cell morphology. The proliferation rate of DPSCs was increased for titanium, while it remained unaltered for CERID. Both materials hold an intrinsic potential to promote osteogenic commitment of neuro-ectomesenchymal stromal cells. Interestingly, the CERID surface mitigated the immune response by inducing an upregulation of anti-inflammatory cytokine IL-10 on activated PBMCs when a pro-inflammatory microenvironment was established. Our in vitro results pave the way to further investigations aiming to corroborate the potential of CERID implants as suitable biomaterials for dental implant applications.

Introduction: In autoimmune diseases, particularly in systemic sclerosis and chronic periaortitis, a strict correlation between chronic inflammation and fibrosis exists. Since the currently used drugs prove mostly effective in suppressing inflammation, a better comprehension of the molecular mechanisms exerted by cell types implicated in fibro-inflammation is needed to develop novel therapeutic strategies. Mesenchymal stromal/stem cells (MSCs) are being matter of deep investigation to unveil their role in the evolution of fibrogenetic process. Several findings pointed out the controversial implication of MSCs in these events, with reports lining at a beneficial effect exerted by external MSCs and others highlighting a direct contribution of resident MSCs in fibrosis progression. Human dental pulp stem cells (hDPSCs) have demonstrated to hold promise as potential therapeutic tools due to their immunomodulatory properties, which strongly support their contribution to tissue regeneration. Methods: Our present study evaluated hDPSCs response to a fibro-inflammatory microenvironment, mimicked in vitro by a transwell co-culture system with human dermal fibroblasts, at early and late culture passages, in presence of TGF-β1, a master promoter of fibrogenesis. Results and Discussion: We observed that hDPSCs, exposed to acute fibro-inflammatory stimuli, promote a myofibroblast-to-lipofibroblast transition, likely based on BMP2 dependent pathways. Conversely, when a chronic fibro-inflammatory microenvironment is generated, hDPSCs reduce their anti-fibrotic effect and acquire a pro-fibrotic phenotype. These data provide the basis for further investigations on the response of hDPSCs to varying fibro-inflammatory conditions.

In the field of bone tissue engineering, particular interest is devoted to the development of 3D cultures to study bone cell proliferation under conditions similar to in vivo ones, e.g. by artificially producing mechanical stresses promoting a biological response (mechanotransduction). Of particular relevance in this context are the effects generated by the flow shear stress, which governs the nutrients delivery rate to the growing cells and which can be controlled in perfusion reactors. However, the introduction of 3D scaffolds complicates the direct measurement of the generated shear stress on the adhered cells inside the matrix, thus jeopardizing the potential of using multi-dimensional matrices. In this study, an anisotropic hydroxyapatite-based set of scaffolds is considered as a 3D biomimetic support for bone cells deposition and growth. Measurements of sample-specific flow resistance are carried out using a perfusion system, accompanied by a visual characterization of the material structure. From the obtained results, a subset of three samples is reproduced using 3D-Computational Fluid Dynamics (CFD) techniques and the models are validated by virtually replicating the flow resistance measurement. Once a good agreement is found, the analysis of flow-induced shear stress on the inner B-HA structure is carried out based on simulation results. Finally, a statistical analysis leads to a simplified expression to correlate the flow resistance with the entity and extensions of wall shear stress inside the scaffold. The study applies CFD to overcome the limitations of experiments, allowing for an advancement in multi-dimensional cell cultures by elucidating the flow conditions in 3D reactors.

Background Human dental pulp stem cells represent a mesenchymal stem cell niche localized in the perivascular area of dental pulp and are characterized by low immunogenicity and immunomodulatory/anti-inflammatory properties. Pericytes, mural cells surrounding the endothelium of small vessels, regulate numerous functions including vessel growth, stabilization and permeability. It is well established that pericytes have a tight cross talk with endothelial cells in neoangiogenesis and vessel stabilization, which are regulated by different factors, i.e., microenvironment and flow-dependent shear stress. The aim of this study was to evaluate the effects of a pulsatile unidirectional flow in the presence or not of an inflammatory microenvironment on the biological properties of pericyte-like cells isolated from human dental pulp (hDPSCs). Methods Human DPSCs were cultured under both static and dynamic conditions with or without pre-activated peripheral blood mononuclear cells (PBMCs). Pulsatile unidirectional flow shear stress was generated by using a specific peristaltic pump. The angiogenic potential and inflammatory properties of hDPSCs were evaluated through reverse phase protein microarrays (RPPA), confocal immunofluorescence and western blot analyses. Results Our data showed that hDPSCs expressed the typical endothelial markers, which were up-regulated after endothelial induction, and were able to form tube-like structures. RPPA analyses revealed that these properties were modulated when a pulsatile unidirectional flow shear stress was applied to hDPSCs. Stem cells also revealed a downregulation of the immune-modulatory molecule PD-L1, in parallel with an up-regulation of the pro-inflammatory molecule NF-kB. Immune-modulatory properties of hDPSCs were also reduced after culture under flow-dependent shear stress and exposure to an inflammatory microenvironment. This evidence was strengthened by the detection of up-regulated levels of expression of pro-inflammatory cytokines in PBMCs. Conclusions In conclusion, the application of a pulsatile unidirectional flow shear stress induced a modulation of immunomodulatory/inflammatory properties of dental pulp pericyte-like cells.

Bone substitute biomaterials (BSBs) represent a promising alternative to bone autografts, due to their biocompatibility, osteoconduction, slow resorption rates, and the ability to define and maintain volume for bone gain in dentistry. Many biomaterials are tailored to provide structural and biological support for bone regeneration, and allow the migration of bone-forming cells into the bone defect. Neural crest-derived stem cells isolated from human dental pulp (hDPSCs) represent a suitable stem cell source to study the biological effects of BSBs on osteoprogenitor cells involved in the physiological bone regenerative processes. This study aimed to evaluate how three different BSBs affect the stem cell properties, osteogenic differentiation, and inflammatory properties of hDPSCs. Our data highlight that BSBs do not alter cell proliferation and stemness markers expression, nor induce any inflammatory responses. Bone metabolism data show that hDPSCs exposed to the three BSBs distinctively secrete the factors supporting osteoblast activity and osteoclast activity. Our data indicate that (i) hDPSCs are a suitable stem cell source to study the effects of BSBs, and that (ii) the formulation of BSBs may condition the biological properties of stem cells, suggesting their versatile suitability to different dentistry applications.

Abstract Osteoarthritis implies a progressive degeneration of the whole joint. Cartilage is particularly affected, with inflammation playing a pivotal role1. In recent years, cartilage regeneration has been pursued through several bioengineering strategies and using different stem cell types2-6. Adipose -derived mesenchymal stromal cells (ASCs) constitute an intriguing and minimally invasive option. However, the use of ASCs for cartilage regeneration is hampered by a relatively inefficient expression of key chondrogenic markers7. Thus, new strategies to boost both in situ targeting and chondrogenesis of ASCs are highly desirable. Here we show that ASCs embedded in a nanocomposite hydrogel including piezoelectric nanomaterials and graphene oxide nanoflakes, and stimulated with ultrasound waves with precisely controlled parameters (1 MHz and 250 mW/cm2, for 5 min once every two days for a period of 10 days) dramatically boost cell chondrogenic commitment. Furthermore, this stimulation regimen also has a considerable anti-inflammatory effect. The proposed nanocomposite hydrogel also shows excellent biocompatibility in vivo. Our results show for the first time the chondrogenic potential of the combined piezoelectric nanoparticle-ultrasound stimulus; the proposed paradigm has the potential to trigger cartilage regeneration in osteoarthritis, focal cartilage defects and other pathological conditions involving cartilage lesions and degeneration. Future efforts should expand preclinical data, and target clinical applications of this therapeutic strategy.

This paper focuses on microfluidic devices, widely used in bioengineering. Their fabrication for research is almost entirely made of PDMS (a silicone), using photolithography and replica molding technologies, which involve many processing steps, sealed with a glass layer by plasma bonding. Our solution fabricates devices in just two steps, laser ablation of a glass layer, technology already extensively tested, and sealing with a commercial silicone layer by plasma bonding, drastically reducing skilled human operations and lead time. The paper describes the technologies with PDMS and with our solution, the design of a microfluidic test chip, the laser ablation and assessment by a confocal microscope of the microfluidic circuit in the glass layer of the chip, the plasma bonding of glass layers with PDMS and two other commercial silicones utilizing a grid of different plasma parameters, the qualitative assessment of the plasma bonding and choosing of a silicone as PDMS substitute, the extensive test on the bonding quality by two different pressure circuits on a batch of microfluidic chips realized with our proposed technology.

This study investigates the biological effects on a 3D scaffold based on hydroxyapatite cultured with MC3T3 osteoblasts in response to flow-induced shear stress (FSS). The scaffold adopted here (B-HA) derives from the biomorphic transformation of natural wood and its peculiar channel geometry mimics the porous structure of the bone. From the point of view of fluid dynamics, B-HA can be considered a network of micro-channels, intrinsically offering the advantages of a microfluidic system. This work, for the first time, offers a description of the fluid dynamic properties of the B-HA scaffold, which are strongly connected to its morphology. These features are necessary to determine the FSS ranges to be applied during in vitro studies to get physiologically relevant conditions. The selected ranges of FSS promoted the elongation of the attached cells along the flow direction and early osteogenic cell differentiation. These data confirmed the ability of B-HA to promote the differentiation process along osteogenic lineage. Hence, such a bioactive and naturally derived scaffold can be considered as a promising tool for bone regeneration applications.

Background Dental pulp stem cells (DPSCs) are low immunogenic and hold immunomodulatory properties that, along with their well-established multi-potency, might enhance their potential application in autoimmune and inflammatory diseases. The present study focused on the ability of DPSCs to modulate the inflammatory microenvironment through PD1/PD-L1 pathway. Methods Inflammatory microenvironment was created in vitro by the activation of T cells isolated from healthy donors and rheumatoid arthritis (RA) patients with anti-CD3 and anti-CD28 antibodies. Direct and indirect co-cultures between DPSCs and PBMCs were carried out to evaluate the activation of immunomodulatory checkpoints in DPSCs and the inflammatory pattern in PBMCs. Results Our data suggest that the inflammatory stimuli trigger DPSCs immunoregulatory functions that can be exerted by both direct and indirect contact. As demonstrated by using a selective PD-L1 inhibitor, DPSCs were able to activate compensatory pathways targeting to orchestrate the inflammatory process by modulating pro-inflammatory cytokines in pre-activated T lymphocytes. The involvement of PD-L1 mechanism was also observed in autologous inflammatory status (pulpitis) and after direct exposure to pre-activated T cells from RA patients suggesting that immunomodulatory/anti-inflammatory properties are strictly related to their stemness status. Conclusions Our findings point out that the communication with the inflammatory microenvironment is essential in licensing their immunomodulatory properties.

Dental implants are one of the most frequently used treatment options for tooth replacement, and titanium is the metal of choice due to its demonstrated superiority in resisting corrosion, lack of allergic reactions and mechanical strength. Surface roughness of titanium implants favors the osseointegration process; nevertheless, its topography may provide a suitable substrate for bacterial biofilm deposition, causing peri-implantitis and leading to implant failure. Subgingival prophylaxis treatments with cleansing powders aimed to remove the bacterial accumulation are under investigation. Two different air-polishing powders-glycine and tagatose-were assayed for their cleaning and antimicrobial potential against a Pseudomonas biofilm and for their effects on human dental pulp stem cells (hDPSCs), seeded on sandblasted titanium disks. Immunofluorescence analyses were carried out to evaluate cell adhesion, proliferation, stemness and osteogenic differentiation. The results demonstrate that both the powders have a great in vitro cleaning potential in the early period and do not show any negative effects during hDPSCs osteogenic differentiation process, suggesting their suitability for enhancing the biocompatibility of titanium implants. Our data suggest that the evaluated cleansing systems reduce microbial contamination and allow us to propose tagatose as an adequate alternative to the gold standard glycine for the air-polishing prophylaxis treatment.