Publications by authors named "Petros Koidis"

62 Publications

The Use of Lasers in Dental Materials: A Review.

Materials (Basel) 2021 Jun 18;14(12). Epub 2021 Jun 18.

Department of Operative Dentistry, School of Dentistry, National and Kapodistrian University of Athens, 11527 Athens, Greece.

Lasers have been well integrated in clinical dentistry for the last two decades, providing clinical alternatives in the management of both soft and hard tissues with an expanding use in the field of dental materials. One of their main advantages is that they can deliver very low to very high concentrated power at an exact point on any substrate by all possible means. The aim of this review is to thoroughly analyze the use of lasers in the processing of dental materials and to enlighten the new trends in laser technology focused on dental material management. New approaches for the elaboration of dental materials that require high energy levels and delicate processing, such as metals, ceramics, and resins are provided, while time consuming laboratory procedures, such as cutting restorative materials, welding, and sintering are facilitated. In addition, surface characteristics of titanium alloys and high strength ceramics can be altered. Finally, the potential of lasers to increase the adhesion of zirconia ceramics to different substrates has been tested for all laser devices, including a new ultrafast generation of lasers.
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http://dx.doi.org/10.3390/ma14123370DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8234179PMC
June 2021

Biocompatibility assessment of resin-based cements on vascularized dentin/pulp tissue-engineered analogues.

Dent Mater 2021 05 7;37(5):914-927. Epub 2021 Mar 7.

Department of Prosthodontics, School of Dentistry, Faculty of Health Sciences, Aristotle University of Thessaloniki (AUTh), Thessaloniki, GR-54124, Greece. Electronic address:

Objectives: A three-dimensional (3D) dentin/pulp tissue analogue, resembling the human natural tissue has been engineered in an in vitro setup, aiming to assess the cytocompatibility of resin-based dental restorative cements.

Methods: Stem Cells from Apical Papilla (SCAP) and Human Umbilical Vein Endothelial Cells (HUVEC) were embedded in Collagen-I/Fibrin hydrogels at 1:3 ratio within 24-well plates. Hanging culture inserts were placed over the hydrogels, housing an odontoblast-like cell layer and a human treated-dentin barrier. Shear modulus of the hydrogels at 3.5 and 5 mg/ml was evaluated by dynamic mechanical analysis. Eluates of two resin-based cements, a dual-cure- (Breeze™, Pentron: Cement-1/C1), and a self-adhesive cement (SpeedCEMplus™, Ivoclar-Vivadent: Cement-2/C2) were applied into the dentin/pulp tissue analogue after pre-stimulation with LPS. Cytocompatibility was assessed by MTT assay, live/dead staining and real-time PCR analysis.

Results: Both hydrogel concentrations showed similar shear moduli to the natural pulp until day (D) 7, while the 5 mg/ml-hydrogel substantially increased stiffness by D14. Both cements caused no significant toxicity to the dentin/pulp tissue analogue. C1 induced stimulation (p < 0.01) of cell viability (158 ± 3%, 72 h), while pre-stimulation with LPS attenuated this effect. C2 (±LPS) caused minor reduction of viability (15-20%, 24 h) that recovered at 72 h for the LPS+ group. Both cements caused upregulation of VEGF, ANGP-1, and downregulation of the respective receptors VEGFR-2 and Tie-1.

Significance: Both resin-based cements showed good cytocompatibility and triggered angiogenic response within the dentin/pulp tissue analogue, indicating initiation of pulp repair responses to the released xenobiotics.
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http://dx.doi.org/10.1016/j.dental.2021.02.019DOI Listing
May 2021

Effect of in vitro aging and acidic storage on color, translucency, and contrast ratio of monolithic zirconia and lithium disilicate ceramics.

J Prosthet Dent 2021 Jan 24. Epub 2021 Jan 24.

Professor, Department of Prosthodontics, School of Dentistry, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece. Electronic address:

Statement Of Problem: How the translucency and color of ceramic restorations are affected by surface changes from the corrosive environment in the oral cavity and aging of materials is unclear.

Purpose: The purpose of this in vitro study was to compare the impact of acidic exposure and aging on the color and translucency of monolithic zirconia and lithium disilicate ceramics.

Material And Methods: Twenty computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic zirconia specimens and 20 pressed lithium disilicate specimens were fabricated. Half of the specimens of each group were aged in an autoclave (7.5 hours, 134 °C, 0.2 MPa), and the rest were immersed in hydrochloric acid to simulate the acidic conditions in the oral cavity from gastric reflux. The color coordinates L∗, a∗, and b∗ were measured with an ultraviolet spectrophotometer before and after aging or acidic storage. The translucency parameters and contrast ratios were calculated, and the CIEDE2000 color difference formula was used to determine color differences before and after each treatment. ANOVA and ANCOVA test models were used for data analysis (α=.05), while differences of color parameters in respect to acceptability and perceptibility thresholds were evaluated with the 1-sample t test (α=.05).

Results: Lithium disilicate presented a significantly higher translucency parameter and lower contrast ratio at baseline compared with monolithic zirconia specimens (P<.001). Acidic storage significantly impacted all parameters compared with aging, especially for the lithium disilicate group. Color differences were above the acceptability ΔΕ threshold for lithium disilicate after acidic storage (P=.001) and below for monolithic zirconia after acidic storage (P=.003).

Conclusions: The performance of lithium disilicate was slightly inferior compared with that of monolithic zirconia specimens, as they presented significant and clinically observable differences for the translucency parameter and ΔΕ after acidic storage and aging.
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http://dx.doi.org/10.1016/j.prosdent.2020.12.015DOI Listing
January 2021

Fracture strength of endodontically treated premolars restored with different post systems and metal-ceramic or monolithic zirconia crowns.

Dent Mater J 2021 May 15;40(3):606-614. Epub 2021 Jan 15.

Department of Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki.

The purpose of this study was to investigate the fracture strength of endodontically treated human maxillary premolars (ETP) restored with posts and metal ceramic (MC) or monolithic zirconia (MZ) crowns. Sixty ETP were randomly divided into 3 groups. Teeth in control group (C) received a resin filling. ETP in the MC group were restored with prefabricated metal posts, composite cores and MC crowns while in the MZ group with glass-fiber posts, composite cores and MZ crowns. Half of the specimens were loaded at a 135° angle and half under axial loading until fracture. The fracture modes were divided in repairable and irreparable using optical microscopy. Mean fracture strength was significantly higher for MC than for MZ crowns and control group only under axial loading. The distribution of repairable and irreparable failures presented no significant differences. Crown placement significantly improved the fracture strength of ETP irrespectively of post and crown type.
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http://dx.doi.org/10.4012/dmj.2020-223DOI Listing
May 2021

The effect of different aging protocols on the flexural strength and phase transformations of two monolithic zirconia ceramics.

J Appl Biomater Funct Mater 2020 Jan-Dec;18:2280800020982677

Laboratory of Prosthodontics, Dentistry Department, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece.

Introduction: The aim of the present study was to investigate how different aging protocols can affect the flexural strength and phase transformations of yttrium-stabilized zirconia ceramics (Y-TZP) for monolithic restorations.

Materials And Methods: Bar-shaped specimens from two zirconia ceramics bars were divided into three groups: a. no treatment (c), b. aging in an autoclave (a), and c. thermal cycling (t). The flexural strength was determined by the 3-point bending test and statistical analysis was performed to determine significant differences (< 0.05). Weibull statistics was used to analyze the dispersion of strength values while surface microstructural analysis was performed through X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM).

Results: Aging did not significantly affect the flexural strength but differences were recorded between the two groups, with group A presenting higher strength values and m-phase percentages.

Conclusions: The observed differences between the two ceramics could be attributed to variations in composition and processing.
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http://dx.doi.org/10.1177/2280800020982677DOI Listing
December 2020

Hybrid chitosan/gelatin/nanohydroxyapatite scaffolds promote odontogenic differentiation of dental pulp stem cells and in vitro biomineralization.

Dent Mater 2021 01 15;37(1):e23-e36. Epub 2020 Nov 15.

Department of Prosthodontics, School of Dentistry, Faculty of Health Sciences, Aristotle University of Thessaloniki (A.U.Th), Greece. Electronic address:

Objective: Hybrid chitosan/gelatin/nanohydroxyapatite (CS/Gel/nHA) scaffolds have attracted considerable interest in tissue engineering (TE) of mineralized tissues. The present study aimed to investigate the potential of CS/Gel/nHA scaffolds loaded with dental pulp stem cells (DPSCs) to induce odontogenic differentiation and in vitro biomineralization.

Methods: CS/Gel/nHA scaffolds were synthesized by freeze-drying, seeded with DPSCs, and characterized with flow cytometry. Scanning Electron Microscopy (SEM), live/dead staining, and MTT assays were used to evaluate cell morphology and viability; real-time PCR for odontogenesis-related gene expression analysis; SEM-EDS (Energy Dispersive X-ray spectroscopy), and X-ray Diffraction analysis (XRD) for structural and chemical characterization of the mineralized constructs, respectively.

Results: CS/Gel/nHA scaffolds supported viability and proliferation of DPSCs over 14 days in culture. Gene expression patterns indicated pronounced odontogenic shift of DPSCs, evidenced by upregulation of DSPP, BMP-2, ALP, and the transcription factors RunX2 and Osterix. SEM-EDS showed the production of a nanocrystalline mineralized matrix inside the cell-based and - to a lesser extent - the cell-free constructs, with a time-dependent production of net-like nanocrystals (appr. 25-30nm in diameter). XRD analysis gave the crystallite size (D=50nm) but could not distinguish between the initially incorporated and the biologically produced nHA.

Significance: This is the first study validating the potential of CS/Gel/nHA scaffolds to support viability and proliferation of DPSCs, and to provide a biomimetic microenvironment favoring odontogenic differentiation and in vitro biomineralization without the addition of any inductive factors, including dexamethasone and/or growth/morphogenetic factors. These results reveal a promising strategy towards TE of mineralized dental tissues.
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http://dx.doi.org/10.1016/j.dental.2020.09.021DOI Listing
January 2021

Advanced in Vitro Experimental Models for Tissue Engineering-based Reconstruction of a 3D Dentin/pulp Complex: a Literature Review.

Stem Cell Rev Rep 2021 Jun 3;17(3):785-802. Epub 2020 Nov 3.

Department of Prosthodontics, School of Dentistry, Faculty of Health Sciences, Aristotle University of Thessaloniki (A.U.Th), GR-54124, Thessaloniki, Greece.

Objective: Experimental procedures have been used to monitor cellular responses at the dentin/pulp interface. Aiming to divert from in vivo studies and oversimplified two-dimensional assays, three-dimensional (3D) models have been developed. This review provides an overview of existing literature, regarding 3D in vitro dentin/pulp reconstruction.

Material & Methods: PubMed, Scopus, Cochrane Library and Web of Science- were systematically searched for attributes between 1998 and 2020. The search focused on articles on the development of three-dimensional tools for the reconstruction of a dentin/pulp complex under in vitro conditions, which were then screened and qualitatively assessed. Article grouping according to mode of implementation, resulted in five categories: the customised cell perfusion chamber (CPC) (n = 8), the tooth bud model (TBM) (n = 3), the 3D dentin/pulp complex manufactured by tissue engineering (DPC) (n = 6), the entire tooth culture (ETC) (n = 4) and the tooth slice culture model (TSC) (n = 5).

Results: A total of 26 publications, applying nine and eight substances for pulp and dentin representation respectively, were included. Natural materials and dentin components were the most widely utilized. The most diverse category was the DPC, while the CPC group was the test with the highest longevity. The most consistent categories were the ETC and TSC models, while the TBM presented as the most complete de novo approach.

Conclusions: All studies presented with experimental protocols with potential upgrades. Solving the limitations of each category will provide a complete in vitro testing and monitoring tool of dental responses to exogenous inputs.

Clinical Relevance: The 3D dentin/pulp complexes are valid supplementary tools for in vivo studies and clinical testing. Graphical Abstract.
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http://dx.doi.org/10.1007/s12015-020-10069-8DOI Listing
June 2021

The Efficacy of Stem Cells Secretome Application in Osteoarthritis: A Systematic Review of In Vivo Studies.

Stem Cell Rev Rep 2020 12;16(6):1222-1241

Department of Prosthodontics, Faculty of Dentistry, Aristotle University of Thessaloniki, University Campus, Dentistry Building, GR-54124, Thessaloniki, Greece.

Purpose: Mesenchymal stem cells (MSCs) have appeared as a promising regenerative cell-based therapeutic, for degenerative conditions, such as OA, while the beneficial results from the application of MSCs have been attributed to the MSCs-derived secretome, which is the sum of cytoprotective factors produced by the MSCs. Aim of this study was to systematically review the literature in order to assess whether stem cell secretome (conditioned medium-CM, exosome-Exos or microvesicles-MV)(CM/Exos/MVs) treatment reduces inflammation and enhances cartilage regeneration in preclinical studies of experimental arthritis.

Materials And Methods: An extensive electronic search was conducted by 2 independent reviewers by using the PubMed, Cochrane Library, Web of Science, and Scopus database, as well as Google Scholar, in order to identify the studies that met our inclusion criteria until August 2019. Included studies were assessed for quality and Risk of Bias (RoB) using the ARRIVE (Animal Research: Reporting In Vivo Experiments) guidelines and a modification of Systematic Review Centre for Laboratory animal Experimentation (SYRCLE) RoB tool for animal studies, respectively.

Results: The initial search provided 525 records, with 28 fulfilling the inclusion criteria. The included studies presented great heterogeneity regarding the stem cells used, the preparation of therapeutic agent as well as the animal models used for testing. In addition, most studies presented with an unclear or high risk bias.

Conclusion: In summary, the positive results of CM/Exos/MVs application in preclinical models of experimentally induced OA in terms of resolution of inflammation and cartilage regeneration are highlighted in this review, presenting a promising therapeutic solution for OA.
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http://dx.doi.org/10.1007/s12015-020-09980-xDOI Listing
December 2020

Variables affecting the fit of zirconia fixed partial dentures: A systematic review.

J Prosthet Dent 2020 May 5;123(5):686-692.e8. Epub 2019 Nov 5.

Professor and Chairman, Department of Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.

Statement Of Problem: Different parameters affect the marginal and internal fit of zirconia fixed partial dentures (FPDs) on natural teeth. Determining a way to optimize these restorations is essential.

Purpose: The purpose of this systematic review was to determine the variables affecting the marginal fit and internal accuracy of zirconia FPDs on natural teeth.

Material And Methods: An electronic search was conducted by 2 independent reviewers by using the MEDLINE, Cochrane, Web of Science, and Scopus databases, as well as Google Scholar, for studies published up to July 2018, and a manual search was conducted from the reference lists of related articles. Eligibility criteria included articles in English published in peer-reviewed journals that assessed the marginal and/or internal adaptation of zirconia FPDs on teeth with 3 or more units, with at least 1 of the experimental groups being frameworks or FPDs fabricated from zirconia. Risk of bias was assessed with the aid of the Cochrane Handbook for Systematic Reviews of Interventions.

Results: The search provided 418 records, with 41 fulfilling the inclusion criteria. The selected studies showed considerable heterogeneity regarding materials, state of sintering, manufacturer and computer-aided design and computer-aided manufacturing (CAD-CAM) system, experimental methodology, sample size, and span length. Of the included articles, 36 were in vitro studies and 5 were clinical studies, most of which exhibited high-performance and detection biases. CAD-CAM systems provided more precise marginal and internal fit than CAM systems. An increase of framework span length to 6 or more units decreased both marginal and internal fit. The reported marginal gap tended to increase after the veneering process. The introduction of a conventional impression into an otherwise digital workflow seems to have a negative effect on the marginal fit.

Conclusions: The accuracy of zirconia FPDs or frameworks is considerably influenced by the processing procedure used and the choice of CAD-CAM system.
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http://dx.doi.org/10.1016/j.prosdent.2019.06.019DOI Listing
May 2020

Color alterations of a PMMA resin for fixed interim prostheses reinforced with silica nanoparticles.

J Adv Prosthodont 2019 Aug 27;11(4):193-201. Epub 2019 Aug 27.

Department of Prosthodontics, School of Dentistry, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece.

Purpose: The aim of the present study was to evaluate the color changes of an autopolymerizing PMMA resin used for interim fixed restorations, reinforced with SiO nanoparticles.

Materials And Methods: Silica nanoparticles were blended with the PMMA resin powder through high-energy ball milling. Four shades of PMMA resin were used (A3, B3, C3, D3) and total color differences were calculated through the equations ΔE= [(ΔL) + (Δa) + (Δb)] and . Statistically significant differences between ΔE and the clinically acceptable values of 3.3 and 2.7 and those between ΔE and the clinically acceptable value of 1.8 were evaluated with one sample t-test (<.05). Differences among the different shades were assessed through One-Way ANOVA and Bonferroni multiple comparison tests.

Results: Significantly lower values were detected for all groups concerning ΔE compared to the intraorally clinical acceptable values of 3.3 and 2.7. Significantly lower mean values were detected for groups B3, C3, and D3, concerning ΔE compared to the intraorally clinical acceptant value of 1.8. Color pigments in red-brown (A3) and red-grey (D3) shades affect the total color change to a greater extent after the reinforcement with SiO nanoparticles compared to the red-yellow (B3) shade.

Conclusion: Within the limitations of this in vitro study, it can be suggested that reinforcing PMMA with SiO nanoparticles at 0.25 wt% slightly affects the optical properties of the PMMA resin without being clinically perceivable.
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http://dx.doi.org/10.4047/jap.2019.11.4.193DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6718840PMC
August 2019

In vitro evaluation of the shear bond strength and bioactivity of a bioceramic cement for bonding monolithic zirconia.

J Prosthet Dent 2019 Aug 17;122(2):167.e1-167.e10. Epub 2019 Jul 17.

Professor and Head, Laboratory of Prosthodontics, Department of Dentistry, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece. Electronic address:

Statement Of Problem: Adhesive cementation is the most common bonding strategy for zirconia restorations. Although cementation with a bioactive luting agent has been proposed as an alternative, how the bond strength compares is unclear.

Purpose: The purpose of this in vitro study was to evaluate shear bond strength after cementing a monolithic zirconia ceramic to human dentin with a bioceramic cement, compare it with a traditional cement, and evaluate its bioactive properties.

Material And Methods: A total of 120 dentin specimens and 120 yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) (BruxZir) cylindrical specimens were used. Zirconia and dentin specimens were randomly divided into 8 study groups (n=15) based on 2 luting cement types (a bioceramic cement or glass ionomer cement as control), 2 airborne-particle abrasion protocols (50 μm or 110 μm), and 2 water storage durations (24 hours or 30 days). After the shear bond strength test using a universal machine at a crosshead speed of 1 mm/min, fracture patterns were evaluated under a stereomicroscope and a scanning electron microscope. Strength values were statistically analyzed with a 3-factor ANOVA model (α=.05). Bioactivity was evaluated in simulated body fluid (SBF).

Results: The control glass ionomer cement achieved significantly greater shear bond strength compared with the tested bioceramic cement. Mean bond strength values ranged from 2.52 MPa to 5.23 MPa for the bioceramic cement tested and from 4.20 MPa to 6.61 MPa for the control cement. The duration of water storage played a significant role in the bond strength, with groups stored for 30 days reaching higher bond strength values, whereas the particle size of airborne-particle abrasion did not have a significant effect. Failure types were primarily mixed. No apatite formation was recorded on the surface of the specimens even after 30 days of immersion in SBF.

Conclusions: The evaluated cement did not develop apatite in SBF, and its bond strength values were below the control glass ionomer cement.
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http://dx.doi.org/10.1016/j.prosdent.2019.04.016DOI Listing
August 2019

Assessment of cytotoxicity and antibacterial effects of silver nanoparticle-doped titanium alloy surfaces.

Dent Mater 2019 09 10;35(9):e220-e233. Epub 2019 Jul 10.

Department of Prosthodontics, School of Dentistry, Faculty of Health Sciences, Aristotle University of Thessaloniki (A.U.Th), Thessaloniki, Greece. Electronic address:

Objectives: This study aimed to develop silver nanoparticle (AgNP)-doped TiAlV alloy surfaces and investigate their antibacterial properties against representative periopathogens and potential cytotoxicity on osteoblastic cells.

Methods: AgNPs of different size distributions (5 and 30nm) were incorporated onto the TiAlV surfaces by electrochemical deposition, using colloid silver dispersions with increasing AgNP concentrations (100, 200 and 300ppm). The time-course silver release from the specimen surfaces to cell culture media was assessed by Atomic Absorption Spectroscopy (AAS). Cell attachment, viability and proliferation were investigated by SEM, live/dead staining MTT and BrdU assays. The antibacterial effects were assessed against P. gingivalis and P. intermedia by serial dilution spotting assays.

Results: A time- and concentration-dependent silver release from the experimental surfaces was observed. Overall, cell viability and attachment on the AgNP-doped surfaces, suggested adequate cytocompatibility at all concentrations. A transient cytotoxic effect was detected at 24h for the 5nm-sized groups that fully recovered at later time-points, while no cytotoxicity was observed for the 30nm-sized groups. A statistically significant, concentration-dependent decrease in cell proliferation rates was induced at 48h in all AgNP groups, followed by recovery at 72h in the groups coated with 5nm-sized AgNPs. A statistically significant, concentration-dependent antibacterial effect up to 30% was confirmed against both periopathogens.

Significance: This study sheds light to the optimal size-related concentrations of AgNP-doped TiAlV surfaces to achieve antibacterial effects, without subsequent cytotoxicity. These results significantly contribute to the development of antibacterial surfaces for application in oral implantology.
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http://dx.doi.org/10.1016/j.dental.2019.06.003DOI Listing
September 2019

Evaluation of the biological behaviour of various dental implant abutment materials on attachment and viability of human gingival fibroblasts.

Dent Mater 2019 07 3;35(7):1053-1063. Epub 2019 May 3.

Department of Prosthodontics, School of Dentistry, Faculty of Health Sciences, Aristotle University of Thessaloniki (A.U.Th), GR-54124, Thessaloniki, Greece. Electronic address:

Objective: This study aimed to investigate the biological effects of yttria-stabilized zirconia (Y-TZP) compared to other dental implant abutment materials, i.e. lithium disilicate (LS2) and titanium alloy (Ti), as well as the effects of aging of Y-TZP on viability/proliferation and attachment properties of Human Gingival Fibroblasts (HGFs).

Methods: Cylindrical specimens of each material were prepared as per manufacturer's instructions. Y-TZP specimens were divided into three groups: 1. no aging (Zr0), 2. aging for 5 h, 134 °C, 2 bars, 100% humidity (Zr5), 3. aging for 10 h under the same conditions (Zr10). Surface roughness was evaluated by optical profilometry; cell metabolic activity/viability by MTT assay, morphological changes by Scanning Electron Microscopy (SEM) and ratio of live/dead cells by confocal microscopy.

Results: Results showed statistically significant reduction of HGF metabolic activity/viability in contact with Y-TZP after aging. Nevertheless, non-aged zirconia showed no significant differences compared with LS2, Ti and control cultures. In contrast, significant stimulation of cell metabolic activity/viability was observed in HGFs exposed to LS2 eluates. Differential morphological patterns were observed for HGF in contact with different materials/treatments, with obviously increased number of dead cells and sparser distribution of HGFs cultured on Zr10 specimens. These effects were not correlated with surface topography, since Y-TZP aging did not alter surface micro-roughness.

Significance: These findings indicate that Y-TZP shows comparable biological properties to Ti and LS2 as implant abutment material. Nevertheless, Y-TZP aging might influence gingival cell attachment and proliferation properties, providing an alert to a potentially negative effect on the long-term maintenance of gingival architecture.
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http://dx.doi.org/10.1016/j.dental.2019.04.010DOI Listing
July 2019

Dental pulp stem cells in chitosan/gelatin scaffolds for enhanced orofacial bone regeneration.

Dent Mater 2019 02 7;35(2):310-327. Epub 2018 Dec 7.

Department of Materials Science and Technology, University of Crete, Heraklion, Greece; Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology Hellas (FORTH), Heraklion, Greece. Electronic address:

Objective: Biomimetic chitosan/gelatin (CS/Gel) scaffolds have attracted great interest in tissue engineering of several tissues. However, limited information exists regarding the potential of combining CS/Gel scaffolds with oral cells, such as dental pulp stem cells (DPSCs), to produce customized constructs targeting alveolar/orofacial bone reconstruction, which has been the aim of the present study.

Methods: Two scaffold types, designated as CS/Gel-0.1 and CS/Gel-1, were fabricated using 0.1 and 1% (v/v) respectively of the crosslinker glutaraldehyde (GTA). Scaffolds (n=240) were seeded with DPSCs with/without pre-exposure to recombinant human BMP-2. In vitro assessment included DPSCs characterization (flow cytometry), evaluation of viability/proliferation (live/dead staining, metabolic-based tests), osteo/odontogenic gene expression analysis (qRT-PCR) and structural/chemical characterization (scanning electron microscopy, SEM; energy dispersive X-ray spectroscopy, EDX; X-ray powder diffraction, XRD; thermogravimetry, TG). In vivo assessment included implantation of DPSC-seeded scaffolds in immunocompromised mice, followed by histology and SEM-EDX. Statistical analysis employed one/two-way ANOVA and Tukey's post-hoc tests (significance for p<0.05).

Results: Both scaffolds supported cell viability/proliferation over 14 days in culture, showing extensive formation of a hydroxyapatite-rich nanocrystalline calcium phosphate phase. Differential expression patterns indicated GTA concentration to significantly affect the expression of osteo/odontogenic genes, with CS/Gel-0.1 scaffolds being more effective in upregulating DSPP, IBSP and Osterix. In vivo analysis demonstrated time-dependent production of a nanocrystalline, mineralized matrix at 6, 8 and 10 weeks, being more prominent in constructs bearing rhBMP-2 pre-treated cells. The latter showed higher amounts of osteoid and fully mineralized bone, as well as empty space reduction.

Significance: These results reveal a promising strategy for orofacial bone tissue engineering.
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http://dx.doi.org/10.1016/j.dental.2018.11.025DOI Listing
February 2019

Evaluation of the micro-mechanical and bioactive properties of bioactive glass-dental porcelain composite.

J Mech Behav Biomed Mater 2018 10 26;86:77-83. Epub 2018 Jun 26.

School of Health Sciences, Dentistry Department, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece. Electronic address:

The aim of this study was to evaluate microhardness and elastic modulus of a novel sol-gel derived dental ceramic - 58S bioactive glass composite (BP67: Bioactive Glass:33.3%, Dental Ceramic:66.7%) BP67 material by micro-indentation and to investigate its microstructure and bioactivity. The research hypotheses were that the values of microhardness (1) and elastic modulus (2) of the novel bioceramic composite and the commercial dental ceramic will be of the same order. The experimental sol-gel derived ceramics showed similar microstructural characteristics to a commercial feldspathic porcelain, and presence of additional calcium phosphate phases, which contributed its bioactivity. The formation of an apatite-like layer on the materials' surface observed by Fourier Transform Infrared (FTIR) spectroscopy, X-ray Diffraction (XRD) and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) techniques after 12 days of maintenance in Conventional Simulated Body Fluid (cSBF) solution. The BP67 exhibited values of microhardness and modulus of elasticity which were not statistically significant different compared to dental ceramic, indicating the adequate mechanical integrity of the material. The results of this study suggest that the novel bioactive composite could be potentially applied in prosthetic dentistry, while its thermal and optical properties should be investigated in future studies.
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http://dx.doi.org/10.1016/j.jmbbm.2018.06.019DOI Listing
October 2018

Fibro/chondrogenic differentiation of dental stem cells into chitosan/alginate scaffolds towards temporomandibular joint disc regeneration.

J Mater Sci Mater Med 2018 Jun 26;29(7):97. Epub 2018 Jun 26.

Department of Prosthodontics, Faculty of Dentistry, Aristotle University of Thessaloniki, University Campus, Dentistry Building, 54124, Thessaloniki, Greece.

Tissue engineering (TE) may provide effective alternative treatment for challenging temporomandibular joint (TMJ) pathologies associated with disc malpositioning or degeneration and leading to severe masticatory dysfunction. Aim of this study was to evaluate the potential of chitosan/alginate (Ch/Alg) scaffolds to promote fibro/chondrogenic differentiation of dental pulp stem cells (DPSCs) and production of fibrocartilage tissue, serving as a replacement of the natural TMJ disc. Ch/Alg scaffolds were fabricated by crosslinking with CaCl2 combined or not with glutaraldehyde, resulting in two scaffold types that were physicochemically characterized, seeded with DPSCs or human nucleus pulposus cells (hNPCs) used as control and evaluated for cell attachment, viability, and proliferation. The DPSCs/scaffold constructs were incubated for up to 8 weeks and assessed for extracellular matrix production by means of histology, immunofluorescence, and thermomechanical analysis. Both Ch/Alg scaffold types with a mass ratio of 1:1 presented a gel-like structure with interconnected pores. Scaffolds supported cell adhesion and long-term viability/proliferation of DPSCs and hNPCs. DPSCs cultured into Ch/Alg scaffolds demonstrated a significant increase of gene expression of fibrocartilaginous markers (COLI, COL X, SOX9, COM, ACAN) after up to 3 weeks in culture. Dynamic thermomechanical analysis revealed that scaffolds loaded with DPSCs significantly increased storage modulus and elastic response compared to cell-free scaffolds, obtaining values similar to those of native TMJ disc. Histological data and immunochemical staining for aggrecan after 4 to 8 weeks indicated that the scaffolds support abundant fibrocartilaginous tissue formation, thus providing a promising strategy for TMJ disc TE-based replacement.
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http://dx.doi.org/10.1007/s10856-018-6109-6DOI Listing
June 2018

Stress generation in mandibular anterior teeth restored with different types of post-and-core at various levels of ferrule.

J Prosthet Dent 2018 Jun 15;119(6):965-974. Epub 2017 Nov 15.

Professor, Department of Fixed Prosthesis and Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece. Electronic address:

Statement Of Problem: Pertinent evidence regarding the mechanical integrity of mandibular anterior teeth restored with a post-and-core is limited.

Purpose: The purpose of this finite element analysis study was to compare the impact of the post type (glass fiber post-and-resin core or cast post-and-core) along with the ferrule effect on the stress fields generated in endodontically treated mandibular lateral incisors and canines.

Material And Methods: Three-dimensional models of the segmented mandible were developed. Mandibular incisors and canines with or without a 2-mm circular ferrule and restored with a cast post-and-core or glass fiber post-and-resin core were simulated and subjected to linear elastic static analysis. The principal stress values were calculated. von Mises equivalent stresses were used to evaluate the stress.

Results: Maximum principal stresses in dentin were highest in incisors, with a ferrule. Stress parameters in composite resin core in both incisors and canines were critically close to the tensile failure limit of the core material. Cast post-and-cores cemented in incisors without a ferrule accumulated the highest stresses, exceeding the tensile failure limit of resin-modified glass ionomer cement.

Conclusions: Tooth preparation with a ferrule led to a remarkable rise in stress in the dentin of mandibular incisors but favored the mechanical integrity of the restoration.
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http://dx.doi.org/10.1016/j.prosdent.2017.07.021DOI Listing
June 2018

Isolation and prolonged expansion of oral mesenchymal stem cells under clinical-grade, GMP-compliant conditions differentially affects "stemness" properties.

Stem Cell Res Ther 2017 Nov 2;8(1):247. Epub 2017 Nov 2.

Department of Conservative Dentistry, Periodontology and Preventive Dentistry, Hannover Medical School (MHH), Hannover, Germany.

Background: Development of clinical-grade cell preparations is central to meeting the regulatory requirements for cellular therapies under good manufacturing practice-compliant (cGMP) conditions. Since addition of animal serum in culture media may compromise safe and efficient expansion of mesenchymal stem cells (MSCs) for clinical use, this study aimed to investigate the potential of two serum/xeno-free, cGMP culture systems to maintain long-term "stemness" of oral MSCs (dental pulp stem cells (DPSCs) and alveolar bone marrow MSCs (aBMMSCs)), compared to conventional serum-based expansion.

Methods: DPSC and aBMMSC cultures (n = 6/cell type) were established from pulp and alveolar osseous biopsies respectively. Three culture systems were used: StemPro_MSC/SFM_XenoFree (Life Technologies); StemMacs_MSC/XF (Miltenyi Biotek); and α-MEM (Life Technologies) with 15% fetal bovine serum. Growth (population doublings (PDs)), immunophenotypic (flow cytometric analysis of MSC markers) and senescence (β-galactosidase (SA-β-gal) activity; telomere length) characteristics were determined during prolonged expansion. Gene expression patterns of osteogenic (ALP, BMP-2), adipogenic (LPL, PPAR-γ) and chondrogenic (ACAN, SOX-9) markers and maintenance of multilineage differentiation potential were determined by real-time PCR.

Results: Similar isolation efficiency and stable growth dynamics up to passage 10 were observed for DPSCs under all expansion conditions. aBMMSCs showed lower cumulative PDs compared to DPSCs, and when StemMacs was used substantial delays in cell proliferation were noted after passages 6-7. Serum/xeno-free expansion produced cultures with homogeneous spindle-shaped phenotypes, while serum-based expansion preserved differential heterogeneous characteristics of each MSC population. Prolonged expansion of both MSC types but in particular the serum/xeno-free-expanded aBMMSCs was associated with downregulation of CD146, CD105, Stro-1, SSEA-1 and SSEA-4, but not CD90, CD73 and CD49f, in parallel with an increase of SA-gal-positive cells, cell size and granularity and a decrease in telomere length. Expansion under both serum-free systems resulted in "osteogenic pre-disposition", evidenced by upregulation of osteogenic markers and elimination of chondrogenic and adipogenic markers, while serum-based expansion produced only minor changes. DPSCs retained a diminishing (CCM, StemPro) or increasing (StemMacs) mineralization potential with passaging, while aBMMSCs lost this potential after passages 6-7 under all expansion conditions.

Conclusions: These findings indicate there is still a vacant role for development of qualified protocols for clinical-grade expansion of oral MSCs; a key milestone achievement for translation of research from the bench to clinics.
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http://dx.doi.org/10.1186/s13287-017-0705-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5667471PMC
November 2017

Color stability of lithium disilicate ceramics after aging and immersion in common beverages.

J Prosthet Dent 2018 Apr 18;119(4):632-642. Epub 2017 Sep 18.

Professor, Department of Fixed Prosthesis & Implant Prosthodontics, Aristotle University of Thessaloniki, Thessaloniki, Greece. Electronic address:

Statement Of Problem: The color of an esthetic restoration and its color stability are important for long-term success. However, the impact of common beverages on lithium disilicate ceramic is not well known.

Purpose: The purpose of this in vitro study was to investigate color variations of lithium disilicate ceramics after thermocycling (TC) and immersion in commonly consumed beverages.

Material And Methods: A total of 288 specimens (1×10×10 mm) were fabricated from IPS e-max computer-aided design (CAD) (n=72), IPS e-max CERAM ([CER] n=72), IPS e-max Press with glazing ([PG] n=72), and IPS e-max Press without glazing ([PNG] n=72) according to the manufacturer's instructions. Each group was divided into 4 subgroups (n=18): TC, coffee, black tea, and red wine. Thermocycling was performed at 21 900 cycles at 5°C, 37°C, 55°C, and 37°C (3 years' clinical simulation), whereas the specimens were soaked in the staining solutions for up to 54 hours (3 years' clinical simulation). Color parameters L*, a*, and b* were assessed with an ultraviolet-visible spectroscopy recording spectrophotometer. Color difference (ΔE) was calculated using the equation [ΔΕ= [(ΔL*) + (Δa*) + (Δb*)]½]. Intraexaminer reliability was assessed by using the intraclass correlation coefficient. Two-way analysis of variance was used for the analysis of ΔΕ, and the parameters L*, a*, and b* were analyzed with linear mixed models for repeated measurements and the Bonferroni pair-wise comparison test (α=.05).

Results: Parameters ΔΕ, L*, a*, and b* were significantly affected by the interaction between material and treatment (P<.001). A ΔΕ >1 was recorded for PG with tea, wine, and coffee, PG after TC and CER after TC. For L*, greater reduction was observed for PNG with tea and CER after TC, whereas for a* significant changes were positive (to red shades), except for PNG with TC, where PNG with wine showed the greatest positive change. For b*, significant changes were negative (to blue shades) except for PNG with tea and coffee and CAD with tea.

Conclusions: All groups demonstrated color changes below the clinically perceptible level (ΔΕ<3.7), except PNG in tea which showed statistically significant color differences (ΔΕ>4). CAD presented higher color stability compared with the nonglazed Press specimens.
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http://dx.doi.org/10.1016/j.prosdent.2017.04.031DOI Listing
April 2018

Evaluation of color stability of preshaded and liquid-shaded monolithic zirconia.

J Prosthet Dent 2018 Mar 11;119(3):467-472. Epub 2017 Jul 11.

Professor, School of Health Sciences, Department of Dentistry, Section of Prosthodontics, Aristotle University of Thessaloniki, Thessaloniki, Greece. Electronic address:

Statement Of Problem: The effect of thermal aging on the color stability of monolithic zirconia has not been thoroughly investigated.

Purpose: The purpose of this in vitro study was to evaluate the color stability before and after thermocycling of monolithic zirconia specimens, which were either preshaded or characterized in the laboratory through the assessment of color parameters L*, a*, and b*.

Material And Methods: A total of 80 specimens (10×10×15 mm) were prepared from zirconia disks (BruxZir) and divided into 2 groups. The first group consisted of preshaded specimens from disks 100, 200, 300, and 400, and the second group consisted of white specimens characterized before the sintering stage with coloring liquids in shades A2, B2, C2, and D2. Ten specimens of each shade were used. A double-beam ultraviolet-visible light recording spectrophotometer was used to assess the color parameters L*, a*, and b* before and after thermocycling. The color difference ΔE was calculated based on ΔΕ=[(ΔL*)+(Δa*)+(Δb*)]. The reliability of the examiner was investigated by MedCalc v12.5 software, and the tests of normality, homogeneity of variances, and 1-way ANOVA statistical analysis of variance were performed by IBM Statistics SPSS v20.0 software (α=.05).

Results: No statistically significant ΔΕ (P>.05) was observed among the different groups after thermocycling. All ΔΕ values were below the limit of the 3.7 that an untrained observer can perceive. Only for the specimens in shades 200 and 400 was ΔΕ above 1, revealing a visible color difference, which, however, was still clinically acceptable. The L*, a*, and b* values for both liquid-shaded and preshaded zirconia specimens were not significantly affected by thermocycling. A higher color stability for laboratory-characterized compared with preshaded monolithic zirconia was observed irrespective of the color shade.

Conclusions: Within the limitations of this in vitro study, monolithic zirconia specimens of any shade, either preshaded or characterized in the laboratory, can be considered as color-stable materials after thermocycling.
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http://dx.doi.org/10.1016/j.prosdent.2017.04.015DOI Listing
March 2018

Psychopathologic Profiles of TMD Patients with Different Pain Locations.

Int J Prosthodont 2017 May/Jun;30(3):251-257

Purpose: The aim of this study was to examine whether psychopathologic profile is related to the location of pain in temporomandibular disorder (TMD) patients with myofascial and/or temporomandibular joint pain.

Materials And Methods: A total of 75 painful TMD patients (39 women and 36 men) participated in the study. Participants were divided into three groups (myogenous, arthrogenous, and mixed) using the Research Diagnostic Criteria for TMD (RDC/TMD) Axis I guidelines for assessment of TMD signs and symptoms. Three psychometric instruments were used to assess the psychopathologic profile of the TMD subgroups. Patients' state and trait anxiety were assessed using the State-Trait Anxiety Inventory (STAI-S, STAI-T), depression was measured with the Center for Epidemiological Studies Depression Scale (CES-D), and psychosocial functioning was evaluated using the Global Disability Scale (Glo.Di.S). The three TMD groups were compared with Kruskal-Wallis test followed by pairwise Mann-Whitney tests relative to the psychometric scores. Statistical analyses were performed with SPSS 15.0 software.

Results: No significant differences were detected among the different TMD groups in the three psychometric scales; STAI-T, CES-D, Glo.Di.S (P > .05). When the psychometric scale of state anxiety (STAI-S) was considered, significant differences were revealed between the myogenous and the arthrogenous pain groups (P = .008) and also between the mixed and the arthrogenous groups (P < .001).

Conclusion: These findings suggest that the psychopathologic profile is not related to the location of pain in TMD patients. However, anxiety was found to be higher in TMD patients with myogenous pain alone or combined with arthrogenous pain compared to those with only arthrogenous pain.
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http://dx.doi.org/10.11607/ijp.5155DOI Listing
July 2017

Oculo-Dento-Digital Dysplasia (ODDD) Due to a GJA1 Mutation: Report of a Case with Emphasis on Dental Manifestations.

Int J Prosthodont 2017 May/June;30(3):280–285. Epub 2017 Mar 20.

Oculo-dento-digital dysplasia (ODDD) is a congenital disorder manifesting with multiple phenotypic abnormalities involving the face, eyes, teeth, and limbs in addition to neurologic symptomatology. This report aims to present a female patient with ODDD who was referred due to extensive oral restorative needs. The presence of hypoplastic enamel triggered further evaluation. Characteristic facies with hypoplastic alae nasi and syndactyly offered greater insight into the phenotype of the syndrome. Clinical suspicion was confirmed by genetic sequencing revealing heterozygous mutation in GJA1. It is important to be aware of genetic disorders associated with characteristic dental malformations to offer appropriate counseling and treatment.
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http://dx.doi.org/10.11607/ijp.5130DOI Listing
July 2017

Reinforcement of a PMMA resin for interim fixed prostheses with silica nanoparticles.

J Mech Behav Biomed Mater 2017 05 9;69:213-222. Epub 2017 Jan 9.

School of Health Sciences, Department of Dentistry, Section of Prosthodontics, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece. Electronic address:

Purpose: Fractures in long span provisional/interim restorations are a common complication. Adequate fracture toughness is necessary to resist occlusal forces and crack propagation, so these restorations should be constructed with materials of improved mechanical properties. The aim of this study was to investigate the possible reinforcement of neat silica nanoparticles and trietoxyvinylsilane-modified silica nanoparticles in a PMMA resin for fixed interim restorations.

Materials And Methods: Composite PMMA-Silica nanoparticles powders were mixed with PMMA liquid and compact bar shaped specimens were fabricated according to the British standard BS EN ISO 127337:2005. The single-edge notched method was used to evaluate fracture toughness (three-point bending test), while the dynamic thermomechanical properties (Storage Modulus, Loss Modulus, tanδ) of a series of nanocomposites with different amounts of nanoparticles (0.25%, 0.50%, 0.75%, 1% w.t.) were evaluated. Statistical analysis was performed and the statistically significant level was set to p<0.05.

Results: The fracture toughness of all experimental composites was remarkably higher compared to control. There was a tendency to decrease of fracture toughness, by increasing the concentration of the filler. No statistically significant differences were detected among the modified/unmodified silica nanoparticles. Dynamic mechanical properties were also affected. By increasing the silica nanoparticles content an increase in Storage Modulus was recorded, while Glass Transition Temperature was shifted at higher temperatures.

Conclusions: Under the limitations of this in-vitro study, it can be suggested that both neat silica nanoparticles and trietoxyvinylsilane-modified silica nanoparticles, especially at low concentrations, may enhance the overall performance of fixed interim prostheses, as can effectively increase the fracture toughness, the elastic modulus and the Glass Transition Temperature of PMMA resins used in fixed provisional restorations.
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http://dx.doi.org/10.1016/j.jmbbm.2017.01.013DOI Listing
May 2017

An experimental bioactive dental ceramic for metal-ceramic restorations: Textural characteristics and investigation of the mechanical properties.

J Mech Behav Biomed Mater 2017 02 28;66:95-103. Epub 2016 Oct 28.

Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece. Electronic address:

The aim of this study was the evaluation of the textural characteristics of an experimental sol-gel derived feldspathic dental ceramic, which has already been proven bioactive and the investigation of its flexural strength through Weibull Statistical Analysis. The null hypothesis was that the flexural strength of the experimental and the commercial dental ceramic would be of the same order, resulting in a dental ceramic with apatite forming ability and adequate mechanical integrity. Although the flexural strength of the experimental ceramics was not statistically significant different compared to the commercial one, the amount of blind pores due to processing was greater. The textural characteristics of the experimental ceramic were in accordance with the standard low porosity levels reported for dental ceramics used for fixed prosthetic restorations. Feldspathic dental ceramics with typical textural characteristics and advanced mechanical properties as well as enhanced apatite forming ability can be synthesized through the sol-gel method.
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http://dx.doi.org/10.1016/j.jmbbm.2016.10.019DOI Listing
February 2017

Odontogenic differentiation and biomineralization potential of dental pulp stem cells inside Mg-based bioceramic scaffolds under low-level laser treatment.

Lasers Med Sci 2017 Jan 26;32(1):201-210. Epub 2016 Oct 26.

Department of Fixed Prosthesis and Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, GR-54124, Greece.

This study aimed to investigate the potential of low-level laser irradiation (LLLI) to promote odontogenic differentiation and biomineralization by dental pulp stem cells (DPSCs) seeded inside bioceramic scaffolds. Mg-based, Zn-doped bioceramic scaffolds, synthesized by the sol-gel technique, were spotted with DPSCs and exposed to LLLI at 660 nm with maximum output power of 140 mw at fluencies (a) 2 and 4 J/cm to evaluate cell viability/proliferation by the MTT assay and (b) 4 J/cm to evaluate cell differentiation, using real-time PCR (expression of odontogenic markers) and a p-nitrophenylphosphate (pNPP)-based assay for alkaline phosphatase (ALP) activity measurement. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were used for structural/chemical characterization of the regenerated tissues. Exposure of the DPSCs/scaffold complexes to the proposed LLLI scheme was associated with statistically significant increase of odontogenesis-related markers (bone morphogenetic protein 2 (BMP-2): 22.4-fold, dentin sialophosphoprotein (DSPP): 28.4-fold, Osterix: 18.5-fold, and Runt-related transcription factor 2 (Runx2): 3.4-fold). ALP activity was significantly increased at 3 and 7 days inside the irradiated compared to that in the non-irradiated SC/DPSC complexes, but gradually decreased until 14 days. Newly formed Ca-P tissue was formed on the SC/DPSC complexes after 28 days of culture that attained the characteristics of bioapatite. Overall, LLLI treatment proved to be beneficial for odontogenic differentiation and biomineralization of DPSCs inside the bioceramic scaffolds, making this therapeutic modality promising for targeted dentin engineering.
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http://dx.doi.org/10.1007/s10103-016-2102-9DOI Listing
January 2017

Inducing bioactivity of dental ceramic/bioactive glass composites by Nd:YAG laser.

Dent Mater 2016 11 24;32(11):e284-e296. Epub 2016 Sep 24.

Department of Fixed Prosthesis and Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece. Electronic address:

Objectives: Aims of this study were to investigate the optimal conditions of laser irradiation of a novel Bioactive Glass/Dental Ceramic-BP67 composite for acceleration of hydroxyapatite-HA formation and to assess cellular responses on the precipitated HA region.

Methods: BP67 (Bioactive Glass: 33.3%, Dental Ceramic: 66.7%) was fabricated by the sol-gel method. A laser assisted biomimetic-LAB process was applied to BP67 sintered specimens immersed in 1.5-times concentrated simulated body fluid-1.5×-SBF. The effect of various energy densities of pulsed nanosecond Nd-YAG (1064nm) laser and irradiation exposure times (30min, 1 and 3h) were evaluated for HA precipitation. The HA film was characterized by FTIR, XRD, SEM and micro Raman techniques. ICP-AES was used for revealing changes in chemical composition of the 1.5×-SBF during irradiation. Cell viability and morphological characteristics of periodontal ligament fibroblasts-PDLFs, human gingival fibroblasts-HGFs and SAOS-2 osteoblasts on the HA surface were evaluated by MTT assays and SEM.

Results: At optimal energy fluence of 1.52J/cm and irradiation time for 3h followed by immersion in 1.5×-SBF at 60°C, a dense HA layer was formed on laser-irradiated BP67 within 7 days. The resulting HA film was tightly bonded to the underlying substrate and had mineral composition similar to cementum. MTT assay showed a consistent reduction of cell proliferation on the HA layer in comparison to conventional control ceramic and BP67 for all 3 cell lines studied.

Significance: These findings suggest LAB is an effective method for acceleration of HA formation on materials with low bioactivity, while cellular responses need further investigation.
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http://dx.doi.org/10.1016/j.dental.2016.09.029DOI Listing
November 2016

Human treated dentin matrices combined with Zn-doped, Mg-based bioceramic scaffolds and human dental pulp stem cells towards targeted dentin regeneration.

Dent Mater 2016 08 11;32(8):e159-75. Epub 2016 Jun 11.

Department of Fixed Prosthesis & Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece. Electronic address:

Objective: This study aimed to investigate the potential of Mg-based bioceramic scaffolds combined with human treated-dentin matrices (hTDMs) and dentinogenesis-related morphogens to promote odontogenic differentiation and dentin-like tissue formation by Dental Pulp Stem Cells-DPSCs.

Methods: DPSC cultures were established and characterized by flow cytometry. Experimental cavities were prepared inside crowns of extracted teeth and demineralized by EDTA (hTDMs). Zn-doped, Mg-based bioceramic scaffolds, synthesized by the sol-gel technique, were hosted inside the hTDMs. DPSCs were spotted inside the hTDMs/scaffold constructs with/without additional exposure to DMP-1 or BMP-2 (100ng/ml, 24h). Scanning Electron Microscopy-SEM, live/dead fluorescence staining and MTT assay were used to evaluate cell attachment and viability; Real time PCR for expression of osteo/odontogenic markers; Inductively Coupled Plasma-Atomic Emission Spectrometry-ICP/AES for scaffold elemental release analysis; ELISA for hTDM growth factor release analysis; SEM and X-ray Diffraction-XRD for structural/chemical characterization of the regenerated tissues.

Results: Scaffolds constantly released low concentrations of Mg(2+), Ca(2+), Zn(2+) and Si(4+), while hTDMs growth factors, like DMP-1, BMP-2 and TGFβ-1. hTDMs/scaffold constructs supported DPSC viability, inducing their rapid odontogenic shift, indicated by upregulation of DSPP, BMP-2, osteocalcin and osterix expression. Newly-formed Ca-P tissue overspread the scaffolds partially transforming into bioapatite. Exposure to DMP-1 or BMP-2 pronouncedly enhanced odontogenic differentiation phenomena.

Significance: This is the first study to validate that combining the bioactivity and ion releasing properties of bioceramic materials with growth factor release by treated natural dentin further supported by exogenous addition of key dentinogenesis-related morphogens (DMP-1, BMP-2) can be a promising strategy for targeted dentin regeneration.
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http://dx.doi.org/10.1016/j.dental.2016.05.013DOI Listing
August 2016

Sol-Gel Derived Mg-Based Ceramic Scaffolds Doped with Zinc or Copper Ions: Preliminary Results on Their Synthesis, Characterization, and Biocompatibility.

Int J Biomater 2016 14;2016:3858301. Epub 2016 Feb 14.

Dentistry Department, Laboratory of Fixed Prosthesis and Implant Prosthodontics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.

Glass-ceramic scaffolds containing Mg have shown recently the potential to enhance the proliferation, differentiation, and biomineralization of stem cells in vitro, property that makes them promising candidates for dental tissue regeneration. An additional property of a scaffold aimed at dental tissue regeneration is to protect the regeneration process against oral bacteria penetration. In this respect, novel bioactive scaffolds containing Mg(2+) and Cu(2+) or Zn(2+), ions known for their antimicrobial properties, were synthesized by the foam replica technique and tested regarding their bioactive response in SBF, mechanical properties, degradation, and porosity. Finally their ability to support the attachment and long-term proliferation of Dental Pulp Stem Cells (DPSCs) was also evaluated. The results showed that conversely to their bioactive response in SBF solution, Zn-doped scaffolds proved to respond adequately regarding their mechanical strength and to be efficient regarding their biological response, in comparison to Cu-doped scaffolds, which makes them promising candidates for targeted dental stem cell odontogenic differentiation and calcified dental tissue engineering.
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http://dx.doi.org/10.1155/2016/3858301DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4769780PMC
March 2016

Is there a potential for durable adhesion to zirconia restorations? A systematic review.

J Prosthet Dent 2016 Jan 6;115(1):9-19. Epub 2015 Nov 6.

Professor and Chairman, Department of Fixed Prosthesis & Implant Prosthodontics Aristotle University of Thessaloniki, Thessaloniki, Greece. Electronic address:

Statement Of Problem: With a number of zirconia ceramic materials currently available for clinical use, an overview of the scientific literature on the adhesion methods and their potential influence is indicated.

Purpose: The purpose of this systematic review was to classify and analyze the existing methods and materials proposed to improve adhesion to zirconia surfaces.

Material And Methods: The current literature of in vitro studies examining the bond strength on zirconia ceramics, including clinical studies from 1998 until 2014, was analyzed. A search of the English language literature was undertaken using MEDLINE and PubMed, and a hand search was made for any relevant research paper from the library of a dental school. Papers evaluating only alumina restoration bond or ceramic-zirconia bond were excluded.

Results: A total of 134 publications were identified for analysis. Different adhesive techniques with different testing methods were reviewed. Results were difficult to compare in that the parameters varied in each research protocol.

Conclusions: Airborne-particle abrasion and tribochemical silica coating are reference pretreatment methods. Adhesive monomers are necessary for chemical bonding. Surface contamination and aging have negative effects on adhesion to zirconia. Many factors influence each combination of zirconia material, such as surface treatment, adhesive medium, and aging conditions. Laboratory studies should be confirmed by clinical trials.
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http://dx.doi.org/10.1016/j.prosdent.2015.09.008DOI Listing
January 2016

Relationship Between Sleep Bruxism and Stress Determined by Saliva Biomarkers.

Int J Prosthodont 2015 Sep-Oct;28(5):467-74

Purpose: The aim of this study was to evaluate the relationship between sleep bruxism (SB) and perceived stress through the estimation of stress-related biomarkers (cortisol, α-amylase) in saliva.

Materials And Methods: Forty-five volunteers (20 men, 25 women) participated in this study. Participants were divided into two groups (bruxers and nonbruxers) according to their answers in a standard bruxism assessment questionnaire outlined by the American Academy of Sleep Medicine. To confirm the preliminary diagnosis and to determine the severity of SB in the group of patients who had a positive self report for SB, a miniature, single-use electromyographic (EMG) device for SB detection (BiteStrip) was used. The perceived stress of the 45 participants was measured using the Perceived Stress Scale questionnaire. Unstimulated whole saliva was collected and levels of salivary cortisol and α-amylase were determined by enzyme-linked immunosorbent assay test and enzyme kinetic reaction, respectively. Nonparametric statistical methods were applied for data analyses.

Results: Bruxers showed higher levels of perceived stress than nonbruxers (P < .001). There was a moderate positive correlation between the 25 bruxers' BiteStrip scores and the salivary cortisol levels (Spearman rank correlation = 0.401, P = .047). Additionally, bruxers showed higher levels of cortisol than nonbruxers (P < .001). On the contrary, salivary α-amylase levels were not significantly different in bruxers and nonbruxers (P = .414).

Conclusions: These findings suggest that SB activity was related to higher levels of perceived psychological stress and salivary cortisol. Despite the limitations of the EMG recording device, a moderate positive correlation between BiteStrip score and cortisol levels was observed in bruxers.
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http://dx.doi.org/10.11607/ijp.4296DOI Listing
December 2015
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