Zirconia Hybrid Dental Implants Influence the Biological Properties of Neural Crest-Derived Mesenchymal Stromal Cells.

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.

Evaluation of Antimicrobial Effect of Air-Polishing Treatments and Their Influence on Human Dental Pulp Stem Cells Seeded on Titanium Disks.

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.

Evaluation of Biological Response of STRO-1/c-Kit Enriched Human Dental Pulp Stem Cells to Titanium Surfaces Treated with Two Different Cleaning Systems.

Peri-implantitis-an infection caused by bacterial deposition of biofilm-is a common complication in dentistry which may lead to implant loss. Several decontamination procedures have been investigated to identify the optimal approach being capable to remove the bacterial biofilm without modifying the implant surface properties. Our study evaluated whether two different systems-Ni-Ti Brushes (Brush) and Air-Polishing with 40 µm bicarbonate powder (Bic40)-might alter the physical/chemical features of two different titanium surfaces-machined (MCH) and Ca++ nanostructured (NCA)-and whether these decontamination systems may affect the biological properties of human STRO-1+/c-Kit+ dental pulp stem cells (hDPSCs) as well as the bacterial ability to produce biofilm. Cell morphology, proliferation and stemness markers were analysed in hDPSCs grown on both surfaces, before and after the decontamination treatments. Our findings highlighted that Bic40 treatment either maintained the surface characteristics of both implants and allowed hDPSCs to proliferate and preserve their stemness properties. Moreover, Bic40 treatment proved effective in removing bacterial biofilm from both titanium surfaces and consistently limited the biofilm re-growth. In conclusion, our data suggest that Bic40 treatment may operatively clean smooth and rough surfaces without altering their properties and, consequently, offer favourable conditions for reparative cells to hold their biological properties.

Titanium Surface Properties Influence the Biological Activity and FasL Expression of Craniofacial Stromal Cells.

Mesenchymal stromal cells (MSCs) can be easily isolated form craniofacial bones during routine dentistry procedures. Due to their embryological origin from neural crest, they represent a suitable cell population to study cell-biomaterial interaction in the craniofacial field, including osteoinductive/osteointegrative processes. The biological and immunomodulatory properties of MSCs may be influenced by chemistry and topography of implant surfaces. We investigated if and how three different titanium surfaces, machined (MCH), sandblasted with resorbable blasting medium (RBM), and Ca++-nanostructured (NCA), may affect biological activity, osseointegration, and immunomodulatory properties of craniofacial MSCs. Cell proliferation, morphology, osteogenic markers, and FasL were evaluated on MSCs isolated from the mandibular bone after seeding on these three different surfaces. No statistically significant differences in cell proliferation were observed whereas different morphologies and growth patterns were detected for each type of surface. No difference in the expression of osteogenic markers was revealed. Interestingly, FasL expression, involved in the immunomodulatory activity of stem cells, was influenced by surface properties. Particularly, immunofluorescence analysis indicated that FasL expression increased on MCH surface compared to the others confirming the suggested role of FasL in promoting osteogenic differentiation. Titanium surface treatments and topography might reflect different biological behaviours of craniofacial MSCs and influence their osseointegration/immunomodulation properties.

Plaque accumulation on titanium disks with different surface treatments: an in vivo investigation.

Implants with rough surfaces are today widely used. It has been speculated that rough surfaces (Ra > 0.2 µm) provide a better "substrate" for retention and accumulation of plaque in terms of area, thickness and colony-forming unit that can eventually lead to peri mucositis and/or peri-implantitis. The aim of this investigation was to evaluate in vivo the plaque accumulation after 48 h on three implant surfaces with different treatments. For this investigation, we used 21 sterilized titanium disks, with a diameter of 8mm and a thickness of 3 mm, provided by the manufacturer: 7 with machined surface, as smooth control, 7 with HA grit sandblasted RBM surface and 7 with Ca++ incorporated in titanium Xpeed surface. One disk for each surface treatment was characterized at time 0 by SEM and AFM to study, respectively, the surface morphology and roughness. The other 18 disks were mounted randomly on three upper acrylic bites in a buccal lateral position, worn for 48 h by three volunteer students for plaque accumulation. After 48 h each disk was removed and analyzed qualitatively and quantitatively by an independent operator, not involved into the study, in order to avoid bias. Data collected were statistically analyzed by one-way ANOVA. The qualitative analysis showed no differences in terms of total plaque accumulation between the surfaces. Data from quantitative analysis using Anova Test showed no significance between all groups. In this in vivo investigation all the surfaces studied promoted plaque formation. The degree of surface roughness seems not to be a critical factor for plaque accumulation.

In vitro and in vivo osteoinductive and osteoconductive properties of a synthetic bone substitute.

PURPOSE: The present study tested a recently introduced bone substitute material (BSM) with a novel structure to determine its osteoinductive and osteoconductive properties in vitro and in vivo. The specific aims were to determine the microstructure of the as-manufactured BSM, as analyzed with scanning electron microscopy, and to characterize different cellular interactions. MATERIALS AND METHODS: Human bone marrow stromal cells were cultured in the presence of the BSM. In vitro, attachment of osteoblastlike cells (SAOS-2) to the BSM was observed with the scanning electron microscope. The expression of genes related to osteogenic differentiation (alkaline phosphatase, bone sialoprotein, type I collagen, and osteocalcin) was determined by reverse-transcriptase polymerase chain reaction. In vivo, bone formation was examined with a murine model of ectopic bone formation through histology and computed tomographic scanning by using tissue-engineered constructs with the BSM and ovine bone marrow stromal cells. RESULTS: Early cellular attachment could be detected as early as 6 hours. Cellular morphology developed in the following 66 hours toward a starlike appearance. Human bone marrow stromal cells cultured in the presence of the BSM showed no reduction in their viability. Osteocalcin was up-regulated during cell culturing, demonstrating an osteoinductive effect of BSM. Histologic and computed tomographic analyses showed the formation of new bone surrounding BSM particles, and a vascular meshwork was observed in the porosity of the particles. CONCLUSION: The analyzed bone substitute of synthetic origin presented osteoinductive properties that may exert a differentiative stimulus upon osteoprogenitor cells. The tested material allowed cellular adhesion of osteoblastlike cells and, following tissue construct implantation in vivo, supported the formation of new bone.

Shock absorption capacity of restorative materials for dental implant prostheses: an in vitro study.

PURPOSE: To measure the vertical occlusal forces transmitted through crowns made of different restorative materials onto simulated peri-implant bone. MATERIALS AND METHODS: The study was conducted using a masticatory robot that is able to reproduce the mandibular movements and forces exerted during mastication. During robot mastication, the forces transmitted onto the simulated peri-implant bone were recorded using nine different restorative materials for the simulated single crown: zirconia, two glass-ceramics, a gold alloy, three composite resins, and two acrylic resins. Three identical sample crowns for each material were used. Each crown was placed under 100 masticatory cycles, occluding with the flat upper surface of the robot to evaluate the vertical forces transmitted. Two-way analysis of variance was used. Alpha was set at .05. RESULTS: The statistical evaluation of the force peaks recorded on the vertical z-axis showed mean values of 641.8 N for zirconia; 484.5 N and 344.5 N, respectively, for the two glass-ceramics; 344.8 N for gold alloy; 293.6 N, 236 N, and 187.4 N, respectively, for the three composite resins; and 39.3 N and 28.3 N, respectively, for the two acrylic resins. Significant differences were found between materials (P < .0001), except for the comparison between gold alloy and one of the glass-ceramics. CONCLUSION: Composite and above all acrylic resin crowns were more able to absorb shock from occlusal forces than crowns made of zirconia, ceramic material, or gold alloy.

The role of surface implant treatments on the biological behavior of SaOS-2 osteoblast-like cells. An in vitro comparative study.

OBJECTIVES: The aim of this study was an in vitro comparison of osteoblast adhesion, proliferation and differentiation related to six dental implants with different surface characteristics, and to determine if the interaction between cells and implant is influenced by surface structure and chemical composition. MATERIAL AND METHODS: Six types of implants were tested, presenting four different surface treatments: turned, sandblasted, acid-etched, anodized. The implant macro- and microstructure were analyzed using SEM, and the surface chemical composition was investigated using energy-dispersive X-ray analysis. SaOS-2 osteoblasts were used for the evaluation of cell adhesion and proliferation by SEM, and cell viability in contact with the various surfaces was determined using cytotoxicity MTT assays. Alkaline phosphatase (ALP) enzymatic activity in contact with the six surfaces was evaluated. Data relative to MTT assay and ALP activity were statistically analyzed using Kruskal-Wallis not parametric test and Nemenyi-Damico-Wolfe-Dunn post hoc test. RESULTS: All the implants tested supported cell adhesion, proliferation and differentiation, revealing neither organic contaminants nor cytotoxicity effects. The industrial treatments investigated changed the implant surface microscopic aspect and SaOS-2 cell morphology appeared to be influenced by the type of surface treatment at 6, 24, and 72 h of growth. SaOS-2 cells spread more rapidly on sandblasted surfaces. Turned surfaces showed the lowest cell proliferation at SEM observation. Sandblasted surfaces showed the greatest ALP activity values per cell, followed by turned surfaces (P < 0.05). CONCLUSIONS: On the base of this in vitro investigation, differently surfaced implants affected osteoblast morphology, adhesion, proliferation, and differentiation. Sandblasted surfaces promoted the most suitable osteoblast behavior.

Graft materials and bone marrow stromal cells in bone tissue engineering.

Bone augmentation procedures rely on osteogenic/osteoconductive properties of bone graft material (BGM). A further improvement is represented by use of autologous bone marrow stromal cells (BMSC), expanded in vitro and seeded on BGM before implantation in the bone defect. The effect of different BGMs on BMSC osteogenic differentiation was evaluated. BMSC were cultured in vitro in the presence of different BGM (natural, synthetic, and mixed origins). Cellular morphology was analyzed with scanning electron microscopy. The capability of BMSC to differentiate was determined in vitro by alkaline phosphatase gene expression and enzyme activity at different time points (7, 14, and 28 days) and in vivo by ectopic bone formation of implanted tissue constructs in an immunodeficient murine model. BGM supports the cell adhesion and osteogenic differentiation of BMSC developing a useful tool in the bone tissue engineering.

Cell behavior related to implant surfaces with different microstructure and chemical composition: an in vitro analysis.

PURPOSE: This paper reports on an in vitro comparison of osteoblast and mesenchymal stem cell (MSC) adhesion, proliferation, and differentiation related to two different surface treatments applied to the same implant design to determine whether the interaction between cells and implants is influenced by surface structure and chemical composition of the implants. MATERIALS AND METHODS: Thirty-nine implants with a sandblasted (SB) surface and 39 implants with a grit-blasted and high-temperature acid-etched (GBAE) surface were used. The implant macrostructures and microstructures were analyzed by high- and low-voltage scanning electron microscopy (SEM) and by stereo-SEM. The surface chemical composition was investigated by energy dispersive analysis and x-ray photoemission spectroscopy. SaOS-2 osteoblasts and human MSCs were used for the evaluation of cell proliferation and alkaline phosphatase enzymatic activity in contact with the two surfaces. RESULTS: The GBAE surface showed fewer contaminants and a very high percentage of titanium (19.7%) compared to the SB surface (14.2%). The two surfaces showed similar mean roughness (Ra), but the depth (Rz) and density (RSm) of the porosity were significantly increased in the GBAE surface. The GBAE surface presented more osteoblast and MSC proliferation than the SB surface. No statistically significant differences in alkaline phosphatase activity were found between surfaces for either cellular line. CONCLUSIONS: The GBAE surface showed less surface contaminants and a higher percentage of titanium (19.7%) than the SB surface. The macro/micropore structured design and chemical composition of the GBAE surface allowed greater cell adhesion and proliferation and an earlier cell spreading but did not play an obvious role in in vitro cellular differentiation.

The use of a masticatory robot to analyze the shock absorption capacity of different restorative materials for prosthetic implants: a preliminary report.

PURPOSE: This study was conducted to measure, in vitro, the chewing load forces transmitted through crowns made of different prosthetic restorative materials onto dental implants. MATERIALS AND METHODS: A masticatory robot capable of reproducing the mandibular movements and the forces exerted during chewing was used. The forces transmitted to the simulated peri-implant bone during the robot mastication were analyzed using four different occlusal materials: three resin composites and one glass ceramic crown. RESULTS: The ceramic crowns transmitted significantly greater forces (up to +63.06%, P < .0001) than the composite crowns tested. CONCLUSION: Composite crowns are better able to absorb shock from occlusal forces than crowns made of ceramic material.

Robotic chewing simulator for dental materials testing on a sensor-equipped implant setup.

PURPOSE: This study describes a mechanical chewing simulator that is able to reproduce mandibular movements in 3 dimensions and the forces exerted during mastication. The aim of this work was to validate the described device, which can be used to test the ability of different restorative materials to withstand stress. MATERIALS AND METHODS: To validate the masticatory robot, 5 identical samples for each of 3 different restorative materials (an acrylic resin, a composite resin, and a glass ceramic) were created. Each sample underwent 5 minutes of chewing in the robot. The forces transmitted to the simulated peri-implant bone were collected. Two-way analysis of variance was used to evaluate the results. RESULTS: There were significant differences between the materials, and internal comparisons also showed significant differences (P < .0001). CONCLUSION: The different elastic moduli of the restorative materials significantly affected stress transmission at the simulated bone-implant interface, and the masticatory robot was able to identify this difference. The very low levels of variation confirm the precision of the machine during data collection and validate the reliability of the method, showing effective repeatability of the tests.