Thermokinetic and Chemorheology of the Geopolymerization of an Alumina-Rich Alkaline-Activated Metakaolin in Isothermal and Dynamic Thermal Scans.

Alkaline sodium hydroxide/sodium silicate-activating high-purity metakaolin geopolymerization is described in terms of metakaolin deconstruction in tetrahedral hydrate silicate [O[Si(OH)]] and aluminate [Al(OH)] ionic precursors followed by their reassembling in linear and branched sialates monomers that randomly copolymerize into an irregular crosslinked aluminosilicate network. The novelty of the approach resides in the concurrent thermo-calorimetric (differential scanning calorimetry, DSC) and rheological (dynamic mechanical analysis, DMA) characterizations of the liquid slurry during the transformation into a gel and a structural glassy solid. Tests were run either in temperature scan (1 °C/min) or isothermal (20 °C, 30 °C, 40 °C) cure conditions.

Geopolymer Materials for Extrusion-Based 3D-Printing: A Review.

This paper examines how extrusion-based 3D-printing technology is evolving, utilising geopolymers (GPs) as sustainable inorganic aluminosilicate materials. Particularly, the current state of 3D-printing geopolymers is critically examined in this study from the perspectives of the production process, printability need, mix design, early-age material features, and sustainability, with an emphasis on the effects of various elements including the examination of the fresh and hardened properties of 3D-printed geopolymers, depending on the matrix composition, reinforcement type, curing process, and printing configuration. The differences and potential of two-part and one-part geopolymers are also analysed.

Bio-Resorption Control of Magnesium Alloy AZ31 Coated with High and Low Molecular Weight Polyethylene Oxide (PEO) Hydrogels.

Magnesium AZ31 alloy has been chosen as bio-resorbable temporary prosthetic implants to investigate the degradation processes in a simulating body fluid (SBF) of the bare metal and the ones coated with low and high-molecular-weight PEO hydrogels. Hydrogel coatings are proposed to control the bioresorption rate of AZ31 alloy. The alloy was preliminary hydrothermally treated to form a magnesium hydroxide layer.

Chemorheology of a Si/Al > 3 Alkali Activated Metakaolin Paste through Parallel Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA).

Although geopolymers, as structural materials, should have superior engineering properties than traditional cementitious materials, they often need to improve their final characteristics' reproducibility due to the need for more control of the complex silico-aluminate decomposition and polymerisation stages. Thermosetting of a reactive geopolymeric paste involves tetrahedral Silicate and Aluminate precursor condensation into polyfunctional oligomers of progressively higher molecular weight, transforming the initial liquid into a gel and a structural solid. Viscosity and gelation control become particularly critical when the geopolymer is processed with 3D printing additive technology.

Effects of different designs of orthodontic clear aligners on the maxillary central incisors in the tooth extraction cases: a biomechanical study.

Background: Controlling the 3D movement of central incisors during tooth extraction cases with clear aligners is important but challenging in invisible orthodontic treatment. This study aimed to explore the biomechanical effects of central incisors in tooth extraction cases with clear aligners under different power ridge design schemes and propose appropriate advice for orthodontic clinic.

Methods: A series of Finite Element models was constructed to simulate anterior teeth retraction or no retraction with different power ridge designs.

Geopolymer Materials for Bone Tissue Applications: Recent Advances and Future Perspectives.

With progress in the bone tissue engineering (BTE) field, there is an important need to develop innovative biomaterials to improve the bone healing process using reproducible, affordable, and low-environmental-impact alternative synthetic strategies. This review thoroughly examines geopolymers' state-of-the-art and current applications and their future perspectives for bone tissue applications. This paper aims to analyse the potential of geopolymer materials in biomedical applications by reviewing the recent literature.

Biomechanically Tunable Nano-Silica/P-HEMA Structural Hydrogels for Bone Scaffolding.

Innovative tissue engineering biomimetic hydrogels based on hydrophilic polymers have been investigated for their physical and mechanical properties. 5% to 25% by volume loading PHEMA-nanosilica glassy hybrid samples were equilibrated at 37 °C in aqueous physiological isotonic and hypotonic saline solutions (0.15 and 0.

Combined microcomputed tomography, biomechanical and histomorphometric analysis of the peri-implant bone: a pilot study in minipig model.

Objectives: To present a practical approach that combines biomechanical tests, microcomputed tomography (μCT) and histomorphometry, providing quantitative results on bone structure and mechanical properties in a minipig model, in order to investigate the specific response to an innovative dental biomaterial.

Methods: Titanium implants with innovative three-dimensional scaffolds were inserted in the tibias of 4 minipigs. Primary stability and osseointegration were investigated by means of insertion torque (IT) values, resonance frequency analysis (RFA), bone-to-implant contact (BIC), bone mineral density (BMD) and stereological measures of trabecular bone.

Direct restoration modalities of fractured central maxillary incisors: A multi-levels validated finite elements analysis with in vivo strain measurements.

Objective: To quantify the influence of fracture geometry and restorative materials rigidity on the stress intensity and distribution of restored fractured central maxillary incisors (CMI) with particular investigation of the adhesive interfaces. Ancillary objectives are to present an innovative technology to measure the in vivo strain state of sound maxillary incisors and to present the collected data.

Methods: A validation experimental biomechanics approach has been associated to finite element analysis.

Nonlinear visco-elastic finite element analysis of porcelain veneers: a submodelling approach to strain and stress distributions in adhesive and resin cement.

Purpose: To assess under load the biomechanical behavior of the cementing system of feldspathic vs alumina porcelain veneers.

Materials And Methods: A 3D model of a maxillary central incisor, the periodontal ligament (PDL) and the alveolar bone was generated. Incisors restored with alumina and feldspathic porcelain veneers were compared to a natural sound tooth.

The importance of cortical bone orthotropicity, maximum stiffness direction and thickness on the reliability of mandible numerical models.

Aim: To identify mechanical and geometrical variables affecting the biofidelity of numerical models of human mandible. Computed results sensibility to cortical bone orthotropy and thicknesses is investigated.

Methods: Two mandible numerical models of different bone complexities are setup.

Nonlinear visco-elastic finite element analysis of different porcelain veneers configuration.

This study is aimed at evaluating the biomechanical behavior of feldspathic versus alumina porcelain veneers. A 3D numerical model of a maxillary central incisor, with the periodontal ligament (PDL) and the alveolar bone was generated. Such model was made up of four main volumes: dentin, enamel, cement layer and veneer.

Non-linear elastic three-dimensional finite element analysis on the effect of endocrown material rigidity on alveolar bone remodeling process.

Objectives: In healthy conditions, modeling and remodeling collaborate to obtain a correct shape and function of bones. Loads on bones cause bone strains which generate signals that some cells can detect and respond to. Threshold ranges of such signals are genetically determined and are involved in the control of modeling and remodeling.

Non-linear viscoelastic finite element analysis of the effect of the length of glass fiber posts on the biomechanical behaviour of directly restored incisors and surrounding alveolar bone.

The study aimed at estimating the effect of insertion length of posts with composite restorations on stress and strain distributions in central incisors and surrounding bone. The typical, average geometries were generated in a FEA environment. Dentin was considered as an elastic orthotropic material, and periodontal ligament was coupled with nonlinear viscoelastic mechanical properties.

Biological response of human bone marrow stromal cells to sandblasted titanium nitride-coated implant surfaces.

Titanium nitride (TiN) coating has been proposed as an adjunctive surface treatment aimed to increase the physico-mechanical and aesthetic properties of dental implants. In this study we investigated the biological response of primary human bone marrow stromal cells (BMSC) to TiN-coated sandblasted (TiN-SB) compared to uncoated sandblasted (SB) surfaces. SB and TiN-SB disks were qualitatively and quantitatively analyzed by atomic force microscopy.

Three-dimensional finite element analysis of strain and stress distributions in endodontically treated maxillary central incisors restored with different post, core and crown materials.

Objectives: The present comparative analysis aimed at evaluating which combination of restorative materials resulted in the most homogeneous stress and strain distributions.

Methods: A three-dimensional finite element analysis was performed. All the nodes on the external surface of the root were constrained in all directions.

In vitro biological response to a light-cured composite when used for cementation of composite inlays.

Objective: To define the cytotoxicity of a photo-cured composite when used as a bonding system under a composite inlay.

Methods: Composite specimens were photo-cured with or without a 2 mm composite inlay interposed between them and the light source. Samples were extracted in complete cell culture medium and the obtained eluates applied to primary cultures of human pulp and gingival fibroblasts.

Influence of tooth preparation design on the stress distribution in maxillary central incisors restored by means of alumina porcelain veneers: a 3D-finite element analysis.

Aim: The present study aimed at providing 3D-FEA engineering tools for the understanding of the influence of tooth preparation design on the stress distribution and localization of critical sites in maxillary central incisors restored by means of alumina porcelain veneers under functional loading.

Methods: A 3D-FEM model of a maxillary central incisor is presented. An arbitrary chewing static force of 10 N was applied with an angulation of 60 and 125 degrees to the tooth longitudinal axis at the palatal surface of the crown.

3D FEA of cemented steel, glass and carbon posts in a maxillary incisor.

Objectives: A comparative study on the stress distribution in the dentine and cement layer of an endodontically treated maxillary incisor has been carried out by using Finite Element Analysis (FEA). The role of post and cement rigidity on reliability of endodontic restorations is discussed.

Methods: A 3D FEM model (13,272 elements and 15,152 nodes) of a central maxillary incisor is presented.

Inlay shading effect on the photopolymerization kinetic of a dental composite material used as bonding system in an indirect restoration technique.

Objectives: To define the inlay shading effect on the polymerization levels and kinetics of a light activated bonding system for an indirect restoration technique.

Materials And Methods: For the bonding system, an adhesive: Excite (Ivoclar-vivadent) and a composite: Z250 (3M-ESPE, St Paul Minnesota, USA) were investigated. A Demetron (Kerr USA) light curing unit was used.

Light shielding effect of overlaying resin composite on the photopolymerization cure kinetics of a resin composite and a dentin adhesive.

Objectives: The purpose of this study was to simultaneously determine the impact of exposure times and incremental resin composite overlaying thickness on the cure kinetics of a light activated composite and a dentin adhesive at selected depths of a simulated restoration.

Methods: Levels and kinetics of polymerization of a light activated resin composite (Z250, 3M-ESPE) and dentin adhesive (Excite, Ivoclar) cured with a halogen light unit (Demetron, Kerr, USA) operating at low/medium intensity (500 mW/cm2) for different exposure durations (20 and 60 s) were measured at selected depths (0.3, 0.

Development of hybrid materials based on hydroxyethylmethacrylate as supports for improving cell adhesion and proliferation.

A novel hydrogel based on 2-hydroxyethylmethacrylate and fumed silica nanoparticles is presented. The filler was mixed at increasing amount (3-40% w/w) to the organic monomer, before accomplish thermal polymerization. The hybrid composite materials obtained were characterized as far as concern the physical-chemical stability and sorption behaviour in water and water solutions.

Mandibular flexure and stress build-up in mandibular full-arch fixed prostheses supported by osseointegrated implants.

The biomechanical effect of mandibular functional flexure on stress build-up in implant-supported fixed restorations is discussed. The relative deformations and stress distributions in six different designs of implant-supported prosthetic systems (six or four implants, with or without distal cantilevers, cross-arch or midline-divided bar into two free-standing bridges) were analysed by a three-dimensional finite element (FE) model of a human edentulous mandible. A significant amount of stress in the more distal implants and the superstructure at the symphysis arises as a consequence of mandible functional flexure.