Project description:The current study focuses on the fabrication of calcium hydroxyapatite (Ca10(PO4)6(OH)2) (HA) in a nanorange having whiskers- and cubic-shaped uniform particle morphology. The synthesized HA particles hold a promising feature as reinforcement fillers in dental acrylic resin composite. They increase the efficacy of reinforcement by length and aspect ratio, uniformity, and monodispersity. Therefore, the acrylic resin was reinforced with the as-synthesized monodispersed HA filler particles (0.2-1 Wt%). The presence of filler particles in the composite had a noticeable effect on the tribological and mechanical properties of the dental material. The morphological effect of HA particles on these properties was also investigated, revealing that cubic-shaped particles showed better results than whiskers. The as-fabricated composite (0.4 Wt%) of the cubic-shaped filler particles showed maximum hardness and improved antiwear/antifriction properties. Particle loading played its part in determining the optimum condition, whereas particle size also influenced the reinforcement efficiency. The current study revealed that particle morphology, particle size, uniformity, etc., of HA fillers, greatly influenced the tribological and mechanical properties of the acrylic resin-based nanocomposite. Improvement in the tribological properties of HA particle-reinforced acrylic resin composites (HA-acrylic resin) followed the trend as AR < CmC < WC < CC.
Project description:The performance of dental resin-based composites (RBCs) heavily depends on the characteristic properties of the individual filler fraction. As specific information regarding the properties of the filler fraction is often missing, the current study aims to characterize the filler fractions of several contemporary computer-aided design/computer-aided manufacturing (CAD/CAM) RBCs from a material science point of view. The filler fractions of seven commercially available CAD/CAM RBCs featuring different translucency variants were analysed using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), Micro-X-ray Computed Tomography (µXCT), Thermogravimetric Analysis (TG) and X-ray Diffractometry (XRD). All CAD/CAM RBCs investigated included midifill hybrid type filler fractions, and the size of the individual particles was clearly larger than the individual specifications of the manufacturer. The fillers in Shofu Block HC featured a sphericity of ≈0.8, while it was <0.7 in all other RBCs. All RBCs featured only X-ray amorphous phases. However, in Lava Ultimate, zircon crystals with low crystallinity were detected. In some CAD/CAM RBCs, inhomogeneities (X-ray opaque fillers or pores) with a size <80 µm were identified, but the effects were minor in relation to the total volume (<0.01 vol.%). The characteristic parameters of the filler fraction in RBCs are essential for the interpretation of the individual material's mechanical and optical properties.
Project description:The aim of this study was to evaluate the correlation between the percent of inorganic filler by weight (wt. %) and by volume (vol. %) of 11 flowable resin composites (FRCs) and their mechanical properties. To establish the correlation, the quantity of inorganic filler was determined by combustion and shape/size analyzed by SEM images. The compressive strength (CS), flexural strength (FS), and flexural modulus (FM) were determined. The CS values were between 182.87-310.38 MPa, the FS values ranged between 59.59 and 96.95 MPa, and the FM values were between 2.34 and 6.23 GPa. The percentage of inorganic filler registered values situated between 52.25 and 69.64 wt. % and 35.35 and 53.50 vol. %. There was a very good correlation between CS, FS, and FM vs. the inorganic filler by wt. % and vol. %. (R2 = 0.8899-0.9483). The highest regression was obtained for the FM values vs. vol. %. SEM images of the tested FRCs showed hybrid inorganic filler for Filtek Supreme XT (A3) and StarFlow (A2) and a homogeneous type of inorganic filler for the other investigated materials. All of the FS values were above 50 MPa, the ISO 4049/2019 limit for FRCs.
Project description:Dental resin composites (DRCs) are popular materials for repairing caries or dental defect, requiring excellent properties to cope with the complex oral environment. Filler/resin interface interaction has a significant impact on the physicochemical/biological properties and service life of DRCs. Various chemical and physical modification methods on filler/resin interface have been introduced and studied, and the physical micromechanical interlocking caused by the modification of fillers morphology and structure is a promising method. This paper firstly introduces the composition and development of DRCs, then reviews the chemical and physical modification methods of the filler/resin interface, mainly discusses the interface micromechanical interlocking structures and their enhancement mechanism for DRCs, finally give a summary on the existing problems and development potential.
Project description:Dental caries is one of the most prevalent human diseases resulting from tooth demineralization caused by acid production of bacteria plaque. It remains challenges for current practice to specifically identify, intervene and interrupt the development of caries while restoring defects. In this study, inspired by natural dental plaque, a stimuli-responsive multidrug delivery system (PMs@NaF-SAP) has been developed to prevent tooth decay and promote enamel restoration. Classic spherical core-shell structures of micelles dual-loaded with antibacterial and restorative agents are self-assembled into bacteria-responsive multidrug delivery system based on the pH-cleavable boronate ester bond, followed by conjugation with salivary-acquired peptide (SAP) to endow the nanoparticle with strong adhesion to tooth enamel. The constructed PMs@NaF-SAP specifically adheres to tooth, identifies cariogenic conditions and intelligently releases drugs at acidic pH, thereby providing antibacterial adhesion and cariogenic biofilm resistance, and restoring the microarchitecture and mechanical properties of demineralized teeth. Topical treatment with PMs@NaF-SAP effectively diminishes the onset and severity of caries without impacting oral microbiota diversity or surrounding mucosal tissues. These findings demonstrate this novel nanotherapy has potential as a promising biomedical application for caries prevention and tooth defect restoration while resisting biofilm-associated diseases in a controlled manner activated by pathological bacteria.
Project description:Background and Objectives: Resin composites represent a class of materials widely used in restorative dentistry due to patient demands for better aesthetics. Colour changes in composite resins can occur due to intrinsic and extrinsic factors. Beverages, such as vegetable juices, can be some of these extrinsic factors. The purpose of this study was to investigate the colour stability and modification of microhardness of two resin composites before and after immersion in different vegetable juices. Materials and Methods: The colour of two resin composite materials (Gradia Direct Anterior-shade A2 and Valux Plus-shade A2) was measured before and after immersion in four different solutions: distilled water (as control), beetroot, carrot, and tomato juice. Colour values (L *, a *, b *) were measured over a white background with a colorimeter, using the CIE L *a *b * system. Colour change values were calculated after 1, 3, 5, and 7 days of immersion. Microhardness measurements were taken before and after seven days immersion in test media. Repeated measures analysis of variance (ANOVA) and independent t-tests were applied for statistical analysis. Results: All vegetable juices produced statistically different discolouration after immersion for 7 days (p < 0.05). Tomato juice produced the most discolouration for the Gradia Direct specimens, whereas beetroot juice and carrot juice produced the most discolouration for the Valux Plus specimens. Microhardness of the materials immersed for 7 days in vegetable juices was reduced compared to the ones immersed in distilled water. Conclusions: Vegetable juices, immersion time, and dental resin composites are significant factors that may affect colour stability and microhardness of composite resins.
Project description:ObjectivesThe aim of this study was to modify the surface of fillers used in dental composites by the synthesis of two novel thiourethane oligomeric silanes, used to functionalize the silica-containing inorganic particles. Several thiourethane silane concentrations were tested during the silanization process to systematically assess the effect of silane coverage on experimental composite conversion, polymerization stress and fracture toughness.Materials and methodsTwo different thiourethane silanes were synthesized based either on 1,6-hexanediol-diissocynate (HDDI), or 1,3-bis(1-isocyanato-1-methylethyl) benzene (BDI). Conventional 3-(Trimethoxysilyl)propyl methacrylate was used as the control. Glass fillers were silanized with 1, 2 or 4 wt% of each thiourethane silane, then evaluated by thermogravimetrical analysis. Photopolymerizable resin composites were prepared with Bis-GMA/UDMA/TEGDMA and 50 wt% silanized glass filler. Polymerization kinetics and degree of conversion were tested using Near-IR. Bioman was used to test polymerization stress. Data were analyzed with two-way ANOVA/Tukey's test (α = 5%).ResultsThe mass of silane coupled to the filler increased with the concentrations of thiourethane in the silanizing solution, as expected. Thiourethane-containing groups exhibited significantly higher degree of conversion compared to control groups, except for BDI 4%. HDDI 4%, BDI 2% and BDI 4% showed significantly lower polymerization stress than control groups. HDDI 4% exhibited significantly higher fracture toughness.Conclusions and clinical significanceNovel filler functionalization with thiourethane silanes may be a promising alternative for improving dental composites properties by significantly increasing the degree of conversion, fracture toughness and reducing the polymerization stress.
Project description:Subgingival dental defects are common in clinical practice among patients with deep dental caries and dental fractures. These defects commonly accompany lesions involving marginal alveolar bone loss and gingival recession, and their clinical management is challenging. Restoring gingival adhesion and activating the regeneration of periodontal tissue are important for a better prognosis in these cases. However, there is no effective resin material for complex restorations involving the destruction of subgingival tissue. To achieve greater biocompatibility, resins are generally modified with bioactive particles that can release specific components. Surface prereacted glass ionomer (S-PRG) is a novel glass particle characterized by a three-layered structure and the release of multiple ions with bioactive potential. Therefore, in this study, we incorporated S-PRG filler into resin-based composites to investigate their effectiveness in the restoration of subgingival defects. Resin composites containing 0, 10, 30, 50, or 70 wt% S-RPG filler were fabricated and formed into material discs, where a commercial resin composite served as the control group. The microstructure and elemental distribution were characterized by scanning electronic microscopy and energy-dispersive spectroscopy. The resin composites containing 50 or 70 wt% S-PRG fillers exhibited comprehensively better physicochemical properties, including flexural modulus, compressive strength, and water sorption. The ion release profile and environmental pH of the resins were measured with material extracts. Periodontal ligament stem cells were considered as seed cells that harbored great potential for periodontal regeneration. Cellular experiments suggested that S-PRG promotes cell proliferation and adhesion, induces cell migration, and stimulates vascularized osteogenesis. The feasibility of using S-PRG-containing resin composite to rectify subgingival dental defects was confirmed in vivo. After restoration with the S-PRG-filled resin material, intact epithelial tissue adhered to the resin surface with no visible inflammation. In conclusion, S-PRG-filled resin composites showed some biocompatibility as an alternative material for clinical applications.
Project description:Novel metal matrix composites (MMCs) have been fabricated with Ti6Al4V matrix and a biogenic ceramic filler in the form of diatomaceous earth (DE). Mixtures of DE and Ti6Al4V powders were consolidated by the spark plasma sintering (SPS) method. Microstructure of the consolidated samples has been investigated with microscopic techniques and XRD. Thermomechanical characteristics have been obtained using small-sample techniques. The results obtained indicate that the fabricated composites show outstanding mechanical and thermal properties due to synergic effects between the filler and the matrix (beyond the rule of mixtures).
Project description:The method of measuring electrical volume resistivity in different directions was applied to characterize the filler orientation in melt mixed polymer composites containing different carbon fillers. For this purpose, various kinds of fillers with different geometries and aspect ratios were selected, namely carbon black (CB), graphite (G) and expanded graphite (EG), branched multiwalled carbon nanotubes (b-MWCNTs), non-branched multiwalled carbon nanotubes (MWCNTs), and single-walled carbon nanotubes (SWCNTs). As it is well known that the shaping process also plays an important role in the achieved electrical properties, this study compares results for compression molded plates with random filler orientations in the plane as well as extruded films, which have, moreover, conductivity differences between extrusion direction and perpendicular to the plane. Additionally, the polymer matrix type (poly (vinylidene fluoride) (PVDF), acrylonitrile butadiene styrene (ABS), polyamide 6 (PA6)) and filler concentration were varied. For the electrical measurements, a device able to measure the electrical conductivity in two directions was developed and constructed. The filler orientation was analyzed using the ratio σin/th calculated as in-plane conductivity σin-plane (σin) divided by through-plane conductivity σthrough-plane (σth). The ratio σin/th is expected to increase with more pronounced filler orientation in the processing direction. In the extruded films, alignment within the plane was assigned by dividing the in-plane conductivity in the extrusion direction (x) by the in-plane conductivity perpendicular to the extrusion direction (y). The conductivity ratios depend on filler type and concentration and are higher the higher the filler aspect ratio and the closer the filler content is to the percolation concentration.