The aim of the present study was to investigate the effects of low-temperature aging on the micro-mechanical and micro-structural properties of zirconia-porcelain interface. In total, thirty-three Y-TZP zirconia blocks were fabricated by using CAD/CAM technology, veneered with porcelains. Specimens were submitted to low-temperature aging in an autoclave at 134 °C, additional 0.2 MPa pressure for 0 h, 5 h, or 10 h. Flexural strength was obtained by using three-point bending test. Micro-mechanical properties (nano-hardness (H) and reduced modulus (Er)) were investigated by nanoindentation tests. Scanning electron microscopy and X-ray diffraction analyses were performed to identify the micro-structure and fracture behavior. The flexure strength, modulus and hardness of zirconia increased after 5 h aging and decreased after 10 h aging. No significant alterations of the reduced modulus or hardness of porcelain were detected in the whole aging duration. Width of the zirconia-porcelain interface was extended towards the bulk of zirconia. The detachment and cracks could be observed in zirconia, and the crystal alignment was disorganized in porcelain after 5 h aging and 10 h aging. Mechanical properties of the veneering porcelain are not affected by low-temperature aging. However, the expansion and the alterations of micro-mechanical and micro-structural properties of zirconia-porcelain interface were detected.

•Regulating the gaps between folds on the surface of SF membrane via LBL deposition.•Excellent antibacterial ability of the membranes could be achieved via LY addition.•LBL modification could effectively improve the mechanical properties of membranes.•Cytocompatibility could be regulated by varying the outmost layer of the membranes.•Adding COL with LY could enhance the biocompatibility of the composite membranes.Silk fibroin (SF) has become a promising biomaterial in guided bone regeneration (GBR). In an attempt to modify the size of the gaps on the surface of SF barrier membrane and improve its antibacterial activity, biological and mechanical properties, positively charged Lysozyme (LY)-Collagen Type-I (COL) composites and negatively charged SF were introduced to the negatively charged surface of SF substrates utilizing the electrostatic layer-by-layer (LBL) self-assembly technique. The morphology, chemical structures and element content of the LBL structured membranes were investigated. The results suggested that LY and COL were successfully assembled and the gaps between the folds on the surface of the membranes became smaller gradually with the increase of coated film numbers. Besides, the content of β-sheets of the membranes increased after deposition, which indicated the improvement of their mechanical properties. Moreover, the results of the measurement of immobilized LY and antibacterial assay not only revealed that the enzymatic catalysis and antibacterial activity of the samples enhanced with the increase of coated bilayer numbers but also implied that LBL modified membranes had better antibacterial activity when LY–COL was on the outermost layer. Furthermore, CCK-8 assay certified both SF membrane and LBL structured membranes could facilitate cell growth and proliferation, and the introduction of COL could further promote this ability. Finally, cell attachment and morphology examination provided intuitional evidence that SF membrane and LBL modified membranes have excellent biocompatibility.Download high-res image (115KB)Download full-size image

Biomedical metallic materials, such as titanium and stainless steel, have already been used in the clinic and tissue engineering fields for many years. However, the bio-inert surface limited and challenged their applications. The present study aimed to fabricate and characterize chitosan–gelatin (CSG) nanosphere based antibacterial coatings for surface functionalization of biomedical metallic materials. A CSG nanosphere coating was fabricated on titanium substrate via electrophoretic deposition (EPD). Tetracycline (Tc), as a model functional agent, was loaded into the coating during fabrication. The mechanism of fabricating Tc loaded CSG nanosphere coatings via EPD was investigated for the first time. Characterization of the coatings showed nanosphere structure, and nanospheres can be released from the coatings. The entrapment of Tc was confirmed by fluorescent microscope, Fourier transform infrared spectroscopy and X-ray diffraction. It could also be proved that new hydrogen bonds formed between Tc and gelatin, as well as the increased crystallinity of the coating. Mechanical test demonstrated enhanced mechanical interlocking in the coating-titanium interface of the high Tc concentration group. After coating preparation, the antibacterial effect of Tc was preserved both qualitatively and quantitatively. These results suggested that a Tc loaded CSG nanosphere coating could be successfully fabricated via EPD, and used for the functionalization of a titanium substrate. CSG nanosphere coating loaded with other functional agents would be a promising surface functionalization strategy for biomedical metallic materials.

Mechanical failure of biomaterials, which can be initiated by either violent force, or progressive stress fatigue, is a serious issue. Great efforts have been made to improve the mechanical performances of dental restorations. Virtual simulation is a promising approach for biomechanical investigations, which presents significant advantages in improving efficiency than traditional in vivo/in vitro studies. Over the past few decades, a number of virtual studies have been conducted to investigate the biomechanical issues concerning dental biomaterials, but only with limited incorporation of brittle failure phenomena. Motivated by the contradictory findings between several finite element analyses and common clinical observations on the fracture resistance of post-restored teeth, this study aimed to provide an approach using numerical simulations for investigating the fracture failure process through a non-linear fracture mechanics model. The ability of this approach to predict fracture initiation and propagation in a complex biomechanical status based on the intrinsic material properties was investigated. Results of the virtual simulations matched the findings of experimental tests, in terms of the ultimate fracture failure strengths and predictive areas under risk of clinical failure. This study revealed that the failure of dental post-restored restorations is a typical damage-driven continuum-to-discrete process. This approach is anticipated to have ramifications not only for modeling fracture events, but also for the design and optimization of the mechanical properties of biomaterials for specific clinically determined requirements.

The electrophoretic deposition (EPD) technique can be used to fabricate functional coating on titanium implant. In this study, chitosan/silk fibroin composite coatings were deposited onto titanium substrates viaEPD at about 4 °C, which was recommended for protein stability and cell viability. We tested the characterization and cell behavior of the hydrogel coatings. The obtained gelatinous coatings had a similar macroporous structure with pore size ranging from 100 to 300 μm. The silk fibroin content in the coatings increased proportionally with the increase of the silk fibroin in the electrophoretic solutions. The shear and tensile bond strength of the coatings to titanium substrates increased with the increasing silk fibroin content. In vitro biological tests indicated that chitosan/silk fibroin composite coatings had better cellular affinity than pure chitosan coatings. Therefore, the low temperature EPD is an advanced technique for preparing functional coating on titanium surface and chitosan/silk fibroin composite coatings are promising candidates for loading bioactive protein and appropriate cells.

Titanium has been reported to have some limitations in dental and orthopaedic clinical application. This study described a coating process using a simple chemical method to prepare calcium carbonate coatings on smooth titanium (STi) and sandblasted and acid-etched titanium (SATi), and evaluated the biological response of the materials in vitro. The surfaces of STi, SATi, calcium carbonate coated STi (CC-STi) and calcium carbonate coated SATi (CC-SATi) were characterized for surface roughness, contact angles, surface morphology and surface chemistry. The morphology of MG63 cells cultured on the surfaces was observed by SEM and Immuno-fluorescence staining. Cell attachment/proliferation was assessed by MTT assay, and cell differentiation was evaluated by alkaline phosphatase (ALP) activity. MG63 was found to attach favorably to calcium carbonate crystals with longer cytoplasmic extensions on CC-STi and CC-SATi, resulting in lower cell proliferation but higher ALP activity when compared to STi and SATi respectively. Moreover, CC-SATi is more favorable than CC-STi in terms of biological response. In conclusion, the calcium carbonate coatings on titanium were supposed to improve the osteointegration process and stimulate osteoblast differentiation, especially in early stage. And this method could possibly be a feasible alternative option for future clinical application.Highlights► Calcium carbonate coatings were prepared on titanium substrates. ► The coating process is simple and cost-effective. ► Calcium carbonate coating could induce differentiation toward an osteoblastic phenotype. ► Calcium carbonate coating could enhance the osteointegration process especially in early stage.

The electrophoretic deposition (EPD) is a versatile and cost-effective technique for fabricating advanced coatings. In this study, chitosan/gelatin (CS/G) coatings were prepared on titanium substrates via EPD. The prepared coatings were characterized using fluorescence microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and shear bond strength testing. It was found that CS/G coatings had a similar macroporous structure. The gelatin content in the CS/G coatings gradually increased with the increase of the gelatin in the blend solutions. The shear bond strength of the CS/G coatings also increased with the increasing gelatin content. In vitro biological tests demonstrated that human MG63 osteoblast-like cells achieved better affinity on the coatings with higher gelatin content. Therefore, it was concluded that EPD was an effective and efficient technique to prepare CS/G coatings on the titanium surface and that CS/G coatings with higher gelatin content were promising candidates for further loading of functional agents.

ObjectiveTo synthesise data on the effects of distal-extension removable dental prostheses (RDPs) on masticatory performance of subjects with (extreme) shortened dental arches ((E)SDAs).DataSearch terms were: ‘masticatory’ respectively ‘chewing’ combined with ‘performance’, ‘efficiency’, or ‘ability’.SourcesAn electronic search restricted to the years 2003–2014 in PubMed, Medline, Cochrane Library, Embase, and Science Direct databases.Study selectionStudies exposing data on subjects with SDA (3–5 posterior occluding pairs) or ESDA (0–2 posterior occluding pairs) and on masticatory performance with RDP were included.ResultsFour studies provided data on comminution, three on mixing ability, and one on both tests. Comminution or mixing ability in subjects with (E)SDA was 28–39% lower compared to that of subjects with complete dentitions. In two studies, comminution outcomes when chewing with an RDP ranged from 2% to 32% reduction, indicating better chewing function (smaller X50) compared to comminution without the RDP. One study reported 28–83% lower mixing ability when chewing at the RDP side than chewing at the dentulous side. Generally, more artificial teeth (or longer occlusal platform) in experimental RDPs resulted in better comminution and better mixing ability (significant in four out of five studies), indicating a ‘dose–effect’ relationship.Conclusions(1) Subjects with (E)SDA had a 30–40% reduced masticatory performance; (2) distal-extension RDPs could compensate this reduction partially (some 50%); and (3) more artificial teeth in RDPs resulted in better performance.Clinical significanceDistal-extension RDPs in subjects with SDA partially compensate reduced masticatory performance.

ObjectivesTo evaluate the fracture resistance of fibre post-restored teeth with various ferrule configurations by using fracture failure tests and extended finite element analysis (XFEM).Methods60 Maxillary central incisors were collected and divided into six groups (n = 10) according to various ferrule configurations with different ferrule heights in the labial or palatal region. All of the teeth were endodontically treated and restored by using fibre posts, composite cores and metal crowns. Fracture failure tests were performed on the post retained restorations until fracture occurred. The ultimate load was recorded and analyzed by one way analysis of variance (ANOVA). The fractured specimens were longitudinal sectioned and investigated by micro-stereomicroscope and scanning electronic microscope. XFEM was used to model the fracture of the post-restored teeth and exhibit crack initiation and propagation in the cement layers.ResultsFracture failure tests indicated that the palatal ferrule significantly enhanced the fracture resistance of the post-restored teeth, regardless the height of the labial ferrule. The fractography investigation exhibited that the crack initiated at the palatal margin of the cement layer and propagated to the cervical region of the root. XFEM confirmed these findings and demonstrated that increasing of the palatal ferrule could effectively enhance the anti-fracture ability of the adhesive cement and protected the integrity of adhesive cement.ConclusionAdhesive interface was the susceptible structure of the post retained restorations. Increasing palatal ferrule height could effectively reduce the stress concentrated within the palatal adhesive cement.Clinical Significance“Ferrule effect” exhibits the protection of the interity of cement layer. Increasing the ferrule height, especially in the palatal side, can significantly enhance the anti-fracture ability of fibre post-restored teeth.

Statement of problemColor errors associated with current shade guides and problems with color selection and duplication are still challenging for restorative dentists.PurposeThe purpose of this study was to evaluate an optimized shade guide for visual shade duplication.Material and methodsColor distributions (L*, a*, and b*) of the maxillary left central incisors of 236 participants, whose ages ranged from 20 to 60, were measured with a spectrophotometer. Based on this color map, an optimized shade guide was designed with 14 shade tabs evenly distributed within the given color range of the natural incisors. The shade tabs were fabricated with porcelain powder mixtures and conventional laboratory procedures. A comparison of shade duplication by using the optimized and Vitapan Classical shade guides was conducted. Thirty Chinese participants were involved, and the colors of the left maxillary incisors were selected by using 2 shade guides. Metal ceramic crowns were fabricated according to the results of the shade selection. The colors of the shade tabs, natural teeth, and the ceramic crowns were measured with a spectrophotometer. The color differences among the natural teeth, the shade tabs, and the corresponding metal ceramic crowns were calculated and analyzed (α=.017).ResultsSignificant differences were found in both phases of shade determination and shade duplication (P<.017). The total number of color errors with the optimized shade guide was 3.5, which was significantly less than that of Vitapan, 5.1 (P<.001).ConclusionsThe optimized shade guide system improved performance not only in the color selection phase but also in the color of the fabricated crowns.

The electrophoretic deposition (EPD) technique can be used to fabricate functional coating on titanium implant. In this study, chitosan/silk fibroin composite coatings were deposited onto titanium substrates viaEPD at about 4 °C, which was recommended for protein stability and cell viability. We tested the characterization and cell behavior of the hydrogel coatings. The obtained gelatinous coatings had a similar macroporous structure with pore size ranging from 100 to 300 μm. The silk fibroin content in the coatings increased proportionally with the increase of the silk fibroin in the electrophoretic solutions. The shear and tensile bond strength of the coatings to titanium substrates increased with the increasing silk fibroin content. In vitro biological tests indicated that chitosan/silk fibroin composite coatings had better cellular affinity than pure chitosan coatings. Therefore, the low temperature EPD is an advanced technique for preparing functional coating on titanium surface and chitosan/silk fibroin composite coatings are promising candidates for loading bioactive protein and appropriate cells.