Electro-optic properties of liquid crystal cells with nanowall electrodes.

This work fabricates a nanowall electrode for achieving advanced liquid crystal (LC) devices and improving LC displays. The nanowall electrode consists of indium-tin-oxide (ITO) sheets stacked with nanowalls, and the nanowalls have a height and thickness of 4 µm and 500 nm, respectively. The high aspect ratio (8.0) of the nanowalls sets the nanowall electrode apart from previous electrodes. A flat electrode that comprises only ITO sheets is used to evaluate the nanowall electrode. The LC cell with the nanowall electrode exhibits better electro-optic properties than the LC cell with the flat electrode due to the strong transverse electric field and small subelectrode gap of the nanowall electrode. Especially, the operating voltage (3.7 V) of the nanowall cell is 36% smaller than that (5.8 V) of the flat cell. Therefore, nanowall electrodes have potential in LC lenses, LC antennas, metaverse displays, and digital optics.

Continuously tunable intensity modulators with large switching contrasts using liquid crystal elastomer films that are deposited with terahertz metamaterials.

A liquid crystal elastomer (LCE) film is successfully deposited with a terahertz metamaterial using thermal evaporation via a programmed electronic shutter and high-efficiency cooling system. The transmittance of the metamaterial at its resonance frequency is monotonically increased from 0.0036 to 1.0 as a pump beam bends the LCE film, so the metamaterial has a large switching contrast of 277 at the frequency. The monotonic increase in the resonance transmittance arises from the constant resonance frequency of the metamaterial at the transmittance modulation and depicts that the metamaterial-deposited LCE film can continuously tune the transmitted intensity of a terahertz beam. The metamaterial-deposited LCE film has potential in developing continuously tunable intensity modulators with large switching contrasts for the application of terahertz imaging and terahertz communication. Therefore, the thermal evaporation expands the application of metamaterials and improves their optical properties.

Dentists' performance in dentin-composite resin bonding before and after hands-on course learning.

BACKGROUND/PURPOSE: The restoration longevity depends on a high dentin-composite bond quality. This study investigated learning outcomes when using etch-and-rinse and self-etch adhesives among general practitioners in a hands-on bonding test course. METHODS: We recruited 30 general practitioners to perform shear bond strength (SBS) tests using five adhesives: one Peak® Universal Bond (PUB) etch-and-rinse and four Futurabond DC, Single Bond universal (SBU), Versa Optibond (VOB), and Tetric-N Bond Self-Etch (TNS) self-etch adhesives. SBS tests were conducted at pre-demonstration (pre-demo), post-demonstration (post-demo), and 24-h storage (delayed bonding) stages. SBS data were analyzed with paired Student's t-tests. We defined 17 MPa as "qualified bond strength (QBS)". The percentages of samples with SBS achieving QBS were analyzed using Mantel-Haenszel chi-square tests. The fracture surfaces of the samples were examined by scanning electron microscopy (SEM). RESULTS: Using PUB caused no significant differences in SBS between pre- and post-demo samples, whereas the SBS of the two self-etch adhesives (SBU and VOB) improved in post-demo samples (p < 0.05). SBU showed the highest percentage of samples with SBS achieving QBS in all three groups (pre-demo = 70%, post-demo = 83%, and delayed bonding = 76.5%). The QBS percentages of VOB and TNS notably improved from 0% (pre-demo) to 71.4% and 23.5% (post-demo), respectively. SEM indicated bubble-like defects at the dentin-resin interfaces in cases of low SBS. CONCLUSION: Bonding performance is both operator- and product-dependent. The continuing education hands-on course does help dentists to improve the bond strength especially when the self-etch system is used.

Strontium ion can significantly decrease enamel demineralization and prevent the enamel surface hardness loss in acidic environment.

BACKGROUND/PURPOSE: Strontium ion may play a role similar to calcium ion in enamel remineralization. The aim of this study was to investigate the effect of strontium ion concentration gradient on the demineralization of enamel. METHODS: Citric acid and sodium citrate were used to prepare 16 different experimental acidic solutions with four different pH values (2.5, 3.5, 4.5, and 5.5) and four different strontium ion concentrations (0 M, 10-4 M, 10-3 M, and 10-2 M). Forty-eight human enamel samples were divided into 16 groups (n = 3) and immersed into the 16 different acidic solutions for 3 min. The phosphorus ion concentrations in 16 different acidic solutions were measured and compared. The enamel surface hardness was measured with a Vickers hardness tester. The energy dispersive spectrometer was used to detect the strontium ion content in the enamel surface. RESULTS: Addition the strontium ions to the acidic solution could reduce the dissolution of the enamel. At pH 3.5 and pH 5.5, significantly lower phosphorus ion concentrations were detected in the acidic solutions with the addition of 10-2 M strontium ions. There was a less reduction of enamel surface hardness, while the strontium ion concentration increased in the acidic solution. At pH 2.5, the addition of 10-4 M, 10-3 M, or 10-2 M strontium ions to the acidic solution resulted in a significant increase in the strontium ion content in the enamel surface. CONCLUSION: Strontium ion can decrease the dissolution of the enamel and prevent the enamel surface hardness loss in acidic environment.

Effects of fluoride and epigallocatechin gallate on soft-drink-induced dental erosion of enamel and root dentin.

BACKGROUND/PURPOSE: Fluoride and epigallocatechin gallate (EGCG) have been proven to prevent dental caries. The purpose of this study was to evaluate the effects of fluoride and EGCG on soft-drink-induced dental erosion in vitro. METHODS: Forty enamel and dentin specimens were prepared from extracted human teeth. The specimens were divided into 4 groups and treated separately with distilled water (as control), 0.5 M sodium fluoride (NF), 400 µM EGCG (EG), and a solution containing 0.5 M NaF and 400 µM EGCG (FG). Cyclic erosive treatment was performed according to the experimental procedures. The specimens were analyzed using laser scanning confocal microscopy, scanning electron microscopy, and a microhardness tester. The data were analyzed using ANOVA and Bonferroni's post hoc test. The significance level was set at 5%. RESULTS: The amount of substance loss was lower in the NF and EG groups than in the control group (p < 0.05). The erosion-caused substance loss was more pronounced in the dentin than in the enamel specimens. Surface microhardness loss was lower in the NF and EG groups than in the control group (p < 0.05). The diameter of the dentinal tubule was wider in the control group than in the NF and EG groups (p < 0.05). No combined effects were observed in the FG group. CONCLUSION: Both fluoride and EGCG are effective in preventing soft-drink-induced erosion compared with the control group. Fluoride and EGCG may interfere with each other. The mechanisms of the anti-erosive effect need to be explored in the future.

Polishing mechanism of light-initiated dental composite: Geometric optics approach.

BACKGROUND/PURPOSE: For light-initiated dental hybrid composites, reinforcing particles are much stiffer than the matrix, which makes the surface rugged after inadequate polish and favors bacterial adhesion and biofilm redevelopment. The aim of the study was to investigate the polishing mechanism via the geometric optics approach. METHODS: We defined the polishing abilities of six instruments using the obtained gloss values through the geometric optics approach (micro-Tri-gloss with 20°, 60°, and 85° measurement angles). The surface texture was validated using a field emission scanning electron microscope (FE-SEM). Based on the gloss values, we sorted polishing tools into three abrasive levels, and proposed polishing sequences to test the hypothesis that similar abrasive levels would leave equivalent gloss levels on dental composites. RESULTS: The three proposed, tested polishing sequences included: S1, Sof-Lex XT coarse disc, Sof-Lex XT fine disc, and OccluBrush; S2, Sof-Lex XT coarse disc, Prisma Gloss polishing paste, and OccluBrush; and S3, Sof-Lex XT coarse disc, Enhance finishing cups, and OccluBrush. S1 demonstrated significantly higher surface gloss than the other procedures (p < 0.05). The surface textures (FE-SEM micrographs) correlated well with the obtained gloss values. CONCLUSION: Nominally similar abrasive abilities did not result in equivalent polish levels, indicating that the polishing tools must be evaluated and cannot be judged based on their compositions or abrasive sizes. The geometric optic approach is an efficient and nondestructive method to characterize the polished surface of dental composites.

A mesoporous biomaterial for biomimetic crystallization in dentinal tubules without impairing the bonding of a self-etch resin to dentin.

BACKGROUND/PURPOSE: CaCO3@mesoporous silica reacted with phosphoric acid (denoted as CCMS-HP) enables the growth of calcium phosphate crystals in dentinal tubules. This study tested whether CCMS-HP could be used to form a biomimetic barrier on the exposed dentin for prevention of dentin sensitivity without impairing the bonding of Single Bond Universal (SBU) self-etch adhesive to the dentin. METHODS: Twenty-four dentin disks were prepared and divided into three groups: (1) SBU group (n = 8), in which SBU self-etch adhesive was bonded to the dentin disk directly; (2) CCMS-HP group (n = 8), in which CCMS-HP was applied onto the dentin surface; and (3) CCMS-HP/SBU group (n = 8), in which the dentin surface was first treated with CCMS-HP and then boned by SBU. The permeation depth of crystals into the dentinal tubules was examined and measured with a scanning electron microscope. The shear bonding strength of SBU and CCMS-HP/SBU to dentin was also measured. RESULTS: The mean crystal permeation depth was 35.8 ± 6.9 µm for the CCMS-HP/SBU group and 33.6 ± 12.2 µm for the CCMS-HP group; no significant difference was found between the two groups. Moreover, the mean shear bonding strength was 22.7 ± 6.7 MPa for the CCMS-HP/SBU group and 23.3 ± 7.0 MPa for the SBU group. There was also no significant difference between the two groups. CONCLUSION: CCMS-HP can be used to form a biomimetic barrier for prevention of dentin sensitivity because it neither impedes the bonding of SBU to dentin nor impairs the shear bonding strength between the SBU and dentin.

Effect of the precrack preparation with an ultrasonic instrument on the ceramic bracket removal.

BACKGROUND/PURPOSE: In terms of fracture mechanics, a precrack preparation may facilitate the propagation of a break through the expected fracture plane during the bracket debonding process. The purpose of this study was to evaluate the effect of an ultrasonic precrack preparation on the debonding force and failure modes of ceramic bracket removal. METHODS: Eighty extracted premolars were assigned to four groups: Inspire, precrack Inspire, Clarity, and precrack Clarity groups, with each group containing 20 teeth. The precrack preparations were made at the mesial gingival line angle of Inspire brackets and on the mesial side of Clarity brackets with an ultrasonic tip. Debonding force, failure modes, and bracket breakage score were measured and recorded. Fracture surfaces after bracket debonding were observed with scanning electron microscopy (SEM). RESULTS: We found that the ultrasonic precrack preparation could significantly decrease the average debonding force and the mean bracket breakage scores of both kinds of ceramic brackets. After bracket debonding, 80% of brackets in the precrack Inspire group and 100% of brackets in the precrack Clarity group showed no bracket failure. However, only 25% of brackets in the Inspire group and 75% of brackets in the Clarity group showed no bracket failure. SEM micrographs showed a precrack notch at the adhesive resin after precrack preparation, and no enamel damage was noted after the bracket debonding. CONCLUSION: The ultrasonic precrack preparation can significantly decrease the debonding force and may guide the bracket debonding through a favorable fracture plane without damage to either the bracket or the enamel.

Influence of cyclic heating on physical property and biocompatibility of α- and ß-form gutta-percha.

BACKGROUND/PURPOSE: Thermoplasticized techniques with high temperature and repetitive heating in root canal filling may cause degeneration of gutta-percha, producing cytotoxic byproducts and interfering sealing quality. This study was conducted to investigate the influence of cyclic heating on the physical property and biocompatibility of α- and ß-form gutta-perchas. METHODS: Both α- and ß-form gutta-perchas were submitted to two heating processes: continuous heating and cyclic heating. Continuous heating was carried out by heating the samples up to 300°C and 400°C. The samples were then analyzed by differential scanning calorimetry, differential thermal analysis (DTA), and thermogravimetry. For cyclic heating process, samples were heated from 30°C to 200°C for seven cycles and analyzed with DTA and thermogravimetry. For cell adhesion assay, samples were treated (30°C to 200°C, one and seven cycles), submitted to cell culture and examined by scanning electron microscope. RESULTS: Differential scanning calorimetry and DTA indicated that α-form gutta-percha presented a major endothermic peak at 50-57°C, while ß-form gutta-percha showed two major endothermic peaks at 46-50°C and 60-63°C. Total weight loss of ß-form gutta-percha was about 2-fold greater than that of α-form gutta-percha after continuous heating up to 300°C, or cyclic heating for seven times. Scanning electron microscopy showed no obvious difference of cell adhesion on α- and ß-form samples, even with seven cyclic heating or one heating cycle. However, the attachment of the cells to the culture plate (the control) is better than to the gutta-percha samples. CONCLUSION: The increase of heating cycles for α- and ß-form gutta-percha exerts no adverse influence on their biocompatibility. Because the physical property of ß-form gutta-percha becomes unstable when it is heated at over 300°C or subjected to cyclic heating, ß-form gutta-percha may not be recommended for use in thermoplasticized gutta-percha techniques.

Erosive potential of soft drinks on human enamel: an in vitro study.

BACKGROUND/PURPOSE: Most soft drinks are acidic in nature. Regular consumption of these drinks may result in dental erosion. The aim of this in vitro study was to evaluate the erosive potential of different soft drinks in Taiwan by a novel multiple erosive method. METHODS: Four commercially available soft drinks in Taiwan were selected for this study. The properties of each product were analyzed to measure their pH, titratable acidity, and ion contents. The erosive potential of the soft drinks was measured based on the amount of loss of human enamel surface following its exposure to the soft drinks tested for different periods (20 minutes, 60 minutes, and 180 minutes). The enamel loss was measured using a confocal laser scanning microscope. RESULTS: The pH values of the soft drinks were below the critical pH value (5.5) for enamel demineralization, and ranged from 2.42 to 3.46. The drink with ingredients of citric acid and ascorbic acid had the highest titratable acidity (33.96 mmol OH(-)/L to pH 5.5 and 71.9 mmol OH(-)/L to pH 7). Exposure to all the soft drinks resulted in loss of human enamel surface (7.28-34.07 µm for 180-minute exposure). The beverage with the highest calcium content had the lowest erosive potential. CONCLUSION: All tested soft drinks were found to be erosive. Soft drinks with high calcium contents have significantly lower erosive potential. Low pH value and high citrate content may cause more surface enamel loss. As the erosive time increased, the titratable acidity to pH 7 may be a predictor of the erosive potential for acidic soft drinks. The erosive potential of the soft drinks may be predicted based on the types of acid content, pH value, titratable acidity, and ion concentration.

Effects of ceramic thickness, ceramic translucency, and light transmission on light-cured bulk-fill resin composites as luting cement of lithium disilicate based-ceramics.

PURPOSE: To assess the effects of ceramic thickness, ceramic translucency, and light transmission on restorative composites used as luting cement for lithium disilicate-based ceramics. METHODS: Four luting types of cement were tested (n=8); a dual-cured resin cement (Multilink N), a light-cured conventional flowable composite (Tetric N-Flow), and two light-cured bulk-fill flowable composites (Tetric N-Flow Bulk Fill and X-tra base). The 20 s- or 40 s-light (1000 mW/cm2) was transmitted through 1- or 2-mm-thick high- or low-translucency (HT- or LT-) ceramic discs (IPS e.Max press) to reach the 1-mm-thick luting cement. Light transmitted to cement without ceramic served as a control. Vickers hardness number (VHN), flexural strength (FS), fractography, and degree of conversion (DC) were evaluated. One-way and multi-way analysis of variance was conducted to determine the effects of factors on VHN and FS. RESULTS: Ceramic thickness, light transmission time, and cement type significantly affected the VHN of the luting cement (P < .000). Only Multilink N (LT- and HT-1mm) and Tetric N-Flow (HT-1mm) reached 90% VHN of corresponding control by 20 s-light transmissions, but Tetric N-Flow exhibited lowest VHN and approximately 1/3-1/2 VHN of Multilink N (P < 0.05). X-tra base expressed superior physicochemical properties to Tetric N-Flow Bulk Fill (P < 0.05) and reached >90% VHN of control in all conditions with 40 s-light transmissions except for LT-2 mm. DC, FS, and fractography supported these findings. CONCLUSIONS: The light-cured bulk-fill composite served as a luting cement for lithium-disilicate-based ceramics in a product-dependent manner. Light transmission time is crucial to ensure sufficient luting cement polymerization.

Effects of surface treatments of bioactive tricalcium silicate-based restorative material on the bond strength to resin composite.

OBJECTIVES: This study aimed to enhance the bond strength between Biodentine™ (BD), a bioactive tricalcium silicate (C3S) based material, and resin composite through various surface treatments. METHODOLOGY: BD samples were immersed in either double distilled water or Hank's Balanced Salt Solution and analyzed using X-ray Diffraction (XRD). Shear bond strength (SBS) evaluations of BD were performed using Prime & Bond™ NT (PNT), Single Bond Universal (SBU), Xeno V (Xeno), and glass ionomer cement (GIC) following various etching durations (0 s/ 15 s/ 30 s/ 60 s with 37.5% phosphoric acid). Two primers, RelyX™ Ceramic Primer (RCP) and Monobond ™ Plus (MBP), were chosen to prime BD for SBS enhancement. Fractography and bonding interfaces were examined with energy dispersive X-ray spectroscopy (EDS)/ scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). RESULTS: XRD confirmed BD's main compositions as C3S, Ca(OH)2, CaCO3 and ZrO2 after 14 days crystal maturation. Etched BD did not improve SBS. GIC exhibited the lowest SBS (p < 0.05) among all adhesives, regardless of the etching mode (all < 1 MPa). The highest SBS (17.5 ± 3.6 MPa, p < 0.05) was achieved when BD primed with MBP followed by SBU application. FTIR and EDS showed γ-MPTS and10-MDP within the MBP primer interacted with C3S and ZrO2 of BD, achieving enhanced SBS. Most specimens exhibited mixed or cohesive failure modes. Significance BD's subpar mechanical properties and texture may contribute to its poor adhesion to resin composite. Pretreating BD with MBP primer, followed by SBU adhesive is recommended for improving bond strength.

Epigallocatechin gallate-immobilized antimicrobial resin with rechargeable fluorinated synergistic composite for enhanced caries control.

OBJECTIVES: Given the global prevalence of dental caries, impacting 2.5 billion individuals, the development of sophisticated prevention filling materials is crucial. Streptococcus mutans, the principal caries-causing strain, produces acids that demineralize teeth and initiate dental caries. To address this issue, we aimed to develop a synergistic resin-based composite for enhancing caries control. METHODS: The synergistic resin composite incorporates fluorinated kaolinite and silanized Al2O3 nanoparticle fillers into an epigallocatechin gallate (EGCG) immobilized urethane-modified epoxy acrylate (U-EA) resin matrix, referred to the as-prepared resin composite. The EGCG-modified TPGDA/U-EA network was synthesized by preparing methacrylate-functionalized isocyanate (HI), reacting it with EGCG to form HI-EGCG, and then incorporating HI-EGCG into the TPGDA/U-EA matrix. The lamellar space within the kaolinite layer was expanded through the intercalation of acrylamide into kaolinite, enhancing its capability to adsorb and release fluoride ions (F-). The layered structure of acrylamide/ kaolinite in the U-EA resin composite acts as a F- reservoir. RESULTS: The physico-mechanical properties of the as-prepared resin composites are comparable to those of commercial products, exhibiting lower polymerization shrinkage, substantial F- release and recharge and favorable diametral tensile strength. The immobilized EGCG in the composite exhibits potent antimicrobial properties, effectively reducing the biofilm biomass. Furthermore, the synergistic effect of EGCG and fluorinated kaolinite efficiently counteracts acid-induced hydroxyapatite dissolution, thereby suppressing demineralization and promoting enamel remineralization. SIGNIFICANCE: Our innovative EGCG and fluoride synergistic composite provides enhanced antimicrobial properties, durable anti-demineralization, and tooth remineralization effects, positioning it as a promising solution for effective caries control and long-term dental maintenance.

[Effect of a 10-Methacryloyloxydecyl Dihydrogen Phosphate- treated Bioceramic Sealer on the Bond Strength of an Endodontic Fiber Post: Multilayer Composite Disk Models and Ultra-highspeed Imaging Analysis].

PURPOSE: Multiple materials are found in the root canal after fiber-post cementation. The layer of a bioceramic-based (BC) sealer may affect the bond strength (σBS) of the fiber post in the root canal. The purpose of this study was to employ multilayer compos-ite-disk models in diametral compression to investigate whether the bond strength between a fiber post and root dentin can be in-creased by the application of a primer on the BC sealer. MATERIALS AND METHODS: The multilayers of materials in the root canal required 3D finite-element (FE) stress analyses (FEA) to pro-vide precise σBS values. First, BC sealer was characterized using x-ray powder diffraction (XRD) to determine when the sealer com-pletely set and the types of crystals formed to select which primer to apply to the sealer. We selected a 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP)-based primer to treat the BC sealer before post cementation. Ultra-highspeed (UHS) imaging was utilized to analyze the crack initiation interface. The obtained failure force was used in FE analysis to calculate σBS. RESULTS: UHS imaging validated the fracture interface at the post-dentin junction as FEA simulations predicted. σBS values of the fiber posts placed with various material combinations in the root canal were 21.1 ± 3.4 (only cement/ post), 22.2 ± 3.4 (BC sealer/cement/post) and 28.6 ± 4.3 MPa (10-MDP primer treated BC sealer/cement/post). The 10-MDP-treated BC sealer exhibited the highest σBS (p < 0.05). CONCLUSION: The multilayer composite disk model proved reliable with diametral compression testing. The presence of BC sealer in the root canal does not reduce σBS of the fiber post. Conditioning the BC sealer layer with 10-MDP primer before fiber-post cemen-tation increases σBS.

Application and development of ultrasonics in dentistry.

Since the 1950s, dentistry's ultrasonic instruments have developed rapidly. Because of better visualization, operative convenience, and precise cutting ability, ultrasonic instruments are widely and efficiently applied in the dental field. This article describes the development and improvement of ultrasonic instruments in several dental fields. Although some issues still need clarification, the results of previous studies indicate that ultrasonic instruments have a high potential to become convenient and efficient dental tools and deserve further development.

Effect of simulated debracketing on enamel damage.

BACKGROUND/PURPOSE: A smooth enamel surface after the removal of a bracket from a tooth is essential for both esthetic demands and the prevention of plaque accumulation. The purpose of this study was to evaluate enamel damage caused by three standardized debracketing techniques. METHODS: We established three standardized test devices based on the principles of the squeezing, shearing, and tensile testing methods, which were simulated using a How Plier (TASK 60-306), a Direct Bond Bracket Remover (TASK 60-335 T), and a Lift-Off Debracketing Instrument (3 M-Unitek 444-761), respectively. Thirty teeth in each group were evaluated after debracketing. An optical stereomicroscope and a CCD camera with a computerized image analysis system were used to ascertain the proportion of remnant adhesive area (RAE) on the enamel surface. Fractography was analyzed using a scanning electron microscope. RESULTS: The squeezing debracketing method exhibited the highest debonding force (54.3 ± 7.0 N) and the least damage to the enamel surface (RAE = 99.5% ± 2.4%). The tensile debracketing method preserved most of the adhesive on the enamel surface (RAE = 98.7% ± 3.3%) and required the least debonding force (6.8 ± 1.2 N). However, the shearing debracketing method exhibited a significantly higher debonding force (32.0 ± 8.2 N) and smaller RAE (77.3% ± 33.5%) compared to the tensile debracketing method (p < 0.05). Three specimens appeared to have vertical fractures on their enamel prisms when using the shearing method. CONCLUSION: With the proposed method, we conclude that the squeezing and tensile methods are acceptable for clinical use when debracketing, whereas the Direct Bond Bracket Remover may cause shearing failure, leading to a risk for enamel damage.

Tension-compression viscoelastic behaviors of the periodontal ligament.

BACKGROUND/PURPOSE: Although exhaustively studied, the mechanism responsible for tooth support and the mechanical properties of the periodontal ligament (PDL) remain a subject of considerable controversy. In the past, various experimental techniques and theoretical analyses have been employed to tackle this intricate problem. The aim of this study was to investigate the viscoelastic behaviors of the PDL using three-dimensional finite element analysis. METHODS: Three dentoalveolar complex models were established to simulate the tissue behaviors of the PDL: (1) deviatoric viscoelastic model; (2) volumetric viscoelastic model; and (3) tension-compression volumetric viscoelastic model. These modified models took into consideration the presence of tension and compression along the PDL during both loading and unloading. The inverse parameter identification process was developed to determine the mechanical properties of the PDL from the results of previously reported in vitro and in vivo experiments. RESULTS: The results suggest that the tension-compression volumetric viscoelastic model is a good approximation of normal PDL behavior during the loading-unloading process, and the deviatoric viscoelastic model is a good representation of how a damaged PDL behaves under loading conditions. Moreover, fluid appears to be the main creep source in the PDL. CONCLUSION: We believe that the biomechanical properties of the PDL established via retrograde calculation in this study can lead to the construction of more accurate extra-oral models and a comprehensive understanding of the biomechanical behavior of the PDL.

Multiple growth factors accommodated degradable submicron calcium sulfate hemihydrate/porous hydroxyapatite for dentin-pulp regeneration.

Vital pulp therapy (VPT) has gained significant consideration by utilizing the natural healing capacity of the inflamed pulp in healing process. However, the protective pulp capping materials that facilitate this healing process are still under investigation for the successful promotion of dentin-pulp regeneration. Herein, we developed a bioactive and biodegradable pulp capping material (denoted as sCSHA-GFs) by synthesizing inorganic submicron calcium sulfate hemihydrate (sCS)/porous hydroxyapatite (HA) loaded with growth factors (GFs) such as transforming growth factor-beta 1 (TGF-ß1), fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF). Physiochemical characteristics of submicron CSHA-GFs (sCSHA-GFs) cement were determined. Human dental pulp stem cells (hDPSCs) were used for analyzing their biocompatibility and bioactivity for dentin mineralization. To evaluate the efficacy of sCSHA-GFs, we compared it with a commercial material, mineral trioxide aggregate (MTA), the reference standard used clinically on pulp capping. Our results showed that sCSHA-GFs cement presented good biodegradability with dissolution properties for sustained release of calcium (Ca2+) ions and GFs, and facilitated attachment, proliferation, differentiation and migration of hDPSCs. In addition, sCSHA-GFs cement was found to be more effective than MTA at prolonged incubation time in inducing the mRNA expression levels of odontoblastic differentiation markers, dentin sialophosphoprotein (DSPP) and dentin matrix protein (DMP-1), leading to increased mineralization (with calcium deposits) along with increased alkaline phosphatase (ALP) expressions, evident from Alizarin Red S and ALP staining assays. Our findings suggest that sCSHA-GFs cement may act as a suitable material in VPT for dentin-pulp regeneration.

Vapor construction and modification of stem cell-laden multicomponent scaffolds for regenerative therapeutics.

Tissue engineering based on the combined use of isolated cells, scaffolds, and growth factors is widely used; however, the manufacture of cell-preloaded scaffolds faces challenges. Herein, we fabricated a multicomponent scaffold with multiple component accommodations, including bioactive molecules (BMs), such as fibroblast growth factor-2 (FGF-2) and l-ascorbic acid 2-phosphate (A2-P), and living cells of human adipose-derived stem cells (hASCs), within one scaffold construct. We report an innovative fabrication process based on vapor-phased construction using iced templates for vapor sublimation. Simultaneously, the vaporized water molecules were replaced by vapor deposition of poly-p-xylylene (PPX, USP Class VI, highly compatible polymer, FDA-approved records), forming a three-dimensional and porous scaffold matrix. More importantly, a multicomponent modification was achieved based on using nonvolatile solutes, including bioactive molecules of FGF-2 and A2-P, and living cells of hASCs, to prepare iced templates for sublimation. Additionally, the fabrication and construction resulted in a multicomponent scaffold product comprising the devised molecules, cells, and vapor-polymerized poly-p-xylylene as the scaffold matrix. The clean and dry fabrication process did not require catalysts, initiators or plasticizers, and potentially harmful solvents, and the scaffold products were produced in simple steps within hours of the processing time. Cell viability analysis showed a high survival rate (approximately 86.4%) for the accommodated hASCs in the fabricated scaffold product, and a surprising multilineage differentiation potential of hASCs was highly upregulated because of synergistic guidance by the same accommodated FGF-2 and A2-P components. Proliferation and self-renewal activities were also demonstrated with enhancement of the multicomponent scaffold product. Finally, in vivo calvarial defect studies further revealed that the constructed scaffolds provided blood vessels to grow into the bone defect areas with enhancement, and the induced conduction of osteoblast growth also promoted bone healing toward osseointegration. The reported scaffold construction technology represents a prospective tissue engineering scaffold product to enable accommodable and customizable versatility to control the distribution and composition of loading delicate BMs and living hASCs in one scaffold construct and demonstrates unlimited applications in tissue engineering repair and regenerative medicine applications.

Ice-templated synthesis of multicomponent porous coatings via vapour sublimation and deposition polymerization.

A multicomponent vapour-deposited porous (MVP) coating with combined physical and biochemical properties was fabricated based on a chemical vapour sublimation and deposition process. Multiple components are used based on their natural thermodynamic properties, being volatile and/or nonvolatile, resulting in the sublimation of water vapour (from an iced template), and a simultaneous deposition process of poly-p-xylylene occurs upon radical polymerization into a disordered structure, forming porous coatings of MVP on various substrates. In terms of physical properties, the coating technology exhibits adjustable hydrophobicity by tuning the surface morphology by timed control of the sublimation of the iced template layer from a substrate. However, by using a nonvolatile solution during fabrication, an impregnation process of the deposited poly-p-xylylene on such a solution with tuning contact angles produces an MVP coating with a customizable elastic modulus based on deformation-elasticity theory. Moreover, patterning physical structures with adjustable pore size and/or porosity of the coatings, as well as modulation and compartmentalization to introduce necessary boundaries of microstructures within one MVP coating layer, can be achieved during the proposed fabrication process. Finally, with a combination of defined solutions comprised of both volatile and nonvolatile multicomponents, including functional biomolecules, growth factor proteins, and living cells, the fabrication of the resultant MVP coating serves devised purposes exhibiting a variety of biological functions demonstrated with versatility for cell proliferation, osteogenesis, adipogenesis, odontogenesis, spheroid growth of stem cells, and a complex coculture system towards angiogenesis. Multicomponent porous coating technology is produced based on vapour sublimation and deposition upon radical polymerization that overturns conventional vapour-deposited coatings, resulting in only dense thin films, and in addition, the versatility of adjusting coating physical and chemical properties by exploiting the volatility mechanism of iced solution templates and accommodation of solute substances during the fabrication process. The MVP coating and the proposed fabrication technique represent a simple approach to provide a prospective interface coating layer for materials science and are attractive for unlimited applications.