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Background: Previous studies showed that hydroxyapatite electret (HAE) accelerates the regeneration of vascular endothelial cells and angiogenesis. This study investigated the effects of HAE in myocardial infarction (MI) model mice. Methods and Results: MI was induced in mice by ligating the left anterior descending artery. Immediately after ligation, HAE, non-polarized hydroxyapatite (HAN), or water (control) was injected into the infarct border myocardium. Functional and histological analyses were performed 2 weeks later. Echocardiography revealed that HAE injection preserved left ventricular systolic function and the wall thickness of the scar, whereas HAN-injected mice had impaired cardiac function and thinning of the wall, similar to control mice. Histological assessment showed that HAE injection significantly attenuated the length of the scar lesion. There was significant accumulation of CD31-positive cells and increased expression of vascular endothelial growth factor (Vegf), intercellular adhesion molecule-1 (Icam1), vascular cell adhesion molecule-1 (Vcam1), hypoxia-inducible factor-1α (Hif1a), and C-X-C motif chemokine ligand 12 (Cxcl12) genes in the infarct border zone of HAE-injected mice. These effects were not induced by HAN injection. Anti-VEGFR2 antibody canceled the beneficial effect of HAE. In vitro experiments in a human cardiovascular endothelial cell line showed that HAE dose-dependently increased VEGFA expression. Conclusions: Local injection of HAE attenuated infarct size and improved cardiac function after MI, probably due to angiogenesis. The electric charge of HAE may stimulate angiogenesis via HIF1α-CXCL12/VEGF signaling.

TiO2 nanosheets have been studied as photocatalysts in various fields, and their performance has been actively improved. Herein, we prepared titania nanosheets with a smaller size than those reported previously with a side length of 29 nm and investigated their photocatalytic activity. (NH4)2TiF6 and Ti(OBu)4 were used as raw materials, and the F/Ti ratio was varied in the range of 0.3 to 2.0 to produce a series of samples with different side lengths by hydrothermal synthesis. A reduction in the F/Ti ratio led to the reduced size of the titanium nanosheets. The photocatalytic activity of each sample was evaluated through the degradation of methylene blue (MB) under ultraviolet (UV) irradiation (365 nm, 2.5 mW/cm2). UV irradiation promoted the decomposition of MB, and the highest degradation efficiency was achieved using titania nanosheets prepared with a F/Ti ratio of 0.3. The high catalytic activity can be attributed to the increase in the surface area due to size reduction. The ratio of the {001} surface exposed on the titania nanosheet also affected the photocatalytic activity; it resulted in increased activation of the reaction. This study demonstrates that further activation of the photocatalytic activity can be achieved by adjusting the size of titania nanosheets.

There is limited research on the influence of different sintering temperatures on the properties of highly translucent zirconia ceramics. This study demonstrated the influence of different sintering temperatures on the translucency, crystallographic structure, biaxial flexural strength, microstructure, and low-temperature degradation (LTD) of three highly translucent zirconia grades, i.e., 3 mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP), 4 mol% yttria-partially-stabilized zirconia (4Y-PSZ), and 5 mol% yttria-PSZ (5Y-PSZ). The specimens were characterized using colorimetry, X-ray diffraction, scanning electron microscopy, Weibull analysis, and LTD tests (134°C; 20 h). The increase in the sintering temperature did not affect the translucency of 3Y-TZP, whereas it increased the translucencies of 4Y-PSZ and 5Y-PSZ. All the zirconia grades exhibited grain enlargement and unchanged biaxial flexural strengths with the increase in the sintering temperature. The degradation of 3Y-TZP and 4Y-PSZ at a sintering temperature of 1,600°C was faster than that at other sintering temperatures.

Zirconia ceramics have been widely used in dentistry. Herein, we assess the surface morphology, surface texture, and osteoblast response of additively manufactured zirconia and alumina-toughened zirconia (ATZ) in comparison with titanium. The surface roughness, contact angle, and surface microstructure of titanium sandblasted with large-grit alumina and subsequently acid-etched using 18% HCl and 49% H2SO4 (SLA-titanium), uniaxially pressed zirconia (UP zirconia), additively manufactured zirconia (AM zirconia), and additively manufactured ATZ (AM ATZ) were investigated. Moreover, the cell viability, alkaline phosphatase (ALP) activity, and gene expression of type I collagen on these materials were evaluated. The data were statistically analyzed using one-way ANOVA with Tukey’s post hoc test. SLA-titanium showed the highest surface roughness and contact angle. The other three materials showed comparable surface roughness and contact angles. Micro- and nanoroughness were observed on the surface of SLA-titanium. UP zirconia and AM zirconia had similar surface morphologies. The cell viability, ALP activity, and gene expression of type I collagen on AM zirconia were comparable to or better than those on SLA-titanium. Our results indicate that AM zirconia is a promising material for zirconia dental implants.

Background: The aim is to classify dentition using a novel texture-based automated convolutional neural network (CNN) for forensic and prosthetic applications. Methods: Natural human teeth (n = 600) were classified, cleaned, and inspected for exclusion criteria. The teeth were scanned with an intraoral scanner and identified using a texture-based CNN in three steps. First, through preprocessing, teeth images were segmented by extracting the front-facing region of the teeth. Then, texture features were extracted from the segmented teeth images using the discrete wavelet transform (DWT) method. Finally, deep learning-based enhanced CNN models were used to identify these images. Several experiments were conducted using five different CNN models with various batch sizes and epochs, with and without augmented data. Results: Based on experiments with five different CNN models, the highest accuracy achieved was 0.8 and the precision was 0.8 with a loss value of 0.9, a batch size of 32, and 250 epochs. A comparison of deep learning models with different parameters showed varied accuracy between the different classes of teeth. Conclusion: The accuracy of the point-based CNN method was promising. This texture-identification method will pave the way for many forensic and prosthodontic applications and will potentially help improve the precision of dental biometrics.

The purpose of this study was to evaluate the influence of resin-coating using one-bottle adhesives on the bond strength of resin cements in single-visit and multiple-visit treatments. Three one-bottle adhesives were used for resin-coating and/or pre-treatment adhesives prior to cementation, in conjunction with resin cements from the same manufacturers: Clearfil Universal Bond Quick with Panavia V5 (UBQ/Pv5), Scotchbond Universal Adhesive with RelyX Ultimate (SBU/RxU), and Optibond All-in-one with NX3 Nexus (OP/NX3). Bovine dentin surfaces were left uncoated or resin-coated. After 1-h water storage (single-visit) or 1-week water storage with a non-eugenol temporary cement (multiple-visit), a CAD/CAM resin block was cemented to uncoated or resin-coated dentin surfaces. Microtensile bond strengths (µTBSs) were measured and statistically analyzed (α=0.05). Application of resin-coating improved µTBSs. The multiple-visit group exhibited lower values of µTBS than the single-visit group. Selection of the materials affected µTBSs. Resin-coating and single-visit treatment are desirable for CAD/CAM resin composite restorations.

This study aimed to assess the influence of different light curing units (LCUs) on the polymerization of various flowable resin composites. Three LCUs (Optilux 501, Elipar™ DeepCure-L LED and Bluephase®20i) and eight flowable resin composites: MI FIL Flow, Estelite Flow Quick, Estelite Universal Flow (medium), Estelite Universal Flow (super low), Beautifil Flow Plus, Clearfil Majesty ES Flow, Filtek Supreme Ultra flowable and TetricEvo Flow were tested. For Vickers microhardness (VHN) test and degree of conversion (DC), specimens were prepared and polymerized for 20 s. VHN test was performed at top surfaces (3 indentations) and DC for each specimen was measured using Fourier transform infrared (FT-IR) spectroscopy after 24 h dry storage in dark at 37˚C. The data were analyzed with 2-way ANOVA and t-test with Bonferroni correction. DC and hardness values showed a relationship between materials and LCUs. The curing efficacy of LCU type may depend on the material composition.

PURPOSE: To assess the degree of conversion (DC) of dual-curing composite cements when cured through ceramic-veneered zirconia disks. METHODS: Portions of mixed cement, either G-CEM LinkForce (GC), Panavia V5 (Kuraray Noritake) or ResiCEM (Shofu), were placed on the ATR crystal of a Fourier Transform Infrared Spectroscope (FTIR; iS50, Thermo Scientific) and squeezed to a 100-µm film thickness using a microscopy cover glass. DC (%) of the composite cements applied in self-curing mode was measured in the dark at 37°C. Following the dual-curing mode, the cements were light-cured directly (positive control) or through a ceramic-veneered zirconia disk (0.5-mm thick zirconia with a 1.0-mm thick veneering ceramic) for 40 sec using two light-curing units (G-Light Prima 2, GC; PenCure, Morita). Per experimental group, 5 tests were conducted to measure DC in self-cure and dual-cure mode (n=5). FTIR spectra of the composite cement films were acquired to determine DC every min up to 30 min. DC of the composite cements was statistically compared using two-way repeated-measures ANOVA (α=0.05). RESULTS: For all cements investigated, the self-curing mode resulted in significantly lower DC at 10, 20 and 30 min than the light-curing mode. When the composite cements were light-cured through the zirconia disk, DC at 30 min dropped significantly for ResiCem (Shofu), while not for Panavia V5 (Kuraray Noritake) and G-CEM LinkForce (GC). CONCLUSIONS: Self-curing slows down polymerization but does not reach for all composite cements the highest (light-cured) DC. Ceramic-veneered zirconia-based restorations may affect DC of some composite cements. ispartof: JOURNAL OF PROSTHODONTIC RESEARCH vol:65 issue:1 pages:39-45 ispartof: location:Japan status: published

Purpose To investigate the risk of debonding of resin-bonded fixed dental prosthesis frameworks and the effects on the periodontal tissue in patients with reduced alveolar bone levels. Materials & methods The abutment teeth were the upper central incisor and the canine. Resin-bonded fixed dental prosthesis framework fabricated using zirconia was set to models with five different alveolar bone levels. A 200-N load (the maximum clenching force of the anterior teeth) was applied to the center of the pontic to analyze the internal stress on the framework, adhesive cement, and periodontal tissue using finite element analysis. Results The mean maximum principal stress generated in the framework was 25.33 and 29.35 MPa in the models with the normal and the lowest alveolar bone level, respectively. Regarding shear stress on the adhesive cement, stress concentration was observed on the connector side in all models, and it increased on the cervical side of the central incisor as the alveolar bone level decreased. In addition, the mean maximum and minimum principal strains generated on the periodontal ligament of the central incisor and canine tended to increase as alveolar bone loss progressed. Furthermore, the mean maximum principal stress on the cortical bone was the greatest in the model with the most significant bone loss at 5.10 MPa. Conclusions This study suggested that the risk of debonding and periodontal tissue damage might be higher when resin-bonded fixed dental prosthesis frameworks were used in patients with reduced alveolar bone levels compared to those in a healthy state. This article is protected by copyright. All rights reserved.

Gene therapy has been explored as a future alternative for treating heart disease. Among several gene delivery systems aimed at penetrating specific target cells, we focused on safe and non-viral gene delivery materials with a high transfection efficiency. Although various techniques have been developed, the mechanisms underlying the cellular uptake of gene delivery materials have not yet been sufficiently studied in cardiomyocytes. The aim of this study was to determine how hydroxyapatite (HAp) nanoparticles contribute to the delivery of plasmid DNA (pDNA) into cardiomyocytes. We fabricated HAp nanoparticles using the water-in-oil (W/O) emulsion method and used these nanoparticles as the delivery vector for transfecting cardiomyocyte-derived HL-1 cells. HAp exhibited particles on the nanoscale and with a low cytotoxicity in HL-1 cells. The transfection assay performed with several endocytosis inhibitors suggested that the HAp/pDNA complexes were internalized by HL-1 cells through macropinocytosis. Furthermore, this HL-1 cell uptake was generated in response to HAp stimulation. Thus, HAp is a positive regulator of macropinocytosis in HL-1 cells and a good system for gene delivery in cardiomyocytes.

This study investigated the efficacy of copper (Cu) as an antibacterial element incorporated on titanium (Ti) surface by electrochemical treatment. Cu was incorporated onto Ti surface by micro-arc oxidation (MAO). A small amount of Cu was incorporated into the oxide layer and was found to be in oxidized states. Cu-incorporated samples exhibited no-harmful effect on the proliferation of osteoblastlike cells. Moreover, the difference in antibacterial property between fresh and incubated samples was evaluated using gram-positive and gram-negative facultative anaerobic bacteria. The specific antibacterial property of Cu incorporated into the Ti surface were confirmed. The antibacterial property prolonged upon immersion in physiological saline for 28 days. In other words, MAO-treated Ti containing Cu in this study is expected to achieve long-term antibacterial property in practical usage.

This study aimed to evaluate the surface strain at the cervical area of endodontically treated molars with a large pulp chamber restored using a composite resin core with three different types of core build-up systems.Reproduction models of human mandibular molars with prepared post spaces were used in this study. Roots duplicated with a composite resin were used as the experimental teeth. Three types of core build-up systems were used: composite resin core(RC), composite resin core with fiber posts (FC), and composite resin core with a prefabricated zirconia tube (ZC). Each group comprised eight specimens. Crowns made of yttria partially stabilized zirconia were cemented with dual-cure resin cement. Four strain gauges were attached to the surfaces of each specimen: the cervical area of the root and crown, on the buccal and lingual sides. The surface strain at each cervical area was measured using a static loading test and statistically analyzed.In the case of static loading to the buccal cusp inner slope, ZC showed a significantly lower strain than RC in the crown on the buccal side and in the root and FC in the root. In the central fossa, ZC showed a significantly lower strain than FC in the root on the lingual side.The prefabricated zirconia tube reduced the surface strain at the cervical area of the buccal/lingual root in molars; however, the effect was small in the cervical area of the crown.

To analyze and compare the emergence angle (EA) using two measurement methods, conventional and modified (EA-GPT and EA-R), the EAs of all-natural teeth were evaluated and classified to derive a suitable and predictable clinically applicable measurement method.Natural human teeth (n=600) were classified, cleaned, and thoroughly inspected. Teeth were scanned using an intraoral scanner. The scanned data were analyzed using three-dimensional analysis software for both methods with several points per surface. A Bland-Altman analysis was used for statistical analysis and a heat map and a nonparametric density plot to assess the repetition and distribution. An XGBoost regression model was used for prediction.The EA-R method showed significantly different values compared to the EA-GPT method, representing an increase of 17.5-20.7% for the proximal surfaces. An insignificant difference between the two methods was observed for other surfaces. Different teeth classes showed variation in the normal range, thereby resulting in a new classification of the EA for all-natural teeth based on the interquartile range. The machine learning gradient boosting model predicted conventional data with an average mean absolute error of 0.9.Variations in the natural teeth EA and measurement methods, suggest a new classification for EA. The established artificial intelligence method demonstrated robust performance, which could aid in implementing EA measurement in prosthetic designs.

Recently, metal-free restoration has become the standard in prosthetic treatment. However, it is still unclear which combination is most effective in preventing root fracture and secondary caries. The purpose of this study was to evaluate the influence of different post systems, crown materials, crown thickness and luting agents on the stress distribution around the crown margins, cervical dentin and the tip of the post.Ninety-six mandibular first premolar models were developed and analyzed using finite element analysis (FEA). Two designs of crowns, six kinds of crown materials, four types of post and core systems and two kinds of luting agents were included and evaluated for the stress distribution within the abutment teeth. The Von Mises stress magnitudes were compared among all models.The stress at the tip of the post decreased as the young's modulus of luting agent decreased; The stress concentrated more at the cervical area (dentin and crown), as the physical properties of the crown material increased.Crowns fabricated using polyetheretherketone (PEEK) can reduce the stress concentration at the cervical area, so it may be possible to reduce the amount of tooth reduction during abutment tooth preparation. The stress distribution around the post tip is affected by the post and core systems and luting agent, regardless of crown materials and thickness. When inserting a post of the higher Young's modulus such as zirconia post, methyl methacrylate luting cement can reduce the stress concentration at the tip of the post.

Osteochondral defects of articular cartilage cannot regenerate spontaneously. For its surgical treatment, advancements in cartilage tissue engineering have particularly focused on subchondral bone lesions that tend to delay healing. Therefore, it is important to understand interactions between subchondral bone and chondrocytes. This study aimed to investigate the behavior of chondrogenic ATDC5 cells on oriented hydroxyapatite (HAp) films that mimic bone surfaces. HAp nanoparticles prepared herein were needle like and plate like. HAp films were formed through self-organization of the nanoparticles and had 2D structures regularly arrayed with the particles. Both films prominently comprised a-plane orientation surfaces but differed in the degree of hydrophilicity because of the patterns of particle self-assembly. ATDC5 cells cultured on the HAp film with plate-like particles could adhered in a shorter period but could not spread. The adhesive force of cells was weaker with the hydrophilic surface than with other surfaces, as determined using a trypsin-based cell detachment assay. In addition, ATDC5 cells displayed enhanced proliferation and chondrogenic differentiation. Our results suggest that the oriented HAp film formed using plate-like particles provided chondrogenic cells with a desired scaffold as that of subchondral bone to increase cell proliferation and differentiation.

Background The scaffold for head and neck reconstruction needs mechanical strength to maintain specific forms. Hydroxyapatite (HA) enhances the mechanical strength of hydrogel and is routinely used for cartilage regeneration. However, there is a demand for hydroxyapatite that controls chondrogenic cell behavior. Objective Our aim was to regulate HA morphology through a hydrothermal process using organic acid and enhance chondrocyte proliferation and differentiation using shaped-regulated HA. Methods HA was synthesized from dodecanedioic acid (DD:HA) and oleic acid (OA:HA) by a hydrothermal method and then coated onto glass plates. Surface properties of the samples were compared by various techniques. Surface roughness and contact angles were calculated. Proliferation and differentiation of chondrogenic cells were measured by MTT assays and Alcian Blue staining, respectively, after various incubation periods. Results The morphological structures of DD:HA and OA:HA were different; however, the crystallinity and chemical structures were similar. Surface roughness and hydrophilic behavior were higher on DD:HA. DD:HA enhanced chondrogenic cell proliferation over time. The differentiation of ATDC5 cells was also increased on the DD:HA surface compared with those in other groups. Conclusions DD:HA enhanced cell viability to a greater extent than OA:HA did, indicating its excellent potential as an inorganic material compatible with chondrocyte regeneration.

In the present study, the influence of the SiO2 content of polyetheretherketone (PEEK) on the bonding between PEEK and resin cement, and the corresponding mechanical properties, were evaluated. Three experimental PEEK samples with varying amounts of SiO2, and PEEK containing 20 wt% of TiO2 (DK), were investigated. The tensile bond strength (TBS) was evaluated before and after 10,000 thermal cycles, upon polishing, sandblasting, and conditioning of the specimens with BONDMER lightless containing a silane coupling agent, and bonded with ESTECEM II. The crystallinity, flexural modulus, and flexural strength were determined after 10,000 thermal cycles. TBS values were analyzed by two-way ANOVA and a t-test with Bonferroni correction (α

This experiment assessed the effect of elapsed time between air abrasion and bonding on tensile bond strength (TBS) between computer-aided design/computer-aided manufacturing (CAD/CAM) composite resin blocks and luting agents. Specimens were divided into eight groups classified by block type (Estelite Block or HC Block), elapsed time after air abrasion (none [D0] or 1 week [D7]), luting agent type (Estecem [ESC] or Rely X Ultimate [RLU]), and polymerization condition (chemical cured [CC] or light cured [LC]). In the CC+ESC group, TBS was significantly higher at D0 than at D7. There was also a significant difference between blocks in all groups except the LC+ESC group. Scanning electron microscopy and atomic force microscopy were used to observe the surfaces of blocks after air abrasion and indicated that blocks absorbed water in air with elapsed time, which affected TBS between CAD/CAM composite resin blocks and luting agents.

Recently, the problem of infection on implanted devices caused by the formation of biofilms has been recognized. Surface treatment to prevent the initial stages of bacterial adhesion and subsequent bacterial growth is the only possible solution against such infection. In this study, simple electrochemical treatment was used for introducing silver, an antibiotic agent, on the titanium surface. A porous oxide layer containing small amounts of silver was formed on the metal of the substrate. This was done by microarc oxidation using the electrolyte with silver nitrate. The porous oxide layer was almost amorphous with a small fraction of anatase phase. The samples prepared using the electrolyte containing 0.04 mM or a higher concentration of silver nitrate showed an excellent antibacterial effect against both

This study aims to elucidate the relationships between the flexural strength and surface topography of composite resin blocks, utilized for the CAD/CAM system, after milling in various step-over amounts. The rectangular specimens were milled from CAD/CAM blocks with step-over amount 0.01, 0.02, 0.05, 0.1, and 0.2 mm; further, a three-point bending test was conducted to reveal the flexural strength. The surface morphology after milling was assessed by a 3D laser microscope. The surface roughness significantly decreased by reducing the step-over amount. Although there was significant association between the surface roughness and flexural strength by the Pearson correlation, the 95% confidence intervals of the flexural strength were between the mirror-polished and sand-blasted groups. These results suggest that a precise step-over amount enables us to obtain a smooth surface. Furthermore, the flexural strength of the rough surface milled by a large step-over amount caused no damage to the composite resin for CAD/CAM crown.

Recently, silver (Ag) and copper (Cu) have been incorporated into a titanium (Ti) surface to realize their antibacterial property. This study investigated both the durability of the antibacterial effect and the surface change of the Ag- and Cu-incorporated porous titanium dioxide (TiO2) layer. Ag- and Cu-incorporated TiO2 layers were formed by micro-arc oxidation (MAO) treatment using the electrolyte with Ag and Cu ions. Ag- and Cu-incorporated specimens were incubated in saline during a period of 0&ndash, 28 days. The changes in both the concentrations and chemical states of the Ag and Cu were characterized using X-ray photoelectron spectroscopy (XPS). The durability of the antibacterial effects against Escherichia coli (E. coli) were evaluated by the international organization for standardization (ISO) method. As a result, the Ag- and Cu-incorporated porous TiO2 layers were formed on a Ti surface by MAO. The chemical state of Ag changed from Ag2O to metallic Ag, whilst that of Cu did not change by incubation in saline for up to 28 days. Cu existed as a stable Cu2O compound in the TiO2 layer during the 28 days of incubation in saline. The concentrations of Ag and Cu were dramatically decreased by incubation for up to 7 days, and remained a slight amount until 28 days. The antibacterial effect of Ag-incorporated specimens diminished, and that of Cu was maintained even after incubation in saline. Our study suggests the importance of the time-transient effects of Ag and Cu on develop their antibacterial effects.

We demonstrated the crystallization of calcium carbonate in the presence of polyaspartic acid (PAsp) and polylysine (PLys) under double-diffusion conditions in agar hydrogels. The crystallization of precipitated CaCO3 was discussed based on the equivalency rule, and it was suggested that the nucleation of CaCO3 in the presence of PLys and PAsp occurred heterogeneously on the polypeptide assemblies that act as templates for nucleation. With PLys alone, the precipitates had calcite as the major component and vaterite as the minor component, where calcite and vaterite adopted dendritic and spherulitic morphologies, respectively. In the presence of PAsp alone and a mixture of PLys and PAsp, the precipitates comprised calcite spherulites only. The spherulites had a hierarchal structure with an inner part (the core) having a loose structure and an outer part composed of calcite crystals that grew radically from the core. The cores completely dissolved during crystallization, resulting in the formation of spheru...

Hydroxyapatite (HAp) plates were successfully synthesized using dodecanedioic acid (DDDA). Following the preparation of an ethanolic solution of DDDA, solutions of calcium and phosphate were added in succession to produce a white slurry upon mixing. Subsequent processing of this slurry under hydrothermal conditions provided HAp plates of various sizes. Indeed, the plate size could be changed by varying the quantity of DDDA employed in the synthesis, with larger particles being obtained in the presence of larger quantities of DDDA. It was confirmed that a calcium–DDDA complex (Ca-DDD, calcium dodecanedioate) was formed upon mixing of the DDDA and calcium solutions. The observed morphological control could potentially be accounted for by the formation of Ca-DDD. More specifically, during crystal growth, Ca-DDD plays the role of a nucleation substrate (template), a pH buffer, and a calcium reservoir. Finally, we demonstrated that the obtained HAp plates could be employed to prepare a HAp film with high cryst...

Purpose To investigate stress and strain concentrations on resin-bonded fixed dental prostheses (RBFDPs) frameworks of different design using finite element analysis. Methods A human dry skull was scanned and models were produced using three-dimensional printer. After abutment preparation, three frameworks, including a three-unit RBFDP, and two-unit cantilevered RBFDPs using #21 and #23 for the abutment tooth, were fabricated. Scanned data were subtracted to define boundary of each structure. Occlusal force (200N) was loaded at 45° to long axis of the pontic. The distributions of shear stress and principal strain in the RBFDP models were measured to evaluate the risk for framework-debonding from the abutment teeth and the impact on periodontal tissue. Results The percentage voxels with shear stress >11MPa in adhesive cement layer of three-unit RBFDP using #21 and #23 were 4.16% and 2.25%, respectively; in two-unit cantilevered RBFDPs, it was 19.25% using #21, and 23.4% using #23. The maximum principal strain on periodontal ligaments in two-unit cantilevered RBFDPs using #21 was the largest, and smallest in the three-unit RBFDP. The maximum principal strain in framework was largest in the two-unit cantilevered RBFDP using #23, and smallest in the three-unit RBFDP. Conclusions The risk for framework-debonding in three-unit RBFDPs was substantially lower than that in two-unit RBFDPs. In difficult cases with indication for three-unit RBFDPs, two-unit cantilever design using the canine would be more advantageous for preservation of periodontal tissue, while for risk of framework-debonding, the design using the central incisor would be more advantageous.

Hydroxyapatite (HAp), a type of calcium phosphate found in bones and teeth, exhibits proton conductivity. In this study, its conductivity is investigated by measuring the complex permittivity of polycrystalline hydroxyapatite samples obtained via a sintering process. The dielectric dispersions measured from samples with different grain sizes are successfully explained using the Maxwell-Wagner interfacial polarization model. The results show that polycrystalline hydroxyapatite consists of both a high impedance grain boundary and a proton-conductive grain that has a conductivity of about 1.0 × 10− 7 S cm− 1 at 573 K. The interfacial polarization is confirmed using thermally stimulated depolarization current measurements. Additionally, electrets are prepared with the polycrystalline HAp via a poling process, and it is demonstrated that the electret formation is caused by the interfacial polarization.

We demonstrated the crystallization of calcite on nonpolarized and polarized (10.4)-oriented calcite single crystal substrates in the presence of poly-lysine (PLys) as a poly amino acid. The PLys and the electric field due to polarized calcite substrates showed a significant effect on the morphologies of calcite precipitates. At a small amount of PLys, rhombohedral calcite crystals, with notches in the edges of the rhombohedra, formed through homoepitaxy and constructed aggregates with an island structure. At a large amount of PLys, the calcite precipitates had overgrown calcite crystals, which were formed by epitaxial growth on each of the rhombohedral surfaces of already formed calcite rhombohedra, and the calcite aggregates became elongated in the direction perpendicular to the substrate. As the amount of PLys increased, the overgrown calcite crystals tapered toward their ends, and some of the overgrown calcite crystals exhibited a cone-shaped appearance. These cone-shaped crystals consisted of aggrega...