Tooth Slices Research Articles

Effects of Intra-canal Medicaments on Infrared Light Energy Transmission Through Enamel and Dentin During Photobiomodulation: An InVitro Study.

This invitro study assessed how shade changes induced by endodontic medicaments affect the transmission of single and multiples wavelengths of infrared light through enamel and dentin. Eighteen extracted single-rooted permanent teeth were prepared, removing all extrinsic staining, and cementum. Tooth slices were treated for 4weeks with UltraCal XS, Ledermix, or were untreated controls. Light transmission through enamel-dentin and dentin regions was assessed using diode lasers (660, 808, 904nm) and a multi-wavelength light-emitting diode (LED) light source (700-1100nm). Absorption studieswere performed to evaluate light absorption by components of medicaments. Samples treated with Ledermix showed the greatest shade change, with a corresponding reduction in visible and near infrared light transmission (P<.001) in dentin, whereas UltraCal XS had a milder effect (P<.01). Across different substrates, the greatest light transmission was seen for the multi-wavelength LED light source, followed by 904nm, 808nm, and finally 660nm. Spectrophotometric studies revealed light absorption by turbid and saturated calcium hydroxide solutions. This study shows that medicaments may influence transmission of visible red and near infrared light. Photobiomodulation protocols used in regenerative endodontics should take this effect into account, by incorporating longer near infrared wavelengths (up to 1100nm) and using multi-wavelength light sources to account for this absorption.

Biomimetic pulp scaffolds prepared from extracellular matrix derived from stem cells from human exfoliated deciduous teeth promote pulp-dentine complex regeneration.

To evaluate the role of biomimetic pulp scaffolds derived from the extracellular matrix derived of stem cells from human exfoliated deciduous teeth (SHED-ECM-PS) in promoting pulp-dentine complex regeneration. SHED-ECM-PS was prepared through cell aggregation and decellularization techniques. Histological and immunofluorescence analyses, scanning electron microscopy, and DNA quantification assays were used to characterize the SHED-ECM-PS. Additionally, a tooth slice implantation model was established to evaluate the effects of SHED-ECM-PS on regeneration of the pulp-dentine complex invivo. Extraction medium for SHED-ECM-PS was prepared, and its effect on bone marrow mesenchymal stem cells (BMMSCs) was assessed invitro. Cell counting kit-8 and Ki-67 staining assays were performed to determine cell proliferation. The rate of apoptosis was evaluated by flow cytometry. Wound healing and transwell assays were conducted to evaluate cell migration. Alizarin red S staining was performed to examine mineralized nodule formation. Western blotting was used to detect the expression of osteogenic and odontogenic markers. The results were analysed using an independent two-tailed Student's t-test. p < .05 was considered statistically significant. SHED-ECM-PS was successfully constructed, exhibiting a striped dental pulp-like shape devoid of nuclear structures or DNA components, and rich in fibronectin, collagen I, DMP1 and DSPP. Notably, SHED-ECM-PS showed no impact on the proliferation or apoptosis of BMMSCs. Histological analysis revealed that dental pulp fibroblasts formed an interwoven mesh in the root canal, and angiogenesis was observed in the SHED-ECM-PS group. Moreover, a continuous, newly formed tubular dentine layer with polarized odontoblast-like cells was observed along the inner wall of the root canal. SHED-ECM-PS promoted the migration, polar alignment and mineralized nodule formation of BMMSCs and specifically elevated the expression levels of odontogenic markers, but not osteogenic markers, compared with the control group invitro. SHED-ECM-PS exhibited no cytotoxicity and promoted pulp-dentine complex regeneration invivo as well as cell migration and odontogenic differentiation of BMMSCs invitro. These findings provide evidence that SHED-ECM-PS, as a novel biological scaffold, has the potential to improve the outcomes of REPs.

Injectable Tissue-Specific Hydrogel System for Pulp–Dentin Regeneration

The quest for finding a suitable scaffold system that supports cell survival and function and, ultimately, the regeneration of the pulp–dentin complex remains challenging. Herein, we hypothesized that dental pulp stem cells (DPSCs) encapsulated in a collagen-based hydrogel with varying stiffness would regenerate functional dental pulp and dentin when concentrically injected into the tooth slices. Collagen hydrogels with concentrations of 3 mg/mL (Col3) and 10 mg/mL (Col10) were prepared, and their stiffness and microstructure were assessed using a rheometer and scanning electron microscopy, respectively. DPSCs were then encapsulated in the hydrogels, and their viability and differentiation capacity toward endothelial and odontogenic lineages were evaluated using live/dead assay and quantitative real-time polymerase chain reaction. For in vivo experiments, DPSC-encapsulated collagen hydrogels with different stiffness, with or without growth factors, were injected into pulp chambers of dentin tooth slices and implanted subcutaneously in severe combined immunodeficient (SCID) mice. Specifically, vascular endothelial growth factor (VEGF [50 ng/mL]) was loaded into Col3 and bone morphogenetic protein (BMP2 [50 ng/mL]) into Col10. Pulp–dentin regeneration was evaluated by histological and immunofluorescence staining. Data were analyzed using 1-way or 2-way analysis of variance accordingly (α = 0.05). Rheology and microscopy data revealed that Col10 had a stiffness of 8,142 Pa with a more condensed and less porous structure, whereas Col3 had a stiffness of 735 Pa with a loose microstructure. Furthermore, both Col3 and Col10 supported DPSCs’ survival. Quantitative polymerase chain reaction showed Col3 promoted significantly higher von Willebrand factor (VWF) and CD31 expression after 7 and 14 d under endothelial differentiation conditions (P < 0.05), whereas Col10 enhanced the expression of dentin sialophosphoprotein (DSPP), alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), and collagen 1 (Col1) after 7, 14, and 21 d of odontogenic differentiation (P < 0.05). Hematoxylin and eosin and immunofluorescence (CD31 and vWF) staining revealed Col10+Col3+DPSCs+GFs enhanced pulp–dentin tissue regeneration. In conclusion, the collagen-based concentric construct modified by growth factors guided the specific lineage differentiation of DPSCs and promoted pulp–dentin tissue regeneration in vivo.

An Automatic Grading System for Orthodontically Induced External Root Resorption Based on Deep Convolutional Neural Network.

Orthodontically induced external root resorption (OIERR) is a common complication of orthodontic treatments. Accurate OIERR grading is crucial for clinical intervention. This study aimed to evaluate six deep convolutional neural networks (CNNs) for performing OIERR grading on tooth slices to construct an automatic grading system for OIERR. A total of 2146 tooth slices of different OIERR grades were collected and preprocessed. Six pre-trained CNNs (EfficientNet-B1, EfficientNet-B2, EfficientNet-B3, EfficientNet-B4, EfficientNet-B5, and MobileNet-V3) were trained and validated on the pre-processed images based on four different cross-validation methods. The performances of the CNNs on a test set were evaluated and compared with those of orthodontists. The gradient-weighted class activation mapping (Grad-CAM) technique was used to explore the area of maximum impact on the model decisions in the tooth slices. The six CNN models performed remarkably well in OIERR grading, with a mean accuracy of 0.92, surpassing that of the orthodontists (mean accuracy of 0.82). EfficientNet-B4 trained with fivefold cross-validation emerged as the final OIERR grading system, with a high accuracy of 0.94. Grad-CAM revealed that the apical region had the greatest effect on the OIERR grading system. The six CNNs demonstrated excellent OIERR grading and outperformed orthodontists. The proposed OIERR grading system holds potential as a reliable diagnostic support for orthodontists in clinical practice.

Efficient semi-analytic method for single tooth contact analysis of loaded spiral bevel gears

Accurately and fast calculation of single tooth load contact state of a gear pair is the basis for accurate calculation of multi-tooth load contact analysis. Therefore, this study proposed a semi-analytical quick single tooth load tooth contact analysis (Q-SLTCA) method. First, the ease-off tooth contact analysis (ease-off TCA) method was established, and a numerically stable initial contact stress distribution and contact ellipse analytical model was derived. Then, considering the influence of edge contact, the real-time division method of gear tooth slice was derived. Based on this, the equivalent principle of contact elliptical node and the load correction strategy were innovatively proposed. Then, the calculation method of the meshing characteristics of the tooth slice was established by coupling the boundary element method (BEM) with the equivalent cylindrical Hertz contact theory. The bending deformation, tooth root stress distribution, contact stress, contact deformation and meshing stiffness of the tooth slice were analyzed and calculated, and the instantaneous meshing stiffness of the single tooth was determined by combining the parallel method of the gear tooth stiffness. Finally, a single-tooth finite element method (FEM) meshing model was created for comparison with the method in this study, which verified the calculation accuracy and efficiency of the proposed method. This method can be easily developed into a quick multi-tooth load contact analysis algorithm, which can provide a new method for gear tooth crack and failure analysis.

Antibacterial biofilm efficacy of calcium hydroxide loaded on Gum Arabic nanocarrier: an in-vitro study

BackgroundAn innovative intracanal medication formulation was introduced in the current study to improve the calcium hydroxide (Ca(OH)2) therapeutic capability against resistant Enterococcus faecalis (E. faecalis) biofilm. This in-vitro study aimed to prepare, characterize, and evaluate the antibacterial efficiency of Ca(OH)2 loaded on Gum Arabic (GA) nanocarrier (Ca(OH)2-GA NPs) and to compare this efficiency with conventional Ca(OH)2, Ca(OH)2 nanoparticles (NPs), GA, and GA NPs.Materials and methodsThe prepared nanoparticle formulations for the tested medications were characterized using Transmission Electron Microscope (TEM) and Fourier-Transform Infrared Spectroscopy (FTIR). 141 human mandibular premolars were selected, and their root canals were prepared. Twenty-one roots were then sectioned into 42 tooth slices. All prepared root canals (n = 120) and teeth slices (n = 42) were divided into six groups according to the intracanal medication used. E. faecalis was inoculated in the samples for 21 days to form biofilms, and then the corresponding medications were applied for 7 days. After medication application, the residual E. faecalis bacteria were assessed using CFU, Q-PCR, and SEM. Additionally, the effect of Ca(OH)2-GA NPs on E. faecalis biofilm genes (agg, ace, and efaA) was investigated using RT-PCR. Data were statistically analyzed at a 0.05 level of significance.ResultsThe synthesis of NPs was confirmed using TEM. The results of the FTIR proved that the Ca(OH)2 was successfully encapsulated in the GA NPs. Ca(OH)2-GA NPs caused a significant reduction in the E. faecalis biofilm gene expression when compared to the control (p < 0.001). There were significant differences in the E. faecalis CFU mean count and CT mean values between the tested groups (p < 0.001) except between the Ca(OH)2 and GA CFU mean count. Ca(OH)2-GA NPs showed the least statistical E. faecalis mean count among other groups. SEM observation showed that E. faecalis biofilm was diminished in all treatment groups, especially in the Ca(OH)2-GA NPS group when compared to the control group.ConclusionsCa(OH)2 and GA nanoparticles demonstrate superior anti-E. faecalis activity when compared to their conventional counterparts. Ca(OH)2-GA NPs showed the best antibacterial efficacy in treating E. faecalis biofilm. The tested NP formulations could be considered as promising intracanal medications.

In vitro and in vivo evaluation of iRoot BP Plus as a coronal sealing material for regenerative endodontic procedures

ObjectivesTo investigate in vitro effects of a nanoparticle bioceramic material, iRoot BP Plus, on stem cells from apical papilla (SCAP) and in vivo capacity to induce pulp-dentin complex formation. Materials and methodsThe sealing ability of iRoot BP Plus was measured via scanning electron microscopy (SEM). SCAP were isolated and treated in vitro by iRoot BP Plus conditioned medium, with mineral trioxide aggregate (MTA) conditioned medium and regular medium used as controls, respectively. Cell proliferation was assessed by BrdU labeling and MTT assay and cell migration was evaluated with wound healing and transwell assays. Osteo/odontogenic potential was evaluated by Alizarin red S staining and qPCR. Pulp-dentin complex formation in vivo was assessed by a tooth slice subcutaneous implantation model.ResultsiRoot BP Plus was more tightly bonded with the dentin. There was no difference in SCAP proliferation between iRoot BP Plus and control groups (P > 0.05). iRoot BP Plus had a greater capacity to elevated cell migration (P < 0.05) and osteo/odontogenic marker expression and mineralization nodule formation of SCAP compared with MTA groups (P < 0.05). Furthermore, the new continuous dentine layer and pulp-like tissue was observed in the iRoot BP Plus group in vivo.ConclusionsiRoot BP Plus showed excellent sealing ability, promoted the migration and osteo/odontogenesis of SCAP and induced pulp-dentin complex formation without affecting the cell proliferation, which indicated iRoot BP Plus was a promising coronal sealing material in REPs.Clinical relevanceThe coronal sealing materials play crucial roles for the outcomes of REPs. This study showed that iRoot BP Plus has good coronal sealing and promote pulp-dentin complex formation compared with MTA, providing experimental evidences for the clinical application of iRoot BP Plus as a promising coronal seal material in REPs.

Mineralized Microgels via Electrohydrodynamic Atomization: Optimization and In Vitro Model for Dentin-Pulp Complex.

There is growing interest in the use of micro-sized hydrogels, including bioactive signals, as efficient platforms for tissue regeneration because they are able to mimic cell niche structure and selected functionalities. Herein, it is proposed to optimize bioactive composite microgels via electrohydrodynamic atomization (EHDA) to regenerate the dentin-pulp complex. The addition of disodium phosphate (Na2HPO4) salts as mineral precursors triggered an in situ reaction with divalent ions in solution, thus promoting the encapsulation of different amounts of apatite-like phases. Morphological analysis via image analysis of optical images confirmed a narrow distribution of perfectly rounded particles, with an average diameter ranging from 223 ± 18 μm to 502 ± 64 μm as a function of mineral content and process parameters used. FTIR, TEM, and EDAX analyses confirmed the formation of calcium phosphates with a characteristic Ca/P ratio close to 1.67 and a needle-like crystal shape. In vitro studies-using dental pulp stem cells (DPSCs) in crown sections of natural teeth slices-showed an increase in cell viability until 14 days, recording a decay of proliferation at 21 days, independent on the mineral amount, suggesting that differentiation is started, as confirmed by the increase of ALP activity at 14 days. In this view, mineralized microgels could be successfully used to support in vitro osteogenesis, working as an interesting model to study dental tissue regeneration.

The radiographic evaluation of 11 different resin composites.

Radiopacities of dental materials used in restorations are very important in making the radiographic diagnosis. Therefore, the aim of our study was to evaluate the radiopacity of five single-shade and six simplishade resin composites with digital technique. Five different single-shade (Charisma Topaz One, Omnichroma, Clearfil Majesty ES-2 Universal, Vittra APS Unique, ZenChroma) and six different simplishade resin composites (G-aenial A'CHORD, Essentia Universal, OptiShade, Estelite Asteria, Filtek Universal, Filtek Z250) were used. For each group, five disk-shaped resin composites of 1mm and 2mm thicknesses were prepared. As a control, tooth slices with 1mm and 2mm thicknesses and a 99.5% pure aluminum step-wedge were used. The samples, tooth slices, and a step-wedge were placed on a photostimulable phosphor plate. Digital radiographs were taken from 30 and 40cm distances (70 kVp, 7mA 0.28ms). The images were analyzed using ImageJ software to measure the mean gray values. Data were analyzed using SPSS 22 package program and Kruskal-Wallis H Test (p < 0.05). The highest radiopacity was seen in Filtek Universal at both distances and thicknesses. Omnichroma had the lowest radiopacity in all parameters. All specimens showed higher radiopacity than dentin. Except for Omnichroma 1 and 2mm thick, Clearfil Majesty ES-2 Universal 2mm thick, samples showed higher radiopacities than enamel (p < 0.05). The restorative materials tested were found to be more radiopaque than dentin. The samples passed the International Organization for Standardization for radiopacity values. The radiopacity values were affected by thickness and type of materials.

Analytical calculation of mesh stiffness for spiral bevel gears with an improved global tooth deformation model

The paper proposes an efficient and accurate analytical calculation model of time-varying mesh stiffness (TVMS) for the spiral bevel gear. Firstly, an enhanced numerical loaded tooth contact analysis (NLTCA) model that considers both the global tooth and local contact deformations is developed. Based on Tredgold's approximation, spiral bevel gears are sliced into a series of spur gears. An improved global tooth deformation model is developed by accounting for axial tooth deformation and the effect of non-contacting tooth slices. The influence coefficient method is utilized to determine the local contact deformation. Subsequently, based on the results of the NLTCA model, a detailed calculation procedure for determining the TVMS of spiral bevel gears is described. Finally, some numerical examples are provided to illustrate the efficiency and accuracy of the proposed model through comparisons to finite element analysis (FEA) results. The proposed model can achieve satisfactory accuracy without FEA modification. Furthermore, ignoring the effects of the non-contacting tooth slices will lead to excessive elastic deformation when the length of the contact area across the tooth width is significantly shorter than the tooth width.

Comparative study of the bond strength of ZirCAD Multi and ZirCAD Prime ceramics with different types of cements

Zirconia ceramic is a modern material used for different types of prosthetic constructions, characterized by high mechanical resistance and aesthetics. The main difficulties in treatment are related to ensuring a stable and durable bond between the ceramic and dentin. This study examined the bonding strength of ZirCAD Multi (3rd generation) and ZirCAD Prime (5th generation) ceramics when using different types of cements before and after sandblasting the surface of zirconia with Al2O3. For this purpose, an experimental setup was created by 3D printing, in which sintered ceramic cylinders were cemented to dentin slices of natural teeth with different types of cements. From the formed ceramic-dentin constructions, test specimens were cut with a microtome and tested for tensile strength. The results showed an increase in the strength of the bond after sandblasting from 1.1 MPa to 2.4 MPa for ZirCAD Multi and from 1.6 MPa to 3.3 MPa for ZirCAD Prime. Zirconia ceramic ZirCAD Prime (5th generation) showed higher adhesion resistance, with the strongest bond being with the Speed Cem Plus and Panavia V5 cements. With ZirCAD Multi, the maximum tensile strength was achieved with the Rely X Luting Plus and Speed Cem Plus cements. Optimal strength and bond resistance were registered between the new fifth-generation zirconia ceramic and composite cements with MDP (10-methacryloyloxydecyl dihydrogen phosphate) primers.

Prostaglandin E2-Transporting Pathway and Its Roles via EP2/EP4 in Cultured Human Dental Pulp

IntroductionProstaglandin E2 (PGE2) exerts biological actions through its transport pathway involving intracellular synthesis, extracellular transport, and receptor binding. This study aimed to determine the localization of the components of the PGE2-transporting pathway in human dental pulp and explore the relevance of PGE2 receptors (EP2/EP4) to angiogenesis and dentinogenesis. MethodsProtein localization of microsomal PGE2 (mPGES)synthase, PGE2 transporters (multidrug resistance-associated protein-4 [MRP4] and prostaglandin transporter [PGT]), and EP2/EP4 was analyzed using double immunofluorescence staining. Tooth slices from human third molars were cultured with or without butaprost (EP2 agonist) or rivenprost (EP4 agonist) for 1 week. Morphometric analysis of endothelial cell filopodia was performed to evaluate angiogenesis, and real-time polymerase chain reaction was performed to evaluate angiogenesis and odontoblast differentiation markers. ResultsMRP4 and PGT were colocalized with mPGES and EP2/EP4 in odontoblasts and endothelial cells. Furthermore, MRP4 was colocalized with mPGES and EP4 in human leukocyte antigen-DR-expressing dendritic cells. In the tooth slice culture, EP2/EP4 agonists induced significant increases in the number and length of filopodia and mRNA expression of angiogenesis markers (vascular endothelial growth factor and fibroblast growth factor-2) and odontoblast differentiation markers (dentin sialophosphoprotein and collagen type 1). ConclusionsPGE2-producing enzyme (mPGES), transporters (MRP4 and PGT), and PGE2-specific receptors (EP2/EP4) were immunolocalized in various cellular components of the human dental pulp. EP2/EP4 agonists promoted endothelial cell filopodia generation and upregulated angiogenesis- and odontoblast differentiation-related genes, suggesting that PGE2 binding to EP2/EP4 is associated with angiogenic and dentinogenic responses.

Preliminary comparison of the remineralization and desensitization effects of a novel mineralized ion-releasing toothpaste and commercially available competitive products

Background/purposeToothpaste plays an important role in brushing teeth to maintain oral hygiene and health. The purpose of this study was to develop a new toothpaste containing surface nanocrystal-rich dicalcium phosphate anhydrous (DCPA) powder and to investigate its effect on tooth samples. Materials and methodsThe innovative toothpaste (REALCaP®/Group R) was compared with two commercial toothpastes (BioRepair®/Group B and Sensodyne®/Group S). Brushing cycle tests were performed on bovine tooth slices coated with individual toothpaste and a control group without toothpaste (Group C). Microhardness, roughness, surface structure observation, and X-ray diffraction (XRD) were performed on cycle days 4, 7, and 14 to analyze the impact of the toothpastes on tooth samples. ReultsMicrohardness in the Group R was higher than that of the other groups regardless of the cycle days. Roughness in the Group R increased on days 4 and 7 but decreased on day 14. Roughness in the groups S and B increased with days. Microstructural observation revealed that most exposed dentinal tubules had been sealed in the Group R on day 14. Overlay thickness in the Group R was significantly higher than that in the groups S and B on days 4, 7, and 14. XRD analysis showed no hydroxyapatite (HA) peak in the Group S. The HA peak in the Group R was higher than that in the Group B on day 14. ConclusionThe innovative toothpaste has better properties than the commercially available products in terms of microhardness, roughness, and effectiveness in sealing dentinal tubules.

Modelo de trozo de dentina de células madre dentales en una construcción de fibrina-agarosa para la regeneración de la pulpa dental

Objectives: To implement a dentin slice model of mesenchymal stem cells derived from dental tissues in a fibrin-agarose construct for dental pulp regeneration. Material and Methods: MSCs derived from different oral cavity tissues were combined with a fibrin-agarose construct at standard culture conditions. Cell viability and proliferation tests were assayed using a fluorescent cell dye Calcein/Am and WST-1 kit. The proliferation assay was evaluated at 24, 48, 72, and 96 hours. Also, we assessed the dental pulp stem cells (DPSCs) cell morphology inside the construct with histological stains such as Hematoxylin and Eosin, Masson's trichrome, and Periodic acid–Schiff. In addition, we elaborated a tooth dentin slice model using a culture of DPSC in the fibrin–agarose constructs co-adhered to dentin walls. Results: The fibrin-agarose construct was a biocompatible material for MSCs derived from dental tissues. It provided good conditions for MSCs' viability and proliferation. DPSCs proliferated better than the other MSCs, but the data did not show significant differences. The morphology of DPSCs inside the construct was like free cells. The dentin slice model was suitable for DPSCs in the fibrin-agarose construct. Conclusion: Our findings support the dentin slice model for future biological use of fibrin-agarose matrix in combination with DPSCs and their potential use in dental regeneration. The multipotency, high proliferation rates, and easy obtaining of the DPSCs make them an attractive source of MSCs for tissue regeneration.

Proline-rich protein from S. mutans can perform a competitive mineralization function to enhance bacterial adhesion to teeth

A proline-rich region was found in Streptococcus mutans (S. mutans) surface antigen I/II (Ag I/II). The functions of this region were explored to determine its role in the cariogenic abilities of S. mutans; specifically, the proline-rich region was compared with human amelogenin. The full-length amelogenin genes were cloned from human (AmH) and surface antigen I/II genes from S. mutans. Then, the genes expressed and purified. We analyzed the structure and self-assembly ability of AmH and Ag I/II, compared their capacities to induce mineralization, and assessed the adhesion ability of S. mutans to AmH- and Ag I/II-coated tooth slices. AmH formed ordered chains and net frames in the early stage of protein self-assembly, while Ag I/II formed irregular and overlapping structures. AmH induced mineralization possessed a parallel rosary structure, while Ag I/II-induced mineralization is rougher and more irregular. The S. mutans adhesion assay indicated that the adhesion ability S. mutans on the Ag I/II-induced crystal layer was significantly higher than that on the AmH-induced crystal layer. S. mutans’ Ag I/II may have evolved to resemble human amelogenin and form a rougher crystal layer on teeth, which play a competitive mineralization role and promotes better bacterial adhesion and colonization. Thus, the cariogenic ability of S. mutans Ag I/II is increased.

Comparison of Two Obturation Techniques on Adhesion and Proliferation of Human Periodontal Ligament Fibroblasts

The present study aimed to compare the adhesion and proliferation of human periodontal ligament fibroblasts (hPDL) in transverse sections of the teeth sealed with two different obturation techniques, BioRoot RCS/hydraulic obturation (HO) and AH-Plus/continuous-wave condensation (CWC). The techniques were tested using an in vitro model to simulate the interaction between periodontal tissues and the materials. The root canals were instrumented and sterilized. A total of 15 samples were obturated with BioRoot RCS/HO and 15 samples with AH-Plus/CWC. Then, roots were sectioned to obtain obturated teeth slices, and hPDL cells were seeded onto the root slices. The results were obtained at intervals of 4 and 24 h for cell adhesion; and at 3,7,14, and 21 days for cell proliferation. Empty cell culture plates were use as controls. The cell adhesion was increased at 4 and 24 h for both groups, with an increased response observed in the BioRoot RCS/HO group (p&lt;0.05). The difference in cell proliferation was also found between experimental groups. After 14 days of culture, BioRoot RCS/HO group showed an increase response than control and AH-Plus/CWC groups (p&lt;0.05), and after 21 days both groups behaved better than control group, with an increased response observed in the BioRoot RCS/HO group. This study demonstrated that both root canal sealers allow the attach and growth of periodontal ligament fibroblasts, with an increased biological response in the BioRoot RCS/HO group.

A Comparative Evaluation of the Radiopacity of Contemporary Restorative CAD/CAM Blocks Using Digital Radiography Based on the Impact of Material Composition

Purpose The main purpose of this study was to assess the radiopacity of contemporary restorative computer-aided design (CAD)/computer-aided manufacturing (CAM) materials and the impact of material composition as measured by energy-dispersive X-ray spectrophotometry (EDX) on radiopacity. Materials and Methods Ten specimens of six CAD/CAM materials with 1 mm thickness were produced and then digitally radiographed with an aluminum (Al) step-wedge (SW) and 1 mm thick tooth slice. The specimen mean gray values (MGVs) were recorded in pixels and compared to an Al-SW, dentin, and enamel of equal thickness. For the elementary analysis of the composition of the materials, EDX was performed. Results The recorded MGVs ranged between 21.20 ± 4.94 and 238.5 ± 13.61 pixels. Materials were sorted according to the MGVs descendingly, Prettau, Vita Suprinity, Vita Enamic, Shofu, Pekkton, and BioHPP. Prettau and Vita Suprinity had significantly higher MGV than dentin and 1 mm thick Al. In comparison, Vita Enamic had a slightly higher value than dentin and 1 mm thick Al. Although Pekkton and BioHPP had MGV significantly lower than dentin and 1 mm thick Al, Shofu had a significantly lower value than dentin and nonsignificantly lower than 1 mm thick Al (p < 0.05). According to EDX analysis, the examined materials contained several components in varying quantities of radiopacity. Conclusions The radiopacity of only three studied materials exceeded the International Organization for Standardization's minimum standards (ISO).

A new effective mesh stiffness calculation method with accurate contact deformation model for spur and helical gear pairs

This paper proposes a new effective mesh stiffness calculation method for spur and helical gear pairs, which is explicitly formulated by an original FE-analytical slice model for tooth local contact deformation, efficient FE model for gear global deformation and mathematical programming approach for gear contact. The original FE-analytical slice model comprehensively integrates the advantages of FE method, Hertz contact theory and slice approach, which can address the displacement datum and elastic interaction of tooth slices effectively, so that tooth contact deformation is determined accurately. The geometry modeling of tooth slices is established and the pressure configuration in the contact region of each slice is prescribed by Hertz distribution. A specified FE programming is developed to derive the tooth contact flexibility matrix accurately. Thus, the mesh stiffness can be effectively calculated by using the proposed method with the FE-analytical slice model. The local contact deformation of gear tooth and mesh stiffness of gear pairs under ideal and error conditions are simulated. The accuracy and efficiency of the proposed method are validated against the ANSYS benchmark and common existing methods.

3D Visualization of Dynamic Cellular Reaction of Pulpal CD11c+ Dendritic Cells against Pulpitis in Whole Murine Tooth.

In dental pulp, diverse types of cells mediate the dental pulp immunity in a highly complex and dynamic manner. Yet, 3D spatiotemporal changes of various pulpal immune cells dynamically reacting against foreign pathogens during immune response have not been well characterized. It is partly due to the technical difficulty in detailed 3D comprehensive cellular-level observation of dental pulp in whole intact tooth beyond the conventional histological analysis using thin tooth slices. In this work, we validated the optical clearing technique based on modified Murray’s clear as a valuable tool for a comprehensive cellular-level analysis of dental pulp. Utilizing the optical clearing, we successfully achieved a 3D visualization of CD11c+ dendritic cells in the dentin-pulp complex of a whole intact murine tooth. Notably, a small population of unique CD11c+ dendritic cells extending long cytoplasmic processes into the dentinal tubule while located at the dentin-pulp interface like odontoblasts were clearly visualized. 3D visualization of whole murine tooth enabled a reliable observation of these rarely existing cells with a total number less than a couple of tens in one tooth. These CD11c+ dendritic cells with processes in the dentinal tubule were significantly increased in the dental pulpitis model induced by mechanical and chemical irritation. Additionally, the 3D visualization revealed a distinct spatial 3D arrangement of pulpal CD11c+ cells in the pulp into a front-line barrier-like formation in the pulp within 12 h after the irritation. Collectively, these observations demonstrated the unique capability of optical clearing-based comprehensive 3D cellular-level visualization of the whole tooth as an efficient method to analyze 3D spatiotemporal changes of various pulpal cells in normal and pathological conditions.

Experimental Bioactive Glass-Containing Composites and Commercial Restorative Materials: Anti-Demineralizing Protection of Dentin.

The purpose of this in vitro study was to investigate whether different types of experimental and commercial restorative dental materials can protect dentin against acid-induced softening. Experimental composites were prepared with a photocurable mixture of methacrylates and two types of bioactive glass (45S5 and a customized low-Na F-containing formulation). Human dentin samples were prepared from mid-coronal tooth slices and immersed in lactic acid solution (pH = 4.0) at 5 mm from set specimens of restorative material. After 4, 8, 12, 16, 20, 24, 28, and 32 days, surface microhardness of dentin samples and pH of the immersion solution were measured, followed by replenishing of the immersion medium. Microstructural analysis was performed using scanning electron microscopy. The protective effect of restorative materials was determined as dentin microhardness remaining statistically similar to initial values for a certain number of acid additions. Scanning electron microscopy showed a gradual widening of dentinal tubules and proved less discriminatory than microhardness measurements. To produce a protective effect on dentin, 20 wt% of low-Na F-containing bioactive glass was needed, whereas 10 wt% of bioactive glass 45S5 was sufficient to protect dentin against acid-induced demineralization. The anti-demineralizing protective effect of experimental and commercial restoratives on dentin was of shorter duration than measured for enamel in a previous study using the same experimental approach.