Journal of Dental Sciences最新文献

Background/purpose: The use of finite element (FE) analysis in implant biomechanics offers many advantages over other approaches in simulating the complexity of clinical situations. The aim of this study was to perform an optimization analysis of dental implants with different thread designs in three types of bone quality.

Materials and methods: The three-dimensional FE model of a mandibular bone block with a screw-shaped dental implant and superstructure was simulated. In the optimization analysis, the design variables included the thread pitch and the thread depth of the implant. The objective was to minimize the displacement of the implant to the target value. Three FE models with different bone qualities (D2: better bone quality; D3: ordinary bone quality; D4: poor bone quality) were created.

Results: The FE results showed that the displacement of the implant and the stress of the cortical bone increased, while the Young's modulus of the cancellous bone decreased. In the D2 bone, changing the thread pitch and thread depth had little effect on cortical stress and implant displacement. However, in D3 and D4 bone, increasing thread depth reduced cortical stress by 40 % and implant displacement by at least 9 %.

Conclusion: Adjusted thread depth for D3 and D4 bone would reduce crestal bone stress and increase implant stability, but only a little alteration on crestal bone stress and implant stability for D2 bone.

Background/purpose: Dual-cure resin-cements are used for various dental restorations. However, whether the curing modes of these resin-cements influence gingival inflammation remains unclear. Hence, herein, we evaluated the effects of dual-cure resin-cement curing modes on gingival cytotoxicity and inflammatory responses.

Materials and methods: Specimens were prepared using two dual-cure resin-cements-RelyX Unicem 2 (RU) and G-CEM ONE (GO)-by light-cure or self-cure modes. Degree of conversion (DC) and monomer elution of the resin-cements were measured using Fourier-transform infrared spectroscopy and high-performance liquid chromatography, respectively. Human gingival fibroblasts (GFs) and macrophages were cultured on resin-cements, and inflammatory cytokine levels, intracellular reactive oxygen species (ROS) generation, and mitogen-activated protein (MAP) kinase activation were evaluated.

Results: Light-cured (LC) resin-cements exhibited significantly higher DC and lower monomer elution than did self-cured (SC) resin-cements. Triethyleneglycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA) were substantially eluted from RU and GO, respectively. Neither LC resin-cement exhibited cytotoxicity and enhanced pro-inflammatory cytokine expression in GFs and macrophages. However, both SC resin-cements significantly decreased cell numbers and promoted cellular inflammatory responses. SC generated higher intracellular ROS levels compared to that seen with LC, and different patterns of MAP kinase activation were observed between SC-RU and SC-GO.

Conclusion: Compared with LC dual-cure resin-cements, SC dual-cure resin-cements show stronger cytotoxicity and elicit greater inflammatory responses in gingival cells owing to residual monomers (e.g., TEGDMA and UDMA) by activating MAP kinases in GFs and macrophages. Clinicians should ensure adequate light irradiation during prosthesis cementation and make efforts to remove the excess cement.

Background/purpose: The performance of intraoral scanners (IOSs) relies on the operator's skills. However, whether operator experience influences IOS accuracy remains unclear. This study investigated the effect of operator experience on the trueness accuracy and time-based efficiency of IOSs.

Materials and methods: Thirty operators were equally divided into two groups on the basis of their IOS-handling experience. Each operator performed simulation scans of a maxillary model in a training dummy by using three IOSs: CEREC Omnicam, Primescan, and Aoralscan 3. A total of 90 scans were generated, and the scan time for image acquisition and the render time required for an IOS to generate a three-dimensional image were recorded. The trueness of each scan was calculated by comparing with a reference scan obtained from an industrial high-precision scanner. The t test and the ANOVA followed by the Tukey post hoc test were used to determine statistical differences. Significance was set at P < 0.01.

Results: For the three IOSs, no significant difference was noted in trueness accuracy, scan time, or render time between inexperienced and experienced operators. For both inexperienced and experienced operators, Omnicam had significantly less accuracy and longer scan time than did the other IOSs; the render time was significantly shorter for Aoralscan 3 than for the other IOSs.

Conclusion: Operator experience does not substantially influence the trueness accuracy and time-based efficiency of IOSs; these factors vary across IOS types. The render time for obtaining three-dimensional images is a significant feature for improving the time-based efficiency of IOSs.

Background/purpose: The local inflammatory microenvironment created by periodontitis negatively impacts periodontal tissue regeneration, necessitating the development of methods to enhance the regenerative capacity of stem cells. This study explored the regulatory role and underlying mechanism of miR-508-5p in the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs).

Materials and methods: The regulatory roles of miR-508-5p in osteogenic differentiation of hPDLSCs were investigated through its inhibition or overexpression. Expression of the sex-determining region Y-related HMG-box 11 (SOX11) and osteogenic markers was analyzed using Western blot and real-time PCR. Osteogenesis was measured using alizarin red S (ARS) staining and alkaline phosphatase (ALP) staining. A dual luciferase reporter assay was performed to confirm SOX11 as a target of miR-508-5p.

Results: During the osteogenic differentiation of hPDLSCs, miR-508-5p expression level gradually decreased, while that of SOX11 increased. miR-508-5p inhibition significantly promoted osteogenesis in hPDLSCs, while overexpression inhibited the process. SOX11 overexpression reversed the suppressive effects of miR-508-5p on the osteogenic differentiation of hPDLSCs. miR-508-5p downregulation significantly increased SOX11; a dual luciferase reporter assay provided evidence for their direct targeting.

Conclusion: miR-508-5p downregulation promotes the osteogenic differentiation of hPDLSCs by targeting SOX11.

Background/purpose: Complications, such as postoperative pneumonia, can occur after pediatric cardiac surgery; however, studies on related changes in perioperative oral bacterial counts are scarce. Herein, we investigated the changes in oral bacterial counts before and after surgery in infants who underwent cardiac surgery, as well as after oral care using an antiseptic mouthwash.

Materials and methods: A total of 102 infants who underwent congenital heart disease surgery were enrolled in this study. Preoperative oral care was provided using water and a sponge brush. Bacterial cultures were used to determine salivary bacterial counts before and after oral care. Postoperatively, the infants were randomized into a water group (WA group), benzethonium chloride mouthwash group (BZ group), or povidone-iodine mouthwash group (PV-I group), and their salivary bacterial counts, before and after oral care, were measured.

Results: The preoperative salivary bacterial colony counts did not change after oral care; however, the postoperative bacterial counts were significantly lower, possibly because of the use of systemic antibiotics. Bacterial counts before and after oral care were not significantly different between the WA and BZ groups; however, bacterial counts were significantly decreased in the PV-I group after oral care.

Conclusion: Overall, the results of this study show that systemic administration of antibiotics reduces postoperative salivary bacterial counts in infants undergoing cardiac surgery, and oral care with PV-I can further reduce bacterial counts.

Background/purpose: Revascularization procedures are used over apexification to treat teeth with necrotic pulp tissues and incomplete root formation. Clinically, inducing proliferation, migration, matrix deposition, and differentiation of stem cells from apical papilla (SCAPs) are critical for pulp regeneration. The study aimed to elucidate the impact of bone morphogenetic protein-4 (BMP-4) on plasminogen activation molecules and the osteogenic/odontogenic differentiation of SCAPs, as well as understand the related signaling mechanisms.

Materials and methods: SCAPs were exposed to BMP-4 with or without signal transduction inhibitors. Cell viability was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. mRNA levels were quantified using real-time PCR. Protein expression in SCAPs was analyzed through immunofluorescent staining or western blotting. Cellular protein production was measured with enzyme-linked immunosorbent assay.

Results: BMP-4 induced suppressor of mother against decapentaplegic (Smad)1/5/8 and Smad2/3 phosphorylation and activation. It also promoted higher expression of osteogenic and odontogenic markers, including Osterix, N-cadherin, and secreted protein acidic and rich in cysteine (SPARC), in SCAPs. Additionally, BMP-4 stimulated connective tissue growth factor (CTGF), plasminogen activator inhibitor-1 (PAI-1), and urokinase plasminogen activator receptor (uPAR) expression, but inhibited uPA expression and production in SCAPs, indicating its role in matrix remodeling and cell migration. Inhibition of Smad2/3 with SB431542 and Smad1/5/8 with LDN193189 attenuated the BMP-4-induced expression Osx, N-cadherin, CTGF, SPARC, uPAR and PAI-1.

Conclusion: These results indicate that BMP-4 stimulates the osteogenic and odontogenic differentiation of SCAPs by regulating matrix turnover and mineralization-related proteins. Furthermore, these processes are associated with the induction of Smad2/3 and Smad1/5/8 of SCAPs by BMP-4.

Background/purpose: The advent of digital technologies has significantly transformed the current dentistry, particularly in the fabrication of removable dental prostheses. A bibliometric analysis of literature may provide a direction of research hotspots and future trends in this field.

Materials and methods: Data were retrieved from Web of Science database for the analysis of literature on digital technologies for removable dental prostheses. Microsoft Excel was used for the descriptive statistics. VOSviewer was deployed for the analysis of published articles.

Results: A total of 457 published documents were identified from 2004 to 2023. The most frequently published article type was original article (n = 262, 57.33%). The number of annual publications and citations significantly increased from 2004 to 2023, respectively (P for trend <0.001). In addition, the significant increased number of publications and citations pre year affected by COVID-19 pandemic were noted (P < 0.002). Most articles were published in Journal of Prosthetic Dentistry (n = 141, 30.85%). The computer-aided design (CAD)/computer-aided manufacturing (CAM) and 3D printing technique were the frequent emphasized keywords in digital technologies for removable dental prostheses.

Conclusion: This bibliometric analysis revealed a growing research interest and technological progress in digital technologies for removable dental prostheses during past two decades. The enhancement of accuracy by CAD/CAM and 3D printing suggests a promising future for the application of these technologies in dental practice.

Background/purpose: Dental implants can restore both function and aesthetics in edentulous areas. However, the absence of cushioning mechanical behavior in implants may limit their clinical performance and reduce the long-term survival rates. This study aimed to establish an implant cushion mechanism that mimicked the natural periodontal ligament, utilizing the properties of composite hydrogels.

Materials and methods: In this study, we synthesized two composite hydrogels (HS and HSP groups) using hyaluronic acid (HA) and silk fibroin. We conducted static-constrained compression, creep, and porosity tests to assess the physical properties of these composite hydrogels. Finite element analysis (FEA) was employed to examine the effects of different thicknesses, permeabilities, and compression coefficients on the deformation of the hydrogels. The composite hydrogels were then applied within a novel dental implant, and the displacement performance of the implants, along with stress distribution on the alveolar bone, was evaluated using FEA.

Results: Regarding the mechanical performance of the composite hydrogels, increased permeability led to quicker displacement under compression. Thicker hydrogels with larger compression moduli influenced the biphasic behavior and deformation. The novel dental implants demonstrated biphasic sinking behavior under loading and rapid repositioning during unloading. When evaluating stress distribution on the alveolar bone under oblique loading, the HS and HSP implant groups showed a stress reduction of 10.3 % and 13.6 %, respectively, compared to commercial implant groups.

Conclusion: This study highlights that the biphasic nature of solid and liquid phases is crucial when incorporating a cushioning mechanism into implants to replicate the characteristics of the periodontal ligament.