High-Performance Dental Composites Based on Hierarchical Reinforcements.

Use of high-performance fibers such as poly(p-phenylene-2,6-benzobisoxazole) (PBO) improves the mechanical properties of dental fiber-reinforced composites (FRCs). However, the surfaces of high-performance fibers are relatively inert, and the interface with the resin matrix is poor. This has become a limitation restricting the performance of PBO FRCs in dentistry. Nanomaterials were introduced onto PBO fibers to construct various hierarchical reinforcements to obtain a dental FRC with higher flexural performance and optimized interface bonding. Four hierarchical reinforcements were constructed: PBO-ZnO nanoparticles (NPs), PBO-ZnO nanowires (NWs), PBO-ZnO NPs-cage silsesquioxane (POSS), and PBO-ZnO NWs-POSS. Performance following this optimized method was evaluated at macroscale and microscale levels, including measurement of the interfacial properties and mechanical properties of FRCs. The physicochemical characteristics of PBO fibers before and after modification were measured to determine the interfacial bonding mechanisms and to verify the connection between the microinterface and macromechanical properties. The cytotoxicity of the preferred PBO FRC was evaluated using the CCK8 assay. In comparison to other designs, the interfacial shear strength (IFSS) of PBO-ZnO NWs-POSS was the highest (29.31 ± 2.40 MPa). The corresponding FRC had the highest flexural strength under a static load (925.0 ± 39.2 MPa), the flexural modulus (39.39 ± 1.41 GPa) was equivalent to that of human dentin, and in vitro cytotoxicity was acceptable. The interfacial bonding mechanisms of PBO-ZnO NWs-POSS resulted from mechanical interlocking, chemical bonds, hydrogen bonds, and van der Waals forces. In summary, the PBO-ZnO NWs-POSS hierarchical reinforcement was introduced in dental FRCs and showed remarkable enhancement of the IFSS and flexural properties. We verified that the PBO-ZnO NWs-POSS hierarchical reinforcement was successful. This PBO FRC may be applied in dentistry as a new option for endodontic posts. Our study provides an interface design strategy for developing high-performance FRCs reinforced with high-performance fibers for dental applications.

[Analysis of caries experience and the dental treatments under general anesthesia in 103 cases of children with autism spectrum disorders].

Objective: To compare the caries experience and the kinds of dental treatment between children with autism spectrum disorders (ASD) and children without systemic disease who were all treated under general anesthesia. Methods: Totally 103 children with ASD who received dental treatments under general anesthesia in 13 professional dental hospitals around China from April to November 2016 were included in the present study. A group of 97 children without systemic disease, according to the age, gender and application propensity score matching method, were chosen as controls, who received dental treatments under general anesthesia between January 2015 to November 2018 in the same hospitals as the children with ASD. Decay missing filling tooth (DMFT/dmft, DMFT for permanent teeth and dmft for primary teeth) indices of two groups of children and the contents of the dental treatments under general anesthesia were analyzed. Results: No significant difference of DMFT/dmft index ï¼»M (Q 25, Q 75)ï¼½ was found between children with ASD group ï¼»0 (0, 3)/11(8, 14)ï¼½ and control group ï¼»0 (0, 3)/9(7, 13)ï¼½ (P>0.05). The average number of dental treatments under general anesthesia and the average number of endodontic treatment in children with ASD were 13 (11, 15) and 3 (2, 6) teeth respectively, while those in the control group were 12 (9, 14) and 2 (1, 4) teeth respectively, the differences were statistically significant (P<0.01, P<0.05). Conclusions: No significant difference was found between children with ASD and the normal controls who receive dental treatments under general anesthesia in DMFT/dmft index, but the treatment needs of children with ASD is relatively higher, and their tooth decay is relatively severer.

Programmed cell death in periodontitis: recent advances and future perspectives.

Periodontitis is a highly prevalent infectious disease, characterized by destruction of the periodontium, and is the main cause of tooth loss. Periodontitis is initiated by periodontal pathogens, while other risk factors including smoking, stress, and systemic diseases aggravate its progression. Periodontitis affects many people worldwide, but the molecular mechanisms by which pathogens and risk factors destroy the periodontium are unclear. Programmed cell death (PCD), different from necrosis, is an active cell death mediated by a cascade of gene expression events and can be mainly classified into apoptosis, autophagy, necroptosis, and pyroptosis. Although PCD is involved in many inflammatory diseases, its correlation with periodontitis is unclear. After reviewing the relevant published articles, we found that apoptosis has indeed been reported to play a role in periodontitis. However, the role of autophagy in periodontitis needs further verification. Additionally, implication of necroptosis or pyroptosis in periodontitis remains unknown. Therefore, we recommend future studies, which will unravel the pivotal role of PCD in periodontitis, allowing us to prevent, diagnose, and treat the disease, as well as predict its outcomes.

The role of Toll-like receptors in periodontitis.

Periodontitis is a common infectious disease. Recent studies have indicated that the progression of periodontitis may be regulated by interactions between host immunity and periodontopathic bacteria. Although periodontopathic bacteria can destroy periodontal tissue, a dysfunctional host immune response triggered by the bacteria can lead to more severe and persistent destruction. Toll-like receptors (TLRs), a type of pattern recognition receptor (PRR) that recognizes pathogens, have been implicated in host innate immune responses to periodontopathic bacteria and in the activation of adaptive immunity. TLR-targeted drugs may hold promise to treat periodontal disease. This review summarizes recent studies on the role of TLRs in periodontitis and discusses areas needing further research. We believe TLRs may be an effective biomarker for the prevention, diagnosis, and treatment of periodontitis in the near future.

Biomechanical characterization of a low density silicone elastomer filled with hollow microspheres for maxillofacial prostheses.

An ideal material for maxillofacial prostheses has not been found. We created a novel material: silicone elastomer filled with hollow microspheres and characterized its biomechanical properties. Expancel hollow microspheres were mixed with MDX4-4210 silicone elastomer using Q7-9180 silicone fluid as diluent. The volume fractions of microspheres were 0, 5, 15, and 30% v/v (volume ratio to the total volume of MDX4-4210 and microspheres). The microspheres dispersed well in the matrix. The physical properties and biocompatibility of the composites were examined. Shock absorption was the greatest by the 5% v/v composite, and decreased with increasing concentrations of microspheres. The density, thermal conductivity, Shore A hardness, tear and tensile strength decreased with increasing concentrations of microspheres, while elongation at break increased. Importantly, the tear strength of all composites was markedly lower than that of pure silicone elastomer. Cell viability assays indicated that the composite was of good biocompatibility. The composite with a volume fraction of 5% exhibited the optimal properties for use as a maxillofacial prosthesis, though its tear strength was markedly lower than that of silicone elastomer. In conclusion, we developed a novel light and soft material with good flexibility and biocompatibility, which holds a promising prospect for clinical application as maxillofacial prosthesis.

Subchronic toxicity studies of fenbendazole in rats.

The effects of prolonged exposure of rats to fenbendazole were investigated. Fenbendazole was given daily by gavage for 14 consecutive days. These dosages (3000, 500 or 50 mg/kg/d) produced reductions in body weight gains. Renal tubular hyperemia or hemorrhage and glomerular capsule dilation, increased serum creatinine and hepatocellular granular degeneration occurred at dosages of 500 and 3000 mg/kg/d. Renal tubular epithelial cell granular degeneration and tubular dilation, increased serum glutamic pyruvic transaminase, cardiac hemorrhage and granular degeneration also occurred at 3000 mg/kg/d.

[Fine needle aspiration cytology in the diagnosis of primary liver cancer].

From Dec. 1979 to Dec. 1984, 171 patients suspicious of primary liver cancer (PLC) were examined by fine needle aspiration cytology (FNAC). In this series, 148 patients were finally diagnosed as PLC. By FNAC, 133 of 148 patients showed positive cytology and 4 suspiciously positive cytology. The overall diagnostic accuracy was 92.6% There was no false positive. Neither spreading or bleeding were observed. The results show that FNAC examination, being simple, rapid and safe, could serve as a reliable way of diagnosing the suspected PLC.