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This study aimed to comparatively evaluate the biomechanical behaviors of three types of dental implant restorations: a screw-and-cement-retained prosthetic system (SCRP); a cementless screw-retained prosthetic system (SRP); and a novel screwless hook-retained prosthetic system (HRP). Three-dimensional finite element analysis (FEA) was used to evaluate biomechanical behavior. A comparative study of three dental implant prostheses was performed under two loading conditions: a vertical load of 100 N and an oblique load of 100 N at an angle of 30°. Under both loading conditions, the maximum von Mises stress values in the dental implant using the HRP system were lower (21.33 MPa) than those of the SCRP system (32.91 MPa), and the stress distribution of the implant prosthetic components tended to be more favorable than that of the SCRP system. Thus, the results show that the performance of the HRP system was comparable to that of a conventional SRP system under the same conditions. Regarding stress distribution, the novel screwless HRP system presents a viable alternative implant prosthodontic system to the conventional SCRP system. [ABSTRACT FROM AUTHOR]

PurposeThe objective of this study was to conduct an in vitro comparative evaluation of polished and laserdimpled titanium (Ti) surfaces to determine whether either surface has an advantage in promoting the attachment of epithelial-like cells and fibroblast to Ti.Materials and methodsForty-eight coin-shaped samples of commercially pure, grade 4 Ti plates were used in this study. These discs were cleaned to a surface roughness (Ra: roughness centerline average) of 180 nm by polishing and were divided into three groups: SM (n=16) had no dimples and served as the control, SM15 (n=16) had 5-µm dimples at 10-µm intervals, and SM30 (n=16) had 5-µm dimples at 25-µm intervals in a 2 × 4 mm(2) area at the center of the disc. Human gingival squamous cell carcinoma cells (YD-38) and human lung fibroblasts (MRC-5) were cultured and used in cell proliferation assays, adhesion assays, immunofluorescent staining of adhesion proteins, and morphological analysis by SEM. The data were analyzed statistically to determine the significance of differences.ResultsThe adhesion strength of epithelial cells was higher on Ti surfaces with 5-µm laser dimples than on polished Ti surfaces, while the adhesion of fibroblasts was not significantly changed by laser treatment of implant surfaces. However, epithelial cells and fibroblasts around the laser dimples appeared larger and showed increased expression of adhesion proteins.ConclusionThese findings demonstrate that laser dimpling may contribute to improving the periimplant soft tissue barrier. This study provided helpful information for developing the transmucosal surface of the abutment.

(1) Background: To compare the degree of conversion of resin cores in various types of cavities and determine an effective irradiation method for achieving a higher degree of conversion. (2) Methods: Four different-sized cavities (narrow–shallow, narrow–deep, wide–shallow, and wide–deep) were simulated using a Teflon mold. The light irradiance reaching the bottom of each mold was measured by positioning a radiometer. The degree of conversion of the dual-cure resin core after irradiation (400 mW/cm2 for 20 s, 400 mW/cm2 for 40 s, and 800 mW/cm2 for 20 s) was measured using Fourier-transform near-infrared spectroscopy. (3) Results: The highest light irradiance was found at the bottom of wide–shallow cavities, followed by wide–deep, narrow–shallow, and narrow–deep ones (p < 0.001). In narrow cavities, irradiation at 800 mW/cm2 for 20 s led to a significantly higher degree of conversion (p < 0.001). In wide cavities, irradiation at 400 mW/cm2 for 40 s and 800 mW/cm2 for 20 s both led to a significantly higher degree of conversion (p < 0.001). (4) Conclusions: Less curing light reaches the bottom of cavities with a smaller diameter and greater depth. Providing a higher irradiance of light can induce a higher degree of conversion of resin composites in narrower cavities. [ABSTRACT FROM AUTHOR]

Although self-adhesive resin cements are convenient and less technique-sensitive materials for dental clinicians, they exhibit a lower degree of conversion due to acidic components in their composition. Supplementation of the initiator, accelerator, and activator in self-adhesive resin cements has been suggested to compensate for the lower degree of conversion. This study aimed to evaluate the effects of different combinations of self-curing initiators, self-curing activators, and accelerators on the degree of conversion (DC) of self-adhesive resin cements. A dual-cured self-adhesive resin was prepared using six combinations of initiators, activators, and accelerators. The change in the DC over time was evaluated with and without light curing. The film thickness, flow properties, and cytotoxicity of each formulation were assessed. The results showed that all supplemental components had an effect on increasing the DC, but a greater increase in the DC was observed in the following order: activator, accelerator, and initiator. The cytotoxicity of the resin cements was related to the DC values, as resin cements with lower DC values exhibited higher cytotoxicity. The film thickness met the ISO standards for all groups. The results suggest that utilizing an activator is the most effective approach to enhance the DC in self-adhesive resin cement and that cytotoxicity tended to increase with lower DC values, whereas film thickness and flow properties demonstrated no correlation with DC values. [ABSTRACT FROM AUTHOR]

The purpose of this study was to explore variables related to school belonging from a holistic perspective, including a large number of variables in one model, different to the traditional analytical method. Using 2015 data from the Program for International Student Assessment (PISA), we sought to identify variables related to school belonging by searching for hundreds of predictors in one model using the group Mnet machine learning technique. The study repeated 100 rounds of model building after random data splitting. After exploring 504 variables (384 student and 99 parent), 32 variables were finally selected after selection counts. Variables predicting a sense of school belonging were categorized as individual/parent variables (e.g. motivation to achieve, tendency to cooperative learning, parental support) and school-related variables (e.g. school satisfaction, peer/teacher relationship, learning/physical activities). The significance and implications of the study as well as future research topics were discussed. [ABSTRACT FROM AUTHOR]

Objective: To investigate the role of periodontitis in the risk of acute and chronic coronary syndrome with compounding factors, including sociodemographic factors and medication use. Methods: This retrospective cohort study used nationwide, population‐based data from the Korean National Health Insurance Service‐Health Screening Cohort database (514,866 individuals, 40–79 years). Propensity score matching was used for analysis. Information of subjects for 12 years was included. Socioeconomic and clinical factors were recorded and analysed. Results: The periodontitis group had a greater risk of overall acute coronary syndrome (hazard ratio [95% confidence interval] =1.25 [1.15, 1.35], p <.001) and non‐fatal acute coronary syndrome (1.26 [1.16, 1.37], p <.001). The hazard ratio for chronic coronary syndrome was higher in patients with periodontitis (1.35 [1.25, 1.46], p <.001). The cumulative incidence of both acute and chronic coronary syndrome gradually increased, and the hazard ratios reached 1.25 and 1.35 at the 12‐year follow‐up, respectively. Subgroup analysis revealed that periodontitis had a significantly greater link with acute coronary syndrome incidence in males, younger adults, smokers and subjects without hypertension (p <.01) and with chronic coronary syndrome incidence in smokers, subjects without hypertension and subjects without dyslipidaemia (p <.05). Conclusions: Periodontitis is associated with an increased risk of acute and chronic coronary syndrome. [ABSTRACT FROM AUTHOR]