Effect of Light Irradiance and Curing Duration on Degree of Conversion of Dual-Cure Resin Core in Various Cavities with Different Depths and Diameters.

(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.

The Effect of the Initiator/Activator/Accelerator Ratio on the Degree of Conversion, Film Thickness, Flow, and Cytotoxicity of Dual-Cured Self-Adhesive Resin Cements.

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.

Effect of erbium, chromium-doped: yttrium, scandium, gallium, and garnet laser-assisted periodontal therapy using radial firing tip during early healing period: a randomized controlled split-mouth clinical trial.

BACKGROUND: This study aimed to demonstrate the efficacy of erbium, chromium-doped:yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser-assisted nonsurgical periodontal therapy in periodontitis patients during 8 weeks of healing. METHODS: A split-mouth, single-blinded, randomized controlled clinical trial was conducted on 12 patients diagnosed with stage III/IV periodontitis and had a minimum of two teeth with probing pocket depth (PPD) > 5 mm in at least two quadrants. Upon randomization, each quadrant was assigned for conventional scaling and root planing (SRP) procedure or laser-assisted therapy (SRP + laser) using radial firing tip (RFPT 5, Biolase). Clinical measurements and gingival crevicular fluid collection were performed for statistical analysis. RESULTS: In the initial statistical analysis on the whole subject teeth, modified gingival index (MGI) reduction was greater in test group at 1(P = 0.0153), 4 (P = 0.0318), and 8 weeks (P = 0.0047) compared to the control in the same period. PPD reduction at 4 weeks in test group was -1.67 ± 0.59 showing significant difference compared to the control (-1.37 ± 0.63, P = 0.0253). When teeth with mean PPD ≥5 mm were sorted, MGI decrease was significantly greater in test group at 1 (P=0.003) and 8 week (P=0.0102) follow-ups. PPD reduction was also significantly greater in test group at 4 week period (-1.98 ± 0.55 vs -1.58 ± 0.56, test vs control, P=0.0224). CONCLUSIONS: Er,Cr:YSGG-assisted periodontal therapy is beneficial in MGI and PPD reductions during early healing period.

Translucency and Strength of Lithium Disilicate for Computer-Aided Design and Manufacturing at Different Thermal Temperatures and Thicknesses: An In Vitro Study.

To manufacture dental restorations composed of lithium disilicate (LD) through the computer-aided design and manufacturing (CAD/CAM) process, thermal refinement is an essential process that can affect the optical and mechanical properties of ceramics. In this study, we aimed to evaluate the translucency and flexural strength of lithium disilicate glass-ceramic for CAD/CAM using different thermal refinement schedules and thicknesses by measuring the total transmission of light through the specimen and calculating the peak load of the specimen until fracture in a piston-on-three-ball test, respectively. The results showed that a lower translucency was exhibited in thicker specimens, and the flexural strength decreased in the order of 1.0, 0.5, and 2.0 mm (p < 0.05). The lithium disilicates thermally refined at a heat of 820 degrees were shown to have the highest biaxial flexural strength (p < 0.05). These findings suggest that it is possible to adjust transparency and strength according to the clinical situation by choosing an appropriate thickness and thermal refinement process.

Reliability of implant stability measuring devices depending on various clinical conditions: an in vitro study.

PURPOSE: The aim of this study was to evaluate the reliability of implant stability measuring devices depending on the location of the implant and the position of the patient. MATERIALS AND METHODS: Six implants were installed in different dentate sextants of six artificial bone models. Implant stability was measured in three conditions of the bone model (without mounting on a phantom head, mounted on a phantom head in supine position, and mounted on a phantom head in upright position). A resonance frequency analysis device (Osstell) and two damping capacity analysis devices (Periotest and Anycheck) were used to measure implant stability. The values measured outside the phantom head were treated as controls, and the values inside the phantom head were compared using an independent t-test. RESULTS: Osstell showed different results in two of the six divisions in both the supine and upright positions compared to outside of the mouth (P < .05). Periotest showed different results in all six parts in the supine position and in five parts in the upright position compared to outside of the mouth (P < .05). While Anycheck showed different results in five areas in the supine position compared to outside of the mouth, it showed different results in only one area in the upright position (P < .05). CONCLUSION: In the difficult implant position for the operator to access, the implant stability measuring devices show less reliability. The accessibility of implant is greatly affected in the order of Osstell, Anycheck, and Periotest.

Bioactive Nonthermal Biocompatible Plasma Enhances Migration on Human Gingival Fibroblasts.

This study hypothesizes that the application of low-dose nonthermal biocompatible dielectric barrier discharge plasma (DBD-NBP) to human gingival fibroblasts (HGFs) will inhibit colony formation but not cell death and induce matrix metalloproteinase (MMP) expression, extracellular matrix (ECM) degradation, and subsequent cell migration, which can result in enhanced wound healing. HGFs treated with plasma for 3 min migrate to each other across the gap faster than those in the control and 5-min treatment groups on days 1 and 3. The plasma-treated HGFs show significantly high expression levels of the cell cycle arrest-related p21 gene and enhanced MMP activity. Focal adhesion kinase (FAK) mediated attenuation of wound healing or actin cytoskeleton rearrangement, and plasma-mediated reversal of this attenuation support the migratory effect of DBD-NBP. Further, this work performs computer simulations to investigate the effect of oxidation on the stability and conformation of the catalytic kinase domain (KD) of FAK. It is found that the oxidation of highly reactive amino acids (AAs) Cys427, Met442, Cys559, Met571, Met617, and Met643 changes the conformation and increases the structural flexibility of the FAK protein and thus modulates its function and activity. Low-dose DBD-NBP-induces host cell cycle arrest, ECM breakdown, and subsequent migration, thus contributing to the enhanced wound healing process.

Clinical Validation of Dental Implant Stability by Newly Designed Damping Capacity Assessment Device during the Healing Period.

Background and Objectives: To evaluate the stability of a dental implant and the effectiveness of a newly designed damping capacity assessment device by improving the number of blows and strength evaluated by a prospective clinical study. Materials and Method: The stability of dental implants was measured in 50 implants in a total of 38 patients. Measurements were performed using Anycheck and Periotest M devices, twice in total, divided into buccal and lingual directions. In addition, measurements were performed on the day of surgery, two weeks, one month, two months, and three months after surgery for a total of five times. After the standardization of the measured values, the differences and changes over time for each device were observed. Result: No difference in standardized values between the two devices was observed at any time point. In both devices, stability decreased at two weeks postoperatively but gradually increased thereafter. No differences were observed in the values according to the measurement direction. Conclusions: The damping capacity of Anycheck was similar to that of Periotest M. After a slight decrease in stability two weeks after implant placement, implant stability increased over time.

Evaluation of microleakage and push-out bond strength of various composite resins for sealing the screw-access channel in implant-supported restorations.

STATEMENT OF PROBLEM: Microleakage and loss of the composite resin sealing the screw-access channel are frequent complications of screw-retained implant-supported prostheses. How the screw-access channel should be best restored to reduce such complications is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the microleakage and bond strength of 3 types of composite resins (flowable, packable, and bulk-fill) with or without a bonding agent treatment to seal the screw-access channel of 2 types of restorative materials (zirconia and Co-Cr alloy) with or without thermocycling. MATERIAL AND METHODS: In total, 240 yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) specimens (IPS e.max ZirCAD) and 240 Co-Cr alloy (Vera PDS) specimens were prepared with a Ø3×3-mm cylindrical cavity at the center to simulate the screw-access channel. Three types of composite resins (flowable, packable, and bulk-fill resin) (Filtek Z350 XT Flowable Restorative, Filtek Z350 XT Universal Restorative, and Filtek One Bulk Fill Restorative) were applied to restore the access channel of the zirconia and Co-Cr specimens with or without a bonding agent (Single Bond Universal Adhesive). Microleakage and push-out bond strength were determined and compared by dividing the specimens into experimental groups with or without thermocycling (1000 times with 30 seconds at 5 ±2 °C and 55 ±2 °C). The results were analyzed by using a 1-way ANOVA and 4-way ANOVA. Adjustment for multiple comparisons was made with the Tukey Honestly Significant Difference (HSD) test. RESULTS: The specimens subjected to thermocycling showed a lower bond strength (P<.001) and higher microleakage (P<.001) than specimens stored in a constant-temperature water bath. Specimens treated with bonding agents showed a higher bond strength (P<.001) and lower microleakage (P<.001) than specimens not treated with a bonding agent. Higher bond strengths were observed in the order of bulk-fill resin, packable resin, and flowable resin (P<.001). Packable resin showed higher microleakage than flowable resin and bulk-fill resin (P<.05). No significant difference in microleakage was found between the flowable resin and bulk-fill resin (P>.05). CONCLUSIONS: Higher bond strengths were observed in the order of bulk-fill resin, packable resin, and flowable resin. Less microleakage was observed in the flowable resin and bulk-fill resin than in the packable composite resin. Bonding agent treatment was effective in increasing bond strength and decreasing microleakage. Zirconia and Co-Cr showed a bond strength similar to that of composite resins, but zirconia showed higher microleakage than Co-Cr. Restoring the screw-access channel with the bulk-fill resin should increase bond strength and reduce microleakage.

Exploration of Variables Predicting Sense of School Belonging Using the Machine Learning Method-Group Mnet.

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.

Guided Bone Regeneration with a Nitric-Oxide Releasing Polymer Inducing Angiogenesis and Osteogenesis in Critical-Sized Bone Defects.

Synthetic scaffolds, as bone grafts, provide a favorable environment for the repair and growth of new bone tissue at defect sites. However, the lack of angio- and osteo-induction limits the usefulness of artificial scaffolds for bone regeneration. Nitric oxide (NO) performs essential roles in healing processes, such as regulating inflammation and addressing incomplete revascularization. In this study, a polymer capable of controlled NO release is developed to promote the osteogenic capacity in artificial scaffolds. The biological efficiency of the NO compound is assessed by its effect on pre-osteoblasts and macrophages in vitro and the extent of vascularization and bone formation in the calvaria defect model in vivo. The compound does not inhibit cell adhesion or proliferation. NO treatment significantly increases both alkaline phosphatase activity and mineralization in pre-osteoblasts. Macrophages treated with NO secrete high levels of anti-inflammatory factors and adopt the pro-regenerative phenotype. In the critical-sized defect model, the collagen scaffold containing the NO compound enhances neovascularization and bone formation. The developed NO-releasing system promotes osteogenesis and regeneration of damaged bone tissue. As the multiple functions of NO involve macrophage modulation and angiogenesis, such release systems may be valuable for guiding bone regeneration in critical-sized defects.

Risk of acute and chronic coronary syndrome in a population with periodontitis: A cohort study.

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.

Pre-contoured reconstruction plate fabricated via three-dimensional printed bending support.

A mandibular continuity defect can be repaired using either a prosthetic device or autogenous bone. A titanium reconstruction plate can be used with a localized or vascularized flap over the defect of the mandible. Unfortunately, the plate may fail due to plate exposure, screw loosening, fracture, or infection, and will need to be removed. Plate exposure though the skin or mucosa is one of the main reasons for failure. In the present work, the authors introduced a lingually positioned reconstruction plate fabricated via three-dimensional printed bending support. This custom reconstruction plate can avoid plate re-exposure as well as reduce surgical errors and operation time.

Shift work sleep disorder is closely associated with an increased risk for periodontal disease.

AIM: This study aimed to investigate the association between work patterns and periodontal disease. MATERIALS AND METHODS: Data were collected from the Korea National Health and Nutrition Examination Survey between 2007 and 2012, and data from 22,508 subjects aged ≥19 years were included. An individual's work pattern was classified as either daytime or shift work. Sleep duration was categorized into three ranges: ≤5, 6-8, and ≥9 h/day. A multivariate logistic regression model was used to determine the adjusted odds ratio (OR) for CPI (Community Periodontal Index) ≥3. The CONTRAST statement was used to show the interaction effect of work patterns and sleep duration. RESULTS: The adjusted OR of shift work was 2.168 (CI: 1.929-2.438, p < .0001). Participants who sleep ≤5 or ≥9 h/day showed ORs 0.735 and 0.663, respectively (p = .0181). Interaction effect analysis revealed that the work pattern had a strong influence on periodontal condition when combined with the sleep amount. Shift workers with ≤5 or ≥ 9 h of sleep showed significantly increased ORs for CPI ≥3 (2.1406 and 2.3251, respectively, p < .0001). The ORs for daytime workers were comparable to the original values (≤5: 0.7348, p = .0292; ≥9: 0.6633, p = .0428). CONCLUSION: Altered sleep patterns caused by shift work have more influence on periodontal disease than sleep duration.

Evaluation of the Age- and Sex-Related Changes of the Osteogenic Differentiation Potentials of Healthy Bone Marrow-Derived Mesenchymal Stem Cells.

Background andObjectives: Human bone marrow-derived mesenchymal stem cells (BMSCs) are promising sources for cell-based regenerative therapy. The purpose of the present study was to elucidate the roles of age and sex on the cellular viability and osteogenic potential of BMSCs cultured in osteogenic media. Materials and Methods: Human BMSCs were isolated and expanded from 3 age groups-20s, 30s, and 50s-from both sexes. The total number of aspirates was ten, and each subgroup had five for 20s (two females and three males), three for 30s (one female and two male), and two for 50s (one female and one male). Analyses of the cell morphology, the cell viability, the expression of the stem cell marker SSEA-4, the secretion of human vascular endothelial growth factor (VEGF), the expression of Runx2 and collagen I, the metabolic activity, and the formation of mineralization nodules were performed. Results: No significant differences were found in the cell viability of human BMSCs cultured in osteogenic media among the different age groups. There were no significant differences in the expression of SSEA among the age groups or between males and females. There were no significant differences in the secretion of human VEGF between males and females. No significant differences in Runx2 or collagen I expression were noted by age or gender. Moreover, no significant differences were shown in osteogenesis by alizarin red staining. Conclusions: The human BMSCs showed no age-related decreases in cellular viability or osteogenic differentiation potential.

A long-term longitudinal study of the osteoarthritic changes to the temporomandibular joint evaluated using a novel three-dimensional superimposition method.

The aim of this study was to assess the changes in individual condyles from 5 to 8 years in patients with temporomandibular joint (TMJ) osteoarthritis using 3-dimensional cone beam computed tomography (3D CBCT) reconstruction and superimposition. To assess the longitudinal TMJ changes, CBCT was performed at initial (T0) and final (T2) timepoints that were at least 5 years apart and at a middle (T1) timepoint. To improve the accuracy, we used a novel superimposition method that designated areas of coronoid process and mandibular body. The differences in the resorption and apposition amounts were calculated between each model via maximum surface distances. The greatest resorption and apposition observed were - 7.48 and 2.66 mm, respectively. Evaluation of the changes in each condyle showed that osteoarthritis leads to both resorption and apposition. Resorption was mainly observed in the superior region, while high apposition rates were observed (in decreasing order) in the posterior, lateral, and anterior regions. The medial parts showed greater apposition than the lateral parts in all regions. Our superimposition method reveals that both resorption and apposition were observed in condyles with TMJ osteoarthritis, and resorption/apposition patterns depend on the individual condyle and its sites.

Horizontal alteration of anterior alveolar ridge after immediate implant placement: A retrospective cone beam computed tomography analysis.

PURPOSE: The aim of this study was to evaluate the labio-lingual alterations of the alveolar bone where the implant was placed immediately after tooth extraction. MATERIALS AND METHODS: Implants were placed immediately after tooth extraction on anterior alveolar ridges in the maxilla and mandible. The pin-guide system was used to help determine the location and path of implants during the surgical process. The horizontal distance from implants to the outer border of alveolar bone was measured at the rim and middle of the implants in the cone beam computed tomography images. The alteration of alveolar bone was evaluated comparing the horizontal distances measured immediately after surgery and 3 months after surgery. RESULTS: The results show that more resorption occurred towards the labial bone than the lingual bone in the maxilla. A similar amount of labial and lingual bone resorption was observed in the mandible. CONCLUSION: Considering the horizontal alteration of alveolar bone, labio-lingual positioning of the implant towards the lingual bone in the maxilla and at the center of the alveolar ridge in the mandible is recommended when it is placed immediately after tooth extraction.

Influence of the Depth of the Convolutional Neural Networks on an Artificial Intelligence Model for Diagnosis of Orthognathic Surgery.

The aim of this study was to investigate the relationship between image patterns in cephalometric radiographs and the diagnosis of orthognathic surgery and propose a method to improve the accuracy of predictive models according to the depth of the neural networks. The study included 640 and 320 patients requiring non-surgical and surgical orthodontic treatments, respectively. The data of 150 patients were exclusively classified as a test set. The data of the remaining 810 patients were split into five groups and a five-fold cross-validation was performed. The convolutional neural network models used were ResNet-18, 34, 50, and 101. The number in the model name represents the difference in the depth of the blocks that constitute the model. The accuracy, sensitivity, and specificity of each model were estimated and compared. The average success rate in the test set for the ResNet-18, 34, 50, and 101 was 93.80%, 93.60%, 91.13%, and 91.33%, respectively. In screening, ResNet-18 had the best performance with an area under the curve of 0.979, followed by ResNets-34, 50, and 101 at 0.974, 0.945, and 0.944, respectively. This study suggests the required characteristics of the structure of an artificial intelligence model for decision-making based on medical images.

Multi-functional effects of a nitric oxide-conjugated copolymer for accelerating palatal wound healing.

The damaged site of a palatal wound is difficult to repair and often remains unclosed due to failure of the healing process, which occurs in inadequate environments of the oral cavity. Nitric oxide (NO) has effective functions in repairing damaged tissues, but it has a limitation due to short lifetime and rapid diffusion. Here, we synthesize a donor to deliver exogenous NO gas and verify its therapeutic effect for the palatal wound healing, which is known to take longer for healing due to the poor environment of warm saliva containing millions of microbes. NO was incorporated into the synthetic polymer and the NO-donors were characterized based upon their ability to release NO. The NO donor not only reduced cytotoxicity but also increased migration and proliferation in gingival fibroblasts. Moreover, the angiogenic capacity was improved by NO-donor treatment. In the palatal wound model, the NO-treatment was involved in enhancing the biological responses associated with wound healing. This strategy suggests that treatment involving controlled NO release may have beneficial effects on palatal wound healing.

Three-Dimensional Reproducibility of the Soft Tissue Landmarks Taken by Structured-Light Facial Scanner in Accordance with the Head Position Change.

The aim of this study was to evaluate the three-dimensional reproducibility of the structured-light facial scanner according to the head position change. A mannequin head was used and angle of the mannequin's axis-orbital plane to the true horizontal plane was adjusted to +10, +5, 0, -5, and -10°. Facial scanning was conducted 30 times, respectively, and 150 3D images were obtained. Reoriented landmarks of each group were compared and analyzed. Reproducibility decreased as the distance from the facial center increased. Additionally, the landmarks below showed lower reproducibility and higher dispersion than landmarks above. These differences occurred mainly in the anteroposterior direction as opposed to other directions. Positive inclination of the head position showed superior reproducibility compared to a negative inclination. This study showed that reproducibility of a structured-light scanner could be varied depending on the head position. Inaccuracies of landmarks in the anteroposterior direction are greater than in other directions. This means that evaluations of the profile using a structured-light scanner should be made carefully. Therefore, the proper head position should be set to ensure the accuracy of the image.

Modulation of Lithium Disilicate Translucency through Heat Treatment.

The aim of this study was to present a control method for modulating the translucency of lithium disilicate ceramics through thermal refinement. Identical lithium disilicate blocks were thermally refined using four different heat treatment schedules, and the microstructure, translucency, and flexural strength of the ceramics were investigated in detail by SEM, spectroscopy, and a piston-on-three-ball test. The results showed that ceramics treated under higher heat had larger grains, with an average size between 240 and 1080 nm. In addition, a higher transmittance of all wavelengths was observed in ceramics treated under lower heat, and the transmittance in the 550 nm wavelength ranged from 27 to 34%. The results suggest that the translucency of ceramics can be modified through thermal refinement under two conditions: (1) the particle size of the ceramic is small enough to achieve minimal grain-boundary light scattering, and (2) the percentage of particles allowing visible light transmission is altered by the heat treatment.