Novel Polymer-Based Organic/c-Si Monolithic Tandem Solar Cell: Enhanced Efficiency using Interlayer and Transparent Top Electrode Engineering.

Tandem solar cells which are electrically connected with various photoactive materials have the potential to solve the current challenges by exceeding the theoretically limited efficiency of single junction solar cells. Here the first monolithic organic/silicon tandem cell is reported based on a semitransparent polymer on a crystalline silicon (c-Si) substrate. Herein, experimental results are presented for four-terminal (4-T) and monolithic two-terminal (2-T) organic/c-Si tandem cells using organic cells with an inverted n-i-p structure and c-Si cells with an n-type TOPCon structure with detailed analysis. The best 4-T tandem cell efficiency is 15.22%, and 2-T results show that the top (organic) and bottom (c-Si) cells are electrically connected by an open-circuit voltage over 1.4 V. Further, a simulated efficiency of over 20% using the organic/c-Si tandem is achieved, implying the tandem efficiency can be enhanced through further improvement of electric and optical characteristics with the optimization.

Age-related long-term posttreatment occlusal and arch changes.

OBJECTIVE: To evaluate differences in long-term postretention changes between adolescents and adults. MATERIALS AND METHODS: The sample included 96 subjects, 51 adolescents and 45 adults (14.2 +/- 0.8 and 21.5 +/- 6.8 years of age, respectively, at the end of treatment) retained for 3 years and followed approximately 16 years post treatment, who were randomly selected from two private practices. Prior to treatment, 38 and 58 had Class I and Class II malocclusions, respectively. RESULTS: With the exception of adult midlines, all of the occlusal variables (overjet [0.50-0.77 mm], overbite [0.85-0.95 mm], the maxillary incisor irregularity [0.69-0.80 mm], the mandibular incisor irregularity [0.85-1.50 mm] and the PAR score [0.86-1.92 points]) showed significant increases over time. Adolescents consistently showed greater increases of the occlusal variables than adults, with mandibular incisor irregularity and the PAR index attaining statistically significant (P < .05) levels. Arch length and mandibular intercanine width showed statistically significant decreases over time in both groups; maxillary intercanine and intermolar widths did not change significantly. Overjet increased significantly more in Class II patients than in Class I patients, whereas Class I patients showed significantly greater decreases in mandibular intermolar width than Class II patients. CONCLUSIONS: Over the 16-year posttreatment period, adolescents showed significantly greater increases in mandibular incisor irregularity, and the PAR index than adults. Treated Class I patients demonstrated less increase in overjet and greater decreases in mandibular intermolar width than Class II patients.

Repair of rabbit radial bone defects using bone morphogenetic protein-2 combined with 3D porous silk fibroin/ß-tricalcium phosphate hybrid scaffolds.

Our study aimed to investigate the effect of bone morphogenetic protein-2 (BMP-2) bound to silk fibroin and ß-tricalcium phosphate (SF/ß-TCP) hybrid on the healing of critical-size radial defects in rabbits. A 15-mm critical-size defect was induced at mid-diaphysis in the left radius of 20 New Zealand white rabbits (average age, 3.5 months; weight, 2.5-3.0 kg). The animals were randomized into Group 1 (SF/ß-TCP combined with BMP-2), Group 2 (SF/ß-TCP alone), and Group 3 (nothing implanted). Radiographs were obtained every 2 weeks and euthanasia was performed after 8 weeks for visual, radiological, micro-computed tomography (micro-CT), and histological studies. Eight weeks after implantation (SF/ß-TCP combined with BMP-2), radiographs showed that new bone formed on the surface of the implant and had bridged the defect in Group 1. Micro-CT imaging also confirmed the formation of new bone around the implant, and the newly formed bone was quantified. Histological examination revealed newly formed bone in the implanted area. Meanwhile, there was no formation of new bone in Group 3. Among the groups, most active formation of new bones was found in Group 1, while there was no difference between Group 2 and Group 3. Based on these results, we concluded that BMP-2-SF/ß-TCP showed significant improvement in healing of critical-size defects. Therefore, the combination of BMP-2 and SF/ß-TCP would be useful in the field of bone tissue engineering.

Effect of simulated pulpal pressure on dentin bond strength of self-etching bonding systems.

PURPOSE: To evaluate in vitro the influence of dentin perfusion on dentin bond strengths of etch and rinse and self-etch adhesives. METHODS: 64 extracted human molars were ground flat and resin composite (Brilliant) was bonded using the following bonding systems (each n=16): OptiBond FL including phosphoric acid etching (OFL+), OptiBond FL without phosphoric acid etching (OFL-), Clearfil SE-Bond (CSE) and Prompt L-Pop (LP). In each bonding system, half of the specimens (n=8) were bonded without (PP-) and half with (PP+) simulated intrapulpal pressure. After water storage (37 degrees C, 24 hours), a 1 mm thick slice was cut vertically from the middle of each sample. Microtensile bond strength (microTBS) was determined and the debonded surfaces were investigated in SEM for the mode of failure. Statistical significance was determined by ANOVA, Tukey-test, and t-test (P= 0.05). RESULTS: Mean microTBS measured were (MPa +/- SD): OFL+/PP- 58.6 (5.8), OFL+/PP+ 38.1 (3.8), OFL-/PP- 37.9 (3.7), OFL-/PP+ 33.3 (3.5), CSE/PP- 41.1 (4.1), CSE/PP+ 39.0 (4.4), LP/PP- 35.8 (6.4), LP/PP+ 29.0 (4.8). The presence of PP resulted in a decrease of microTBS in all bonding systems, which reached significance in OFL+ (P< 0.0001), OFL- (P= 0.023) and LP (P= 0.032). Both, with and without PP, the bonding systems showed significant differences in bond strength (ANOVA: P< 0.0001).

Modified oligosaccharides as potential dental plaque control materials.

Metabolic acids produced by oral pathogens demineralize tooth surfaces, leading to dental caries. Glucosyltransferases are the key factor in this process. We synthesized various modified oligosaccharides and tested them for their inhibitory effects on glucosyltransferase activity. Oligosaccharides were produced using a mixed-culture fermentation of Lipomyces starkeyi and Leuconostoc mesenteroides and then further modified as iron- and sulfate-oligosaccharides. Iron- and sulfate-oligosaccharides reduced glucosyltransferase activity of Streptococci from 17% to 43% and prevented the formation of insoluble biomass on the surface of glass vials or stainless steel wires in the presence of sucrose. They also reduced the growth and acid productions of oral pathogens including S. mutans, S. sobrinus, Eikenella corrodens, Prevotella intermedia, and Actinobacillus actinomycetemcmitans.

Bond strength of adhesive/composite combinations to dentin involving total- and self-etch adhesives.

PURPOSE: To compare the bonding potential to human dentin of adhesive/composite combinations including five 2-step and two 3-step total-etch (TE) bonding systems, two systems with self-conditioning (SC) primers, and one SC all-in-one adhesive by use of the microtensile bond test. METHODS: Hybrid resin composites were bonded to the occlusal dentin of 50 extracted human molars. After water storage (37 degrees C, 24 h), 31-mm-thick slabs were cut from the middle of the teeth perpendicular to their long axis. Microtensile bond strength was determined and debonded surfaces were examined under the SEM for mode of failure. STATISTICS: GLM multivariate procedure for repeated measurements, Student-Newman-Keuls test (SPSS version 10.0; p = 0.05). RESULTS: Mean bond strengths of the simplified (2-step) TE systems (OptiBond Solo, Gluma One Bond, Solobond M, Prime&Bond NT, One Coat Bond; 19.9 MPa to 39.9 MPa) were not significantly lower than that of the traditional 3-step TE systems (EBS Multi: 26.0 MPa; OptiBond FL: 32.7 MPa), and not related to phosphoric acid concentration. Dentin treatment with SC primers (Clearfil Liner Bond 2: 22.0 MPa; Clearfil Liner Bond 2V: 22.4 MPa) was as effective as etching with phosphoric acid. The SC all-in-one adhesive (Etch&Prime 3.0: 10.1 MPa) produced significantly lower bond strength than all other systems evaluated. CONCLUSION: The use of adhesive/composite combinations including simplified bonding systems does not necessarily result in reduced bond strength to dentin. SC primers offer a promising alternative to phosphoric acid etching as far as bonding to dentin is concerned. In contrast, the SC all-in-one adhesive evaluated needs to be improved.

The effect of antioxidants on the production of pro-inflammatory cytokines and orthodontic tooth movement.

Orthodontic force causes gradual compression of the periodontal ligament tissues, which leads to local hypoxia in the compression side of the tissues. In this study, we investigated whether antioxidants exert a regulatory effect on two factors: the expression of pro-inflammatory cytokines in human periodontal ligament fibroblasts (PDLFs) that were exposed to mechanical compression and hypoxia and the rate of orthodontic tooth movement in rats. Exposure of PDLFs to mechanical compression (0.5-3.0 g/cm(2)) or hypoxic conditions increased the production of intracellular reactive oxygen species. Hypoxic treatment for 24 h increased the mRNA levels of IL-1ß, IL-6 and IL-8 as well as vascular endothelial growth factor (VEGF) in PDLFs. Resveratrol (10 nM) or N-acetylcysteine (NAC, 20 mM) diminished the transcriptional activity of hypoxiainducible factor-1 and hypoxia-induced expression of VEGF. Combined treatment with mechanical compression and hypoxia significantly increased the expression levels of IL-1ß, IL-6, IL-8, TNF-α and VEGF in PDLFs. These levels were suppressed by NAC and resveratrol. The maxillary first molars of rats were moved mesially for seven days using an orthodontic appliance. NAC decreased the amount of orthodontic tooth movement compared to the vehicle-treated group. The results from immunohistochemical staining demonstrated that NAC suppressed the expression of IL-1ß and TNF-α in the periodontal ligament tissues compared to the vehicle-treated group. These results suggest that antioxidants have the potential to negatively regulate the rate of orthodontic tooth movement through the down-regulation of pro-inflammatory cytokines in the compression sides of periodontal ligament tissues.

Hypoxia inducible factor-1α directly induces the expression of receptor activator of nuclear factor-κB ligand in periodontal ligament fibroblasts.

During orthodontic tooth movement, local hypoxia and enhanced osteoclastogenesis are observed in the compression side of periodontal tissues. The receptor activator of nuclear factor-κB ligand (RANKL) is an osteoblast/stromal cell-derived factor that is essential for osteoclastogenesis. In this study, we examined the effect of hypoxia on RANKL expression in human periodontal ligament fibroblasts (PDLFs) to investigate the relationship between local hypoxia and enhanced osteoclastogenesis in the compression side of periodontal tissues. Hypoxia significantly enhanced the levels of RANKL mRNA and protein as well as hypoxia inducible factor-1α (HIF-1α) protein in PDLFs. Constitutively active HIF-1α alone significantly increased the levels of RANKL expression in PDLFs under normoxic conditions, whereas dominant negative HIF-1α blocked hypoxia-induced RANKL expression. To investigate further whether HIF-1α directly regulates RANKL transcription, a luciferase reporter assay was performed using the reporter vector containing the RANKL promoter sequence. Exposure to hypoxia or overexpression of constitutively active HIF-1α significantly increased RANKL promoter activity, whereas dominant negative HIF-1α blocked hypoxia-induced RANKL promoter activity. Furthermore, mutations of putative HIF-1α binding elements in RANKL promoter prevented hypoxia-induced RANKL promoter activity. The results of chromatin immunoprecipitation showed that hypoxia or constitutively active HIF-1α increased the DNA binding of HIF-1α to RANKL promoter. These results suggest that HIF-1α mediates hypoxia-induced up-regulation of RANKL expression and that in compression side periodontal ligament, hypoxia enhances osteoclastogenesis, at least in part, via an increased RANKL expression in PDLFs.

Synthetic peptide-coated bone mineral for enhanced osteoblastic activation in vitro and in vivo.

A 15-mer synthetic peptide, designated P1, was derived from the bone morphogenetic protein (BMP) receptor I and BMP receptor II binding domains of BMP-2 for the purpose of enhancing bone regeneration capacity of inorganic bovine bone mineral. A second peptide, denoted P2, was designed by adding seven glutamic acid residues to the N-terminal of P1 to increase the surface coating efficiency onto bone mineral. The coating efficiency of P1 increased with the concentration of peptide. P2 peptide, in contrast, had a higher coating efficiency at lower peptide concentrations. The peptides properly transduced intracellular signals properly via the Smad and ERK pathways, thereby increasing mineralization in vitro, implying that the peptides alone can induce osteoblastic differentiation. Adhesion of cells to bone mineral was greater when peptides were present than in bone mineral alone. P1- and P2-coated bone mineral increased osteoblastic differentiation, as demonstrated by ALPase activity. P1-coated bone mineral stimulated more new bone regeneration in bone defect sites after 2 weeks than the peptide-free control. These peptides, in combination with bone grafts or implants, have the potential to enhance osteoblastic differentiation and bone regeneration.