Essential oil of lemon myrtle (Backhousia citriodora) induces S-phase cell cycle arrest and apoptosis in HepG2 cells.

ETHNOPHARMACOLOGICAL RELEVANCE: Lemon myrtle (Backhousia citriodora F.Muell.) leaves, whether fresh or dried, are used traditionally in folk medicine to treat wounds, cancers, skin infections, and other infectious conditions. However, the targets and mechanisms related to anti-cancer effect of lemon myrtle are unavailable. In our study, we found that the essential oil of lemon myrtle (LMEO) showed anti-cancer activity in vitro, and we initially explored its mechanism of action. MATERIALS AND METHODS: We analyzed the chemical compositions of LMEO by GC-MS. We tested the cytotoxicity of LMEO on various cancer cell lines using the MTT assay. Network pharmacology was used also to analyze the targets of LMEO. Moreover, the mechanisms of LMEO were investigated through scratch assay, flow cytometry analysis, and western blot in the HepG2 liver cancer cell line. RESULTS: LMEO showed cytotoxicity on various cancer cell lines with values of IC50 40.90 ± 2.23 (liver cancer HepG2 cell line), 58.60 ± 6.76 (human neuroblastoma SH-SY5Y cell line), 68.91 ± 4.62 (human colon cancer HT-29 cell line) and 57.57 ± 7.61 µg/mL (human non-small cell lung cancer A549 cell line), respectively. The major cytotoxic chemical constituent in LMEO was identified as citrals, which accounted for 74.9% of the content. Network pharmacological analysis suggested that apurinic/apyrimidinic endodeoxyribonuclease 1 (APEX1), androgen receptor (AR), cyclin-dependent kinases 1 (CDK1), nuclear factor erythroid 2-related factor 2 (Nrf-2), fatty acid synthase (FASN), epithelial growth factor receptor (EGFR), estrogen receptor 1 (ERα) and cyclin-dependent kinases 4 (CDK4) are potential cytotoxic targets of LMEO. These targets are closely related to cell migration, cycle and apoptosis. Notley, the p53 protein had the highest confidence to co-associate with the eight common targets, which was further confirmed by scratch assay, flow cytometry analysis, and western blot in the HepG2 liver cancer cell line. LMEO significantly inhibited the migration of HepG2 cells in time-dependent and dose-dependent manner. Moreover, LMEO caused a S-phase blocking on HepG2 cells and promoted apoptosis in the meanwhile. Western blot results indicated that p53 protein, Cyclin A2 and Bax proteins were up-regulated, while Cyclin E1 and Bcl-2 proteins were down-regulated. CONCLUSION: LMEO showed cytotoxicity in various cancer cell lines in vitro. Pharmacological networks showed LMEO to have multi-component and multi-targeting effects that are related to inhibit migration of HepG2 cells, and affect cell cycle S-phase arrest and apoptosis through modulation of p53 protein.

A hnRNPA2B1 agonist effectively inhibits HBV and SARS-CoV-2 omicron in vivo.

The twenty-first century has already recorded more than ten major epidemics or pandemics of viral disease, including the devastating COVID-19. Novel effective antivirals with broad-spectrum coverage are urgently needed. Herein, we reported a novel broad-spectrum antiviral compound PAC5. Oral administration of PAC5 eliminated HBV cccDNA and reduced the large antigen load in distinct mouse models of HBV infection. Strikingly, oral administration of PAC5 in a hamster model of SARS-CoV-2 omicron (BA.1) infection significantly decreases viral loads and attenuates lung inflammation. Mechanistically, PAC5 binds to a pocket near Asp49 in the RNA recognition motif of hnRNPA2B1. PAC5-bound hnRNPA2B1 is extensively activated and translocated to the cytoplasm where it initiates the TBK1-IRF3 pathway, leading to the production of type I IFNs with antiviral activity. Our results indicate that PAC5 is a novel small-molecule agonist of hnRNPA2B1, which may have a role in dealing with emerging infectious diseases now and in the future.

Transcriptional Analysis of Mice Melanoma B16-F10 Cells in Response to Directed Current Electric Fields.

The endogenous electric field (EF) is widely observed among tissues. It is supposed to be an important environmental factor in tumor metastasis. To explore the role of endogenous EFs in tumor metastasis, the migration of mouse melanoma B16-F10 cells in directed current EFs (dcEFs) was investigated. The transcriptome of melanoma B16-F10 cells in response to EF stimulation was analyzed using RNA sequencing. The results demonstrated that the mouse melanoma B16-F10 cells migrated toward the cathode in applied dcEFs. Directional migration occurred in a voltage-dependent manner. Approximately 3000 upregulated and 2613 downregulated genes were identified under dcEF. Some genes correlated with cell migration, such as Serpine1, Ctgf, Fosb, and Fos, were upregulated. The signaling pathways involved in cell motility were significantly altered. Some genes, highly related to tumorigenesis, invasion, and metastasis, are upregulated in response to EF stimulation. Endogenous EFs may play a role in tumorigenesis and metastasis in vivo. © 2022 Bioelectromagnetics Society.

Clinical outcomes of implant-retained mandibular overdentures using the bar and magnetic attachment systems: an up to 5-year retrospective study.

BACKGROUND: Implant-retained mandibular overdentures (IODs) represent an effective and reliable treatment modality for edentulous patients. The present retrospective study compared the clinical outcomes of IODs using bar attachment (BA) system with those using magnetic attachment (MA) system after functioning for up to 5 years. METHODS: Human subjects treated with IODs between 01-01-2010 and 12-31-2014 were identified from patient records. Of the 54 subjects who met the inclusion criteria, 48 subjects including 26 treated with BA-IODs and 22 with MA-IODs (96 mandibular implants) were recruited for the study. The implant units and prostheses were evaluated individually for peri-implant health. Prosthetic complications and maintenance during follow-up were recorded. The subjects responded to the visual analog scale (VAS) and the Oral Health Impact Profile questionnaires for evaluation of patient satisfaction and oral health-related quality of life (OHRQoL). RESULTS: The survival rates of the implants and prostheses were 96.9% and 95.8%, respectively, over a mean observation period of 48±11.3 (range, 13-64) months. Peri-implant probing depth (PPD) and plaque index (PI) were significantly better for the MA group compared with the BA group (P<0.05), while marginal bone loss (MBL) and sulcus bleeding index (SBI) showed no significant differences (P>0.05). Prosthetic complications and maintenance were attachment-dependent. Most recruited subjects were satisfied with their prostheses. There was no statistically significant difference regarding general patient satisfaction or OHRQoL between the two groups (P>0.05). Nevertheless, patients complained that the BA-IODs were significantly more difficult to clean than the MA-IODs (P<0.05). CONCLUSIONS: IODs have an ideal medium-term outcome irrespective of the attachment design. It is recommended that oral hygiene instructions and regular clinical examination be given to subjects wearing IODs.

Applied electric fields suppress osimertinib-induced cytotoxicity via inhibiting FOXO3a nuclear translocation through AKT activation.

Osimertinib is a third-generation epidermal growth factor receptor tyrosine kinase inhibitor against T790M-mutant non-small cell lung cancer (NSCLC). Acquired resistance to osimertinib is a growing clinical challenge that is not fully understood. Endogenous electric fields (EFs), components of the tumor microenvironment, are associated with cancer cell migration and proliferation. However, the impact of EFs on drug efficiency has not been studied. In this study, we observed that EFs counteracted the effects of osimertinib. EFs of 100 mV/mm suppressed osimertinib-induced cell death and promoted cell proliferation. Transcriptional analysis revealed that the expression pattern induced by osimertinib was altered by EFs stimulation. KEGG analysis showed that differential expression genes were mostly enriched in PI3K-AKT pathway. Then, we found that osimertinib inhibited AKT phosphorylation, while EFs stimulation resulted in significant activation of AKT, which could override the effects generated by osimertinib. Importantly, pharmacological inhibition of PI3K/AKT by LY294002 diminished EF-induced activation of AKT and restored the cytotoxicity of osimertinib suppressed by EFs, which proved that AKT activation was essential for EFs to attenuate the efficacy of osimertinib. Furthermore, activation of AKT by EFs led to phosphorylation of forkhead box O3a (FOXO3a), and reduction in nuclear translocation of FOXO3a induced by osimertinib, resulting in decreased expression of Bim and attenuated cytotoxicity of osimertinib. Taken together, we demonstrated that EFs suppressed the antitumor activity of osimertinib through AKT/FOXO3a/Bim pathway, and combination of PI3K/AKT inhibitor with osimertinib counteracted the effects of EFs. Our findings provided preliminary data for therapeutic strategies to enhance osimertinib efficacy in NSCLC patients.

Correction: Caveolin-1-mediated STAT3 activation determines electrotaxis of human lung cancer cells.

[This corrects the article DOI: 10.18632/oncotarget.21306.].

Caveolin-1-mediated STAT3 activation determines electrotaxis of human lung cancer cells.

Migration of cancer cells leads to the invasion of distant organs by primary tumors. Further, endogenous electric fields (EFs) in the tumor microenvironment direct the migration of lung cancer cells by a process referred to as electrotaxis - although the precise mechanism remains unclear. Caveolin-1 (Cav-1) is a multifunctional scaffolding protein that is associated with directional cell migration and lung cancer invasion; however, its precise role in lung cancer electrotaxis is unknown. In the present study, we first detected outward electric currents on the tumor body surface in lung cancer xenografts using a highly-sensitive vibrating probe. Next, we found that highly-metastatic H1650-M3 cells migrated directionally to the cathode. In addition, reversal of the EF polarity reversed the direction of migration. Mechanistically, EFs activated Cav-1 and the downstream signaling molecule STAT3. RNA interference of Cav-1 reduced directional cell migration, which was accompanied by dampened STAT3 activation. Furthermore, pharmacological inhibition of STAT3 significantly reduced the electrotactic response, while rescue of STAT3 activation in Cav-1 knock-down cells restored electrotaxis. Taken together, these results suggest that endogenous EFs in the tumor micro-environment might play an important role in lung cancer metastasis by guiding cell migration through a Cav-1/STAT3-mediated signaling pathway.

Chemical Composition and Acetylcholinesterase Inhibitory Activity of Essential Oils from Piper Species.

The essential oils (EOs) derived from aromatic plants such as Piper species are considered to play a role in alleviating neuronal ailments that are associated with inhibition of acetylcholinesterase (AChE). The chemical compositions of 23 EOs prepared from 16 Piper spp. were analyzed by both gas chromatography with a flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS). A total of 76 compounds were identified in the EOs from the leaves and stems of 19 samples, while 30 compounds were detected in the EOs from the fruits of four samples. Sesquiterpenes and phenylpropanoids were found to be rich in these EOs, of which asaricin, caryophyllene, caryophyllene oxide, isospathulenol, (+)-spathulenol, and ß-bisabolene are the major constituents. The EOs from the leaves and stems of Piper austrosinense, P. puberulum, P. flaviflorum, P. betle, and P. hispidimervium showed strong AChE inhibitory activity with IC50 values in the range of 1.51 to 13.9 mg/mL. A thin-layer chromatography (TLC) bioautography assay was employed to identify active compound(s) in the most active EO from P. hispidimervium. The active compound was isolated and identified as asaricin, which gave an IC50 value of 0.44 ± 0.02 mg/mL against AChE, comparable to galantamine with an IC50 0.15 ± 0.01 mg/mL.

Occlusion and Disocclusion Time Changes in Single Unit Crowns Designed by Functional Generated Path Technique: A Randomised Clinical Trial.

Although it is believed that implementation of the functional generated path (FGP) technique can facilitate occlusal surface design for restorations, it has not been objectively compared in situ with the conventional fabrication yet. Therefore, in the present study, a single-blind crossover clinical trial was conducted using T-scan to compare changes in occlusion time (OT) and disocclusion time (DT) of single posterior artificial crowns designed differently using FGP technique (FGP), average-value FGP technique (AVR) and conventional fabrication (CON). Each of the 10 participants took part in the study tried three artificial crowns in different sequences according to a computer generated randomization list. The results objectively revealed that changes in OT and DT were significantly smaller for FGP than CON (P < 0.05) and considerably smaller for AVR than CON, respectively. The subjective feedback and the occlusal adjusting time were better and shorter for FGP and AVR than CON (P < 0.05). No harm to the participants occurred. Overall, FGP is an efficient technique showing more physiological harmonious relationship with the articulating system.

A large-scale screen reveals genes that mediate electrotaxis in Dictyostelium discoideum.

Directional cell migration in an electric field, a phenomenon called galvanotaxis or electrotaxis, occurs in many types of cells, and may play an important role in wound healing and development. Small extracellular electric fields can guide the migration of amoeboid cells, and we established a large-scale screening approach to search for mutants with electrotaxis phenotypes from a collection of 563 Dictyostelium discoideum strains with morphological defects. We identified 28 strains that were defective in electrotaxis and 10 strains with a slightly higher directional response. Using plasmid rescue followed by gene disruption, we identified some of the mutated genes, including some previously implicated in chemotaxis. Among these, we studied PiaA, which encodes a critical component of TORC2, a kinase protein complex that transduces changes in motility by activating the kinase PKB (also known as Akt). Furthermore, we found that electrotaxis was decreased in mutants lacking gefA, rasC, rip3, lst8, or pkbR1, genes that encode other components of the TORC2-PKB pathway. Thus, we have developed a high-throughput screening technique that will be a useful tool to elucidate the molecular mechanisms of electrotaxis.

[Analysis of type-I collagen fibrils and chondroitin sulfate distribution in human dentin by confocal laser scanning microscopy combined with dual immunofluorescent labeling technique].

OBJECTIVE: To introduce the method of dual immunofluorescence labeling of human dentin matrix without demineralization of the whole dentin fragments, and to analyze the distribution of type-I collagen fibrils and chondroitin sulfate in human dentin. METHODS: Forty 30 µm- thick middle coronal dentin sections were obtained from 8 freshly extracted human third molars and etched with 37% phosphoric acid(PA) gel for 15 s. After preconditioning with or without tosyl- phenylalanyl chloromethyl ketone(TPCK) treated trypsin digestion, sections were subjected to dual immunofluorescent labeling and scanned by confocal laser scanning microscopy to identify the type-I collagen fibrils and chondroitin sulfate. RESULTS: Chondroitin sulfate was localized in the lumens of the dentin tubules and peritubular dentin, while the type-I collagen fibrils were localized in intertubular dentin and peritubular dentin. After preconditioning with TPCK treated trypsin digestion, the red fluorescence was decreased or disappeared. CONCLUSIONS: The dual immunofluorescence labeling methodology can be used to study the human dentin matrix without demineralization of the whole dentin fragments. Chondroitin sulfate was localized in the lumens of the dentin tubules and peritubular dentin, while the type-I collagen fibrils were localized in intertubular dentin and peritubular dentin.

Health-related quality of life after mandibular resection for oral cancer: Reconstruction with free fibula flap

OBJECTIVES: Mandibular resection for oral cancer is often necessary to achieve an adequate margin of tumor clearance. Mandibular resection has been associated with a poor health-related quality of life (HRQOL), particularly before free fibula flap to reconstruct the defect. The aim of this study was to evaluate health-related quality of life in patients who have had mandibular resections of oral cancer and reconstruction with free fibula flap. Study Designs: There were 115 consecutive patients between 2008 and 2011 who were treated by primary surgery for oral squamous cell carcinoma, 34 patients had a mandibular resection. HRQOL was assessed by means of the 14-item Oral Health Impact Profile (OHIP-14) and University of Washington Quality of Life (UW-QOL) questionnaires after 12 months postoperatively. RESULTS: In the UW-QOL the best-scoring domain was mood, whereas the lowest scores were for chewing and saliva. In the OHIP-14 the lowest-scoring domain was social disability, followed by handicap, and psychological disability. CONCLUSIONS: Mandible reconstruction with free fibula flap would have significantly influenced on patients'quality of life and oral functions. The socio-cultural data show a fairly low level of education for the majority of patients

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Proteoglycans affect monomer infiltration in the etch-and-rinse bonding technique.

OBJECTIVES: To identify proteoglycans (PGs) and collagen fibrils (CF) within human dentin by means of a dual immunofluorescent labeling technique and to investigate the monomer infiltration of two etch-and-rinse adhesives to tosyl-phenylalanine chloromethyl-ketone (TPCK)-treated trypsin (TRY)-pretreated dentin. METHODS: Thirty-micrometer sections of middle coronal dentin were obtained and etched with 37% phosphoric acid gel for 15 s. After preconditioning with or without TRY digestion, the sections were subjected to dual immunofluorescent labeling and observed with a confocal laser scanning microscope (CLSM). Demineralized dentin matrixes treated with or without TRY were observed with field emission scanning electron microscope (FE-SEM). Two etch-and-rinse adhesives, Adper Single Bond 2 (SB) and Prime & Bond NT (PBNT), were applied to the dentin surfaces that were pretreated with or without TRY. The thickness of the hybrid layers was evaluated under confocal micro-Raman spectroscopy and analyzed with a two-way ANOVA. RESULTS: Green and red fluorescence was used to represent the PGs and the CF that were colocalized in the same section with different distributions. PGs were localized in the lumens of the dentin tubules and in peritubular dentin, while the type-I collagen fibrils were localized in intertubular dentin and peritubular dentin. After preconditioning with TRY digestion, the red fluorescence decreased or disappeared, the organic filaments in the lumens of the dentin tubules disappeared, the tubules were enlarged, and the hybrid layer thickness for adhesives bonded to the TRY-pretreated dentin surfaces were significantly increased (p<0.001 for both SB and PBNT). SIGNIFICANCE: The dual immunofluorescence labeling methodology can be used to study the human dentin matrix without decalcifying the entire dentin fragment. Proteoglycans were localized in the lumens of the dentin tubules and in peritubular dentin, which could depress the infiltration of the adhesive resin monomers. The use of TRY digestion increased the thickness of the hybrid layer created by the tested two-step etch-and-rinse adhesive.

[Bonding properties of four different cements to glass fiber posts after different treatments].

OBJECTIVE: To investigate the effect of four different cements on the bonding effectiveness of root canal dentine and fiber post before and after different treatments. METHODS: A total of 216 freshly extracted sound single-root-canal mandibular premolars were randomly divided into four groups. After root canal treatment and post space preparation being conducted on the premolars, Fuji I, Fuji Cem, RelyX Unicem, RelyX ARC were used respectively to bond fiber posts and were marked with group A, B, C, and D. Microleakage, micromorphology of the bonded interfaces, and pull-out bond strength were evaluated in the immediate group, thermocycling group and thermomechanical loading group. RESULTS: In the immediate group, samples in group D showed the highest bond strength [(278 ± 26)N], followed by group C[ (219 ± 12) N], B[ (104 ± 23) N] and A[(73 ± 8) N]. Significant differences were found among all groups (P < 0.05) . A significant increase in bond strength was found in group A and B, whereas a decrease tendency was detected in group C and D after different treatments.Scanning electron microscope indicated that some little gaps were observed in group D after treatment, while a more intense bonding interface was found in group A and B. Microleakage scores in group A and B were lower than those in group C and D after aging treatments. CONCLUSIONS: Resin cement can achieve a better immediate bond strength, while resin-modified resin cement may acquire a better long-term retention.

Health-related quality of life after mandibular resection for oral cancer: reconstruction with free fibula flap.

OBJECTIVES: Mandibular resection for oral cancer is often necessary to achieve an adequate margin of tumor clearance.Mandibular resection has been associated with a poor health-related quality of life (HRQOL), particularly before free fibula flap to reconstruct the defect. The aim of this study was to evaluate health-related quality of life in patients who have had mandibular resections of oral cancer and reconstruction with free fibula flap. STUDY DESIGNS: There were 115 consecutive patients between 2008 and 2011 who were treated by primary surgery for oral squamous cell carcinoma, 34 patients had a mandibular resection. HRQOL was assessed by means of the 14-item Oral Health Impact Profile (OHIP-14) and University of Washington Quality of Life (UW-QOL) questionnaires after 12 months postoperatively. RESULTS: In the UW-QOL the best-scoring domain was mood, whereas the lowest scores were for chewing and saliva. In the OHIP-14 the lowest-scoring domain was social disability, followed by handicap, and psychological disability. CONCLUSION: Mandible reconstruction with free fibula flap would have significantly influenced on patients'quality of life and oral functions.The socio-cultural data show a fairly low level of education for the majority of patients.

[Effect of dentin proteoglycans on the bonding properties of dentin].

OBJECTIVE: To investigate the potential effect of proteoglycan (PG) and glycosaminoglycan (GAG) on the bonding of etch and rinse adhesive to dentin, in order to improve the bonding effect of dentin. METHODS: Forty-two extracted molars were used to obtain standard dentin bonding surface, and the specimens were etched for 15 s with 37% phosphoric acid and divided into three groups using a table of random numbers. Then the three groups undergone different incubating procedures as follow: specimens in chondroitinase ABC (C-ABC) group were incubated with C-ABC at 37 °C for 48 h in vibrator. Specimens in trypsin (TRY) group were incubated with trypsin, and specimens in the control group were incubated with deionized water for 48 h in the oscillators. Then specimens in each group were randomly assigned into two subgroups, A (Adper(TM) Single Bond 2) and B (Prime & Bond NT) (n = 7). The microtensile bond strength (µTBS), fracture mode and bonding interface morphology of the specimens were evaluated via microtensile testing, stereo microscope and field emission scanning electron microscopy (FE-SEM) respectively after specimens being incubated in 37 °C water for 24 h. RESULTS: The immediate µTBS of C-ABC group bonding with adhesive A and B [(32.9±2.5) and (26.8±2.2) MPa] were significantly lower than that of the control group [(40.7±3.3) and (34.6±3.7) MPa] (P < 0.05). While the immediate µTBS of TRY group [(49.0 ± 3.6) and (44.5 ± 3.0) MPa] were significantly higher than that of the control group(P < 0.05). CONCLUSIONS: Dentin PG participates in the dentin bonding process. Removal of PG increased the immediate µTBS of dentin and total etching adhesives, while removal of GAG decreased the immediate µTBS.

Effect of luting cement and thermomechanical loading on retention of glass fibre posts in root canals.

OBJECTIVES: To evaluate the effect of luting cement and thermomechanical loading on the retention of glass fibre posts in root canals. METHODS: One hundred and forty-four single-rooted human premolars were endodontically treated and restored with RelyX Fibre Posts. The teeth were divided into four groups according to the cements used (Fuji I, Fuji CEM, RelyX Unicem and RelyX ARC). Each group was further divided into two subgroups according to the method of ageing (immediately tested and after thermomechanical loading). Bond strength was evaluated using a pull-out test. Microleakage was examined quantitatively with dye penetration. The dentine-cement-post bonding interface was assessed using scanning electron microscopy. Data were analysed with two-way ANOVA (pull-out test) and Kruskal-Wallis analysis (microleakage). RESULTS: The pull-out bond strength and microleakage were significantly affected by the type of cement and ageing. Although RelyX ARC showed the highest bond strength before thermomechanical loading (p<0.05), the sealing ability of this cement was worse than those exhibited in Fuji CEM and RelyX Unicem (p<0.05). After thermomechanical loading, pull-out strengths of Fuji I and Fuji CEM were significantly increased, whereas that of RelyX ARC group significantly decreased (p<0.05). The sealing ability of Fuji CEM was significantly better than the two resin cement groups (p<0.05) after ageing. CONCLUSION: Fuji CEM demonstrates increased pull-out strength after thermomechanical loading and favourable sealing ability compared with the other cements. CLINICAL SIGNIFICANCE: Resin-modified glass ionomer cements have the potential benefit of achieving long-term retention when used for luting glass fibre post to root canal dentine. So it may be recommended for the cementation of glass fibre post in clinics.

3D arrays for high throughput assay of cell migration and electrotaxis.

Cell behaviour in 3D environments can be significantly different from those in 2D cultures. With many different 3D matrices being developed and many experimental modalities used to modulate cell behaviour in 3D, it is necessary to develop high throughput techniques to study behaviour in 3D. We report on a 3D array on slide and have adapted this to our electrotaxis chamber, thereby offering a novel approach to quantify cellular responses to electric fields (EFs) in 3D conditions, in different matrices, with different strains of cells, under various field strengths. These developments used Dictyostelium cells to illustrate possible applications and limitations.

A new fixation method for stick-shaped specimens in microtensile tests: laboratory tests and FEA.

PURPOSE: To introduce a new fixation method for stick-shaped specimens for use in microtensile tests and to evaluate the effect of this new method on microtensile bond strength, failure modes, and stress distribution. MATERIALS AND METHODS: Flat mid-coronal dentin surfaces were prepared on 12 caries-free human third molars and randomly divided into two groups for testing with two dental adhesives (Adper Single Bond 2 [SB2] and Clearfil SE Bond [SEB]). Following adhesive application and composite buildups, the bonded teeth were sectioned into beams. Sticks from each tooth were then equally divided into two subgroups for microtensile bond testing according to the utilized gripping devices (a flat Ciucchi's jig and the experimental setup). Failure modes were examined with a field-emission scanning electron microscope (FESEM). Three-dimensional models of each gripping device and specimen were developed, and stress distributions were analyzed by finite element analysis (FEA). Statistical significance was set at α = 0.05 RESULTS: Compared to those fixed using a flat Ciucchi's jig, sticks fixed with the experimental setup yielded lower bond strength values (p = 0.021 for SB2 and p = 0.007 for SEB) and more mixed failure patterns (p = 0.036 for both SB2 and SEB). In addition, the experimental setup guaranteed a uniaxial tensile force that was perpendicular to the bonding interface and produced a more uniform stress distribution at the bonding interface. CONCLUSION: An experimental setup for fixing microtensile sticks was proposed that was designed to provide a uniform stress distribution at the adhesive interface. FEA and failure mode analysis confirmed such uniform distribution, thus supporting the validity of the bond strength results obtained with this new fixture design.

[The potential effect of proanthocyanidins on the stability of resin-dentin bonds against thermal cycling].

OBJECTIVE: To investigate the potential effect of proanthocyanidins (PA), a natural cross-linker, on the stability of resin-dentin bonds against thermal cycling. METHODS: Ten percent, 15% PA-based preconditioners, and 5% glutaraldehyde were prepared for the transient pretreatment of demineralized dentin before bonding. Specimens without pretreatment were used as negative controls (n = 4 teeth for each group). Microtensile bond strength, failure mode, micromorphologies of resin-dentin interface and the collagen degradation of bonded specimens after thermal cycling were evaluated. RESULTS: After thermal cycling, the microtensile bond strength values of resin-dentin bond in groups pretreated with 15% PA for 120 s and 60 s [(23.09 ± 3.19) and (21.88 ± 3.49) MPa] were significantly higher than that in control group [(15.47 ± 3.78) MPa] (P < 0.05). Mixed fractures were the most prevalent failure mode. Specimens with pretreatment presented compact hybrid layer, while some narrow gaps were found in hybrid layer of non-treated specimens. Collagen biodegradation rates in groups with pretreatment were significantly lower than that in control group (P < 0.05). Among them, specimens pretreated by 15% PA preconditioner for 120 s exhibited the lowest biodegradation rates [(0.316 ± 0.019) mg/g]. CONCLUSIONS: The application of natural cross-linker PA on demineralized dentin reduced the bond degradation against aging by thermal cycling, and can be helpful to create more durable bonds to dentin.