Fascicular ventricular tachycardia arising from the left side His and its adjacent region: a subset of upper septal idiopathic left ventricular tachycardia.

AIMS: Fascicular ventricle tachycardia (FVT) arising from the proximal aspect of left His-Purkinje system (HPS) has not been specially addressed. Current study was to investigate its clinical, electrocardiographic, and electrophysiological characteristics. METHODS AND RESULTS: Eighteen patients who were identified as this rare FVT were consecutively enrolled, and their scalar electrocardiogram and electrophysiological data were collected and analysed. The ventricular tachycardia (VT) morphology was similar to sinus rhythm (SR) in eight patients, left bundle branch block type in one patient, right bundle branch block type in seven patients, and both narrow and wide QRS type in two patients. During VT, right-sided His potential preceded the QRS with His-ventricle (H-V) interval of 36.3 ± 12.4 ms, which was shorter than that during SR (-51.4 ± 8.6 ms) (P = 0.002). The earliest Purkinje potentials (PPs) were recorded within 7 ± 3 mm of left-side His and preceded the QRS by 49.1 ± 14.0 ms. Mapping along the left anterior fascicle and left posterior fascicle revealed an antegrade activation sequence in all with no P1 potentials recorded. In the two patients with two VT morphologies, the earliest PP was documented at the same site, and the activation sequence of HPS remained antegrade. Ablation at the earliest PP successfully eliminated the tachycardia, except one patient who developed complete atrial-ventricular block and two patients who abandoned ablations. After at least 12 months follow-up, 15 patients were free from any recurrences. CONCLUSIONS: Fascicular ventricle tachycardia arising from the proximal aspect of left HPS was featured by recording slightly shorter H-V interval and absence of P1 potentials. Termination of VT requires ablation at the left-sided His or its adjacent region.

Asymptomatic atrial fibrillation among hospitalized patients: clinical correlates and in-hospital outcomes in Improving Care for Cardiovascular Disease in China-Atrial Fibrillation.

AIMS: The clinical correlates and outcomes of asymptomatic atrial fibrillation (AF) in hospitalized patients are largely unknown. We aimed to investigate the clinical correlates and in-hospital outcomes of asymptomatic AF in hospitalized Chinese patients. METHODS AND RESULTS: We conducted a cross-sectional registry study of inpatients with AF enrolled in the Improving Care for Cardiovascular Disease in China-Atrial Fibrillation Project between February 2015 and December 2019. We investigated the clinical characteristics of asymptomatic AF and the association between the clinical correlates and the in-hospital outcomes of asymptomatic AF. Asymptomatic and symptomatic AF were defined according to the European Heart Rhythm Association score. Asymptomatic patients were more commonly males (56.3%) and had more comorbidities such as hypertension (57.4%), diabetes mellitus (18.6%), peripheral artery disease (PAD; 2.3%), coronary artery disease (55.5%), previous history of stroke/transient ischaemic attack (TIA; 17.9%), and myocardial infarction (MI; 5.4%); however, they had less prevalent heart failure (9.6%) or left ventricular ejection fractions ≤40% (7.3%). Asymptomatic patients were more often hospitalized with a non-AF diagnosis as the main diagnosis and were more commonly first diagnosed with AF (23.9%) and long-standing persistent/permanent AF (17.0%). The independent determinants of asymptomatic presentation were male sex, long-standing persistent AF/permanent AF, previous history of stroke/TIA, MI, PAD, and previous treatment with anti-platelet drugs. The incidence of in-hospital clinical events such as all-cause death, ischaemic stroke/TIA, and acute coronary syndrome (ACS) was higher in asymptomatic patients than in symptomatic patients, and asymptomatic clinical status was an independent risk factor for in-hospital all-cause death, ischaemic stroke/TIA, and ACS. CONCLUSION: Asymptomatic AF is common among hospitalized patients with AF. Asymptomatic clinical status is associated with male sex, comorbidities, and a higher risk of in-hospital outcomes. The adoption of effective management strategies for patients with AF should not be solely based on clinical symptoms.

Evaluation of left atrial volume and function using single-beat real-time three-dimensional echocardiography in atrial fibrillation patients.

BACKGROUND: This study was aimed to evaluate the feasibility and accuracy of real-time three-dimensional echocardiography (RT-3DE) measurement of left atrial (LA) volume and function in comparison with two-dimensional echocardiography (2DE) measurements in atrial fibrillation (AF) patients. METHODS: A total of 50 pairs of AF patients and healthy controls were enrolled in this study. Indexed LA end-diastole volume (ILAEDV) and indexed LA end-systolic volume (ILAESV), as well as LA function indices such as segmental LA ejection fraction (LAEF), were assessed using 2DE Simpson's method and the RT-3DE method. RESULTS: The images showed that regional LA volume-time curves and LAEF were disordered in AF patients. ILAEDV and ILAESV were markedly increased and global LAEF was significantly decreased in AF patients compared with those in healthy controls (P < 0.01). No significant differences were found in ILAEDV, ILAESV, and LAEF levels as determined by the RT-3DE method or 2DE Simpson's method. Bland-Altman analysis showed that the two methods agreed well for measuring ILAEDV, ILAESV, and segmental LAEF. CONCLUSION: The RT-3DE method may be a feasible and accurate method for evaluating LA volume and function of AF patients in clinical practice.

Efficient preparation of (R)-2-chloromandelic acid via a recycle process of resolution.

Efficient preparation of (R)-2-chloromandelic acid based on a recycle process of resolution is described. In the process, the desired was obtained by coordination-mediated resolution with D-O,O'-di-(p-toluoyl)-tartaric acid in the presence of Ca(2+) . Meanwhile, the undesired could be racemized in the presence of sodium hydroxide and the product was suitable for further resolution. A carbanion mechanism for the racemization of is proposed.

[Study of the mucosal morphological difference of distal-extension of mandibular dentition defect impressions taken by intra-oral digital scanning and selective pressure impression technique].

PURPOSE: To compare the mucosal morphological difference in distal-extension area of mandibular dentition defect taken by intra-oral digital scanning and selective pressure impression techniques. METHODS: Seventeen patients with Kennedy Class I and Class II dentition defect in lower jaw were included, including twenty-two distal-extensions. Intraoral digital scanning and functional impression technique were taken in each patients, respectively. Laboratory cast scanner was used to scan the plaster casts made from the selective pressure impression to obtain the three-dimensional data. All the data were stored in STL format. The 3D data collecting from intra-oral digital scanning and selective pressure impression from the same patient were compared by Geomagic Control 2014 software. Root mean square of 2.5mm diameter area was calculated in 5,10,15 mm from terminal tooth. Pearson's correlation test was used to analyze the correlation of the distance and morphological difference with SPSS 20.0 software package. RESULTS: Mean mucosal morphological difference of jaw distal-extension edentulous area taken by intra-oral digital scanning and selective pressure impression techniques was (0.37±0.12) mm. There was positive correlation between distance from terminal tooth and mucosal morphological difference(P＜0.05). Morphological differences in 5, 10, 15 mm from terminal tooth were (0.14±0.11) mm, (0.22±0.13) mm and (0.39±0.16) mm, respectively. CONCLUSIONS: In this study, there was positive correlation between the length of distal-extension edentulous area and mucosal morphological difference, while the kind of ridge defect and mucosal thickness may also affect the morphological difference quantity.

[Correlation of miR-195 with invasiveness and prognosis of breast cancer].

OBJECTIVE: To explore the potential role of miR-195 on invasiveness and prognosis of breast cancer. METHODS: The RNA in formalin-fixed paraffin embedded (FFPE) of 88 breast cancer patients with primary tumors was extracted, and miR-195 levels were quantified by quantitative real-time polymerase chain reaction (real-time PCR). The relationship of miR-195 levels and clinicopathological variables were assessed by Mann Whitney-U test. Recurrence-free survival and overall survival curves were derived from Kaplan-Meier estimates and the curves were compared by Log-rank tests. Cox regression analysis was used for multivariate analysis. All statistical tests were two-sided. RESULTS: The levels of miR-195 in the breast cancer with histological high grade, tumor size of T3-4, lymph nodal involvement or vessel invasion were significantly down-regulated, compared with those of patients with histological low grade (Z = -2.271, P = 0.023), tumor size of T1-2 (Z = -2.687, P = 0.007), no lymph node metastasis (Z = -1.967, P = 0.049) and vessel invasion (Z = -2.432, P = 0.015). In addition, no statistically significant difference (P > 0.05) was identified between miR-195 levels and hormone receptors status, HER-2 expression, TNM stage, tumor types, recurrence and menstrual status. When considering 2(-ΔCt) = 0.270 (median level) as cut-off value, Kaplan-Meier survival analysis indicated that patients with high miR-195 level showed a positive association towards a longer survival, either recurrence-free survival (χ(2) = 5.985, P = 0.014) or overall survival (χ(2) = 30.05, P = 0.000). In a multivariate analysis, miR-195 expression on FFPE correlated significantly with outcomes of breast cancer (HR = 0.040, 95%CI: 0.009 - 0.179, P = 0.000) and was independent of other prognostic factors. CONCLUSIONS: It suggests that miR-195 expression on FFPE is inversely correlated with histological high grade, bigger tumor size, lymph node involvement, vessel invasion. Furthermore, as independent prognostic factor, low miR-195 significantly contributes to poor outcomes of breast cancer.

[Correlation of polymorphism rs1563828 in MDM4 gene with breast cancer risk and onset age].

OBJECTIVE: To explore effect of polymorphism rs1563828 (C > T) in human murine double minute 4 gene (MDM4) on genetic susceptibility for early-onset breast cancer and potential association with age of onset of breast cancer. METHODS: One hundred and twenty-four early-onset breast cancer patients (age ≤ 35 years at time of diagnosis) from independent families admitted from January 2006 to June 2010 and 101 age-matched healthy control subjects were analyzed. Genotype analysis was conducted by polymerase chain reaction and then MALDI-TOF-MS assay. Association of genotype distribution and breast cancer risk was evaluated by χ(2) test. The odd-ratios (OR) and 95% confidence intervals (CI) were calculated by unconditional Logistic regression model. The t test was used to compare the age and demographic differences among groups. RESULTS: The frequency of rs1563828 polymorphism genotypes in control group were CC 43.6% (44/101), CT 42.6% (43/101), TT 13.9% (14/101), and in case group were 42.7% (53/124), 46.0% (57/124), 11.3% (14/124), respectively. No significant difference (χ(2) = 0.449, P = 0.799) was reached by χ(2) test. rs1563828CT or TT genotype does not confer a significantly increased risk for breast cancer compared with CC genotype after adjusting for age, menarche in Logistic regression analysis (OR = 1.024, 95%CI: 0.581 - 1.806, P = 0.934). TT carriers were observed to develop breast cancer earlier than CC/CT carriers [(30 ± 4) years vs. (32 ± 3) years, P = 0.028]. CONCLUSIONS: The rs1563828(C > T) polymorphism in MDM4 gene may not confer risk to breast cancer, especially for early-onset breast cancer patients. Homozygous TT of rs1563828 is associated with younger age to develop breast cancer.

[Correlation of miR-155 on formalin-fixed paraffin embedded tissues with invasiveness and prognosis of breast cancer].

OBJECTIVE: To investigate the potential use of miR-155 as novel breast cancer biomarker. METHODS: There were 88 breast cancer patients underwent modified mastectomy and had detailed clinical follow-up information. Extracting RNA from the formalin-fixed paraffin embedded (FFPE) samples, miR-155 levels were quantified by real-time-PCR. miR-155 levels among clinico-pathological variables were accessed by Mann Whitney-U test. Overall survival curve was derived from Kaplan-Meier estimates and the curve was compared by Log-rank test. Cox regression analysis was used for multivariate analysis. All statistical tests were two-sided. RESULTS: Significantly higher miR-155 level was found in tumor tissue compared to paired normal tissue (t = 6.75, P = 0.000). A potential relationship between miR-155 levels and existing clinico-pathological parameters of breast cancer, such as menstrual status, tumor size, nodal involvement, stage of disease, hormone receptor status, HER-2 status, histological grade or tumor subtype was investigated. Up-regulated miR-155 level was observed in breast cancer with lymph node metastasis, pT3+4, advanced TNM stage, HER-2 positive and with vascular invasion (Z = -6.320 to -2.041, P = 0.000 to 0.041). When considering 2(-ΔCt) = 4.87 (median level) as cut-off value, patients with miR-155 up-regulation showed a positive association towards a shorter overall survival (χ(2) = 6.396, P = 0.011). In Cox multivariate analysis, miR-155 expression on FFPE was shown an inverse trend for outcomes of breast cancer (HR = 1.58, 95%CI: 0.87 - 3.16, P = 0.082). CONCLUSIONS: miR-155, as an oncomir, promotes lymph node involvement and vascular invasion and accompanies over-expressed HER-2 on breast cancer FFPE tissue. It suggests that miR-155 could predict the invasiveness.

[Study of the morphological difference of upper jaw impressions taken by intra-oral digital scanning and functional impression technique].

PURPOSE: To compare the difference in distal-extension models taken by intra-oral digital scanning and functional impression technique. METHODS: Twenty patients with dentition defect in upper jaw, including 10 Kennedy Ⅰ defect and another 10 Kennedy Ⅱ defect, were chosen to treat with intraoral digital scanning and functional impression technique respectively. Laboratory cast scanner was used to scan the plaster casts made from the functional impression to obtain the three-dimensional data. All the data were stored in STL format. The 3D data collecting from intra-oral digital scanning and functional impression from the same patient were compared by Geomagic Qualify 12 software, and the trueness of the difference on free end morphology were analyzed. Paired t test was used to analyze the difference of the alveolar mucosa variable with SPSS 20.0 software package. RESULTS: There was no significant difference between the group of Kennedy I defect and Kennedy Ⅱ defect(P>0.05） regarding the two methods of impression. All the cases presented the tendency that with distance from distal teeth increasing, the average RMS also increased. CONCLUSIONS: Whether using intra-oral digital scanning or functional impression technique, the type of dentition defect was not obviously related to the difference of RMS in distal-extension tissues. In addition, there is positive correlation between the length of distal-extension edentulous area and difference of RMS, which needs further studies with more cases.

Lifetime-Engineered Carbon Nanodots for Time Division Duplexing.

Optical multiplexing attracts considerable attention in the field of information encryption, optical probe, and time-resolved bioimaging. However, the optical multiplexing based on rare-earth nanoparticles suffers from heavy metal elements and relatively short lifetimes; sophisticated facilities are thus needed. Herein, time division duplexing based on eco-friendly carbon nanodots (CNDs) with manipulative luminescence lifetimes is demonstrated. In a single green color emission channel, the luminescence lifetimes of the CNDs can be manipulated from nanosecond level to second level by introducing water, while the lifetime of the CNDs confined by a silica shell stays. Time division duplexing based on the CNDs and CNDs@silica with distinct lifetimes is realized and spatio-temporal overlapping information is thus resolved. High-level information encryption using the time division duplexing technology is realized. This work may promise the potential applications of CNDs in multi-lifetime channels biological imaging, high-density information storage, and anti-counterfeiting.

Phosphorescent Carbon-Nanodots-Assisted Förster Resonant Energy Transfer for Achieving Red Afterglow in an Aqueous Solution.

Water-soluble red afterglow imaging agents based on ecofriendly nanomaterials have potential application in time-gated afterglow bioimaging due to their larger penetration depth and nondurable excitation. Herein, red afterglow imaging agents consisted of Rhodamine B (RhB) and carbon nanodots (CNDs) have been designed and demonstrated. In these agents, CNDs act as energy donors, and RhB acts as an energy acceptor. Both of them are confined into a hydrophilic silica shell to form a CNDs-RhB@silica nanocomposite. The phosphorescence emission spectrum of the CNDs and the absorption spectrum of the RhB match well, and efficient energy transfer from the CNDs to the RhB via Förster resonant energy transfer process can be achieved, with a transfer efficiency can reach 99.2%. Thus, the as-prepared nanocomposite can emit a red afterglow in aqueous solution, and the afterglow spectrum of CNDs-RhB@silica nanocomposite can extend to the first near-infrared window (NIR-I). The luminescence lifetime and afterglow quantum yield (QY) of the CNDs-RhB@silica can reach 0.91 s and 3.56%, respectively, which are the best results in red afterglow region. Time-gated in vivo afterglow imaging has been demonstrated by using the CNDs-RhB@silica as afterglow agents.

[A comparative study on the effect of glass fiber post and metal post in restoration of anterior tooth defect].

PURPOSE: To analyze the effect and long-term success rate of using glass fiber post or metal post in restoration of anterior tooth defect. METHODS: One hundred and fifty cases with anterior tooth defects were chosen after root canal therapy in our hospital. According to different material being chosen, the patients were divided into fiber post group and metal post group with 75 cases in each group. Local gingival sulcus fluid (GCF) levels and alkaline phosphatase (ALP) level in gingival sulcus liquid were measured and compared 4 weeks, 6 months, 1 year, 2 years and 3 years after restoration. Restoration integrity, edge fitness and color matching of two groups were compared after follow-up for 3 years. The data were analyzed with SPSS 19.0 software package. RESULTS: Four weeks, 6 months, and 1 year after restoration, local GCF, ALP levels significantly elevated in both groups. The fiber post group showed more significant elevated levels of GCF and ALP than the metal post group (P<0.05). After 2 and 3 years, the difference between the two groups was not significant. The gingival color matching degrees were significantly better in the glass fiber post group after 1 year compared with that in the metal post group(P<0.05). The success rate of metal post group was significantly higher than that of fiber post group 3 years after restoration(P<0.05). CONCLUSIONS: Fiber post and metal post both have satisfactory restoration result for tooth defect in anterior teeth area. However, the use of precious metal alloy post may reduce the possibility of microleakage between tooth-prosthesis surfaces.

Water-induced MAPbBr3@PbBr(OH) with enhanced luminescence and stability.

Poor stability has long been one of the key issues that hinder the practical applications of lead-based halide perovskites. In this paper, the photoluminescence (PL) quantum yield (QY) of bromide-based perovskites can be increased from 2.5% to 71.54% by introducing water, and the PL QY of a sample in aqueous solution decreases minimally over 1 year. The enhanced stability and PL QY can be attributed to the water-induced methylamino lead bromide perovskite (MAPbBr3)@PbBr(OH). We note that this strategy is universal to MAPbBr3, formamidine lead bromide perovskite (FAPbBr3), inorganic lead bromide perovskite (CsPbBr3), etc. Light-emitting devices (LEDs) are fabricated by using the as-prepared perovskite as phosphors on a 365 nm UV chip. The luminance intensity of the LED is 9549 cd/m2 when the driven current is 200 mA, and blemishes on the surface of glass are clearly observed under the illumination of the LEDs. This work provides a new strategy for highly stable and efficient perovskites.

[Effect of Naoxintong Capsule on Inflammation in Peripheral Ischemic Tissue and Its Mechanism].

OBJECTIVE: To study the mechanism of naoxintong capsule (NXT) -inhibiting peripheral ischemic inflammation. METHODS: Mice were randomly double-blindly divided into 3 groups: sham-operation group, model group and NXT group. Both model and NXT groups underwent the hind limb ischemia (HLI) surgery followed by oral gavage with saline or NXT, respectively, one hour after operation. Three days after operation, the percentages of neutrophils and macrophages in the gastrocnemius muscle were examined by flow cytomety and immunohistochemical method. The changes in gene and protein expressions induced by NXT were examined by real-time PCR and protein chip, respectively. The changes of signaling pathways were analyzed. RESULTS: Compared with sham oparation and model groups, NXT could decrease the ratios of neutrophils and macrophages in gastrocnemius inflammation site (P＜0.01), and downregulate the mRNA expression of gene EMR1 (P＜0.01). NXT reduced the expression of TNF-α and IL-1ß at both mRNA (P＜0.001) and protein levels (P＜0.05). The proteomic analysis showed that the use of NXT resulted in the expression changes of 13 proteins. The expression of 6 cytokines was increased, and the secretion of 7 proteins was upregulated. Besides, most of identified 13 proteins were involved in the function regulation of other immune cells. CONCLUSION: NXT can significantly alleviate ischemia-induced peripheral inflammation by reducing the ratio of immune cells and altering the expression patterns of mRNA and protein. The expression changes provide theoretical guidance and the potential targets for the clinical use of NXT in the treatment of ischemia-induced peripheral inflammatory diseases.

Ultrasensitive Mechano-Stimuli Luminescence Enhancement in ZnO Nanoparticles.

Ultrasensitive mechano-stimuli photoluminescence enhancement was observed in pyramid-like zinc oxide nanoparticles (ZnO NPs), which are fabricated by a facile hydrothermal route. The response of the ZnO NPs to mechanical stimuli is so sensitive that even an ant walking and acoustic vibration can trigger the luminescence enhancement. The mechanism for this unusual behavior was attributed to the electron injection process between crystal boundaries. Thus, this work opens up the possibility of detecting slight mechanical stimuli wirelessly, rapidly, and sensitively. Importantly, the sensitive response of the NPs to sound waves can find potential application in devices for hearing-impaired people.

A self-calibrated luminescent thermometer based on nanodiamond-Eu/Tb hybrid materials.

Luminescent hybrid materials based on nanodiamonds (NDs) and rare earth ions have been successfully synthesized by covalently modifying NDs with pyromellitic acid (PMA) which is capable of coordinating to Eu3+ and Tb3+ ions. With NDs acting as a host matrix, the PMA and rare earth ions serve as an organic sensitizer and activator, respectively, yielding a highly bright hybrid composite. Interestingly, for the co-doped hybrid composites ND-PMA-Eu/Tb, the intensity ratio of the two emissions, 5D4→7F5 transition (Tb3+) to 5D0→7F2 transition (Eu3+), is linearly related to temperature in the range from 77 K to 277 K. Therefore, the hybrid could be developed as a self-calibrated ratiometric luminescent thermometer due to its temperature-dependent luminescence performance.

Multi-zinc oxide-cores@uni-barium sulfate-shell with improved photo-, thermal-, and ambient-stability: Non-equilibrium sorption fabrication and light-emitting diodes application.

ZnO as an eco-friendly material shows bright luminescence under UV illumination when it is tailored into nanoscale size, which makes it a promising luminescent nanomaterial. However, the poor stability of ZnO hinders its applications drastically. In this work, multi-ZnO-cores@uni-BaSO4-shell (mZnO@uBaSO4) nanocomposite has been prepared through a non-equilibrium sorption process employing ZnO QDs as the "seeds" and BaSO4 as the "valve". The mZnO@uBaSO4 nanocomposite shows improved photo-, thermal- and ambient-stability compare with bare ZnO QDs. The fluorescence efficiency of the mZnO@uBaSO4 nanocomposite decreases little even after 60 h of UV irradiation compare with ZnO QDs. The mZnO@uBaSO4 nanocomposite shows bright luminescence with little decrease even the ambient temperature up to 160 °C and the nanocomposite shows strong resistance to harsh environment. By coating the mZnO@uBaSO4 nanocomposite and commercial phosphors onto UV-chip, light-emitting diode (LED) with correlated color temperature, Commission Internationale de L'Eclairage coordinate, color rendering index and luminous efficiency of 6109 K, (0.32, 0.33), 85 and 47.33 lm/W have been realized, and this will make a great step towards eco-friendly UV-pumped LEDs.

Effect of multiple freezing-thawing cycles on structural and functional properties of starch granules isolated from soft and hard wheat.

Properties of starches isolated from soft and hard wheat dough after freezing/thawing (F/T) treatment were investigated. Significance of results was observed between isolated hard wheat starch (HWS) and soft wheat starch (SWS), but both cultivars showed an increase in the amounts of damaged starch and leaching proteins, lipids, and amylose with F/T cycles. The freezing-treated HWS exhibited a higher swelling power and peak, trough, breakdown and final viscosity than SWS after F/T treatment. The onset, peak and conclusion gelatinization temperatures and the enthalpy of the isolated HWS determined by differential scanning calorimetry, decreased throughout F/T cycles. Concomitantly, the bread containing freezing-treated HWS exhibited a lower bread specific volume and harder crumb firmness, which might be associated with its significant structural changes induced by F/T treatment.

[Analysis of retention of 3 different aesthetic Co-Cr-Mo alloy clasps on premolars].

PURPOSE: To analyze the retention of 3 different Co-Cr-Mo alloy clasps on premolars, and provide information for clinical design of aesthetic clasps. METHODS: An EZ20 force measuring instrument was used to record the retention of Co-Cr-Mo alloy casting aesthetic clasps when they were dislodged from undercuts of different depths (0.25, 0.50, 0.75 mm) on premolars. The data were analyzed with SPSS 22.0 software passage. RESULTS: The clasp retention in groups of 0.25 and 0.5 mm undercut was three-arm clasp > varied Y-shaped clasp > modified RPI clasp. In the group of 0.75 mm undercut, the clasp retention was varied Y-shaped clasp>three-arm clasp>modified RPI clasp after circulations. CONCLUSIONS: A varied Y-shaped bar clasp of 0.75 mm undercut depth is suitable for premolar both for its adequate retention and aesthetic effect.

[Effects of repeated firing on microleakage of selective laser melting ceramic crowns].

PURPOSE: To investigate the effects of repeated firing on microleakage of selective laser melting ceramic crowns. METHODS: Fifty molars were randomly divided into 2 groups (25 teeth in each group). Teeth in group A received a chamfer finish line preparation, whereas teeth in group B received a shoulder finish line. After SLM metal crowns were fabricated, all the crowns received initial oxidation step, opaque firing, dentin firing and glaze firing, then crowns in each group were randomly divided into 5 sub-groups according to different time of clinical firings. Glass ionomer was applied for bonding. After 5000 thermocycles ranging from 5degrees centigrade to 55degrees centigrade, all the specimens was evaluated by dye penetration and then microleakage was examined under light microscopy. The data were analyzed with SPSS 20.0 software package. RESULTS: Microleakage between all specimens of group A were not statistically significant (P>0.05) whereas that of group B were statistically significant (P<0.05); After the fifth time of clinical firing, microleakage of specimens in group B(B5) were significantly higher than that of group A(A5). CONCLUSIONS: Repeated firings had no significant influence on marginal microleakage of SLM ceramic crowns whereas the crowns of chamfer finish lines result in better clinical performance after repeated firings.