Teeth image segmentation has significant implications for various aspects of dental medicine, forensic odontology identification, scientific research, and education. However, the annotations made by radiologists may be subjective, and manual annotation requires a considerable amount of time and labor costs. In this paper, we propose deep-learning model VCMix-Net+ to achieve high-quality segmentation of 2D teeth images. Our VCMix-Net+ performs parallel operations of convolution and a multi-layer perceptron with class attention at multiple scales, simultaneously capturing both local and local-global information. Additionally, we have successfully reduced the annotation cost by employing a self-training semi-supervised approach. Our contribution lies in introducing a dedicated pseudo-label filtering network during the pseudo-label generation phase of semi-supervised training. This filtering network helps in selecting high-quality pseudo-labels, thereby reducing the risk of error accumulation in the self-training process. Meanwhile, we propose the concept of half-image training, which effectively improves the segmentation evaluation metrics. Finally, the average Score of our method's predicted results on the online test set is 92.89.

Background Microleakage is a common problem that affects the quality and longevity of all-ceramic crowns. It is influenced by factors such as the resin cement, crown margin design and curing technique. However, few studies focus on the effect of different methods of removing excess resin adhesive on the microleakage of all-ceramic crowns. This study aimed to compare two methods of removing excess resin adhesive (the small brush and sickle methods) on the microleakage of all-ceramic crowns with different marginal clearances. Methods Forty extracted third molars were prepared with a 90° shoulder margin and randomly divided into four groups according to their marginal lift (30, 60, 90 or 0 μm). Procera alumina crowns were fabricated using computer-aided design/computer-aided modelling and cemented onto the teeth with 3 M RelyX Unicem (3 M Company, United States) resin cement. Excess resin cement was removed by either the small brush or the sickle scalpel method. The marginal adaptation was observed with a digital microscope. After thermal cycling of the teeth, microleakage was assessed using the dye penetration test under a stereomicroscope. The Mann–Whitney U test and Kruskal–Wallis H test were used to compare the microleakage scores among different groups. Results The small-brush group showed significantly better marginal adaptation and lower microleakage scores than the sickle group ( p < 0.05). There was no significant difference in the microleakage score (grade 0) among different marginal clearances within each group ( p > 0.05). Conclusion The small-brush method was more effective than the sickle scalpel method in reducing the microleakage of all-ceramic crowns with different marginal clearances. This method can improve the marginal adaptation and sealability of all-ceramic crowns, thus preventing secondary caries and other complications.

Objective: The gut microbiota and its metabolites are important for host physiological homeostasis, while dysbiosis is related to diseases including the development of cancers such as colorectal cancer (CRC). In this study, we characterized the relationship of an altered gut microbiome with the fecal metabolome in CRC patients in comparison with volunteers having a normal colorectal mucous membrane (NC). Methods: The richness and composition of the microbiota in fecal samples of 30 CRC patients and 36 NC controls were analyzed through 16S rRNA gene sequencing, and the metabolome was determined by ultra-performance liquid chromatography coupled to tandem mass spectrometry. Spearman correlation analysis was to determine the correlation between the gut microbiome and fecal metabolome in CRC patients. Results: There were significant alterations in the gut microbiome and fecal metabolome in CRC patients compared with NC controls. Bacteroidetes, Firmicutes, Actinobacteriota, and Proteobacteria dominated the gut microbial communities at the phylum level in both groups. Compared with NC controls, CRC patients had a lower frequency of Blautia and Lachnospiracaea but a higher abundance of Bacteroides fragilis and Prevotella. Regarding the fecal metabolome, twenty-nine metabolites were identified as having significantly changed, showing increased levels of adrenic acid, decanoic acid, arachidonic acid, and tryptophan but a reduction in various monosaccharides in the fecal samples of CRC patients. Moreover, increased abundance of Bacteroides fragilis was strongly associated with decreased levels of monosaccharides, while Blautia was positively associated with the production of monosaccharides in the fecal samples. Conclusion: These results highlight alterations of gut microbiota in association with certain metabolites in CRC progression, implying potential diagnostic and intervention potential for CRC.

Characterizing the relationships between the water repellency and moisture permeability (breathability) of hydrophilic polyurethane and its supramolecular structure, including the phase inversion temperature in the soft phase, is unavoidable when developing intelligent, breathable textile products. In this study, a two-step technique was employed to prepare hydrophilic nonionic polyurethanes (PU) with various polyether (PE) soft segments. The hard segments of the samples were composed of 4,4 '-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO), while the soft segments consisted of polyethylene glycol 1000 (PEG), polytetramethylene glycol 1000 (PTMG), or their mixture. The relationships between the chemical and physical structure and the breathability were studied. The results showed that the samples with better separated structure between the soft and hard domains had a special microstructure of partial compatibility and simultaneously partial separation between the polyether soft and hard domains. In addition, the distribution of the mixed polyethers in the soft domains was homogeneous. The microphase structure, especially the hydrophilic ether bond content, exhibited a specific corresponding relevancy to the water resistance, moisture permeability and hydrophilicity of the PU membrane. The moisture permeability and water resistance were also directly related to their film-forming properties. Enhanced microphase separation intensified the positive effects of ether bonds on the moisture permeability, while worsened microphase separation weakened their negative influence on the water resistance/hydrophobicity.

Background and Aims: MicroRNA (miR)-497 is downregulated in several inflammatory diseases, excluding inflammatory bowel disease (IBD). The aim of this study is to evaluate whether miR-497 inhibits gut inflammation both in vivo and in vitro. Methods: The 3% dextran sulphate sodium (DSS) was used to induce experimental colitis, while 1 mu g/ml lipopolysaccharide (LPS) was for RAW264.7 cell damage. Colitis severity was evaluated by disease activity index (DAI), colon length, histopathologic injury, etc. The nuclear transcription factor NF-kappa B activity in colon tissues was also estimated by western blot. Then, the quantitative real-time polymerase chain reaction (qRT-PCR) was performed to evaluate the expression levels of miR-497, pro-inflammatory cytokines and chemokines in colon tissues and RAW264.7 cells. Furthermore, the activity of Wnt/beta-catenin pathway was determined by western blot and TOP/FOP-flash reporter assays. Results: The level of miR-497 was reduced in inflamed mucosa from IBD patients, mice with colitis and LPS-treated RAW264.7 cells. miR-497 knockout (miR-497 KO) mice were more susceptible to DSS-induced colitis, with increased inflammatory response, compared with control mice. Furthermore, the overexpression of miR-497 reduced the release of pro-inflammatory cytokines and chemokines in LPS-treated RAW264.7 cells. Finally, we found that miR-497 inhibited inflammation through Wnt/beta-catenin pathway both in vitro and in vivo. Conclusion: Our data indicate that miR-497 inhibits inflammation in DSS-induced IBD model mice and LPS-induced RAW264.7 cells by inhibiting the activation of NF-kappa B pathway and the release of cytokines, indicating that miR-497 plays a key role in the progression of IBD. Thus, therapeutic regulation of miR-497 expression may be beneficial for the treatment of IBD.

OBJECTIVE:Eradication of Helicobacter pylori (H. pylori) could not completely prevent the progression of gastric cancer (GC), suggesting that non-H. pylori bacteria may participate in the carcinogenesis of GC. The dysbiosis of microbiota in the stomach of GC has gradually been investigated, while the detailed mechanism that promotes GC in this process has not been elucidated. We aimed to identify a non-H. pylori bacteria that contribute to GC.DESIGN:GC tissues and adjacent normal tissues were collected to identify bacteria that significantly increased in GC tissues by 16S rRNA gene sequencing and fluorescence in situ hybridization (FISH) analysis. CCK8, wound healing assay, and trans-well assay were performed to analyze the tumor-promoting effect of this bacteria. Next, we detailed the mechanism for tumor-promoting effect of the bacteria by immunofluorescence, RT-qPCR, and western-blotting analysis.RESULTS:Comparing the microbial community from GC tissues and adjacent normal tissues, we found that Propionibacterium acnes (P. acnes) significantly increased in GC tissues, especially in H. pylori-negative tissues. We further found that the abundance of P. acnes correlated with TNM stages of GC patients. Interestingly, condition medium (CM) from P. acnes-primed macrophages promoted migration of GC cells, while P. acnes only could not. We next proved that P. acnes triggers M2 polarization of macrophages via TLR4/PI3K/Akt signaling.CONCLUSIONS:Together, our finding identified that P. acnes could be a possible agent for the progression of GC besides H. pylori. M2 polarization of macrophages could be promoted by P. acnes via TLR4/PI3K/Akt signaling, thus triggers the progression of GC.

Background Wingless and Int-related protein (Wnt) ligands were aberrantly expressed in human diseases. However, the aberrant level of Wnt ligands have not been explored in serum. Here, we aimed to identify the WNT4 level in serum and explore its oncogenic role in colorectal cancer (CRC). Methods Serum samples from 40 CRC patients and 28 healthy donors were collected to measure the levels of WNT4. CRC tissue samples from patients were collected to explore the resource of WNT4. Further, we used CRC cells and xenograft mouse model to explore the oncogenic role of WNT4. Results WNT4 was significantly upregulated in serum of colorectal cancer (CRC) patients, and CRC tissues were identified as an important source of elevated WNT4 levels in CRC patients. Interestingly, the elevated WNT4 in serum was downregulated after tumor resection. Next, we found that WNT4 could contributed to epithelial-to-mesenchymal transition and activated fibroblasts by activating WNT4/β-catenin pathway in vitro and in vivo; besides, angiogenesis was also induced via WNT4/β-catenin/Ang2 pathway. Those effects could be reversed by ICG-001, a β-catenin/TCF inhibitor. Conclusion These data indicated that WNT4 may be a potential biomarker for CRC and provided evidence to support a critical role of WNT4 in promoting CRC cell metastasis by inducing epithelial-to-mesenchymal transition, activating fibroblasts and promoting angiogenesis in the colorectal tumor microenvironment.

BACKGROUND/PURPOSE:Color errors associated with the visual color duplication approach for ceramic laminate veneers are still challenging in esthetic dentistry. The aim of this study is to evaluate color errors generated during traditional visual shade matching approach.MATERIALS AND METHODS:Eighteen stooth-shaped veneer discs (shade A2 and 0.7 mm in thickness) were fabricated using six veneer materials. The veneer specimens placed on five extracted teeth with nominal shade A2 formed veneer-tooth combinations. Color coordinates of the A2 shade tab, the extracted teeth, and the veneer-tooth combinations were measured using a spectrophotometer. Then, the veneers were reduced to 0.5 mm, and 0.3 mm in thickness consecutively. Color measurements were performed repeatedly. Color differences of the extracted teeth to veneer-tooth combinations (ΔEt-v), veneer-tooth combinations to shade tab (ΔEv-s), and translucency parameter (TP) values were calculated and analyzed using Two-way ANOVA.RESULTS:ΔEt-v ranged from 2.0937 to 5.0603 (mean of 3.1833±1.5485). Mean of ΔEv-s was 4.0103±1.8508. ΔEt-v and ΔEv-s values were significantly influenced by veneer material and thickness (P<0.05). TP values decreased gradually with the lessening of veneers thickness.CONCLUSION:Acceptable color duplication of ceramic veneers cannot be achieved by routine visual shade replica protocols, when the thickness of veneers is less than 0.7 mm. Specified color matching standards for the ceramic veneers are needed.

BACKGROUND/PURPOSE:Significant research has proposed that the implant with microthread in the neck can significantly reduce marginal bone loss, but whether it is consistent in the condition of marginal bone loss is still unknown. The objective of this study is to investigate the effect of microthread on stress distribution in peri-implant bone with different bone level using finite element analysis.MATERIALS AND METHODS:A series of computational models of mandible segments with different bone resorption and implant models with or without microthread in the neck was installed by computer-aided design software. The simulated occlusal force of 150N was applied buccolingually on the top center point of implant. The FEA was performed, and the von Mises stress, principal stress and shear stress in peri-implant bone were recorded and analyzed.RESULTS:In all models, the T-neck group exhibits higher von Mises stress and principal stress, as well as lower shear stress than S-neck group. Three types of stresses increase with the depth of bone resorption developed, but the differences of shear stress between two groups of implants were gradually decreased.CONCLUSION:The micro-thread design in implant neck can reduce marginal bone loss by decreasing shear stress in peri-implant bone, but this effect is gradually weakened with the decline of the marginal bone level.

Background : Wingless and Int-related protein (Wnt) ligands are aberrantly expressed in patients with colorectal cancer (CRC). However, the aberrant level of Wnt ligands in serum have not been explored. Here, we aimed to identify the levels of WNT4 in serum and explored its oncogenic role in CRC Methods : The Oncomine database was used to analyze the relationship between WNT4 and the prognosis of CRC. ELISA was performed to measure WNT4 levels in serum and conditioned medium from fresh CRC tissues and adjacent normal tissues. Western blot and immunohistochemistry were carried out to measure the expression of WNT4 in human CRC tissues and adjacent normal tissues. The migration and invasion of CRC cells were determined by trans-well assay, and the effects of WNT4 on CRC invasion and metastasis in vivo were verified by tumor xenograft in nude mice. Cancer-associated fibroblasts (CAFs) and angiogenesis in subcutaneous nodules were detected by immunofluorescence (IF). In addition, the suspended spheres formation and tube formation assay were performed to explore the effects of WNT4 on CAFs and angiogenesis respectively. Results : WNT4 was significantly upregulated in serum of CRC patients, and CRC tissues were identified as an important source of elevated WNT4 levels in CRC patients. Interestingly, elevated levels of WNT4 in serum were downregulated after tumor resection. Furthermore, we found that WNT4 contributed to epithelial-to-mesenchymal transition (EMT) and activated fibroblasts by activating the WNT4/β-catenin pathway in vitro and in vivo. Moreover, angiogenesis was induced via the WNT4/β-catenin/Ang2 pathway. Those effects could be reversed by ICG-001, a β-catenin/TCF inhibitor. Conclusion : Our findings indicated that serum levels of WNT4 may be a potential biomarker for CRC. WNT4 secreted by colorectal cancer tissues promote the progression of CRC by inducing EMT, activate fibroblasts and promote angiogenesis through the canonical Wnt/β-catenin signalling pathway.

随着人们对口腔美学要求的不断提高,全瓷修复成为当前口腔固定修复的主要趋势.但是,由核瓷与饰面瓷构成的全瓷修复体的力学强度仍是人们关注的问题之一.因此,如何更好地设计全瓷修复体以应对口腔较为复杂的咬合力将显得格外重要,尤其是核瓷与饰面瓷厚度改变时,修复体抗弯强度将如何变化依旧没有定论.目前,已有不少关于这方面的研究,但各研究之间的实验设计、背景、方法等并不相同,本文将对这些差异性因素进行介绍与分析.

PURPOSE:To explore the feasibility of a novel computer color-matching (CCM) system based on the improved back-propagation neural network (BPNN) model by comparing it with the traditional visual method. MATERIAL AND METHODS:Forty-three metal-ceramic specimens were fabricated by proportionally mixing porcelain powders. Thirty-nine specimens were randomly selected to train the BPNN model, while the remaining four specimens were used to test and calibrate the model. A CCM system based on the improved BPNN model was constructed using MATLAB software. A comparison of the novel CCM system and the traditional visual method was conducted by evaluating the color reproduction results of 10 maxillary central incisors. Metal-ceramic specimens were fabricated using two color reproduction approaches. Color distributions (L*, a*, and b*) of the target teeth and of the corresponding metal-ceramic specimens were measured using a spectroradiometer. Color differences (ΔE) and color distributions (ΔL*, Δa*, and Δb*) between the teeth and their corresponding specimens were calculated. RESULTS:The average ΔE value of the CCM system was 1.89 ± 0.75, which was lower than that of the visual approach (3.54 ± 1.11, p < 0.01). With respect to color distributions, substantial differences were found between the two color-matching systems, except for ΔL* (p > 0.05). CONCLUSION:The novel CCM system produced greater accuracy in color reproduction within the given color space than the traditional visual approach.

目的:研究Nacera两种氧化锆的透明度和与Vita标准比色板A2色片的色差.方法:用CAD/CAM(computer aided design&manufacturing)将彩晶高透(Nacera Pearl)和彩晶低透(Nacera Shell)的氧化锆块加工成不同厚度(0.5、0.8、1.0、1.5 mm)的圆盘形核心瓷块,然后在核心瓷上烧结厚度分别为1.0、0.7、0.5、0 mm的A2饰瓷(Noritake Kizai Co,Ltd,Nagoya,Japan),最后上釉.共制作40片直径为10.0 mm、总厚度为1.5 mm的氧化锆基底瓷片(n=5).采用PR-655分光光度计测量试件在标准黑白板及4.0mm厚Dentin色树脂背景下的色度值,用来计算试件的相对透明度(translucency parameters,TP)值和与Vita Lumin Vacuum比色板A2色片的色差(△E).结果:Nacera Shell组的TP值明显小于Nacera Pearl组.Nacera Pearl组随着核心瓷厚度增大,试件颜色与A2色片的色差变大,而Nacera Shell组的色差变化相对较小.结论:Nacera品牌的两种氧化锆均能较好地模拟比色板A2色片的颜色,但并非透明度越高的氧化锆最终修复颜色越好.

BACKGROUND: CD4(+) T-helper cell is crucial for the inflammatory autoimmune condition of oral lichen planus (OLP). Recently, the pathogenetic functions of T follicular helper (Tfh) cells, a subtype of CD4(+) T-helper cells, have been revealed in autoimmune diseases for their pivotal regulation on humoral immunity. To explore the potential pathophysiological role of Tfh cells in OLP, the expression of circulating Tfh-like cells and its correlations with IL-21 and B cells were investigated. METHODS: The frequencies of CXCR5(+) CD4(+) Tfh-like cells and CD19(+) B cells were analyzed in peripheral blood of patients with OLP and controls by flow cytometry, respectively. Besides, the serum IL-21 concentration was measured using ELISA technology. Furthermore, the correlations of CXCR5(+) CD4(+) Tfh-like cells with CD19(+) B cells and serum IL-21 expression levels were evaluated. RESULTS: This study showed significant increased circulating Tfh-like cells (P < 0.05) and B cells (P < 0.0001), as well as decreased serum IL-21 expression (P < 0.001) in OLP. Besides, the frequency of Tfh-like cells exhibited negative correlation with B cells in OLP (r = -0.435, P < 0.05). In particular, the proportion of CXCR5(+) CD4(+) Tfh-like cells in peripheral blood mononuclear cells of erosive OLP was higher than non-erosive OLP and controls (P = 0.012 and 0.021, respectively). CONCLUSIONS: Increased circulating Tfh-like cells may be involved in the pathogenesis of OLP through abnormal modulation on B-cell proliferation and IL-21 production, and associated with different clinical forms of OLP.

PURPOSETo investigate the color differences of ceramic veneers and the intended shade tab, and evaluate the effects of luting composites on the resultant colors of ceramic veneers.MATERIALS AND METHODSPressable leucite-reinforced feldspathic ceramic discs (IPS e.max), with nominal shade A3, were fabricated with thicknesses of 1.0 mm, 0.7 mm, and 0.5 mm (n = 10/ thickness). The ceramic specimens were cemented onto a composite background (shade Dentin) using a veneer adhesive system with five colors of luting composites (RelyX). The colors of the veneer (veneer/luting/background complexes) and corresponding shade tab (A3, Vitapan) were measured using a spectrophotometer, and subsequently converted to CIE L*a*b* values. Color differences (△E) between each complex and the shade tab were calculated and analyzed with two-way ANOVA. Tukey's multiple comparisons were used to evaluate the effects of luting composites on the △E values.RESULTSThe means of color differences between ceramic veneers and intended shade tab were 2.50 ± 0.38, 3.17 ± 0.48, and 3.84 ± 0.63 for the 1.0 mm, 0.7 mm, and 0.5 mm thicknesses, respectively. △E values were significantly affected by the veneer thickness and the luting composite color (p < 0.001). Tukey's multiple comparison results revealed no significant differences among the luting composites in the thickness of 1.0 mm and 0.7 mm.CONCLUSIONSThe color matching of ceramic veneers to the intended shade tab was not achieved in the 0.7 mm and 0.5 mm veneer thicknesses, whichever colors of the luting composites were used.

OBJECTIVE:This study aimed to explore the chemical changes and discoloration of endodontically treated teeth using spectroradiometric and chemical analyses.METHODS AND MATERIALS:Ten freshly extracted sound third molars and 10 discolored molars obtained after root canal treatment (RCT) were included in this study. Dentin blocks (3 × 3 × 1 mm) were prepared and treated with an intracoronal bleaching agent. Spectroradiometric evaluations, X-ray photoelectron spectroscopy (XPS), and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analyses were performed before and after bleaching. The spectroradiometric parameters and XPS and ATR-FTIR spectra of the dentin slabs were analyzed using independent-sample t-tests or one-way analysis of variance.RESULTS:Differences in color coordinates and translucency parameters were observed between the two groups before bleaching. Demineralization effects were also detected in the discolored dentin. No binding energy shifts or new spectral bands were found in the XPS and ATR-FTIR spectra, except in the narrow-scanned XPS spectra of C1s. Significant changes in color coordinates were also found in both groups after bleaching, and the translucency parameter was remarkably altered in discolored dentin. The organic and inorganic components of dentin also decreased in both groups. However, binding energy shifts (ie, C1s, Ca2p, and P2p) were detected only in discolored dentin.CONCLUSION:Significant alterations in the organic and inorganic components of dentin contributed to the discoloration of endodontically treated teeth. Moreover, intracoronal bleaching could effectively whiten both discolored and vital dentin. The chemical compositions of mineral and organic components within discolored dentin are more sensitive to the acid bleaching agent than normal teeth.

目的:研究纤维桩直径和肩领高度对桩核修复体抗折能力的交互影响.方法:60颗上颌中切牙切除牙冠部分,按邻面釉-牙骨质界上残余牙体高度分为0 mm、1 mm、2 mm、3 mm四组(n=15).按照常规桩核修复技术,使用Macro Lock纤维桩(2#,3#和4#)制作试样.采用静态折裂实验获取各试样的最大折裂力;通过断口图像分析试样折裂情况.双因素方差分析肩领高度和纤维桩直径对试样抗折能力的影响.结果:双因素方差分析结果显示肩领高度和纤维桩直径存在明显交互作用(P=0.006).在0 mm和1 mm组,增加纤维桩直径能显著提高试样抗折能力;在2 mm组,使用2#和3#纤维桩时,试样抗折力无显著差异;在3 mm组,不同直径纤维桩对试样抗折力均无显著影响.结论:纤维桩直径对于桩核修复体抗折能力的影响随着肩领高度增加而减弱.增加肩领高度能有效提高桩核修复体抗折能力.

The aim of the present study was to investigate the effects of low-temperature aging on the micro-mechanical and micro-structural properties of zirconia-porcelain interface. In total, thirty-three Y-TZP zirconia blocks were fabricated by using CAD/CAM technology, veneered with porcelains. Specimens were submitted to low-temperature aging in an autoclave at 134°C, additional 0.2MPa pressure for 0h, 5h, or 10h. Flexural strength was obtained by using three-point bending test. Micro-mechanical properties (nano-hardness (H) and reduced modulus (Er)) were investigated by nanoindentation tests. Scanning electron microscopy and X-ray diffraction analyses were performed to identify the micro-structure and fracture behavior. The flexure strength, modulus and hardness of zirconia increased after 5h aging and decreased after 10h aging. No significant alterations of the reduced modulus or hardness of porcelain were detected in the whole aging duration. Width of the zirconia-porcelain interface was extended towards the bulk of zirconia. The detachment and cracks could be observed in zirconia, and the crystal alignment was disorganized in porcelain after 5h aging and 10h aging. Mechanical properties of the veneering porcelain are not affected by low-temperature aging. However, the expansion and the alterations of micro-mechanical and micro-structural properties of zirconia-porcelain interface were detected.

Mechanical failure of biomaterials, which can be initiated by either violent force, or progressive stress fatigue, is a serious issue. Great efforts have been made to improve the mechanical performances of dental restorations. Virtual simulation is a promising approach for biomechanical investigations, which presents significant advantages in improving efficiency than traditional in vivo/in vitro studies. Over the past few decades, a number of virtual studies have been conducted to investigate the biomechanical issues concerning dental biomaterials, but only with limited incorporation of brittle failure phenomena. Motivated by the contradictory findings between several finite element analyses and common clinical observations on the fracture resistance of post-restored teeth, this study aimed to provide an approach using numerical simulations for investigating the fracture failure process through a non-linear fracture mechanics model. The ability of this approach to predict fracture initiation and propagation in a complex biomechanical status based on the intrinsic material properties was investigated. Results of the virtual simulations matched the findings of experimental tests, in terms of the ultimate fracture failure strengths and predictive areas under risk of clinical failure. This study revealed that the failure of dental post-restored restorations is a typical damage-driven continuum-to-discrete process. This approach is anticipated to have ramifications not only for modeling fracture events, but also for the design and optimization of the mechanical properties of biomaterials for specific clinically determined requirements.

Objectives: To evaluate the fracture resistance of fibre post-restored teeth with various ferrule configurations by using fracture failure tests and extended finite element analysis (XFEM).Methods: 60 Maxillary central incisors were collected and divided into six groups (n = 10) according to various ferrule configurations with different ferrule heights in the labial or palatal region. All of the teeth were endodontically treated and restored by using fibre posts, composite cores and metal crowns. Fracture failure tests were performed on the post retained restorations until fracture occurred. The ultimate load was recorded and analyzed by one way analysis of variance (ANOVA). The fractured specimens were longitudinal sectioned and investigated by micro-stereomicroscope and scanning electronic microscope. XFEM was used to model the fracture of the post-restored teeth and exhibit crack initiation and propagation in the cement layers.Results: Fracture failure tests indicated that the palatal ferrule significantly enhanced the fracture resistance of the post-restored teeth, regardless the height of the labial ferrule. The fractography investigation exhibited that the crack initiated at the palatal margin of the cement layer and propagated to the cervical region of the root. XFEM confirmed these findings and demonstrated that increasing of the palatal ferrule could effectively enhance the anti-fracture ability of the adhesive cement and protected the integrity of adhesive cement.Conclusion: Adhesive interface was the susceptible structure of the post retained restorations. Increasing palatal ferrule height could effectively reduce the stress concentrated within the palatal adhesive cement.Clinical Significance: "Ferrule effect'' exhibits the protection of the interity of cement layer. Increasing the ferrule height, especially in the palatal side, can significantly enhance the anti-fracture ability of fibre post-restored teeth. (C) 2014 Elsevier Ltd. All rights reserved.