Estimation of stress distribution and risk of failure for maxillary premolar restored by occlusal veneer with different CAD/CAM materials and preparation designs.

OBJECTIVES: To compare stress distribution and failure probability in maxillary premolars restored by simple occlusal veneer (SOV) and buccal-occlusal veneer (BOV) with 3 different CAD/CAM materials. MATERIALS AND METHODS: A maxillary premolar was digitized by a micro-CT scanner. Three-dimensional dynamic scan data were transformed, and finite element models of 2 different models (SOV and BOV restored teeth) were designed. Three different CAD/CAM materials, including lithium disilicate glass ceramic (LD) IPS e.max CAD, polymer-infiltrated ceramic-network (PICN) Vita Enamic, and resin nano-ceramic (RNC) Lava Ultimate, were designated to both veneers. Maximum principle stresses were determined by applying a 300-N axial load to the occlusal surface. Weibull analyses were performed to calculate the failure probability of the models. RESULTS: LD-restored teeth showed the highest stress in the veneer, lowest stress in substrate teeth, and lowest failure probability for the overall system; RNC-restored teeth showed the lowest stress in the veneer, highest stress in substrate teeth, and highest failure probability. No significant differences were found in the cement layer among the different models. No significant differences of stress and failure probability existed between SOV and BOV preparations. CONCLUSIONS: CAD/CAM composite resin occlusal veneers bear lower maximum stress than ceramic veneers. Teeth restored by composite veneers are more prone to failure than those restored by ceramic veneers. Additional reduction of the buccal surface did not increase the stress on the occlusal veneer under axial load. CLINICAL RELEVANCE: Both occlusal veneers could be used under physiological masticatory force. CAD/CAM glass ceramic was safer than composite resins.

Incorporation of Stromal Cell-Derived Factor-1α in Three-Dimensional Hydroxyapatite/Polyacrylonitrile Composite Scaffolds for Bone Regeneration.

Bone regeneration strategies rely on biomaterial constructs with stem cells or growth factors. By comparison, cell homing strategies employ chemokines to recruit the host endogenous stem or progenitor cells to the defect site to support endogenous healing. In the present study, we used a novel fluffy hydroxyapatite/polyacrylonitrile (HA/PAN) composite scaffold to provide a better three-dimensional cell culture microenvironment. These HA/PAN composite scaffolds loaded with stromal cell-derived factor-1α (SDF-1α) provided a diffusion-controlled SDF-1α release profile and endowed the scaffolds with cell homing capabilities. Furthermore, the scaffolds significantly stimulated bone marrow stromal cell (BMSC) recruitment, facilitated BMSC osteogenic differentiation, and promoted ectopic bone formation. Our results suggest that a HA/PAN composite scaffold loaded with SDF-1α offers a clinically beneficial bone repair strategy.

Differentiated adipose-derived stem cell cocultures for bone regeneration in RADA16-I in vitro.

Craniofacial defects can cause morbidness. Adipose-derived stem cells (ADSCs) have shown great promise for osteogeneration and vascularization; therefore cocultures of differentiated ADSCs are explored to increase bone and vessel formation. In this study, ADSCs were induced into osteogenic ADSCs (os-ADSCs) and endothelial ADSCs (endo-ADSCs) cells, which were then cocultured in variable proportions (os-ADSCs/endo-ADSCs = 2:1, 1:1, 1:2). The os-ADSCs in a ratio of 1:1 expressed more ALP, RUNX2 and COL-I, whereas VEGF, vWF and CD31 were upregulated in the endo-ADSCs of this group. Next generation RNA sequencing (RNA-seq) was performed to evaluate the molecular mechanisms of cocultured ADSCs. The os-ADSCs and endo-ADSCs interacted with each other during osteogenic and angiogenic differentiation, especially at the ratio of 1:1, and were regulated by vascular-related genes, cell-mediated genes, bone-related genes and the transforming growth factor ß signaling pathway (TGF-ß), mitogen-activated protein kinase signaling pathway (MAPK) and wnt signaling pathway (Wnt). Angptl4, apoe, mmp3, bmp6, mmp13 and fgf18 were detected to be up-regulated, and cxcl12 and wnt5a were down-regulated. The results showed that the gene expression levels were consistent with that in RNA-seq. The cells were then seeded into self-assembling peptide RADA16-I scaffolds as cocultures (1:1) and monocultures (ADSCs, os-ADSCs, endo-ADSCs). The results showed that the cells of all groups grew and proliferated well on the scaffolds, and the cocultured group exhibited better osteogeneration and vascularization. In conclusion, cocultured os-ADSCs and endo-ADSCs at the ratio of 1:1 showed strong osteogenic and angiogenic differentiation. There is a great potential for osteogenesis and vascularization by 3D culturing cells in a 1:1 ratio in self-assembling peptide RADA16-I scaffolds, which requires evaluation for bone regeneration in vivo.

Burnout and study engagement among medical students at Sun Yat-sen University, China: A cross-sectional study.

This study aims to investigate burnout and study engagement among medical students at Sun Yat-sen University, China.A cross-sectional survey was conducted among undergraduate medical students of Sun Yat-sen University, China. A total of 453 undergraduate students completed a self-administered, structured questionnaire between January and February, 2016. Burnout and study engagement were measured using the Maslach Burnout Inventory-Student Survey (MBI-SS) and the UTRECHT Work Engagement Scale-Students (UWES-S), respectively. Subjects who scored high in emotional exhaustion subscale, high in cynicism subscale, and low in professional efficacy subscale simultaneously were graded as having high risk of burnout. Independent sample t tests and chi-square tests were used to compare the differences in burnout and work engagement between genders, majors, and grade levels.The means (standard deviations) of the MBI-SS subscales were 3.42 (1.45) for emotional exhaustion, 2.34 (1.64) for cynicism, and 3.04 (1.30) for professional efficacy. The means (standard deviations) of the UWES-S subscales were 3.13 (1.49) for vigor, 3.44 (1.47) for dedication and 3.00 (1.51) for absorption. Approximately 1 in 11 students experienced a high risk of burnout. There were no statistically significant gender differences in burnout and study engagement. There were also no statistically significant differences in burnout and study engagement subscales according to student major. Students in higher grades displayed increased burnout risk, higher mean burnout subscale score of cynicism, lower mean burnout subscale score of professional efficacy, and decreased mean study engagement subscale scores of dedication and absorption. There were strong correlations within study engagement subscales.Chinese medical students in this university experience a high level of burnout. Students at higher-grade level experience more burnout and decreased study engagement compared with students in lower level.

Evaluation of speech improvement following obturator prostheses for patients with palatal defect.

Palatal defect is a common maxillofacial defect after maxillectomy that can be repaired by obturator prostheses, which can effectively improve patients' speech. However, comprehensive evaluation methods for speech recovery are still controversial and remain undefined. A prospective cohort study on 34 patients with palatal defect and 34 healthy controls was performed. Patients received obturator prostheses and their speech was recorded without and then with obturators. Participants pronounced six Chinese vowels and 100 syllables for recording. This paper evaluated the recovery of speech function of patients through the combination of subjective and objective assessment methods. Recruited listeners evaluated the speech intelligibility (SI) of 100 syllables. Vowel formant frequency and quantified vowel nasalization were measured using analysis software. The SI of patients improved significantly after wearing obturators. F2 values of six vowels in patients with obturators were higher than patients without obturators and close to the corresponding values in normal controls. The differences in F2 of /i/ and /u/, (A1-P1) of /i/ and /u/ for patients without and with obturator use were significant. Patients' ability to control the pronunciation of /i/ and /u/ improved greatly with obturators. These provide clinical evidence of the treatment outcomes in patients with palatal defect who received obturators.