Minimal tooth preparation for posterior monolithic ceramic crowns: Effect on the mechanical behavior,reliability and translucency

ObjectiveDespite the increased use of monolithic crowns, their performance has yet to be determined when the minimal tooth preparation (MTP) principle is considered. The goal of this study was to evaluate the effect of MTP on the mechanical behavior, reliability and translucency of posterior monolithic ceramic crowns.MethodsDentin analogues were machined using two preparation designs (0.5 or 1 mm reduction) to receive first molar crowns in order to evaluate the monolithic crown performance. Next, 126 crowns were divided (21/g) according to the material (High translucent zirconia – YZHT, Zirconia reinforced lithium silicate – ZLS and Hybrid ceramic – HC) and thickness (0.5 or 1 mm). Tensile stress concentration was calculated using the finite element method. The crowns were adhesivelly cemented and step stress fatigued to calculate reliability for missions at 600 and 1000 N. Translucency was analyzed in 10 discs of each material and thickness.ResultsHigher stress concentration was found in thinner crowns and those with higher elastic modulus. YZHT crowns were suspended when fatigue reached 1500 N load, thus 1-parameter Weibull was used to analyze the data. Reliability was only affected by thickness at 1000 N. ZLS.5 showed lower survival than HC.5, which was similar to the groups that presented 100% survival. YZHT showed the highest strength and data scattering. ZLS1 (22.3 ± 1.4) presented higher translucency than HC1 (19.2 ± 0.6) and YZHT1 (12.0 ± 2.9), whereas ZLS.5 and HC.5 were similar to each other (26.5 ± 2.3, 26.7 ± 2.2) and superior to YZHT.5 (12.7 ± 1.2).SignificanceHC.5 combined high reliability and translucency with low stress concentration, yielding better crown performance and tooth preservation.     

Survival probability of zirconia-reinforced lithium silicate ceramic: Effect of surface condition and fatigue test load profile

ObjectivesThe present investigation evaluated the step stress accelerated test (SSALT) load profiles on the survival probability of a glass ceramic under two surface conditions (polished or roughened).MethodsSuprinity–ZLS blocks (Vita Zhanfabrik) were shaped into cylinders, cut in a sawing machine, and crystalized according to the manufacturer's instructions. 60 discs were obtained (Ø = 12 mm, thickness = 1.2 mm) and randomly assigned into two surface conditions: “p” polished surface (400–1200-grit SiC papers), and “r” roughened surface (200-grit SiC papers). Profilometry was performed in all discs to evaluate average surface roughness prior to flexural fatigue strength testing. 3 discs of each group were submitted to biaxial flexural strength in an universal testing machine (0.5 mm/min) and the mean load to failure (N) was calculated to determine SSALT profiles. 27 specimens per surface condition were assigned into three profiles – Mild (n = 9), Moderate (n = 9), and Aggressive (n = 9), and submitted to the fatigue test (60–320 N, 140,000 cycles at 1.4 Hz). The results were analyzed using the Kaplan-Meier and Wilcoxon tests (5%), 2-way ANOVA and Tukey test (α = 5%).ResultsKaplan-Meier and generalized Wilcoxon showed (P = 0.002) that polished groups showed higher survival probability than roughened condition (P < 0.05). A rough internal surface impacted deleteriously on the fatigue strength and reliability of ZLS ceramic. Both surface conditions were more sensitive to the aggressive profile than the other profiles, even worst for the roughened group. Regardless the load profile, 0% survival probability was observed at 384 MPa for polished condition. While for roughened, aggressive tested specimens did not survived 147 MPa followed by moderate at 312 MPa and mild at 384 MPa. The failure modes showed fracture marks originating from superficial grooves for both surface conditions.SignificancePolished specimens are sensitive to the load profile variation, confirming the effect of surface morphology on the fatigue results.     

Cyclic contact fatigue resistance of ceramics for monolithic and multilayer dental restorations

ObjectiveTo evaluate the cyclic contact fatigue resistance and failure mode of ceramics for monolithic and multilayer restorations.MethodsCeramic structures (10 mm × 1.8 mm) were fabricated as follows (n = 28): (1) CAD-on- trilayer structure composed of Y-TZP (yttria stabilized tetragonal zirconia polycrystal- IPS e.max ZirCAD) infrastructure, fusion glass–ceramic (IPS e.max CAD Crystall/Connect) and lithium disilicate-based glass–ceramic (IPS e.max CAD); (2) ZFC- bilayer structure composed of Y-TZP infrastructure veneered by a fluorapatite glass–ceramic (IPS e.max Ceram); (3) LDC- monolithic lithium-disilicate glass–ceramic (IPS e.max CAD); and (4) YZW- monolithic Y-TZP (Zenostar Zr Translucent). All ceramics structures were bonded to a dentin analog substrate (G10). Specimens were submitted to cyclic contact fatigue test in a pneumatic cycling machine with 80 N load and 2 Hz frequency in distilled water at 37 °C. Test was interrupted after 10⁴, 10⁵, 5 × 10⁵ and 10⁶ cycles and the presence or absence of failure was recorded. Fatigue data were analyzed using Kaplan–Meier (log rank) and Holm–Sidak tests (α = 0.05). The relationship between the type of crack leading to failure and the experimental group was analyzed using chi-square test (α = 0.05).ResultsThere was no statistical difference between CAD-on and YZW groups (p = 0.516), which presented the highest survival rates after cyclic loading, followed by ZFC and LDC groups (p < 0.01). There was a significant relationship between type of crack and experimental group (p < 0.001). LDC specimens showed the greatest frequency of radial cracks, while cone cracks were more prevalent for ZFC and CAD-on specimens.SignificanceMonolithic Y-TZP (YZW) showed similar fatigue resistance to CAD-on multilayer specimens, but different failure mode. Monolithic lithium disilicate glass–ceramic (LDC) and Y-TZP conventionally veneered by glass–ceramic (ZFC) showed lower survival time under fatigue.     

A randomized clinical trial on the efficacy of a patient-adapted autonomous exercise regime for patients with head and neck cancer

Patients undergoing surgical therapy of head and neck malignancies are known to exhibit a high number of comorbidities and frequently present a high nosocomial morbidity. Physiotherapy (PT) improves the clinical course of patients after extensive surgery. The aim of this study was to establish and then compare an additional individualized autonomous exercise plan with standard physiotherapy. 69 consecutive patients undergoing surgical treatment of head and neck cancer were randomized into two groups. The control group received standard clinical physiotherapy, the intervention group an additional autonomous exercise plan, adapted to the patient's performance profile. The patients randomized to the intervention group showed significantly fewer signs of fatigue (5.5 ± 3.5 vs. 3.7 ± 2.7, p = 0.048) and fewer digestive problems (4.7 ± 3.3 vs. 2.3 ± 2.7; p = 0.009) compared with the patients of the control group. In addition, a significantly shorter hospital stay was observed (17.7 ± 6.3 vs. 13.4 ± 3.4 days, p = 0.005), which was positively influenced by the early start of the exercises (r = 0.623, p = 0.001) and frequent practice (r = 0.432, p = 0.031). Patients with head and neck cancer therapy can benefit from an autonomous, individualized exercise plan. In coordination with the physiotherapists, mobilization should be as early and intensive as possible.     

Neurophysiological Correlates of Fatigue in Multiple Sclerosis

Examining fatigue may be beneficial for nurse practitioners to intervene in the care of patients with multiple sclerosis (MS). We measured the relationship of fatigue severity with event-related potentials during electroencephalogram and diffusion basis spectrum imaging/magnetic resonance imaging in 11 participants with relapsing-remitting MS and 5 healthy controls. Data were analyzed to measure brain activity during event-related potentials to responses to cue (correct response) and distractor (incorrect response) using a cognitive performance task. Nurse practitioners caring for patients with MS have an important role in monitoring fatigue severity.     

Prevalence and Risk Factors for Fatigue in Adults With Inflammatory Bowel Disease: A Systematic Review With Meta-Analysis

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全科专业住院医师规范化培训学员职业倦怠及其影响因素研究

背景　全科医师是初级医疗保健体系和分级诊疗的重要支点,全科专业住院医师规范化培训（以下简称全科住培）是培养高素质全科医师最重要的渠道,但目前我国的执业现状使学员易产生职业倦怠,分析其职业倦怠影响因素可为完善全科住培管理和壮大全科医师队伍提供依据。目的　了解全科住培学员职业倦怠现状,并分析其影响因素。方法　2019年3-4月,从江苏省13个市各抽取1家国家级全科住培基地,基地内全科学员全样本调查,共抽取682名学员。采用自制社会人口学调查表、职业倦怠普适量表调查学员的职业倦怠情况,采用多元线性回归分析探讨全科住培学员职业倦怠的影响因素。结果　共发放问卷682份,回收有效问卷604份,有效问卷回收率为88.6%。职业倦怠3个维度情绪耗竭维度得分为（15.34±7.02）分、去个性化维度得分为（9.17±6.36）分、个人成就感低落维度得分为（13.61±8.12）分。零倦怠检出率为43.7%（264/604）,轻度职业倦怠检出率为27.3%（165/604）,中度职业倦怠检出率为21.5%（130/604）,重度职业倦怠检出率为7.5%（45/604）。体育锻炼次数、睡眠时长是全科住培学员情绪耗竭的影响因素（P<0.05）;学历、体育锻炼次数、睡眠时长、参加住培年度、收入水平是全科住培学员去个性化的影响因素（P<0.05）;性别、身份归属和体育锻炼次数是全科住培学员个人成就感低落的影响因素（P<0.05）。结论　全科住培学员职业倦怠检出率较高。体育锻炼次数、睡眠时长、参加住培年度、收入水平、学历、性别、身份归属是全科住培学员职业倦怠的影响因素。建议加强全科住培学员体育锻炼和心理建设、探索构建“行业社会人”的培养模式、夯实基层基地的建设、提高全科住培学员薪资待遇等,来缓解或降低其职业倦怠程度。