Composite polymerization stress as a function of specimen configuration assessed by crack analysis and finite element analysis

Objectives

To test the null hypothesis that polymerization-induced stress was not influenced by cavity dimensions and geometries.

Methods

Four experimental groups, with different C-factors and specimen volumes were defined using bottom-less glass disks (height: 1 or 2 mm) with a central hole 3 or 6 mm in diameter, and 3 mm wall thickness. Another four groups were created by bonding a glass plate to the bottom of the disks. Additionally, disks with 2-mm height, 3 mm in cavity diameter, and 4.5-mm thick walls were prepared. Vickers indents (9.8 N, 20 s) were made at the top surface at 600 μm from the cavity margin. The lengths of the indentation diagonal and the corner cracks parallel to the cavity margin were measured. Ten minutes after restoration (Majesty Esthetic, Kuraray), cracks were re-measured. Stresses at the indent site were calculated based on glass fracture toughness and increase in crack length. Data were subjected to ANOVA/Tukey or Kruskal–Wallis/Mann–Whitney tests (alpha: 5%, n = 8). Finite element analysis (FEA) was used to estimate stress at the interface and the effective structural rigidity of the substrate.

Results

Overall, for experimental and FEA results, cavities developed higher stress than bottom-less disks. Increasing wall thickness did not affect stress. When similar geometries and C-factors were compared, higher volumes developed higher stress and had greater incidence of margin cracking.

Clinical significance

C-factor is a suitable predictor for polymerization stress in low compliance environments, particularly due to its simplicity. However, the influence of cavity size cannot be disregarded especially for the development of marginal cracking. The interaction between size, geometry and stiffness is likely to become more complex according to the complexity of the cavity shape.     

Influence of hydration and mechanical characterization of carious primary dentine using an ultra-micro indentation system (UMIS)

The conditions under which mechanical properties of dentine are tested influence the values recorded. The aims of this study were to examine the effect of hydration on the mechanical properties of primary carious dentine and to provide information on changes in hardness and modulus of elasticity change caused by the demineralizing caries process in dentine. Three primary molar teeth with untreated carious dentine were prepared for nano-indentation tests under both wet and dry conditions. Further tests were conducted on eight primary molars with untreated carious dentine under hydrated conditions. The mechanical properties of dehydrated carious dentine increased approximately 10-fold for hardness and 100-fold for the modulus of elasticity compared with hydrated dentine. The hardness and elastic modulus of the carious primary dentine deteriorated progressively toward the lesion cavity floor, ranging from 0.001 to 0.52 GPa and from 0.015 to 14.55 GPa, respectively, and could be fitted to a simple linear relationship when plotted in logarithmic scale vs. distance. The total depth of dentine affected was around 1100 microm parallel to the tubule direction. This depth was significantly greater than observed subjectively, implying that the demineralization process is more advanced than might be suspected on simple clinical examination.     

Endoscopic mucosal resection of 161 cases of large sessile or flat colorectal polyps

Objective. Large sessile or flat colorectal polyps, which are traditionally treated surgically, may be amenable to endoscopic mucosal resection (EMR), often using a piecemeal method. Appropriate selection of lesions and a careful technique may enhance the efficacy of EMR for polyps ≥20 mm in diameter without compromising safety. The aim of this study was to identify the factors that may be predictive of the risk of polyp recurrence. Material and methods. A retrospective analysis was conducted on the outcome of 161 polyps ≥20 mm in diameter, treated by piecemeal EMR at a single centre using the “lift and cut” technique. All records were reviewed for polyp size, site, morphology and histology. Polypectomy technique, patient follow-up, polyp recurrence and surgical interventions were also recorded. Results. Over an 8-year period, 161 colonic polyps measuring ≥20 mm were removed by EMR. Follow-up data were available for 149 cases (93%) with a mean polyp diameter of 32.5 mm; the total success rate of endoscopic polyp removal was 95.4%. The number of cases requiring 1, 2, 3, 4 and 6 attempts at EMR was 89 (60%), 36 (24%), 14 (9%), 2 (1.3%) and 1 (0.7%), respectively. Recurrence was significantly related to polyp size (p<0.001). There was no statistically significant relationship between site and recurrence. Seven patients (4.6%) underwent surgical intervention after EMR because of failed clearance. There were no post-EMR perforations and significant bleeding was reported in only two patients (1.7%). Conclusions. With careful attention to technique, piecemeal EMR is a safe option for the resection of most sessile and flat colorectal polyps ≥20 mm in size. A stricter follow-up may be required for larger lesions because of a higher risk of recurrence.     

Risk factors for mortality in patients with alcoholic hepatitis and assessment of prognostic models: A population-based study

BACKGROUND:

Severe alcoholic hepatitis (AH) is associated with a substantial risk for short-term mortality.

OBJECTIVES:

To identify prognostic factors and validate well-known prognostic models in a Canadian population of patients hospitalized for AH.

METHODS:

In the present retrospective study, patients hospitalized for AH in Calgary, Alberta, between January 2008 and August 2012 were included. Stepwise logistic regression models identified independent risk factors for 90-day mortality, and the discrimination of prognostic models (Model for End-stage Liver Disease [MELD] and Maddrey discriminant function [DF]) were examined using areas under the ROC curves.

RESULTS:

A total of 122 patients with AH were hospitalized during the study period; the median age was 49 years (interquartile range [IQR] 42 to 55 years) and 60% were men. Median MELD score and Maddrey DF on admission were 21 (IQR 18 to 24) and 45 (IQR 26 to 62), respectively. Seventy-three percent of patients received corticosteroids and/or pentoxifylline, and the 90-day mortality was 17%. Independent predictors of mortality included older age, female sex, international normalized ratio, MELD score and Maddrey DF (all P<0.05). For discrimination of 90-day mortality, the areas under the ROC curves of the prognostic models (MELD 0.64; Maddrey DF 0.68) were similar (P>0.05). At optimal cut-offs of ≥22 for MELD score and ≥37 for Maddrey DF, both models excluded death with high certainty (negative predictive values 90% and 96%, respectively).

CONCLUSIONS:

In patients hospitalized for AH, well-known prognostic models can be used to predict 90-day mortality, particularly to identify patients with a low risk for death.     

The human gut microbiome and health inequities

Individuals who are minoritized as a result of race, sexual identity, gender, or socioeconomic status experience a higher prevalence of many diseases. Understanding the biological processes that cause and maintain these socially driven health inequities is essential for addressing them. The gut microbiome is strongly shaped by host environments and affects host metabolic, immune, and neuroendocrine functions, making it an important pathway by which differences in experiences caused by social, political, and economic forces could contribute to health inequities. Nevertheless, few studies have directly integrated the gut microbiome into investigations of health inequities. Here, we argue that accounting for host–gut microbe interactions will improve understanding and management of health inequities, and that health policy must begin to consider the microbiome as an important pathway linking environments to population health.     

Endoscopic mucosal resection of 161 cases of large sessile or flat colorectal polyps

OBJECTIVE: Large sessile or flat colorectal polyps, which are traditionally treated surgically, may be amenable to endoscopic mucosal resection (EMR), often using a piecemeal method. Appropriate selection of lesions and a careful technique may enhance the efficacy of EMR for polyps >or=20 mm in diameter without compromising safety. The aim of this study was to identify the factors that may be predictive of the risk of polyp recurrence. MATERIAL AND METHODS: A retrospective analysis was conducted on the outcome of 161 polyps >or=20 mm in diameter, treated by piecemeal EMR at a single centre using the "lift and cut" technique. All records were reviewed for polyp size, site, morphology and histology. Polypectomy technique, patient follow-up, polyp recurrence and surgical interventions were also recorded. RESULTS: Over an 8-year period, 161 colonic polyps measuring >or=20 mm were removed by EMR. Follow-up data were available for 149 cases (93%) with a mean polyp diameter of 32.5 mm; the total success rate of endoscopic polyp removal was 95.4%. The number of cases requiring 1, 2, 3, 4 and 6 attempts at EMR was 89 (60%), 36 (24%), 14 (9%), 2 (1.3%) and 1 (0.7%), respectively. Recurrence was significantly related to polyp size (p<0.001). There was no statistically significant relationship between site and recurrence. Seven patients (4.6%) underwent surgical intervention after EMR because of failed clearance. There were no post-EMR perforations and significant bleeding was reported in only two patients (1.7%). CONCLUSIONS: With careful attention to technique, piecemeal EMR is a safe option for the resection of most sessile and flat colorectal polyps >or=20 mm in size. A stricter follow-up may be required for larger lesions because of a higher risk of recurrence.     

Population-based analysis of practices and costs of surveillance for colonic dysplasia in patients with primary sclerosing cholangitis and colitis

BACKGROUND: Patients with primary sclerosing cholangitis (PSC) and colitis are at risk of developing dysplasia and colorectal cancer (CRC). Consequently, annual surveillance colonoscopy with random biopsies is recommended. The aims of the present study were (1) to determine the incidence of dysplasia or CRC, (2) to assess surveillance practices, and (3) to assess the costs associated with surveillance of PSC patients. METHODS: A population-based study was conducted between 2000 and 2004 to identify all patients with a diagnosis of PSC using regional databases. Colonic histopathology reports of PSC patients with colitis were reviewed to determine the frequency of surveillance colonoscopies performed between 2000 and 2005, the number of biopsies retrieved, and the presence of CRC or dysplasia. The cost of annual surveillance colonoscopy with 33 random biopsies to detect 1 additional case of dysplasia was calculated from a local costs database. RESULTS: Forty-five PSC patients with ulcerative colitis or Crohn's disease were identified. Five patients (11.1%) were diagnosed with low-grade dysplasia (n = 2), dysplasia-associated lesion or mass (n = 2), or CRC (n = 1) during the 5-year follow-up period for an incidence rate of 3.1 events per 100 person-years (95% confidence interval: 1.0-7.2/100 person-years). Two of these lesions were detected through surveillance and 3 because of symptomatic presentation. Only 36% (56) of the expected number of surveillance colonoscopies were performed. The median number of biopsies collected was 27 (IQR: 19-33). The cost of surveillance to detect 1 additional case of dysplasia was USD 26,495. CONCLUSION: Despite a high rate of colorectal dysplasia or CRC among PSC patients, surveillance was suboptimal.     

Pleural empyema due to S. typhi: a case report

In a 35 year old immunocompetent male, clinically diagnosed as a case of hydropneumothorax of left side, Salmonella typhi was isolated as the causative agent of pleural empyema.