Comparative analysis of canal transportation and centring ability of three Ni–Ti rotary endodontic systems: Protaper®, MTwo® and Revo-S™, assessed by micro-computed tomography

The aim of this study was to use high-resolution micro-CT to evaluate the effects of three Ni–Ti rotary endodontic instruments, Mtwo^® (VDW, München, Germany), ProTaper^® (Dentsply-Maillefer, Ballaigues, Switzerland) and Revo-S? (MicroMega, Besançon, France), on canal transportation and centring ratio. Fifty-four mesial roots of extracted mandibular molars with an angle of curvature of 25–35° were randomly divided into three groups of eighteen. Each group was instrumented with a previously unused Ni–Ti rotary system. The final instruments used were #30/0.05 taper (Mtwo^®), F3 #30/0.09 apical taper (ProTaper^®) and AS30 #30/0.06 taper (Revo-S?). Teeth were scanned before and after instrumentation using micro-computed tomography with a spatial resolution of 20 μm to measure volume and shaping changes. All images were filtered to improve signal-to-noise ratio. To determine the perimeter of roots and canals exactly, images were segmented in each slice with an edge detection process. Canal transportation and centring ratio were evaluated at 1, 3, 5 and 7 mm from the end of each root. The method developed by Gambill et al. was chosen. ANOVA was conducted with the significance threshold set at p < 0.05. No statistically significant differences were found among the three groups in terms of canal transportation or centring ratio at any level. These systems give similar results with regard to the tested shaping parameters. Under the tested conditions and within the limitations of this study, these systems were able to produce centred preparations of curved canals with minimal transportation.     

Does the acidity of self-etching primers affect bond strength and surface morphology of enamel?

PURPOSE: This study examined the ultrastructure and microtensile bond strengths (TBS) of self-etching (with different acidity) and conventional adhesive systems bonded to unground enamel. MATERIALS AND METHODS: Resin composite (Filtek Z250) buildups were bonded to unground enamel surfaces of third molars after adhesive application with the following materials: Clearfil SE Bond (CSE); Optibond Solo Plus Self-Etch (OP); Tyrian Self Priming Etching (TY), and the controls Scotchbond Multi-Purpose Plus (SBMP) and Single Bond (SB). Six teeth were assigned to each material. After storage in waterfor 24 h at 37 degrees C, the bonded specimens were sectioned into beams of approximately 0.8 mm2 and subsequently subjected to microTBS testing at a crosshead speed of 0.5 mm/min. The average values were subjected to one-way ANOVA (alpha = 0.05). The effect of surface conditioning of each material was observed under scanning electron microscopy (SEM). RESULTS: The highest resin-enamel bond strength was observed for SBMP (22.7 +/- 5.2) and SB (26.7 +/- 5.2 MPa). The lowest mean bond strengths were 10.9 +/- 3.2 and 7.8 +/- 1.5 MPa for TY and OP, respectively. CSE showed an intermediate performance (18.7 +/- 4.6 MPa). An overall increase in porosity was evident along the entire enamel surface treated with the self-etching primers; however, no selective demineralization similar to that with 35% phosphoric acid was observed. CONCLUSION: The highest bond strength means and the more retentive etching pattern were observed for the two-step etch-and-rinse adhesives. Among the self-etching systems studied, Clearfil SE Bond should be preferred.     

Integrity situational judgement test for medical school selection: judging ‘what to do’ versus ‘what not to do’

Context

Despite their widespread use in medical school selection, there remains a lack of clarity on exactly what situational judgement tests (SJTs) measure.

Objectives

We aimed to develop an SJT that measures integrity by combining critical incident interviews (inductive approach) with an innovative deductive approach. The deductive approach guided the development of the SJT according to two established theoretical models, of which one was positively related to integrity (honesty–humility [HH]) and one was negatively related to integrity (cognitive distortions [CD]). The Integrity SJT covered desirable (HH‐based) and undesirable (CD‐based) response options. We examined the convergent and discriminant validity of the Integrity SJT and compared the validity of the HH‐based and CD‐based subscores.

Methods

The Integrity SJT was administered to 402 prospective applicants at a Dutch medical school. The Integrity SJT consisted of 57 scenarios, each followed by four response options, of which two represented HH facets and two represented CD categories. Three SJT scores were computed, including a total, an HH‐based and a CD‐based score. The validity of these scores was examined according to their relationships with external integrity‐related measures (convergent validity) and self‐efficacy (discriminant validity).

Results

The three SJT scores correlated significantly with all integrity‐related measures and not with self‐efficacy, indicating convergent and discriminant validity. In addition, the CD‐based SJT score correlated significantly more strongly than the HH‐based SJT score with two of the four integrity‐related measures.

Conclusions

An SJT that assesses the ability to correctly recognise CD‐based response options as inappropriate (i.e. what one should not do) seems to have stronger convergent validity than an SJT that assesses the ability to correctly recognise HH‐based response options as appropriate (i.e. what one should do). This finding might be explained by the larger consensus on what is considered inappropriate than on what is considered appropriate in a challenging situation. It may be promising to focus an SJT on the ability to recognise what one should not do.     

Local narratives of sexual and other violence against children and young people in Zanzibar

Understandings of violence, and especially sexual violence against children, must be situated within the local context. The 2009 Violence against Children Survey in Zanzibar indicated that 6% of girls and 9% of boys reported having experienced sexual violence before the age of 18 years. This paper reports on an in-depth qualitative study conducted in Zanzibar to provide further insights to these findings by examining the circumstances for sexual and other violence against children in Zanzibar. Twenty-four in-depth interviews with young people and 18 focus-group discussions with young people and adults were conducted in rural and urban Zanzibar. A further 8 interviews were conducted with parents and key stakeholders in government and NGO offices that provide services for children. The findings revealed that religious and cultural practices, which form the foundation of Swahili culture in Zanzibar, provide a moral frame for childhood development, but structural factors make children vulnerable to sexual violence. Both boys and girls are vulnerable to sexual violence in the home, neighbourhood, at school and, in particular, at madrasa or Qur’anic schools. As religion and culture are strong influences on childhood, preventing sexual violence at madrasa schools would strengthen the positive aspects of religious teachings for ensuring a safe childhood.     

Barriers to Effective Drug Treatment for Brain Metastases: A Multifactorial Problem in the Delivery of Precision Medicine

The treatment of metastatic lesions in the brain represents a serious unmet medical need in the field of neuro-oncology. Even though many effective compounds have demonstrated success in treating peripheral (non-CNS) tumors with targeted agents, one aspect of this lack of success in the brain may be related to poor delivery of otherwise effective compounds. Many factors can influence the brain delivery of these agents, but one key barrier is a heterogeneously “leaky” BBB that expresses efflux transporters that limit the BBB permeability for many targeted agents. Future success in therapeutics for brain metastases must take into account the adequate delivery of “active, free drug” to the target, and may include combinations of targeted drugs that are appropriate to address each individual patient’s tumor type. This review discusses some issues that are pertinent to precision medicine for brain metastases, using specific examples of tumor types that have a high incidence of brain metastases.     

In vivo and in vitro methods for evaluating soil arsenic bioavailability: relevant to human health risk assessment

Arsenic (As) is the most frequently occurring contaminant on the priority list of hazardous substances, which lists substances of greatest public health concern to people living at or near U.S. National Priorities List site. Accurate assessment of human health risks from exposure to As-contaminated soils depends on estimating its bioavailability, defined as the fraction of ingested As absorbed across the gastrointestinal barrier and available for systemic distribution and metabolism. Arsenic bioavailability varies among soils and is influenced by site-specific soil physical and chemical characteristics and internal biological factors. This review describes the state-of-the science that supports our understanding of oral bioavailability of soil As, the methods that are currently being explored for estimating soil As relative bioavailability (RBA), and future research areas that could improve our prediction of the oral RBA of soil As in humans. The following topics are addressed: (1) As soil geochemistry; (2) As toxicology; (3) in vivo models for estimating As RBA; (4) in vitro bioaccessibility methods; and (5) conclusions and research needs.