Chemical kinetics of silver diammine fluoride in demineralization and remineralization solutions-an in vitro study

Introduction

Silver Diammine Fluoride (SDF) is a clinical minimal intervention to manage dentin caries. Its chemistry in demineralization conditions has been investigated widely, but far less in remineralization conditions. The aim was to investigate and compare the chemical reactions when SDF is added to remineralization and demineralization solutions.

Methods

0.01 ml SDF (Riva Star) was added to deionized water (DW); demineralization (DS = pH4) and remineralization (RS = pH7.0) solutions. The time sequence of concentrations of NH4+, F-, and Ag+ were measured using ion selective electrodes (ISEs) every 2 min. The pH was also measured. Precipitates were characterized using x-ray Diffraction (XRD) and, 31P and 19F nuclear magnetic resonance spectroscopy (NMR).

Results

The concentrations of NH4+ and Ag+ showed decreasing trends in DW (-0.12 and -0.08 mM/h respectively), and in DS (-1.06 and -0.5 mM/h respectively); with corresponding increase in F- concentration (0.04 and 0.7 mM/h respectively). However, in RS, NH4+ concentration showed little change (0.001 mM/h), and Ag+ and F- concentrations were negligible. XRD results showed that precipitates (in RS only) contained AgCl, and metallic Ag. NMR showed that fluorapatite/carbonated fluorapatite (FAP/CFAP) were formed. The pH increased after SDF addition in all three solutions.

Discussion

SDF dissolved to release NH4+, F- and Ag + . In DW and DS, NH4+ combined with Ag+ to form diamminesilver, causing an increase of F- and pH. In RS, F- reacted with Ca2+ and (PO)43- to form FAP/CFAP, and Ag+ reacted with Cl- to form AgCl/Ag. These suggests why SDF is effective in managing dentin caries.

Characterization of chemical reactions of silver diammine fluoride and hydroxyapatite under remineralization conditions

Introduction

Silver Diammine Fluoride (SDF) is a clinically used topical agent to arrest dental caries. However, the kinetics of its chemical interactions with hydroxyapatite (HA), the principal inorganic component of dental enamel, are not known. The aim was to characterize the step-wise chemical interactions between SDF and HA powder during the clinically important process of remineralization.

Methods

Two grams of HA powder were immersed in 10 ml acetic acid pH = 4.0 for 2 h to mimic carious demineralization. The powder was then washed and dried for 24 h and mixed with 1.5 ml SDF (Riva Star) for 1 min. The treated powder was then air-dried for 3 min, and 0.2 g was removed and stored in individual tubes each containing 10 ml remineralizing solution. Powder was taken from each tube at various times of exposure to remineralization solution (0 min, 10 min, 2 h, 4 h, 8 h, 24 h, and 10 days), and characterized using Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) spectroscopy.

Results and discussion

19F MAS-NMR spectra showed that calcium fluoride (CaF2) started to form almost immediately after HA was in contact with SDF. After 24 h, the peak shifted to -104.5 ppm suggesting that fluoride substituted hydroxyapatite (FSHA) was formed with time at the expense of CaF2. The 31P MAS-NMR spectra showed a single peak at 2.7 ppm at all time points showing that the only phosphate species present was crystalline apatite. The 35Cl MAS-NMR spectra showed formation of silver chloride (AgCl) at 24 h. It was observed that after the scan, the whitish HA powder changed to black color. In conclusion, this time sequence study showed that under remineralization conditions, SDF initially reacted with HA to form CaF2 which is then transformed to FSHA over time. In the presence of chloride, AgCl is formed which is subsequently photo-reduced to black metallic silver.

Living with Dysphagia: A Survey Exploring the Experiences of Adults Living with Neuromuscular Disease and their Caregivers in the United Kingdom

Background

Dysphagia is common in adults living with neuromuscular disease (NMD). Increased life expectancy, secondary to improvements in standards of care, requires the recognition and treatment of dysphagia with an increased priority. Evidence to support the establishment of healthcare pathways is, however, lacking. The experiences of people living with NMD (pplwNMD) and their caregivers are valuable to guide targeted, value-based healthcare.

Objective

To generate preliminary considerations for neuromuscular dysphagia care and future research in the United Kingdom, based on the experiences of those living with, or caring for, people with NMD.

Methods

Two surveys (one for adults living with NMD and dysphagia, and a second for caregivers) were co-designed with an advisory group of people living with NMD. Surveys were electronically distributed to adults living with NMD and their caregivers between 18th May and 26th July 2020. Distribution was through UK disease registries, charity websites, newsletters, and social media.

Results

Adults living with NMD receive little information or education that they are likely to develop swallowing difficulties. Most respondents report wanting this information prior to developing these difficulties. Difficulties with swallowing food and medication are common in this group, and instrumental assessment is considered a helpful assessment tool. Both adults living with NMD and caregivers want earlier access to neuromuscular swallowing specialists and training in how best to manage their difficulties.

Conclusions

Improvement is needed in the dysphagia healthcare pathway for adults living with NMD to help mitigate any profound physical and psychological consequences that may be caused by dysphagia. Education about swallowing difficulties and early referral to a neuromuscular swallowing specialist are important to pplwNMD and their caregivers. Further research is required to better understand the experiences of pplwNMD and their caregivers to inform the development of dysphagia healthcare pathways.

Epichloë fungal endophyte interactions in perennial ryegrass (Lolium perenne L.) modified to accumulate foliar lipids for increased energy density

BACKGROUND

Commercial cultivars of perennial ryegrass infected with selected Epichloë fungal endophytes are highly desirable in certain pastures as the resulting mutualistic association has the capacity to confer agronomic benefits (such as invertebrate pest deterrence) largely due to fungal produced secondary metabolites (e.g., alkaloids). In this study, we investigated T2 segregating populations derived from two independent transformation events expressing diacylglycerol acyltransferase (DGAT) and cysteine oleosin (CO) genes designed to increase foliar lipid and biomass accumulation. These populations were either infected with Epichloë festucae var. lolii strain AR1 or Epichloë sp. LpTG-3 strain AR37 to examine relationships between the introduced trait and the endophytic association. Here we report on experiments designed to investigate if expression of the DGAT + CO trait in foliar tissues of perennial ryegrass could negatively impact the grass-endophyte association and vice versa. Both endophyte and plant characters were measured under controlled environment and field conditions.

RESULTS

Expected relative increases in total fatty acids of 17-58% accrued as a result of DGAT + CO expression with no significant difference between the endophyte-infected and non-infected progeny. Hyphal growth in association with DGAT + CO expression appeared normal when compared to control plants in a growth chamber. There was no significant difference in mycelial biomass for both strains AR1 and AR37, however, Epichloë-derived alkaloid concentrations were significantly lower on some occasions in the DGAT + CO plants compared to the corresponding null-segregant progenies, although these remained within the reported range for bioactivity.

CONCLUSIONS

These results suggest that the mutualistic association formed between perennial ryegrass and selected Epichloë strains does not influence expression of the host DGAT + CO technology, but that endophyte performance may be reduced under some circumstances. Further investigation will now be required to determine the preferred genetic backgrounds for introgression of the DGAT + CO trait in combination with selected endophyte strains, as grass host genetics is a major determinant to the success of the grass-endophyte association in this species.

Development and calibration of a high dynamic range and autonomous ocean-light instrument to measure sub-surface profiles in ice-covered waters

The optical chain and logger (OptiCAL) is an autonomous ice-tethered observatory equipped with multiple light sensors for mapping the variation of light with depth. We describe the instrument and present an ensemble calibration for downwelling irradiance E P A R in [µm o l m -2 s -1]. Results from a long-term deployment in the Arctic Ocean demonstrate that the OptiCAL can cover the high dynamic range of under-ice light levels from July to November and produce realistic values in terms of magnitude when compared to modeled surface irradiance. Transient features of raised light levels at specific depths associated with nearby leads in the ice underline the importance of depth-resolved light measurements.

Influence of Mechanical Alignment on Functional Knee Phenotypes and Clinical Outcomes in Primary TKA: A 1-Year Prospective Analysis

In total knee arthroplasty (TKA), functional knee phenotypes are of interest regarding surgical alignment strategies. Functional knee phenotypes were introduced in 2019 and consist of limb, femoral, and tibial phenotypes. The hypothesis of this study was that mechanically aligned (MA) TKA changes preoperative functional phenotypes, which decreases the 1-year Forgotten Joint (FJS) and Oxford Knee Score (OKS) and increases the 1-year WOMAC. All patients included in this study had end-stage osteoarthritis and were treated with a primary MA TKA, which was supervised by four academic knee arthroplasty specialists. To determine the limb, femoral, and tibial phenotype, a long-leg radiograph (LLR) was imaged preoperatively and two to three days after TKA. FJS, OKS, and WOMAC were obtained 1 year after TKA. Patients were categorized using the change in functional limb, femoral, and tibial phenotype measured on LLR, and the scores were compared between the different categories. A complete dataset of preoperative and postoperative scores and radiographic images could be obtained for 59 patients. 42% of these patients had a change of limb phenotype, 41% a change of femoral phenotype, and 24% a change of tibial phenotype of more than ±1 relative to the preoperative phenotype. Patients with more than ±1 change of limb phenotype had significantly lower median FJS (27 points) and OKS (31 points) and higher WOMAC scores (30 points) relative to the 59-, 41-, and 4-point scores of those with a 0 ± 1 change (p < 0.0001 to 0.0048). Patients with a more than ±1 change of femoral phenotype had significantly lower median FJS (28 points) and OKS (32 points) and higher WOMAC scores (24 points) relative to the 69-, 40-, and 8-point scores of those with a 0 ± 1 change (p < 0.0001). A change in tibial phenotype had no effect on the FJS, OKS, and WOMAC scores. Surgeons performing MA TKA could consider limiting coronal alignment corrections of the limb and femoral joint line to within one phenotype to reduce the risk of low patient-reported satisfaction and function at 1-year.

Insight into the regulatory networks underlying the high lipid perennial ryegrass growth under different irradiances

Under favourable conditions, perennial ryegrass (Lolium perenne) engineered to accumulated high lipid (HL) carbon sink in their leaves was previously shown to also enhance photosynthesis and growth. The greater aboveground biomass was found to be diminished in a dense canopy compared to spaced pots. Besides, the underlying genetic regulatory network linking between leaf lipid sinks and these physiological changes remains unknown. In this study, we demonstrated that the growth advantage was not displayed in HL Lolium grown in spaced pots under low lights. Under standard lights, analysis of differentiating transcripts in HL Lolium reveals that the plants had elevated transcripts involved in lipid metabolism, light capturing, photosynthesis, and sugar signalling while reduced expression of genes participating in sugar biosynthesis and transportation. The plants also had altered several transcripts involved in mitochondrial oxidative respiration and redox potential. Many of the above upregulated or downregulated transcript levels were found to be complemented by growing the plants under low light. Overall, this study emphasizes the importance of carbon and energy homeostatic regulatory mechanisms to overall productivity of the HL Lolium through photosynthesis, most of which are significantly impacted by low irradiances.

Realist analysis of whether emergency departments with primary care services generate 'provider-induced demand'

Background

It is not known whether emergency departments (EDs) with primary care services influence demand for non-urgent care (‘provider-induced demand’). We proposed that distinct primary care services in EDs encourages primary care demand, whereas primary care integrated within EDs may be less likely to cause additional demand. We aimed to explore this and explain contexts (C), mechanisms (M) and outcomes (O) influencing demand.

Methods

We used realist evaluation methodology and observed ED service delivery. Twenty-four patients and 106 staff members (including Clinical Directors and General Practitioners) were interviewed at 13 EDs in England and Wales (240 hours of observations across 30 days). Field notes from observations and interviews were analysed by creating ‘CMO’ configurations to develop and refine theories relating to drivers of demand.

Results

EDs with distinct primary care services were perceived to attract demand for primary care because services were visible, known or enabled direct access to health care services. Other influencing factors included patients’ experiences of accessing primary care, community care capacity, service design and population characteristics.

Conclusions

Patient, local-system and wider-system factors can contribute to additional demand at EDs that include primary care services. Our findings can inform service providers and policymakers in developing strategies to limit the effect of potential influences on additional demand when demand exceeds capacity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12873-022-00709-2.

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

Mental health, welfare or justice: An introductory global overview of differences between countries in the scale and approach to secure placements of children and young people

BACKGROUND

Estimates suggest that over a million children per year are deprived of their liberty across the world. Little is known about the types, ethos or distribution of secure beds in which they are detained.

AIM

This study aims to provide quantitative data with background information, to explore similarities and differences across jurisdictions, and to inform critical inquiry into key concepts and practices.

METHODS

Data was obtained using an opportunistic sample of affluent countries, derived from an emerging academic/practice network of senior professionals. Depending on jurisdiction, data was already in the public domain or specifically requested. Data requests were related to the nature and size of health, welfare and criminal justice elements of secure beds and recent occupancy. Key professionals working in child secure settings, within jurisdictions, provided commentary on local approaches.

RESULTS

Data was incomplete but allowed for comparisons between 10 jurisdictions. The proportions of the populations of children and young people detained varied by jurisdiction as did their distribution across variations of secure settings. Not all jurisdictions had all three kinds of secure settings. Definitions of secure beds varied depending on the use of relational, procedural or physical security.

CONCLUSION

Findings are tentative but suggestion solely considering numerical descriptions of children's detention is misleading; our study highlights ways in which comparative studies may be improved. Within reported jurisdictions, the framework of health, welfare and justice was meaningful but this may not hold true with a wider international application of this method. Open interrogation of this data would be enhanced by the inclusion of children's perspectives.

Changes in Leaf-Level Nitrogen Partitioning and Mesophyll Conductance Deliver Increased Photosynthesis for Lolium perenne Leaves Engineered to Accumulate Lipid Carbon Sinks

Diacylglycerol acyl-transferase (DGAT) and cysteine oleosin (CO) expression confers a novel carbon sink (of encapsulated lipid droplets) in leaves of Lolium perenne and has been shown to increase photosynthesis and biomass. However, the physiological mechanism by which DGAT + CO increases photosynthesis remains unresolved. To evaluate the relationship between sink strength and photosynthesis, we examined fatty acids (FA), water-soluble carbohydrates (WSC), gas exchange parameters and leaf nitrogen for multiple DGAT + CO lines varying in transgene accumulation. To identify the physiological traits which deliver increased photosynthesis, we assessed two important determinants of photosynthetic efficiency, CO₂ conductance from atmosphere to chloroplast, and nitrogen partitioning between different photosynthetic and non-photosynthetic pools. We found that DGAT + CO accumulation increased FA at the expense of WSC in leaves of L. perenne and for those lines with a significant reduction in WSC, we also observed an increase in photosynthesis and photosynthetic nitrogen use efficiency. DGAT + CO L. perenne displayed no change in rubisco content or V_cmax but did exhibit a significant increase in specific leaf area (SLA), stomatal and mesophyll conductance, and leaf nitrogen allocated to photosynthetic electron transport. Collectively, we showed that increased carbon demand via DGAT+CO lipid sink accumulation can induce leaf-level changes in L. perenne which deliver increased rates of photosynthesis and growth. Carbon sinks engineered within photosynthetic cells provide a promising new strategy for increasing photosynthesis and crop productivity.

Real-world challenges for patients with breast cancer in sub-Saharan Africa: a retrospective observational study of access to care in Ghana, Kenya and Nigeria

OBJECTIVE

To evaluate medical resource utilisation and timeliness of access to specific aspects of a standard care pathway for breast cancer at tertiary centres in sub-Saharan Africa.

DESIGN

Data were retrospectively abstracted from records of patients with breast cancer treated within a prespecified 2-year period between 2014 and 2017. The study protocol was approved by local institutional review boards.

SETTING

Six tertiary care institutions in Ghana, Kenya and Nigeria were included.

PARTICIPANTS

Health records of 862 patients with breast cancer were analysed: 299 in Ghana; 314 in Kenya; and 249 in Nigeria.

INTERVENTIONS

As directed by the treating physician.

OUTCOME MEASURES

Parameters selected for evaluation included healthcare resource and use, medical procedure turnaround times and out-of-pocket (OOP) payment patterns.

RESULTS

Use of mammography or breast ultrasonography was <45% in all three countries. Across the three countries, 78%-88% of patients completed tests for hormone receptors and human epidermal growth factor receptor 2 (HER2). Most patients underwent mastectomy (64%-67%) or breast-conserving surgery (15%-26%). Turnaround times for key procedures, such as pathology, surgery and systemic therapy, ranged from 1 to 5 months. In Ghana and Nigeria, most patients (87%-93%) paid for diagnostic tests entirely OOP versus 30%-32% in Kenya. Similarly, proportions of patients paying OOP only for treatments were high: 45%-79% in Ghana, 8%-20% in Kenya and 72%-89% in Nigeria. Among patients receiving HER2-targeted therapy, the average number of cycles was five for those paying OOP only versus 14 for those with some insurance coverage.

CONCLUSIONS

Patients with breast cancer treated in tertiary facilities in sub-Saharan Africa lack access to timely diagnosis and modern systemic therapies. Most patients in Ghana and Nigeria bore the full cost of their healthcare and were more likely to be employed and have secondary or postsecondary education. Access to screening/diagnosis and appropriate care is likely to be substantively lower for the general population.

An Exploratory Study of the Texture Research Investigational Platform (TRIP) to Evaluate Bone Texture Score of Distal Femur DXA Scans - A TBS-Based Approach

Poor bone status is associated with increased complications following orthopedic surgery. Therefore, assessing site-specific skeletal status prior to or after orthopedic surgery to optimize outcomes is appealing. The trabecular bone score (TBS) approach, a surrogate for microarchitecture, was adapted to the Texture Research Investigational Platform (TRIP), which allows assessment of many skeletal sites imaged by various modalities. TRIP generates a bone texture score (TBS ORTHO), which could potentially guide surgical decision-making and offer insight into postsurgical fracture risk. As distal femur bone loss occurs following total knee arthroplasty (TKA), we hypothesized that TBS ORTHO after TKA would identify poorer texture in the operated femur compared to the nonoperated. We evaluated 30 subjects (15 M/15 F) with unilateral TKA 2-5 yr previously, mean age 67.9 yr and body mass index 30 kg/m². Using a Lunar iDXA, lumbar spine and entire femur scans were obtained, the latter using the atypical femur fracture feature. Distal femur bone mineral density (BMD) and TBS ORTHO were obtained using manual regions of interest (ROI) at 15% and 25% of leg length from the intercondylar notch. TBS ORTHO was determined using distal femur DICOM images and TRIP v1.0 (Medimaps, France). Differences in operated vs nonoperated femur were evaluated by paired t test. As previously reported, operated leg BMD was approx 10% lower at 15% and 25% ROIs. Similarly, TBS ORTHO values in the operated leg were approx 5% lower (p < 0.05) at these same ROIs. Distal femur TBS ORTHO and BMD were largely unrelated. TBS ORTHO reproducibility at these ROIs was approx 3.5%. In conclusion, this pilot study documents the feasibility of reproducibly obtaining distal femur TBS ORTHO values. Lower values were observed in the surgical leg, consistent with the bone loss that follows TKA. Further work is indicated to refine TRIP use and evaluate whether such data provides guidance for surgical decision-making and improves periprosthetic fracture prediction.

Development of a Clinical Prediction Model for In-hospital Mortality from the South African Cohort of the African Surgical Outcomes Study

BACKGROUND

Data on the factors that influence mortality after surgery in South Africa are scarce, and neither these data nor data on risk-adjusted in-hospital mortality after surgery are routinely collected. Predictors related to the context or setting of surgical care delivery may also provide insight into variation in practice. Variation must be addressed when planning for improvement of risk-adjusted outcomes. Our objective was to identify the factors predicting in-hospital mortality after surgery in South Africa from available data.

METHODS

A multivariable logistic regression model was developed to identify predictors of 30-day in-hospital mortality in surgical patients in South Africa. Data from the South African contribution to the African Surgical Outcomes Study were used and included 3800 cases from 51 hospitals. A forward stepwise regression technique was then employed to select for possible predictors prior to model specification. Model performance was evaluated by assessing calibration and discrimination. The South African Surgical Outcomes Study cohort was used to validate the model.

RESULTS

Variables found to predict 30-day in-hospital mortality were age, American Society of Anesthesiologists Physical Status category, urgent or emergent surgery, major surgery, and gastrointestinal-, head and neck-, thoracic- and neurosurgery. The area under the receiver operating curve or c-statistic was 0.859 (95% confidence interval: 0.827-0.892) for the full model. Calibration, as assessed using a calibration plot, was acceptable. Performance was similar in the validation cohort as compared to the derivation cohort.

CONCLUSION

The prediction model did not include factors that can explain how the context of care influences post-operative mortality in South Africa. It does, however, provide a basis for reporting risk-adjusted perioperative mortality rate in the future, and identifies the types of surgery to be prioritised in quality improvement projects at a local or national level.

The logistical management of tertiary urethral disease in the United Kingdom: Implications from an online audit of male reconstructive urethral surgery

Objective:

To determine those patient groupings, based on volume and risk, whose optimal urethral reconstructive management might be provided by a reorganisation of UK reconstructive surgeons.

Methods:

Between 2010 and 2017, ~689 men/year were enrolled onto an online audit platform collecting data about urethral reconstruction in the UK; this accrual was compared against hospital episode statistics (HES). The available workforce, and where this was based, was collected. Individual and institutional incumbent patient volumes, pathology, surgical complexity and outcomes from treatment were collated to stratify volume/risk groups.

Results:

More than 90% of all HES-recorded data were accrued, being provided by 50 surgeons at 39 operative sites. Most reconstructive surgery was provided at 10 centres performing >20 procedures/year. More than 50% of all interventions were of a high-volume low-risk type. Of activity, 32.3% was intermediate volume or moderate risk, and 12.5% of men presented for lower-volume or higher-risk procedures.

Conclusion:

Correlation of detailed volume/outcome data allows the definition of patient populations presenting for urethral reconstruction. Stratification of each group’s management, to optimise the surgical outcome, may be applied to a hierarchical service delivery model based on the complexity of the patient’s presenting urethral pathology.

Level of evidence:

Level IV