CMRsim-A python package for cardiovascular MR simulations incorporating complex motion and flow

PURPOSE

To present an open-source MR simulation framework that facilitates the incorporation of complex motion and flow for studying cardiovascular MR (CMR) acquisition and reconstruction.

METHODS

CMRsim is a Python package that allows simulation of CMR images using dynamic digital phantoms with complex motion as input. Two simulation paradigms are available, namely, numerical and analytical solutions to the Bloch equations, using a common motion representation. Competitive simulation speeds are achieved using TensorFlow for GPU acceleration. To demonstrate the capability of the package, one introductory and two advanced CMR simulation experiments are presented. The latter showcase phase-contrast imaging of turbulent flow downstream of a stenotic section and cardiac diffusion tensor imaging on a contracting left ventricle. Additionally, extensive documentation and example resources are provided.

RESULTS

The Bloch simulation with turbulent flow using approximately 1.5 million particles and a sequence duration of 710 ms for each of the seven different velocity encodings took a total of 29 min on a NVIDIA Titan RTX GPU. The results show characteristic phase contrast and magnitude modulation present in real data. The analytical simulation of cardiac diffusion tensor imaging with bulk-motion phase sensitivity took approximately 10 s per diffusion-weighted image, including preparation and loading steps. The results exhibit the expected alteration of diffusion metrics due to strain.

CONCLUSION

CMRsim is the first simulation framework that allows one to feasibly incorporate complex motion, including turbulent flow, to systematically study advanced CMR acquisition and reconstruction approaches. The open-source package features modularity and transparency, facilitating maintainability and extensibility in support of reproducible research.

Self-gated cine phase-contrast balanced SSFP flow quantification at 0.55 T

PURPOSE

To implement cine phase-contrast balanced SSFP (PC-bSSFP) for low-field 0.55T cardiac MRI by exploiting the intrinsic flow sensitivity of the bSSFP slice-select gradient and the in-plane phase-cancelation properties of radial trajectories, enabling self-gated and referenceless PC-bSSFP flow quantification at 0.55 T.

METHODS

A free-running, tiny golden-angle radial PC-bSSFP approach was implemented on 0.55T and 1.5T systems. Cardiac and respiratory self-gating was incorporated to enable electrocardiogram-free scanning during breath-hold and free-breathing. By exploiting the intrinsic in-plane phase-cancelation properties of radial acquisitions and background phase fitting, referenceless single-point PC-bSSFP was realized. In vivo data were acquired in the ascending aorta of healthy subjects at 0.55 T and 1.5 T during breath-hold and free-breathing. Flow data, SNR, and velocity-to-noise ratio were compared relative to data obtained with phase-contrast spoiled gradient-echo variants.

RESULTS

Velocities acquired with PC-bSSFP compared well with data from phase-contrast spoiled gradient-echo (RMSEv  = 5.8 cm/s). PC-bSSFP at 0.55 T resulted in high-quality cine magnitude images and phase maps with sufficient SNR and velocity-to-noise ratio. Breath-hold and free-breathing PC-bSSFP performed very similarly, with comparable flow quantification (RMSEv  = 5.7 cm/s). Referenceless single-point PC-bSSFP results agreed well with two-point PC-bSSFP (-1.8 ± 5.2 cm/s) while reducing scan times 2-fold.

CONCLUSION

PC-bSSFP is feasible on low-field 0.55T systems, producing high-quality cine images while permitting simultaneous aortic flow measurements during breath-hold and free-breathing and without the need for electrocardiogram gating.

Pacemaker-lead-associated thrombosis in dogs: a multicenter retrospective study

INTRODUCTION

Pacemaker implantation is the treatment of choice for clinically relevant bradyarrhythmias. Pacemaker-lead-associated thrombosis (PLAT) occurs in 23.0-45.0% of people with permanent transvenous pacemakers. Serious thromboembolic complications are reported in 0.6-3.5%. The incidence of PLAT in dogs is unknown.

ANIMALS, MATERIALS AND METHODS

multicenter retrospective study of seven centers with 606 client-owned dogs undergoing permanent pacemaker implantation between 2012 and 2019. 260 dogs with a transvenous pacemaker with echocardiographic follow-up, 268 dogs with a transvenous pacemaker without echocardiographic follow-up and 78 dogs with an epicardial pacemaker.

RESULTS

10.4% (27/260) of dogs with transvenous pacemakers and echocardiographic follow-up had PLAT identified. The median time to diagnosis was 175 days (6-1853 days). Pacemaker-lead-associated thrombosis was an incidental finding in 15/27 (55.6%) dogs. Of dogs with a urine protein:creatinine ratio measured at pacemaker implantation, dogs with PLAT were more likely to have proteinuria at pacemaker implantation vs. dogs without PLAT (6/6 (100.0%) vs. 21/52 (40.4%), P=0.007). Urine protein:creatinine ratio was measured in 12/27 (44.4%) dogs at PLAT diagnosis, with proteinuria identified in 10/12 (83.3%) dogs. Anti-thrombotic drugs were used following the identification of PLAT in 22/27 (81.5%) dogs. The thrombus resolved in 9/15 (60.0%) dogs in which follow-up echocardiography was performed. Dogs with PLAT had shorter survival times from implantation compared to those without PLAT (677 days [9-1988 days] vs. 1105 days [1-2661 days], P=0.003).

CONCLUSIONS

Pacemaker-lead-associated thrombosis is identified in 10.4% (27/260) of dogs following transvenous pacing, is associated with proteinuria, can cause significant morbidity, and is associated with reduced survival times.

Ramping down a clinical 3 T scanner: a journey into MRI and MRS at 0.75 T

OBJECT

Lower-field MR is reemerging as a viable, potentially cost-effective alternative to high-field MR, thanks to advances in hardware, sequence design, and reconstruction over the past decades. Evaluation of lower field strengths, however, is limited by the availability of lower-field systems on the market and their considerable procurement costs. In this work, we demonstrate a low-cost, temporary alternative to purchasing a dedicated lower-field MR system.

MATERIALS AND METHODS

By ramping down an existing clinical 3 T MRI system to 0.75 T, proton signals can be acquired using repurposed ¹³C transmit/receive hardware and the multi-nuclei spectrometer interface. We describe the ramp-down procedure and necessary software and hardware changes to the system.

RESULTS

Apart from presenting system characterization results, we show in vivo examples of cardiac cine imaging, abdominal two- and three-point Dixon-type water/fat separation, water/fat-separated MR Fingerprinting, and point-resolved spectroscopy. In addition, the ramp-down approach allows unique comparisons of, e.g., gradient fidelity of the same MR system operated at different field strengths using the same receive chain, gradient coils, and amplifiers.

DISCUSSION

Ramping down an existing MR system may be seen as a viable alternative for lower-field MR research in groups that already own multi-nuclei hardware and can also serve as a testing platform for custom-made multi-nuclei transmit/receive coils.

Incisional hernia following colorectal cancer surgery according to suture technique: Hughes Abdominal Repair Randomized Trial (HART)

BACKGROUND

Incisional hernias cause morbidity and may require further surgery. HART (Hughes Abdominal Repair Trial) assessed the effect of an alternative suture method on the incidence of incisional hernia following colorectal cancer surgery.

METHODS

A pragmatic multicentre single-blind RCT allocated patients undergoing midline incision for colorectal cancer to either Hughes closure (double far-near-near-far sutures of 1 nylon suture at 2-cm intervals along the fascia combined with conventional mass closure) or the surgeon's standard closure. The primary outcome was the incidence of incisional hernia at 1 year assessed by clinical examination. An intention-to-treat analysis was performed.

RESULTS

Between August 2014 and February 2018, 802 patients were randomized to either Hughes closure (401) or the standard mass closure group (401). At 1 year after surgery, 672 patients (83.7 per cent) were included in the primary outcome analysis; 50 of 339 patients (14.8 per cent) in the Hughes group and 57 of 333 (17.1 per cent) in the standard closure group had incisional hernia (OR 0.84, 95 per cent c.i. 0.55 to 1.27; P = 0.402). At 2 years, 78 patients (28.7 per cent) in the Hughes repair group and 84 (31.8 per cent) in the standard closure group had incisional hernia (OR 0.86, 0.59 to 1.25; P = 0.429). Adverse events were similar in the two groups, apart from the rate of surgical-site infection, which was higher in the Hughes group (13.2 versus 7.7 per cent; OR 1.82, 1.14 to 2.91; P = 0.011).

CONCLUSION

The incidence of incisional hernia after colorectal cancer surgery is high. There was no statistical difference in incidence between Hughes closure and mass closure at 1 or 2 years.

REGISTRATION NUMBER

ISRCTN25616490 (http://www.controlled-trials.com).

Exercise to Mend Aged-tissue Crosstalk in Bone Targeting Osteoporosis & Osteoarthritis

Aging induces alterations in bone structure and strength through a multitude of processes, exacerbating common aging- related diseases like osteoporosis and osteoarthritis. Cellular hallmarks of aging are examined, as related to bone and the marrow microenvironment, and ways in which these might contribute to a variety of age-related perturbations in osteoblasts, osteocytes, marrow adipocytes, chondrocytes, osteoclasts, and their respective progenitors. Cellular senescence, stem cell exhaustion, mitochondrial dysfunction, epigenetic and intracellular communication changes are central pathways and recognized as associated and potentially causal in aging. We focus on these in musculoskeletal system and highlight knowledge gaps in the literature regarding cellular and tissue crosstalk in bone, cartilage, and the bone marrow niche. While senolytics have been utilized to target aging pathways, here we propose non-pharmacologic, exercise-based interventions as prospective "senolytics" against aging effects on the skeleton. Increased bone mass and delayed onset or progression of osteoporosis and osteoarthritis are some of the recognized benefits of regular exercise across the lifespan. Further investigation is needed to delineate how cellular indicators of aging manifest in bone and the marrow niche and how altered cellular and tissue crosstalk impact disease progression, as well as consideration of exercise as a therapeutic modality, as a means to enhance discovery of bone-targeted therapies.

Consensus Statement on Future Directions for the Behavioral and Social Sciences in Oral Health

The behavioral and social sciences are central to understanding and addressing oral and craniofacial health, diseases, and conditions. With both basic and applied approaches, behavioral and social sciences are relevant to every discipline in dentistry and all dental, oral, and craniofacial sciences, as well as oral health promotion programs and health care delivery. Key to understanding multilevel, interacting influences on oral health behavior and outcomes, the behavioral and social sciences focus on individuals, families, groups, cultures, systems, societies, regions, and nations. Uniquely positioned to highlight the importance of racial, cultural, and other equity in oral health, the behavioral and social sciences necessitate a focus on both individuals and groups, societal reactions to them related to power, and environmental and other contextual factors. Presented here is a consensus statement that was produced through an iterative feedback process. The statement reflects the current state of knowledge in the behavioral and social oral health sciences and identifies future directions for the field, focusing on 4 key areas: behavioral and social theories and mechanisms related to oral health, use of multiple and novel methodologies in social and behavioral research and practice related to oral health, development and testing of behavioral and social interventions to promote oral health, and dissemination and implementation research for oral health. This statement was endorsed by over 400 individuals and groups from around the world and representing numerous disciplines in oral health and the behavioral and social sciences. Having reached consensus, action is needed to advance and further integrate and translate behavioral and social sciences into oral health research, oral health promotion and health care, and the training of those working to ensure oral health for all.

Fundamentals of turbulent flow spectrum imaging

PURPOSE

To introduce a mathematical framework and in-silico validation of turbulent flow spectrum imaging (TFSI) of stenotic flow using phase-contrast MRI, evaluate systematic errors in quantitative turbulence parameter estimation, and propose a novel method for probing the Lagrangian velocity spectra of turbulent flows.

THEORY AND METHODS

The spectral response of velocity-encoding gradients is derived theoretically and linked to turbulence parameter estimation including the velocity autocorrelation function spectrum. Using a phase-contrast MRI simulation framework, the encoding properties of bipolar gradient waveforms with identical first gradient moments but different duration are investigated on turbulent flow data of defined characteristics as derived from computational fluid dynamics. Based on theoretical insights, an approach using velocity-compensated gradient waveforms is proposed to specifically probe desired ranges of the velocity autocorrelation function spectrum with increased accuracy.

RESULTS

Practical velocity-encoding gradients exhibit limited encoding power of typical turbulent flow spectra, resulting in up to 50% systematic underestimation of intravoxel SD values. Depending on the turbulence level in fluids, the error due to a single encoding gradient spectral response can vary by 20%. When using tailored velocity-compensated gradients, improved quantification of the Lagrangian velocity spectrum on a voxel-by-voxel basis is achieved and used for quantitative correction of intravoxel SD values estimated with velocity-encoding gradients.

CONCLUSION

To address systematic underestimation of turbulence parameters using bipolar velocity-encoding gradients in phase-contrast MRI of stenotic flows with short correlation times, tailored velocity-compensated gradients are proposed to improve quantitative mapping of turbulent blood flow characteristics.

A Pre-implementation Study of Volumetric Modulated Arc Therapy for Same-day Planning and Treatment of Vertebral Bone Metastases Within a Rapid-access Palliative Radiotherapy Programme

AIMS

We aimed to develop a process for same-day contouring, planning, quality assurance and delivery of volumetric modulated arc therapy (VMAT) for vertebral bone metastases within our institution's rapid-access palliative radiotherapy programme.

MATERIALS AND METHODS

Two thoracic (T6-7, T3-7) and two lumbar (L2-3, L1-5) targets were contoured on computed tomography images acquired from an anthropomorphic phantom and five patient scans. Inverse planning aimed to provide coverage of a prescribed dose of 8 Gy with a combined lung V2Gy < 25% and a combined kidney mean dose <2 Gy. Serial plans were created to identify an efficient combination of six main planning variables specific to our treatment planning system: (i) voxel size (3 mm versus 5 mm), (ii) Monte Carlo statistical uncertainty (1% per calculation versus 3% per control point), (iii) fluence smoothing (medium versus high), (iv) number of iterations of segment shape changes during optimisation (1 versus 5), (v) dose calculation algorithm (Monte Carlo versus pencil beam) and (vi) number of arcs (single versus multiple). Contouring, planning, quality assurance and treatment delivery were timed.

RESULTS

The combination of planning variables deemed efficient and appropriate was: a 3 mm voxel size, statistical uncertainty of 1% per calculation, medium fluence smoothing, five iterations of segment shape changes, Monte Carlo dose calculation and single full arc delivery. Patient scan contouring times ranged from 7 to 9 min (T6-7), 11-13 min (T3-7), 5-7 min (L2-3) and 8-10 min (L1-5) and planning times ranged from 9 to 15 min (T6-7), 13-25 min (T3-7), 18-25 min (L2-3) and 21-31 min (L1-5). Physics quality assurance times ranged from 15 to 21 min and beam-on times ranged from 3 to 6 min.

CONCLUSIONS

The combined elements of VMAT for thoracic and lumbar vertebral bone metastases were completed in under 2 h. This new process makes same-day contouring, planning, quality assurance and treatment delivery of VMAT feasible within our rapid-access palliative radiotherapy programme.

Behavioral Sciences in the Promotion of Oral Health

The importance and value of behavioral sciences in dentistry have long been recognized, and their contribution to dental education, research, clinical practice, and oral health policy has been significant over the past half century. Over time behavioral sciences have expanded our understanding of oral health beyond "disease" to a broader biopsychosocial concept of oral health. This in turn has led dentistry away from a focus of "treatment" to oral health "care," notably in the new millennium. Key oral health behaviors have been identified for more than half a century: the importance of diet, oral hygiene, dental services, and other factors. Various behavioral models and theories have been proposed, particularly since the 1970s, providing useful frameworks with sound psychological basis to help understand the paths of oral health behaviors. These models draw on theories of self-efficacy, motivation, counseling, and "behavior change." Since the 1980s, there has been a greater understanding that these behaviors often share a common pathway with the etiology of other diseases (common risk factors). Furthermore, the relationship between individual factors and the broader environmental factors has been increasingly emphasized since the 1990s, leading to a united call for action in addressing oral health inequalities. Within the past decade, there are useful examples of models, frameworks, and techniques of behavior change with respect to oral health, involving planning, prompting, encouraging, goal setting, and/or motivating. In particular, there is a growing interest and use of motivational interviewing. Likewise, behavioral therapies, such as cognitive behavioral therapy, are increasingly being employed in dental practice in the management of dental anxiety, pain, and psychosomatic dental and oral problems, with promising results. Recommendations are outlined for future directions for behavioral sciences in the promotion of oral health.

Time to Diagnosis and Treatment with Palliative Radiotherapy among Inuit Patients with Cancer from the Arctic Territory of Nunavut, Canada

AIMS

The cancer burden among Circumpolar Inuit is high. Palliative radiotherapy is a mainstay treatment for controlling symptoms of advanced cancers, but Inuit are required to travel far distances to access this service. Access to palliative radiotherapy and time away from home communities have not been explored among this population. We sought to describe the time intervals from symptom onset to the start of palliative radiotherapy among Canadian Inuit patients treated at The Ottawa Hospital (TOH).

MATERIALS AND METHODS

A retrospective review of Inuit patients from Nunavut treated with radiotherapy between 2005 and 2014 at TOH.

RESULTS

Of a total of 152 radiotherapy patients, 88 (58%) were treated palliatively. Of these, 61 (70%) had stage IV disease at diagnosis and 63 (72%) had lung cancer. The median time from referral for specialist care to the patient's first flight to Ottawa was 4 days (range 0-97). The median length of treatment was 7 days (range 0-27), but patients spent a median of 64.5 days (range 14-633) in Ottawa. The median survival from the date of pathological diagnosis was 5.2 months.

CONCLUSIONS

Most Inuit radiotherapy patients at TOH were treated palliatively. Patients were brought from Nunavut relatively quickly for specialist care, which is encouraging. However, patients spent over 2 months away from home, in the context of a median survival of less than 6 months. Opportunities for improvement include both provider and system-level changes, which may be applicable to other Circumpolar Inuit regions across Europe and North America.

Efficacy of caries and gingivitis prevention strategies among children and adolescents with intellectual disabilities: a systematic review and meta-analysis

BACKGROUND

Dental caries and periodontal diseases are the most common oral diseases among human beings. Individuals with intellectual disabilities (IDs) have poor oral health and limited access to dental care. The aim of this study was to investigate the efficacy of strategies in caries and gingivitis prevention among children and adolescents with ID.

METHODS

Four electronic databases (PubMed, Cochrane Library, Web of Science and Scopus) were searched from their commencement date to 17 April 2017. Randomised or non-randomised controlled trials evaluating the efficacy of interventions in caries and gingivitis prevention were included if the participants were children and adolescents with ID. Gingival index and caries experiences were reported in the format of mean difference and standard error. Meta-analysis was conducted if data could be pooled from two or more studies using similar outcome measurements and intervention.

RESULTS

A total of 1455 articles published in English were identified. Fourteen studies formed the basis of qualitative analysis; six studies were feasible to perform quantitative analysis. Meta-analysis favoured fluoride to placebo in caries prevention [Z = 2.02, P < 0.05, 95% CI: -0.71 (-1.40, -0.02)], while the effectiveness of chlorhexidine remained elusive.

CONCLUSIONS

Both mechanical and chemical approaches had been applied to caries and gingivitis prevention among children and adolescents with ID. Insufficient evidence supported the efficacy of chlorhexidine nor powered toothbrush, while fluoride was suggested to be an effective caries preventive strategy in fluoride-deficient areas. More well-designed randomised controlled trials using integration strategies are encouraged in further studies.

Pulmonary Arteriovenous Malformation Masquerading as Massive Pulmonary Thromboembolus

We present a case of a 78-year-old male with hereditary haemorrhagic telangiectasia and severe hypoxia incorrectly diagnosed as pulmonary embolism following a false positive ventilation/perfusion scan. Anti-coagulation and thrombolysis was complicated by an upper gastro-intestinal haemorrhage. Pulmonary arteriovenous malformations resulted in a clinically significant right-left shunt and created an apparent perfusion defect evident upon radionuclide imaging, leading to diagnostic uncertainty and a potentially dangerous treatment modality.

Structural Determinants and Children's Oral Health: A Cross-National Study

Much research on children's oral health has focused on proximal determinants at the expense of distal (upstream) factors. Yet, such upstream factors-the so-called structural determinants of health-play a crucial role. Children's lives, and in turn their health, are shaped by politics, economic forces, and social and public policies. The aim of this study was to examine the relationship between children's clinical (number of decayed, missing, and filled teeth) and self-reported oral health (oral health-related quality of life) and 4 key structural determinants (governance, macroeconomic policy, public policy, and social policy) as outlined in the World Health Organization's Commission for Social Determinants of Health framework. Secondary data analyses were carried out using subnational epidemiological samples of 8- to 15-y-olds in 11 countries ( N = 6,648): Australia (372), New Zealand (three samples; 352, 202, 429), Brunei (423), Cambodia (423), Hong Kong (542), Malaysia (439), Thailand (261, 506), United Kingdom (88, 374), Germany (1498), Mexico (335), and Brazil (404). The results indicated that the type of political regime, amount of governance (e.g., rule of law, accountability), gross domestic product per capita, employment ratio, income inequality, type of welfare regime, human development index, government expenditure on health, and out-of-pocket (private) health expenditure by citizens were all associated with children's oral health. The structural determinants accounted for between 5% and 21% of the variance in children's oral health quality-of-life scores. These findings bring attention to the upstream or structural determinants as an understudied area but one that could reap huge rewards for public health dentistry research and the oral health inequalities policy agenda.

Low-dose naltrexone: a novel treatment for Hailey-Hailey disease

Hailey-Hailey disease (chronic benign familial pemphigus) is a rare inherited dermatosis typically characterized by erosions at intertriginous sites preceded by minor trauma or stress. We report a case of treatment-resistant Hailey-Hailey disease having failed topical and oral steroids, prophylactic aciclovir and doxycycline, and systemic therapies including dapsone, acitretin and ciclosporin. Low-dose naltrexone 4·5 mg once daily was commenced following an incidental benefit in this patient's similarly affected sister. The clinical and psychological response to date has been considerable.

The effect of antiseptic oral sprays on dental plaque and gingival inflammation: A systematic review and meta-analysis

OBJECTIVES

To review the effectiveness of antiseptic oral sprays on oral health.

METHODS AND MATERIALS

Three electronic databases (PubMed, Cochrane Library and Web of Science) were systematically searched to identify relevant studies. Only randomized controlled trials (RCTs) comparing the effect of oral sprays to placebo/control spray or mouthrinse on dental plaque and gingival inflammation were included.

RESULTS

Among a total of 996 papers, 20 effective studies fulfilled the selection criteria, and 8 studies were suitable for inclusion in meta-analyses. A meta-analysis of three studies using a 0.2% chlorhexidine (CHX) spray intervention, without prophylaxis at baseline, showed reductions in Plaque Index (PI) (Silness and Löe) and Gingival Index (GI) (Silness and Löe) scores of 0.74 (95% CI: -1.03 to -0.45) and 0.22 (95% CI: -0.38 to -0.06), respectively. Five studies provided a prophylaxis for subjects before study initiation. Three of these five studies used 0.2% CHX spray. A meta-analysis demonstrated an increase of 0.18 (95% CI: -0.01 to 0.37) in PI (Silness and Löe) scores. Two RCTs compared 0.12% and 0.2% CHX spray, and a meta-analysis showed increases of 1.71 (95% CI: 1.27 to 2.14) and 1.58 (95% CI: 1.23 to 1.93), respectively, in PI (Quigley and Hein) scores. Of the RCTs not amenable to meta-analysis, eight studies reported significant improvements in PI and GI scores.

CONCLUSIONS

Available evidence suggests that oral sprays are an acceptable delivery method for antiseptic agents. Further high-quality studies are warranted to determine the effectiveness of alternative chemotherapeutic agents delivered via oral sprays on oral health.

Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA

We present possible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron star systems, which are the most promising targets for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and [Formula: see text] credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5-[Formula: see text] requires at least three detectors of sensitivity within a factor of [Formula: see text] of each other and with a broad frequency bandwidth. When all detectors, including KAGRA and the third LIGO detector in India, reach design sensitivity, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

Upper Limits on the Stochastic Gravitational-Wave Background from Advanced LIGO's First Observing Run

A wide variety of astrophysical and cosmological sources are expected to contribute to a stochastic gravitational-wave background. Following the observations of GW150914 and GW151226, the rate and mass of coalescing binary black holes appear to be greater than many previous expectations. As a result, the stochastic background from unresolved compact binary coalescences is expected to be particularly loud. We perform a search for the isotropic stochastic gravitational-wave background using data from Advanced Laser Interferometer Gravitational Wave Observatory's (aLIGO) first observing run. The data display no evidence of a stochastic gravitational-wave signal. We constrain the dimensionless energy density of gravitational waves to be Ω_{0}<1.7×10^{-7} with 95% confidence, assuming a flat energy density spectrum in the most sensitive part of the LIGO band (20-86 Hz). This is a factor of ∼33 times more sensitive than previous measurements. We also constrain arbitrary power-law spectra. Finally, we investigate the implications of this search for the background of binary black holes using an astrophysical model for the background.

Directional Limits on Persistent Gravitational Waves from Advanced LIGO's First Observing Run

We employ gravitational-wave radiometry to map the stochastic gravitational wave background expected from a variety of contributing mechanisms and test the assumption of isotropy using data from the Advanced Laser Interferometer Gravitational Wave Observatory's (aLIGO) first observing run. We also search for persistent gravitational waves from point sources with only minimal assumptions over the 20-1726 Hz frequency band. Finding no evidence of gravitational waves from either point sources or a stochastic background, we set limits at 90% confidence. For broadband point sources, we report upper limits on the gravitational wave energy flux per unit frequency in the range F_{α,Θ}(f)<(0.1-56)×10^{-8}    erg cm^{-2} s^{-1} Hz^{-1}(f/25  Hz)^{α-1} depending on the sky location Θ and the spectral power index α. For extended sources, we report upper limits on the fractional gravitational wave energy density required to close the Universe of Ω(f,Θ)<(0.39-7.6)×10^{-8}  sr^{-1}(f/25  Hz)^{α} depending on Θ and α. Directed searches for narrowband gravitational waves from astrophysically interesting objects (Scorpius X-1, Supernova 1987 A, and the Galactic Center) yield median frequency-dependent limits on strain amplitude of h_{0}<(6.7,5.5,  and  7.0)×10^{-25}, respectively, at the most sensitive detector frequencies between 130-175 Hz. This represents a mean improvement of a factor of 2 across the band compared to previous searches of this kind for these sky locations, considering the different quantities of strain constrained in each case.

Oral Health Care Guidelines, Training, and Resources among Stroke Care Providers

During a stroke, the mouth tends to become an unhealthy place and may give rise to various life-threatening conditions. To this end, there have been repeated calls to incorporate oral hygiene guidelines and practices for hospitalized stroke patients to prevent aspiration pneumonia and improve patients' oral health. The objective of the study was to determine health care providers' practices of oral health care among patients hospitalized after an occurrence of stroke and to determine health care providers' background and work environment effect on these practices. A cross-sectional study was conducted among stroke care providers in 13 public hospitals in Malaysia. The questionnaires distributed were self-administered, where nursing staff provided details of their oral health care practices for stroke patients. Information on the background of health care providers and work environment was also collected. Overall, a total of 780 responses from the registered nurses were obtained. Almost half of the respondents (48.1%) reported that they recommended toothbrushing twice or more per day to stroke patients. Two-thirds (64.7%) reported that they performed daily mouthwashing on their patient, while less than half (38.8%) reported daily oral hygiene assistance. Result of the analysis revealed that oral hygiene practices were significantly associated with having working wards ( P < 0.05), level of qualification ( P < 0.05), having oral health care guidelines ( P < 0.001), specific resources ( P < 0.05), and attending previous training in oral care ( P < 0.001). Provision of oral hygiene practices for hospitalized stroke patients is important. A lack of oral health care guidelines, support from dental professionals, specific resources, training, and assistance in daily oral care for patients is evident and detrimental to oral hygiene practices. The current findings have significant implications for new initiatives to support health care providers, particularly the registered nurses performing oral health care for hospitalized stroke patients. Knowledge Transfer Statement: This study may provide a basis of information for improving the delivery of oral health care to stroke patients. Enhancement in the training and improvement in the existing guidelines and resources is pivotal for the provision of better oral health care for the potential benefits to these patients, including their improved quality of life and disease prevention.

Oral health of Hong Kong children: a historical and epidemiological perspective

OBJECTIVE

To provide a historical and epidemiological overview of the oral health of Hong Kong children.

METHODS

Literature published before 2014 related to the oral health of Hong Kong children, supplemented with information accessed from government-archived oral health reports, was sourced using electronic databases and hand searches. Dental caries experience, periodontal health, enamel defects, and malocclusion of Hong Kong children were reviewed.

RESULTS

A decline in the prevalence and extent of dental caries was observed among Hong Kong schoolchildren and adolescents after the 1960s. Among preschool children, however, dental caries remains common and the extent appears to have increased. The periodontal health of Hong Kong children remains unsatisfactory. Recently, enamel defects/dental fluorosis have considerably reduced. Information about malocclusion in Hong Kong children is limited.

CONCLUSIONS

Since the 1960s, following public health policies, health promotion activities, and the introduction of a School Dental Care Service, improvements in the oral health of schoolchildren are evident. Nonetheless, the oral health of preschool children remains a concern. Policies and practices to improve the oral health of preschool children in Hong Kong are required.

Early Childhood Dental Problems

Investigations into the wider bioecological understanding of dental problems in early childhood are limited in national surveys. Classification tree analysis (CTA) was used to explore multilevel interactions among key aspects of child and primary caregiver (PCG) psychosocial and physical health affecting dental problems in preschool children. Data were derived from the Growing Up in Ireland study, a nationally representative sample of 9-mo-olds (N = 11,134) in 2007/2008 followed up at age 3 y (N = 9,793) in 2010/2011. Analysis included PCG reports of children’s dental problems, general health, temperament, emotional and behavioral difficulties, and their own general health, stress and depression, relationship, and sociodemographic variables. Misclassification costs were specified for the model by applying a higher penalty for misclassifying those with a dental problem (minority class). Logistic regression analyses were carried out for comparison. Dental problems were reported among 302 infants (2.7%) at 9 mo of age and 493 children (5.0%) at 3 y. CTA identified infant temperament (Infant Characteristics Questionnaire unpredictable) as the primary predictor of dental problems at 9 mo and child global health at 3 y of age. First-level predictors were PCG depression score and use of a soother at 9 mo and PCG ethnicity and unscheduled hospital visits at 3 y of age. Regression analyses results supported the most important predictors at 9 mo and 3 y of age. The CTA model for 9-mo-old infants had a specificity of 90.4%, sensitivity of 31.2%, and overall accuracy of 88.8% while that for 3-y-olds had a specificity of 58.5%, sensitivity of 66%, and overall accuracy of 59%. Key aspects of infant/child and PCG health, as well as psychosocial characteristics associated with reported dental problems, should be considered in future multidisciplinary approaches to child health.

Knowledge Transfer Statement: The results of this data analysis should help raise awareness among clinicians of how primary caregiver and child psychosocial and general health factors are associated with early childhood dental problems, even before the primary dentition is complete. Classification tree analysis visually demonstrates how factors such as infant temperament (9 mo) and child global health (3 y) can interact at multiple levels and affect different subgroups of the child population. Future intervention strategies for oral health should involve consideration of the psychological and general health characteristics of the young child and PCG at both the patient and population levels. This knowledge could assist decision makers adopt an integrated multidisciplinary approach in formulating a coherent oral health policy for preschool children.

The effectiveness of low-level laser therapy as an adjunct to non-surgical periodontal treatment: a meta-analysis

Background and Objectives

Although low‐level laser therapy (LLLT) has been demonstrated to have a biomodulatory effect on periodontal tissue, no systematic review has exclusively addressed its effectiveness as an adjunct to non‐surgical periodontal treatment. This study aimed to evaluate whether an additional benefit exists for the application of LLLT compared with scaling and root planing (SRP) alone.

Material and Methods

An extensive search was conducted in the Cochrane Library (Issue 8, 2015), PubMed (1997) and EMBASE (1947) before August 2015 for randomized controlled trials (RCTs). The bias risk was assessed with the Cochrane tool for risk of bias evaluation. A meta‐analysis was performed using REVMAN 5.3.

Results

After independent screening of 354 initial records, eight publications (seven RCTs) were included. However, six were rated as ‘having a high risk of bias’ as a result of major methodological weakness in ‘allocation concealment’ and ‘blinding of key personnel’. Meta‐analysis showed that LLLT‐mediated SRP demonstrated significant short‐term benefits over SRP monotherapy in the improvement of the probing pocket depth (p = 0.0009 at 1 mo; p = 0.03 at 2 mo) and the level of interleukin‐1β in the gingival crevicular fluid (p = 0.01 at 1 mo). Nevertheless, LLLT failed to show significant additional intermediate‐term (3 and 6 mo) effects in terms of clinical parameters and alveolar bone density.

Conclusion

These findings indicated that LLLT showed only short‐term additional benefits after conventional SRP. Its long‐term effects remain unclear due to substantial methodological weaknesses and an insufficient number of current studies. Future RCTs with better designs and longer follow‐up periods are required to assess the effectiveness of LLLT as an adjunctive treatment strategy in patients with periodontal disease.

Development and evaluation of a Dental Patient Feedback on Consultation skills (DPFC) measure to enhance communication

OBJECTIVES

To adapt an existing medical questionnaire on patient-provider communication for use in the dental setting, and to evaluate the performance of the measure in a first dental encounter (validity and reliability).

METHODS

A patient feedback questionnaire on consultation skills was adapted for use in dental settings through content and convergent validity. A survey of dentist consultation skills was conducted among adults attending a teaching hospital. Patients self-completed a 16-item Dental Patient Feedback on Consultation skills (DPFC) questionnaire during their first dental consultations. Repeat assessments were conducted on -10% of the sample. Variations in DPFC responses (scale and item level) were examined in relation to socio-demographics and dental attendance pattern in bivariate and regression analyses. Internal reliability (Cronbach's alpha) and test-retest reliability (Intraclass Correlation Coefficient - ICC) were examined.

RESULTS

A DPFC questionnaire was derived following minor modifications. The clarity of items ranged from 81.1-100% and content validity index ranged from 0.73-1.00. Exploratory item factor analysis showed a one-dimensional construct. The response rate to the survey was 90.5% (389/430). Variations in DPFC scores with respect to global rating of satisfaction were apparent (P < 0.001). Cronbach's alpha value was 0.94 and ICC value was 0.89. Bivariate and regression analyses identified dental attendance pattern as a key factor associated with DPFC (P < 0.05); but no significant differences were observed with respect to socio-demographic factors.

CONCLUSIONS

A DPFC questionnaire was adapted with acceptable validity and reliability. Dental service utilization pattern was associated with dentist-patient clinical communication rather than socio-demographics.

Multiple tooth loss is associated with vascular cognitive impairment in subjects with acute ischemic stroke

BACKGROUND AND OBJECTIVE

Emerging evidence shows that tooth loss is associated with cognitive impairment and dementia. Vascular cognitive impairment (VCI) is a common consequence of ischemic stroke. This study investigated the association of tooth loss with VCI in patients with acute stroke.

MATERIAL AND METHODS

A total of 161 subjects with acute ischemic stroke were recruited. Within 1 wk after admission, fasting blood tests were undertaken and the number of teeth present was recorded. VCI was evaluated with the Montreal Cognitive Assessment (MoCA).

RESULTS

The patients with loss of ≥ 8 teeth exhibited significantly lower MoCA values as compared to those with loss of ≤ 7 teeth (13.2 ± 6.6 vs. 17.3 ± 6.0, p < 0.001). Multivariate logistic regression analysis showed that loss of ≥ 8 teeth (OR = 3.1, 95% CI: 1.2-7.9, p = 0.02) and stroke history (OR = 3.8, 95% CI: 1.1-14.1, p = 0.04) were significantly associated with VCI (MoCA score ≤ 20.0).

CONCLUSION

Within the limitations of this study, the current findings provide the first evidence that multiple tooth loss is independently associated with VCI in patients with acute ischemic stroke.

Barriers to providing oral health care to pre-school children-differences between paediatric dentists' and general dental practitioners' beliefs

BACKGROUND

The unmet dental needs of pre-school children indicate there are barriers in 'accessing' appropriate oral health care and this warrants consideration of care providers' beliefs.

OBJECTIVE

To explore the beliefs and attitudes of dentists in Hong Kong towards providing oral health care to pre-school children; and to determine difference in attitudes between general dental practitioners (GDPs) and paediatric dentists (PDs).

METHODS

A random sample of 476 GDPs (-25% of all registered dentists) and all registered PDs (28) were invited to participate in the study. Both groups were asked to complete the Barriers to Childhood Caries Treatment (BaCCT) questionnaire: a 29-item measure considering child, parent, dentist and health care system factors. Differences in attitudes of GDPs and PDs were examined in bivariate and regression analyses.

RESULTS

The overall response rate of the study was 61.5% (310/504). There were significant differences in overall BaCCT scores and across all domains between GDPs and PDs (p < 0.05). Furthermore, variations across many aspects (as described at an item level) were apparent. Regression analyses confirmed differences in BaCCT between GDPs and PDs, controlling for practice and other factors.

CONCLUSIONS

Differences exist between GDPs' and PDs' perceptions of barriers to care for early childhood caries. This has implications for how to address 'access' issues with likely implications on how to overcome barriers to care for pre-school children.

What are the key endodontic factors associated with oral health-related quality of life?

AIM

To determine the associations between endodontic factors and oral health-related quality of life (OHQoL), controlling for socio-demographics, pain and other oral health clinical factors.

METHODOLOGY

OHQoL assessments were conducted amongst a consecutive sample of 412 Chinese patients requiring endodontic treatment employing the short-form Oral Heath Impact Profile (OHIP-14). Information on (i) number of teeth requiring endodontic treatment, (ii) tooth type, (iii) retreatment requirements, (iv) periapical radiolucency assessment and (v) diagnostic classification was obtained. In addition, socio-demographic information (age, gender, educational attainment and family income), pain ratings on a visual analogue scale (VAS) and other clinical oral health status information were collected.

RESULTS

Bivariate analyses identified association between number of teeth requiring endodontic treatment and summary OHIP-14 score (P < 0.01) and four of its seven domain scores (P < 0.05). Need for endodontic retreatment was associated with summary OHIP-14 score (P < 0.05) and two of its seven domain scores (P < 0.05). In regression analyses having controlled for socio-demographics, other clinical factors and pain rating amongst 15 confounding variables, patients requiring endodontic treatment for multiple teeth were more than twice as likely to have poor OHQoL (upper quintile OHIP-14 scores) compared with those requiring endodontic treatment for a single tooth (OR = 2.16, 95% CI 1.17, 3.98, P < 0.05). Pain VAS rating and age also emerged as significant factors associated with poor OHQoL in the regression analysis.

CONCLUSION

OHQoL is compromised amongst patients requiring endodontic treatment. Number of teeth requiring endodontic treatment is associated with poor OHQoL, controlling for socio-demographic and other oral health clinical and pain factors.

Silver diamine fluoride and education to prevent and arrest root caries among community-dwelling elders

BACKGROUND/AIMS

Root caries among elderly communities is of growing public health concern globally. This controlled clinical trial investigated the effectiveness of silver diamine fluoride and oral health education in preventing and arresting root caries.

METHODS

Two hundred sixty-six elderly subjects who had at least 5 teeth with exposed root surfaces and did not have serious life-threatening medical diseases were allocated to 3 groups according to a computer-generated random list: group 1 (the control group) received oral hygiene instructions (OHI) annually; group 2 received OHI and silver diamine fluoride (SDF) application annually, and group 3 was given OHI and SDF application annually, plus an oral health education (OHE) programme every 6 months.

RESULTS

Two hundred twenty-seven elderly subjects were followed for 24 months. The mean numbers of new root caries surfaces in groups 1, 2 and 3 were 1.33, 1.00 and 0.70, respectively (ANOVA, p < 0.05). Group 3 had fewer root surfaces with new caries than group 1 (Scheffé multiple-comparison test, p < 0.05). The mean numbers of arrested root caries surfaces in groups 1, 2 and 3 were 0.04, 0.28 and 0.33, respectively (ANOVA, p < 0.01). Group 3 and group 2 had a greater number of active root caries surfaces which became arrested than group 1 (Scheffé multiple-comparison test, p < 0.05).

CONCLUSION

Annual application of SDF together with biannual OHE was effective in preventing new root caries and arresting root caries among community-dwelling elderly subjects.

Journal-based learning, a new learning experience building on PBL at HKU

OBJECTIVE

To evaluate the effectiveness of a new journal-based learning (JBL) programme designed to equip students with skills necessary to understand dental research publications, thereby preparing them for continuing professional development.

MATERIALS AND METHODS

A baseline evaluation of knowledge relating to key research terms was conducted on 52 final-year BDS students. 11 weekly seminars were conducted from 8 clinical disciplines driven by a reading list of 2-5 journal articles along with a series of 'guidance' questions relating to research terms and content knowledge aspects of each paper to focus their reading and learning. Seminars were facilitated by discipline experts with supporting notes. An exit test based on research process and terminologies for the programme was conducted with 4 repeated questions from the baseline assessment. A systematic marking scheme was used and the results analysed. A focus group was run to collect feedback regarding students' views and experiences on the JBL experience.

FINDINGS

Students showed significant improvements over the baseline score. The mean score rose from 3.5 to 11.5 in the repeated questions (P < 0.001). The focus group revealed that students had learnt new information about journal classification, evidence level determination, new research terms and the structure of research papers. From the first 4 years of PBL, students recognized the importance of learning from research papers since year 1. However, JBL gave them a deeper understanding of research and the development of critical appraisal skills.

IMPLICATIONS

JBL provided final-year students the opportunity to learn significantly more about dental research, terminologies, paper structure, critical analysis and content knowledge through active-learning small group seminars.

Self-perceived preparedness for dental practice amongst graduates of The University of Hong Kong's integrated PBL dental curriculum

OBJECTIVES

To determine how prepared for dental practice graduates from the integrated problem-based learning (PBL) dental undergraduate curriculum at The University of Hong Kong (HKU) perceive themselves to be and to identify factors associated with self-perceived preparedness.

MATERIALS AND METHODS

A postal questionnaire was sent to five cohorts of dentists who had graduated from HKU's integrated PBL curriculum between 2004 and 2008. Using a 4-point Likert scale, the questionnaire assessed the self-perceived level of preparedness in 59 competencies grouped in nine domains. Responses were dichotomised into 'poorly prepared' and 'well prepared'.

RESULTS

The response rate was 66% (159/241). The mean proportion (±standard deviation) of respondents indicating well-preparedness was 72.0±15.1% overall, and for each domain was as follows: general patient management, 93.1±12.1%; practice management, 81.0±22.2%; periodontology and dental public health, 73.5±19.3%; conservative dentistry, 92.5±13.1%; oral rehabilitation, 62.8±24.0%; orthodontics, 23.0±32.9%; managing children and special-needs patients, 64.8±28.9%; oral and maxillofacial surgery, 52.2±25.2%; and drug and emergency management, 84.7±22.6%. The odds of self-perceived well-preparedness were increased for cohorts graduating in 2004 and 2005 and graduates working in a non-solo dental practice.

CONCLUSIONS

Dental graduates of HKU's integrated PBL curriculum felt well prepared for the most fundamental aspects of dental practice. However, apparent deficiencies of training in orthodontics and oral and maxillofacial surgery will need to be addressed by continuing education, postgraduate training and planning for the new 6-year undergraduate curriculum in 2012.