The subsurface lesion in erosive tooth wear

OBJECTIVES

This study compared the surface change on natural and polished enamel exposed to a joint mechanical and chemical wear regimen.

METHODS

Human enamel samples were randomly assigned to natural (n = 30) or polished (n = 30) groups, subjected to erosion (n = 10, 0.3% citric acid, 5 min), abrasion (n = 10, 30 s), or a combination (n = 10). Wear in the form of step height was measured with a non-contact profilometer, and surface changes were inspected with SEM on selected sections. Data was normalised and underwent repeated measures MANOVA, accounting for substrate and erosive challenge as independent variables, with Bonferroni correction for significant post hoc interactions.

RESULTS

After four cycles, polished samples had mean step heights of 3.08 (0.40) μm after erosion and 4.08 (0.37) μm after erosion/abrasion. For natural samples, these measurements were 1.52 (0.22) μm and 3.62 (0.39) μm, respectively. Natural surfaces displayed less wear than polished surfaces under erosion-only conditions (p<0.0001), but the difference disappeared with added abrasion. SEM revealed a shallow subsurface layer for polished surfaces and natural ones undergoing only erosion. However, natural surfaces exposed to both erosion and abrasion showed deeper subsurface changes up to 50 µm.

CONCLUSION

Natural enamel, when exposed to erosion alone, showed less wear and minimal subsurface alterations. But with added abrasion, natural enamel surfaces saw increased wear and notable subsurface changes compared to polished ones.

CLINICAL SIGNIFICANCE

The pronounced subsurface lesions observed on eroded/abraded natural enamel surfaces highlight how combined wear challenges may accelerate tooth tissue loss.

Significance of predicted future liver remnant volume on liver failure risk after major hepatectomy: a case matched comparative study

Introduction

Future liver remnant volume (FLRV), a risk factor for liver failure (PHLF) after major hepatectomy (MH), is not routinely measured. This study aimed to evaluate the association between FLRV and PHLF.

Patients and methods

All patients undergoing MH (4 + segments) between 2011 and 2018 were identified from a prospectively maintained single-centre database. Perioperative data were collected for patients with PHLF, who were matched (1:2) with non-PHLF controls. FLRV and FLRV_% (i.e., % of total liver volume) were calculated retrospectively from preoperative CT scans using Synapse-3D software, and compared between the PHLF and matched control groups.

Results

Of 711 patients undergoing MH, PHLF occurred in 27 (3.8%), of whom 24 had preoperative CT scans available. These patients were matched to 48 non-PHLF controls, 98% of whom were classified as being at high risk of PHLF on preoperative risk scoring. FLRV_% was significantly lower in the PHLF group, compared to matched controls (median: 28.7 vs. 35.2%, p = 0.010), with FLRV% < 30% in 58% and 29% of patients, respectively. Assessment of the ability of FLRV_% to differentiate between PHLF and matched controls returned an area under the ROC curve of 0.69, and an optimal cut-off value of FLRV_% < 31.5%, which yielded 79% sensitivity and 67% specificity.

Conclusions

FLRV_% is significantly predictive of PHLF after MH, with over half of patients with PHLF having FLRV_% < 30%. In light of this, we propose that all patients should undergo risk stratification prior to MH, with the high risk patients additionally being assessed with CT volumetry.

The early wear susceptibility of cementum, enamel and dentine in vitro

OBJECTIVES

To assess the differential early wear susceptibility of cementum, enamel and dentine at a micron level.

METHODS

Whole human molar buccal surfaces incorporating natural enamel and cementum (n = 20) confirmed by imaging (digital microscopy: Keyence, VHX-7000 Milton Keynes, UK), were mounted, scanned (profilometry: XYRIS 4000, Taicaan, Southampton, UK), and allocated to receive erosion (citric acid, pH 2.7, 30 min (n = 10)) or erosion/abrasion challenges (3 cycles of (citric acid, pH 2.7, 10 min, 60 300 g linear abrasion strokes), n=10). Samples were polished and the experiment repeated on polished enamel, and polished coronal and radicular dentine within the same tooth. Profilometric wear data were obtained using superimposition: GeoMagic (3Dsystems, Darmstadt, Germany) and subtraction: MountainsMap (DigitalSurf, Besancon, France). Data were normal. A general linear model was used to assess differences between groups and substrates.

RESULTS

The mean step height (SD) for natural enamel was 8.82 μm (2.53) for erosion and 11.48 μm (2.95) for erosion/abrasion. For natural cementum, the mean step height was 6.00 μm (2.29) for erosion and 4.67 μm (1.58) for erosion/abrasion. Dentine step heights ranged from 7.20 μm (1.53) for erosion and 9.79 μm (1.01) for erosion/abrasion with no statistical differences in dentine wear. Natural cementum surfaces had the lowest wear (p<0.001). Dentine had significantly less wear than natural enamel (p<0.02).

CONCLUSIONS

Cementum surfaces demonstrated the most wear resistance, followed by dentine under erosion dominant conditions in this in vitro study. Further in-vivo investigations are needed to confirm the intraoral stability of cementum.

CLINICAL SIGNIFICANCE

Cementum may be the least susceptible of dental substrates to wear and dentine does not wear at a faster rate than enamel under erosive conditions. This adds to our knowledge on the development of non-carious cervical lesions and questions whether wear rates will accelerate once dentine is exposed.

The interplay of saliva, erosion and attrition on enamel and dentine

Purpose

This investigation aimed to compare the protective role of saliva against erosion and attrition challenges.

Method

Polished enamel and dentine samples (n = 160) were prepared and randomly assigned to either the saliva or saliva-free group (n = 40 enamel and n = 40 dentine/group). Within each subgroup, they were allocated to four subgroups: negative control (deionized water exposure 10 min), erosion (0.3% citric acid 10 min), attrition (120 S of 300 g force), or combined erosion/attrition (0.3% citric acid 10 min then 120 S of 300 g force). Experimental cycles were repeated three times. Data analysis was performed using SPSS.

Results

The mean and standard deviation (SD) of step heights produced by the attrition and erosion/attrition groups in enamel in the saliva-free group were 5.6 µm (2.4) and 13.4 µm (2.8), respectively, while they were 2.4 µm (3.8) and 12.9 µm (3.5) in the saliva group, with no significant difference between the saliva and saliva-free groups. For dentine, the corresponding step heights were 25.2 µm (5.5) and 35.9 µm (7.9) for the saliva-free group, but 21.8 µm (5.3) and 27.3 µm (6.4) for the saliva group (p < 0.001).

Conclusion

There was a trend that saliva decreased wear, but this was only statistically significant for erosion/attrition dentine wear.

O-P01 Potential Utility of Intraoperative Fluid Amylase Measurement During Pancreaticoduodenectomy

Background

Postoperative pancreatic fistula (POPF) after pancreaticoduodenectomy (PD) is a source of major morbidity and mortality. Early diagnosis and treatment of POPF is mandatory to improve patient outcomes, and clinical risk scores may be combined with postoperative drain fluid amylase (DFA) values to stratify patients.

The aim of this study was to determine if intraoperative fluid amylase values (IFA) correlate with DFA1 and POPF.

Methods

In consecutive patients undergoing PD between February and November 2020, intraoperative samples of intra-abdominal fluid adjacent to the pancreatic anastomosis were taken and sent for fluid amylase measurement prior to abdominal closure. Data regarding patient demographics, postoperative DFA values, complications and mortality were prospectively collected.

Results

Patient Demographics: Data was obtained for 52 patients with a median alternative Fistula Risk Score (aFRS) of 9.4. Postoperative complications occurred in 20 patients (38%), including five Clavien grade 3+. There were eight POPFs and two patients died (pneumonia/sepsis). There was significant correlation between IFA and DFA1 (Pearson’s correlation: R2=0.713; p &lt; 0.001) and DFA3 (p &lt; 0.001), and median IFA was higher in patients with POPF than patients without (1232.5 vs. 122; p = 0.0003). IFA&gt;260 U/l predicted POPF with sensitivity, specificity, PPV and NPV of 88%, 75%, 39% and 97%, respectively. The incidence of POPF was 43% in high risk (high aFRS/IFA) and 0% in low risk patients (low aFRS/IFA).

Complications:

Conclusions

Intraoperative fluid amylase closely correlated with postoperative pancreatic fistula, and may be a useful adjunct to clinical risk scores to stratify patients during pancreatico-duodenectomy, allowing targeted intervention to reduce the clinical impact of pancreatic fistula.It is possible to detect fluid amylase adjacent to the completed pancreatic anastomosis in patients undergoing PD. Presence of IFA correlates with postoperative DFA and POPF.

IFA increases the accuracy of the alternate Fistula Risk Score in predicting POPF. Low risk patients with a low IFA may be suitable for a ‘no drain’ strategy, whilst patients with a high IFA may benefit from intraoperative mitigation strategies to reduce the incidence and/or severity of a postoperative pancreatic fistula.

Superimposition of sequential scans to measure erosion on unpolished and curved human enamel

OBJECTIVES

To determine if superimposition of sequential scans can discriminate between different fluorides at step heights less than 5 μm on natural human enamel surfaces.

MATERIALS AND METHODS

Natural, unpolished, human enamel specimens (n = 60) were randomly assigned to one of three pre-treatment toothpaste slurries with a calcium silicate/fluoride, fluoride-only and a control. Baseline and post treatment scans, from a non-contacting profilometer with a 0.01 μm z-axis and <1 μm lateral scanning resolution were imported into superimposition software to define change in mean 3D step height and surface roughness following erosion in 0.3 % citric acid for 15 min. Statistical analysis conducted with two-way repeated measures ANOVA and post-hoc Tukey's multiple comparisons.

RESULTS

Confidence and resolution of superimposition and subtraction of repeated profiles from unpolished enamel revealed accuracy within 1-2 μm. The technique was able to discriminate between the fluorides demonstrating statistical differences in mean (SD) 3D step height (μm) of 1.96 (0.40) and 2.75 (0.49) (p=0.0024). There was a statistically significant increase in surface roughness for all groups after 15 min erosion compared to baseline. But no statistically significant difference between the interventions after 15 min erosion but there was compared to no fluoride (p=0.006).

CONCLUSION

Superimposition and subtraction of profiles could discriminate between fluoride interventions, which showed statistical differences in enamel loss differences less than 3 μm.

CLINICAL SIGNIFICANCE

This erosion model and data analysis workflow was able to distinguish differences between scans of 3 μm on unpolished enamel following the interaction with fluoride.

Severe Sepsis Mimicking Primary Nonfunction Following Liver Transplantation: Normothermic Machine Perfusion Is a Potential Environment for Bacterial Overgrowth and Transmission From Donor to Recipient. A Case Report

Primary nonfunction (PNF) in the early postoperative period following liver transplantation is fatal if not managed appropriately with early retransplantation. Severe early allograft dysfunction can mimic PNF. The identification of treatable causative factors such as sepsis, hepatic artery, or portal vein thrombosis is essential to distinguish it from PNF, and their early management may avoid the need for retransplantation. In this article, we describe a case of sepsis-induced severe liver dysfunction from a contaminated graft perfused with normothermic machine perfusion (NMP), which presented in a manner similar to PNF. The implications of graft contamination are poorly described. To our knowledge, this is the first report of bacterial contamination of a graft that underwent NMP and subsequently caused severe sepsis in the recipient. The conditions created with NMP may be optimal for certain micro-organisms to thrive. The role of the liver in the immune system is complex as it provides an essential barrier to enterically derived portal venous pathogens and produces numerous acute phase proteins that augment the systemic immune response. Additionally, the liver is also known to restrain harmful and excessive systemic immune responses such as those that occur with the sepsis syndrome. The relationship between bacterial graft contamination, sepsis, and graft dysfunction may be multidirectional.

Tooth wear and aging

BACKGROUND

In an ageing population, tooth wear is likely to increase. It is increasing in prevalence in the younger population and a greater number of patients are retaining their teeth into old age.

METHODS

This paper is a narrative review of the clinical presentation, the epidemiology and the restorative intervention for erosive tooth wear. The dilemmas in managing this common condition with the aging dentition in mind are described. The paper discusses evidence-based prevention methods and highlights how preventive intervention may be preferable over extensive restorative care and high maintenance needs. Patient wishes, expectations and commitment to treatment and maintenance require consideration during clinical decision making.

CONCLUSION

Successful management of erosive tooth wear in an ageing population depends on effective diagnosis, preventive intervention and holistic advice regarding restorative intervention.

Prevalence, severity and explanatory factors of tooth wear in Arab populations

OBJECTIVES

The aim of this study was to assess the prevalence and severity of tooth wear and related risk indicators in six Arab countries.

METHODS

This multicenter, multinational cross-sectional study was conducted among 2924 participants between the ages of 18-35 years old from six Arab countries. Calibrated dentists assessed tooth wear using the Basic Erosive Wear Examination Index (BEWE). Participants were also asked to complete a questionnaire that assessed their dietary and oral health habits. Each participant was identified by the sextant with the highest BEWE score in the upper and lower jaws.

RESULTS

Odds ratios were estimated for correlates of tooth wear anterior and posterior regions. Oman had the highest prevalence of BEWE score 3 (N = 255 (60.2%)). Overall, the highest BEWE score 3 was observed on the incisal edge of the upper anterior teeth (N = 602 (20.6%)) and in the lower left posterior region (sextant 6) on the occlusal surface (N = 466 (15.9%)). Correlates of severe tooth wear in both regions were eating or drinking more than six times per day, age and education. Drinking soft drinks "once a day" was significantly associated with severe tooth wear in the posterior region (OR: 1.3, 95% CI:1.05, 1.6). Brushing teeth more than twice a day was inversely associated with tooth wear in the anterior region (OR:0.75, 95% CI: 0.57,0.97).

CONCLUSION

The prevalence of tooth wear in Arab populations is relatively high, specific preventive and therapeutic measures should be developed to target people at higher risk of this condition.

CLINICAL SIGNIFICANCE

Tooth wear is now regarded as a significant oral health problems, dentists should advise their patients about dietary and oral health habits that can lead to severe tooth wear.

Randomised Controlled Clinical Trial Investigating The Impact of Implementation Planning on Behaviour Related to The Diet

There is a perceived gap between dietary advice given by health practitioners and adherence to the advice by patients. We investigated whether a behaviour change technique (implementation-planning) was more effective than standard-of-care diet advice at reducing dietary acid intake using quantitative erosive tooth wear progression as an objective clinical outcome. This study was a randomised controlled, double-blind, single-centre clinical trial in the UK. Participants (n = 60) with high dietary acid intake (≥2 daily), were recruited and randomly assigned (1:1) to receive either implementation-planning or standard-of-care diet advice in a single clinical session. Questionnaires and impressions were taken at baseline and 6 months later. Dental casts were scanned using laser profilometry and superimposed using surface-matching software. Data were analysed per protocol and intention-to-treat using independent t-tests and Mann-Whitney tests. The intervention group reduced their dietary acid intake between meals to 1 intake per day compared to 2 intakes per day for the controls and demonstrated reduced dental hard tissue volume loss (-0.00 mm³ (SD = 0.01)) compared to controls (-0.07 mm³ (SD 0.17)), p = 0.049. This paper supports the use of implementation planning in clinical practice and presents a non-invasive method of intervention assessment in behaviour change. Larger trials are needed to confirm the generalisability of results.

The influence of varnish and high fluoride on erosion and abrasion in a laboratory investigation

BACKGROUND

The aim of this study was to investigate the potential of concentrated fluoride varnishes to reduce enamel loss from repeated cycles of citric acid erosion and toothbrush abrasion in vitro.

METHODS

Polished human enamel samples were exposed to fluoride varnishes: Bifluorid10® (NaF&CaF2- 45,200 ppmF), Duraphat® (NaF 22,600 ppmF), Fluor-Protector® (difluorsilane 1000 ppmF) and a control coating of copal ether varnish (0 ppmF) group and a deionized water group. For each group of 16 samples, nine cycles of erosion and nine cycles of erosion-abrasion [1 cycle=erosion (0.3% citric acid, pH 3.2, 5 min)+artificial saliva (1 h, pH 7.0)+abrasion (120 linear strokes in artificial saliva from Oral B medium soft brushes 300 g loading]. The change in the enamel surface was evaluated using optical profilometry.

RESULTS

Duraphat® and Bifluorid10® applications had a median (IQR) step height of 4.21 um (1.59) and 5.01 um (1.02). This was statistically significantly less than Fluor-Protector® 6.83 um (1.25), copal ether 7.22 um (1.97) and water 7.39 um (1.96) (p<0.001). For erosion-abrasion, both Duraphat® and Bifluorid® had statistically lower step heights than the other products (p<0.01).

CONCLUSIONS

The action of fluoride in a range of single-application topical varnishes was effective in reducing enamel wear from erosion and erosion-abrasion in this laboratory study.

Family ecology of young children with cerebral palsy

BACKGROUND

Family ecology in early childhood may influence children's activity and participation in daily life. The aim of this study was to describe family functioning, family expectations of their children, family support to their children, and supports for families of young children with cerebral palsy (CP) based on children's gross motor function level.

METHODS

Participants were 398 children with CP (mean age = 44.9 months) and their parents residing in the USA and Canada. Parents completed four measures of family ecology, the Family Environment Scale (FES), Family Expectations of Child (FEC), Family Support to Child (FSC) and Family Support Scale (FSS).

RESULTS

The median scores on the FES indicated average to high family functioning and the median score on the FSS indicated that families had helpful family supports. On average, parents reported high expectations of their children on the FEC and strong support to their children on the FSC. On the FES, higher levels of achievement orientation were reported by parents of children in Gross Motor Function Classification System (GMFCS) level II than parents of children in level I, and higher levels of control were reported by parents of children in level I than parents of children in level IV. On the FEC, parents of children with limited gross motor function (level V) reported lower expectations than parents of children at all other levels.

CONCLUSIONS

Family ecology, including family strengths, expectations, interests, supports and resources, should be discussed when providing interventions and supports for young children with CP and their families.

Consensus guidelines from The American Society of Peritoneal Surface Malignancies on standardizing the delivery of hyperthermic intraperitoneal chemotherapy (HIPEC) in colorectal cancer patients in the United States

BACKGROUND

The American Society of Peritoneal Surface Malignancies (ASPSM) is a consortium of cancer centers performing cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC). This is a position paper from the ASPSM on the standardization of the delivery of HIPEC.

METHODS

A survey was conducted of all cancer centers performing HIPEC in the United States. We attempted to obtain consensus by the modified method of Delphi on seven key HIPEC parameters: (1) method, (2) inflow temperature, (3) perfusate volume, (4) drug, (5) dosage, (6) timing of drug delivery, and (7) total perfusion time. Statistical analysis was performed using nonparametric tests.

RESULTS

Response rates for ASPSM members (n = 45) and non-ASPSM members (n = 24) were 89 and 33 %, respectively. Of the responders from ASPSM members, 95 % agreed with implementing the proposal. Majority of the surgical oncologists favored the closed method of delivery with a standardized dual dose of mitomycin for a 90-min chemoperfusion for patients undergoing cytoreductive surgery for peritoneal carcinomatosis of colorectal origin.

CONCLUSIONS

This recommendation on a standardized delivery of HIPEC in patients with colorectal cancer represents an important first step in enhancing research in this field. Studies directed at maximizing the efficacy of each of the seven key elements will need to follow.

Laryngeal reflex apnea in neonates: effects of CO2 and the complex influence of hypoxia

We have examined influence of hypocapnia, mild hypercapnia and hypoxia on the durations of fictive apnea and respiratory disruption elicited by injection of 0.1ml of water into the laryngeal lumen-the laryngeal chemoreflex (LCR)-in 20 unanesthetized, decerebrate, vagotomized piglets aged 4-10 days that were paralyzed and ventilated with a constant frequency and tidal volume. The LCR was enhanced by hypocapnia and attenuated by hypercapnia as reported by others. The responses to laryngeal stimulation during hypoxia were varied and complex: some animals showed abbreviated responses during the tachypnea of early hypoxia, followed after 10-15min by more prolonged apnea and respiratory disruption accompanying the reduction in ventilatory activity that commonly occurs during sustained hypoxia in neonates. We speculate that this later hypoxic enhancement of the LCR may be due to accumulation of adenosine in the brain stem.

A new index to measure tooth wear--methodolgy and practical advice

A new tooth wear index, designed to measure stages of tooth wear in enamel and dentine is presented. The index measures the lateral spread of wear in enamel and the depth of tooth wear in dentine. The index scores enamel loss at 5 levels and 6 levels in dentine and provides a more sensitive index for monitoring the progression of wear than older indices. The protocols and methods of the index are described and incorporate refinements based on the combined experiences of two independent studies conducted on adults and children. The findings of both studies are summarised and recommendations are made for future studies which investigate the prevalence of tooth wear in adults or children.

Basic Erosive Wear Examination (BEWE): a new scoring system for scientific and clinical needs

A new scoring system, the Basic Erosive Wear Examination (BEWE), has been designed to provide a simple tool for use in general practice and to allow comparison to other more discriminative indices. The most severely affected surface in each sextant is recorded with a four level score and the cumulative score classified and matched to risk levels which guide the management of the condition. The BEWE allows re-analysis and integration of results from existing studies and, in time, should initiate a consensus within the scientific community and so avoid continued proliferation of indices. Finally, this process should lead to the development of an internationally accepted, standardised and validated index. The BEWE further aims to increase the awareness of tooth erosion amongst clinicians and general dental practitioners and to provide a guide as to its management.

Clinical Measurement of Palatal Tooth Wear Following Coating by a Resin Sealing System

This randomized clinical study presents the results of applying a resin-based dentin bonding agent to the palatal surfaces of worn and eroded anterior teeth. The application of the barrier protected the teeth for up to three months.

The perceived barriers of vocational dental practitioners in London to specialisation

OBJECTIVES

To investigate the short- and long-term career aspirations and barriers to postgraduate study of recently qualified vocational dental practitioners (VDPs).

METHOD

One hundred and eight vocational dental practitioners in London were asked to complete a questionnaire survey.

RESULTS

The questionnaires were completed by 94 respondents (85%) and results indicated that the majority of the VDPs wanted to continue to work in general dental practice after vocational training (VT). Nearly 80% of the VDPs were considering undertaking further postgraduate studies in the form of the MFDS examination and 25% were seriously considering undertaking specialist training. Perceived barriers to specialist training included the time, cost and requirement of gaining the MFDS.

CONCLUSIONS

The questionnaire showed that despite recently completing their undergraduate education, VDPs were considering obtaining further qualifications and potentially following a pathway leading to specialist training.

The potential for sodium hexametaphosphate (SHMP) found in common children drinks to limit acid production in the oral biofilm

OBJECTIVE

Sodium hexametaphosphate (SHMP) is a widely used industrial preservative commonly found in children's drinks. In this paper we examined the effect of SHMP incorporated into children's drinks on acid production by the oral biofilm by monitoring salivary concentrations of lactic acid.

MATERIALS AND METHOD

Twelve healthy adult subjects with an average age 36 years (range 26-54 years) consumed 10 ml from four children's beverages (Coca Cola and three types of Sunny Delight supplemented with SHMP) and a standard solution of sucrose. Saliva was collected at intervals following exposure of the oral biofilm to the drinks and the clearance of carbohydrates and the appearance of lactate was measured using standard enzymatic techniques.

RESULTS

All the carbohydrates derived from the drinks were cleared from saliva within 15 min of consumption. Comparison of two drinks [Sunny D Normal and Sunny C] with the same carbohydrate, but different SHMP concentrations suggested that SHMP in these beverages had no significant effect on acid production.

CONCLUSIONS

In this clinical study the role of SHMP, incorporated in common beverages, did not inhibit acid production from carbohydrates.

Multianalyte profiling of serum cytokines for detection of pancreatic cancer

Early detection of pancreatic cancer might improve clinical outcome. Significant alterations in the levels of individual serum cytokines have been reported in pancreatic cancer. We hypothesized that a multicytokine panel could serve as biomarkers for pancreatic cancer. To evaluate the diagnostic utility of such a panel, we have utilized a novel multianalyte LabMAP profiling technology that allows simultaneous measurement of multiple markers. In this study, a panel of 31 serological markers including cytokines, chemokines, growth and angiogenic factors in combination with CA 19-9 was analyzed in sera of pancreatic cancer patients, patients with chronic pancreatitis, and matched control healthy subjects. Statistical analysis identified a multicytokine panel that was able to distinguish pancreatic cancer from healthy controls with a sensitivity of 85.7% and specificity of 92.3%, which was superior to performance of CA 19-9 alone. Importantly, a multicytokine panel allowed the discrimination of pancreatic cancer from chronic pancreatitis with high sensitivity of 98% and specificity of 96.4%. In conclusion, we demonstrated that analysis of multiple serum cytokines using a novel LabMAP technology is a promising approach for development of a diagnostic assay for pancreatic cancer.

Evaluation of individual dosimetry in mixed neutron and photon radiation fields (EVIDOS). Part II: Conclusions and recommendations

The paper presents the main conclusions and recommendations derived from the EVIDOS project, which is supported by the European Commission within the 5th Framework Programme. EVIDOS aims at evaluating state of the art neutron dosimetry techniques in representative workplaces of the nuclear industry with complex mixed neutron-photon radiation fields. This analysis complements a series of individual papers which present detailed results and it summarises the main findings from a practical point of view. Conclusions and recommendations are given concerning characterisation of radiation fields, methods to derive radiation protection quantities and dosemeter results.

Characterisation of mixed neutron photon workplace fields at nuclear facilities by spectrometry (energy and direction) within the EVIDOS project

Within the EC project EVIDOS, 17 different mixed neutron-photon workplace fields at nuclear facilities (boiling water reactor, pressurised water reactor, research reactor, fuel processing, storage of spent fuel) were characterised using conventional Bonner sphere spectrometry and newly developed direction spectrometers. The results of the analysis, using Bayesian parameter estimation methods and different unfolding codes, some of them especially adapted to simultaneously unfold energy and direction distributions of the neutron fluence, showed that neutron spectra differed strongly at the different places, both in energy and direction distribution. The implication of the results for the determination of reference values for radiation protection quantities (ambient dose equivalent, personal dose equivalent and effective dose) and the related uncertainties are discussed.

Evaluation of individual dosimetry in mixed neutron and photon radiation fields (EVIDOS). Part I: Scope and methods of the project

Supported by the European Commission, the EVIDOS project started in November 2001 with the broad goal of evaluating state of the art dosimetry techniques in representative workplaces of the nuclear industry. Seven European institutes joined efforts with end users at nuclear power plants, at fuel processing and reprocessing plants, and at transport and storage facilities. A comprehensive programme was devised to evaluate capabilities and limitations of standard and innovative personal dosemeters in relation to the mixed neutron-photon fields of concern to the nuclear industry. This paper describes the criteria behind the selection of dosimetry techniques and workplaces that were analysed, as well as the organisation of the measurement campaigns. Particular emphasis was placed on the evaluation of a variety of electronic personal dosemeters, either commercially available or previously developed by the partners. The estimates provided by these personal dosemeters were compared to reference values of dose equivalent quantities derived from spectrometry and fluence-to-dose equivalent conversion coefficients. Spectrometry was performed both with conventional multisphere and with some original instrumentation providing energy and direction resolution, based on silicon detectors and superheated drop detectors mounted on or in spherical moderators. The results were collected in a large, searchable database and are intended to be used in the harmonisation of dosimetric procedures for mixed radiation fields and for the approval of dosimetry services in Europe.

Focal warming in the nucleus of the solitary tract prolongs the laryngeal chemoreflex in decerebrate piglets

The laryngeal chemoreflex (LCR), elicited by a drop of water in the larynx, is exaggerated by mild hyperthermia (body temperature = 40-41 degrees C) in neonatal piglets. We tested the hypothesis that thermal prolongation of the LCR results from heating the nucleus of the solitary tract (NTS), where laryngeal afferents first form synapses in the brain stem. Three- to 13-day-old piglets were decerebrated and vagotomized and studied without anesthesia while paralyzed and ventilated. Phrenic nerve activity and rectal temperature were recorded. A thermode was placed in the medulla, and the brain tissue temperature was recorded with a thermistor approximately 1 mm from the tip of the thermode. When the thermode was inserted into the brain stem, respiratory activity was arrested or greatly distorted in eight animals. However, the thermode was inserted in nine animals without disrupting respiratory activity, and in these animals, warming the medullary thermode (thermistor temperature = 40-41 degrees C) while holding rectal temperature constant reversibly exaggerated the LCR. The caudal raphé was warmed focally by approximately 2 degrees C in four additional animals; this did not alter the duration of the LCR in these animals. Thermodes placed in the NTS did not disrupt respiratory activity, but they did prolong the LCR when warmed. Thermodes that were placed deep to the NTS in the region of the nucleus ambiguus disrupted respiratory activity, which precluded any analysis of the LCR. We conclude that prolongation of the laryngeal chemoreflex by whole body hyperthermia originates from the elevation of brain tissue temperature within in the NTS.

Evaluation of individual monitoring in mixed neutron/photon fields: mid-term results from the EVIDOS project

EVIDOS is an EC sponsored project that aims at an evaluation and improvement of radiation protection dosimetry in mixed neutron/photon fields. This is performed through spectrometric and dosimetric investigations during different measurement campaigns in representative workplaces of the nuclear industry. The performance of routine and, in particular, novel personal dosemeters and survey instruments is tested in selected workplace fields. Reference values for the dose equivalent quantities, H(*)(10) and H(p)(10) and the effective dose E, are determined using different spectrometers that provide the energy distribution of the neutron fluence and using newly developed devices that determine the energy and directional distribution of the neutron fluence. The EVIDOS project has passed the mid-term, and three measurement campaigns have been performed. This paper will give an overview and some new results from the third campaign that was held in Mol (Belgium), around the research reactor VENUS and in the MOX producing plant of Belgonucléaire.

Electronic neutron personal dosemeters: their performance in mixed radiation fields in nuclear power plants

This work describes spectral distributions of neutrons obtained as function of energy and direction at four workplace fields at the Krümmel reactor in Germany. Values of personal dose equivalent H(p)(10) and effective dose E are determined for different directions of a person's orientation in these fields and readings of personal neutron dosemeters--especially electronic dosemeters--are discussed with respect to H(p)(10) and E.