Papers by Valentin Rousson
Annals of Statistics, 2000
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Dental Materials, 2011
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Journal of the Mechanical Behavior of Biomedical Materials, 2015
There is no standard test to determine the fatigue resistance of denture teeth. With the increasi... more There is no standard test to determine the fatigue resistance of denture teeth. With the increasing number of patients with implant-retained dentures the mechanical strength of the denture teeth requires more attention and valid laboratory test set-ups. The purpose of the present study was to determine the fatigue resistance of various denture teeth using a dynamic load testing machine. Four denture teeth were used: Bonartic II (Candulor), Physiodens (Vita), SR Phonares II (Ivoclar Vivadent) and Trubyte (Dentsply). For dynamic load testing, first upper molars with a similar shape and cusp inclination were selected. The molar teeth were embedded in cylindrical steel molds with denture base material (ProBase, Ivoclar Vivadent). Dynamic fatigue loading was carried out on the mesio-buccal cusp at a 45° angle using dynamic testing machines and 2,000,000 cycles at 2Hz in water (37°C). Three specimens per group and load were submitted to decreasing load levels (at least 4) until all the three specimens no longer showed any failures. All the specimens were evaluated under a stereo microscope (20× magnification). The number of cycles reached before observing a failure, and its dependence on the load and on the material, has been modeled using a parametric survival regression model with a lognormal distribution. This allowed to estimate the fatigue resistance for a given material as the maximal load for which one would observe less than 1% failure after 2,000,000 cycles. The failure pattern was similar for all denture teeth, showing a large chipping of the loaded mesio-buccal cusp. In our regression model, there were statistically significant differences among the different materials, with SR Phonares II and Bonartic II showing a higher resistance than Physiodens and Trubyte, the fatigue resistance being estimated at around 110N for the former two, and at about 60N for the latter two materials. The fatigue resistance may be a useful parameter to assess and to compare the clinical risk of chipping and fracture of denture tooth materials.
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Plasma cell myelomas (PM) exhibit a clinical and molecular heterogeneity. So far, traditional mor... more Plasma cell myelomas (PM) exhibit a clinical and molecular heterogeneity. So far, traditional morphology and immunohistochemistry (IHC) were only of limited value to stratify patients into different prognostic or predictive categories. Among hematological neoplasms, PMs are unique for their extensive genomic instability, involving both numerical and structural rearrangements. Chromosomal translocation involving the IgH locus at 14q32 are seen in most
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Dental materials : official publication of the Academy of Dental Materials, Jan 12, 2015
This is the first meta-analysis on the efficacy of composite resin restorations in anterior teeth... more This is the first meta-analysis on the efficacy of composite resin restorations in anterior teeth. The objective of the present meta-analysis was to verify whether specific material classes, tooth conditioning methods and operational procedures influence the result for Class III and Class IV restorations. The database SCOPUS and PubMed were searched for clinical trials on anterior resin composites without restricting the search to the year of publication. The inclusion criteria were: (1) prospective clinical trial with at least 2 years of observation; (2) minimal number of restorations at last recall=20; (3) report on drop-out rate; (4) report of operative technique and materials used in the trial, and (5) utilization of Ryge or modified Ryge evaluation criteria. For the statistical analysis, a linear mixed model was used with random effects to account for the heterogeneity between the studies. p-Values smaller than 0.05 were considered to be significant. Of the 84 clinical trials, ...
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Dental materials : official publication of the Academy of Dental Materials, 2015
To evaluate the variability of bond strength test results of adhesive systems (AS) and to correla... more To evaluate the variability of bond strength test results of adhesive systems (AS) and to correlate the results with clinical parameters of clinical studies investigating cervical restorations. Regarding the clinical studies, the internal database which had previously been used for a meta-analysis on cervical restorations was updated with clinical studies published between 2008 and 2012 by searching the PubMed and SCOPUS databases. PubMed and the International Association for Dental Research abstracts online were searched for laboratory studies on microtensile, macrotensile and macroshear bond strength tests. The inclusion criteria were (1) dentin, (2) testing of at least four adhesive systems, (3) same diameter of composite and (4) 24h of water storage prior to testing. The clinical outcome variables were retention loss, marginal discoloration, detectable margins, and a clinical index comprising the three parameters by weighing them. Linear mixed models which included a random stud...
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Annals of epidemiology, 2015
We examined the role of smoking in the two dimensions behind the time trends in adult mortality i... more We examined the role of smoking in the two dimensions behind the time trends in adult mortality in European countries, that is, rectangularization of the survival curve (mortality compression) and longevity extension (increase in the age-at-death). Using data on national sex-specific populations aged 50 years and older from Denmark, Finland, France, West Germany, Italy, the Netherlands, Norway, Sweden, Switzerland, and the United Kingdom, we studied trends in life expectancy, rectangularity, and longevity from 1950 to 2009 for both all-cause and nonsmoking-related mortality and correlated them with trends in lifetime smoking prevalence. For all-cause mortality, rectangularization accelerated around 1980 among men in all the countries studied, and more recently among women in Denmark and the United Kingdom. Trends in lifetime smoking prevalence correlated negatively with both rectangularization and longevity extension, but more negatively with rectangularization. For nonsmoking-relat...
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Dental materials : official publication of the Academy of Dental Materials, 2015
When we examined a previously published prospective multi-center clinical trial in which complete... more When we examined a previously published prospective multi-center clinical trial in which complete denture-wearers were followed over a period of 2 years, we found that about 30% of the variability in the clinical wear data of denture teeth was due to unknown characteristics of the subjects. In the second part of the study, we try to identify which patient- and therapy-related factors may explain some of this variability. The clinical wear data of denture teeth at different recall times (6, 12, 18, 24 months) in 89 subjects (at baseline) were correlated with the following parameters, which may all have an influence on the wear of denture teeth: age, gender, bruxism as reported by the subjects, number of prostheses used so far, time since last extraction, smoking, fit of dentures as judged by the subject and the clinician, average denture wearing time and wearing of denture during the night. To evaluate the influence of the different patient- and therapy-related variables, both a univ...
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Research in developmental disabilities, 2014
An established tool for the assessment of motor performance in children with developmental coordi... more An established tool for the assessment of motor performance in children with developmental coordination disorder (DCD) is the Movement-ABC-2 (M-ABC-2). The Zurich Neuromotor Assessment (ZNA) is also widely used for the evaluation of children's motor performance, but has not been compared with the M-ABC-2. Fifty-one children (39 males) between 5 and 7 years of age with suspected DCD were assessed using the M-ABC-2 and the ZNA. Rank correlations between scores of different test components were calculated. The structure of the tests was explored using canonical-correlation analysis. The correlation between total scores of the two motor tests was reasonable (0.66; p<0.001). However, ZNA scores were generally lower than those of M-ABC-2, due to poor performance in the fine motor adaptive component and increased contralateral associated movements (CAM). The canonical-correlation analysis revealed that ZNA measures components like pure motor skills and CAM that are not represented i...
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The Journal of infectious diseases, 2015
Infective endocarditis (IE) mostly occurs after spontaneous low-grade bacteremia. Thus, IE cannot... more Infective endocarditis (IE) mostly occurs after spontaneous low-grade bacteremia. Thus, IE cannot be prevented by circumstantial antibiotic prophylaxis. Platelet activation following bacterial-fibrinogen interaction or thrombin-mediated fibrinogen-fibrin polymerization is a critical step in vegetation formation. We tested the efficacy of antiplatelet and antithrombin to prevent experimental IE. A rat model of experimental IE following prolonged low-grade bacteremia mimicking smoldering bacteremia in humans was used. Prophylaxis with antiplatelets (aspirin, ticlopidine [alone or in combination], eptifibatide, or abciximab) or anticoagulants (antithrombin dabigatran etexilate or anti-vitamin K acenocoumarol) was started 2 days before inoculation with Streptococcus gordonii or Staphylococcus aureus. Valve infection was assessed 24 hours later. Aspirin plus ticlopidine, as well as abciximab, protected 45%-88% of animals against S. gordonii and S. aureus IE (P < .05). Dabigatran etexi...
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British journal of cancer, Jan 17, 2008
Twenty per cent of sentinel lymph node (SLN)-positive melanoma patients have positive non-SLN lym... more Twenty per cent of sentinel lymph node (SLN)-positive melanoma patients have positive non-SLN lymph nodes in completion lymph node dissection (CLND). We investigated SLN tumour load, non-sentinel positivity and disease-free survival (DFS) to assess whether certain patients could be spared CLND. Sentinel lymph node biopsy was performed on 392 patients between 1999 and 2005. Median observation period was 38.8 months. Sentinel lymph node tumour load did not predict non-SLN positivity: 30.8% of patients with SLN macrometastases (> or =2 mm) and 16.4% with micrometastases (< or =2 mm) had non-SLN positivity (P=0.09). Tumour recurrences after positive SLNs were more than twice as frequent for SLN macrometastases (51.3%) than for micrometastases (24.6%) (P=0.005). For patients with SLN micrometastases, the DFS analysis was worse (P=0.003) when comparing those with positive non-SLNs (60% recurrences) to those without (17.6% recurrences). This difference did not translate into signific...
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International journal of colorectal disease, 2003
Carcinoma of the esophagus is an aggressive cancer with a high failure rate after combined local ... more Carcinoma of the esophagus is an aggressive cancer with a high failure rate after combined local and systemic treatment modalities. One of the factors that could influence the high rate of locoregional persistence is hypoxia. Hypoxic cancers are known to be more aggressive and less responsive to chemo- and radiotherapy. We investigated the effect of several factors on overall survival and several surrogate markers of hypoxia on survival in squamous-cell esophageal cancer. We conducted a retrospective analysis of 41 curatively treated patients with squamous-cell esophageal cancer: 30 received combined radio- and chemotherapy (cisplatin and 5-FU) and 11 radiotherapy alone. Cox regression analysis was performed to study the effect of several factors on overall survival. Significantly better survival was shown only in patients who were younger, received more cycles of chemotherapy, or had more proximal tumors or less advanced T stage but not for possible clinical surrogate markers for h...
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Studies in Classification, Data Analysis, and Knowledge Organization, 2008
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Global Heart, 2014
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Studies in Classification, Data Analysis, and Knowledge Organization, 2007
... 1 Statistical Institute, University of Neuchâtel Pierre-`a-Mazel 7, 2000 Neuchâtel, Switzerla... more ... 1 Statistical Institute, University of Neuchâtel Pierre-`a-Mazel 7, 2000 Neuchâtel, Switzerland, yadolah.dodge@unine.ch 2 Neuchâtel Cantonal Statistical Office Le Château, 2001 Neuchâtel, Switzerland, gerard.geiser@ne.ch 3 Department of Biostatistics, University of Zürich ...
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Developmental Medicine & Child Neurology, 2014
Longitudinal studies that have examined cognitive performance in children with intellectual disab... more Longitudinal studies that have examined cognitive performance in children with intellectual disability more than twice over the course of their development are scarce. We assessed population and individual stability of cognitive performance in a clinical sample of children with borderline to mild non-syndromic intellectual disability. Thirty-six children (28 males, eight females; age range 3-19y) with borderline to mild intellectual disability (Full-scale IQ [FSIQ] 50-85) of unknown origin were examined in a retrospective clinical case series using linear mixed models including at least three assessments with standardized intelligence tests. Average cognitive performance remained remarkably stable over time (high population stability, drop of only 0.38 IQ points per year, standard error=0.39, p=0.325) whereas individual stability was at best moderate (intraclass correlation of 0.58), indicating that about 60% of the residual variation in FSIQ scores can be attributed to between-child variability. Neither sex nor socio-economic status had a statistically significant impact on FSIQ. Although intellectual disability during childhood is a relatively stable phenomenon, individual stability of IQ is only moderate, likely to be caused by test-to-test reliability (e.g. level of child&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s cooperation, motivation, and attention). Therefore, clinical decisions and predictions should not rely on single IQ assessments, but should also consider adaptive functioning and previous developmental history.
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PLoS ONE, 2012
The method of instrumental variable (referred to as Mendelian randomization when the instrument i... more The method of instrumental variable (referred to as Mendelian randomization when the instrument is a genetic variant) has been initially developed to infer on a causal effect of a risk factor on some outcome of interest in a linear model. Adapting this method to nonlinear models, however, is known to be problematic. In this paper, we consider the simple case when the genetic instrument, the risk factor, and the outcome are all binary. We compare via simulations the usual two-stages estimate of a causal odds-ratio and its adjusted version with a recently proposed estimate in the context of a clinical trial with noncompliance. In contrast to the former two, we confirm that the latter is (under some conditions) a valid estimate of a causal odds-ratio defined in the subpopulation of compliers, and we propose its use in the context of Mendelian randomization. By analogy with a clinical trial with noncompliance, compliers are those individuals for whom the presence/absence of the risk factor X is determined by the presence/absence of the genetic variant Z (i.e., for whom we would observe X = Z whatever the alleles randomly received at conception). We also recall and illustrate the huge variability of instrumental variable estimates when the instrument is weak (i.e., with a low percentage of compliers, as is typically the case with genetic instruments for which this proportion is frequently smaller than 10%) where the inter-quartile range of our simulated estimates was up to 18 times higher compared to a conventional (e.g., intention-to-treat) approach. We thus conclude that the need to find stronger instruments is probably as important as the need to develop a methodology allowing to consistently estimate a causal odds-ratio.
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The journal of adhesive dentistry, 2012
More than five hundred million direct dental restorations are placed each year worldwide. In abou... more More than five hundred million direct dental restorations are placed each year worldwide. In about 55% of the cases, resin composites or compomers are used, and in 45% amalgam. The longevity of posterior resin restorations is well documented. However, data on resin composites that are placed without enamel/dentin conditioning and resin composites placed with self-etching adhesive systems are missing. The database SCOPUS was searched for clinical trials on posterior resin composites without restricting the search to the year of publication. The inclusion criteria were: (1) prospective clinical trial with at least 2 years of observation; (2) minimum number of restorations at last recall = 20; (3) report on dropout rate; (4) report of operative technique and materials used; (5) utilization of Ryge or modified Ryge evaluation criteria. For amalgam, only those studies were included that directly compared composite resin restorations with amalgam. For the statistical analysis, a linear mi...
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Thalamus and Related Systems, 2005
ABSTRACT The over-inhibition of thalamic relay cells by hyperactivity of the internal part of the... more ABSTRACT The over-inhibition of thalamic relay cells by hyperactivity of the internal part of the globus pallidus is a cornerstone of the parkinsonian pathophysiology that leads to a distortion of the thalamocortical dynamics called thalamocortical dysrhythmia (TCD). Here, we present the results of the stereotactic pallidothalamic tractotomy (PTT), which interrupts selectively the enhanced pallidal output to the thalamus in a restricted location in the fields of Forel. This operation represents a reactualization of Spiegel&#39;s campotomy. PTT was offered to 41 patients (66.1±8.5 years) suffering from chronic, therapy-resistant Parkinson&#39;s disease. It was performed bilaterally in 21 patients. Forty patients displayed mixed, i.e. tremulent and akinetic parkinsonian signs, and seven had drug-induced dyskinesias. One patient had only rest tremor. The evaluation was based on the Unified Parkinson&#39;s Disease Rating Scale (UPDRS) scores, comparing the patients&#39; preoperative medicated state with the state at the last postoperative follow-up. We, thus, tested surgical success in terms of superiority to drug treatment. Mean follow-up was 22.4 months with 15 patients followed for &gt;2 years. Mean improvement was 60% (P&lt;0.001) for UPDRS III and 51% (P&lt;0.001) for UPDRS II. Significant improvement (P&lt;0.001) appeared in subscores for tremor (87%), limb akinesia (58%) and axial akinesia (33%). Improvement of postural stability and gait was at the limit of significance (P&lt;0.05). Improvement of hypomimia and hypophonia did not reach statistical significance. Increase of dysarthria was significant (P&lt;0.01). Intake of L-DOPA was reduced significantly and 21 patients were able to stop intake. Median improvement of the Quality of Life score was 67%. Improvement remained, independent of follow-up length. In conclusion, PTT provides a high, stable level of relief to parkinsonian patients whose condition cannot be controlled with pharmacotherapy. The rationale of the surgical therapy is based on a selective extrathalamic regulation of the parkinsonian TCD.
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Papers by Valentin Rousson