Skeletal stability following mandibular advancement with and without advancement genioplasty.

The correction of most cases of skeletal class II mandibular deficiency requires surgical advancement of the mandible for treatment of the malocclusion. Often genioplasty is included in the procedure to improve the soft tissue profile. Long-term skeletal stability is an important goal for the surgeon and orthodontist following bilateral sagittal split osteotomy (BSSO) and is influenced by the muscles attached to the mandible. Following the surgical advancement of the mandible, the suprahyoid muscle complex is stretched and even more so when the procedure is combined with surgical advancement of the chin. This retrospective comparative study determined the long-term skeletal stability of patients who had undergone surgical advancement of the mandible by means of BSSO with an advancement genioplasty, compared to those who had undergone mandibular advancement surgery (BSSO) without an advancement genioplasty. This study concluded that the postoperative hard tissue relapse following BSSO advancement, with or without genioplasty, was clinically insignificant.

A sensitivity analysis of a personalized pulse wave propagation model for arteriovenous fistula surgery. Part A: Identification of most influential model parameters.

Previously, a pulse wave propagation model was developed that has potential in supporting decision-making in arteriovenous fistula (AVF) surgery for hemodialysis. To adapt the wave propagation model to personalized conditions, patient-specific input parameters should be available. In clinics, the number of measurable input parameters is limited which results in sparse datasets. In addition, patient data are compromised with uncertainty. These uncertain and incomplete input datasets will result in model output uncertainties. By means of a sensitivity analysis the propagation of input uncertainties into output uncertainty can be studied which can give directions for input measurement improvement. In this study, a computational framework has been developed to perform such a sensitivity analysis with a variance-based method and Monte Carlo simulations. The framework was used to determine the influential parameters of our pulse wave propagation model applied to AVF surgery, with respect to parameter prioritization and parameter fixing. With this we were able to determine the model parameters that have the largest influence on the predicted mean brachial flow and systolic radial artery pressure after AVF surgery. Of all 73 parameters 51 could be fixed within their measurement uncertainty interval without significantly influencing the output, while 16 parameters importantly influence the output uncertainty. Measurement accuracy improvement should thus focus on these 16 influential parameters. The most rewarding are measurement improvements of the following parameters: the mean aortic flow, the aortic windkessel resistance, the parameters associated with the smallest arterial or venous diameters of the AVF in- and outflow tract and the radial artery windkessel compliance.

A sensitivity analysis of a personalized pulse wave propagation model for arteriovenous fistula surgery. Part B: Identification of possible generic model parameters.

Decision-making in vascular access surgery for hemodialysis can be supported by a pulse wave propagation model that is able to simulate pressure and flow changes induced by the creation of a vascular access. To personalize such a model, patient-specific input parameters should be chosen. However, the number of input parameters that can be measured in clinical routine is limited. Besides, patient data are compromised with uncertainty. Incomplete and uncertain input data will result in uncertainties in model predictions. In part A, we analyzed how the measurement uncertainty in the input propagates to the model output by means of a sensitivity analysis. Of all 73 input parameters, 16 parameters were identified to be worthwhile to measure more accurately and 51 could be fixed within their measurement uncertainty range, but these latter parameters still needed to be measured. Here, we present a methodology for assessing the model input parameters that can be taken constant and therefore do not need to be measured. In addition, a method to determine the value of this parameter is presented. For the pulse wave propagation model applied to vascular access surgery, six patient-specific datasets were analyzed and it was found that 47 out of 73 parameters can be fixed on a generic value. These model parameters are not important for personalization of the wave propagation model. Furthermore, we were able to determine a generic value for 37 of the 47 fixable model parameters.

A Multivariate Multilevel Approach to the Modeling of Accuracy and Speed of Test Takers.

Response times on test items are easily collected in modern computerized testing. When collecting both (binary) responses and (continuous) response times on test items, it is possible to measure the accuracy and speed of test takers. To study the relationships between these two constructs, the model is extended with a multivariate multilevel regression structure which allows the incorporation of covariates to explain the variance in speed and accuracy between individuals and groups of test takers. A Bayesian approach with Markov chain Monte Carlo (MCMC) computation enables straightforward estimation of all model parameters. Model-specific implementations of a Bayes factor (BF) and deviance information criterium (DIC) for model selection are proposed which are easily calculated as byproducts of the MCMC computation. Both results from simulation studies and real-data examples are given to illustrate several novel analyses possible with this modeling framework.

A Box-Cox normal model for response times.

The log-transform has been a convenient choice in response time modelling on test items. However, motivated by a dataset of the Medical College Admission Test where the lognormal model violated the normality assumption, the possibilities of the broader class of Box-Cox transformations for response time modelling are investigated. After an introduction and an outline of a broader framework for analysing responses and response times simultaneously, the performance of a Box-Cox normal model for describing response times is investigated using simulation studies and a real data example. A transformation-invariant implementation of the deviance information criterium (DIC) is developed that allows for comparing model fit between models with different transformation parameters. Showing an enhanced description of the shape of the response time distributions, its application in an educational measurement context is discussed at length.

[How calcification in the atherosclerotic aorta can be associated with both a lower risk of recurrent stroke in clinical studies and an increased number of strokes in an autopsy study: interpretation based on selection bias]. / Hoe calcificatie in de atherosclerotische aorta kan samengaan zowel met minder recidiefherseninfarcten in klinisch onderzoek als met een toegenomen aantal herseninfarcten in obductieonderzoek: interpretatie op basis van selectiebias.

Studies evaluating the role ofcalcification in the relationship between aortic atherosclerosis and stroke have led to contradictory conclusions: clinical studies show that aortic calcification is linked to a reduced risk of recurrence in stroke patients, while an autopsy series found a positive association between aortic calcification and stroke. The controversy can be explained by assuming that the risk associated with aortic atherosclerosis varies among individuals. Low-risk patients would live longer and have more time to develop calcification. Consequently, calcification would be a sign of low risk. This explains the apparent recurrence-reducing effect of calcification in stroke patients. The association between aortic calcification and stroke found in an autopsy series does not contradict this hypothesis but supports it: application of Berkson's fallacy shows that calcification is linked to lower mortality.

Dislocation of the mandibular condyle into the middle cranial fossa: report of a case with 5 year CT follow-up.

A 17-year-old patient suffered a dislocation of the right mandibular condyle into the middle cranial fossa following a motorcycle accident. Reduction was delayed because of serious orthopaedic injuries. The condyle was relocated into the glenoid fossa through a combined neurosurgical and preauricular approach. Five years later the patient presented for removal of wisdom teeth and a CT-scan was done to determine the effects of the trauma and management to the condyle. A fibro-osseous ankylosis had occurred in the right temporomandibular joint. The radiological changes confirm that early management appears to improve the prognosis for these injuries.

Transcutaneous electrical nerve stimulation in the treatment of myofascial pain dysfunction.

The effect of transcutaneous electrical nerve stimulation (TENS) plus conservative therapy (ibuprofen, bite plate, self-physiotherapy) on myofascial pain dysfunction (MPD) was determined. A single-blind trial as done in 10 patients with MPD with subthreshold TENS (frequency 35 Hz, pulse width 100 milliseconds, modulation 50%) compared with sham TENS at 8 visits over 14 weeks. Pain was assessed on a visual analogue scale before and after TENS at each visit and the data were analysed with the analysis of variance (ANOVA) for repeated measures. A highly significant effect was seen for time (F = 4.80, P = 0.0003) but not for TENS. Subthreshold TENS did not increase the symptom relief produced by conservative treatment with the protocol used.

Implant-supported prostheses in patients with Sjögren's syndrome: a clinical report on three patients.

Implant-supported prostheses offer a solution to the problems experienced by edentulous patients with Sjögren's syndrome. These patients often find it very difficult, if not impossible, to wear conventional complete dentures. Three clinical reports provide an insight into some of the difficulties involved in treating patients afflicted with this complex multifactorial disease using the Brånemark system.

Screw osteosynthesis compared with wire osteosynthesis in advancement genioplasty: a retrospective study of skeletal stability.

OBJECTIVE: To compare the skeletal stability of wire and screw fixation after advancement genioplasty. DESIGN: Retrospective study. SETTING: Teaching hospital and private practice, South Africa. SUBJECTS: 40 Patients who required advancement genioplasty, 20 in each group. INTERVENTIONS: Advancement genioplasty measurements made on cephalometric radiographs before and immediately after operation, and at least 6 months later. MAIN OUTCOME MEASURES: Comparison of horizontal and vertical measurements. RESULTS: In the screw (rigid) group mean horizontal advancement was 6.3 mm followed by a relapse of 0.3 mm during the follow up period. The corresponding figures for the wire (non-rigid) group were 5.8 and 0.5 mm. The two differed significantly in the degree of vertical change but the result is clinically unimportant. There was no difference in the degree of horizontal change. CONCLUSION: There was no difference in skeletal stability between the two groups.

Diseases and lesions associated with third molars. Review of 1001 cases.

This study reports on a retrospective survey of 1001 panoramic radiographs in a dental school population of persons with impacted third molars. The objective was to determine the association between pathologic conditions visible on radiographs and third molar teeth. In the series 2872 impacted third molars were examined. The most common problem seen radiolucencies. Other than caries, occurrence rates were low. Statistically significant differences in occurrences rates were seen within and between jaws for various pathologic conditions. The low rates did not offer support for the likely presence of pathologic conditions to be an indication for third molar removal.

Glucagon stimulation test: assessment of beta-cell function in gestational diabetes mellitus.

OBJECTIVE: Because women with gestational diabetes mellitus have a risk of up to 60% for the later development of type II diabetes, we used the intravenous glucagon stimulation test to evaluate beta-cell function in pregnant women. PATIENTS: Twenty-seven pregnant women with one or more risk factors for gestational diabetes had an intravenous beta-cell stimulation test. Glucose, C-peptide and insulin levels were measured at baseline and 5, 10 and 15 min after the administration of 1 mg glucagon. The women were classified using the 75-g oral glucose tolerance test according to World Health Organization criteria. During the oral glucose tolerance test glucose, C-peptide and insulin levels were measured at baseline and at 2 h. RESULTS: Insulin and C-peptide responses were significantly lower in pregnant women with impaired glucose tolerance and diabetes compared with women with normal glucose tolerance. CONCLUSION: This study shows gradually decreasing insulin secretion from normal to subnormal in pregnant women without and with glucose intolerance, and diabetes mellitus, respectively.

[A case of oleander poisoning in a cat]. / Een geval van oleanderintoxicatie bij de kat.

This case history describes clinical symptoms and pathological changes in a cat that are consistent with those of oleander intoxication. The clinical symptoms were characterized by vomiting, diarrhoea, and ventricular extrasystoles. On post-mortem examination focal degeneration and necrosis of the myocardium was seen, as well as haemorrhage of myocardium and wall of the gastrointestinal tract. An overview is given of the literature on the diagnosis, pathogenesis, and treatment of oleander intoxication in different animals and in humans.

Cholescintigraphy and biochemical tests in cholecystitis--an evaluation with discriminant analysis.

The biochemical values of 76 patients with suspected cholecystitis were subjected to discriminant analysis. The final diagnoses, i.e. acute cholecystitis, chronic cholecystitis and non-biliary disease, were used as the grouping variable. Cholescintigraphy identified patients with acute cholecystitis. Routine preoperative biochemical tests were found to be of limited value. Only alkaline phosphatase was of help in predicting common-duct stones, especially in patients with acute cholecystitis. The conclusion is that many biochemical tests presently in common use could as well be dispensed with.

The separation of overlapping peaks in cyclic voltammetry by means of semi-differential transformation.

A method for extracting single peaks from complex linear sweep and cyclic voltamperograms is presented. Voltamperograms are transformed by means of semidifferentiation, then all undesired peaks are removed from the semiderivative curve and replaced by calculated baselines. The resulting curve is semiintegrated back, giving a voltamperogram with one peak only. Baselines in the semiderivative domain are determined by the least-squares curve-fitting of datapoints from peak border regions, using the equation that describes the semiderivative peak of a reversible electrode process. With this procedure peaks can be removed without assumptions about the mechanism of the underlying electrode reaction. Due to its design, the algorithm presented is suitable for the fully automatic processing of cyclic and linear sweep voltamperograms. Performance of the procedure was checked with generated reversible voltamperograms as well as in real experiments with both reversible and irreversible systems. The smallest distance between two peaks of equal height, for which the described method can yield correct results, has been found to be 110 mV for a reversible one-electron process at 298 K. This procedure can also be applied to the elimination of the cathodic current from the cyclic voltamperogram of a single component in order to get a pure anodic current value, free from cathodic contribution, or vice versa.

Determination of water in organic solvents by flow-injection analysis with Karl Fischer reagent and a biamperometric detection system.

A flow-injection system with a biamperometric flow-through detector provided with two platinum plate electrodes was tested for the determination of water with a two-component pyridine-free Karl Fischer reagent. The response was shown to be linear in the concentration range 0.03-0.11% water in methanol, ethanol or 2-propanol, with methanol as the carrier solvent. The maximum sampling frequency was about 150 samples per hr. It appeared to be possible to introduce a membrane separation step, thus allowing for the determination of water in fouled process streams. To avoid direct contact between the Karl Fischer solution and the pumping tubes, and thus extend the lifetime of the tubes, an indirect delivery system, based on replacement of the solution by pumped silicone oil, was also applied.