Biomedical subjects
Publications and source records attributed to G Willems.
This review of literature provides an overview of the most commonly used dental age estimation techniques and focuses on dental age estimation scoring systems in children and adults. In order to obtain a more reliable and reproducible age estimation the forensic odontologist should use several of these available methods whenever an age estimation in the living or dead is required.
BACKGROUND: If medical treatment of obesity fails and if surgical gastroplasty is not indicated, insertion of an intragastric balloon may represent an intermediate modality. METHODS: Two patients are reported in whom a balloon was placed for weight reduction before elective surgery: 1) A 53-year-old woman with a BMI of 41.3 kg/m2 lost 18 kg in 6 months and then underwent surgical repair of a huge incisional hernia; 2) A 58-year-old woman with a BMI of 35.8 kg/m2 had total hip arthroplasty after losing 15.5 kg in 5 months. RESULTS: The uneventful postoperative recovery in both patients was thought to be positively influenced by their preoperative weight loss. CONCLUSION: In morbidly obese patients, intragastric balloon placement may contribute to preoperative weight reduction before elective surgery.
The Edgewise system and the Begg technique were until the early 1970's two of the most familiar and well-known fixed appliance techniques in orthodontics. During the following years they both underwent some slight adaptations that were generally based on more straightforward biomechanics. These changes have led to what in recent years is called the 'Straight Wire technique'. The latter claims to be the treatment option of choice based on preadjusted appliances and preformed arch wires. Besides biomechanics, treatment tools also concentrated on esthetics. It resulted in the development of smaller brackets as well as tooth coloured ones made from polycarbonates or ceramics. Finally lingual orthodontics starts to play a more important role in the orthodontic treatment options for the new millennium.
Successful orthodontic treatment is characterized by optimal anchorage control. Teeth or groups of teeth are united to counteract biomechanical reactive forces during orthodontic treatment. These classic anchorage control mechanisms are less efficient or even non-existent in partially edentulous patients who are missing multiple posterior teeth. However, osseointegrated oral implants ad modum Brånemark can provide optimal anchorage control for orthodontic tooth alignment and rehabilitation of occlusion through prosthetic implant restorations. Careful multidisciplinary planning based on complex diagnostic wax setup casts to determine exact implant location and orientation in line with future orthodontic tooth displacements and prosthetic implant crown restorations is the most important step in the overall treatment planning.
Gastrin can induce mitotic stimulation in the oxyntic mucosa of the stomach, sometimes leading to abnormal growth. We examined whether gastrin was able to influence cell proliferation in the oesophageal epithelium. Rats were treated with gastrin, omeprazole or saline for 3 days, or were subjected to fundectomy or sham operation. Bromodeoxyuridine labelling (LI) and mitotic (MI) indices were counted in the proliferative zone of the squamous epithelium. Infusion of exogenous gastrin, treatment with omeprazole or fundectomy raised the LI and the MI values in the oesophageal epithelium, indicating that gastrin stimulates cell proliferation in the oesophageal mucosa in the rat.
Accurate measurements of the mean energy expended in a gas per ion pair formed (W value) for protons slowed down in alkanes are needed (i) in the fields of neutron metrology and microdosimetry, and (ii) in the field of basic radiation research to check the validity of theoretical models describing the degradation of protons in matter. Here, data for protons at energies of less than 100 keV are of particular interest because W increases strongly with decreasing proton energy in the very low-energy region and shows some structure between 10 keV and 100 keV. For these reasons, the energy dependence of W was studied for completely slowed down monoenergetic protons in the alkane series from methane to pentane at energies 1 keV < or = T < or = 100 keV, by measuring the positive ionization yield produced in a plane-parallel ionization chamber. The final results, which have uncertainties of less than 1.5%, are given in tabular form and also in an analytical representation. They were used to determine the differential value omega of the mean energy expended in a gas per ion pair formed and to analyse differences in proton degradation in the alkanes as a function of the number of carbon atoms.
The effect of experimental gastroesophageal reflux on mitotic activity in the squamous epithelium, as well as in the submucosal glands, of the esophagus was investigated in dogs. The lower esophageal sphincter was destroyed in four dogs using a Wendel cardioplasty, a simple esophagotomy was carried out in four other animals, and four unoperated dogs were taken as controls. Two weeks later, mucosal samples from the esophagus were taken after in vivo labeling of the animals with bromodeoxyuridine. In all mucosal samples the proliferative parameters were estimated in the squamous epithelium, in the submucosal glands and in their excretory ducts. After the cardioplasty, the proliferative parameters were increased (P < 0.05) not only in the esophageal epithelium but also in the submucosal glands and in their excretory ducts (P < 0.05). The amplitude of the proliferative response was more than ten times larger in the latter than that in the surface epithelium. Gastroesophageal reflux is a potent proliferative stimulant to the esophageal squamous epithelium, but also to the cells of the submucosal esophageal glands and their excretory ducts.
BACKGROUND/OBJECTIVE: Gastrin is trophic for the mucosa of the acid-producing part of the rat stomach, notably the histamine-producing ECL cells. Gastrin is said to stimulate growth also of colonic mucosa and colon cancer. The purpose of the present study was to examine whether endogenous hypergastrinaemia had trophic effects on normal colonic mucosa and transplanted colon adenocarcinoma in rats. METHODS: Rats were subjected to fundectomy (surgical removal of the acid-producing part of the stomach) or treatments known to induce endogenous hypergastrinaemia. The treatments included refeeding after 48 h of food deprivation or administration of omeprazole (400 micromol/kg/day, orally). Other operations included colostomy and sham operation. A K12-cell line, originally established from a 1,2-dimethylhydrazine-induced colon adenocarcinoma, was used for transplantation. The rates of cell proliferation were determined in the oxyntic and colonic mucosa and in the tumour by measuring the proportion of the cells that accumulated bromodeoxyuridine in their nuclei, i.e. the labelling index (LI). The thickness of the oxyntic mucosa and the activity of histidine decarboxylase (HDC), the histamine-forming enzyme of the ECL cells, were measured. In addition, the thickness of the colonic mucosa and the weight and volume of the tumour were measured. RESULTS: Refeeding or treatment with a single dose of omeprazole in fasted rats raised the serum gastrin concentration and the LI and HDC activity in the oxyntic mucosa; refeeding but not omeprazole raised the LI in the colonic mucosa. In fed rats, hypergastrinaemia induced by fundectomy or treatment with omeprazole (for 10 days) failed to affect either the LI or the thickness of the mucosa of the proximal colon and the excluded distal colon of the colostomized rats. Fundectomy failed to stimulate the growth of the tumour transplants. CONCLUSION: Endogenous hypergastrinaemia did not induce trophic effects on rat colonic mucosa and did not promote growth of a transplanted colon adenocarcinoma in the rat.
The observation of mitotic figures in the epithelium of the normal gallbladder is exceptional because cell renewal is occurring at a very slow rate. It is only after using 3H-thymidine and autoradiography to observe the cells in DNA synthesis that evidence of a significant epithelial cell replication has been provided. Because numerous mitotic figures and increased 3H-thymidine uptake have been observed after intraluminal introduction of foreign bodies or after ligation of the common bile duct in animals, mechanical distension has been supposed to represent an important trigger factor of cell proliferation in this hollow organ. An increased epithelial cell renewal was also observed in human gallbladders of patients with a complete obstruction of the common bile duct causing the distension. However, the absence of correlation between the degree of gallbladder distension and the proliferative response was suggesting that factors other than distension could be involved. In studies on experimental lithiasis cell proliferation appeared to be enhanced in the gallbladder epithelium of mice fed on a cholesterol-cholic acid-rich lithogenic diet. The fact that the increase in proliferative activity was preceding the formation of gallstones was another indication that factors other than mechanical stimulation by stretching or by the stones may stimulate cell renewal in this organ. Factors in the bile of animals receiving a lithogenic diet could be involved which might cause cellular death and, hence, a regenerative reaction. Direct mitogenic effect of an unknown factor in the bile of these animals is an alternative possibility. On the other hand the stimulating effect of postprandial hormones on gallbladder cell renewal suggested by the observation of a DNA synthesis peak after feeding has been established. Synthetic cholecystokinin analogues have been shown to increase the proliferative activity and to induce epithelial hyperplasia in this organ. In one recent study using fundusectomy to increase the serum gastrin levels, a significant proliferative stimulation in the gallbladder was also observed. In human gallbladder mitotic activity in gallbladders with gallstones in much higher than in the controls. No correlation between stone number, weight or volume and the proliferative activity was put in evidence, whereas cell renewal appeared to be more influenced by the composition of the stones than by their physical presence. Epithelial DNA synthesis activity was, namely, much higher in gallbladders with cholesterol stones than in those with pigment stones. Whether increased cell turnover and, hence, cellular shedding into the lumen could represent a nucleating factor for cholesterol stones is an attractive working hypothesis. Considering the very high frequency of gallstones in man and also the frequent association of gallbladder cancer and lithiasis, further studies on mitotic activity in this organ are required. In conclusion, data from animal experiments and in vitro studies on human gallbladders indicate that gallbladder epithelial cell proliferation may be influenced by several mechanical, chemical and hormonal factors. The list of these factors is still incomplete while their possible role in gallbladder disease is a fascinating exploration field for future research.
The knowledge of the natural history of common bile duct stones in biliary pancreatitis may be helpful in the debate concerning the timing of endoscopic sphincterotomy in relation to surgery. The endoscopic cholangiographies of 211 patients with biliary pancreatitis were analyzed. The presence of bile duct stones was recorded, as well as the time interval between admission and endoscopic retrograde cholangiopancreatography (ERCP). The predicted severity of pancreatitis was determined by the modified Glasgow criteria. The overall incidence of bile duct stones was 28.9%. This incidence was 43.8% during the first 2 days and decreased to < 20% after 1 week. There was no correlation between the severity of disease and the presence of bile duct stones. The performance of an ERCP 1 week after the admission for biliary pancreatitis will avoid a substantial number of unnecessary endoscopic sphincterotomies. Prediction of the severity of disease does not alter the yield of bile duct stones.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Between January 1993 and November 1995 laparoscopic surgery was used in 21 patients with a variety of splenic diseases, namely idiopathic thrombocytopenic purpura, congenital spherocytosis, lymphoma, leukemic infiltrative disease, splenic infarction, trauma, or splenic cyst. Total splenectomy was carried out laparoscopically in 16 patients. Conversion to open splenectomy was necessary in two other patients because of intractable bleeding. Two patients with a splenic cyst underwent laparoscopic unroofing of the cyst. Conservative hemostasis of a spleen injury grade II was carried out in a child after blunt trauma. The total mean duration of the laparoscopic procedures was 158 min and the mean blood loss volume was 350 ml, both conversions being excluded. Postsurgical recovery was excellent and the average hospital stay was 5 days, including the patients with conversion. There were no significant postoperative complications. Our observations indicate that an increasing number of surgical diseases of the spleen can be managed adequately by a less invasive laparoscopic approach. However, the criteria for using this procedure are in an expanding phase and are still mainly dependent on the surgeon's technical experience.
The expression of damage in dental composite restoratives varies widely, going from some local damage as in attrition facets, to generalized failure or collapes of a restoration. However, crack growth lies on the basis of both aforementioned phenomena. It is therefore of primary importance to gain insight in the way structurally differing materials respond to external stress. It is the aim of the present review to summarize some recent in vitro studies that deal with simulation of wear and fatigue phenomena in dental composite restorative materials.
Thrombin production by the phospholipid-bound complex of blood clotting factors Xa and Va (prothrombinase) was studied in a tubular flow reactor. The inner wall of a glass capillary was coated with a phospholipid bilayer of 25% phosphatidylserine and 75% phosphatidylcholine. Prothrombinase was assembled on this bilayer by perfusion with a mixture containing an excess of factor Va (2 nM) and a limiting amount of factor Xa (1-100 pM), either in the absence or presence of prothrombin. The rate of assembly of prothrombinase in the presence of prothrombin appeared to be limited by the transfer rate of factor Xa to the phospholipid surface. A good agreement was found between the predicted mass transfer coefficient for factor Xa and the observed pre-steady state rate of thrombin production. The eventually obtained steady state rates of thrombin production were proportional to the prothrombin concentration and independent of the surface density of prothrombinase. The observed rate of thrombin production was in excellent agreement with the predicted mass transfer rate for prothrombin. Transport-limited prothrombin conversion was observed for prothrombinase densities exceeding 1 fmol/cm2, which corresponds to 0.05% occupation of available binding sites. The kinetic parameters of the reaction were determined at low prothrombinase densities (0.02-0.04 fmol/cm2). Even in this situation the Michaelis-Menten equation had to be corrected for substrate depletion near the catalytic surface. We hereto employed an accurate approximation of the mass transfer coefficient. The kinetic parameter kcat was 60 s-1 and the intrinsic Km had a surprisingly low value of 3 nM. Both parameters were not influenced by the wall shear rate.
Bilateral synchronous multifocal Wilms' tumor is a rare malignancy for which no optimum treatment has been established thus far. The need to preserve renal parenchyma whenever possible is obvious. The authors describe a patient who underwent removal of six subcapsular tumors from a kidney that had been protected from ischemia by in situ cooling with UW-Belzer solution and by surface cooling. This technique was safe, easy to perform, and allowed all the time required to resect the tumors under adequate visual control and to wait for analysis of the frozen sections. It might be a useful alternative to the more complicated "bench" technique.
OBJECTIVES: The marginal quality of four tooth-coloured inlay systems was clinically investigated and subjected to computer-aided semiquantitative marginal analysis under scanning electron microscopy (SEM) after 3 years of clinical service. METHODS: Three of the restoration types were made using the Cerec CAD-CAM apparatus: one was milled from preformed glass ceramic blocks, and the two other inlay types were milled from preformed porcelain blocks. The fourth system was based on an experimental indirect resin composite inlay system. Each inlay type was luted with a different luting resin composite. The clinical evaluation was performed with a mirror and explorer by two clinicians separately, and the marginal analysis was conducted microscopically on replicas (SEM x 200). RESULTS: After 3 years in situ, all the restorations were clinically acceptable. No recurrent caries was observed. Marginal analysis under SEM detected a high percentage of submargination for all four systems, which suggests that their respective resin composite luting agents were all subject to wear. The percentage of marginal fractures on the enamel side as well as on the inlay side did not increase dramatically compared to the 6-month results. CONCLUSION: The first recall after 6 months of clinical service indicated how tooth-coloured inlays behave at their margins. The 3-year results confirmed the early findings, indicating that wear of resin composite lutes is important and present in all systems. The two ceramic materials showed a similar behaviour at the margins. The resin composite inlay performed better at the inlay site than at the enamel site.
Patients with a history of gastroduodenal surgery for benign lesions are at increased risk of developing cancer of the gastric stump. The majority of malignant tumors arising in gastric remnants are adenocarcinomas, but a few of cases of malignant lymphoma have been reported as well. Some recent studies have suggested that Helicobacter pylori-associated gastritis may play a role in the pathogenesis of primary gastric lymphoma. We report a case of primary high grade polymorphic B-cell lymphoma (high grade MALT lymphoma) occurring in the gastric stump of a 74-year-old man 17 years after Billroth-II gastrectomy. The non-tumorous gastric mucosa showed features of reflux gastritis with presence of deeply situated dense lymphoid aggregates in the lamina propria. However, no micro-organisms with the morphology of Helicobacter pylori could be found at the luminal surface. The literature concerning gastric stump lymphomas is reviewed.