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Biomedical subjects

G Willems

Publications and source records attributed to G Willems.

At least 199 records · Page 11Linked to original sources
PubMedDate not supplied

In vitro peel/shear bond strength of orthodontic adhesives.

OBJECTIVES: The purpose of this study was to evaluate the in vitro peel/shear bond strength of a selection of orthodontic bracket adhesives to human premolar teeth. METHODS: Twenty-two commercially available bracket adhesives were used to bond the same bracket type (Miniature Twin, 3M Unitek, Monrovia, CA. USA) on 264 intact human premolar teeth and then adhesively tested to failure. Peel/shear bond strength values were calculated in newtons and megapascals. The site of bond failure was scored according to the Adhesive Remnant Index. Statistics included one-way analysis of variance and Tukey's Studentized Range test together with Weibull analysis. The latter is a survival analysis able to describe the performance of a material. RESULTS: The mean bond strengths varied from 9.9 MPa for Concise to 4.1 MPa for Heliosit Orthodontic. The overall F-test showed a significant difference (P < 0.0001). No significant differences in bond strength were found between Concise, AccuBond, Imperva Dual, Transbond XT, Kurasper and Spectrum. CONCLUSION: Concise and AccuBond are among the materials of choice for bonding fixed orthodontic appliances to teeth. These materials combine high bond strength with a reliable bond that is easily and quickly debonded.

Acrylic Resins↗
PubMedDate not supplied

Timing of Demirjian's tooth formation stages.

BACKGROUND: Global differences in Demirjian et al.'s method of assessing dental maturity are thought to be due to population differences. AIM: The aim of this study was to investigate the timing of individual tooth formation stages in children from eight countries. RESEARCH DESIGN: This was a meta-analysis of previously published data from retrospective cross-sectional studies of dental maturity. METHOD: Data of mandibular permanent developing teeth from panoramic radiographs (Demirjian's stages) were combined from Australia, Belgium, Canada, England, Finland, France, South Korea and Sweden (n = 9002, ages 2-16.99 years). Age-of-attainment was calculated using logistic regression for each group by sex and meta-analysis of the total. Overlapping 95% confidence intervals of the means was interpreted as no significant difference. RESULTS: Mean ages for each group and total were significantly different in 65 out of 509 comparisons (p < 0.05). Some of these were of small sample size but there was no consistent pattern. Apex closure of the first molar was significantly later in children from Quebec and this might explain differences found in the dental maturity score. CONCLUSIONS: These results suggest no major differences in the timing of tooth formation stages between these children. This fails to explain previous findings of differences using Demirjian's dental maturity method.

Adolescent↗
PubMedDate not supplied

Gallstone pancreatitis in adolescents.

Two female adolescents, 16 and 18 years of age respectively, had to be operated for gallstone pancreatitis. They represented 2.2% of all patients with this disorder, admitted from 1978 to 1987 in our department. In one patient cholelithiasis was associated with obesity, in the other there was a positive family history of gallstones. Congenital anomalies of the biliary tract, hemolytic disorders, early pregnancy and other predisposing factors were absent. Although unfrequent, gallstone pancreatitis is a serious cause of acute abdominal distress in adolescents which can lead to severe morbidity. Adequate biliary tract surgery is curative.

Acute Disease↗
PubMedDate not supplied

Colostomy closure: still a hazardous procedure.

Seventy nine patients with closure of a loop (51 patients) or a terminal (28 patients) colostomy were reviewed retrospectively. Operative mortality was 2.5%. Wound infection in 19% and anastomotic breakdown in 7.7% were the most important postoperative complications. Restoring continuity after a Hartmann intervention, closure of left sided colostomies and early closure (before 12 weeks) all accounted for a statistically significant higher complication rate, while age and sex, the underlying disease, bowel preparation and the method of closure had no influence on the operative outcome.

Colostomy↗
PubMedDate not supplied

Upper gastrointestinal bleeding due to benign tumours of the stomach.

Benign tumours of the stomach are usually asymptomatic and are discovered incidentally during radiology, endoscopy or pathological examination. In some cases, however, these tumours produce overt clinical symptoms. The authors report eight patients with significant upper gastrointestinal bleeding due to benign gastric tumours, who required surgical resection of their lesion. Histologically, the growths proved to be leiomyoma in five cases, polyps in two and lipoma in one. Surgical treatment consisted in local excision in three patients and subtotal gastrectomy in five patients. Bleeding was stopped in all cases and there was no operative mortality.

Aged↗
PubMedDate not supplied

Retroperitoneal leiomyosarcoma.

The clinical history, radiological investigations, pathologic findings and treatment of four patients affected by retroperitoneal leiomyosarcoma were compared with data of the literature. These tumors have a great tendency to develop local recurrences after excision, but metastases to lymph nodes and distant organs usually occur lately. CT examination of the retroperitoneal space is a sensitive tool in the diagnosis and follow-up. Complete excision of the tumor followed by radiotherapy improves significantly the prognosis. Chemotherapy is advisable only when disseminated metastases appear. No correlation was found between the histologic appearance and the clinical behaviour.

Adult↗
PubMedDate not supplied

[Whole bowel irrigation as preparation for colorectal surgery].

One hundred consecutive patients underwent a whole gut irrigation as preoperative care for surgery of the large intestine. The solution used was balanced for isotonicity with mineral salts and polyethylene glycol. The procedure was quite well tolerated by the patients, also by the elderly. Only slight changes in body weight or in serum ionic concentrations were noted. In 88% of the patients the preparation was considered to be good or excellent by the operating surgeon. There was a tendency for low rate postoperative infections.

Adult↗
PubMedDate not supplied

Postoperative duodenal fistulas. A report of 23 cases with emphasis on the surgical treatment by the Roux-en-Y operation.

A series of 23 patients-15 with a spontaneous postoperative duodenal fistula and 8 with a catheter duodenostomy fistula-admitted in both departments between 1974 and 1983, is reviewed. Overall mortality rate was 9%. Using conservative management and parenteral nutrition, spontaneous closure of the fistula was observed in 78% of the cases after an average duration of 33 days. Three patients with an intractable fistula were successfully managed by surgical internal drainage using a Roux-en-Y jejunal loop. Healing time of catheter duodenostomy fistulas was similar to that of spontaneous fistulas. Therefore, deliberate creation of such duodenal fistulas should be carefully considered. The Roux-en-Y operation is recommended for those fistulas that do not heal with conservative management. The latter technique could perhaps be used primarily for the closure of difficult duodenal stumps.

Adult↗
PubMedDate not supplied

Endometriosis of the appendix.

Endometriosis has been encountered in different sites of the gastrointestinal tract. Involvement of the vermiform appendix, however, is rather unusual. Two cases of appendiceal endometriosis are reported in the present study: one patient had symptoms simulating acute appendicitis; in another patient it was an incidental finding during pelvic surgery. There are no clinical signs and findings pathognomonic of endometriosis of the appendix, but the condition may present as appendicitis. At surgery, the diagnosis can only be suspected when it is associated with obvious genital endometriosis. Correct diagnosis is established by microscopic examination of the lesion. Symptomatic endometriosis of the appendix will be cured by appendectomy.

Adenocarcinoma↗
PubMedDate not supplied

Precancerous lesions in the stomach.

Clinical and epidemiological studies indicate that the risk for gastric cancer is increased in pernicious anaemia, atrophic gastritis, postgastrectomy stumps. Ménétrier's disease and gastric adenomatous polyps. Using histoautoradiography, cell maturation disorders have been displayed in all these conditions. Abnormal proliferative patterns or increased uptake of 3H-actinomycin may indicate high risk lesions. However, the predictive value of such histoautoradiographic abnormalities in an individual patient has still to be evaluated by combinating these new techniques with clinical follow-up studies on large series of patients.

Adult↗
PubMedDate not supplied

[Free perforation of the colon in Crohn's disease].

Free intestinal colonic perforation in Crohn's disease. Free intestinal colonic perforation in Crohn's disease is a serious complication. In reference to the case history of a Crohn patient with sigmoid perforation, a literature survey of free colonic perforations has been given. Only 18 cases of free colonic perforations in Crohn's disease have so far been described in world literature. Pathogenesis, treatment and evolution of this affection have been dealt with.

Adult↗
PubMedDate not supplied

Comparison of surface characteristics of six commercially pure titanium abutments.

Clinical studies have reported a positive correlation between the surface roughness of teeth or implants and the rate of supragingival and subgingival plaque maturation. This study compared the surface characteristics of abutments from different implant systems (Astra Tech, Bonefit, Brånemark, Core-Vent, IMZ, and Steri-Oss). For each system, two abutments were examined for surface roughness and surface hardness. The latter served as an indicator for resistance against roughening during professional or habitual oral hygiene procedures. The Ra values (in microns) of the tested abutments were: Steri-Oss, 0.10; IMZ, 0.14; Brånemark, 0.21; Bonefit, 0.23; Astra Tech, 0.27; and Core-Vent, 0.30. The Vickers hardness scores (in VHN) were: Brånemark, 154; IMZ, 208; Astra Tech, 258; Bonefit, 292; Core-Vent, 304; and Steri-Oss, 340. In comparison to most metallographically polished composites, titanium abutments showed a higher initial surface roughness and a slightly higher surface hardness. This may explain, besides the known high surface free energy of titanium, rapid plaque growth on these abutments.

Dental Abutments↗