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Biomedical subjects

G Zellweger

Publications and source records attributed to G Zellweger.

At least 19 recordsLinked to original sources
PubMed2005

A comparison of three different methods for the quantification of the in vitro wear of dental materials.

OBJECTIVE: Different approaches are utilized to quantify the wear generated on flat specimens with a wear simulator. However, there are no systematic studies comparing different wear quantification methods with a series of materials that exhibit different wear rates. METHODS: Sixteen restorative materials, including 14 composites (BelleGlass, Chromasit, Estenia, Esthet-X, Four Seasons, Heliomolar RO, Heliomolar HB, Herculite XRV, InTen-S, Point 4, SureFil, Targis cured at 95 and 130 degrees C, Tetric Ceram) as well as an amalgam (Amalcap) and a ceramic (Empress) material, were subjected to attrition wear against standardized Empress antagonists in the Willytec wear simulator (120,000 cycles, 5 kg, 1.6 Hz). The volume and maximal vertical loss were quantified directly on the specimens with a profilometry device (Perthometer) and the FRT MicroProf optical sensor. After the fabrication of plaster replicas, the loss was also determined with a 3D laser scanning device. For the statistical analysis, the data were subjected to a logarithmic transformation. Intraclass correlation was calculated to measure the agreement among all three methods, while limits of agreement were used to compare one method against another. RESULTS: There was a very good agreement between all three quantification methods for both volume and vertical loss. The mechanical sensor measured consistently higher values compared to the optical sensors for the volume loss (correction factor 0.95), whereas for the vertical loss, consistently lower values were obtained (correction factor 1.17). However, the ranking of the materials was only marginally influenced by the quantification method. SIGNIFICANCE: All three sensors are suitable for the quantification of wear facets. Due to speed and simplicity, the laser sensor has greater advantages over the two other sensors.

Acrylic Resins↗
PubMed2005

Influence of the antagonist material on the wear of different composites using two different wear simulation methods.

OBJECTIVES: The aim of the study was to evaluate two ceramic materials as possible substitutes for enamel using two wear simulation methods, and to compare both methods with regard to the wear results for different materials. METHODS: Flat specimens (OHSU n=6, Ivoclar n=8) of one compomer and three composite materials (Dyract AP, Tetric Ceram, Z250, experimental composite) were fabricated and subjected to wear using two different wear testing methods and two pressable ceramic materials as stylus (Empress, experimental ceramic). For the OHSU method, enamel styli of the same dimensions as the ceramic stylus were fabricated additionally. Both wear testing methods differ with regard to loading force, lateral movement of stylus, stylus dimension, number of cycles, thermocycling and abrasive medium. In the OHSU method, the wear facets (mean vertical loss) were measured using a contact profilometer, while in the Ivoclar method (maximal vertical loss) a laser scanner was used for this purpose. Additionally, the vertical loss of the ceramic stylus was quantified for the Ivoclar method. The results obtained from each method were compared by ANOVA and Tukey's test (p<0.05). To compare both wear methods, the log-transformed data were used to establish relative ranks between material/stylus combinations and assessed by applying the Pearson correlation coefficient. RESULTS: The experimental ceramic material generated significantly less wear in Tetric Ceram and Z250 specimens compared to the Empress stylus in the Ivoclar method, whereas with the OHSU method, no difference between the two ceramic antagonists was found with regard to abrasion or attrition. The wear generated by the enamel stylus was not statistically different from that generated by the other two ceramic materials in the OHSU method. With the Ivoclar method, wear of the ceramic stylus was only statistically different when in contact with Tetric Ceram. There was a close correlation between the attrition wear of the OHSU and the wear of the Ivoclar method (Pearson coefficient 0.83, p=0.01). SIGNIFICANCE: Pressable ceramic materials can be used as a substitute for enamel in wear testing machines. However, material ranking may be affected by the type of ceramic material chosen. The attrition wear of the OHSU method was comparable with the wear generated with the Ivoclar method.

Aluminum Silicates↗
PubMed1994

[Fulminant purpura in Still's disease and bacteremia with Xanthomonas maltophilia and coagulase-negative staphylococci].

We describe the case of a 31-year-old man with a long history of juvenile rheumatoid arthritis who was admitted to the hospital because of painful purple skin lesions on hands and feet. On admission he presented the classical picture of "purpura fulminans" with extensive acrocyanosis and large blisters on the lower limbs which evolved into symmetrical peripheral gangrene. Laboratory findings revealed activated intravascular coagulation and bacteremia with coagulase-negative staphylococci and Xanthomonas maltophilia which was thought to be catheter-related. His condition improved markedly under therapy with antibiotics, intravenous heparin, iloprost and intensive local debridement including amputation of several toes. Coagulation studies two months after the acute phase of the disease revealed chronic activated coagulation with a significant protein S deficiency. Clinical findings, etiology, significance of impaired coagulation and therapeutic action in "purpura fulminans" are discussed.

Adult↗
PubMed1992

[Severe necrotizing fasciitis].

The pathophysiology of necrotizing fasciitis remains unclear in patients with no apparent immunologic disorders. Between 1987 and 1990 we treated six patients with necrotizing fascitis and septic-toxic multiple organ failure, three patients survived. The mean age was 38 years (25-62). In all patients the primary bacteriological examination revealed streptococcus. Between the first symptoms and an adequate therapy were 4 days in surviving patients and 7 days in patients who died. Four patients showed spread of the gangrene into the adjacent tissue: muscles (n = 3), bowel (n = 2), mediastinum (n = 1). Adequate débridement was not possible or not performed in patients with spread into the abdominal cavity or the mediastinum. These patients did not survive. The duration of intensive care treatment in surviving patients were 14 to 78 days. We conclude that survival of patients with severe necrotizing fasciitis is influenced by the delay before adequate treatment, the localisation of the gangrene and intensive care facilities.

Adult↗
PubMed1991

Tissue expanders in reconstruction of burn sequelae.

In 20 patients with burn scars and 1 patient with a fresh burn, 33 tissue expanders were implanted. In 16 patients, the expansion fulfilled the goal set with the help of 27 expanders. The results are very satisfactory, but the effort of treatment and the trouble are substantial. Thirteen patients encountered no complications. In terms of expanders, there were 6 major and 11 minor complications. They were infection (three), wound dehiscence (two), insufficient expansion with hematoma (one), leakage (six), superficial skin damage (three), and intercurrent hematoma formation (two). There was no flap necrosis, and thus, apart from superfluous surgery, no real damage. Retrospectively, the major complications could have been avoided by more careful observance of indications. Unfortunately, this seems to be a process that every surgeon must learn by experience and not by theory alone. Here, infection was managed by removal of the expanders. Hematomas should be evacuated early (we drained most expanders), and incidences of leakage can be diminished by using larger valves. Small incisions in healthy tissue for expander insertion may lead to faster onset of expansion, thus, shortening the procedure. Late widening of scars was found only once, perhaps due to a rather long duration of expansion, averaging 13 weeks.

Adolescent↗
PubMed1989

[Therapeutic possibilities in hand burns].

Four methods of treating the burned hand are possible: conservative treatment of superficial dermal burns, tangential excision and immediate grafting of deep dermal and barely full thickness burns, granulation method with late grafting of deep dermal to deep full thickness burns, flap procedures of full thickness burns. The tangential excision and grafting of deep dermal and barely third degree burns has improved the well being of the patient by good functional and cosmetic results, less hospitalization time (10-14 days) and less pain. The procedure is described. Tangential excision is contraindicated in the very deep burn. In these the growth of granulations or in certain cases the application of skinflaps will produce better results. Important as to the result is the aftercare consisting of compression gloves and physiotherapy. Even with progress the deep burn remains a devastating injury to the delicately operating hand. Nevertheless the appropriate therapy can achieve good results.

Burns↗
PubMed1986

[Toxic epidermal necrolysis (Lyell syndrome)].

Toxic epidermal necrolysis, a serious allergically triggered skin reaction, has a mortality of about 30% largely due to internal diseases. The management involves several specialties. Clinical picture and therapy are described in a case probably induced by allopurinol, with 70% involvement of body surface.

Aged↗
PubMed1986

[Liver injuries].

Mortality in blunt hepatic trauma is still high, death being most frequently caused by hemorrhage. Associated injuries are present in nearly all cases. A variety of possible surgical procedures allow treatment tailored to fit the individual situation. Even the sophisticated intensive care required by the frequent posttraumatic complications is not a substitute for adequate surgery.

Abdominal Injuries↗
PubMed1981

[Causes of death in burn patients].

Analysis of causes of death in 54 patients in the Zürich Burn Center has shown that pneumonia and septicemia occur secondary to pulmonary edema. Pulmonary infection and septicemia were the main causes of death in our cases. Pathophysiologically, a timetable of danger phases can be established: a) 1st day: death from unknown cause (organ edemas); b) 2nd to 6th day: pneumonia and pulmonary edema in combinations of varying degrees; c) after the 6th day: death from pneumonia and septicemia. Wound infection alone seldom causes septic death. From this it is concluded that the badly burned patient should not be overhydrated in the initial phase of therapy. Kidneys can be subjected to more strain than was previously supposed.

Brain↗
PubMed1979

[Burn mortality and morbidity: experience of the burn center in Zürich from 1967 to 1977].

Ten years of burn treatment in a burn center are compared to the ten years prior to 1967: --Survival has increased markedly, due to aggressive local treatment with débridement, topical ointments, biologic dressings, and rapid closure of wounds. --Functional and cosmetic results have improved since tangential excision and immediate autografting are routinely performed. --Favourable results with shorter duration of hospitalization are obtained if doctors and nurses can acquire and apply their knowledge in many cases as is possible in a burn center.

Burns↗
PubMed1978

[Experiences of tangential excision of burned hands].

Tangential excision and immediate grafting of deep burns of the hands enable wound closure within 14 days. Mobility of the hand is rapidly restored, pain is practically omitted, scar formation is minimized, and sensitivity is restored to normal in the majority of cases. Considering only surviving patients accounting for a total of 247 hand (hospitalisation from January 1974 to June 1977), we tangentially excised 118 hands. Two thirds of the tangential excisions needed no more corrections. One third had corrections of interdigital webs, dermabrasion of graft margins, excision of scars, or correction of contractions mainly of the fifth finger. On questioning, half of the patients admitted increased vulnerability of the transplanted skin but were not impeded by this. Work incapacity in those cases in which the hands determined the uptake of manual labour was only 5 weeks.

Burns↗