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Biomedical subjects

M Persson

Publications and source records attributed to M Persson.

At least 73 records · Page 4Linked to original sources
PubMed1996

Metal-ceramic bond strength.

No currently available bond test for dental metal ceramic systems has yet gained general acceptance. Such a bond test cannot be established without careful analysis of the stress distribution within the adherence region. The objective of the present study was to establish a mechanical shear stress test and combine the results with a finite element stress analysis of an idealized crown to enable comparisons of different metal-ceramic systems. The titanium-ceramic systems tested, both machined and cast titanium, showed higher shear strength values than the high gold-ceramic system used as a reference. Since the latter system has been used successfully in the clinic for many years, it seems reasonable to assume that the bond strength of titanium-ceramic systems is quite satisfactory for dental crown-and-bridge work. In conclusion, the interfacial bond strength test proposed in the present study should be applicable to all of the currently known material combinations in which a brittle fracture might be expected to occur.

Ceramics↗
PubMed1995

GroEL/ES-mediated refolding of human carbonic anhydrase II: role of N-terminal helices as recognition motifs for GroEL.

The presence of GroEL/ES during the refolding of human carbonic anhydrase II (pseudo-wild type) was found to increase the yield of active enzyme from 65 to 100%. This chaperone action on the enzyme could be obtained by adding GroEL alone, and the time-course in that case was only moderately slower than the spontaneous process. Truncated forms of carbonic anhydrase, in which N-terminal helices were removed, also served as protein substrates for GroEL/ES. This demonstrates that N-terminally located helices are not obligatory as recognition motifs.

Binding Sites↗
PubMed1995

The accuracy of a high-precision digitizer for CAD/CAM of crowns.

An alternative method for manufacturing fixed prostheses that uses machine digitalization and a combination of milling and spark erosion has been developed. The digitizer used has a contact probe with a ball-shaped tip. This study evaluated the accuracy of the device and the transfer of data from the individual die to the computer. The dimensions of a square gauge as read by the machine were compared with the known dimensions of the object with a computer, which allowed determination of the accuracy of the digitalization. Procera machining and the implications for reliable prosthodontic treatment are discussed.

Analog-Digital Conversion↗
PubMed1995

The role of sutures in normal and abnormal craniofacial growth.

The paper is a shortened version of a paper read at the symposium on craniofacial growth, in which the literature on various aspects of sutures was reviewed. Suture development, structure, growth, and closure are covered, and the response of sutures to orthopedic forces and their role in craniosynostosis exemplified. Rather than being an extensive review, references are included preferably to present diversity in results and methods within the subtitle of the symposium, 'mechanisms and study methods'.

Animals↗
PubMed1995

To dress or not to dress surgical wounds? Patients' attitudes to wound care after major abdominal operations.

OBJECTIVE: To find out what patients' attitudes were to wound care after abdominal operations to ensure that patients' own views were not violated by introducing a new method of wound care. DESIGN: Randomised study. SETTING: University hospital, Sweden. PATIENTS: 68 consecutive patients operated for benign gastrointestinal disease. INTERVENTIONS: Patients were randomised to have their abdominal wounds dressed or exposed. On their last day in hospital their attitudes were assessed by visual analogue score and questionnaire. MAIN OUTCOME MEASURES: Attitudes to wound care. RESULTS: There were no differences between the two groups in any of the variables studied. The visual analogue scores for postoperative pain were higher than had been anticipated. CONCLUSION: Most patients do not mind whether their wounds are covered with a dressing or not after abdominal operations.

Abdomen↗
PubMed1994

Use of genetically prepared enzyme conjugates in lactose and galactose analyses.

Genetically prepared enzyme conjugates were used in soluble enzyme assays for determination of lactose and galactose with spectrophotometric, fluorimetric, and bioluminometric detection. The use of a bifunctional enzyme in biosensors based on calorimetric detection is also presented. Due to proximity of the enzymes to one another several advantages in the analyses were achieved. The lag phase of coupled enzymatic reactions was reduced and the steady-state rates were increased, which could increase the sensitivity of the assays and decrease the time of analysis.

Arabinose↗
PubMed1994

Bradykinin and thrombin stimulate release of arachidonic acid and formation of prostanoids in human periodontal ligament cells.

Previous reports have demonstrated the importance of prostaglandin formation in orthodontic tooth movement, but the mechanisms involved in the activation of prostaglandin biosynthesis in the periodontal ligament (PDL) are still unclear. There is, however, evidence that inflammatory reactions appear after application of orthodontic forces. In the present study, the effect of bradykinin (BK) and thrombin, two inflammatory mediators, on prostanoid biosynthesis in human PDL-cells was investigated. BK and thrombin caused a time-dependent burst of prostaglandin E2 (PGE2) formation (maximal effect after 2-5 min). The stimulatory actions of BK and thrombin on PGE2 biosynthesis were dose-dependent; seen in PDL-cells isolated from four different patients and abolished by the non-steroidal anti-inflammatory drug indomethacin. BK and thrombin also dose-dependently stimulated the biosynthesis of PGI2. BK agonists, with affinity to the B2 subtype of BK receptors, caused a significant increase of PGE2 biosynthesis in human PDL-cells. In contrast, BK agonists with affinity to BK-B1 receptors did not cause a burst of PGE2 biosynthesis. BK and BK-B2 receptor agonists as well as thrombin, but not BK-B1 receptor agonists, also significantly increased [3H] release in human PDL-cells prelabelled with [3H]-arachidonic acid, indicating that BK and thrombin stimulate prostanoid biosynthesis, at least partly, due to activation of phospholipase A2. These data show that BK via BK-B2 receptors, as well as thrombin, have the capacity to stimulate arachidonic acid release and subsequent prostanoid biosynthesis in human PDL-cells and thus may be implicated in the tissue reactions involved in orthodontic tooth movement.

Amino Acid Sequence↗
PubMed1994

The association between spontaneous reversal of gingival recession in mandibular incisors and dentofacial changes in children. A 3-year longitudinal study.

In a previous 3-year longitudinal study, reversal of gingival recession in mandibular incisors was observed for 16 out of 28 participating children aged 6-13 years (Andlin-Sobocki et al., 1991). In the present report various dentofacial conditions that might be associated with this reversal were evaluated from dental casts and cephalometric radiographs by comparing the 16 children with spontaneous reversal of gingival recession (Group Rev) to the 12 children with persisting gingival recession (Group Per). Dental casts and cephalometric radiographs were obtained at baseline and after three years. The findings indicate that the children with persisting gingival recession tended to have a particular facial morphology and incisor pattern. They were likely to have a larger basal bone discrepancy between the maxillary and mandibular jaws, with somewhat more proclined and more irregularly positioned mandibular incisors. Although a reduction in incisor irregularity and a slight increase in anterior arch widths occurred for both groups during the observation period, the tooth alignment situation in Group Per at the end of the observation period was similar to that of Group Rev at baseline. Additionally, in Group Rev all facially deviating incisors with recession at baseline had self-corrected at 3 years. This was not the case for Group Per. Thus, spontaneous reversal of gingival recession in mandibular incisors seem to be related to developmental changes in the dentition favouring incisor alignment.

Adolescent↗
PubMed1994

Prospective study of prevalence and endoscopic and histopathologic characteristics of duodenal polyps in patients submitted to upper endoscopy.

BACKGROUND: Retrospective studies of duodenal polyps have shown a prevalence of 0.3%-1.5% in patients referred to upper endoscopy, and histopathologic classifications have been inconsistent. METHODS: A prospective consecutive study was carried out in 584 patients referred to diagnostic upper endoscopy. Symptoms were registered on a questionnaire, endoscopic and histopathologic findings on standard forms. The same pathologist evaluated all biopsy specimens. RESULTS: Twenty-seven patients had polyps in the first and/or second part of the duodenum, for a prevalence 4.6%. Sixteen polyps were either inflammatory (nine polyps) or ectopic gastric mucosa (seven polyps). Both of these polyp types were practically always non-solitary, sessile, small, and located in the duodenal bulb. Seven polyps were covered by normal mucosa, three being endoscopically typical lipomas. Two polyps were adenomas (0.4% of all the patients and 7% of the polyps), and both were found in the descending part. One hyperplastic polyp of the gastric type and one case of fibrosis were found. CONCLUSIONS: 1) Duodenal polyps are found in 4.6% of patients referred to upper endoscopy and should therefore be looked for. 2) Multiple, small polyps in the duodenal bulb are always benign and need neither biopsy nor treatment (in patients with familial polyposis biopsy is recommended). 3) In the descending duodenum polyps are rare, but a substantial number of them are adenomas. Biopsy is therefore mandatory in this localization.

Adenoma↗