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Biomedical subjects

A Wenzel

Publications and source records attributed to A Wenzel.

At least 109 records · Page 6Linked to original sources
PubMed1989

Changes in condyle position after bilateral vertical ramus osteotomy with and without osteosynthesis.

The purpose of the present study was to elucidate the importance of ramal osteosynthesis and evaluate postoperative condylar movements. The right temporomandibular joints of 53 patients with mandibular prognathism were examined by linear tomography the day before, 1 week after, and 1 year after surgery. During surgery the patients were randomly allocated to two groups: one with (n = 26) and one without (n = 27) osteosynthesis. It was found that osteosynthesis did not influence condyle position (p greater than 0.3). The two groups were thereafter pooled. Radiographic measurements of the posterior and anterior interarticular space revealed that condyle position 1 week postoperatively was forward and downward in relation to the preoperative position (posterior fossa, p less than 0.001; anterior fossa, p less than 0.01). One year later the condyle position demonstrated a tendency to approximate the preoperative position, especially with respect to the posterior part, but there was still a significant (p less than 0.01) difference when related to the original position. In conclusion, osteosynthesis after ramus osteotomy seems to be of no importance when healing and postoperative condyle position are considered. Furthermore, 1 year after surgery the condyles were not reestablished in their preoperative positions.

Adolescent↗
PubMed1989

Relationships of changes in craniofacial morphology, head posture, and nasopharyngeal airway size following mandibular osteotomy.

The aim of the present study was to illustrate a possible relationship between changes in craniofacial morphology after mandibular osteotomy and changes in head posture and nasopharyngeal airway size. The material comprised standardized profile cephalograms of 52 patients with mandibular prognathism, all of whom underwent orthodontic adjustment before mandibular osteotomy. Mean age of the patients was 24.3 years; 12 men and 40 women participated in the study. The first profile radiograph of each patient was taken 1 day before surgical treatment in the natural head (mirror) position. All patients underwent mandibular surgery with a bilateral vertical ramus osteotomy. The cephalometric investigation was repeated approximately 1 year after the surgical procedure (means = 1.12 years). Craniofacial morphology was evaluated by 12 parameters describing sagittal and vertical jaw relationship. Head posture was evaluated by the craniocervical angulation and airway as nasopharyngeal airway size. Pearson's correlation analysis was used to evaluate the relationship between morphology, posture, and airway size before surgery and changes in these parameters after surgery. Before surgical treatment statistically significant correlations were found between posture and many morphologic variables, mostly mandibular. Small correlations were observed between posture and airway size, and airway size and morphology. After the surgical procedure, changes in posture were still related to changes in mandibular morphology, while other correlations between posture and morphology had been eliminated. Changes in nasopharyngeal airway size were not correlated to any changes in morphology, apart from maxillary prognathism, nor to changes in posture. The results indicated that mandibular morphology and function play a significant role in determining head posture.

Adolescent↗
PubMed1989

Changes in head posture and nasopharyngeal airway following surgical correction of mandibular prognathism.

It was the aim of the present study to cast light on the role of the mandible in relation to head posture and airway space by evaluating patients before and after surgical correction of mandibular prognathism. The material comprised standardized profile cephalograms of 52 patients with mandibular prognathism. All patients had received orthodontic adjustments prior to mandibular osteotomy. Mean age of the patients was 24.3 years, and 12 males and 40 females participated in the study. The first profile radiograph of each patient was obtained the day before surgery in the natural head (mirror) position. All patients underwent mandibular surgery with a bilateral vertical ramus osteotomy. Approximately one year after surgery, the cephalometric investigation was repeated. Head posture was evaluated by the craniocervical angulation (NSL/CVT and NSL/OPT) and airway space as nasopharyngeal airway size (ad1 and ad2). Changes in posture and airway (ex.2-ex.1) were evaluated by paired t-tests. The results showed a mean increase in head posture of 2.7 degrees (p less than 0.001) and a mean reduction in airway space of 2.3 mm (p less than 0.001).

Adolescent↗
PubMed1989

Panoramic screening for dental anomalies assessed by professionals with identical and different backgrounds.

The aim of the present study was to evaluate how dental professionals with identical and different backgrounds assess dental anomalies viewed on panoramic radiographs. 101 panoramic radiographs performed of 9-to-10-yr-old children were examined independently by three orthodontists and two radiologists. All observers agreed on the recording of number and identification of congenitally missing permanent teeth. The observers' assessments of malpositioned teeth, teeth in infraocclusion, and primary teeth with atypical/non root resorption varied, however, to a great extent. Two of the orthodontists seemed to report only major deviations from normality (in 38 and 51 of the children respectively) while one reported several more findings (in 85 children). The radiologists reported abnormal findings in 80 and 88 children respectively. In only three children were no dental anomalies reported by any observer. The inconsistent reporting of the majority of dental anomalies (except for agenesis) in children, even among members of subgroups with a similar educational background (e.g. orthodontists), substantiates the need for an evaluation of the expedience of panoramic screening.

Anodontia↗
PubMed1989

Effect of manual compared with reference point superimposition on image quality in digital subtraction radiography.

The aim of this study was to compare a new subtraction program based on positioning of reference points (RP) in the two images with the classic manual (M) superimposition of the images during recording. The experiments were performed on 22 dry mandibles from domestic pigs. A bone chip was prepared from the cortex with seven edges: 0.26, 0.30, 0.36, 0.42, 0.49, 0.55 and 0.72 mm thick respectively. Each mandible was radiographed at 0 degrees vertical angulation without the bone chip. The bone chip was then fixed to the lingual plate for a series of radiographs during which the vertical angulation was varied from 0 degrees to 10 degrees at 1 degree intervals. After completion of this series of exposures, amalgam fillings were placed in the two molars on the right side and a second series obtained. The radiographs were digitized (512 x 512 x 8 bit resolution), stored in a personal computer and then subtracted in a random order by the two methods. The RP method was found to be superior to the M method for all the angulations evaluated; as the images were more homogeneous as shown by the smaller SD in the grey-scale histogram. The best results were obtained on images with amalgam-filled teeth. Significantly more bone edges were seen with the RP method, especially when amalgam fillings were present. The RP method may therefore be superior to the M in clinical trials using subtraction radiography.

Animals↗
PubMed1989

Sialic acid, galactose and fucose on the surface of Ehrlich ascites tumor cells grown in glucose-free medium in the presence of uridine.

1) The content and accessibility of terminal sialic acid and galactose residues as well as the incorporation of [3H]fucose into glycoconjugates were determined in 48-h cultures of Ehrlich ascites tumor cells in a glucose-free medium supplemented with uridine, a compound which can fulfil the necessary functions of glucose. 2) Sialic-acid residues accessible to sialidase cleavage were reduced from 695 +/- 80 nmol/10(9) cells (controls) to 284 +/- 22 nmol/10(9) cells (43% of controls). In situ labeling using periodate oxidation followed by sodium borotritiide reduction revealed a tritium incorporation of 47 +/- 11% that of controls (= 4.1 x 10(5) cpm/mg protein). 3) Labeling of galactose residues of 80-90% of that of controls was achieved after treatment of the cells with galactose oxidase/sodium borotritiide. A nearly six-fold enhancement of tritium incorporation into galactose of control cells was observed after sialidase/galactose oxidase treatment and sodium borotritiide reduction (1.5----8.8 x 10(5) cpm/mg protein); only a 3.6-fold increase (1.2 x 10(5)----4.3 x 10(5) cpm/mg protein) was found with glucose-free cultured cells. It is concluded that the galactose content of the cell surface is reduced to about 50% of controls. 4) The incorporation of tritium into acid-insoluble precipitate after 24 h incubation with [3H]fucose and the activity of the acid-soluble fraction were enhanced by about 85% as compared to controls. The pattern of inhibition by tunicamycin of [3H]fucose uptake and incorporation was the same in glucose-containing standard medium and in glucose-free uridine medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Effect of image enhancement for detectability of bone lesions in digitized intraoral radiographs.

Digital image enhancement is concerned with the computer-controlled manipulation of image information. The aim of this study was to evaluate whether diagnostic accuracy would improve in digitally enhanced images of radiographs with impaired density. Each of 83 dry mandibles was divided into four regions. By random assignment it was decided for each region whether or not a hole should be drilled. Three intraoral radiographs (3 x 4 cm) were performed of each region at different exposure times: 2.0 s, 0.60 s, and 0.16 s and interpreted. The radiographs were thereafter recorded by a video camera connected to an IBM-PC. The personal computer held a hardware digitization card defined at a 512 x 512 x 8 matrix resolution on the basis of which a software program with image enhancement facilities was developed. The light and dark radiographs were digitally enhanced by the use of contrast stretching and smoothing filters. The light (0.16 s) original radiographs were less accurate than the ones with optimal density (0.60 s) while no significant differences were found between dark (2.0 s) and optimal density original radiographs. No significant differences were found between original and digitized radiographs of optimal density and digitally enhanced images of light or dark radiographs. The diagnostic accuracy obtained from optimal density radiographs can thus be maintained in digitized dark radiographs and in light radiographs with a four-times dose reduction after digital image enhancement.

Animals↗
PubMed1988

Tumorigenicity of SEWA murine cells correlates with degree of c-myc amplification.

Previous studies have shown that cells of the SEWA mouse tumor contain amplified copies of the proto-oncogene c-myc in the aberrant chromosomal structures of double minutes (DMs), homogeneously staining regions (HSRs) and C-bandless chromosomes (CMs). DMs, and to a lesser degree CMs, tend to disappear from the cells grown in vitro and again reappear after transfer back in vivo, as if DNA amplification confers a growth advantage upon the tumor cells. We have now isolated five in vitro clones that exhibit different degrees of c-myc amplification. When we inoculated cells of the different clones into compatible hosts, we found that there was a positive correlation between degree of c-myc amplification, level of c-myc RNA, and tumorigenicity. Our results lend further support to the idea that gene amplification contributes to the higher malignant phenotype, and to progression of tumors.

Animals↗
PubMed1987

Cytokinetic studies on the switch from glucose to uridine metabolism, and vice versa, of Ehrlich ascites tumour cells in vitro.

Glucose is normally required as the energy source and for the proliferation of neoplastic cells. For Ehrlich ascites tumour cells, kept under glucose-free culture conditions, this requirement was alleviated by uridine, indicating that the supply of ribose is obligatory for sustaining growth capacity. In a 96-hr culture experiment with mouse-derived cells, the increase in cell number from cultures supplemented with 5 mM uridine was 50-70%, whilst lactate production was 5% that of controls. An increase in the number of multinucleate cells was observed from cell-smears; DNA histograms indicated the presence of cells with a DNA content higher than 4c and an increased portion of cells in G2 phase. For precise determination of changes in cell cycle distribution on transfer of cells from glucose-supplemented to glucose-free conditions, the progression of phase-accumulated cells (by centrifugal elutriation) was monitored by DNA distribution analysis; G2 cells continued the cycle at a rate comparable to controls but were delayed, in the following cycle, predominantly in S and G2 phases. This was also observed with G1 cells from a G1-accumulated fraction in the first cycle. The addition of glucose to cells kept for some hours in glucose-free, uridine-supplemented medium resulted in an immediate increase in mitotic index (amplification by the colcemid method). The results are interpreted and support our concept that the delivery of compounds, necessary for normal growth, i.e. hexoses for glycoproteins and glycolipids, are limited as a consequence of the 'metabolic channelling' of pentose from uridine in Ehrlich ascites tumour cells. Therefore, the constantly lowered growth-rate in uridine-supplemented cells observed with long-term culture experiments could reflect an adaptation of growth-cycle to these limitations.

Animals↗
PubMed1987

Effect of varying gray-scale resolution for detectability of bone lesions in intraoral radiographs digitized for teletransmission.

Visual communication equipments were developed early by radiologists for the transmission of analog signals, whereas today's transmission systems are based on digitization of the radiograph. For teletransmission of dental radiographs, it is essential to assess the diagnostic accuracy of various spatial and gray-scale resolutions. Each of 83 dry mandibles was divided into four regions. By random assignment it was decided for each region whether or not a hole should be drilled. Intraoral radiographs (3 x 4 cm) were performed of each region and interpreted. The radiographs were thereafter recorded by a video camera connected to an IBM-PC. The personal computer held a hardware digitization card defined at a 512 x 512 spatial resolution with the possibility of selecting varying gray-scale resolutions. All radiographs were assessed in resolutions with 256 (8 bit), 128 (7 bit), 64 (6 bit), and 32 (5 bit) shades of gray. In no case was the original radiograph more accurate than the 512 x 512 x 8 resolution. In two of the regions evaluated, the images providing 32 shades of gray were less accurate (percentage of true positives and negatives) than the other resolutions (P less than 0.05) while in one region resolutions of 8 bit depth (256 shades of gray) provided a significantly greater accuracy than did the original radiograph and the other image resolutions (P less than 0.05). This was due to fewer false negative scores and was not followed by an increase in false positive scores. It can be concluded that a 512 x 512 spatial resolution is satisfactory for the detection of bone lesions in digitized intraoral radiographs and that 64 shades of gray provide an equally good diagnostic accuracy as do the original radiograph. This might be relevant when transmission times are of importance.

Animals↗