Biomedical subjects
Publications and source records attributed to I Sewerin.
The use of Kodak Duplicating Dental films for production of intraoral dental x-ray film copies represents an alternative to a constant use of double film packages. The technique which is very simple is described, and economic considerations are discussed.
Radiography is an essential tool in treatment of the edentulous jaw with osseointegrated implants. Radiographic examinations are made 1) preoperatively in treatment planning, 2) as intermediate controls during surgical and prosthetic procedures, and 3) postoperatively in longitudinal control. In the present paper the purposes of the different examinations are summarized, and the radiographic techniques used by the Department of Radiology, Royal Dental College, Copenhagen, in treatment with titanium implants a.m. Brånemark are described. Panoramic rotational radiography, cephaloradiography, intraoral projections, and tomography are used at different stages and for different purposes. The superiority of the tomographic technique for depiction of cross-sectional images of the alveolar ridge is emphasized. The problems of interpreting tomograms are explained, and the wide variability in the anatomy of the osseous alveolar ridge is demonstrated.
A previous paper summarized preoperative radiographic examinations, and the present paper is dealing with intermediate examinations following abutment operation as well as longitudinal examinations subsequent to prosthetic restoration. The difficulties in detecting incomplete fixture-abutment connection, and the need for identity of periodical radiographs are discussed. The operator is faced with great problems of film placement and projection angles when radiographing fixtures embedded in jaw bone. The main purposes of longitudinal examinations are to control marginal bone level changes and perifixtural bone quality. Radiography is also essential in diagnosing complications, e.g. loss of osseointegration and fixture fractures.
A survey was made of the total number of extraoral and intraoral exposures performed during the preoperative, intermediate and control phases in treatment of patients with osseointegrated implants ad modum Brånemark according to the routine procedures used at the Department of Radiology, Royal Dental College, Copenhagen. Dose values from literature were used for calculation of total effective dose equivalent. The sum of examinations comprised 16 extraoral and 231 intraoral films for a patient treated with 6 maxillary and 6 mandibular implants. The total dose over a 7-year-period amounted to approximately 1.7 mSv (0.25 mSv per year). Considering that the natural radiation in Denmark results in an annual dose of 3 mSv per inhabitant and many medical radiographic examinations result in effective dose equivalents of 3-6 mSv, the dose following the treatment with implants appear to be of a moderate magnitude. The increased scattering due to the metallic implants does not seem of deleterious significance.
Studies of energy imparted (mJ) and effective dose equivalents (mu Sv) following rotational panoramic radiography and intraoral full mouth surveys from the past 10 years are reviewed (Tables 1 and 2). Energy and dose values are compared. Factors influencing energy imparted and effective dose equivalents are discussed (measuring techniques, calculation principles, generator, kilovoltage, filtration and half-value layer, irradiated field, collimation, intensifying screens, film sensitivity, focus to object distance, sex and age of patients, inaccurate technical specifications, individual x-ray unit characteristics). In general it is concluded that one panoramic examination means less energy imparted to the patient and a lower effective dose equivalent than an intraoral full mouth survey. However, a number af factors are of influence, and the change of a single factor may have a dramatic effect and reverse the situation. When comparing individual cases all factors of known influence must be considered and general conclusions cannot be applicated without reservations.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The CEJ on radiographs is often used as a reference point in the assessment of alveolar bone loss. The aim of the present study was to test the stability of the radiographic CEJ ("RCEJ") in relation to the alveolar crest under varying angulations of the central X-ray beam. In an experimental model four types of extracted teeth were radiographed at 0 degree and 20 degrees vertical angulation and at 15 horizontal angulations varying from a 17.5 degrees mesial view to a 17.5 degrees distal view. The buccal alveolar bone margin was simulated by a steel needle. RCEJ-"crest" distances were read at a X 10 magnification. Changing the vertical angulation from 0 degree to 20 degrees reduced the RCEJ-"crest" distances for all tooth types (range of average reduction 2.2-4.1 mm). Horizontal angulations without concomitant vertical angulation had a significant effect but were without clinical significance. Horizontal angulations in combination with a 20 degrees vertical angulation had a considerable influence; in a mesial view, mesial RCEJ-"crest" distances decreased and distal ones increased, and vice versa in a distal view. The deviations from the true CEJ-crest distance demonstrated may be of clinical significance, and a critical attitude to alveolar bone loss measures on radiographs using the RCEJ as reference point is recommended.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
A number of technical and methodologic factors govern the quality of the radiographic image. The purpose of the present paper is to analyze the attention paid to these factors in epidemiologic studies and clinical trials. The description of radiographic methods in a sample of scientific reports was reviewed. It is concluded that the descriptions are generally sparse. They seem to be of an erratic character, and the data described are not selected according to their significance. Factors governing object coverage, image density and contrast, image geometry, and readability are discussed in relation to the descriptions analyzed. Recommendations for relevant and informative descriptions enabling the reader to evaluate and control the results of an investigation are presented.
It has been demonstrated previously that in 1982, 2.4 million intraoral radiographs were taken in Denmark, or 0.47 radiograph per inhabitant. In the present study this frequency is compared to frequencies in other countries. The number of radiographs per inhabitant varied between 1.6 (Sweden) and 0.08 (Hungary). It is concluded that the frequency in Denmark is lower than in Sweden, USA, Norway, and Japan, but higher than in Great Britain, Finland, and Hungary. The increase in use of intraoral radiography was compared for five countries. The frequency curves exhibited nearly identical slopes, but the rates of increase for Great Britain and Denmark were approximately 15 yr delayed in comparison with Sweden, USA, and Japan.
The absorbed doses in the body of a Rando-Alderson phantom were measured in rotational panoramic radiography (OP-5) with LiF-700 crystals using conventional intensifying screens and standard collimator, as well as rare earth intensifying screens and a collimator slit of reduced width. The reduction of the absorbed doses obtained by using the latter combination was calculated. The reduction range in different regions was 0-50%. The greatest reduction was obtained in the cranial part of the phantom. In the caudal part little or no reduction was observed, probably because leakage radiation contributes substantially to the absorbed doses in this area. The average dose equivalent was calculated for organs in which measurements were made in several locations. The reduction was about 50% for these organs except for the gonads (8%). Compared to the estimated average annual dose equivalent originating from the natural background radiation sources, the dose equivalent resulting from this X-ray examination was very small except in the thyroid gland. In this organ the dose equivalent from one exposure corresponded to 36 days of natural background radiation, but it could be reduced to 18 days by using rare earth intensifying screens in combination with reduced beam width.
Explore the source record for details and available documents.
Explore the source record for details and available documents.