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Biomedical subjects

I Sewerin

Publications and source records attributed to I Sewerin.

At least 19 recordsLinked to original sources
PubMed1992

Identification of dental implants on radiographs.

In the future, dentists will more frequently encounter patients who have dental implants. To use radiographs to identify implants that were previously inserted by other dentists, dentists have to be familiar with the detailed morphology of different products and types of fixtures as well as with the principles for formation of their radiographic images. In the present study, radiographic images of ten common dental implants were analyzed. Images varied with viewing angles. The influences of surface structures, such as threads, cuts, holes, perforations, and flutes, are demonstrated.

Dental Implants↗
PubMed1992

[A comparison of two methods for pre-operative radiographic examination in treatment with oral implants in the anterior mandibular area].

Insertion of osseointegrated implants in the anterior mandibular region for retaining a removable denture represents a treatment, which is cheap for the patient and surgically uncomplicated. Bone height measures from two radiographic examinations 1) panoramic radiographs and 2) lateral tangential views, were compared. Radiographs from 20 patients were analyzed. The vertical height of the mandible was measured in the midline as well as in the cuspid region on the panoramic radiographs and the tangential views ("maximum" bone heights). The mean maximum bone heights were higher on tangential views in both regions. On the tangential views the inclinations of the future implants were estimated and the part of the alveolar ridge having a width less than 5 mm, which is the minimum width for housing an implant, was compiled. The resulting height ("effective bone height") was calculated. In 10% of the cases the effective bone height was equal to the maximum height, and in 90% it was smaller. The over-estimation varied between 0 mm and 15.3 mm. It is concluded that panoramic radiographs are unreliable for evaluating bone height in planning insertion of oral implants in the anterior mandibular region. They give no information about form and width of the bone. Tangential views reveal the true morphology of the mandible as seen in a cross-section, and offer an opportunity for calculating the effective bone height at disposal for oral implants.

Dental Implantation, Endosseous↗
PubMed1992

Radiographic image characteristics of Brånemark titanium fixtures.

In the interpretation of radiographs showing oral implants a thorough knowledge of their radiographic image is essential. The purpose of the present study was to describe the radiographic image of the Brånemark titanium standard fixture, and to analyze the influence of rotation of fixture in the jawbone as well as angulation of central X-ray beam in relation to longitudinal fixture axis. Especially the influence upon the radiographic image of the thread system, the apical cylindrical perforation, and the four apical vertical cuts is considered.

Dental Implantation, Endosseous↗
PubMed1991

Sources of noise in digital subtraction radiography.

In 17 patients, three identical radiographic examinations were performed for the lower premolar-molar region, by two examiners at one visit and by one examiner again approximately 3 months later. Recordings were performed with a newly developed device. The radiographs were converted to digital images in the following way: (1) video camera recording of the radiograph obtained at first visit by the first examiner (A), (2) copying of the numeric image of this radiograph (B), (3) repeated video recording of this radiograph (C), (4) video recording of the radiograph obtained at first visit by the second examiner (D), and (5) video recording of the radiograph obtained after 3 months (E). Subtractions were performed between the images: B - A, C - A, D - A, and E - A. The standard deviation of the histogram for the distribution of gray shades in the subtraction images was used to evaluate noise in the image. The standard deviation was 1.3 between B - A, 2.8 between C - A, 4.0 between D - A, and 4.1 between E - A. Physical noise originating from the video camera and the analog-to-digital conversion process thus constituted the major part of noise seen in subtraction images performed between radiographs recorded with a time interval. This indicates that reproducible recordings could be performed with the present device, which, in combination with a subtraction program able to correct for some geometry and density differences, may aid the use of subtraction radiography in clinical trials.

Adolescent↗
PubMed1991

Performance for obtaining maximal gain from a program for digital subtraction radiography.

The aim of this study was to evaluate the effect on subtraction image quality of number of a) gray shades sampled during camera recording, and b) reference points positioned in the two images to be subtracted. Intraoral radiographs were obtained in each of 12 patients, one at 0 degrees and one at 15 degrees horizontal angulation in a standardized recording procedure. The radiographs were videorecorded twice sampling 1) 160-180 and 2) 200-220 shades of gray. The 0 degrees radiographic image was digitally copied. Subtractions were performed between the identical (0 degrees/0 degrees) and the non-identical (0 degrees/15 degrees) radiographs from both gray shade samples after positioning 5, 10, 15, and 20 reference points, respectively, in each of the images to be subtracted. The standard deviation in the subtraction image histogram was used as the test parameter for image quality. No differences existed between image quality obtained from the radiographs sampled using 160-180 and 200-220 shades of gray (P greater than 0.05). The standard deviation fell continuously, the more reference points were positioned in the images. For the 0 degrees/0 degrees images the difference was statistically significant between the 5 and 10 point images (P = 0.045) while for the 0 degrees/15 degrees images differences existed between 5 and 10 point images (P = 0.077) and the 10 and 15 point images (P = 0.048). The precision of reference point positioning as evaluated in the two identical images was satisfactory, the divergence being on average 1.4 pixels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Leaded screens for protection of the body against scattered radiation in intraoral radiography].

The use of a protective leaded shield as an alternative to leaded aprons and leaded neck collars for reduction of body doses originating from scattered radiation in intraoral radiography is discussed. The shield is stiff and has a U-shaped form fitting the neck of the patients and is kept in position by the patient himself. During exposure the shield is pressed against the patient's neck and kept in close contact with the inferior border of the mandible in a horizontal position. Three products of shields are described, all having lead equivalents of 0.5 mm. The protection of the thyroid gland is of maximum efficiency. Measurements of absorbed doses have shown the shield to have a protective effect equal to leaded aprons in cranial body regions, while gonadal doses are a little higher. Upper extremities are always protected by a shield, while many patients keep their hands and arms upon and not under an apron. Shields are easy to handle for the staff, hygienic, and cheaper than an apron. They can hardly be damaged and leaks following handling will not occur as for aprons. Leaded shields have recently been accepted as alternative to leaded aprons by the Danish National Institute of Radiation Hygiene.

Adolescent↗
PubMed1991

[Tangential projection for depiction of the anterior regions of the jaws performed with the dental X-ray set].

The tangential projection represents an extraoral projection which with success can be performed with the dental X-ray set. The film is placed lateral to the angle of the mouth in a vertical position level with either the maxilla or the mandible. If a view of the midline is wanted the film is placed parallel with the sagittal plane; if e.g. the canine region is of interest the film is angulated. The central X-ray is directed horizontally and perpendicularly to the film passing (as a tangent) the anterior surface of either the maxilla or mandible. The beam area used for periapical projections is ideal also for this projection. The tangential projection is indicated as a supplemental projection for three-dimensional localization of e.g. supernumerary teeth in the maxillary anterior region and for the buccolingual position of an impacted canine. It is also very useful in combination with frontal projections in the planning of insertion of dental implants. According to the Danish legislation it is not allowed to use the dental X-ray set for extraoral projections unless intensifying screens are used. However, the Danish Institute of Radiation Hygiene has accepted tangential projections using dental X-ray films and omitting intensifying screens in edentulous patients due to their better resolution, which is of particular importance in the planning of implant insertion.

Humans↗
PubMed1991

[Depiction of oral implants on radiographs].

An enormous number of products and types of oral implants exists. In identification of implants previously inserted by other dentists radiography is essential. The radiographic images of 14 fixtures were analyzed and explained based on experimental exposures under standardized circumstances. In particular was the influence of different viewing angles due to rotational position of the fixture described. It is concluded that any of the metallic fixtures studied possesses macrostructures which will lead to a unique radiographic image making it possible to recognize it on radiographs. On the other hand the images will vary widely depending on rotational stage of the fixture why a thorough knowledge of the detailed architecture of the implants is necessary.

Dental Implants↗
PubMed1990

[Unusual ghost-images on rotational panoramic radiographs: five cases].

In continuation of a previous paper on the principles in formation of "ghost images" on rotational panoramic radiographs five unusual and illustrative cases are presented. They demonstrate the influence of the position of the true object in relation to that of the rotation center. The dimensions of the ghost image inform of the distance between the center and the true structure. If the height is uniform it means that the true object is the seat of the rotation center. A ghost image may appear narrower or broader than the true structure, if its dimensions differ in various viewing angles.

Adult↗
PubMed1990

[Lead foil artifacts as a result of unintentional bending of dental X-ray films].

The lead foil of dental x-ray film packets may cause a number of artifacts; especially well known are the "tractor treads" and "herringbone patterns" following a backward filmpositioning in the patient's mouth. In the present paper a specific and seldomly occurring lead foil artifact is described which is caused by bending of the film packet. Four cases collected over a 5-year period are presented. Although different the four cases show a number of similarities. They appear as radiopaque areas covering the upper or lower halves of the films. Their borders show the characteristic "sandbar-pattern" previously described by the author. The explanation of their origin is that the patient has been occluding on a part of the film packet which has been bent to a nearly horizontal position. The x-rays directed against the edge of the lead foil will be absorbed causing irregular radiopaque areas on the film lined by "sandbar-pattern". When the film packet is bent, the lead foil will be stretched and drawn a little away from the edges of the films. Consequently the x-rays will be able to expose the edges of the films. Irregularities of the foil will give rise to concentric "bars". The lead foil is only of limited radiopacity, but due to the oblique direction of the x-rays through the foil the absorbing effect is intensified.

Diagnostic Errors↗
PubMed1990

A radiographic four-year follow-up study of asymptomatic mandibular third molars in young adults.

Fifty-five asymptomatic mandibular third molars (M3) in 34 dental students (mean age 20.6 years at the start of the study) were followed radiographically for 4 years. Based on clinical evaluation the 55 teeth included 20 almost erupted, 13 partly erupted and 22 non-erupted M3. The following were assessed on the radiographs: root development, level of eruption, sagittal angulation, resorption, pericoronitis/bony pockets/paradental cysts and widening of the periodontal space/dentigerous cysts. The state of 21 teeth (38 per cent) was radiographically changed at the end of the observation period. The most remarkable finding was that 15 teeth changed their sagittal angulation, all in a distal direction; five mesioangular to vertical, five vertical to distoangular, five mesioangular to distoangular. Radiographically, 13 M3 moved to a more advanced level of eruption. No real pathological osseous lesions and no root resorption were observed at initial or follow-up examinations. It is concluded that there are frequent essentially unpredictable changes in the position of M3 after the age of 19 years which may influence decisions on their removal or preservation.

Adult↗
PubMed1990

[Patients' acceptance of poly-soft and paper-pack X-ray film packets].

Two types of Kodak dental x-ray film packets are manufactured, paper-pack (PP) from paper, and poly-soft (PS) from vinyl. They differ in dimensions as PP measures 31.4 X 42.1 mm compared to PS measuring 33.0 x 44.3 mm. The edges of PP are rounded, while those of PS have welded, thin and sharp edges. Patients acceptance of the two types was tested among 25 adult patients during exposures for full mouth surveys. For each patient half PP and PS were used in a random sequence. The patients were asked to rate any feeling of discomfort or pain and to compare the feeling after each pair of film packets. The scores were compared by Wilcoxon's matched-pairs signed-ranks test. The results revealed with a statistical significance at the 1% level, that the patients felt more discomfort when the poly-soft packet was used. No affections of image quality were noticed. In spite of the higher level of discomfort resulting from the use of PS it seems justified to recommend this type due to its superior hygienic qualities.

Humans↗
PubMed1990

[Ghost images in rotational panoramic radiography].

Ghost images are defined as images representing structures in the object located between the x-ray source and the rotation center. Their origin may be anatomic structures as well as foreign objects. A survey is given of the principles for the appearance of ghost images, their possible combinations with real and double images, and factors governing their position and occurrence.

Humans↗
PubMed1989

[An easy and inexpensive method for copying intraoral radiographs].

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.

Copying Processes↗
PubMed1989

[Preoperative radiographic examinations for edentulous jaws with osseointegrated implants].

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.

Dental Implantation, Endosseous↗
PubMed1989

[Intermediate and longitudinal radiographic examinations of edentulous jaws with osseointegrated implants].

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.

Bone Resorption↗
PubMed1989

[Effective dose equivalent following radiographic examination of edentulous patient treated by osseointegrated implants].

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.

Dental Implantation, Endosseous↗