Digital subtraction radiography for assessment of simulated root resorption cavities. Performance of conventional and reverse contrast modes

Abstract A previous study of the sensitivity and accuracy of a standardized radiographic technique for the disclosure of root cavities in a cadaver material indicated that it was not possible to perceive small artificial “resorption” cavities. Using the same material, the aim of the present study was to evaluate whether the use of subtraction radiography would improve the detection of root cavities. In an autopsy material of five mandibular blocks each containing two premolars, small, medium, and large cavities were drilled in the cervical, middle, and apical thirds of the proximal and oral root surfaces. Each jaw block was radiographed before (B) and after (A) cavity preparation with three different exposure times resulting in light, medium, and dark film densities. The radiographs were digitized. Digital subtraction was performed between the A- and B images of varying densities by a computer program developed for dental subtraction radiography. Conventional and reverse contrast modes of the subtraction image were assessed independently by four observers. The results showed small inter- and intraobserver differences in diagnostic accuracy for assessment of total number of root cavities. Original film density did not influence the diagnostic performance in the resulting subtraction image. Contrast mode in the subtraction image influenced diagnostic performance as the majority of observers did best with the reverse contrast mode (p<0.05). Some of the small root cavities were disclosed by the subtraction technique, but overall accuracy was not increased compared to conventional radiography.     

Radiographic control of fixture-abutment connection in Br?nemark implant technique

In the treatment with osseointegrated implants ad modum Br?nemark a radiographic control of the fixture-abutment connection is recommended. The purpose of the present study was to analyze the possibilities of detecting incomplete connection by radiography using the recommended technique. In an experimental model the influence of film density, orientation of the fixture hexagon, angulation between film plane and fixture axis, leakage width, and partial connection were analyzed. Slits of 0.05 mm were detectable under optimum projection conditions. On the other hand, slits of 0.1 mm were obscured even at deviations of 5 degrees. A number of factors, e.g. low density level and "unfavorable" orientation of the hexagon in relation to the X-ray beam, reduce the possibilities of detecting slits. It is concluded that in clinical cases a demonstration of incomplete fixture-abutment connection by the use of the recommended radiographic technique radiography to some extent is fortuitous, and that radiographic control has certain limitations.     

Estimation of angulation of Brånemark titanium fixtures from radiographic thread images

Identity of film positioning and of X-ray beam angulation is essential for valid comparisons of marginal bone height around osseointegrated implants. The purpose of the present study was to analyze the possibilities of estimating fixture angulation in relation to film plane from the threads of Brånemark fixtures. 10 observers compared 62 images of fixtures with angulations ranging from 0" to ± 15" with a set of reference radiographs. Out of 620 recordings, 29% were right, and 71% differed by ≥ 1". The observers distinguished with great accuracy between negative and positive angulations. 81% of the recordings differed by 2" or less. It is concluded that the threads of Brånemark fixtures are helpful in controlling the identity of serial radiographs of implants. The test circumstances were ideal compared to clinical cases, and it is possible that accuracy will be less in patient cases.     

Livedo racemosa als kutane Manifestation bei eosinophiler Granulomatose mit Polyangiitis

As a rare antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis, eosinophilic granulomatosis with polyangiitis (EGPA, formerly Churg-Strauss syndrome) is characterized by asthma, severe peripheral eosinophilia and the presence of extravascular granulomas. Cutaneous involvement usually includes palpable purpura or cutaneous to subcutaneous nodes. We present the case of a 43-year-old woman with EPGA and the unusual cutaneous manifestation of livedo racemosa.     

Binding of native and thrombin activated factor VIII to platelets

The interaction of human Factor VIII with platelets has been studied using discontinuous albumin gradient centrifugation. When purified Factor VIII complex was mixed with released platelets about 10% of the recovered Factor VIII activity became associated with the platelets. In the corresponding experiment with thrombin-activated Factor VIII about half of the Factor VIII activity was bound to the platelets. This binding was reversible; dilution of the platelet suspension containing bound Factor VIII resulted in dissociation of part of the Factor VIII activity. With non-released platelets very little binding of Factor VIII activity occurred. A mechanism for the in vivo formation of the Factor X activator complex is suggested.     

Annual number of intraoral radiographs in Denmark and other countries

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.     

Accuracy of radiographic diagnosis of peri‐implant radiolucencies -‐ an in vitro experiment

The absence of a peri‐implant radiolucency on radiographs is used as a criterion for implant success. The purpose of the present study was to evaluate the accuracy of diagnosing peri-implant radiolucencies using an experimental model. Astra Tech fixtures were inserted into 20 bony specimens. Later, the fixtures were removed and the prepared cavities were enlarged in 2 steps. The specimens were radiographed under strictly standardized circumstances in the 3 stages ("press‐fit"= simulated osseointegration, and "0.1 mm space" and "0.175 mm space"= simulated connective tissue layer". All specimens were radiographed with 2 vertical angulations (0" and 15"). Ten observers read the radiographs and evaluated bone‐implant relationship on a 5‐point scale. The interobserver agreement was low. Specificity was remarkably low, and sensitivity was moderate. A significant difference in diagnostic accuracy was found for 0.175 mm peri‐implant space compared to 0.1 mm space. The diagnostic accuracy was found to be highest for 0.175 mm peri‐implant space specimens. It is concluded, that radiography seems to be an unreliable method for diagnosing peri‐implant spaces, although accuracy improved at increasing space widths. Strict orthogonal projection angles did not improve diagnostic accuracy.     

Three-dimensional perception of radiographic images among dental students and dentists

Six radiographs exhibiting problems of three-dimensional perception were shown to seventy-six inexperienced dental students and to seventy-six experienced dentists. They were asked (1) from which viewing direction they perceived the image, (2) if they were able to reverse the image, and if not (3) if they denied the possibility of reversibility. In most cases a vast majority (83 to 93 percent) agreed in one perception. Twelve to 62 percent were unable to reverse the images. High percentages of the observers denied perceptions other than their own. No statistically significant differences were observed between the answers of the students and the dentists. The decisions of the observers and their restricted ability for ambiguous perception are discussed. Rules governing the choices of perception are suggested. The importance of training at undergraduate as well as postgraduate levels in perceiving radiographic images ambiguously and three-dimensionally is stressed.     

Fallbasiertes interaktives ?PACS-learning��

Purpose

Medical curricula are currently being reformed in order to establish superordinated learning objectives, including, e.g. diagnostic, therapeutic and preventive competences. This requires a shifting from traditional teaching methods towards interactive and case-based teaching concepts. Conceptions, initial experiences and student evaluations of a novel radiological course Co-operative Learning In Clinical Radiology (CLICR) are presented in this article.

Materials and methods

A novel radiological teaching course (CLICR course), which combines different innovative teaching elements, was established and integrated into the medical curriculum. Radiological case vignettes were created for three clinical teaching modules. By using a PC with PACS (Picture Archiving and Communication System) access, web-based databases and the CASUS platform, a problem-oriented, case-based and independent way of learning was supported as an adjunct to the well established radiological courses and lectures. Student evaluations of the novel CLICR course and the radiological block course were compared.

Results

Student evaluations of the novel CLICR course were significantly better compared to the conventional radiological block course. Of the participating students 52% gave the highest rating for the novel CLICR course concerning the endpoint overall satisfaction as compared to 3% of students for the conventional block course. The innovative interactive concept of the course and the opportunity to use a web-based database were favorably accepted by the students. Of the students 95% rated the novel course concept as a substantial gain for the medical curriculum and 95% also commented that interactive working with the PACS and a web-based database (82%) promoted learning and understanding.

Conclusion

Interactive, case-based teaching concepts such as the presented CLICR course are considered by both students and teachers as useful extensions to the radiological course program. These concepts fit well into competence-oriented curricula.