Biomedical subjects
W Bürgin
Publications and source records attributed to W Bürgin.
Diagnosis of alveolar bone changes with digital subtraction images and conventional radiographs. An in vitro study.
The purpose of the present study was to compare the diagnostic properties of radiographs obtained with Ultra-Speed and Ektaspeed films when analyzed conventionally radiographs and after conversion in digital subtraction images. Artificial lesions, measuring 0.5, 0.7, 0.9, and 1.1 mm in diameter, were drilled in a dry skull with slow-speed burs. Standardized radiographs were obtained by means of acrylic bite blocks and a modification of the Rinn system. The results of this study demonstrated that sensitivity in the detection of the lesions was doubled after digitizing and displaying subtraction images compared with the conventional radiographic interpretation, independent of the use of Ektaspeed or Ultra-Speed films for the original radiographs. The diagnostic information seemed to be equal in radiographs obtained from Ultra-Speed and Ektaspeed films after digitization and image processing procedures.
Digital subtraction radiography for the assessment of changes in peri-implant bone density.
Digital subtraction radiography is proposed as a potential diagnostic tool for implant research and patient monitoring. Examples of the application of this technique are given observing peri-implant density changes during the early healing phase and during ligature-induced peri-implantitis in an animal model. Additional cases document the loss of peri-implant bone density associated with an infection and increase in density caused by remodeling after functional loading of an implant with a single crown. Digital subtraction radiography might be one of the most sensitive noninvasive methods for assessing subtle density changes in peri-implant tissues, providing additional diagnostic information on implant tissue integration and maintenance.
Does the mandible alter its functional position during activator treatment?
The study aimed at revealing possible changes, in activator-free periods, in the positions and movements of the mandible induced by the wearing of an activator. Twenty-one children being treated with three different types of activator for the correction of Angle Class II, Division 1 malocclusion were studied. The movement capacity of the mandible, the rest position, and the position of tooth contact during chewing were recorded with a Sirognathograph before treatment and repeatedly during the first year of treatment. With the exception of a slight increase in the maximal protrusion, no changes in mandibular movement capacity were found. The anteroposterior position of the mandible in the rest position was constant during the period of treatment, but the freeway space increased. No changes in the position of the point of tooth contact during chewing were found. The study produced no evidence of a treatment-induced forward positioning of the mandible in activator-free periods.
[Malocclusions in Swiss recruits in 1985].
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Laboratory and intra-oral tests of the degradation of elastic chains.
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Long-term analysis of biologic and technical aspects of fixed partial dentures with cantilevers.
PURPOSE: The aim of the present clinical study was to analyze the long-term treatment outcome of fixed partial dentures (FPD) with cantilevers. MATERIALS AND METHODS: Ninety-two patients with 115 cantilever FPDs on 239 abutment teeth were examined. Immediately following cementation, radiographs of the abutment teeth were obtained. At the follow-up examination 5 to 16 years after cementation, the abutment teeth were clinically and radiographically evaluated. Besides the assessment of periodontal parameters and vitality testing, the presence of carious lesions of the abutment teeth, loss of retention, fracture of bridgework, and fracture of abutment teeth were also recorded. The Student's t test was used to detect differences between abutment teeth and control teeth with natural crowns as well as over time within the groups. RESULTS: Plaque scores and bleeding on probing were low at both abutment and nonabutment teeth. Mean probing pocket depth and level of the clinical attachment never exceeded 3.0 mm in both groups. The radiographic bone levels at abutments were stable within 3% over the observation period. Of the 120 initially vital abutment teeth, 12 (10%) lost vitality during the observation period; one (1%) of the 119 initially nonvital abutments showed periapical pathology. Development of secondary caries was observed at 8% of the 239 abutment teeth. In total, 8% of the abutment teeth were affected by loss of retention, which made up more than half of all technical problems. Material fractures only occurred occasionally, affecting from 1% to less than 3% of the abutment teeth. Fracture of abutment teeth amounted to 3% and was twice as frequent at abutments adjacent to cantilevers compared to abutments not adjacent to cantilevers. CONCLUSION: The most frequent biologic (caries) and technical complications (loss of retention) made up more than half of all problems recorded. These problems may be at least partially avoided by performing optimal plaque control and by strictly observing the rules for preparation of retentive FPD abutments.
Occlusal force and oral tactile sensibility measured in partially edentulous patients with ITI implants.
Maximal occlusal force and oral tactile sensibility were recorded in (1) a group of partially edentulous patients restored with ITI implants supporting fixed prostheses or single crowns and (2) a control group consisting of fully dentate subjects with healthy natural teeth. Maximal occlusal force was measured with a miniature force transducer placed between antagonistic implant/tooth pairs in the test group and antagonistic teeth in the control group. The detection threshold of minimal pressure (ie, passive tactile sensibility) was recorded with dynamometers, and minimal perceived thickness (active tactile sensibility) was assessed using steel foils with a thickness from 100 to 10 microns. Highest maximal occlusal force was measured in fully dentate subjects on second premolars (average 450 N). A significant reduction on the first premolars (300 N) was observed. With fixed prostheses supported by implants, the average value of maximal occlusal force was distinctly lower, about 200 N for first premolars and for molars, and 300 N for second molars. The maximum force was again found on second premolars. The detection threshold of minimal pressure was significantly higher on implants than on natural teeth. The average number of wrong assessments when testing steel foils was 3.2 for antagonistic implant/tooth pairs and 2.6 for natural teeth. The comparison of test sides (with implants) and control sides (without implants) in patients of the test group did not reveal significant differences of measurements. It seems that patterns of oral function depend primarily on the state of dentition, type of prosthodontic restorations, and on psychological aspects, and secondarily on the presence of implants.