Friedhelm Bollmann

Publications of Friedhelm Bollmann

• Three-dimensional quantification of color-marked occlusal paths on anatomically oriented casts

  Authors: Dieter Dirksen, Christoph Runte, Zoltán Böröcz, Carsten Thomas, Gert von Bally, Friedhelm Bollmann

  The Journal of Prosthetic Dentistry.

  Statement of problem. The analysis of occlusal contacts on mounted diagnostic casts is an important task in prosthetic diagnostics. However, it is still restricted mainly to qualitative aspectsStatement of problem. The analysis of occlusal contacts on mounted diagnostic casts is an important task in prosthetic diagnostics. However, it is still restricted mainly to qualitative aspects because existing measuring techniques fail to provide 3-dimensional data for more than a few single points in acceptable time. Purpose. The aim of this study was to develop a method for quantifying occlusal contacts and paths by using anatomically oriented diagnostic casts and to design the method to allow fast acquisition of digital 3-dimensional coordinates. Material and methods. Plaster casts with color-marked contacts were digitized optically with a profilometric system based on the fringe projection technique. Digital camera images taken simultaneously were used to define the contact areas by marking them either manually or automatically with the help of image-processing routines. Three-dimensional coordinates were determined by finding the corresponding points within the profilometric data set. Results. Color-marked contact areas on diagnostic casts were successfully digitized with a computer-controlled, automatic setup in approximately 30seconds. The accuracy of the acquired 3-dimensional data was estimated to be better than 60 μm in lateral and 30 μm in height resolution. The data set was visualized and evaluated in a skullrelated coordinate system. Summary. This study verified the use of a new tool to quantify color-marked occlusal contacts on diagnostic casts in terms of spatial coordinates. The resulting digital data may be stored easily and analyzed numerically as well as visualized 3-dimensionally with computer graphic equipment. Because the anatomic orientation of the casts is maintained throughout the measurement process, it is possible to compare the data with electronically registered condyle paths and therefore to investigate, for example, their relation to the corresponding guidance paths of the frontal teeth and the canines in dynamic occlusion. (J Prosthet Dent 2001;85:156-61.)

• Spectral analysis of /s/ sound with changing angulation of the maxillary central incisors.

  Authors: Christoph Runte, Djafar Tawana, Dieter Dirksen, Bettina Runte, Antoinette Lamprecht-Dinnesen, Friedhelm Bollmann, Eberhard Seifert, Gholamreza Danesh

  The International journal of prosthodontics. 15(3):254-8.

  PURPOSE: The aim of the study was to measure the influence of the maxillary central incisors free from adaptation phenomena using spectral analysis. MATERIALS AND METHODS: The maxillary dentures ofPURPOSE: The aim of the study was to measure the influence of the maxillary central incisors free from adaptation phenomena using spectral analysis. MATERIALS AND METHODS: The maxillary dentures of 18 subjects were duplicated. The central incisors were fixed in a pivoting appliance so that their position could be changed from labial to palatal direction. A mechanical push/pull cable enabled the incisor section to be handled extraorally. Connected to the control was a sound generator producing a sinus wave whose frequency was related to the central incisor angulation. This acoustic signal was recorded on one channel of a digital tape recorder. After calibration of the unit, the denture duplicate was inserted into the subject's mouth, and the signal of the /s/ sounds subsequently produced by the subject was recorded on the second channel during alteration of the inclination angle simultaneously with the generator signal. Spectral analysis was performed using a Kay Speech-Lab 4300B. RESULTS: Labial displacement in particular produced significant changes in spectral characteristics, with the lower boundary frequency of the /s/ sound being raised and the upper boundary frequency being reduced. CONCLUSION: Maxillary incisor position influences /s/ sound production. Displacement of the maxillary incisors must be considered a cause of immediate changes in /s/ sound distortion. Therefore, denture teeth should be placed in the original tooth position as accurately as possible. Our results also indicate that neuromuscular reactions are more important for initial speech sound distortions than are aerodynamic changes in the anterior speech sound-producing areas.

• Optical data acquisition for computer-assisted design of facial prostheses.

  Authors: Christoph Runte, Dieter Dirksen, Holger Deleré, Carsten Thomas, Bettina Runte, Ulrich Meyer, Gert von Bally, Friedhelm Bollmann

  The International journal of prosthodontics. 15(2):129-32.

  PURPOSE: The conventional impression technique for manufacturing facial prostheses has the disadvantage of deforming the soft tissues because of the tension caused by the impression material, as wellPURPOSE: The conventional impression technique for manufacturing facial prostheses has the disadvantage of deforming the soft tissues because of the tension caused by the impression material, as well as causing discomfort to the patient. The purpose of this study was to establish a system that allows contact-free reproduction of the facial surface combined with computer-assisted design and fabrication of facial prostheses. MATERIALS AND METHODS: Three-dimensional data of the facial surface were obtained using an optical acquisition system based on the method of phase-measuring profilometry. A sensor head with a fringe projector and two CCD cameras for photogrammetric triangulation were used in connection with a PC for measurement control and data evaluation. Software for computer-assisted design of the facial surface to be reconstructed was developed. A prototype facial prosthesis was fabricated using stereolithography. The system was tested using a modified puppet head. First clinical tests were performed with a patient who had undergone maxillofacial surgery including the resection of one eye. RESULTS: Three-dimensional data acquisition and imaging allow visualization of a whole face without causing tension or neuromuscular reaction. As surface brightness is also part of the digital model, it is even more realistic than a plaster cast. The stereolithographic object showed good marginal fit and satisfactory shape. CONCLUSION: The presented technique allows three-dimensional data reproduction of the facial surface, computer-assisted design of a facial prosthesis, and transfer to a rapid prototyping unit. The system has obvious advantages over conventional impression techniques. Further clinical trials are planned to evaluate the clinical success of the technique.