PubMed Health⌕ Search

Biomedical subjects

F Bollmann

Publications and source records attributed to F Bollmann.

At least 19 recordsLinked to original sources
PubMed2004

[Investigation of influencing variables on the computer-aided simulation of contacts in dynamic occlusion based on optically digitized plaster casts].

In dentistry, mechanical articulators with which mandibular movements can be reproduced in dentals casts play a major role. Commonly used semiadjustable articulators, however, have major limitations: On the one hand, the movement of the mandible is not reproduced exactly, on the other, they do not provide time-related information on jaw movement. Both problems can be solved by replacing the mechanical articulator by a digital simulation ("virtual articulator") based on digitized plaster casts and electronically recorded masticatory movements. We present a system for the 3D measurement of plaster casts in a skull-related, anatomical coordinate system using the fringe projection technique, and electronically recorded condylar movements. Using numerical algorithms, the contacts between upper and low jaw, and the angle of rotation of the temporomandibular joint can be computed for each movement in dynamic occlusion. Taking the data recorded from a patient as an example, the influence of the accuracy of the digitization of plaster casts on the computation of the rotation of the temporomandibular joint is discussed in relation to the anatomy of the masticatory apparatus.

Computer Simulation↗
PubMed2002

[Computer-assisted development of epitheses after optical recording of facial defects].

A major drawback of conventional impression techniques used for customizing facial prostheses is the fact that pressure applied deforms soft tissue, thus reducing accuracy and causing patient discomfort. A possible solution is the use of optical 3-D coordinate measuring techniques, such as the fringe projection technique, which enables precise and contact-free recording of facial surfaces. The application of this method is demonstrated on a patient who lost his left eye and part of the jaw bone during surgery for cancer. 3-D CAD software that supports the construction of a facial prosthesis from the data obtained has been developed. For this purpose, spline functions are used to define border curves, and the intact half of the face is used as a model for the prosthetic surface. The resulting digital data are used to construct first a model made of synthetic resin, and then a final wax model with the aid of rapid prototyping techniques.

Computer-Aided Design↗
PubMed2001

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

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 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 30 seconds. The accuracy of the acquired 3-dimensional data was estimated to be better than 60 microm in lateral and 30 microm in height resolution. The data set was visualized and evaluated in a skull related 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.

Color↗
PubMed2001

The influence of maxillary central incisor position in complete dentures on /s/ sound production.

STATEMENT OF PROBLEM: The insertion of prosthodontic restorations often leads to speech defects, most of which are transient but nevertheless a source of concern to the patient. For the dental practitioner, there are few guidelines on designing a prosthetic restoration with maximum phonetic success. PURPOSE: This study investigated the effect of different maxillary central incisor positions on phonetic patterns. MATERIAL AND METHODS: The inclination angle of central incisor blocks in duplicate complete maxillary dentures was changed in a range of -30 degrees to +30 degrees from the original position (0 degrees). Test words and sentences were acoustically analyzed. Spectral parameters such as first peak, noise band (defined by upper and lower limits of the most intensively blackened frequency area), Fast Fourier Transformation power spectrum, energy spectrum, and time were investigated. Influences of oral stereognosis, hearing, and age as cofactors on /s/ articulation were also taken into account. RESULTS: The change of incisor block angle in both directions usually caused a poorer execution of the /s/ sound. The labial angulation seemed to have a greater effect than the palatal angulation. The most significant changes were those in the noise band and energy spectrum. CONCLUSION: Immediate phonetic adaptation of prosthetic restorations in the maxillary incisor region can be achieved only if the original position of the natural teeth is transferred to the denture. Although these misarticulations are, in most cases, likely to disappear within a few weeks, they may persist and even lead to psychosocial problems. A better understanding of the causes of misarticulation and the limits of adaptation according to certain morphologic parameters of dentures is important.

Adaptation, Physiological↗
PubMed2000

Clinical anatomy and palpability of the inferior lateral pterygoid muscle.

STATEMENT OF PROBLEM: The intraoral palpation technique of the inferior belly of the inferior lateral pterygoid (ILP) muscle is a standard diagnostic examination method for temporomandibular joint dysfunction syndrome, although different studies have revealed inconsistent results. PURPOSE: This study assessed the feasibility of the ILP muscle palpation by a simulated clinical setting. MATERIAL AND METHODS: Three dentists performed a bilateral palpation of the ILP muscle in 53 fresh and unfixed human cadavers and decided whether the muscle was palpable or unpalpable. In a second step, it was observed through the dissected infratemporal fossa, whether the examiner's finger did or did not touch the ILP muscle by simulating the performed palpation. Palpatory findings were supplemented by 1-dimensional measurements for determination of topographic relations of the ILP muscle within the infratemporal fossa. For statistical analysis, sensitivity, specificity, and negative and positive predictive values of the palpation technique were calculated. Interexaminer agreement was estimated with the kappa value. RESULTS: In 86 of 106 dissected specimens, a superficial fascicle of the medial pterygoid muscle was found in direct proximity to the ILP muscle. In these cases, a residual distance of 7.8 +/- 3.2 mm remained between the ILP muscle and buccinator fascia indented by the tip of the examiner's finger. In 10 of 20 specimens with an absent superficial fascicle, the finger was able to reach the ILP muscle. CONCLUSION: It is recommended that the ILP muscle palpation technique should no longer be considered as a standard clinical procedure because it is nearly impossible to palpate the ILP muscle anatomically and because the risk of false-positive findings (by palpation of the medial pterygoid muscle) is high.

Facial Pain↗
PubMed1999

Three-dimensional acquisition and visualization of dental arch features from optically digitized models.

A method for the acquisition and evaluation of 3D coordinates from anatomically oriented plaster casts is presented, which is based on optical phase shifting profilometry (a fringe projection technique). With the computer-controlled setup, measurements from different views can be combined to obtain a complete three dimensional reconstruction of the model surface. To allow faster evaluation, the result is converted into a range image. From this digital data set the characteristic features like cusp tips can be identified and located semi-automatically. Based on these marks, quantitative values for differences between situation models like local displacements, e.g. during orthodontic treatment, can be determined. The results are visualized as interactively controllable 3D computer graphics, which helps to make spatial relations clearer.

Calibration↗
PubMed1999

[Effect of dental prosthesis on the voice].

It is well known that alterations to the oral cavity caused by dental prostheses may affect speech articulation, although influences on the voice are not assumed. In addition to the vocal fundamental frequency, vibrations of the vocal chords generate overtones. Through the shape of the larynx and the upper airway, resonances and antiresonances are formed, and in this way overtones are amplified to a variable extent. Nozzle changes caused by a dental prosthesis in the oral cavity may possibly influence overtones but influences on the vocal fundamental frequency seem unlikely. The influence of dental prostheses on the voice is demonstrated in a patient who owned two different dental prostheses. The fundamental frequency rose by up to five semitones during speech and his vocal range increased by up to four semitones when a thin denture was used instead of a normal denture. When the position of the mandible was checked by intraoral needle point placement, a more rostral position of the mandible was recorded with the thin denture than with the normal denture. Sagittal magnetic resonance tomography imaging also showed that the larynx was in a more cranial position. This change was presumed to be due to an upward movement of the larynx induced by the tongue, which itself was found to be in a more cranial position with the thin denture. In this situation, increased tension of the laryngeal muscles were believed to induce a rise in fundamental frequency, shifting the voice range toward higher frequencies. These findings show that dental prostheses can cause vocal changes in individual cases. The etiology of this occurrence is still not clear. Its consequences, however, should be known to the dentist, ENT surgeon and phoniatrist if patients notice changes in their voice after having altered or replaced their dentures.

Aged↗
PubMed1999

Can dental prostheses influence vocal parameters?

STATEMENT OF THE PROBLEM: Alterations to the oral cavity caused by dental prostheses can affect speech articulation, whereas the influence of dental prostheses on the voice is unknown. For 1 patient, the fundamental frequency rose by up to 5 semitones during speech and his voice range was enlarged by up to 4 semitones when a thin denture was used instead of his normal denture. In this patient, intraoral needlepoint registration revealed a more rostral position of the mandible with the thin denture when compared with the normal denture. PURPOSE: This study evaluated the effects of such changes on phonation by varying the dentures of 20 subjects in line with those of the first patient. MATERIAL AND METHODS: The volumes of the test dentures were reduced and the vertical and horizontal dimensions of occlusion were varied. The influences of these changed dentures on speaking fundamental frequency, voice range (in semitones), and lowest and highest frequencies of the voice range were examined with a Homoth phonomat. RESULTS: A statistically significant influence of the different dentures on the investigated voice parameters was not proven; however, audible changes to the voice parameters for persons were documented. CONCLUSIONS: Variations of thickness and or volume of dentures and of the vertical and horizontal dimension of occlusion may result in unpredictable audible changes to the voice. Patients should be informed about possible effects of modified or new dentures on their voice.

Acrylic Resins↗
PubMed1999

Three-dimensional visualization and quantification of the mandibular articular surface by optical profilometry.

The aim of this study was to introduce a nondestructive optical technique for the quantitative assessment of natural biological surfaces as demonstrated with the example of the articular surface of the human temporomandibular joint. The computer-assisted quantitative evaluation of the surface is realized by the acquisition of three-dimensional images via the optical technique of phase measuring profilometry. After mathematical processing of the data set the resulting image can be visualized as three-dimensional object surface reconstructions or as grid surfaces from which arbitrary sections may easily be extracted. From such single sections we can calculate a value that represents the degree of height deviations of the section profile and can be regarded as a parameter for the surface roughness. Further quantitative information about the surface topography is provided by the Fourier transform analysis of the profiles. The Fourier spectrum contains information about the spatial distribution of roughness-causing protuberances along the overall surface. As an example one healthy condyle and one remodeled condyle from macerated cadaver mandibles were investigated. For the two samples evaluated we calculated a mean surface roughness of the entire articular surface with a value of 0.03 +/- 0.005 mm for the healthy condyle with its smooth surface and a value of 0.14 +/- 0.009 mm for the remodeled condyle. We recommend optical profilometry as a sophisticated technique for a more objective and quantitative pathological classification of articular surfaces and similar objects.

Fourier Analysis↗
PubMed1999

[In Process Citation]

Since February 1997 the Departments of Dentistry and Oral & Maxillofacial Surgery of the University of Munster, Germany, can be visited on the Internet on more than 1400 HTML pages. These Web pages have been organized using an especially designed database which ensures standardized layout of the presented information and systematic navigation. A various amount of the Web pages are created fully automatically from a database (e.g. lectures, list of resources (URLs)); manually created pages are automatically adjusted concerning layout, integrated in the overall structure and given uniform navigation elements. Among other things, the database generates an interactive Web-site index (like a tree view), which facilitates search.

Journal Article↗
PubMed1998

Computer-aided automated landmarking of cephalograms.

The computer-aided method presented is able to interpret and measure radiological structures automatically and reproducibly on a large number of randomly selected lateral head films of different film quality. For example the hard and soft tissue expression of the profile is used to discuss method, application and disadvantages. The performance of the system depends on image quality. The algorithm cannot be influenced by opacifications due to metal structure. In 90% of all cases the contours are identified correctly. Even if the image quality is poor, the recognition rate is about 84%. The selected cephalometric landmarks are placed in the right way in 85% of all cases. The constraint mathematical conditions and the high reproducibility improve the quality process of the cephalometric analysis. Recognition rates of 84% to 90% justify even nowadays the routine use of semi-automatic systems in PC-based analysis. With advancing digital radiography and improved computer performance, image interpreting systems will certainly become established.

Cephalometry↗
PubMed1998

Computer-aided axiography of asymptomatic individuals with Class II/2.

UNLABELLED: The condylar axiographic tracings of 23 asymptomatic adult volunteers (Helkimo-index DiO) with Class II/2 axiography relationships were compared to tracings of an analogous group (DiO; n = 30) with normal occlusion. The obtained measurements were evaluated statistically and discussed with respect to possible recording errors. RESULTS: The open-close movement proceeded uncharacteristically, differences existed only in protrusion, mediotrusion and their combined rotation component. In Class II/2 cases an approximately 7 degrees higher angle of the condylar path inclination (CPI) was measured. The Class II/2 group rotated to a significantly higher angle in protrusive and mediotrusive movements and showed longer condylar path lengths than the control group. Another significant difference was found in the location of maximum CPI values and maximum rotation angles within the condylar path, because in no case was isolated rotation or translation of the hinge axis observed. CONCLUSION: The temporomandibular joint of Class II/2 individuals shows a wider range of motion than joints of subjects with normal occlusion. The reduced capacity of motion which was assumed to exist in a so-called hack-bite could not be backed up for Class II/2 deep bite cases. The investigated differences cannot be seen as pathomechanisms, because all participants were clinically free of dysfunction. The neuromuscular engram to overcome the overbite controls a complex spatial motion pattern which cannot be described by a simplified mechanical abstraction of motion in the sagittal plane. The temporomandibular joint with its complex pattern of movement is able to create physiological mechanisms of compensation to react to different dental and skeletal features.

Adult↗
PubMed1981

[Results of sialography (author's transl)].

A randomly selected group of patients which had been subjected to sialography during 1975/76, was analysed retrospectively. In a total of 386 patients, 395 contrast radiographs had been performed; of these, 243 sialographs were evaluated retrospectively, the definite diagnosis having been established by surgery, biopsy or clinical course of the disease. The accuracy of diagnosis was 95% when employing diagnosis by exclusion (sialographic diagnosis having yielded "normal findings"), the correct diagnosis being the presence of concrements and inflammatory diseases of the salivary gland. However, the rate of error amounting to 5% must be considered a cause for concern insofar as of the total of 8 wrong diagnoses (against a total of 154 correct diagnoses), 7 patients had tumours which had not been recognized, four of these tumours being of a malignant nature. The presence of a space-occupying process was diagnosed with an accuracy of 88%. Space-requiring growths, provided they were properly diagnosed, were correctly localised in 83% of the cases. Statements on the degree of malignancy of a tumour--which were made in about one-third of the tumour diagnoses only--were found to be correct in 83% of the cases. False positive findings were obtained in 12% of the patients.

Adolescent↗