Dieter Dirksen

Westfälische Wilhelms-Universität Münster · Department of Prosthetic Dentistry

Research interests

  • Interests
    Medical Imaging, Medical Image Processing, Medical Image Analysis, Biomedical Engineering, Tissue Engineering, Biomaterials

Publications

  • 1.41
    Impact points
    Autofocusing in digital holographic phase contrast microscopy on pure phase objects for live cell imaging.

    Patrik Langehanenberg, Björn Kemper, Dieter Dirksen, Gert von Bally

    Applied optics. 08/2008; 47(19):D176-82.

    Digital holography enables a multifocus quantitative phase microscopy for the investigation of reflective surfaces and for marker-free live cell imaging. For digital holographic long-term investigations of living cells an automated (subsequent) robust and reliable numerical focus adjustment is of pa... [more] Digital holography enables a multifocus quantitative phase microscopy for the investigation of reflective surfaces and for marker-free live cell imaging. For digital holographic long-term investigations of living cells an automated (subsequent) robust and reliable numerical focus adjustment is of particular importance. Four numerical methods for the determination of the optimal focus position in the numerical reconstruction and propagation of the complex object waves of pure phase objects are characterized, compared, and adapted to the requirements of digital holographic microscopy. Results from investigations of an engineered surface and human pancreas tumor cells demonstrate the applicability of Fourier-weighting- and gradient-operator-based methods for robust and reliable automated subsequent numerical digital holographic focusing.
  • 1.67
    Impact points
    Optimizing color reproduction of a topometric measurement system for medical applications.

    Matthias Westhäuser, Guido Bischoff, Zoltan Böröcz, Johannes Kleinheinz, Gert von Bally, Dieter Dirksen

    Medical engineering & physics. 03/2008;

    Integration of color information in 3D models acquired with a topometric measurement system opens a wide field of applications in medicine, e.g. prosthetics. To ensure an accurate and reliable color reproduction in a 3D topometric measurement system, different approaches have been evaluated. These t... [more] Integration of color information in 3D models acquired with a topometric measurement system opens a wide field of applications in medicine, e.g. prosthetics. To ensure an accurate and reliable color reproduction in a 3D topometric measurement system, different approaches have been evaluated. These techniques focus on the calibration of the CCD camera using color test charts by applying a polynomial regression method as well as numerical methods to compensate an intensity decay of the illumination in 3D datasets which is caused by varying distances and orientations of the measured object with respect to the light source. The methods presented in this contribution have been applied to a topometric measurement system with one-chip color CCD cameras. An enhanced color reproduction of various objects is demonstrated.
  • 0.53
    Impact points
    Modular optical topometric sensor for 3D acquisition of human body surfaces and long-term monitoring of variations.

    Guido Bischoff, Zoltan Böröcz, Christian Proll, Johannes Kleinheinz, Gert von Bally, Dieter Dirksen

    Biomedizinische Technik. Biomedical engineering. 02/2007; 52(4):284-9.

    Optical topometric 3D sensors such as laser scanners and fringe projection systems allow detailed digital acquisition of human body surfaces. For many medical applications, however, not only the current shape is important, but also its changes, e.g., in the course of surgical treatment. In such case... [more] Optical topometric 3D sensors such as laser scanners and fringe projection systems allow detailed digital acquisition of human body surfaces. For many medical applications, however, not only the current shape is important, but also its changes, e.g., in the course of surgical treatment. In such cases, time delays of several months between subsequent measurements frequently occur. A modular 3D coordinate measuring system based on the fringe projection technique is presented that allows 3D coordinate acquisition including calibrated color information, as well as the detection and visualization of deviations between subsequent measurements. In addition, parameters describing the symmetry of body structures are determined. The quantitative results of the analysis may be used as a basis for objective documentation of surgical therapy. The system is designed in a modular way, and thus, depending on the object of investigation, two or three cameras with different capabilities in terms of resolution and color reproduction can be utilized to optimize the set-up.
  • 1.44
    Impact points
    A prospective comparison of octyl-2-cyanoacrylate and suture in standardized facial wounds.

    J G K Handschel, R A Depprich, D Dirksen, C Runte, A Zimmermann, N R Kübler

    International journal of oral and maxillofacial surgery. 05/2006; 35(4):318-23.

    Regarding the cosmetic results of wound closure using tissue adhesives as opposed to sutured wounds, most published studies are performed on children and with non-standardized lacerations, which makes it difficult to transfer the results to facial incisional wounds in adults. There are also conflict... [more] Regarding the cosmetic results of wound closure using tissue adhesives as opposed to sutured wounds, most published studies are performed on children and with non-standardized lacerations, which makes it difficult to transfer the results to facial incisional wounds in adults. There are also conflicting conclusions about the cosmetic results. The purpose of this randomized prospective study was to compare the cosmetic outcomes of wound closure with sutures and octyl-2-cyanoacrylate in standardized facial wounds in adults. To compare very similar facial wounds, the infraorbital cut (lower eyelid incision) was used in 45 patients. The assessment was performed by patients and surgeons blind to the data. Phase-shifting profilometry was used to measure the profile of the scars. No early complications were observed in any group. The wound depth in the tissue adhesive group was significantly greater than in the suture group. There were no differences in the overall cosmetic results among all patients in the two groups. Interestingly, in the younger patients the result of the sutured wounds was superior to that of the adhesive-treated patients. The Dermabond skin adhesive provides a means of closure of facial surgical wounds without early complications, but adjustment of the edges of the wound and the cosmetic result in younger patients are less successful than with thin sutures.
  • [Objective assessment of cosmetic outcome of scars]

    J G K Handschel, R A Depprich, D Dirksen, C Runte, A Zimmermann, Z Böröcz, N R Kübler

    Mund-, Kiefer- und Gesichtschirurgie : MKG. 12/2005; 9(6):396-9.

    AIM OF THE STUDY: Cosmetic outcome of surgical treatment in the facial region is influenced by the appearance of the scar. The purpose of this investigation was to evaluate the objectivity and validity of various methods for the assessment of scars. MATERIAL AND METHODS: 45 patients undergoing facia... [more] AIM OF THE STUDY: Cosmetic outcome of surgical treatment in the facial region is influenced by the appearance of the scar. The purpose of this investigation was to evaluate the objectivity and validity of various methods for the assessment of scars. MATERIAL AND METHODS: 45 patients undergoing facial surgery were examined three months after surgery. Three maxillofacial surgeons evaluated the wounds in a blinded manner using a visual analog scale (VAS). The patients also used the VAS for evaluation of their own scar. The surface of the scars was also measured by optical profilometry. Finally, the colour of the scars was analysed using both the RGB colour model and the HSV colour model. RESULTS: Interestingly, there was no significant correlation between the values of R (red) as assessed by the three surgeons. However, there was a very strong correlation between the values of H (hue) as assessed by the three raters. The appearance of the surface was more important in the patients' evaluation than in the raters' assessment. CONCLUSION: The hue of a scar as measured in terms of the H value in the HSV colour model is an objective and reliable measure for assessing the cosmetic outcome of facial surgery.
  • 0.53
    Impact points
    [Investigation of influencing variables on the computer-aided simulation of contacts in dynamic occlusion based on optically digitized plaster casts]

    Z Böröcz, D Dirksen, C Thomas, C Runte, F Bollmann, G von Bally

    Biomedizinische Technik. Biomedical engineering. 06/2004; 49(5):111-6.

    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 p... [more] 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.
  • Image-based biomimetric approach to design and fabrication of tissue engineered bone.

    Ulrich Meyer, Christoph Runte, Dieter Dirksen, T. Stamm, T. Fillies, Ulrich Joos, Hans-Peter Wiesmann

    CARS 2003. Computer Assisted Radiology and Surgery. Proceedings of the 17th International Congress and Exhibition, London, June 25-28, 2003; 01/2003

  • 0.53
    Impact points
    [Computer-assisted development of epitheses after optical recording of facial defects]

    D Dirksen, C Runte, H Deleré, C Thomas, Z Böröcz, F Bollmann, G von Bally

    Biomedizinische Technik. Biomedical engineering. 05/2002; 47(4):85-90.

    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 fring... [more] 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.
  • 1.22
    Impact points
    The influence of maxillary central incisor position in complete dentures on /s/ sound production.

    C Runte, M Lawerino, D Dirksen, F Bollmann, A Lamprecht-Dinnesen, E Seifert

    The Journal of prosthetic dentistry. 06/2001; 85(5):485-95.

    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.... [more] 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.
  • 1.22
    Impact points
    Three-dimensional quantification of color-marked occlusal paths on anatomically oriented casts.

    D Dirksen, C Runte, Z Böröcz, C Thomas, G von Bally, F Bollmann

    The Journal of prosthetic dentistry. 03/2001; 85(2):156-61.

    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... [more] 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.
  • 1.41
    Impact points
    Endoscopic double-pulse electronic-speckle-pattern interferometer for technical and medical intracavity inspection.

    B Kemper, D Dirksen, W Avenhaus, A Merker, G von Bally

    Applied optics. 09/2000; 39(22):3899-905.

    An endoscope electronic-speckle-pattern interferometer (ESPI) camera system is presented that can be applied to examinations of technical objects as well as for in vitro and in vivo minimal invasive medical diagnostics. Integration of optical fibers for the guidance of a cw-laser beam and an endosco... [more] An endoscope electronic-speckle-pattern interferometer (ESPI) camera system is presented that can be applied to examinations of technical objects as well as for in vitro and in vivo minimal invasive medical diagnostics. Integration of optical fibers for the guidance of a cw-laser beam and an endoscopic imaging system yield a compact ESPI system that opens up new possibilities for highly sensitive interferometric intracavity inspection under handheld conditions. A CCD camera in combination with a fast frame-grabber system allows dynamic image subtractions at a frequency rate of as much as 25 Hz with high fringe contrast. Results from investigations of technical objects and biological objects in vitro and in vivo are obtained. In endoscopic minimal invasive therapy this method could substitute for the missing operator's tactile contact with the treated tissue by replacing it with visual information (endoscopic taction).
  • 1.22
    Impact points
    Clinical anatomy and palpability of the inferior lateral pterygoid muscle.

    U Stratmann, K Mokrys, U Meyer, J Kleinheinz, U Joos, D Dirksen, F Bollmann

    The Journal of prosthetic dentistry. 06/2000; 83(5):548-54.

    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 stud... [more] 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.
  • 0.89
    Impact points
    Three-dimensional acquisition and visualization of dental arch features from optically digitized models.

    D Dirksen, S Diederichs, C Runte, G von Bally, F Bollmann

    Journal of orofacial orthopedics = Fortschritte der Kieferorthopädie : Organ/official journal Deutsche Gesellschaft für Kieferorthopädie. 02/1999; 60(2):152-9.

    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 ... [more] 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.
  • 3.32
    Impact points
    Three-dimensional visualization and quantification of the mandibular articular surface by optical profilometry.

    D Dirksen, U Stratmann, J Kleinheinz, G von Bally, F Bollmann

    Cells, tissues, organs. 02/1999; 164(4):212-20.

    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 rea... [more] 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.
  • Optimization of spatial phase shifting in endoscopic electronic speckle pattern interferometry

    Björn Kemper, Jochen Kandulla, Dieter Dirksen, Gert von Bally

    Optics Communications.

    Endoscopic electronic speckle pattern interferometry (endoscopic ESPI) is a versatile tool for the inspection of technical and biological cavities. By the utilization of spatial phase shifting (SPS) methods, it is possible to obtain quantitative information about movements and displacements. An impo... [more] Endoscopic electronic speckle pattern interferometry (endoscopic ESPI) is a versatile tool for the inspection of technical and biological cavities. By the utilization of spatial phase shifting (SPS) methods, it is possible to obtain quantitative information about movements and displacements. An important quality parameter for such phase measurement techniques is a minimized noise of the phase difference. In this paper, a geometry for digital Fourier holographic reconstruction of the exit aperture of the endoscope imaging system is presented to adjust precisely and reliably the phase gradient between object wave and reference wave. Thus, the noise of the phase difference measured by endoscope SPS ESPI systems is reduced. Furthermore, the experimental setup can be simply integrated into an endoscope ESPI system with the advantage that no additional aperture in the optical path is needed.
  • Three-dimensional quantification of color-marked occlusal paths on anatomically oriented casts

    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 aspects because existing measuring techniques fail to provide 3-dimensional data for more than a few single points... [more] 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 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.)
  • Lensless Fourier holography for digital holographic interferometry on biological samples

    Dieter Dirksen, H. Droste, B. Kemper, H. Deleré, M. Deiwick, H.H. Scheld, G. von Bally

    Optics and Lasers in Engineering.

    Digital holography as a tool for highly sensitive, interferometric non-destructive testing has several advantages compared to holographic measurements based on conventional storage media like an all-digital processing and a direct access to the phase of the object wave. Experimental results of inter... [more] Digital holography as a tool for highly sensitive, interferometric non-destructive testing has several advantages compared to holographic measurements based on conventional storage media like an all-digital processing and a direct access to the phase of the object wave. Experimental results of interferometric investigations of heart valve bio-prostheses with a setup for lensless Fourier holography are presented which demonstrate that this technique is applicable to such biological samples with their wet and unstable surfaces. Limitations on size and resolution of the reconstructed object caused by the properties of the CCD sensor are discussed.
  • 1.23
    Impact points
    Spectral analysis of /s/ sound with changing angulation of the maxillary central incisors.

    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 of 18 subjects were duplicated. The central incisors were fixed in a pivoting appliance so that their pos... [more] 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 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.
  • A prospective comparison of octyl-2-cyanoacrylate and suture in standardized facial wounds

    J.G.K. Handschel, R.A. Depprich, D. Dirksen, C. Runte, A. Zimmermann, N.R. Kübler

    International Journal of Oral and Maxillofacial Surgery.

    Regarding the cosmetic results of wound closure using tissue adhesives as opposed to sutured wounds, most published studies are performed on children and with non-standardized lacerations, which makes it difficult to transfer the results to facial incisional wounds in adults. There are also conflict... [more] Regarding the cosmetic results of wound closure using tissue adhesives as opposed to sutured wounds, most published studies are performed on children and with non-standardized lacerations, which makes it difficult to transfer the results to facial incisional wounds in adults. There are also conflicting conclusions about the cosmetic results. The purpose of this randomized prospective study was to compare the cosmetic outcomes of wound closure with sutures and octyl-2-cyanoacrylate in standardized facial wounds in adults. To compare very similar facial wounds, the infraorbital cut (lower eyelid incision) was used in 45 patients. The assessment was performed by patients and surgeons blind to the data. Phase-shifting profilometry was used to measure the profile of the scars. No early complications were observed in any group. The wound depth in the tissue adhesive group was significantly greater than in the suture group. There were no differences in the overall cosmetic results among all patients in the two groups. Interestingly, in the younger patients the result of the sutured wounds was superior to that of the adhesive-treated patients. The Dermabond® skin adhesive provides a means of closure of facial surgical wounds without early complications, but adjustment of the edges of the wound and the cosmetic result in younger patients are less successful than with thin sutures.
  • Quantitative determination of out-of-plane displacements by endoscopic electronic-speckle-pattern interferometry

    B. Kemper, D. Dirksen, J. Kandulla, G. von Bally

    Optics Communications.

    The combination of endoscopes and electronic-speckle-pattern interferometry requires a more detailed consideration of their imaging properties with respect to interferometric fringe formation, if a quantitative analysis of the observed deformation is desired. Due to a relatively small distance betwe... [more] The combination of endoscopes and electronic-speckle-pattern interferometry requires a more detailed consideration of their imaging properties with respect to interferometric fringe formation, if a quantitative analysis of the observed deformation is desired. Due to a relatively small distance between the illuminating and the imaging optical elements and to strongly divergent beams, the sensitivity vector may not be regarded as constant, and image distortions caused by the endoscope optics must be taken into account. A simplified model that deals with the situation of a plane object perpendicular to the optical axes of the endoscope is presented and verified by experimental results.
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