Christoph Runte

Evaluation of accuracy of insertion of dental implants and prosthetic treatment by computer-aided navigation in minipigs.

The survival of loaded implants is critically dependent on their biomechanical stability. We have used a computer-guided navigation technique to evaluate the accuracy of computer-assisted insertion for immediately-loaded implants in minipigs. On the basis of computed tomographical data, the Robodent system was used for preoperative planning and guidance of inserting the implant. An optical tracking system allowed positioning of the implant and immediate prosthetic rehabilitation by inserting it in a plaster model and during the operation. Postoperative computed tomograms (CT) showed that the implants were placed precisely in the preoperatively planned position. The accuracy achieved corresponded well with the spatial resolution of the CT used. Immediate placement of the prefabricated crowns resulted in favourable occlusal positioning. Histological cross-sections showed that the implants were biomechanically stable. The accuracy of insertion of oral implants illustrated here suggests that insertion and prosthetic modelling of implants may benefit from computer-assisted navigation.

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.

Quantification of facial asymmetry by 2D analysis – A comparison of recent approaches

INTRODUCTION Symmetry has been found to play a crucial role in attractiveness assessment and so its restoration is an essential problem in oral maxillofacial surgery. This paper presents an overview of recent 2D asymmetry analysis techniques. These are techniques which are based on the evaluation of two-dimensional data, like photos. The aim of this paper is to find the most precise and practical techniques to investigate facial asymmetry. MATERIALS AND METHODS For this purpose studies addressing symmetry investigations are collected and categorized by the type of data they extract from the photos. The reference points on the facial surface, which are frequently used in these studies, are presented and calculation methods are described. RESULTS Three kinds of techniques using vertical or horizontal reference lines or centres of bilateral points appear to be most appropriate. Recommendations are made, which aspects should be taken into account when calculating symmetry/asymmetry indices from photos. Advantages and disadvantages of the three selected methods are summarized in a table. CONCLUSIONS Using one of the three recommended approaches denoted by FA, AI and z-score allows calculating meaningful asymmetry values. The proper selection and identification of reference points is crucial. For highest accuracy, a sufficient number of evenly distributed and reproducible reference points should be used.

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 semiautomatically. 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.ZusammenfassungEs wird eine Methode vorgestellt, bei der schädelgerecht ausgerichtete Gipsmodelle mit der Phasenschiebeprofilometrie (Streifenprojektionstechnik) auf optischem Wege dreidimensional vermessen und digitalisiert werden. Die Rechnersteuerung erfaßt dabei mehrere Perspektiven des Modells und integriert diese zu einem digitalen 3D-Abbild, das zur Beschleunigung der weiteren Auswertung in ein Höhenbild umgesetzt wird. Anhand der digitalen Modelldaten können charakteristische Merkmale wie Höckerspitzen halbautomatisch aufgefunden und Veränderungen am Zahnbogen vor und beispielsweise nach einer kieferorthopädischen Behandlung quantitativ erfaßt werden. Die Visualisierung der Ergebnisse als interaktiv steuerbare 3D-Grafiken veranschaulicht räumliche Zusammenhänge in hohem Maße.

Measured symmetry of facial 3D shape and perceived facial symmetry and attractiveness before and after orthognathic surgery.

One aim of cranio-maxillo-facial surgery is to strive for an esthetical appearance. Do facial symmetry and attractiveness correlate? How are they affected by surgery? Within this study faces of patients with orthognathic surgery were captured and analyzed regarding their symmetry. A total of 25 faces of patients were measured three-dimensionally by an optical sensor using the fringe projection technique before and after orthognathic surgery. Based upon this data an asymmetry index was calculated for each case. In order to gather subjective ratings each face was presented to 100 independent test subjects in a 3D rotation sequence. Those were asked to rate the symmetry and the attractiveness of the faces. It was analyzed to what extend the ratings correlate with the measured asymmetry indices and whether pre- and post-surgical data differ. The measured asymmetry indices correlate significantly with the subjective ratings of both items. The measured symmetry as well as the rated symmetry and attractiveness increased on average after surgery. The increase of the ratings was even statistically significant. A larger enhancement of symmetry is achieved in pre-surgical strongly asymmetric faces than in rather symmetric faces.

Image-based biomimetric approach to design and fabrication of tissue engineered bone

Abstract The utilization of computer-aided technologies in tissue engineering has evolved in the development of a new field of computer-aided tissue engineering (CATE). Computer technologies can be used for the design and manufacturing (CAD/CAM) of scaffolds prepared from a specific building material to form a defined three-dimensional tissue. The hypothesis of the present experimental study was that autogenous cultivated osteoblasts can be grown on individualised scaffolds to improve bone regeneration in mandibular defects. Autogenous bone cells of minipigs were harvested and multiplicated in culture. Mandibular defects were created in the body and temporomandibular joint (TMJ) region of the mandible and a CT scan performed. The scaffold of the defect site was modelled by computed tomography (CT)-based rapid prototyping of polylactite/polyglycosite copolymers. Cells were seeded on the mandibular body scaffolds and the defects were reconstructed by the artificial materials. CT scans were performed directly after insertion and animals were sacrificed after 3 and 30days of healing time. The intraoperative situation as well as the postoperative CT scans demonstrated an accurate anatomical modelling of the defect sites. Transplanted cell/scaffold constructs appeared to enhance bone formation in the defect site as revealed by histological analysis. The combination of computer technology and tissue engineering may improve bone reconstruction approaches in the future.

Rechnergestützte Gestaltung von Epithesen nach optischer Abformung von Gesichtsdefekten / Computer-aided Design in the Modelling of Facial Prostheses from Optical Impressions of Facial Defects

Ein wesentlicher Nachteil der bislang bei der prothetischen Versorgung von Patienten mit Gesichtsdefekten angewandten Methoden zur Abdrucknahme liegt darin, daß durch das Abformmaterial Druck auf die abzuformenden Gewebe ausgeübt wird, wodurch sowohl die Genauigkeit der Abformung beeinträchtigt als auch der Patient belastet wird. Eine mögliche Alternative bieten hier optische 3-D-Koordinatenmeßtechniken wie die Streifenprojektionstechnik, die eine präzise und berührungsfreie Abformung der Gesichtsoberfläche ermöglichen. Am Beispiel eines Patienten, der im Verlauf einer Tumoroperation das linke Auge und Teile des Kiefers verloren hat, wird die Anwendung dieser Technik demonstriert. Es wurde hierfür ein 3-D-CAD-Programm entwickelt, mit dem auf der Basis der optisch gewonnenen Daten eine Epithesenrohf orm gestaltet werden kann. Dafür wird am Meßkamerabild mit einer Spline-Funktion interaktiv eine Randlinie festgelegt und die Epithesenoberseite durch Spiegelung von Teilen der gesunden Gesichtshälfte gestaltet. Auf der Basis des digitalen Modells wurde mit der Stereolithografietechnik ein Kunstharzmodell der Epithese erstellt sowie, nach Anprobe am Patienten, ein entsprechendes Wachsmodell.

Measuring facial symmetry: a perception-based approach using 3D shape and color

Abstract Objective: Facial symmetry is an important factor affecting esthetics. Thus, its restoration is an essential task in maxillofacial surgery. The aim of this study is to develop an objective measure of facial asymmetry by a novel approach where both the shape and the color are taken into account and to validate its correlation with perception. Methods: Optical three-dimensional (3D) face scans of 30 healthy adults are performed. Face-specific asymmetry indices are calculated by quantifying color differences as well as spatial distances between 3D data of a face and its mirrored copy. Subjective ratings of symmetry and attractiveness of the faces by 100 subjects are used to validate these indices. Results: The symmetry ratings show significant correlations with color and geometric asymmetry indices. The attractiveness ratings correlate only weakly with both indices. However, the product of the indices exhibits significant correlations with both attractiveness and symmetry ratings. Conclusion: The presented combined asymmetry index comprising shape and coloring turned out to reflect subjective perception of both facial symmetry and attractiveness. It thus promises to be a valid objective measure for facial esthetics, which could contribute, e.g., to the evaluation of surgical methods as well as to the design of craniofacial prostheses.

Zahnheilkunde und sprachlautbildung

ZusammenfassungFür die Entstehung einer fehlerhaften Aussprache werden viele Faktoren als mitwirkende Ursachen verantwortlich gemacht. Die Kiefer- und Zahnstellungsanomalie spielt als einer dieser Faktoren eine wichtige Rolle. Zusammenhänge zwischen morphologischen Veränderungen des Zahnstatus und Aussprachestörungen sind bekannt, werden aber in der Literatur unter-schiedlich diskutiert. Insgesamt ist von einer wechselseitigen Beziehung zwischen Dysfunktion und Formveränderung der Bezahnung auszugehen. Ziel unserer Literaturübersicht und experimentellen Untersuchung war es, den Einfluß von Formveränderungen auf die Lautbildung am Beispiel der zweiten Artikulationszone und der /s/-Lautbildung zu objektivieren. Durch Aufbringen von zahnärztlichem Phosphatzement auf die palatinalen Flächen der oberen Frontzähne wurde die zweite Artikulationszone experimentell verändert. Verschiedene Testwörter wurden vor- und unmittelbar nach der Zahnveränderung gesprochen. Die /s/-Lautbildungen wurden mit Hilfe der Sonagraphie akustisch analysiert und miteinander verglichen. Diese bei allen Probanden völlig gleichartige Veränderung des Zahnstatus führt zwar zu einer auditiv pathologischen /s/-Lautbildung, objektiv lassen sich aber durchaus interindividuelle Unterschiede feststellen. So gelingt mit dieser Methode zwar eine objektive Differenzierung zwischen akustisch korrekter und inkorrekter /s/-Lautbildung; Sprache und Sprachlautbildung erweisen sich aber als derart komplexe Mechanismen, daß sie sich nicht in einen einfachen kausalen Zusammenhang mit Veränderungen der peripheren Sprechwerkzeuge bringen lassen.SummaryMany factors are thought to be responsible for misarticulation. Maxillomandibular or dental irregularities play an important role as one of these factors. Correlations between morphological changes in dental status and speech disorders are well known, but different opinions are discussed in the literature. A reciprocal relationship between dysfunction and various dental irregularities is assumed. The objective of our review and experimental investigations was to document the influence of dental irregularities on speech articulation as exemplified by the second articulation zone and /s/ articulation. The second articulation zone was experimentally changed by application of dental cement to the palatal surface of the upper incisors. Various words were spoken before and just after the change to the frontal teeth. The /s/ articulations were acoustically analyzed by means of sonagraphy and compared with each other. Although this modification of the teeth, which was identical in all probands, leads to /s/ misarticulation from the standpoint of auditory analysis, interindividual differences were recorded by acoustic means. It is thus possible to differentiate objectively between acoustically correct and incorrect /s/ articulation. Speech and articulation are, however, such complex mechanisms that it is impossible to characterize them by simple causal connections with maxillomandibular or dental irregularities.