International Poster Journal of Dentistry and Oral Medicine, 04/2000

The treatment of orofacial pain and temporo-mandibular disorders (TMD) has evolved into a multidisciplinary approach. Studies have demonstrated that MRI of the TMJ is the most accurate concerning disk position. CT is considered to be the most accurate for osseous changes. Being able to register these two modalities allows to transfer the coordinates of computerized axiography and scelettal analyses on the base of a lateral cephalometric radiograph for anatomical reference and for disk displacement. Material and methods: In order to display TMJ images as a dynamic study has been affected by using MAGNETOM SP 63, Siemens and C 100 XL, Imatron. To facilitate this procedure a modified BURNETT-device was developed to passivily open the patient's mouth. Results: The tomograms have a ACR Nemo-format and were transferred in PCX-format for using surface-based methods to register CT- and MRI-imagery. The transfer of the original geometry in a CAD-model is concluded. The 3D-models of the TMJ are creating by using a five-axio CNC-milling machine and laser lithography. Conclusion: An initial comparison of the 3D-models of the TMJ's vs anatomic structures showed a good correlation with respect to the axiographpyprotocol While this approach based on aligment of surfaces, this technique ist depend on the a priori quality of the available segmentations. Alternativly, intensity-based technique can work directly with the volumetric data and must be relied on some what ad hoc assumptions about the nature of the signals involved. Adjustment of the relative position and orientation is needed until the mutual information between images and computerized axiography is maximized. Keywords: TMJ, MRI, CT, 3D model, 3D reconstruction, axiography, lateral X-ray, laser lithography modelling

Characteristics of the Vector-system are the linear movement of the instruments parallel to the tooth surface and an indirect application of the ultrasound's energy on the tissues to be treated due to a liquid film adhering to the instrument, or by particle suspension. 24 subjects (14 male, 10 female, age: 37 - 64 yrs.) were recruited for a clinical trial aimed at assessing the effect of the Vector periodontal therapy. The treated periodontal areas showed no endodontic disorder and the pockets measured (pressure calibrated probe) between 5 mm and 14 mm. After a baseline examination including assessments of oral hygiene standards, attachmemt level, bleeding on probing (BOP) and suppuration the patients received oral hygiene instructions. For the initial periodontal treatment the metallic Vector-instruments and the Vector-hydroxylapatite (HA)-suspension was used according to the manufacturer's instructions. By using a split mouth design on the same patients, diluted HA-suspension with a pH of 7 (control) and diluted citrus acid solution with a pH of 5.5 modified analogous HA-suspension (test group) were assessed. After 6 weeks, 3 months, 6 months and 12 months all of the results were re-evaluated. The participants reveived a professional oral prophylaxis by using the Vector fiber-reinforced resin-recall-instruments and analogous suspensions, areas with persistent BOP were re-treated. Six weeks after the initial treatment a significant reduction of the pocket depths and of the number of periodontal areas with positive BOP was attained (Kruskal/Wallis; Wilcoxon Mann-Whitney). Suppurations had completely disappeared. Twelve months after the initial treatment an attachment gain of more than 2 mm was recorded on 21 out of 24 patients on more than three periodontal areas. No gender specific significant differences existed; data of both the test and control group was derived from the same population. The pH of the Vector coupling fluid seems to have a minor influence on the treatment outcome. Keywords: periodontitis, Vector, Initial Treatment, Supportive Periodontal Therapy

Today, the oral intraosseous implantology offers an important and well-accepted treatment concept in dentistry. Prosthetic restorations, partially or totally retained by osseointegrated dental implants, should be an integrated part of the overall treatment concept in any private practise to make the functional and aesthetic advantages of implant retained prosthesis available for all patients. Therefore, it is important to incorporate implant retained restorations into the prosthetic curriculum from an early stage on.We started in our department in 1992 to include the fabrication of an implant retained fixed partial denture into the curriculum of the second phantom-course in preclinical prosthodontics (5. semester). The students have to fabricate a combined tooth/implant retained bridge, in which the mesial abutment is a premolar (tooth 45) treated with post and core and the distal abutment is a Paragon®-Implant. Contrarily to other concepts which teach only some of the procedures, e.g. impression taking, in Marburg the students have to perform all relevant clinical procedures, using a mannequin head, as well as the laboratory procedures by themselves. The described concept enables the students to learn the specific procedures involved in implant prosthodontics under realistic clinical conditions. Keywords: Implantologie, vorklinische Ausbildung, Phantomkurs, Implantatprothetik

Objectives. Detailed knowledge of the elusive anatomy of root canals systems is essential for successful endodontics. The current study employed high resolution scanning tomography (µCT) to assess changes in the canals' paths after preparation using 4 NiTi preparation systems.Material and Methods. A commercially availabe µCT scanner (Scanco, Switzerland) was used to analyze 40 extracted maxillary molars. Teeth were scanned before & after 30 canals each were prepared using NiTi K-Files, Lightspeed, ProFile .04 & GT Files. Precise repositioning allowed repeated scanning of specimens after preparation. Dentin volume (V) and surface areas (A) for each canal before & after preparation were calculated using specially developed software. Differences between means were analyzed using repeated measures ANOVA.Results. Mean canal volumes (± SD) & surface areas were 2.30 ± 1.51mm3 & 18.76 ± 7.72mm2 before and 4.39 ± 1.60mm3 & 24.45 ± 6.63 mm2 after preparation. Changes in canal volume and area differed significantly (p Keywords: micro computed tomography, root canal, rotary instrumentation

Minimal invasive navigational resection of anosteoma of the lateral pterygoid process via anintraoral approachMinimal invasive tumor surgery needs detailed andexact planning using CT scans to show extensionof the tumor and point out vital structures.Computer assisted surgery allows preoperativeplanning and simulation, intraoperativenavigation and postoperative control. On the baseof an axial spiral CT or MRI data set in ourclinic the STN-Navigation-System (Stryker-Leibinger/Zeiss) is used for preoperative planning and intraoperative controlling of guided biopsies and tumor resection. Minimal invasive resection of an osteoma of the right lateral pterygoid process was performed through an intraoral approach. With a guided drill a two millimeter mini screw could be inserted safely into the osteoma onto which a wire was fixed. After guiding the chisel to the desired point of the external lamina of the pterygoid process the tumor could be completely removed. Intraoperative navigation wih non-invasive registration allows guided biopsies and tumor resections achieving minimal invasive diagnostic and therapeutic treatment in oral and maxillofacial surgery. Keywords: computer assisted surgery, frameless stereotaxy, maxillofacial surgery, tumor surgery

In comparison to conventional screen-film combinations Digital Radiography (DR) offers several advantages, i.e. reduction of the x-ray exposure and the further option of image processing. It is an obvious controversy that collimated film areas provide information for cephalometric analyses. One of the most interesting side effects of DR is the possibility to perform a complete analysis of the entire scull in typically collimated lateral cephalograms.The aim of this prospective study was to determine the validity of this special image processing method developed by the Department of Orthodontics, University of Muenster.Out of 400 digital radiographs taken for orthodontic diagnosis, 100 lateral head films were randomly selected. The routine radiographs were taken from the Department of Radiology, University of Muenster. For each patient the facial cranium exclusively was faded in and exposed at 77kV/12 mAs with an anode to film distance of 350 cm.The digital image acquisition included laser-scanning (pre-read) of the storage phosphor plates, individual processing of every image (Pattern Recognition for Iris of Exposure Field - algorithm) and storing of the original and processed images using the DICOM - format.The intra-individual reproducibility of the landmarks defined by DELAIRE who proposed a cranial and craniofacial analysis was examined using the NIH-Image 1.62 analysis program.The results show that it is possible to attain information from collimated areas (cranial vault, cervical vertebra) using DR combined with special image processing methods. This is due to the x-ray scatter and the various contrast enhancements possible in different film areas of the same image.The information attained from these areas with very low x-ray load is sufficient for a complete cranial analysis proposed by DELAIRE, so that an increase of field size can be avoided in many clinical cases.For the first time since 1987 the gold standard of head film acquisition for the DELAIRE-Analysis proposed by PRECIOUS and MILES has been redefined. Keywords: Digitale Fernröntgenseitenbilder, digitale Lumineszenzradiographie, Strahlenreduktion, Delaire-Analyse

The aim of this retrospective study was todetermine the number of premature membraneexposures and to evaluate possible predisposingfactors.72 patients were treated with ePTFE membranes(GoreTex augmentation material) for membraneguided bone regeneration (GBR) of periimplantbone defects (median age 38,5 years, minimum18 years, maximum 68 years; 39 % male and 61 %female patients, data collection between 03/1993and 02/2000).61 % of the membranes were applied in the upperjaw and 39 % in the lower jaw. 61 % of all GBRprocedures were done in context with single toothreplacements.44 % of all sites revealed a premature membraneexposure (PME). 72 % of these PMEs occured afterprimary uneventful healing period after membraneimplantation.Statistical analysis revealed a significantcorrelation between the parameters 'prematuremembrane exposure', 'membrane covering thealveolar ridge' (p=0,0004)and 'membrane locatedbeneath the incision line' (p=0,0004).Additionally a tendency for correlation wascalculated for the parameters 'defectconfiguration' (p=0,08) and 'smoking' (p=0,04).The defect morphology, the flap and incisiondesign and the smoking habits of the patientshave to be taken into critical consideration ifGBR is planned. Non space maintaining defectconfigurations, smoking habits and crestalincisions crossing the planned membrane locationseem to be contraindications for the use ofePTFE membranes. However, alternative treatmentmethods should be taken into account. Keywords: guided bone regeneration, complications, premature membrane exposure