International Poster Journal of Dentistry and Oral Medicine, 02/2000

Therapy of tumors needs detailed planning using CT or MRI to show extension of the malignoma, define intended safety margins and point out vital structures. Furthermore reconstruction following tumor resection needs reliable information also to choose correct type of grafts and to predict the outcome. On the base of an axial spiral CT or MRI data set the STN-Navigation-System (Stryker-Leibinger/Zeiss) is used for preoperative planning, intraoperative navigation and postoperative controlling of radical tumor resection and reconstruction. The predictive and intraoperative advantage concerning postsurgical outcome by using modern navigation systems is investigated in the treatment of patients with carcinoma, osteoma, meningioma and esthesio-neuroblastoma. Tumor resection and primary reconstruction were preoperatively planned. Intraoperatively tumor, savety margins and contours of transplanted tissue were navigated. Frameless stereotaxy was successfully completed in all cases of radical tumor resection. Computer assisted treatment improves preoperative planning by combining CT and MRI data. Tumor volume before preoperative chemotherapy can be assessed and transfered to the data-set after chemotherapy to perform radical resection inside the old borderlines. Intraoperative navigation makes radical tumor surgery more reliable by going for the safety margins, saving vital structures and leading the reconstruction to preplanned results. Keywords: computer assisted surgery, frameless stereotaxy, maxillofacial surgery, reconstructive surgery

For the past 15 years magnetic resonance imaging (MRI) has increasingly been used in the diagnosis of craniomandibular disorders. The present standardized evaluation form was created to establish a more systematic approach to the evaluation of MRI images of the temporomandibular joint. The initial parameters to be evaluated are condylar morphology (compacta and spongiosa), fossa and tubercular morphology, and disk morphology. Next, the condyle/fossa relationship with the mouth open and closed, the disk position in two planes (coronal, vertical to the long axis of the condyle) with the mouth open and closed, and the bilaminar zone are examined. Finally, the T2-weighted signals in the condylar region, in the joint space, and in the bilaminar zone are evaluated. The MRI images presented originate from a retrospective study of 77 patients in whom an arthropathy of the temporomandibular joint was clinically suspected. The images were taken using bilateral temporomandibular surface coils and FLASH or SE sequences (T1 and T2 weighting) in two planes without using a contrast medium. The standardized evaluation form streamlines MRI diagnosis. Moreover, the risk that subsidiary findings might be missed is minimized. Keywords: craniomandibular disorders, CMD, temporomandibular joint, diagnosis, magnetic resonance imaging, evaluation form

The aim of this study was to examine the values measured with the Diagnodent®-system for caries detection concerning a dependence on the dryness of the tooth-surface. Measurements were made at 40 points on the occlusal surface of filling-free human extracted teeth stored in physiological saline solution. The teeth, altogether 25 premolars and molars, and the probe of the measurement device were fixed on a mechnical stage, so that their position could be adjusted with a precision of 0.01 mm. All measurements were made at a temperature of 21°C, the relative humidity was 55%. At the beginning of each measurement, the tooth-surface was dried with a gaze-swab. The light-probe A of the Diagnodent®-system was put on the tooth-surface and in temporal intervals of 30 sec the momentary laser-fluorescence value was listed. The duration of all measurement was determined to 22 minutes. In a previous study, it could be shown that dependent on the individual caries risk, a value up to 10 indicates that no dental therapy is necessary. Values of 11 to 30 indicate preventive care and values higher than 30 demand restorative therapy. For this reason the laser-fluorescence values were evaluated in three groups. Within the median values from 0 to 10 (group I), no changes were observed while the drying of the tooth surface took place. In the groups with median values over 10 changes could be observed. Dependent on the period of observation (0.5 to 20 min), the median standard-deviation of the laser-fluorescence-values from 11 to 30 (group II) increased from 0.1 to 1.7. In the group with values over 30 (group III), the median standard-deviation increased from 0.5 to 5.7. Using the laser-fluorescence system for monitoring the progression of a carious lesion, variations of ±2 units can appear when a primary laser-fluorescence value of 11 to 30 was measured. A primary laser-fluorescence value of over 30 can result in variations of ±6 units, which possibly are not caused by the progression of caries but by the unequal dryness of the tooth-surface. Keywords: Laser-Fluoreszenz, Laser, Diagnodent-System, Trockenheit, Austrocknung

The aim of this study was to compare the values measured with the Diagnodent®-system for caries detection to the caries extension in enamel. 40 filling-free human extracted teeth stored in physiological saline solution were examined. After cleaning the tooth the surface was examined with the Diagnodent®-system at three points (mesial, central and distal). After staining the sections with Toluidine Blue/Rhodamin B the caries extension of the areas measured with the laser fluorescence system could be examined by light microscopic analysis. With increasing extension of caries in enamel higher and more varying laser fluorescence values were measured (correlation coefficient: 0.85). The values of the laser fluorescence measurements (before embedding the teeth in light-activated plastic) could always be reproduced after 1.5 hours storing the teeth in physiological saline solution. Up to a measured value of 10 a caries in enamel of up to 0.3 mm depth can be expected. At the moment a classification of caries in enamel with the laser fluorescence system is not possible due to the strongly varying measured values. Keywords: caries detection, laser fluorescence, histology, Diagnodent-System

For primary reconstruction of intraoral defects after tumorresection the microvascular anastomosed the radial forearm flap is a very reliable method. Disadvantages are the additional split-thickness skin grafting from the upper thigh for covering the harvesting defect at the foreram, the risk of complications of exposed tendons, and the limited adaption of skin and hairs especially in men to the mucosa of the oral cavity. To overcome these disadvantages we developed the tissue engineered prelamination of the radial forearm flap. At the time of clinical diagnosis, when the taking the biopsy for pathologic confirmation, an additional biopsy from healthy mucosa is gained for tissue engineering. Within 14 days in a graft is cultured consisting of a mucosa epithelium on a membrane. 7 days before tumor resection this mucosa membrane is implanted in a subcutaneous pocket at the lower arm in local anesthesia. When reconstructing after tumor resection the vessel pedicle and the connective and muscle tissue of the lower forearm flap covered by the tissue engineered mucosa is harvested extending the primary incision proximally. The harvesting defect at the lower forearm is covered primarily by the skinflaps. The tissue engineered mucosa radial forearm flaps showed uneventful intraoral healing and a differentiation of the flap surface into oral mucosa. The harvesting defect at the lower arm healed without complication. This technique reduces the morbidity at the graft harvesting site as well as it improves considerably the soft tissue situation in the oral cavity, producing new perspectives for intraoral reconstruction techniques. Keywords: radial forearm flap, tissue engineering

During orthodontic-surgical treatment a three-dimensional repositioning of the maxilla is needed after Le Fort I osteotomy. The preoperative planning usually involves a two-dimensional lateral radiograph. However, the lateral radiograph consists of two dimensions, whereas, during surgery, three dimensions have to be considered. Therefore, the third dimension's influence on treatment planning was investigated in a first study. Lateral radiographs were taken of 20 skulls. Impressions were taken of the maxilla and maxillary teeth. Casts were fabricated, and cuts were made in the transverse vertical plane at the level of the tips of the canines and the mesiobuccal cusps of the first molars bilaterally. Calculations of the discrepancies of the position of reference points on the lateral radiograph and on the lateral surface of the maxilla after the transfer from two to three dimensions revealed for the first molar differences up to 3.3 mm. It is possible to reduce these errors by application of the Goettingen concept for three-dimensional positioning of the maxilla using the 'model-repositioning instrument' for cast surgery and the 'three-dimensional double splint method' with condylar positioning during surgical procedure. This instrument and method were applied during treatment of 20 adult patients in a second study, and the position of the maxilla before and after surgery was analyzed. It was found that the planned position of the maxillary dental arch could be transferred from model surgery to actual surgery with an accuracy of ± 1 mm sagittally and vertically. Keywords: Orthognathic surgery, Le Fort I osteotomy, 3-dimensional repositioning, condylar positioning

To obtain a sufficient primary stability of implants in the lateral maxillary area, a bone thickness of minimum 4 mm is necessary, but often additional osteoplastic operations are required. Regarding this, several sinus lift techniques are known. In this case, the use of an implant stabilizer made of resorbable synthetic material reduces the operation invasivity. For this purpose, a polylactate implant stabilizer with appropiate shape and function has been developed. The following material's characteristics, such as the material's hydrolysis, the reduction of the molecular weight and the mechanical retention on the implant have been analysed in vitro. Hydrolysis has been performed following ISO/TC 150 SC 1 standard, and its effects have been documented by SEM images and illustrated with degradation curves. The mechanical properties are defined by the stabilizer's traction forces in the direction of the implant shaft. Before hydrolysis, the median traction force is 118 [N], one month after, it is reduced to 94 [N] and three months after hydrolysis, the complete absence of any retention force is achieved. The stabilizer has been inserted in the subperiostal tissue of a Goettingen mini pig's frontal bone. Four months later, the material has been removed. The presented histological preparation shows the osteo-inductive properties of the stabilizer. Keywords: resorbable, implant stabilizer, sinus lift

The clinical use of AO/ASIF 1.5 and 2.0 self-drilling screw (Synthes)were evaluated in different locations and indications in the craniomaxillofacial area. The handling and fixation properties and torque measurements in bone of different thickness and quality were evaluated with 334 screws in 28 patients. Ease of insertion without previous drilling.Insertion torque was increased compared to self-tapping screws. Torque measurements 6 months after insertion demonstrated good anchorage of the self-drilling screws similar to the self-tapping screws. Miniplate osteosynthesis and the fixation of bone grafts using self-drilling screws proved to be reliable. Although in dense cortical bone of 3-4 mm in thickness the use of self-drilling screws may be limited, in our opinion the excellent clinical results in the craniofacial region will result in a broad acceptance within craniomaxillofacial surgery. Keywords: craniomaxillofacial surgery, self-drilling, bone screws

In 15 patients undergoing intraoral surgery the colonization of different surgical suture materials with oral bacteria was testet. Culturing removed sutures of defined length and weight showed a mean of 108 CFU of aerobic and anaerobic bacteria in Monocryl® and Deknalon® as well. The predominance of anaerobe pathogens (Prevotella intermedia, Fusobacterium nucleatum, Peptostreptococcus micros) suggests a relevance of suture colonization as a potential risk for wound infection. Early removal of suture materials is recommended. Keywords: surgical suture, colonization, oral bacteria, wound infection