Development of a static and dynamic simulator for osteosyntheses of the mandible.

The development of new methods and materials for osteosynthesis requires in vitro testing prior to clinical use to exclude major problems or difficulties. In the field of oral and maxillofacial surgery no standardized testing procedures have so far been established. From a biomechanical point of view the lower jaw can be described as a lever that during the chewing cycle various forces at various points of the bone act upon. Standardized solid foam polyurethane mandibles (Sawbones, Malmö, Sweden) were used for the testing of various types of screws and different types of fractures. Via linkages that were connected to hydraulic cylinders defined forces were exerted on the polyurethane mandibles and the deformation was registered depending on the force. Monitoring was carried out contactless and therefore without back coupling by the use of a video system that recorded well-defined points on both sides of the fracture line. The photographs were then evaluated by special software (SIMI MOTION CAPTURE). The control of the cylinders was performed through a processor that besides static forces also allowed dynamic testing (e.g. sinusoid oscillation with defined amplitude and number of cycles). For the standardized and realistic three-dimensional static or dynamic testing of new methods and materials for osteosynthesis of the lower jaw this test stand has proved to be optimally suitable. Independent on the type of fracture and the material used the field of application for our test stand is the complete lower jaw. Therefore an ethically correct and economically reasonable testing of industrial products and clinical methods of osteosynthesis can be performed with this simulator.

Synthetic, pure-phase beta-tricalcium phosphate ceramic granules (Cerasorb) for bone regeneration in the reconstructive surgery of the jaws.

The aim of this study was to investigate the long-term effect of the ceramic beta-tricalcium phosphate (beta-TCP) at different sites of alveolar reconstruction and to evaluate its properties. From 1997 to 2002, beta-TCP was implanted as bone substitute in 152 patients using a standardized study protocol. Main indications were the filling of large mandibular cysts (n=52), secondary and tertiary alveolar cleft grafting (n=38), periodontal defects (n=24) and maxillary sinus floor augmentation (n=16). For defects exceeding 2cm in diameter, beta-TCP was combined with autologous bone taken from the retromolar area, the maxillary tuberosity or the chin region. A radiological, clinical and ultrasonographical examination was carried out 4, 12 and 52 weeks postoperative. In 16 cases, biopsies were taken after 12 months indicating complete bony regeneration. While wound-healing disturbances occurred in 9.2% of cases, partial loss of the bone substitute material was found in 5.9%, while total loss occurred in only 2%. Complete radiological replacement of beta-TCP by autologous bone was found after approximately 12 months, indicating its osteoconductive properties. Because of its versatility, low complication rate and good long-term results, synthetic, pure-phase beta-TCP is a suitable material for the filling of bone defects in the alveolar region.

[Small fragment screws vs. plate osteosynthesis in condylar head fractures]. / Kleinfragmentschrauben vs. Plattenosteosynthese bei Gelenkwalzenfrakturen. Vergleich funktioneller Ergebnisse mit MRT und Achsiographie.

AIMS: This prospective study evaluates the outcome after osteosynthesis of condylar head fractures using 1.7 mm small fragment screws (2/2000 ff), which were selected according to a previous biomechanical trial to optimize condylar head traumatology. Clinical and functional results were compared to a group of fractures fixed mainly by mini- and microplates (1993-2000) and to a control group after conservative therapy with early functional training. PATIENTS AND METHODS: Functional values (axiography and MRI) regarding loss of vertical height, disk mobility, protrusive and translatory movements were assessed (a) in 34 of 83 condylar head fractures (groups V and VI according to Spiessl and Schroll, 22/69 subjects) managed by osteosynthesis with 1.7-mm small fragment screws (KFS), (b) a reference group (43/84 subjects) fixed mainly by mini- or microplates (PLO), comprising 56 of 101 fractures (1993-2000), and (c) 16 condylar head fractures after conservative therapy with early functional training (KT) as a control. RESULTS: In cases of small fragment screws, loss of vertical height (0.3 mm) was significantly reduced (p<0.01) in comparison to PLO (1.6 mm) and KT (6.9 mm). Disk mobility in KFS reached 90% of the non-fractured sides (NFS), thus clearly superior (p<0.01) to PLO (63% of NFS) and KT (40% of NFS). Translatory movements after KFS showed better results, too (p<0.05), with mediotrusion 84% and protrusion 80% of NFS. After PLO, mediotrusion was 62%, protrusion 71% of NFS, whereas KT showed only 53% (mediotrusion) and 56% (protrusion) of NFS. High-grade limitations of translatory movements presented in about 30% after PLO and <10% in KFS (p<0.01). Fragment displacements were found in <5% after small fragment screws, and in the plate osteosynthesis group in 15% (p<0.01). CONCLUSIONS: Due to better stability and reduced articular scarification osteosynthesis with 1.7-mm small fragment screws in condylar head fractures showed clearly superior functional results compared to mini- and microplates, and to conservative therapy.

[The prognostic importance of urinase type plasminogen activators (uPA) and plasminogen activator inhibitors (PAI-1) in the primary resection of oral squamous cell carcinoma]. / Prognostische Bedeutung des Plasminogenaktivators vom Urokinasetyp (uPA) und des Plasminogenaktivator-Inhibitors (PAI-1) beim primär resezierten Plattenepithelkarzinom der Mundhöhle.

This article examines the prognostic importance of urinase type plasminogen activators (uPA) and of plasminogen activator inhibitors (PAI-1) in cases of primary oral squamous cell carcinoma. Tissue samples were taken from the core of the tumour in 58 such primary surgical patients. The levels of uPA and PAI-1 were determined using ELISA. Statistical significance was calculated using the chi2- and log-rank tests. The mean follow-up (n=58) was 23 months. In order to determine prognostic value, the time before relapse was used. The mean time before relapse was 19 months. A total of 28 (40%) patients relapsed (local n=13, lymph node n=3, local and lymph node n=1, lymph node and skin n=1, other locations n=5). Such patients had significantly raised uPA (P<0.012) and PAI-1 (P<0.014) levels in the primary tumour. A optimal cutoff value for uPA (4.58 ng/mg) and PAI-1 (106.3 ng/mg) was determined using the multiple log-rank test. There was no significant correlation for patients with low or high levels (i.e. lower or higher than the cutoff value, respectively) with the usual clinical parameters such as localisation, N-stage, T-stage, differentiation and residual tumor status. Older patients (>58 years) had significantly higher levels of uPA and PAI-1 (P<0.017 and P<0.02, respectively). The likelihood of relapse was significantly higher in patients with high levels (uPA P<0.009, PAI-1 P<0.008). If the patients were divided into three groups depending on uPA and PAI-1 levels (group 1: uPA and PAI-1 low, n=35; group 2: uPA or PAI-1 high, n=12; group 3: uPA and PAI-1 high, n=11), relapses were more common in group 3 than in groups 1 or 2 (P<0.023). Patients with only surgical therapy (n=29) and those with postoperative radiotherapy (n=29) were used to evaluate postoperative follow-up. Cutoff levels were calculated for both groups. In the surgical therapy group this was uPA=5.63 ng/mg and PAI-1=106.3 ng/ml and in the surgical therapy plus radiotherapy group uPA=4.13 ng/mg and PAI-1=97.02 ng/mg. Kaplan-Meier curves showed a marked tendency for patients with higher levels to relapse more often. This is significant for surgical patients for PAI-1 (P<0.01) and for radiotherapy patients for uPA (P<0.04)

[Comparison of urokinase type plasminogen activators (uPA) and plasminogen activator inhibitors (PAI-1) in primary resection of oral squamous cell carcinoma]. / Vergleich des Plasminogenaktivators vom Urokinasetyp (uPA) und des Plasminogenaktivator-Inhibitors (PAI-1) mit klinischen Parametern beim resezierten Plattenepithelkarzinom der Mundhöhle.

This article examines the distribution and prognostic importance of urinase type plasminogen activators (uPA) and of plasminogen activator inhibitors (PAI-1) in cases of primary oral squamous cell carcinoma. Tissue from the primary tumor was taken from 79 patients. In order to make an intra-individual comparison, tissue from the healthy mucous membrane of the mouth was taken from 50 patients and metastatic tissue from lymph glands in the neck from 16 patients. The content of uPA and PAI-1 was determined using ELISA. After follow-up, 58 patients with primary surgical therapy were included. Statistical evaluation was carried out using the Kruskal-Wallis test, the Mann-Whitney U-test and the Wilcoxon test. Pearson's product moment correlation was used to determine the relationship between uPA and PAI-1 levels. The median uPA value was 3.43 ng/mg in primary tumor, and for PAI-1 47.1 ng/mg ( n=79). There was a significant correlation between uPA and PAI-1 both in the cancerous as well as the healthy tissue ( P<0.01). The intra-individual comparisons showed uPA and PAI-1 differed significantly between cancerous and healthy tissue ( P<0.0001) with the mean uPA and PAI-1 values being nine times higher in the cancerous tissue ( n=58). The correlation for between uPA and PAI-1 in tumors, healthy tissue and metastatic lymph node tissue ( n=16) showed highly significant values in the tumors ( P<0.001). The comparison between cancerous tissue in the primary tumor and the lymph nodes was not significant for PAI-1. For uPA, the values in the lymph nodes were significantly lower ( P<0.049). There were also significantly higher levels in metastatic lymph node tissue compared with healthy mucous membrane ( P=0.005 for uPA and P=0.003 for PAI-1). There was no significant correlation of PAI-1 and uPA ( n=79) with the patient's sex, size of the tumor (T stage), nodal status (N stage), differentiation (grade), or residual tumor status. If the patients were divided into two groups (< or =58 years and >58 years), the older patients had higher uPA ( P<0.017) and PAI-1 ( P<0.02) levels. The was no significant association between tumor localisation and uPA content in the tumor; for PAI-1 the association was significant ( P<0.02) in the individual areas of the mouth. A total of 23 (40%) patients relapsed (local n=13, lymph node n=3, local and lymph node n=1, lymph node and skin n=1, other locations n=5). Such patients had raised uPA ( P=0.012) and PAI-1 ( P=0.014) levels in the primary tumor. The high variability of the normal clinical parameters in tumors only has a limited prognostic value because it is not taken into account in individual cases. Thus determination of the PAI-1 level directly after surgery could provide an indication of the likelihood of a relapse and thus aid in determining the adjuvant therapy. This confirms a trend in that tumor associated proteases can also play a key role in oral squamous cell carcinoma as new, independent, prognostic factors. Whether or not uPA and PAI-1 will play such a role will be determined in additional multicentre clinical studies.

[Stability of osteosyntheses for condylar head fractures in the clinic and biomechanical simulation]. / Stabilität der Osteosynthese bei Gelenkwalzenfrakturen in Klinik und biomechanischer Simulation.

BACKGROUND: Fractures of the condylar head are traditionally managed by closed techniques, despite a considerable rate of dysfunctional problems. PDS pin osteosynthesis (presented by Rasse 1992) via a preauricular approach failed to become established as a standard procedure due to a lack of stability. Alternatively, mini- or microplating, as performed in our patients (101 condylar head fractures between 1993 and 2000), showed high-grade limitations of translatory movements in about 30% due to scarification after loosening of osteosynthesis materials. The aim of this study was to establish an efficient procedure for achieving a functionally stable and atraumatic osteosynthesis. METHODS: For the definition of a suitable procedure, models of the mandible (standardized fractures, types A, B, and C) were osteosynthesized (six samples for each type of fracture and type of screw), each with three PDS pins, 2.0 mm resorbable, 2.0 cortical, 1.7 and 1.2 mm small fragment screws, and exposed to increasing loads in centric (0-20-35 mm opening) and eccentric (35 mm opening) condylar positions. A computerized biomechanical test stand allowed a dynamic simulation of chewing forces (16 hydraulic drives). The resulting fracture gaps were measured without contact by a motion capture system. RESULTS: Within physiological limits, only 1.7 small fragment and 2.0 mm cortical screws were able to bear occlusal loadings up to 200 N (1.2 mm small fragment screws up to 150 N, resorbable 2.0 mm screws up to 100 N, and PDS-pins up to 50 N). In a pullout experiment (condylar spongious bone of young pigs, aged 4-6 months), 1.7 mm small fragment screws showed superior retention. A consecutively developed small fragment screw-system has been applied clinically in 74 condylar head fractures (58 patients). After removal of osteosynthesis material, 41 of 49 TM joints have so far shown complete restitution. CONCLUSIONS: The newly developed osteosynthesis system using a retroauricular approach based on 1.7 mm small fragment screws makes maxillomandibular immobilization unnecessary. The extra-articular position of the screw heads prevents scar-induced articular limitations. Preexisting degenerative alterations of the TMJ soft tissues, however, will affect functional results adversely.

[Condylar reconstruction after resection of an intracapsular stomach carcinoma metastasis]. / Kollumrekonstruktion nach Resektion einer intrakapsulären Magenkarzinommetastase.

BACKGROUND: The mandible is a very uncommon place for a metastasis of a gastric carcinoma. Normally the area of the temporomandibular joint (TMJ) remains unaffected. The separate vascularization is discussed as one reason among others. Primary reconstruction after resection of the condyle is often problematic because an early onset of adjuvant systemic therapy is required. In this case, the insertion of a Quinn joint prosthesis is presented after resection of a TMJ metastasis. CASE: We report a hematogenic metastatic gastric adenocarcinoma in a 51-year old male who initially presented with increasing disclusion in the left molar region. Suspecting a metastatic adenocarcinoma of the TMJ, a condylectomy with immediate replacement by a total joint prosthesis was performed via a preauricular approach. Corresponding to the clinically and radiologically suspected diagnosis, the decalcified histological specimen presented as a metastatic gastric adenocarcinoma within the intracapsular region. RESULTS: The healing period of the implanted modified Quinn prosthesis was fast and uncomplicated after resection of this, to our knowledge, first documented metastatic gastric adenocarcinoma of the intracapsular region. After early restoration of joint function and patient satisfaction, the required radiochemotherapy of further unresectable bony metastases could be started in time. DISCUSSION: This example of an extremely rare case of a metastasis shows that such a total joint prosthesis appears to be a very good alternative to extended autogenous reconstruction or an unsatisfactory primary resection. Due to the mating of the spherical condylar head and glenoid fossa, the modified Quinn prosthesis is very suitable for total joint replacement after extended resection or in multiply preoperated cases.

[Differential and common characteristics of patients with atypical facial pain and craniomandibular dysfunction]. / Differenzielle und gemeinsame Merkmale bei Patienten mit atypischem Gesichtsschmerz und kraniomandibularer Dysfunktion.

BACKGROUND: Craniomandibular disorders (CMD) and atypical facial pain (AFP) represent a clinical challenge. Whereas CMD patients respond to somatic approaches, somatization should be strictly avoided in AFP. The aim of this study was to establish prognostic criteria to identify an aggravated risk of a chronic course in CMD and AFP. METHOD: A total of 124 consecutive patients with CMD ( n=108) or AFP ( n=16) were examined by two interdisciplinary academic pain centers. Psychometric evaluation was conducted with standardized questionnaires (SCL-90R, STAXI, modified SBAS-IV). All patients were clinically assessed by a maxillofacial surgeon or specialized dentist. RESULTS: The following variables proved to be significant: age (risk for AFP vs CMD increased by 6% p.a.), decreased dysfunction index (13% higher risk for AFP vs CMD), and low scores concerning outwardly directed anger (12% higher risk for AFP vs CMD). There was no correlation between initial pain intensity and somatic parameters of disease as assessed by the standardized clinical examination. Low educational status proved to be the best predictor ( p<0.001) for patients presenting high initial pain with a marked discrepancy between somatic findings and subjective status. CONCLUSIONS: CMD patients differ from AFP patients regarding age, psychosocial isolation, outwardly directed anger, and a decreased dysfunction index. Additionally, initial pain intensity in patients presenting indistinct CMD/AFP can be considered as a valid predictor for a chronic course in pain.

Speech evaluation and swallowing ability after intra-oral cancer.

In this study, four methods of postoperative speech evaluation are compared for 19 persons with oral cancers who have undergone oral surgery and/or radiotherapy. The Munich Intelligibility Profile was used for intelligibility testing and semiquantitative scoring by novice listeners. Expert ratings were done on the Therapy Outcome Measure (TOM) Phonological Disability form. For self-evaluation, the EORTC QLQ-C30 and the Head and Neck module was used. Swallowing function was scored on the TOM Dysphagia form. There was a high intercorrelation between the results of subjective speech evaluation by experts and non-experts and the intelligibility test, but no correlation with any of these methods could be shown for the self-evaluation by the participants. Voice quality seemed to have an influence on non-expert scores. Swallowing was a more severe problem for our group than speech impairment.

[Experimental endoscopic intrauterine surgery for craniofacial malformations such as the cleft lip and palate]. / Tierexperimentelle endoskopische intrauterine Chirurgie bei kraniofazialen Fehlbildungen am Beispiel der Lippen-Kiefer-Gaumen-Spalten.

INDICATION FOR FETAL SURGERY: The widespread use of high-resolution ultrasound in prenatal diagnosis allows nowadays an accurate and early diagnosis of congenital malformations. Some of these can be corrected surgically. In certain cases intrauterine surgery could present functional and aesthetic advantages or be even lifesaving. Due to the extreme sensitiveness of the fetal patient and the fetal membranes, only some defined anomalies currently meet the criteria for intrauterine surgery. However, the list can change in the future since prenatal diagnosis, technical advances, and knowledge of pathophysiology improve constantly. ENDOSCOPIC INTRAUTERINE SURGERY: Additionally, the recent development of endoscopic intrauterine surgery represents a new and more careful possibility for intrauterine surgery. Endoscopic procedures could avoid the disadvantages of open intrauterine surgery and thus make fetal operations safer, in life-threatening as well as in non-life-threatening malformations such as cleft lip and palate (CLP). The main advantages of these procedures are (1) scarless wound healing and bone healing without callus formation that leave to expect normal growth of the midface and (2) lower fetal and maternal morbidity. DISCUSSION: Based on the results achieved until now, it can be stated that at present the intrauterine operation of CLP on humans cannot be recommended. The high morbidity and mortality risk for mother and fetus cannot be counterbalanced by the unsatisfactory results of a prenatal operation. CONCLUSION: In this study first results of an experimental investigation with the new endoscopic techniques are presented, whereby the possibilities for optimization and quality improvement of the intrauterine surgical procedures are analyzed in detail.

Investigation on plasma immersion ion implantation treated medical implants.

In this work the biocompatibility of osteosynsthesis plates treated with plasma immersion ion implantation (PIII) was tested using a rat model. Small rods (Ø 0.9 mm, and length 10 mm) prepared from different materials-pure Ti, anodised Ti, and two NiTi alloys (SE 508, and SM 495)-were implanted with oxygen by PIII to form a rutile surface layer and subsequently inserted into rat femurs, together with a control group of untreated samples. The results of the biomechanical tests correlate with the histological results, and show that plasma immersion ion implantation leads to an increase of biocompatibility and osseointegration of titanium and NiTi, albeit no improvement of the (bad) biocompatibility of the anodised Ti. Despite the layer thickness of up to 0.5 microm a strong influence of the base material is still present.

[Surgical vs. conservative therapy of diacapitular and high condylar fractures with dislocation. A comparison between MRI and axiography]. / Operative vs. konservative Therapie diakapitulärer und hoher Kollumluxationsfrakturen. Vergleich mit MRT und Achsiographie.

AIMS: At present the discussion about the correct management of high condylar and diacapitular fractures has been reopened. The aim of the present prospective study was to evaluate the role of condylar mobility, disk mobility, and vertical dimension regarding the postoperative functional outcome after open reduction and osteosynthesis compared to nonsurgical treatment. METHODS: Since 1993 a total of 130 high condylar and diacapitular fractures have been treated by open reduction and osteosynthesis. Thirty-nine subjects with 51 fractures classes V and VI according to Spiessl and Schroll (surgical treatment, ST) were assessed postoperatively (mean 24 months) including magnetic resonance imaging (MRI) and axiography. Sixteen conservatively treated fractures served as a reference (conservative treatment, CT). RESULTS: Surgically treated temporomandibular joints presented a better condylar mobility (11.4 mm after ST, 5.9 mm after CT) and a less remarked loss of vertical ramus height (1.6 mm after ST, 5.4 mm after CT). Conservatively treated high condylar fractures formed a nearthrosis with the articular eminence in an anteromedial malposition (x axis 6.9 mm, y axis 10.3 mm). Disk mobility was reduced in both groups (3.8 mm after CT, 5.8 mm after ST), with major interindividual variations after ST. Significant correlations were found in the surgically treated group between axiographic limitations and limitations of disk mobility (p < 0.01) or periarticular scar formations (p < 0.01). Helkimo indices after ST (31% symptom free, 67% light symptoms < 5 points) were clearly superior (p < 0.01) to conservative treatment, with 63% of the subjects presenting craniomandibular symptoms > 5 points. CONCLUSIONS: According to the functional results observed, high condylar and diacapitular fractures will profit by open reduction and osteosynthesis. Only effective surgical procedures can preserve both disk mobility and vertical ramus height.

[Speech outcome after simple and multiple cleft palate operations]. / Sprechsprachliche Ergebnisse nach einfachen und mehrfachen Gaumenverschlussoperationen.

OBJECTIVES: If the primary palatal closure in a patient with cleft lip and palate is unsuccessful, defects such as palatal fistulas and a short velum have to be corrected by secondary operations. It is an informal belief among surgeons that these reoperations can have detrimental effects on the patients' nasal resonance and articulation. It was our aim to critically evaluate the validity of this belief. MATERIAL AND METHODS: One hundred and twenty-four patients with cleft lip and palate were divided into three groups. The 70 patients in group 1 had only undergone a primary palatal closure operation. The 33 patients in group 2 had undergone one or more palatal reoperations. The 21 patients in group 3 had undergone an additional pharyngeal flap operation. Resonance and articulation were evaluated perceptually. Nasalance was assessed with the NasalView system, and the mean speech rate was analyzed with the MODIAS software. RESULTS: There were no significant differences for any of the speech measures between groups 1 and 2. Patients in group 3 had significantly worse results for all speech measures. CONCLUSIONS: The speech outcomes for patients with multiple palatal reoperations were no different from those of patients with single palatal closure operations. The pharyngeal flap operation did not lead to sufficient improvements in the speech of the patients in group 3.

Peri-implant care of ailing implants with the carbon dioxide laser.

One of the many applications for which lasers have been proposed in implant dentistry is for the decontamination process. The purposes of this study were to assess possible alterations in titanium implants in vitro and in vivo by use of the carbon dioxide (CO2) laser and to determine whether new bone formation can occur on previously contaminated implants. In vitro, temperature changes at the bone-titanium implant interface were recorded during use of a CO2 laser-scanning system (Swiftlase). Additionally, the effects of laser irradiation on titanium implants at various power settings were examined. In 6 beagle dogs, a total of 60 implants and bony defects resulting from plaque accumulation were treated by air-powder abrasive (the conventional treatment), laser irradiation, or both. Depending on the parameters chosen, melting and other surface alterations were seen in vitro, especially in the superpulse mode. Otherwise, no alterations were found, even at high power settings in the continuous mode. In vivo, corresponding histologic examination of 4-month sections showed evidence of new direct bone-to-implant contact after laser-assisted therapy, especially when the implants had been treated concomitantly with submerged membranes. These results support the hypothesis that peri-implant defects can be treated successfully by laser decontamination without damaging the surrounding tissues in the dog model. Nevertheless, further investigations will be required to determine the clinical efficacy of the treatment.

Levatorplasty, a new technique to treat hypernasality: anatomical investigations and preliminary clinical results.

BACKGROUND: Velopharyngoplasty is the most commonly used operative technique for the treatment of velopharyngeal insufficiency. By attaching a posterior pharyngeal flap to the velum, a nonphysiological situation is created in the upper airway. PURPOSE: The aim of this investigation was to find a new surgical approach to physiological reconstruction of the velopharyngeal sphincter. MATERIAL: Anatomical investigations were performed in four cadavers. From this study a new surgical technique was developed and called 'levatorplasty': the musculus longus capitis was taken to create a new muscular loop leading to (a) an augmentation of the posterior wall, (b) a medial shift of the lateral pharyngeal wall; and (c) stretching of the velum posteriorly. Thus, the velopharyngeal space was reduced and a physiological closure of the nasal airway space could be obtained. STUDY DESIGN: The levatorplasty was employed in nine cleft palate patients with velopharyngeal insufficiency. Pre- and postoperatively the velopharyngeal closure was evaluated by phonetic and radiological examination. RESULTS: The operation was easily performed without major complications. A concentric constriction with decrease of the velopharyngeal space was achieved and a definitive decrease of nasalance and hypernasality resulted. CONCLUSION: Long-term follow-ups have to verify whether these results will be stable. They also have to be compared with functional improvements following velopharyngoplasty or pharyngoplasty. Of special interest will be evaluation of the altered mobility of the lateral pharyngeal walls.

[Stress analysis of the human mandible in standard trauma situations with numerical simulation]. / Spannungsanalyse des menschlichen Unterkiefers bei traumatologischen Standardsituationen mittels numerischer Simulation.

For the stress analysis of the human mandible a flexible simulation concept basing on finite element-method has been developed. One of the main issues is the prediction of fractures as a consequence of known forces as well as the forensic reconstruction of the traumatologic situation. At first, the individual geometry was reconstructed by 3D-CT-Scans. To reduce the simulation efforts, for the time being the anisotropic structural mechanics of the jaw bone was neglected in favour of an homogeneous and isotropic material law. Assuming the Von-Mises-Stress as a failure indicator the results of the simulations were in good agreement with typical traumatologic situations. For further validation of the model, a real failure case, shown on a radiograph of a injured human mandible with three fractures, was simulated and, by this, the real incident was reconstructed. Reasonable planned extensions of the actual simulation concept have the regard on the nerve channel, the temporomandibular joint's function, the paradontal apparatus and the individual mechanical properties of the bone.

[Numerical simulation (FEM) of the human mandible: validation of the function of the masticatory muscles]. / Numerische Simulation (FEM) des menschlichen Unterkiefers: Validierung der Umsetzung der Kaumuskulatur.

The article describes part of a research project aiming to develop a new modular software tool for the individual dynamic numerical simulation of the human mandible using the finite element method (FEM). Its planned use in the clinical setting makes it very important to validate the results of the simulations. Here, the function of the masticatory muscles is to be tested. On the basis of biomechanical data from the literature, standard movements, such as closing the mouth, forward movement, lateral movement or backward movement, were dynamically simulated. Apart from muscle activity, the movements of the mandible are defined by the temporomandibular joint. At present, translating the condylar dynamics to the simulation still poses problems. For this reason, therefore, simulations of the two extreme cases "fixed" and "force-free" condyles are compared. While in the case of fixed condyles, some of the movements could be reproduced either not at all or only weakly, in the case of force-free condyles, all standard movements were reproduced qualitatively, albeit without the guiding effect of the joint capsule or the articular disc.

Nasalance distance and ratio: two new measures.

OBJECTIVES: Mean nasalance in speakers with perceptually normal nasal resonance can differ in magnitude considerably. In addition, categorizations of speech based on nasalance scores may not agree with perceptual judgments. To overcome this limitation, we evaluated two new simple measures derived from mean nasalance data: the nasalance distance (range between maximum and minimum nasalance) and the nasalance ratio (minimum nasalance divided by maximum nasalance). SETTING: Department of Oral and Maxillofacial Surgery, University of Technology, Munich, Germany. SUBJECTS: The sample consisted of 133 cleft lip and palate patients with normal nasal resonance or varying degrees of hypernasality. PROCEDURES: Oral and nasal acoustic measurements were made using the NasalView system. Nasalance distance and nasalance ratio were calculated for five non-nasal and three nasal sentences from the modified Heidelberg Rhinophonia Assessment Form. RESULTS: Optimum cutoffs were derived from receiver-operating characteristics. Results for the sentence stimuli ranged from 64.4% to 89.6% sensitivity and from 91.2% to 94.1% specificity. When the analysis was limited to only one nonnasal and one nasal sentence, results ranged from 79.7% to 87.5% sensitivity and from 88.2% to 97.1% specificity. CONCLUSIONS: We conclude that the two new measurements are valuable in routine clinical examinations. Nasalance distance and ratio derived from sentence stimuli are two useful and easily applicable measures that can be used to supplement the nasalance mean value.

[A modular software concept for individual numerical simulation (FEM) of the human mandible]. / Ein modulares Software-Konzept für individuelle numerische Simulation (FEM) des menschlichen Unterkiefers.

A new modular software concept for individual numerical simulation of the human mandible using the finite element method (FEM) is presented. The main task is an individual analysis of regional stress and stress-compatibility on the basis of computed tomographic data in individual patients. Simulation should, however, also be possible in parallel with biomechanical experiments, or for further research projects. For this purpose, rapid and uncomplicated generation of the FEM model, easy modification of input data, and short computation times are required. Practical use in the clinical setting makes appreciable additional demands on the individual software components.

[Position and mobility of the articular disk after surgical management of diacapitular and high condylar dislocation fractures of the temporomandibular joint]. / Position und Beweglichkeit des Discus articularis nach operativer Versorgung diakapitulärer und hoher Kiefergelenkluxationsfrakturen.

Magnetic resonance imaging (MRI) assessment of traumatized temporomandibular joints (TMJ) usually focuses on disc position, defining regular joint function by normal, excentric or displaced disc position. So far, there are only few reports regarding disc position after open reduction of diacapitular or high condylar fractures of the TMJ with dislocation. The aim of the present study was to evaluate the role of the disc as regards postoperative functional outcome by electronic axiographic recordings of condylar movements and MRI, displacement of the disc and lesions of TMJ soft tissues being frequent in this type of mandibular fractures. A total of 30 subjects with 37 condylar fractures in whom osteosynthesis was performed using a preauricular approach were imaged postoperatively (mean 24 months) with a 1.5-Tesla MRI system to determine, (a) the position of the disc, (b) the range of mobility of the disc and (c) condylar mobility in closed and open mouth position, comparing fractured sides (FS) vs nonfractured sides (NFS). Linear movements between the two jaw positions in the sagittal plane were measured by superimposing transparencies. The results indicate: (1) more than 70% of the discs (FS) were found to be in normal position; there was no disc displacement without reduction. However, these data stood in contrast to severe limitations of the axiographic tracings as presented by almost 30% of the subjects. (2) Significant correlations were found between fixed (alpha = 0.05) or highly immobilized (alpha = 0.01) discs and axiographic limitations, suggesting disc mobility to be a valuable parameter for assessment of the postoperative functional outcome.