Biomedical subjects

R Sader

Publications and source records attributed to R Sader.

At least 19 recordsLinked to original sources

PubMed2006

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.

Adolescent↗

PubMed2006

Three-dimensional recording of the human face with a 3D laser scanner.

Three-dimensional recording of the surface of the human body or of certain anatomical areas has gained an ever increasing importance in recent years. When recording living surfaces, such as the human face, not only has a varying degree of surface complexity to be accounted for, but also a variety of other factors, such as motion artefacts. It is of importance to establish standards for the recording procedure, which will optimise results and allow for better comparison and validation. In the study presented here, the faces of five male test persons were scanned in different experimental settings using non-contact 3D digitisers, type Minolta Vivid 910). Among others, the influence of the number of scanners used, the angle of recording, the head position of the test person, the impact of the examiner and of examination time on accuracy and precision of the virtual face models generated from the scanner data with specialised software were investigated. Computed data derived from the virtual models were compared to corresponding reference measurements carried out manually between defined landmarks on the test persons' faces. We describe experimental conditions that were of benefit in optimising the quality of scanner recording and the reliability of three-dimensional surface imaging. However, almost 50% of distances between landmarks derived from the virtual models deviated more than 2mm from the reference of manual measurements on the volunteers' faces.

Adult↗

PubMed2006

[Lip, jaw, and palate clefts. Analysis of unilateral cleft lip using 3-D laser topometry].

INVESTIGATION: In most cases it is not sufficient to use photographs and plaster casts to document and analyze the three-dimensional morphology of lip, jaw, and palate clefts. The aim of this study was to evaluate the applicability of surface scanning with a 3-D laser topography scanner in patients with unilateral cleft lip. PATIENTS AND METHODS: Three-dimensional surface scans of the face were performed pre- and postoperatively in 20 patients (3-35 years of age) with a 3-D laser topography scanner. All patients were suffering from nonoperated, one-sided cleft lip, cleft lip-jaw, or cleft lip-jaw and palate. The digital data sets were metrically analyzed and expressed on the basis of quotients, independent of size factors. RESULTS: Using this 3-D laser scanner it was possible to acquire good quality three-dimensional data sets. Measurements were in the dimension of millimeters. Based on the data sets it was possible to provide the three-dimensional cleft morphology with reproducible landmarks and analyze the data. The postoperative symmetry of the face was controlled and objectively quantified. It is disadvantageous however that numerous views need to be taken to get the full image of the face and that the scanning process takes about 2 s. CONCLUSION: The presented 3-D laser scanner renders a precise 3-D surface analysis of the lip and nose region in cleft patients. For lively infants or uncooperative adults, the system is suitable only to a limited extent due to the time-consuming scanning process.

Adolescent↗

PubMed2006

Consideration of anisotropic elasticity minimizes volumetric rather than shear deformation in human mandible.

This article is focused on the role of anisotropic elasticity in the simulation of the load distribution in a human mandible, due to a lateral bite on the leftmost premolar. Based on experimental evidence, orthotropy of the elastic properties of the bone tissue has been adopted. The trajectories of anisotropic elasticity are reconstructed from (i) the organ's geometry and (ii) from coherent structures which can be recognized from the spatial distribution of the grey values coming from computer tomography (CT). A sensitivity analysis comprising various three-dimensional (3D) finite element (FE) simulations reveals the relevance of elastic anisotropy for the load carrying behavior of a human mandible: comparison of the load distributions in isotropic and anisotropic simulations indicates that anisotropy seems to "spare" the mandible from loading. Moreover, a maximum degree of anisotropy leads to kind of load minimization of the mandible, expressed by a minimum of different norms of local volumetric strain, evaluated throughout the organ. The observed optimization with respect to volumetric rather than shear strain seems to confirm the frequently emphazised role of volumetric-strain-induced fluid flow for the stimulation of cellular activity.

Anisotropy↗

PubMed2006

Accuracy and precision of the three-dimensional assessment of the facial surface using a 3-D laser scanner.

Three-dimensional (3-D) recording of the surface of the human body or anatomical areas has gained importance in many medical specialties. Thus, it is important to determine scanner precision and accuracy in defined medical applications and to establish standards for the recording procedure. Here we evaluated the precision and accuracy of 3-D assessment of the facial area with the Minolta Vivid 910 3D Laser Scanner. We also investigated the influence of factors related to the recording procedure and the processing of scanner data on final results. These factors include lighting, alignment of scanner and object, the examiner, and the software used to convert measurements into virtual images. To assess scanner accuracy, we compared scanner data to those obtained by manual measurements on a dummy. Less than 7% of all results with the scanner method were outside a range of error of 2 mm when compared to corresponding reference measurements. Accuracy, thus, proved to be good enough to satisfy requirements for numerous clinical applications. Moreover, the experiments completed with the dummy yielded valuable information for optimizing recording parameters for best results. Thus, under defined conditions, precision and accuracy of surface models of the human face recorded with the Minolta Vivid 910 3D Scanner presumably can also be enhanced. Future studies will involve verification of our findings using test persons. The current findings indicate that the Minolta Vivid 910 3D Scanner might be used with benefit in medicine when recording the 3-D surface structures of the face.

Algorithms↗

PubMed2005

Computer aided surgical reconstruction after complex facial burn injuries -- opportunities and limitations.

In severe facial burn injuries with extensive destruction of anatomical structures, cosmetic and functional outcome of treatment are frequently not satisfactory. Although operative therapy is being continuously refined, the variety and proximity of structures in the facial region is considered a major challenge in reconstructive surgery. We present the case of a 16-year-old patient with a severe facial burn injury. In planning the reconstructive procedures, we used a multimodal approach employing data from computerized tomography imaging, as well as from surface laser scanning, which provided three-dimensional visualization of facial soft tissues. Amount and pattern of structural loss could thus be determined more precisely and studied more vividly than by inspection of two-dimensional imaging alone. Anatomical features to be reconstructed could be projected onto the skin area of the prelaminated vertical rectus abdominis muscle (VRAM) flap that has been chosen to cover the defect. Prior to surgery, correction of the defects was simulated and the results of the virtual procedure superimposed on a three-dimensional head model of the patient. Tissue elasticity and thickness of the flap, however, could not be ascertained in advance, indicating the limitations of the method.

Adolescent↗

PubMed2004

[MRT sequences as a database for a visual articulatory model].

Articulatory models can be used in phoniatrics for the visualisation of speech disorders, and can thus be used in teaching, the counselling of patients and their relatives, and in speech therapy. The articulatory model developed here was based on static MRI data of sustained sounds. MRI sequences are now being used to further refine the model with respect to speech movements. Medio-sagittal MRI sections were recorded for 12 consonants in the symmetrical context of the three point vowels [i:], [a:] and [u:] for this corpus. The recording-rate was eight images/s. The data show a strong influence of the vocalic context on the articulatory target-positions of all consonants. A method for the reduction of the MRI data for subsequent qualitative and quantitative analyses is presented.

Articulation Disorders↗

PubMed2003

[Condylar reconstruction after resection of an intracapsular stomach carcinoma metastasis].

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.

Adenocarcinoma↗

PubMed2002

[Speech outcome after simple and multiple cleft palate operations].

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.

Adolescent↗

PubMed2002

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.

Animals↗

PubMed2002

Surgery planning tools for the osseous grafting treatment.

This paper presents a method for computer assisted selection of optimal donor sites for autologous grafts in the craniofacial surgery planning. The method consists of two stages. The non-automatic graft design step is followed by a fully automatic procedure to find the best harvesting site in the predefined donor region. The main idea of the proposed method is based on the registration paradigm. The optimal donor site is identified by performing an optimization of the surface based similarity measure between the donor region and the designed graft template. An efficient optimization method based on the Levenberg-Marquardt algorithm has been implemented. It enables, once the preprocessing step has been performed, selection of the optimal donor site in time less than one minute.

Algorithms↗

PubMed2001

[Stress analysis of the human mandible in standard trauma situations with numerical 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.

Biomechanical Phenomena↗

PubMed2001

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.

Adolescent↗

PubMed2000

[A modular software concept for individual numerical simulation (FEM) of the human mandible].

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.

Biomechanical Phenomena↗

PubMed2000

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.

Adolescent↗

PubMed1999

[Quantitative diagnosis of hypernasality in cleft lip and palate patients by computerized nasal quality assessment].

In patients with cleft lip and palate (CLP), the assessment of velopharyngeal morphology and function and the quantitative analysis of perceptual consequences of velopharyngeal insufficiency are of major importance regarding the effective planning of velopharyngoplasties for speech improvement. The NasalView, a new instrument for the objective assessment of rhinophonia, is presented. The NasalView measures nasalance, the relative sound pressure level of the nasal signal in speech, expressed as a percentage. In order to evaluate the effectiveness of the computerised measurement of nasalance, 156 patients with surgically treated CLP were examined. The NasalView differentiated with high sensitivity and specificity between patients with normal nasal resonance and patients with varying degrees of hypernasality. To illustrate the importance of the NasalView for making the decision for a velopharyngoplasty, a single case is presented.

Adolescent↗

PubMed1999

[Significance of profile prognosis in implant management of the atrophic maxilla].

Postoperative cosmetic results in soft tissue after combined surgical and prosthetic treatment of the extremely atrophic edentulous maxilla by maxillary advancement, sinus lift, and insertion of enosseous implants are rarely considered during preoperative planning. In a prospective study that began in 1993 in 23 patients, the treatment concept was determined by a medical rapid prototyping model and video imaging to predict the soft tissue profile, taking into consideration the appearance of the front teeth. In eight patients, the surgical and/or the prosthetic concept was modified according to the treatment plan decided on with the patient. All patients were highly satisfied with the aesthetic and functional result achieved. Profile prediction using video imaging is a useful tool in planning rehabilitation of the atrophic maxilla and takes into account the interplay of various factors--the amount of maxillary advancement, the direction of insertion of enosseous implants, and the type of supraconstruction. This procedure shows a very high level of acceptance by patients.

Alveolar Bone Loss↗

PubMed1999

[Quality of life research in patients with cleft lip and palate: preliminary results].

While esthetic and functional outcomes of treatment have improved for patients with cleft lip and palate (CLP), a CLP remains a severe problem for patients and relatives. To date, psychological research has dealt with issues such as intelligence, self-consciousness or treatment satisfaction but the long-term impact of a CLP on a psychological construct such as quality of life has yet to be explored. From a pool of 156 patients with CLP, subgroups of varying sizes were examined with a set of standardized questionnaires (KINDL, SF-36, Social Support Survey). In all patients, primary operative treatment had been accomplished. Long-term impact of the CLP on family life was assessed by 112 of the patients' parents by filling in the Impact on Family Scale. A set of questionnaires, especially developed for patients with CLP, was administered as well. For all patients who have been being treated in an interdisciplinary cleft center for their entire life, the results presented indicate that quality of life is good and within a normal range. Social support appears to be within a normal range. Parents report only minor long-term impact of the CLP on family life and family planning. Treatment satisfaction is high in the CLP patients. The questionnaires especially aimed at CLP patients indicate more specific problems mainly concerning social acceptance, where patients think the CLP had a negative impact. The standardized questionnaires employed so far failed to capture these problems. The combination of the two types of questionnaires is a sufficiently sensitive assessment procedure.

Adolescent↗