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Biomedical subjects

R Ewers

Publications and source records attributed to R Ewers.

At least 19 recordsLinked to original sources
PubMed2005

Invitro study of adherent mandibular osteoblast-like cells on carrier materials.

Augmentation of the craniofacial region is necessary for many aesthetic and reconstructive procedures. Tissue engineering offers a new option to supplement existing treatment regimens. In this procedure, materials composed of hydroxyapatite (HA), of synthetic or natural origin, are used as scaffolds. The aim of this study was to evaluate the effects of three HA materials on cultured human osteoblasts in vitro. Explant cultures of cells from human alveolar bone were established. Human osteoblasts were cultured on the surface of HA calcified from red algae (C GRAFT/Algipore), deproteinized bovine HA (Bio-Oss) and bovine HA carrying the cell binding peptide P-15 (Pep Gen P-15). Cultured cells were evaluated with respect to cell attachment, proliferation and differentiation. Cells were cultured for 6 and 21 days under osteogenic differentiation conditions, and tissue-culture polystyrene dishes were used as control. The ability of cells to proliferate and form extracellular matrix on these scaffolds was assessed by a DNA quantification assay, protein synthesis analysis and by scanning electron microscopical examination. Osteogenic differentiation was screened by the expression of alkaline phosphatase. The osteoblastic phenotype of the cells was monitored using mRNA levels of the bone-related proteins including osteocalcin, osteopontin and collagen Type I. We found that cells cultured on C GRAFT/Algipore) and Pep Gen P-15 showed a continuous increase in DNA content and protein synthesis. Cells cultured on Bio-Oss showed a decrease in DNA content from Day 6 (P < 0.05) to Day 21 (P < 0.0001) and protein synthesis on Day 21 (P < 0.005). Alkaline phosphatase activity increased in cells grown on C GRAFT/Algipore and Pep Gen P-15 in contrast to cells grown on Bio-Oss, in which the lowest levels of activity could be observed on Day 21 (P < 0.05). Reverse transcriptase polymerase chain reaction analysis confirmed the osteoblastic phenotype of the cells grown on all three materials throughout the whole culture period. The results of our in vitro study show that the differences in metabolic activity of cells grown on HA materials are directly related to the substrate on which they are grown. They confirm the excellent properties of HA carrying the cell binding peptide P-15 and HA calcified from red algae as used in maxillofacial surgery procedures.

Alkaline Phosphatase↗
PubMed2005

Distraction osteogenesis with subperiosteal devices in edentulous mandibles.

Nine patients with severely atrophic edentulous mandibles were treated by distraction osteogenesis with subperiosteal distractors for vertical augmentation of the anterior alveolar bone before insertion of implants. All the patients had severe complications and we conclude that the use of subperiosteal devices for vertical augmentation of edentulous mandibles is hazardous and offers no advantage over other surgical methods.

Adult↗
PubMed2005

Basic research and 12 years of clinical experience in computer-assisted navigation technology: a review.

Computer-aided surgical navigation technology is commonly used in craniomaxillofacial surgery. It offers substantial improvement regarding esthetic and functional aspects in a range of surgical procedures. Based on augmented reality principles, where the real operative site is merged with computer generated graphic information, computer-aided navigation systems were employed, among other procedures, in dental implantology, arthroscopy of the temporomandibular joint, osteotomies, distraction osteogenesis, image guided biopsies and removals of foreign bodies. The decision to perform a procedure with or without computer-aided intraoperative navigation depends on the expected benefit to the procedure as well as on the technical expenditure necessary to achieve that goal. This paper comprises the experience gained in 12 years of research, development and routine clinical application. One hundred and fifty-eight operations with successful application of surgical navigation technology--divided into five groups--are evaluated regarding the criteria "medical benefit" and "technical expenditure" necessary to perform these procedures. Our results indicate that the medical benefit is likely to outweight the expenditure of technology with few exceptions (calvaria transplant, resection of the temporal bone, reconstruction of the orbital floor). Especially in dental implantology, specialized software reduces time and additional costs necessary to plan and perform procedures with computer-aided surgical navigation.

Computer Graphics↗
PubMed2005

Fixation of zygomatic fractures with a biodegradable copolymer osteosynthesis system: short- and long-term results.

Biodegradable osteosynthesis devices can be viewed as addition to, not yet replacement for conventional metal osteosynthesis materials. In a series of 65 patients with zygomatic fractures, a short-term complication/sequelae rate of 22.8% and a long-term complication rate of 9.4% were recorded. Lactosorb plates, panels and screws were the only devices used for osteosynthesis. All complications associated with the biodegradable material could be considered minor and were resolved by the use of minor surgical procedures or conservative measures. The results of this study indicate that treatment of zygomatic fractures with biodegradable osteosynthesis material has no major long-term adverse effects beyond the total material resorption time.

Absorbable Implants↗
PubMed2005

Preoperative radiochemotherapy and radical resection for stages II-IV oral and oropharyngeal cancer: outcome of 222 patients.

To analyse survival and locoregional control in patients with advanced oral and oropharyngeal squamous cell carcinoma (SCC) after multimodal therapy with preoperative radiochemotherapy (RCT) and radical surgery. We included in this analysis 222 patients who underwent multimodal therapy between 1990 and 2000. Eligible were patients with UICC disease stages II-IV (T2: 33.3%; T3: 12.6%; T4: 54.1%; N0: 45.9%; N1: 17.6%; N2: 33.3%; N3: 3.2%; stage II: 21.1%; stage III: 14.9%; stage IV: 64%). Patients received preoperative radiochemotherapy consisting of Mitomycin C (15-20 mg/m2, day 1) plus 5-Fluorouracil (750 mg/m2/24 h-infusion, days 1-5) and concomitant radiotherapy for a total dose of 50 Gy. Radical locoregional en bloc-resection according to the pretherapeutic tumour extension was carried out in all patients. After a median surveillance period of 72.3 months (24-152 months), 131 patients (59%) were alive, and 91 (41%) patients died; 12 (5%) of them died postoperatively, 46 (21%) due to tumour recurrence, and 33 (15%) deaths were not directly related to the primary tumour. Overall survival probability was 76% after 2 years, and 62% after 5 years. Two- and 5-year local control probability were 88 and 81%, respectively. Regarding the high percentage of stage IV disease in the reported patients, the multimodal concept is an effective therapy offering excellent survival and local control probability.

Antibiotics, Antineoplastic↗
PubMed2005

Preoperative radiochemotherapy and radical resection for stages II to IV oral and oropharyngeal cancer: grade of regression as crucial prognostic factor.

The purpose of this study was to assess the prognostic value of histological response to preoperative radiochemotherapy in an established multimodal therapy concept for advanced oral and oropharyngeal cancer. Two hundred and twenty-two patients who underwent preoperative radiochemotherapy (RCT: 50 Gy, mitomycin C and fluorouracil) and radical surgery were retrospectively evaluated. Resected tumours of all patients were histologically analysed and response to RCT was classified in histopathological grades of regression (RG). In a multivariate statistical analysis, RG was compared with established factors regarding their predictive value for overall and disease-specific survival. The 5-year overall survival probability in the different groups of histopathological regression grades were: RG1 (no vital tumour): 73.4%, RG2 (minimal tumour remnants encompassing less than 5%): 72.1%, RG3 (5-50% vital tumour cells): 41.9%, RG4 (more than 50% vital tumour): 37.9%. For disease-specific survival probability no significant differences were found between both groups of "responders" (RG1 and RG2) nor between "non-responders" (RG3 and RG4), whereas responders and non-responders differed significantly from each other (log-rank test; p < 0.001). T-classification, N-classification and disease stage, histological grading, tumour site, age, and sex had less prognostic value than RG in a Cox regression model. In the neoadjuvant multimodal therapy concept, histological response to preoperative RCT is a crucial prognostic factor even when surgical R0-resection is accomplished. Thus, non-responders have to be regarded as high-risk patients for recurrence and may benefit from further therapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2004

Conservative treatment of large cystic lesions of the mandible: a prospective study of the effect of decompression.

Our aim was to evaluate prospectively the effects of decompression as the primary treatment of large mandibular cysts, irrespective of their histological type. Twenty patients with large mandibular cysts completed treatment successfully. After a mean duration of decompression of 446 days, cysts had shrunk by a mean of 81%. Mean follow-up was 527 days after removal of the decompression stent and removal of the cyst. There were no recurrences. The advantages of this approach are simplicity, immediate gathering of information on the type of cyst with simultaneous start of treatment, low morbidity and low incidence of complications during treatment. Despite the length of the treatment, we recommend the use of decompression stents in the treatment of large mandibular cysts.

Adolescent↗
PubMed2003

[Evidence of osteocalcin expression in osteoblast cells of mandibular origin growing on biomaterials with RT-PCR and SDS-PAGE/Western blotting].

A new approach to addressing difficult tissue reconstructive or replacement problems in the oral cavity is to engineer new tissue by using selective cell transplantation on polymer scaffolds. The current study characterized the osteoblastic nature of adherent mandibular cells on biomaterials, which could have a potential use as scaffolds for tissue engineering strategies. Cells of mandibular origin from one patient were cultivated on three different biomaterials (PepGen P-15 trade mark, Frios Algipore, and OsteoGraf/LD-700) for 7 and 14 days and osteocalcin expression was demonstrated by RT-PCR and SDS-PAGE/Western blotting. In order to explicitly characterize only the adherent cells on the biomaterials, we first separated the biomaterials with adherent cells from the culture plate before trypsinization. We could demonstrate that cell growth of adherent mandibular osteoblast-like cells was significantly higher on biomaterials with an organic component (PepGen P-15 trade mark ) in comparison to Frios Algipore and OsteoGraf/LD-700, respectively. In conclusion, only the explicit study of adherent cells at the gene and protein levels gives information about the osteoconductivity of biomaterials.

Alginates↗
PubMed2002

Orbital floor reconstruction with an alloplastic resorbable polydioxanone sheet.

The orbital floor is frequently reconstructed after blow-out fractures or midface fractures to avoid a relapse of the repositioned orbital tissue and to prevent enophthalmos. A total of 31 patients underwent reconstruction of internal orbital wall fractures with a resorbable 0.25 mm or 0.5 mm-thick polydioxanone implant (PDS). Skeletal and functional outcome was evaluated retrospectively with regard to fracture size. Fracture size was graded as small, moderate or large by CT scans and operating records. Two of the 25 patients with small or moderate defects showed an enophthalmos of 2-3 mm. Five of the six patients with large defects or two orbital wall fractures had enophthalmos. The scar that formed after implant resorption was to weak to provide adequate support of the globe or to compensate the enlarged orbital volume. Endoscopic follow-up examination of 12 patients showed yielding of the scar in the orbital floor already in moderate defects. Eight patients had diplopia in extreme gaze and two had significant diplopia. Blow-out and midfacial fractures with small to moderate defects in the orbital floor (up to a size of 2.5 cm2) can be reconstructed by polydioxanone sheet to avoid enophthalmos. Polydioxanone implants should only be used in cases without massive orbital fat herniation. The scar formed after implant resorption may influence functional outcome.

Absorbable Implants↗
PubMed2002

Quantitative analysis of factors affecting intraoperative precision and stability of optoelectronic and electromagnetic tracking systems.

This study aims to provide a quantitative analysis of the factors affecting the actual precision and stability of optoelectronic and electromagnetic tracking systems in computer-aided surgery under real clinical/intraoperative conditions. A "phantom-skull" with five precisely determined reference distances between marker spheres is used for all measurements. Three optoelectronic and one electromagnetic tracking systems are included in this study. The experimental design is divided into three parts: (1) evaluation of serial- and multislice-CT (computed tomography) images of the phantom-skull for the precision of distance measurements by means of navigation software without a digitizer, (2) digitizer measurements under realistic intraoperative conditions with the factors OR-lamp (radiating into the field of view of the digitizer) or/and "handling with ferromagnetic surgical instruments" (in the field of view of the digitizer) and (3) "point-measurements" to analyze the influence of changes in the angle of inclination of the stylus axis. Deviations between reference distances and measured values are statistically investigated by means of analysis of variance. Computerized measurements of distances based on serial-CT data were more precise than based on multislice-CT data. All tracking systems included in this study proved to be considerably less precise under realistic OR conditions when compared to the technical specifications in the manuals of the systems. Changes in the angle of inclination of the stylus axis resulted in deviations of up to 3.40 mm (mean deviations for all systems ranging from 0.49 to 1.42 mm, variances ranging from 0.09 to 1.44 mm), indicating a strong need for improvements of stylus design. The electromagnetic tracking system investigated in this study was not significantly affected by small ferromagnetic surgical instruments.

Biophysical Phenomena↗
PubMed2001

Use of the preseptal transconjunctival approach in orbit reconstruction surgery.

PURPOSE: This report evaluated the advantages of the preseptal transconjunctival approach in reconstruction of the orbit. PATIENTS AND METHODS: Ninety-nine preseptal incisions were used in 80 patients for different indications (blowout fracture, complex zygoma fracture, enophthalmos correction, midface hypoplasia, secondary incision). All operative procedures were performed without an additional lateral canthotomy. The infraorbital rim was stabilized with miniplates or microplates. RESULTS: There was no ectropion or entropion in any patients. Complications included 1 laceration of the tarsal plate and 1 temporary entropion after a primary subciliary incision. The overall complication rate was 2%. CONCLUSIONS: The preseptal transconjunctival incision without lateral canthotomy provides good exposure of the orbital floor and the caudal parts of the lateral and medial wall. This approach is preferable to a retroseptal approach in reconstructive orbital surgery because of minimal disturbance of the intraorbital connective tissue framework. The anatomic optimal dissection line also results in a lower complication rate.

Adolescent↗
PubMed2001

Preprosthetic vertical distraction osteogenesis of the mandible using an L-shaped osteotomy and titanium membranes for guided bone regeneration.

PURPOSE: Vertical osteodistraction is a new alternative method for alveolar ridge augmentation of the mandible. The purpose of this article is describe a technique using an L-shaped osteotomy and titanium membranes for guided bone regeneration (GBR) in the distraction gap. PATIENTS AND METHODS: Ten patients with severe atrophy of the edentulous molar region of the mandible underwent vertical callus distraction in 13 sites using intraoral microplate distractors. An L-shaped osteotomy with a short vertical part mesially and a longer horizontal part ending in the retromolar region was made, and the osteotomized segment was fixed to the mandibular ramus at its distal edge by a microplate, which became the center of rotation when distraction began. In this way, more callus generation could be achieved mesially than in the distal molar region. Follow-up computed tomography (CT) scans reconstructed axially to the axis of the mandible revealed semilunar excavations of the generated bone buccally in the distraction gap in the first cases. Clinical inspection on removal of the distractors showed fibrous connective tissue in the gap. Therefore, to prevent this from happening, titanium membranes covering the distraction gap were applied in subsequent cases. RESULTS: Ten patients (13 sites) were treated by vertical callus distraction. In 4 cases, GBR was achieved using titanium membranes. In all cases, the increase in alveolar height was sufficient to make dental implantation possible. In 1 patient, a fracture of the distractor occurred, and dehiscence was observed in 2 cases. These complications did not change the plan of therapy nor did they influence the results. The CT scans showed a homogenous surface on the regenerated mandible in the cases of GBR application. CONCLUSION: Both an L-shaped osteotomy and the application of titanium membranes for GBR in the distraction gap are of great value for mandibular augmentation, producing a physiologically shaped alveolar ridge.

Adult↗
PubMed2001

Midfacial degloving: an alternative approach for traumatic corrections in the midface.

Midfacial degloving was used as an approach in 14 patients to correct post-traumatic deformities in the midface. In eight patients, deformities in the naso-orbito-ethmoid region were corrected by orbitonasal osteotomy, telecanthus correction, orbital grafting and nasal augmentation procedures. Zygomatic osteotomies were performed in five patients with orbitozygomatic deformity. In one patient, a midface fracture (Le Fort II/III) was reconstructed after midfacial degloving. By combination of transoral vestibular, intranasal and preseptal transconjunctival incisions a complete degloving of the midface up to the nasofrontal angle and the zygoma prominence was possible. All osteotomies could be completed after midfacial degloving. Additional coronal incisions were not required. Orbitonasal osteotomies for nasal lengthening as well as fixation of the medial canthal ligament by a miniplate could be performed under direct vision. There were no postoperative complications such as stenosis of the nasal aperture or disturbances of the mimic musculature. Midfacial degloving offers good exposure, specially of the central part of the midface, without leaving an external scar. It is useful for reconstructive procedures in patients after midface trauma.

Adult↗
PubMed2001

Principles of computer-assisted arthroscopy of the temporomandibular joint with optoelectronic tracking technology.

PURPOSE: This preliminary clinical study evaluated the applicability, accuracy, and benefits of computer-assisted arthroscopy of the temporomandibular joint (TMJ) with optoelectronic tracking technology. MATERIALS AND METHODS: A hybrid of reality and virtual reality is built as a composite-reality environment by extracting 3-dimensional anatomical structures through use of computed tomography, magnetic resonance imaging, radiography, and other types of imaging procedures commonly used in clinical praxis. These various independent sources of imaging data of a particular patient can be combined with and complemented by complex graphic simulations. Intraoperatively they are merged with online position data of surgical instruments inside the patient's TMJ. This hybrid model of detailed anatomical structures, guidelines, and real-time instrument positions allows the surgeon to accurately plan the arthroscopic intervention as well as to navigate effectively intraoperatively. RESULTS: In the first 10 cases of computer-assisted TMJ arthroscopy, composite reality environment technology permitted the online visualization of TMJ structures, puncture sites, instrument positions, and virtual pathways in relation to anatomical landmarks with high spatial accuracy (minimum, 0.0 mm; maximum, 2.5 mm; mean, 1.4 mm; SD, 0.6 mm) and high temporal resolution (100 ms). Past, present, and possible future instrument positions can be displayed. The application of computer-assisted arthroscopy caused little immobility for either surgeon or patient. CONCLUSION: Even experienced surgeons profit from improved precision in the handling of the arthroscope; thus this technology was found to be particularly useful in degenerative temporomandibular disorders and for triangulation procedures.

Arthroscopes↗
PubMed2001

Placement of endosteal implants in the zygoma after maxillectomy: a Cadaver study using surgical navigation.

Endosteal implants facilitate obturator prosthesis fixation in tumor patients after maxillectomy. Previous clinical studies have shown, however, that the survival of implants placed into available bone after maxillectomy is generally poor. Nevertheless, implants positioned optimally in residual zygomatic bone provide superior stability from a biomechanical point of view. In a pilot study, the authors assessed the precision of VISIT, a computer-aided surgical navigation system dedicated to the placement of endosteal implants in the maxillofacial area. Five cadaver specimens underwent hemimaxillectomy. The cadaver head was matched to a preoperative high-resolution computed tomograph by using implanted surgical microscrews as fiducial markers. The position of a surgical drill relative to the cadaver head was determined with an optical tracking system. Implants were placed into the zygomatic arch, where maximum bone volume was available. The results were assessed using tests for localization accuracy and postoperative computed tomographic scans of the cadaver specimens. The localization accuracy of landmarks on the bony skull was 0.6 +/- 0.3 mm (average +/- SD), as determined with a 5-df pointer probe; the localization accuracy of the tip of the implant burr was 1.7 +/- 0.4 mm. The accuracy of the implant position compared with the planned position was 1.3 +/- 0.8 mm for the external perforation of the zygoma and 1.7 +/-1.3 mm for the internal perforation. Eight of 10 implants were inserted with maximal contact to surrounding bone, and two implants were located unfavorably. Reliable placement of implants in this region is difficult to achieve. The technique described in this article may be very helpful in the management of patients after maxillary resection with poor support for obturator prostheses.

Cadaver↗
PubMed2000

Evaluation of a chronic indwelling prototype mesh ureteral stent in a porcine model.

OBJECTIVES: Ureteral stents all share one general goal, drainage, and one major drawback, irritative symptoms in the kidney and bladder. In an effort to preserve drainage while minimizing irritation, a lightweight, self-expanding mesh stent was designed. Herein, we compare the in vivo tissue reaction and flow characteristics of the mesh stent to a standard 7F double-pigtail polyurethane stent. METHODS: Eight female Yucatan minipigs had bilateral stents placed: a mesh stent on one side and a standard 7F stent on the opposite side. Imaging and flow measurements were obtained in 4 pigs at 1 week and in another 4 pigs at 6 weeks. Following this procedure, the stents were removed, and the kidneys, ureters, and bladder were harvested en bloc for a blinded histopathologic analysis. RESULTS: The degree of stent-related tissue reactivity was low for both stents and appeared similar for the ureter and bladder. Overall, the mesh stent resulted in a decrease in inflammation along the urinary tract at 1 week, but this result was statistically insignificant (P = 0.55). Flow rate through the mesh stent tended to be greater than for the polyurethane stent both at 1 week and at 6 weeks. CONCLUSIONS: Overall, the mesh stent appeared to be well tolerated and provided for excellent flow.

Animals↗