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Biomedical subjects

J Kreidler

Publications and source records attributed to J Kreidler.

At least 19 recordsLinked to original sources
PubMed2002

[Physiological loading of the mandibular osteosynthesis: development of an improved mandibular load simulator].

Loading conditions physiologically approximating those acting on the normal masticatory system were incorporated into a new mandibular load simulator. Separate tension wires attached to each ramus of the mandible simulated the resultant force vectors of the masticatory musculature. The muscle insertion points were chosen in accordance with the anatomical situation, and the maximum in vivo forces acting on the joint. In a first application, the stability of a 2.4 mm LC-WDCP was compared with that of a 2.7 mm EDCP in plastic mandible models. It was found that under largely physiological loading, the 2.4 mm LC-EDCP exerted a stabilizing effect similar to that of a 2.7 mm EDCP. Although of smaller dimensions, the 2.4 mm LC-EDCP appears to enable an osteosynthesis of similar stability in the treatment of fractures of the mandibular angle.

Biomechanical Phenomena↗
PubMed2001

A composite polymer/tricalcium phosphate membrane for guided bone regeneration in maxillofacial surgery.

The aim of the study was the development of a resorbable membrane for guided bone regeneration (GBR) with improved biocompatibility, which should be stiff enough to avoid membrane collapse during bone healing. Combining a bioactive ceramic with a resorbable polymer may improve the biocompatibility and osteoconductivity of resorbable devices. The present article describes the preparation, the mechanical properties, and the in vitro degradation characteristic of a composite membrane made of poly(L, DL-lactide) and alpha-tricalcium phosphate in comparison to a membrane made of pure poly(L, DL-lactide). The tensile strength and the elastic modulus as well as the molecular weight of the membranes were measured after in vitro degradation in buffer at 37 degrees C up to 28 weeks. The initial tensile strength of the composite and the polymer membrane was 37.3 +/- 2.4 MPa and 27.7 +/- 2.3 MPa and the elastic modulus 3106 +/- 108 MPa and 3101 +/- 104 MPa, respectively. The mechanical properties remained constant up to 8 weeks and then decreased slowly until week 28. The molecular weight of both membranes decreased steadily from 170,000 D to 30,000 D. It was concluded that the mechanical requirements for a membrane for GBR were fulfilled by the composite membrane.

Absorbable Implants↗
PubMed1999

Intra-arterial preoperative cytostatic treatment versus preoperative irradiation: A prospective, randomized study of lingual and sublingual carcinomas.

BACKGROUND: For several decades, both preoperative intra-arterial chemotherapy and preoperative irradiation have been accepted treatments for patients with tumors of the head and neck. Unfortunately, arguments have often been put forward in favor of one or other of the two methods, but without the performance of an objective, randomized investigation. To resolve this situation, the authors have carried out a multicenter, randomized prospective study of selected patients with a view to deciding which method affords better results in complex tumor therapy from the aspects of survival and postoperative quality of life. METHODS: One hundred thirty-one patients with operable sublingual or lingual squamous cell carcinoma in stages T2NXM0 to T4MXM0 were randomized into 2 groups: 1 group participated in preoperative chemotherapy with cisplatin and epirubicin (total doses: 200 mg cisplatin, 120 mg epirubicin) via the external carotid artery, whereas the other group received preoperative radiation therapy (46 grays). Following subsequent radical surgery, the patients received regular follow-up for 5 years. RESULTS: By the end of the 5 years, 95 of the 131 patients had conformed to the protocol. Of those 95, 47 had received preoperative chemotherapy and 48 preoperative irradiation. After 5 years, 18 of the 47 patients who received chemotherapy and 15 of the 48 patients who received irradiation were still alive and tumor free. A few more patients had died of recurrence or regional metastasis in the chemotherapy group (23 patients) than in the irradiation group (20 patients). Occurrence of a second carcinoma was 3 times as frequent in the irradiation group (9 patients) as in the chemotherapy group (3 patients). Overall, the survival rates were by-and-large the same for the two groups. Regarding postoperative quality of life, the chemotherapy group presented a more favorable picture. CONCLUSIONS: The long term survival results subsequent to preoperative intra-arterial chemotherapy or preoperative radiotherapy were practically the same. Regarding postoperative quality of life, patients who underwent intra-arterial chemotherapy appeared to be in a slightly more favorable situation. The authors consider it important to stress these findings, as they are not aware of a similar randomized study of patients with tumors of the oral cavity.

Adult↗
PubMed1998

The significance of DNA flow cytometry in predicting survival and delayed clinical manifestation of occult lymph node metastasis to the untreated neck in patients with oral squamous cell carcinoma.

A total number of 116 clinically neck-negative patients with squamous cell carcinoma of the oral cavity who underwent radical primary tumour surgery without simultaneous neck treatment were entered into this prospective study. The 5 year overall survival rate was 87% for patients with flow cytometrically diploid tumours and 58% for the aneuploid group (P < 0.05). By multivariate survival analysis, tumour stage (P < 0.05) and DNA ploidy (P < 0.05) were significantly associated with the outcome. The cumulative 3 year rate of delayed clinical manifestation of lymph node metastasis to the previously untreated neck was 12.6% for patients with flow cytometrically diploid tumours and 41.3% for the aneuploid group (P < 0.01). By multivariate analysis, the DNA ploidy status of the primary tumour was the only factor among tumour stage, localization and degree of histological differentiation predictive of occult metastasis development (P < 0.05). Also, patients with T1 tumours who frequently are not considered to benefit from elective neck dissection were at high risk of subclinical lymph node involvement if the primary tumours were aneuploid (47%), whereas only 10% of the diploid T1 sample showed occult neck disease. Particularly in patients with less extensive oral carcinomas, DNA aneuploidy is therefore an important decisive factor in elective neck dissection.

Carcinoma, Squamous Cell↗
PubMed1997

Morphology and blood supply of the iliac crest applied to jaw reconstruction.

The aim of this study was to improve vessel and nerve security and the harvesting procedure of the iliac crest in the microvascular reconstruction of the upper and lower jaw by iliac crest flap in cases of tumour invasion or trauma. The critical points for the surgeon in harvesting the iliac crest are the course of the deep circumflex iliac artery and lateral cutaneous nerve of the thigh in relation to the iliac crest and the position of their subsequent ramifications. Bilateral anatomical preparations of the iliac bone (total 90 dissections) were examined in 45 formalin preserved cadavers (21 male, 24 female) with the course of the vessel and nerve supply being mapped. Topographic variations of muscles, bones, vessels and nerves were documented by measurement by photographic documentation and diagrams. In 78% (70 cases) a standard-type arrangement with a single main vessel coming from the external iliac artery above the inguinal ligament and crossing the upper part of the iliac crest with second ramifications was observed. In 12% (11 cases) the main vessel was observed to be 2-3 cm below the iliac crest, in 7% (6 cases) a second main branch of the deep circumflex iliac artery was found to run parallel to the iliac crest. In other cases the following variations were observed: one main vessel without ramification, separate branching of the main vessel and ramifications or common trunks of the deep and superficial circumflex iliac arteries. Because of these results it might be possible to perform window resection of the iliac crest in some cases rather than bloc resection: this may have postoperative advantages for the patient.

Bone Transplantation↗
PubMed1991

Monitoring of intra-arterial treatment with epirubicin and cisplatin in oral carcinoma by DNA flow cytometry.

Twenty-two patients with squamous cell carcinoma of the oral cavity were treated intra-arterially with epirubicin and cisplatin. Biopsies were taken before, during, and after treatment and analysed by DNA flow cytometry. Clinical response to therapy was better in the diploid group as well as in previously aneuploid tumors which showed complete disappearance of the abnormal clone in the course of treatment. Poor reduction of tumor volume corresponded with persistence of aneuploid cells.

Carcinoma, Squamous Cell↗
PubMed1991

[The DNA ploidy in squamous cell carcinomas of the mouth floor determined by flow cytometry].

The cellular DNA content of 90 primary squamous cell carcinomas of the floor of mouth was determined by flow cytometry. Aneuploid cell lines were detected in 86% of the cases. The proportion of diploid carcinomas decreased with size (T1: 63%, T2: 11%, T3: 7%) and histologic grade (G1: 17%, G2: 16%, G3: 9%). Only 15% of the diploid, but 61% of the aneuploid tumors showed evidence of lymph node involvement. A 96% sensitivity of the test and a negative predictive value of 85% emphasize the prognostic importance of DNA ploidy in the primary tumor to evaluate the risk of subclinical dissemination.

Carcinoma, Squamous Cell↗
PubMed1990

Flow cytometric DNA ploidy analysis of squamous cell carcinoma of the oral cavity. Comparison with clinical staging and histologic grading.

The clonal DNA content of tumor biopsy specimens of 110 patients with primary and untreated squamous cell carcinoma of the oral cavity was determined by flow cytometric study. The ploidy status was compared with tumor size and histologic grading. Thirty tumors (27.3%) were diploid; in 80 cases (72.7%) cell lines with abnormal DNA content were detected. The portion of aneuploid tumors increased with decreasing degree of histologic differentiation (P less than 0.001) from G1 (38.1%) to G2 (76.6%) and G3 (92.0%). Only one of 13 T1 carcinomas (7.6%) showed abnormal clonal DNA content, but 76.9% of T2 and 90.6% T3 tumors (P less than 0.001) did. The emergence of aneuploid clones obviously represents a marker of malignancy progression in oral carcinoma.

Aneuploidy↗
PubMed1990

The orthopan tomoscintigram--a new application of emission computed tomography for facial bone scanning.

The exact regional correlation of findings of facial bone scans, planar or SPECT, to dental orthopan X-ray films (OPT) is difficult because of the very different projection techniques. To improve correlative imaging in this regard a projection algorithm was developed that uses SPECT data of the skull for reconstructing an orthopan tomoscintigraphic projection. Fourteen conventional SPECT slices of the upper and lower jaws were obtained during bone scanning. All mandibular slices were superimposed resulting in a horseshoe shaped structure, while was marked by an ROI which was divided into segments. All 14 SPECT slices were then masked by this segmental ROI, thereby marking the teeth-carrying bone in all slices. The information from this horseshoe like ROI is then transformed into lines. Line by line arrangement results in an orthopan projection, the orthopan tomoscintigram. This new display allows 1:1 true scale superimposition with the X-ray OPT and markedly facilitates correlative imaging.

Facial Bones↗
PubMed1990

Prognostic implications of DNA ploidy in squamous cell carcinomas of the tongue assessed by flow cytometry.

A total of 47 primary squamous cell carcinomas of the tongue were analysed by DNA flow cytometry. With respect to their clonal DNA content two distinct tumor groups could be distinguished. In 14 cases the tumors (29.8%) were dipoid, whereas in 33 cases (70.2%) additional cell lines characterized by abnormal DNA content could be detected. A significant increase of aneuploid cases with tumor size as well as with decreasing histological differentiation could be detected. Aneuploid cell lines are lacking in T1 as well as in most G1 carcinomas but predominate in T3 and G3. Furthermore, cervical lymph node involvement was recognized in the majority of aneuploid primary carcinomas (81.8%) but was largely lacking in diploid tumors (21.4%). Hence, the presence of aneuploid cell lines is clearly connected with clinical and histopathological parameters, each of which have turned out to worsen the prognosis in tongue carcinomas.

Carcinoma, Squamous Cell↗
PubMed1989

Giant ossifying fibroma: a clinicopathologic study of 8 tumors.

Clinical, radiographic and microscopic features of 8 ossifying fibromas diagnosed in 7 patients and measuring more than 8 cm in greatest diameter, were reviewed. The tumors occurred in both juvenile and middle aged patients and all lesions in women involved the maxilla. The abundance of fibrous connective tissue and resorption of mineralized deposits are indicative of altered cellular differentiation and proliferative activities in large ossifying fibromas. Focal areas of aneurysmal bone cyst formation were identified in the majority of lesions.

Adolescent↗
PubMed1989

[Therapeutic concept of the University of Ulm for the treatment of neuralgiform facial pain].

The therapy of chronic facial pain poses an interdisciplinary problem. Since 1984 the therapeutical plan of Ulm University was developed in such a way that the intensity of pain and the location as well as former treatments are accommodated. The therapeutical steps don't interfere among one another. In the first four years 204 patients were treated with this scheme. A freedom or at least a reduction of pain was achieved in 187 patients.

Autonomic Nerve Block↗