No abstract

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.

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.

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.