[Exploration of tumor suppressors p16INK4a and p14ARF in oral leukoplakias]. / Untersuchung der Tumorsuppressoren p16INK4a und p14ARF in Mundschleimhautleukoplakien.

The inactivation of p16 and p14ARF is considered to be an important step in the carcinogenesis of oropharygeal carcinomas. This consideration is supported by the observation of multiple allelic losses in the coding loci of chromosome 9p21 in squamous cell carcinomas and in dysplastic premalignant lesions. The present study hypothesized that comparable alterations already occur in leukoplakia, which are seen as potential predecessors of oral squamous cell carcinomas and that it is possible to differ leukoplakia with from leukoplakia without further malignant transformation. Furthermore we evaluated, whether such leukoplakia show sequence alterations in the genes p16 and p14ARF, which are capable to cause a limitation in gene function. The results show that the LOH pattern in genes p16 and p14ARF occur as well in leuplakia with malignant transformation as in leukoplakia, that do not show clinical alterations. The rate of allelic loss did not differ significantly. Overall, the incidence of allelic loss was lower in leuplakia compared to succeeding squamous-cell carcinomas (p<0,05). The results further illustrated an increase in LOH patterns in dyplastic leukoplakia, without reaching statistical significance. Significant increases in allelic losses were found in heavy smokers, (p < 0,05). PCR analysis of the exons 1-alpha, exon 1-beta and exon 2 in leukoplakia, containing LOH patterns did not show genetic alterations. Thus we concluded, that gene deletion and gene mutation have a minor role in the inactivation process of p16 and p14ARF in oral leukoplakia. Representing an early process in carcinogenesis, gene deletion and mutation occur in leukoplakia with and without malignant transformation. Therefore, taken as a singular parameter they represent an uncertain criteria to assess the potential of malignant transformation. However they could provide information in combination with other genetic factors like chromosomal methylation patterns and histology.

Ultrasound aided pin fixation of biodegradable osteosynthetic materials in cranioplasty for infants with craniosynostosis.

AIM: Biodegradable osteosynthesis materials are often used for fixation of bone fragments when repairing craniosynostoses. When compared with titanium plates they have the disadvantage of difficult handling and time-consuming thread cutting. A new method of using resorbable pins inserted with the aid of ultrasound (bone welding) and not requiring thread cutting was applied in patients for the first time. METHOD: In eight patients with craniosynostoses, the biodegradable material Resorb-X was fixed with resorbable pins inserted with the aid of ultrasound. The patients were followed up for 12 months. RESULTS: Pin fixation was stable in all cases. The time required for applying the osteosynthesis materials was reduced by about 50% since handling of the material was easier and no thread cutting was required. CONCLUSIONS: Due to fixation in cortical as well as cancellous bone ultrasound aided fixation using resorbable osteosynthesis materials is more stable than screw fixation. The time required for application is considerably shortened as no thread cutting is required.