RESUMO
Electrical discharge using a capacitance of 450 µF at 7.0 and 8.0 kJ input energies was applied to mechanical alloyed Ti5Si3 powder without applying any external pressure. A solid bulk of nanostructured Ti5Si3 with no compositional deviation was obtained in times as short as 159 µsec by the discharge. During an electrical discharge, the heat generated is the required parameter possibly to melt the Ti5Si3 particles and the pinch force can pressurize the melted powder without allowing the formation of pores. Followed rapid cooling preserved the nanostructure of consolidated Ti5Si3 compact. Three stepped processes during an electrical discharge for the formation of nanostructured Ti5Si3 compact are proposed: (a) a physical breakdown of the surface oxide of Ti5Si3 powder particles, (b) melting and condensation of Ti5Si3 powder by the heat and pinch pressure, respectively, and (c) rapid cooling for the preservation of nanostructure. Complete conversion yielding a single phase Ti5Si3 is primarily dominated by the solid-liquid mechanism.
RESUMO
Complete resection is usually impossible for fibrous dysplasia (FD) involving the cranial base. Incomplete resection could be followed by regrowth of FD, but there is no method for indicating disease progress. Serum alkaline phosphatase (ALP) is significantly high in patients with FD. The authors investigate the relationship between ALP, progress of FD, and age at surgery. 18 patients with craniofacial FD were separated into 3 groups: Group A, complete resection; Group B, incomplete resection followed by regrowth of FD; and Group C, incomplete resection but no regrowth of FD. Medical records and CT scans were reviewed retrospectively. ALP levels were obtained preoperatively, postoperatively and every year during follow-up. The relation between ALP and regrowth and that between age at surgery and regrowth were investigated. There was no recurrence in Group A (n=4). Regrowth in Group B (n=7) was preceded by an abrupt increase in ALP. In Group C (n=7), no regrowth was observed and ALP was maintained within the normal range. 6 patients (85%) in Group B and 2 (28%) in Group C were under 17 years old. The results revealed that the level of postoperative serum ALP could be a reliable marker for predicting the progress of craniofacial FD.