Manipulating the mandibular distraction site at different stages of consolidation.

PURPOSE: The purpose of this study was to define optimal timing and conditions for correcting an open bite side effect by manipulating the distraction site with orthodontic springs after mandibular distraction. MATERIALS AND METHODS: At 0, 1, 2, 3, and 8 weeks postdistraction, interarch springs were attached for 2 weeks to close distraction-produced open bites in 45 rabbits. Distractors were removed in half of the animals receiving spring treatment. Segment position was recorded by weekly direct measurements and radiographs. Tissue samples were collected at the end of spring application for microcomputerized tomography analysis and measurements of lateral symmetry. RESULTS: Orthodontic springs closed the open bite with or without distractors in place immediately after distraction and partially corrected the bite at later stages of bone consolidation. Distractor removal produced more rapid bite closure but also introduced lateral buckling of the distraction site during early consolidation. The lateral buckling was not observed if springs were applied after 2 weeks of consolidation. The amount of bite correction with orthodontic springs correlated with mineralization of the distraction site. CONCLUSION: During the consolidation period, a distraction site can be callus manipulated with orthodontic springs to correct an open bite. The amount of correction depended on when springs were placed and whether distractors were removed at the time of spring application.     

Evaluation of an immunoextraction procedure for the estimation of free thyroxine concentration

We have examined the performance of a commercial free-thyroxine assay in which a radiolabeled T4 derivative permits the competitive quantitation of extracted T4 in the presence of serum proteins. After the total T4 pool had been radiolabeled with either I-125 T4 or I-131 T4, the solid-phase antibody was found to be associated with 4-8% of the total T4 present in the assay tube. Of this, 15-60% was displaceable (antibody-bound). The assay estimated free T4 to be 0.6-1.8 ng/dl in euthyroid patients, and distinguished them from hyperthyroid (sensitivity 91%) and hypothyroid patients (sensitivity 91%) without apparent TBG dependence. In patients with severe nonthyroidal illnesses, the assay correctly quantitated a reduced extracted mass in some. In other patients, however, the assay results were inappropriately lower than the actual extracted mass, in agreement with the FTI but not with the measurements of free T4 by dialysis. This assay appears to produce clinically appropriate results in most patients. In some nonthyroidally ill patients however, the indicated free T4 is spuriously low.