Vertical components of overbite change: a mathematical model.

The purpose of this study was to better understand the multidimensional nature of overbite changes that occur during adolescence. The study used longitudinal cephalograms of 181 untreated children (102 males, 79 females) taken at ages 10 and 15. Four major components that directly affect overbite were measured: (1) maxillary vertical displacement, (2) mandibular vertical displacement, (3) upper incisor vertical change within the bone, (4) lower incisor vertical change within the bone. Cranial base, maxillary, and mandibular superimpositions were performed for each subject to assess the vertical changes that occurred in these 4 components and to assess overbite. A multiple regression analysis was used to develop a mathematical model describing the relationships of these components to changes in overbite. The model was validated with an independent subsample and a comparison of subjects whose overbites decreased and those whose overbites increased. The results showed that overbite changed minimally (0.2 mm) over the 5-year period; variation ranged from a 2.4 mm decrease to a 5.6 mm increase. The regression model indicated that the mandibular skeletal changes were twice as important as the mandibular dental changes and about 2.5 times as important as the maxillary changes in effecting overbite change. Within the mandibular skeletal component, vertical growth was more important than mandibular rotation in determining overbite change. The model demonstrated that a multivariate approach is necessary to understand overbite changes. More effective orthodontic treatment might be achieved by focusing on the primary components effecting overbite change, especially those with the greatest potential for therapeutic modification.

Anti-proliferative effects of deflazacort on Nb2 cells as quantitated by formazan production.

Prolactin and other lactogenic hormones are mitogenic for the rat T-cell lymphoma line, Nb2. Glucocorticoids have antiproliferative effects on these cells. A limiting feature of experiments utilizing the Nb2 line is their labor-intensive nature. We therefore adapted the commonly used MTT dye proliferation assay for the Nb2 cell line. While rPRL, hPRL, oPRL, hGH, bPL, and to a lesser extent bPRL stimulated the Nb2 cells, hormones without lactogenic activity, rGH and oGH did not. Human serum and rat sera from animals bearing a PRL-secreting tumor stimulated the Nb2 cells in parallel to standards. Glucocorticoids had anti-proliferative effects on Nb2 cells in the presence of half-maximal or maximal PRL doses, as measured by the MTT proliferation assay. It has been claimed that an oxazoline steroid, deflazacort, has anti-inflammatory effects in clinical studies with fewer of the deleterious side-effects common to glucocorticoids. We therefore compared the in vitro anti-proliferative effects of deflazacort with other glucocorticoids. Deflazacort's negative effect on Nb2 cell proliferation was similar to that of cortisol and prednisolone and less than that of dexamethasone. We conclude that the MTT proliferation assay can be used to study both mitogenic and anti-proliferative substances in Nb2 cells. In addition we found that deflazacort acts similarly in vitro to other glucocorticoids.