Evaluation of changes in clinical crown length of lower anterior teeth after treatment with Frankel-2's appliance.

PURPOSE: The aim of this study was to test the null hypothesis that there is no change in the lower anterior teeth's crown size when measured just after the treatment with Frankel-2's orthopedic appliance and in a long-term posttreatment follow-up. MATERIALS AND METHODS: The sample was composed of 34 plaster models belonging to 9 male and 8 female individuals, treated at the College of Health, Methodist University of São Paulo, São Bernardo do Campo, São Paulo, Brazil, with mean age of 12 years and 6 months (standard deviation [SD] =7 months) at T1 (end of the treatment with Frankel-2's function regulator), and 19 years and 8 months (SD = 7 months) at T2 (7.11 years after the end of the treatment). RESULTS: The distance from the incisal edge to the most concave portion of the gingival margin of the lower incisors and canines was measured using a digital caliper. Data analysis was carried out by means of Student's t-test and paired-t test. Among the lower anterior teeth, the teeth 31, 33, 42 and 43 showed a statistically significant increase in their crown length, whereas the teeth 32 and 41 showed no changes. CONCLUSION: It can be concluded that there is a tendency to increase the clinical crown of lower anterior teeth throughout the years after the mandibular advancement treatment by using functional devices, rejecting the null hypotheisis.

Orthodontic cements induce genotoxicity and cytotoxicity in mammalian cells in vitro.

BACKGROUND: This study assessed the genotoxic and cytotoxic potential of three different glass ionomer cements used in Orthodontics (Vidrion C, OptiBand, and Band-Lok). MATERIALS AND METHODS: The tested cements were exposed in vitro to mouse fibroblast cells for 1 h at 37°C. The genotoxicity and cytotoxicity were evaluated by means of the single cell gel (Comet Assay) and the trypan blue exclusion test, respectively. All data were assessed by the Kruskal-Wallis non-parametric test, followed by Dunn's test. P < 0.05 was considered for statistical significance. RESULTS: Significant statistically differences (P < 0.05) in cytotoxicity were observed for both Vidrion C powder and liquid at the tested concentrations, with exception to the group presenting the lowest powder concentration. OptiBand similarly presented induced cellular death at the highest tested concentration for paste A (P < 0.05). Band-Lok paste B was also able to induce cytotoxicity at the highest tested concentration. Regarding the comet assay, Band-Lok paste B and OptiBand paste A resulted in increased DNA injury (P < 0.05). CONCLUSION: The obtained results support the thought that some glass ionomer cement components present both genotoxic and cytotoxic effects when in high concentrations. Since DNA damage and cellular death are important events during oncogenesis, this study represents relevant contribution to estimate the real risks induced by these materials upon cellular systems.