Mel-18 gene is one of the core members of the PcG (polycomb group) family,which plays an important role in embryogenesis,cell growth and proliferation and self-renewal of stem cells.Mel-18 gene expressing abnormally has been related to human tumorigenesis,development process.Mel-18 serves as a tumor suppressor gene and inhibits tumor growth through transcriptional repression of Bmi-1 and c-myc.Mel-18 expression is decreased at transcriptional and translational levels in most human cancers including breast cancer,prostate cancer,and gastric cancer and other tumors.Mel-18 is expected to become a prognostic marker for human cancers.

Objective This study aims to investigate the relationship between the dental and basal arch forms of patients with skeletal class Ⅱ malocclusion using three-dimensional virtual models and to generate the best-fit curve for these arch forms. Methods The mandibular dental casts of 35 skeletal class Ⅱ patients were taken prior to treatment and were laser scanned. The facial axis (FA) points, which were used to represent the dental arch, and the WALA points, which were used to represent the basal bone, were identified for each tooth from the right first molar to the left first molar. The Pearson corre-lation coefficients between the intercanine and intermolar widths at the FA and WALA points were determined. Finally, the best-fit curves were generated using the fourth-degree polynomial equation to represent the arch forms. Results A strong correlation was found between the FA and WALA intermolar widths (r=0.873). However, a moderate correlation was observed between the FA and WALA intercanine widths (r=0.534). The difference between the intermolar widths at the FA and WALA points was significant (P<0.01). No statistically significant difference was found between the intercanine widths (P=0.481). The radii of curvature of the FA and WALA curves in the anterior teeth area were 15.194 and 20.250, respectively. The re-gression coefficients of the FA and WALA curves were calculated as R2=0.912 and 0.947, respectively. Conclusion For skeletal class Ⅱ malocclusion patients, the FA and WALA dental intermolar widths showed strong correlation, whereas the FA and WALA intercanine widths exhibited moderate correlation. The FA points were located more labially in the anterior teeth area but more lingually in the posterior teeth area. No statistically significant difference was found between the intercanine FA and WALA widths. The difference between the intermolar widths at the FA and WALA points was significant. The radii of curvature of the FA curve was larger than that of the WALA curve in the anterior teeth area.