Torque changes of anchorage units in pre-adolescent patients treated with a digitally designed tooth-borne expander anchored to deciduous vs. permanent molars

Aim To compare the effects on permanent or deciduous anchorage dental units in patients treated with a digitally designed palatal expander.Study Design Retrospective controlled study on consecutively treated patients.Methods Inclusion criteria were the following: presence of maxillary transverse deficiency, no previous orthodontic treatment, no extractions, absence of agenesis, congenital pathologies and cranio-maxillofacial malformations. Twenty patients (11 males, 9 females, 11 +/- 1.8 years) received a digitally designed and metal printed palatal expander anchored on first permanent molars and 1 activation per day for 30 days (Group 1). Twenty-one patients (12 males, 9 females, 8.6 +/- 1.4 years) received a digitally designed and metal printed palatal expander anchored on second deciduous molars and 2 activations per day for 14 days (Group 2). Digital intraoral scans were taken before expansion and after device removal, and torque and the palatal transverse diameter were digitally measured. The FDI notation was used to indicate each tooth.Results Significant intragroup differences over time were found in Group 1 considering the torque of teeth 1.6, 1.4, 1.3, 2.1, 2.4, 2.5, 2.6. Significant differences between groups were found regarding the longitudinal change in torque of teeth 1.5, 2.4 and 2.5. Significant intragroup differences over time were found in both groups considering all transverse diameter parameters. No significant differences were found between groups in the transverse diameter modifications over time.Statistics Intragroup differences over time were tested by the Paired t-Test or Wilcoxon's signed rank test. To investigate the association of differences over time with groups, the Student's t-Test and Mann-Whitney U test were performed.Conclusions Less dental torque augmentation was produced in Group 2.