Friction properties according to vertical and horizontal tooth displacement and bracket type during initial leveling and alignment.

OBJECTIVE: To compare frictional properties according to the amounts of vertical displacement (VD) and horizontal displacement (HD) of teeth and bracket types during the initial leveling/alignment stage. METHODS: Combinations of self-ligating brackets (SLBs; two active type: In-Ovation-R and In-Ovation-C; four passive type: Damon-3Mx, Damon-Q, SmartClip-SL3, and Clarity-SL) and 0.014-inch nickel-titanium archwires (austenitic type, A-NiTi, and copper type, Cu-NiTi) were tested in a stereolithographically made typodont system that could simulate malocclusion status and periodontal ligament space. The upper canines (UCs) were displaced in the gingival direction and the upper lateral incisors (ULIs) in the lingual direction from their ideal positions by up to 3 mm, with 1-mm intervals, respectively. Two conventional brackets were used as controls. Static and kinetic frictional forces were measured. One-way analysis of variance test with post hoc test was performed for statistical analysis. RESULTS: In the gingival displacement of UCs, Clarity-SL produced significantly lower frictional force (P < .001), while Damon-3Mx, In-Ovation-R, and SmartClip-SL3 produced higher frictional force among SLBs. In the lingual displacement of ULIs, Damon-Q and Damon-3Mx produced significantly lower frictional force (P < .01), while Clarity-SL produced the highest frictional force among SLBs (P < .001). Clarity-SL combined with A-NiTi and C-NiTi, Damon-3Mx combined with A-NiTi, and In-Ovation-C combined with Cu-NiTi showed differences in frictional properties between VD and HD. CONCLUSIONS: Since the frictional properties of SLBs would be different between VD and HD of teeth, it is necessary to develop SLBs with low friction in both VD and HD of teeth.

En masse retraction and two-step retraction of maxillary anterior teeth in adult Class I women. A comparison of anchorage loss.

OBJECTIVE: To compare the amount of anchorage loss of the maxillary posterior teeth and amount of retraction of the maxillary anterior teeth between en masse retraction and two-step retraction of the anterior teeth. MATERIALS AND METHODS: The sample consisted of 30 female adult patients with Class I malocclusion and lip protrusion who needed maximum posterior anchorage. The sample was subdivided into group 1 (n = 15, mean age = 21.4 years, en masse retraction) and group 2 (n = 15, mean age = 24.6 years, two-step retraction). Lateral cephalograms were taken before (T1) and after treatment (T2). Nine skeletal and 10 anchorage variables were measured, and independent t-test was used for statistical analysis. RESULTS: Although the amount of horizontal retraction of the maxillary anterior teeth was not different between the two groups, there was mild labial movement of the root apices of the upper incisors in group 2 at T2. There were no significant differences in the degree of anchorage loss of the maxillary posterior teeth between the two groups. Bodily and mesial movements of the upper molars occurred in both groups. Approximately 4 mm of the retraction of the upper incisal edges resulted from 1 mm of anchorage loss in the upper molars in both groups. CONCLUSION: No significant differences existed in the degree of anchorage loss of the upper posterior teeth and the amount of retraction of the upper anterior teeth associated with en masse retraction and two-step retraction of the anterior teeth.