Effect of tooth displacement and vibration on frictional force and stick-slip phenomenon in conventional brackets: a preliminary in vitro mechanical analysis.

OBJECTIVE To evaluate the effects of tooth displacement and vibration on frictional force and stick-slip phenomenon (SSP) when conventional brackets were used with a levelling/alignment wire. MATERIALS AND METHODS The samples consisted of six groups (n = 10 per group) with combinations of tooth displacement (2mm lingual displacement [LD], 2mm gingival displacement [GD], and no displacement [control]) and vibration conditions (absence and presence at 30 Hz and 0.25 N). A stereolithographically made typodont system was used with conventional brackets and elastomeric ligatures. After application of artificial saliva, static/kinetic frictional forces (SFF/KFF) and frequency/amplitude of SSP were measured while drawing a 0.018-inch copper nickel-titanium (Cu-NiTi) archwire at a speed of 0.5mm/min for 5 minutes at 36.5 degree celsius. Two-way analysis of variance and independent t-test were performed. RESULTS Tooth displacement increased SFF and KFF (control < LD < GD, all P < 0.001) and reduced SSP frequency (control > [LD, GD], P < 0.01). Vibration reduced SFF, KFF, and SSP amplitude in the control group (P < 0.05, P < 0.05, and P < 0.001, respectively), but not in the LD and GD groups. SSP frequency was increased by vibration in the control, LD, and GD groups (all P < 0.001), and it was lower in the LD and GD groups than in the control group (P < 0.01). CONCLUSIONS When conventional brackets and a 0.018-inch Cu-NiTi archwire were used in the tooth displacement conditions (LD and GD), vibration did not significantly reduce SFF, KFF, or SSP amplitude.