In Vitro Study of the Effect of Tooth Displacement and Vibration on Frictional Force and Binding-and-Releasing Phenomenon

Abstract

Objective: The purpose of this in vitro study was to evaluate the effect of tooth displacement and vibration on frictional force and binding-and-releasing phenomenon (BRP) in conventional bracket (CB) and passive-type self-ligating bracket (PSLB) when used with leveling/alignment wire, respectively.

Materials and Methods: Two types of bracket [CB (Victory, 3M-Unitek, Monrovia, CA, USA) and PSLB (Damon-Q, Ormco, Orange, CA, USA)] were tested under two conditions: tooth displacement [2 mm lingual displacement of the maxillary right lateral incisor (LD)

2 mm gingival displacement of the maxillary right canine (GD)

no displacement (control)] and vibration [presence and absence (30 Hz and 0.25 N)] (N = 10/group). A stereolithographically-made typodont system was used. After artificial saliva was applied to the bracket slot, static/kinetic frictional forces (SFF/KFF) and frequency/amplitude of BRP were measured during drawing of 0.018 inch Copper-NiTi archwire at a speed of 0.5 mm/min for 5 minutes at 36.5 °C. Two-way analysis of variance and post hoc Bonferroni test were performed.

Results: (1) SFF and KFF significantly increased in order of control, LD, and GD groups among tooth displacement types in both CB and PSLB (all p < 0.001). SFF and KFF under vibration condition significantly decreased compared to non-vibration condition in PSLB (all p < 0.001), but they did not show significant differences in CB. (2) The effect of vibration to increase BRP frequency was generally reduced according to tooth displacement in both CB (p < 0.01) and PSLB (p < 0.001). (3) The effect of vibration to decrease BRP amplitude was generally reduced according to tooth displacement in CB (p < 0.001). However, in PSLB, BRP amplitude significantly increased in order of control, LD, and GD groups among tooth displacement types (p < 0.001) and significantly decreased under vibration condition than that under non-vibration condition (p < 0.001).

Conclusions: The effect of tooth displacement to increase the frictional force showed similar tendency in both CB and PSLB. However, the effect of vibration to decrease the frictional force and BRP amplitude was more prominent in PSLB than that in CB. Therefore, these results might suggest a possibility that the change in BRP by vibration indirectly induced decreases in frictional force in PSLB.