Rate and anchorage loss during en-masse retraction between friction and frictionless mechanics: A randomized clinical...

To compare rate and anchorage loss during en-masse retraction of anterior maxillary teeth between friction mechanics (FM) and frictionless mechanics (FLM).

Thirty-eight patients requiring en-masse retraction of protruded anterior maxillary teeth were randomly allocated into FM and FLM groups.

En-masse retraction with sliding mechanics (FM) using an elastomeric chain was compared with continuous mushroom loop archwire mechanics (FLM). Study models and lateral cephalograms were taken before (T1) and immediately after retraction (T2). The primary outcome was the rate of en-masse retraction. Anchorage loss was the secondary outcome. Intergroup comparison was performed using an independent t test (P < .05).

Baseline characteristics were similar between groups. Thirty-six patients completed the trial. Two patients were lost to follow-up in the FLM group. The rate of en-masse retraction did not differ significantly (P = .625) between FM (0.7 mm/mo) and FLM (0.8 mm/mo) groups. The intragroup comparison showed significant anchorage loss in FM (2.28 mm) and FLM (1.13 mm) groups; however, the intergroup comparison showed no statistically significant difference (P = .093). Maxillary first molar showed a statistically significant change in angulation between the two mechanic groups (P < .001). Vertical movement of the maxillary incisor and first molar showed no significant difference between FM and FLM groups (P = .143, P = .546, respectively).

The rate of en-masse retraction and anchorage loss was comparable between the FM and FLM groups. Significant anchorage loss was seen with both mechanics. The result suggests that both the mechanic group require external reinforcement to prevent anchorage loss.