Does anchorage loss differ with 0.018-inch and 0.022-inch slot bracket systems?

Objectives: To compare maxillary first molar anchorage loss between 0.018-inch and 0.022-inch slot fixed appliance systems.

Materials and Methods: Patients requiring bilateral maxillary premolar extractions (n=74) within a randomized clinical trial comparing the effectiveness of 0.018-inch and 0.022-inch slot MBT bracket systems (3M-Unitek, Monrovia, California) were included. Three-dimensional pre- and post-treatment digital models were landmarked and measured (R700 scanner and OrthoAnalyzer software, 3Shape, Copenhagen, Denmark). Anteroposterior position of the first molars was measured using the third medial rugae point as a reference. Anchorage loss (AL) represented the subtraction of the post-treatment distance from the pre-treatment distance for both right (ALR) and left (ALL) sides. The values were then compared using a two-way analysis of variance.

Results: There were 41 and 33 cases for the 0.018-inch and 0.022-inch bracket slot systems, respectively. The baseline characteristics were similar between groups, except for the presence or absence of anchorage devices (P = 0.050). Therefore, the analysis was run for the total sample and following exclusion of cases with anchorage devices. For the total sample: 0.018’’ ALR = 3.86 mm, ALL = 3.30 mm and 0.022’’ ALR = 3.73 mm, ALL = 3.47 mm. Both analyses revealed no statistically significant differences between the two appliance groups (P = 0.970 and 0.383).

Conclusions: Bracket slot size does not influence maxillary molar anchorage loss during orthodontic treatment.