Anchorage reinforcement with miniscrews and molar blocks in adolescents: A randomized controlled trial

Anchorage can be reinforced in many ways. Due to the variety of anchorage concepts, only a few general conclusions can be drawn. Therefore, more research is needed to investigate specific concepts with specific indications. The objective of this trial was to compare the anchorage capacities of miniscrews and molar blocks.

This randomized controlled trial was conducted on 2 parallel arms. The trial was conducted at the Public Dental Service Orthodontic Clinic in Gävle, Sweden. Participants were adolescents who needed orthodontic treatment with a fixed appliance, extraction of the maxillary first premolars, and anchorage reinforcement. In group A, miniscrews were used as direct anchorage during space closure. In group B, molar blocks were used as anchorage reinforcement during leveling and alignment and space closure. The primary outcome was loss of anchorage assessed as maxillary first molar movement. Random allocation was maintained with a simple randomization stratified by sex. The observer was blinded to the allocations during the measurements.

Forty participants each were randomized to groups A and B. Results were analyzed on an intention-to-treat basis, meaning that all participants, successful or not, were included in the analysis. Group A showed a mean anchorage loss of 1.2 mm during leveling and alignment. During space closure with miniscrews, no significant anchorage loss was found. Group B showed mean anchorage losses of 1.4 mm during leveling and alignment and 2.4 mm during space closure. No serious harms were detected. The first molar rotation, torque, and tipping showed different characteristics during the treatment phases.

Miniscrews can be recommended for anchorage reinforcement. Depending on the need for anchorage reinforcement, miniscrews can be inserted at the beginning of treatment or when space closure starts. Molar blocks cannot be recommended for anchorage reinforcement.

This trial was registered at www.clinicaltrials.gov (NCT02644811).

The protocol was published after trial commencement.

This trial received funding from the Center for Research and Development, Uppsala University/Region Gävleborg; Thuréus Foundation for the Promotion of Dental Science; and the Swedish Dental Associations Scientific Funds.