A novel method for evaluating forces present during RME treatment: a clinical pilot study

Maxillary constriction is a common condition, often resulting in maxillary crowding, functional shifts, asymmetric jaw growth and posterior crossbites. The standard of orthodontic care is treatment with a rapid maxillary expander (RME), which applies expanding forces on the maxilla via the turning of a jackscrew of the RME, with the goal of separating the midpalatal suture. Few studies have attempted to measure these forces.

The objective of this study was to pilot a novel method for measuring the forces of expansion. To do so, a novel calibration procedure was fine-tuned and utilized to enable a prediction to be made of the forces within the maxilla and dentition resisting expansion, estimated from the force needed to turn the key of the expander jackscrew.

Analysis corroborates previous findings that forces range from 0 to 20 lbs, with no decrease in forces following sutural separation, indicating that resistance to expansion is not due to the midpalatal suture alone. On average, forces increased approximately 500 grams per day (with a 2-turns per day activation schedule) prior to diastema formation, and 200 grams per day after diastema formation. Force increase per day prior to diastema formation was significantly age dependent. Older patients showed higher rates of load increase per day prior to diastema formation, and a more significant decrease in slope after diastema formation.