Background
To compare the effects of rapid maxillary expansion (RME) and alternate rapid maxillary expansions and constrictions (Alt-RAMEC) protocols on tooth root development in patients with Class III skeletal malocclusion treated with a face mask (FM).

Methods
This retrospective clinical study included 40 patients with Class III skeletal malocclusions treated with Petit-type FMs. The first group comprised 20 patients (6 females and 14 males) treated with the RME protocol and a FM (RME/FM). The second group comprised 20 patients (9 females and 11 males) treated with the Alt-RAMEC protocol and a FM (Alt-RAMEC/FM). The root lengths of maxillary and mandibular canines, premolars, and first molars were measured using dental panoramic radiographs before and after treatment.

Results
The RME/FM group showed significant length increases in the upper right second premolars and all mandibular premolars. The Alt-RAMEC/FM group showed significant length increases in the mandibular and maxillary premolars. Intergroup comparisons showed that the lengths of the maxillary second premolars and right first premolars were significantly shorter in the RME/FM group than in the Alt-RAMEC/FM group.

Conclusion
In both protocols, no significant negative effects depend on the expansion procedures applied to the maxilla on root development was observed. Although the amount of root development of some teeth differed between the groups, it can be said that the effects of RME and Alt-RAMEC protocols on root development were clinically similar when the patients’ ages and individual differences are taken into consideration.