A Preliminary Study of Intra-Alveolar Tooth Germ Movement in Maxillary Protraction Treatment

Introduction: This preliminary study aimed to explore whether maxillary protraction therapy using tooth-borne anchorage could influence the intra-alveolar position of unerupted maxillary posterior teeth in patients with skeletal Class III malocclusion. Methods: Seventeen patients treated with rapid maxillary expansion and facemask (RME/FM) were compared to five patients treated with miniplates and facemask (miniplate/FM), who served as a control group. Lateral cephalograms taken before and after treatment were analyzed to assess the horizontal and vertical movements of the maxillary central incisor, first molar, and the second premolar and second molar tooth germs. Results: The RME/FM group exhibited significantly greater mesial movement of both erupted teeth and intra-alveolar tooth germs compared to the control group. Notably, the second premolar and second molar tooth germs moved mesially by approximately 72% and 28%, respectively, of the first molar’s movement. No significant vertical differences were observed. A moderate correlation was found between the mesial movement of second molar germs and adjacent first molars. Conclusions: Maxillary protraction treatment using RME may unintentionally induce mesial displacement of developing tooth germs, potentially affecting arch length and molar relationship.