Hispanic adolescent lip response to extraction and nonextraction orthodontic treatment

In orthodontics, treatment aims to improve the patient's occlusion and overall facial appearance. Extraction of 4 first premolars may improve the occlusion, but it may negatively impact a patient's facial harmony and create a "dished-in" appearance. Although many studies in orthodontic literature reviewed Caucasian patient soft-tissue change throughout extraction treatment, there is a void in the literature regarding Hispanic patients, who have different soft-tissue characteristics and may respond differently to extraction therapy. This study aimed to determine the influence of first premolar extractions on soft-tissue profile in Hispanic adolescents and whether there is a correlation between pretreatment lip strain and lip movement throughout treatment.

Lateral cephalograms and study models of 60 Hispanic patients were evaluated at pretreatment and posttreatment stages. Patients were divided into nonextraction and extraction groups and further subdivided on the basis of pretreatment lip strain. Cephalometric analyses were compared between the groups and subgroups, and a correlation analysis was conducted.

There was a significant difference in lip position change between nonextraction and extraction groups. There was a significant increase in upper vermillion lip thickness in the extraction group. There was no significant difference in lip position change between the minimal and moderate-severe lip strain extraction groups. There was no significant correlation between pretreatment crowding or lip strain and lip position change.

Hispanic patients' lips may retract less than Caucasian patients' lips in response to extraction treatment. Pretreatment lip strain and crowding may have less effect on retrusive lip movement than in Caucasian patients.