Leveling the curve of Spee: Comparison between continuous archwire treatment and Invisalign system: A retrospective study

Abstract

The purpose of this study was to evaluate and compare leveling of the curve of Spee (COS) achieved by traditional fixed appliances and Invisalign clear aligners (Align Technology, Santa Clara, Calif). This retrospective study involved 2 groups of subjects with an increased COS depth. Patients treated with the Invisalign system (I group) and patients treated with the standard edgewise full-fixed appliance (Fgroup). The I group included 30 subjects (13 males, 17 females; mean age, 24 years 5 months ± 19 months). The F group included 32 subjects (12 males, 20 females; mean age, 22 years 4 months ± 21 months). The 2 groups were matched for sex, age, vertical pattern, and observation period. Pretreatment (T0) and posttreatment (T1) lateral cephalograms were analyzed. COS depth was measured on digital dental casts. The intragroup variation between T0 and T1 was analyzed with a paired t test. The intergroup variation was evaluated using an unpaired t test. The leveling of COS was statistically significant, comparing T0 and T1 within the groups. The F group presented a statistically significant extrusion of posterior teeth, with a flaring of the mandibular incisors. The I group showed a statistically significant intrusion of the mandibular incisors, with excellent control in the proclination of incisors during the intrusion movement. Traditional continuous archwire treatment and the Invisalign system effectively level the COS.