Longitudinal behavior of orthodontic extraction spaces: A retrospective dental cast analysis

This retrospective study aimed to qualitatively and quantitatively evaluate orthodontic extraction space behavior and size at the end of treatment and the short- and long-term stages in Class I, II, and III malocclusions.

The sample comprised records of 1283 orthodontic patients treated with extractions (cross-sectional group). From these patients, 1- and 5-year posttreatment records of 214 patients were additionally evaluated (longitudinal group). Orthodontic extraction sites of immediate (end of treatment), short-term (1-year posttreatment), and long-term (5-year posttreatment) stage dental casts were measured with a digital caliper. Extraction spaces were classified according to their qualitative behavior in the open, closed, reopened, and recently closed spaces. Space qualitative longitudinal behavior was compared among the malocclusion types with chi-square tests. Kolmogorov-Smirnov normality tests were performed to check the variable's distribution. All variables showed normal distribution, except the malocclusion group ages. Therefore, parametric tests were used for all comparisons between the malocclusion groups, except for age comparisons in each stage, which were compared with the Kruskal-Wallis tests. Thus, space size and its reduction were compared among the 3 stages, in general, and between the maxillary and mandibular arches, with analysis of variance followed by Tukey tests and t tests, respectively.

Classes I, II, and III malocclusion patients presented similar ages at each stage. At the end of treatment, 71.4% and 65.1% of the quadrants were closed in the cross-sectional and longitudinal groups, respectively, and 43.6% and 38.2% of patients presented all quadrants closed at this same stage in both groups. The reopening and late closure tendencies were 2.9 and 2.3 times greater in the short term than in the long term. Reopening tendency in the short-term was greater in Class II than in Class I malocclusion. Of the quadrants closed at the end of treatment, 87% were stable in the long term. From the quadrants with residual spaces at the end of treatment, 28.4% persisted openly in the long term. Residual space size reduced significantly in the short and long term, primarily in the mandibular arch.

The percentage of patients with residual spaces at the end of treatment was 56.4%. Space reopening and late closure occur mainly in the first year after treatment. There was long-term stability in 87% of the quadrants closed at the end of treatment. There was a significant reduction in orthodontic extraction space size in the short and long term, especially in the mandibular arch.