Vertical skeletal changes after extraction and non-extraction treatment in matched class I patients identified by a discriminant analysis: cephalometric appraisal and Procrustes superimposition

Abstract

BackgroundIn the long-lasting debate of extraction versus non-extraction treatment, the impact of extractions on the skeletal vertical dimension remains rather unclear. The aim of this retrospective research study was to obtain a bias-free sample of morphologically similar borderline patients treated with or without extraction of the four first premolars and to retrospectively evaluate the vertical changes that occurred.MethodsA borderline sample of 83 patients, 41 treated with four first premolar extractions and 42 treated without, was obtained by means of discriminant analysis applied to a previously investigated parent sample of 542 class I patients. The pretreatment and posttreatment cephalometric radiographs were analyzed digitally, and seven measurements were assessed for vertical skeletal changes. Also, average tracings between the two treatment groups were evaluated using the Procrustes superimposition method.ResultsThe variables of SN to Go-Gn and Y-axis showed adjusted intergroup differences of − 0.91° and − 1.11° (P = 0.04). Comparing the mean intra-group differences of all the variables simultaneously, a significant difference was found between the two treatment groups (overall P value = 0.04). In the extraction group, only the gonial angle showed a significant decrease (P = 0.01) while the overall P value evaluating the intra-group differences between pre- and posttreatment was significant (overall P value < 0.01). In the non-extraction group, the variable of N-ANS/N-Me showed a significant decrease (P = 0.02) and the overall P value evaluating the intra-group differences between pre- and posttreatment was also significant (overall P value < 0.01). Differences in treatment duration were assessed using a log-normal model and showed that extraction treatment lasted significantly longer than non-extraction treatment (P < 0.01).ConclusionsThe borderline group of patients identified by the discriminant analysis exhibited similar morphological characteristics at treatment’s onset; therefore, the posttreatment changes could safely be attributed to the choice of extraction or non-extraction treatment and not to pre-existing differences. Treatment choice had an impact on the patients’ vertical skeletal dimensions. Patients treated with four first premolar extractions showed a slight decrease in the vertical skeletal measurements, whereas non-extraction patient treatment showed a slight increase. The treatment time was also significantly higher in the extraction group.

Dentoskeletal and facial features comparison between individuals treated with four first premolar extraction in the 1970s and in the new millennium

“…Both groups showed a predominant hyperdivergent growth pattern. These findings were expected considering that previous studies have indicated four first premolar extraction in patients with hyperdivergent pattern [48][49][50] . The control of the vertical dimension was thought to occur by a counterclockwise rotation of the mandible through the forward movement of posterior teeth.…”

“…Hyperdivergent patients are usually treated with extractions, due to the better vertical control by a counterclockwise rotation of the mandible through the forward movement of posterior teeth . Despite the absence of significant vertical changes reported between extraction and nonextraction treatments, greater vertical development is expected with nonextraction approaches BEIT et al, 2017). Vertical component analysis showed a significantly increased LAFH for group 2, which is in accordance with other studies that indicated extractions in patients with increased LAFH BEIT et al, 2017).…”

“…Despite the absence of significant vertical changes reported between extraction and nonextraction treatments, greater vertical development is expected with nonextraction approaches BEIT et al, 2017). Vertical component analysis showed a significantly increased LAFH for group 2, which is in accordance with other studies that indicated extractions in patients with increased LAFH BEIT et al, 2017). Group 2 showed an increased lower anterior facial height and a greater development of maxillary incisors and molars compared to group 1.…”

“…The control of the vertical dimension was thought to occur by a counterclockwise rotation of the mandible through the forward movement of posterior teeth. [48][49][50] A greater increase in the LAFH has been observed after nonextraction treatment when compared to extraction treatment. 48,51,52 Our results are in accordance with the indication of four first premolar extractions predominantly in hyperdivergent pattern, both in the 1970s decade and in the new millennium.…”

“…[48][49][50] A greater increase in the LAFH has been observed after nonextraction treatment when compared to extraction treatment. 48,51,52 Our results are in accordance with the indication of four first premolar extractions predominantly in hyperdivergent pattern, both in the 1970s decade and in the new millennium. Group 2 showed an increased lower anterior facial height and a greater development of maxillary incisors and molars compared to group 1 (Table III).…”