Skeletal & soft tissue changes in extraction vs non extraction orthodontic treatment evaluated with geometric morphometrics
A research conducted at the Department of Orthodontics, Dental School, National & Kapodistrian University of Athens, Greece
"A geometric morphometric evaluation of hard and soft tissue profile changes in borderline extraction versus non-extraction patients" published in European Journal of Orthodontics, Volume 41, Issue 3, June 2019, Pages 264–272,
Afroditi Kouli , Alexandros Papagiannis, Nikoleta Konstantoni, Demetrios J. Halazonetis, Dimitrios Konstantonis
Objectives: To evaluate the hard tissue and facial profile changes in matched extraction and nonextraction Class I patients by the use of geometric morphometrics.
Subjects and Methods: From a parent sample of 542 Class I patients, previously subjected to discriminant analysis, a subsample of 68 borderline cases was obtained, 34 treated with extraction and 34 without extraction of 4 first premolars. Geometric morphometric methods (Procrustes superimposition and Principal Component Analysis) were applied on cephalometric tracings to assess the validity of the discriminant analysis in successfully identifying a morphologically homogeneous group and to evaluate inter- and intra-group skeletal and facial profile shape changes.
Results: No significant pre-treatment shape difference between the two groups was found, thus validating the discriminant analysis. The non-extraction group showed increase in hard tissue facial height (P < 0.001), with slight lower lip retrusion and upper lip protrusion (P = 0.027). The extraction group showed retraction of the hard tissue and facial profile outline (P < 0.001). Permutation tests for post-treatment inter-group differences resulted in P = 0.054 for the soft tissue outline and P = 0.078 for the hard tissue skeletal component.
Conclusions: The evidence indicates that borderline cases treated with four premolar extractions will exhibit lip retrusion compared to non-extraction treatment.
#orthodontics #extractions #profile changes #discriminant analysis #geometric morphometrics
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