Supervisors info:
Χαλαζωνίτης Δημήτριος, Καθηγητής
Τσολάκης Απόστολος, Επίκουρος Καθηγητής
Σηφακάκης Ιωσήφ, Επίκουρος Καθηγητής
Summary:
Objective: To evaluate the hard tissue and facial profile changes in matched extraction and non-extraction Class I patients by the use of geometric morphometrics.
Subjects and Method: From a parent sample of 542 Class I patients, been subjected to discriminant analysis in a previous study, a subsample of 68 borderline cases, in regards to extraction modality, was obtained and analyzed. Of the borderline patients 34 were treated with extraction and 34 without extraction of 4 first premolars. The validity of the discriminant analysis in successfully identifying a borderline group of morphologically similar patients was examined by geometric morphometric methods. Inter- and intragroup skeletal and facial profile changes were evaluated morphometrically using pre- and post-treatment cephalometric radiographs. Permutation tests were conducted to test statistical significance, based on the Procrustes distances between group means.
Results: The discriminant analysis was validated. The post-treatment soft tissue differences were marginally significant (P=0.053, 10000 permutations), but not in the hard tissue skeletal component (P=0.078, 10000 permutations). The non-extraction group showed increase in overall hard tissue height (P<0.00, 10000 permutations), with slightly retruded upper and slightly protruded lower lip (P=0.027, 10000 permutations). The extraction group showed a significant retraction of the hard tissue and facial profile outline (P<0.00, 10000 permutations).
Conclusions: The choice of treatment modality in regards to extractions has a definite impact on the skeletal and soft tissue profile in Class I borderline patients. In patients treated by non-extraction similar changes were presented in the vertical direction, concerning hard tissue, whereas facial profile altered slightly. Patients treated by extractions exhibited vertical increase of skeletal structures and retroposition of the maxillary and mandibular alveolar osseous contours, followed by similar soft tissue changes mainly in the perioral area.
Keywords:
Borderline Class I cases, hard tissue profile, soft tissue changes, extraction vs non-extraction, discriminant analysis
