[Soft and hard tissue changes of hyperdivergent class Ⅱ patients before and after orthodontic extraction treatment]

To investigate the hard and soft tissue changing trend and contributing factors of skeletal class Ⅱ hyperdivergent patients before and after orthodontic camouflage treatment by analyzing the cephalogram and the three dimensional (3D) facial scan data.

Eighteen skeletal class Ⅱ hyperdivergent adult female patients who finished camouflage orthodontic treatment were selected. Skeletal and dental measurements were carried out with the cephalometric analysis before and after the treatment. 3D facial data before and after orthodontic treatment were acquired and the anatomical landmarks were set after the repositioning and superimposition process. Hard tissue measurement included 17 mea-surement indicators (sella-nasion-subspinale angle, sella-nasion-supramental angle, subspinale-nasion-supramental angle, facial angle, angle of convexity, Frankfort horizontal plane-mandibular plane angle (FH-MP), Y axis angle, sella-nasion plane-mandibular plane angle (MP-SN), pogonion-nasion-supramental distance, upper incisor-nasion-subspinale distance, upper incisor to sella-nasion, lower incisor-nasion-supramental distance, lower incisor-nasion-supramental angle, upper incisor to lower incisor, upper incisor to sella-nasion, lower incisor-mandibular plane angle, and Z angle), and the changes before and after treatment were measured for 11 of them. Twenty soft tissue landmarks (left/right cheekbone, left/right chelion, left/right crista philtra, soft tissue gnathion, left/right gonion, glabella, labrale infe-rius, labrale superius, soft tissue menton, left/right mid-mandibular border, soft tissue pogonion, stomion superius, sublabial, subnasale, and supralabial) and 9 soft tissue indicators (lower lip height, facial convexity, lower vermilion height, mandibular contour, nasolabial angle, philtral length, philtral width, upper lip height, and upper vermilion height) were measured and recorded for treatment changes. Linear-regression analysis and correlation analysis were carried out for analyzing the relationship between hard and soft tissue changes before and after the treatment.

Significant differences were noticed for 18 out of the 20 cephalometric measurements and facial measurements before and after the treatment (P < 0.05), which mainly represented the sagittal retraction of lip area after the treatment. Significant vertical displacements were revealed for soft tissue menton after treatment [(1.88±2.61) mm, P < 0.05]. Significant sagittal displacements were revealed for left/right cheilion [(-2.95±1.9) mm, (-2.90±1.92) mm], labrale inferius[(-4.94±1.95) mm], labrale superius[(-3.25±1.44) mm], sublabial [(-3.10±3.5) mm], and subnasale [(-1.23±1.06) mm] after treatment (P < 0.05). An average of 4.10°±2.57° increasement was noticed for Z angle after treatment. High correlation (r>0.7) was noticed for the displacement of menton after treatment with FH-MP, with the rate of -0.183 :1, and MP-SN, with the rate of -0.157 :1. Moderate correlations (0.7≥r>0.4) were noticed for the other measurements with correlations (P < 0.05).

A certain extent of facial improvements could be achieved with orthodontic camouflage treatment for skeletal class Ⅱ hyperdivergent patients, which were mostly represented by the improvement of sagittal relationship of nose, lips, and chin. Certain correlations were noticed for the hard and soft tissue changes.