Background: The objective of this retrospective study was to analyze the morphological changes of the upper arch after two protocols of expansion, the Invisalign® First system and rapid maxillary expansion (RME), in mixed dentition by means of geometric morphometric analysis (GMM). Methods: Digital dental casts of 32 children treated either with RME (RME group: 17 subjects; mean age 8.1 years) or the First system (First group: subjects; mean age 8.4 years) were collected. For both the RG and FG, pre-(T1) and post-treatment(T2) digital models were created. A total of 14 landmarks were digitized and GMM was applied. Procrustes analysis and principal component analysis (PCA) were performed. Results: The PC1 resulting from the T2–T1 comparison in the RG g showed statistically significant morphological changes in the posterior region of the upper arch shape, without significant variations in the anterior region. The comparison of the T2–T1 changes in the FG showed an increase in the transverse dimension at the level of the canine and the first deciduous molar widths, with morphological variation in the anterior region due to frontal teeth alignment. Conclusions: The First system induced shape modifications of the upper arch during expansion in contrast to RME. The FG presented an improvement in the maxillary arch shape, while the RG maintained the initial triangular shape.

(1) Background: The nature of the changes that contribute to Class II correction with functional appliances is still controversial. A broad variation in treatment responses has been reported. The purpose of this study was to find cephalometric predictors for individual patient responsiveness to twin-block treatment in patients with Class II Division 1 malocclusion; (2) Methods: The study was performed on a sample of 39 pubertal patients (21 females, 18 males) treated with the twin block appliance. Lateral cephalograms were available at the start of the treatment (T1) and at the end of functional therapy (T2). The outcome variable was the T2–T1 change in the sagittal position of the soft tissue pogonion with respect to the vertical line perpendicular to the Frankfort plane and passing through point subnasale. The predictive variables were age, gender at T1, and all the cephalometric parameters measured T1. Forward stepwise linear regression with p value to enter 0.05 and p value to leave 0.10 was applied; (3) Results: The only significant predictive variable that was selected was the Co–Go–Me angle (p = 0.000); (4) Conclusions: A greater advancement of the soft tissue chin on the profile is expected with smaller pretreatment values of Co–Go–Me angle.

Objective: The aim of the present retrospective study was to compare the changes resulting from treatment using the MA and the TB with special regard to the oro-and naso-pharyngeal sagittal airway dimensions in subjects with dentoskeletal Class II malocclusions and positive history of Sleep Disorder Breathing (SDB) diagnosed through the Pediatric Sleep Questionnaire (PSQ).Materials and methods: This retrospective study involved 2 groups of subjects: patients treated with Twin Block (TB group: n = 22, 10 males, 12 females; mean age 12.0 ± 1.3 years) and patients treated with Mandibular Advancement (MA group: n = 23, 11 males, 12 females; mean age 12.2 ± 1.1 years). Pretreatment (T1) and posttreatment (T2) lateral cephalograms were analyzed. All patients underwent the PSQ to diagnose SDB.Results: In both treated groups there was an increase in the airways dimensions and an improvement in symptoms related SDB. The statistical comparison of the changes between T1 and T2 in the TB group showed a significant increment in upper airway size (PNS-AD2, +1.50 mm + −3.30; McNamara's upper pharynx dimension, +2.21 + −4.21) after active treatment. The MA group showed similar results during active treatment with a significant increase in both upper (PNS-AD2, +2.72 + −2.65; McNamara's upper pharynx dimension, +2.97 + −3.07) and lower (PNS-AD1, +2.17 mm + −3.54) airway size.Conclusions: Despite the different structure of these two devices and the different advancement protocols, both appliances were valuable as a suitable treatment option for Class II patients with respiratory disorders, inducing an increase of upper and lower airway size and a significant reduction in diurnal symptoms.

Background: to compare the effects of two different expansion protocols in terms of bi-dimensional linear, angular measurements, and three-dimensional analysis of palatal area on digital casts in patients with mixed dentition. Methods: digital casts of 32 children treated with the RME (RG: 17 subjects), or with clear aligners (FG: 15 subjects) were collected. Linear and angular values were measured in both groups on the upper arch for each pre (T1) and post-treatment (T2) models, as well as palatal area. Unpaired t-test was used to test significant differences between groups (p<0.05). Results: the comparison of T2-T1 changes for linear measurements between groups showed significant differences in the inter-canine width (+1.5mm in FG), in the first inter-deciduous molar width (+1.5mm in FG), in the first inter-molar distal width (-1.2mm in FG), in the inter-canine transpalatal width (+1.5mm in FG) and in the first inter-deciduous molar transpalatal width (+1.4mm in FG). The analysis of angular measurements showed a significant increase of the crown angulation for all the teeth in FG except for the second deciduous molars and for the first molars. First molars showed a reduction of this parameter. FG patients showed a greater increase of the palatal area. Conclusions: the comparison between FG and RG groups pointed out that clear aligners system seems to be more efficient than RME in terms of expansion obtainable at the anterior segment of the arch with a better control of upper first molar crown angulation and a greater increase of the palatal area.