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.

Attachments are specific features of clear aligner treatment designed to ensure the aligner’s retention and the predictability of tooth movements. The properties of composite resin used for their reproduction play a relevant role to preserve their integrity and shape over the time. Thus, the aim of the present evaluation was to compare the mechanical properties and the wear performance of two nanocomposite by means of mechanical and tribological tests. Twelve samples for both flowable nanocomposite (FNC) and conventional nanocomposite (CNC) were created. The two nanocomposites differ in terms of filler volume and viscosity of the mixture. The following tests were performed: thermal analysis and burning test; flat instrumented indentation test and a compression stress relaxation test; tribological analysis. Wear evaluation was performed by means of a contact probe surface profiler and a TayMap software for the 3D analysis. A customized step-sliding test was conducted to simulate the clinical application of materials with a polymethyl methacrylate (PMMA) ball used as counterpart. Wear evaluation of both resin surfaces and PMMA ball was performed. No differences were found in terms of polymeric nature and quantity of nanoparticles in the matrix. FNC showed lower density values (1.62 g/cm³ ± 0.02) and inorganic percentage residue (41%) than the CNC (respectively 1.95 g/cm³ ± 0.01 and 23%). Significant differences in terms of decrement of stress values, elastic modulus (1,114.12 ± 91.39 MPa), and stress relaxation rate (24.39% ± 3.23) were observed for the CNC when compared to the FNC (respectively, 835.04 ± 184.73 MPa and 40.19% ± 4.65). FNC showed higher values of dynamic friction coefficient (0.72 ± 0.017) and more worn and deeper profiles than the conventional ones. The step-sliding test with a PMMA ball confirmed a higher friction coefficient for FNC and a greater wear of the PMMA surfaces when used against flowable samples. Lower viscosity of FNC ensures a better adaptation during clinical attachment fabrication, whereas it has a negative impact on mechanical properties. CNC showed greater performance and resistance under mechanical stresses than the flowable ones, resulting in being more suitable for clinical needs.

Aim. To assess the three-dimensional (3D) maxillomandibular and dental response to Balters Bionator (BB) and the Sander Bite Jumping Appliance (SBJA) in growing patients. Materials and Methods. Twenty-seven Class II division 1 patients (13 males, 14 females), consecutively treated with either the BB (9 females, 7 males; 10.1±1.6 years) or SBJA (5 females, 6 males; 11±1.9 years), were collected from a single orthodontic practice. All patients presented overjet ≥5 mm, full Class II or end-to-end molar relationship, mandibular retrusion. CBCT scans were available at T1 and after removal of the functional appliances (T2) with a mean interval of 18 months. The 3D location and direction of skeletal and dental changes with growth and treatment were quantitatively assessed. Statistical analysis was performed by means of Mann–Whitney U test (p<0.05). Results. Patients treated with the SBJA and BB orthopedic appliances presented, respectively, 4.7 mm and 4.5 mm of 3D displacement of the chin, with marked ramus growth of, respectively, 3.7 mm and 2.3 mm. While the mandible and maxilla grew downward and forward, no opening of the mandible plane was observed. Both appliances adequately controlled labial inclination of lower incisors (1.3° and 0.3°, for the SBJA and BB groups, resp.). No significant between-group differences were found for the T2−T1 changes for any of the variables, with the exception of molar displacements (significantly greater in the SBJA group than in the BB group, 1.2 mm and 0.9 mm, resp.). Conclusions. The maxillomandibular and dental growth responses to BB and SBJA therapies are characterized by vertical ramus growth and elongation of mandible that improve the maxillomandibular relationship with adequate control of lower incisor position.

Summary: Objectives: The objective of this study was to analyze soft tissue changes produced by rapid maxillary expansion and facial mask therapy in growing Class III patients.Materials: The treated group consisted of 32 Caucasian patients (15 females and 17 males) with dentoskeletal Class III malocclusion treated with the Face Mask Protocol (FMP, rapid maxillary expander, facial mask, and removable lower bite-block). All patients were evaluated before treatment (T1; mean age, 8.4 years), at the end of active treatment (T2; mean age, 10.7 years), and at a post-pubertal follow-up observation (T3; mean age, 15.8 years). The treated group was compared with a matched control group of 20 untreated subjects (10 females and 10 males) with dentoskeletal Class III malocclusion. Statistical comparisons between two groups were performed with the independent samples t-test (P < 0.05).Results: Significant improvements were found during the long-term T1–T3 interval for profile facial angle (–5.8°), nasolabial angle (–4.4°), mandibular sulcus (–10.3°), upper lip protrusion (+0.7 mm), and lower lip protrusion (–1.1 mm) in the treated group. No significant post-pubertal effects were found in terms of lower face percentage between two groups.Limitations: This study has a retrospective design and it used a historical control sample.Conclusion: The FMP induced positive effects on soft tissue facial profile with a good long-term post-pubertal stability.

To evaluate load and stress distribution on Delaire facemask (FM) during maxillary protraction in class III growing patients by means of finite element analysis (FEA). A three-dimensional geometry of a Delaire FM was reconstructed from the original CAD 3D prototype, using software package (ANSYS 5.7). FM presented forehead and chin supports and stainless steel framework characterized by two lateral vertical bars connected to a crossbar with two pawls for elastic attachment. Two traction intensities (7.8 and 9.8 N) were applied on the FM pawls along three different downward inclined directions with respect to the occlusal plane (0°, 30°, or 50°, respectively). Resulting stresses and deformations were then tested through the von Mises yield criterion in order to underline the FM wear performance. The analysis showed that higher stresses and deformations are mostly related to axial forces of 9.8 N rather than 7.8 N. Stresses also progressively increased with increasing downward force inclinations (0°, 30°, and 50° with respect to the occlusal plane). The overall tensions were inferior to the limit of the elastic behavior (yield point) characterizing the material they are applied on. Thus, the FM structure absorbed the load applied with an elastic deformation of the lateral and horizontal bars. Resulting stresses and deformations were directly proportional to protraction load amounts and to increasing downward inclination of forces. In all tested conditions, protraction forces were not able to determine plastic deformation on FM structure compromising its performance and efficiency.