Soft tissue changes: a comparison between changes caused by the construction bite and by successful treatment with a modified Twin-block appliance

Comparison Study of Extraction Accuracy of 3D Facial Anatomical Landmarks Based on Non-Rigid Registration of Face Template

(1) Background: Three-dimensional (3D) facial anatomical landmarks are the premise and foundation of facial morphology analysis. At present, there is no ideal automatic determination method for 3D facial anatomical landmarks. This research aims to realize the automatic determination of 3D facial anatomical landmarks based on the non-rigid registration algorithm developed by our research team and to evaluate its landmark localization accuracy. (2) Methods: A 3D facial scanner, Face Scan, was used to collect 3D facial data of 20 adult males without significant facial deformities. Using the radial basis function optimized non-rigid registration algorithm, TH-OCR, developed by our research team (experimental group: TH group) and the non-rigid registration algorithm, MeshMonk (control group: MM group), a 3D face template constructed in our previous research was deformed and registered to each participant’s data. The automatic determination of 3D facial anatomical landmarks was realized according to the index of 32 facial anatomical landmarks determined on the 3D face template. Considering these 32 facial anatomical landmarks manually selected by experts on the 3D facial data as the gold standard, the distance between the automatically determined and the corresponding manually selected facial anatomical landmarks was calculated as the “landmark localization error” to evaluate the effect and feasibility of the automatic determination method (template method). (3) Results: The mean landmark localization error of all facial anatomical landmarks in the TH and MM groups was 2.34 ± 1.76 mm and 2.16 ± 1.97 mm, respectively. The automatic determination of the anatomical landmarks in the middle face was better than that in the upper and lower face in both groups. Further, the automatic determination of anatomical landmarks in the center of the face was better than in the marginal part. (4) Conclusions: In this study, the automatic determination of 3D facial anatomical landmarks was realized based on non-rigid registration algorithms. There is no significant difference in the automatic landmark localization accuracy between the TH-OCR algorithm and the MeshMonk algorithm, and both can meet the needs of oral clinical applications to a certain extent.

Three-Dimensional Evaluation of Soft Tissue Changes after Functional Therapy

This study was aimed at proposing a three-dimensional (3D) evaluation method for the soft tissue effects of Twin Block (TB) functional appliance therapy by using cone beam computed tomography (CBCT) images. In this retrospective study, a total of 60 pre- and posttreatment (T0 and T1) CBCT images of Class II patients with mandibular retrognathia treated with a TB appliance were used. Volumetric and linear soft tissue changes were evaluated quantitatively with 3D measurements and qualitatively with color mapping visual. Linear (NV-A and NV-Pog) and angular (SNA, SNB, and ANB) skeletal changes were also measured on 3D images. The Wilcoxon signed-rank test was used to compare statistical differences, and the scores of male and female participant differences were observed with the Mann-Whitney U test. In this study, a decrease was observed in SNA (p < 0.05), ANB (p < 0.01), and NV-Pog (p < 0.05) while an increase in SNB (p < 0.01) was found. However, decrease in NV-A distance was not statistically significant (p > 0.05). As a result of the evaluation of soft tissue changes, while the anterior reposition of the lower lip, soft tissue pogonion, and soft tissue gnathion was found to be significant (p < 0.01, p < 0.01, and p < 0.05, respectively), the upper lip and subnasale repositions were not statistically significant (p > 0.05). 3D soft tissue changes after TB therapy can be evaluated quantitatively and qualitatively by using CBCT images. Anterior repositioning of the mandible with functional therapy also provides improvement in soft tissue profile, especially in the lower facial region.

Evaluation of Profile Changes in Class II Individuals Treated by Means of Herbst Miniscope Appliance

Background: To evaluate the profile changes following orthopedic/orthodontic treatment with the Herbst Miniscope^® appliance in subjects affected with Class II malocclusion with mandibular retrusion. Methods: A total of 44 patients presenting a skeletal Angle Class II malocclusion (ANB > 4°) due to mandibular retrusion and a cervical maturation stage between CS2 and CS3 were included in the study. Of these 44 patients, 22 (mean age 11.9 ± 1.3, HBT group) were treated using the Herbst appliance, while 22 (mean age 10.6 ± 1.3, CTR group) were followed for a 12-month observational period. A cephalometric tracing was performed at the beginning of treatment (T0) and after 12 months (T1). Results: In both groups there was a significant advancement of soft tissue pogonion (HBT = 3.5 ± 3.0 mm, p < 0.001; CTR = 2.2 ± 2.9 mm, p < 0.001), but the difference between the two groups was not significant (p = 0.172). On the contrary, both groups had a significant advancement of the mandibular sulcus (HBT = 3.7 ± 2.8 mm, p < 0.001; CTR = 1.2 ± 2.2 mm, p < 0.001) and a lower lip protrusion (HBT = 3.45 ± 2.51 mm, p < 0.001; CTR = 1.7 ± 2.7 mm, p = 0.008), but in both cases the HBT group showed a statistically significant greater increase in sulcus protrusion (p = 0.002) and lower lip protrusion (p = 0.029) than controls. There were no statistically significant effects on the upper jaw. Conclusions: The Herbst appliance advanced the lower jaw soft tissues.