Tianmin Xu

Backgrounds: With the development of straight wire appliance (SWA), especially the rountine use of nickel‐titanium (NiTi) archwires in the initial stage has largely eliminated the need for bending up. However, engaging fine NiTi wire into the molar buccal tube with built‐in forward tipping prescription can induce unintended mesial tipping and mesialization of maxillary molars, leading to early anchorage loss. This single‐center, two‐arm parallel randomized clinical trial aimed to compare the physiologic anchorage spee‐wire system (PASS) with the Mclaughlin‐Bennet‐Trevici straight‐wire system (MBT) in terms of their ability to preserve maxillary anchorage control during the alignment and leveling. Methods: Sixty‐four patients with Angle Class I or II malocclusion undergoing maxillary first premolar extraction were recruited. Minimal randomization was used to select the sample. Two bracket systems were used—PASS and MBT. Digital dental models were acquired at pre‐treatment(T0), the first 3 months during treatment(T1), and the first 6 months during treatment(T2). Study models of different time point were superimposed to evaluate movements of maxillary first molars, canines, and central incisors. Results: During the first 6 months of the treatment, maxillary first molars in the PASS group exhibited distal tipping (2.67° ± 4.59°) and distal movement (0.03 ± 1.02 mm). In contrast, the MBT group showed mesial tipping (1.95° ± 3.04°) and mesial movement (0.67 ± 0.79 mm). Additionally, the maxillary canines also exhibited treatment difference. The increase of inter‐canine width was significantly smaller increased in the PASS group (1.31 ± 2.00 mm) compared to the MBT group (2.37 ± 1.72 mm). No other difference was found. Conclusion: Compared with the MBT system, PASS was better at preserving maxillary anchorage during the alignment and leveling stage. These findings suggest that PASS offers superior physiological anchorage control in the early stages of treatment without the need for auxiliary appliances.

Objective: This study aims to analyse and compare the subjective evaluations of post‐orthodontic treatment profile photos and cephalometric radiographs by Chinese orthodontic experts, along with their correlation to objective measurements. Materials and Methods: A total of 216 cases treated at Peking University School of Stomatology (2016–2021) were included. Sixty‐five Chinese orthodontic experts conducted subjective ranking and grading of post‐treatment profile photos and lateral cephalograms, while three doctoral students performed objective cephalometric analyses. Statistical analyses were used to identify and compare objective indices correlated with expert assessments, determine their weightings, and establish thresholds distinguishing ‘harmony’ from ‘disharmony’. Results: Experts' subjective evaluations of profile photos and cephalograms showed moderate agreement. Five objective indices correlated with facial photograph evaluations (two skeletal: ANB, MP/SN; three soft tissue: Sn‐GPos, UL‐E, Bs‐GPos), while eight indices were associated with cephalogram assessments (including additional skeletal and dental indices: ANB, MPA, Pog‐NB, U1/PP, L1/MP, Sn‐GPos, UL‐GPos, Bs‐GPos). ROC analysis determined that a threshold of 3.30 points could differentiate ‘harmony’ from ‘disharmony’ for both modalities. Conclusion: Experts' subjective assessments are significantly associated with multiple objective cephalometric parameters, particularly those related to incisor inclination, skeletal relationships, and labiomental morphology. Regression analysis suggests that a combination of these indices can reasonably predict expert evaluations. Compared to facial photographs, cephalogram assessments place greater emphasis on incisor inclination and chin morphology.

Background: Yes-associated protein (YAP) is a crucial mechanosensor involved in mechanotransduction, but its role in regulating mechanical force-induced bone remodeling during orthodontic tooth movement (OTM) is unclear. This study aims to elucidate the relationship between mechanotransduction and mechanical force-induced alveolar bone remodeling during OTM. Results: Our study confirms an asynchronous (temporal and spatial sequence) remodeling pattern of the alveolar bone under mechanical force during OTM. Both compression and tension activate osteoclasts recruiting to the alveolar bone, whereas no significant presence of osteoblasts in the alveolar bone at the early stages of bone remodeling. Specifically, applying different force magnitudes (10, 25, 50, 100 g) to rats’ 1st molars affected OTM distance. Force-induced alveolar bone remodeling was characterized by osteoclastogenesis and YAP activation at compressive/tensile sites on day 1 of OTM. Notably, 25 g force triggered peak YAP expression and osteoclastic activity early on. Time-course analysis revealed two YAP activity peaks on day1 and 14, contrasting with one peak of type I collagen expression on day14. In addition, RNA-sequencing highlighted increased nuclear factor kappa B (NF-κB) signaling, mineral absorption, and osteoclast differentiation at day-1 and 3. Moreover, gene expression analysis showed similar trends for NF-κB p65, YAP1, and TEA domain 1 (TEAD1) during this time. Furthermore, experiments on osteoclast cultures indicated YAP activation via large tumor suppressor (LATS) and TEAD under mechanical stimuli (compression/tension), promoting osteoclastogenesis by regulating NF-κB p65 and receptor activator of NF-κB (RANK). Inhibiting YAP with verteporfin delayed OTM by impairing force-induced osteoclastic activities in vivo and ex-vivo. Conclusions: We propose that YAP mediates alveolar bone remodeling through NF-κB p65-induced osteoclastogenesis in an asynchronous remodeling pattern during OTM. Both compression and tension activate osteoclasts recruiting to the alveolar bone at early stages of bone remodeling, offering evidence for orthodontists as a reference.

The determining effect of facial hard tissues on soft tissue morphology in orthodontic patients has yet to be explained. The aim of this study was to clarify the hard-soft tissue relationships of the lower 1/3 of the face in skeletal Class II-hyperdivergent patients compared with those in Class I-normodivergent patients using network analysis. Fifty-two adult patients (42 females, 10 males; age, 26.58 ± 5.80 years) were divided into two groups: Group 1, 25 subjects, skeletal Class I normodivergent pattern with straight profile; Group 2, 27 subjects, skeletal Class II hyperdivergent pattern with convex profile. Pretreatment cone-beam computed tomography and three-dimensional facial scans were taken and superimposed, on which landmarks were identified manually, and their coordinate values were used for network analysis. (1) In sagittal direction, Group 2 correlations were generally weaker than Group 1. In both the vertical and sagittal directions of Group 1, the most influential hard tissue landmarks to soft tissues were located between the level of cemento-enamel junction of upper teeth and root apex of lower teeth. In Group 2, the hard tissue landmarks with the greatest influence in vertical direction were distributed more forward and downward than in Group 1. (2) In Group 1, all the correlations for vertical-hard tissue to sagittal-soft tissue position and sagittal-hard tissue to vertical-soft tissue position were positive. However, Group 2 correlations between vertical-hard tissue and sagittal-soft tissue positions were mostly negative. Between sagittal-hard tissue and vertical-soft tissue positions, Group 2 correlations were negative for mandible, and were positive for maxilla and teeth. Compared with Class I normodivergent patients with straight profile, Class II hyperdivergent patients with convex profile had more variations in soft tissue morphology in sagittal direction. In vertical direction, the most relevant hard tissue landmarks on which soft tissue predictions should be based were distributed more forward and downward in Class II hyperdivergent patients with convex profile. Class II hyperdivergent pattern with convex profile was an imbalanced phenotype concerning sagittal and vertical positions of maxillofacial hard and soft tissues.

Background: Orthodontic tooth movement (OTM) in a region containing alveolar bone defects with insufficient height and width is hard to achieve. Bovine bone mineral (Bio-Oss) is available to restore the alveolar defect; however, whether the region augmented with a bovine bone mineral graft (BG) is feasible for OTM, and the mechanisms by which macrophages remodel the BG material, is uncertain under the mechanical force induced by OTM. Material and methods: Rats were divided into three groups: OTM (O), OTM + BG material (O + B), and Control (C). First molars were extracted to create bone defects in the O and O + B groups with bovine bone mineral grafting in the latter. Second molars received OTM towards the bone defects in both groups. After 28 days, maxillae were analyzed using microfocus-computed tomography (μCT) and scanning-electron-microscopy (SEM); and macrophages (M1/M2) were stained using immunofluorescence. THP-1 cell-induced macrophages were cultured under mechanical force (F), BG material (B), or both (F + B). Phagocytosis-related signaling molecules (cAMP/PKA/RAC1) were analyzed, and conditioned media was analyzed for MMP-9 and cytokines (IL-1β, IL-4). Results: Our study demonstrated that alveolar defects grafted with BG materials are feasible for OTM, with significantly increased OTM distance, bone volume, and trabecular thickness in this region. SEM observation revealed that the grafts served as a scaffold for cells to migrate and remodel the BG materials in the defect during OTM. Moreover, the population of M2 macrophages increased markedly both in vivo and in cell culture, with enhanced phagocytosis via the cAMP/PKA/RAC1 pathway in response to mechanical force in combination with BG particles. By contrast, M1 macrophage populations were decreased under the same circumstances. In addition, M2 macrophage polarization was also indicated by elevated IL-4 levels, reduced IL-1β levels, and less active MMP-9 in cell culture. Conclusion: This study explored the mechanisms of mechanical force-induced alveolar bone remodeling with bovine bone mineral grafts during OTM. The results might provide molecular insights into the related clinical problems of whether we can move teeth into the grafted materials; and how these materials become biologically remodeled and degraded under mechanical force.

Background: Assessment of growth-related or treatment-related changes in the maxilla requires a reliable method of superimposition. Such methods are well established for two-dimensional (2D) cephalometric images but not yet for three-dimensions (3D). The aims of this study were to identify natural reference structures (NRS) for the maxilla in growing patients in 3D, opportunistically using orthodontic mini-screws as reference; and to test the applicability of the proposed NRS for maxillary superimposition by assessing the concordance of this approach with Björk’s ‘stable reference structures’ in lateral projection. Methods: The stability of the mini-screws was tested on longitudinal pairs of pre- and post-orthodontic cone-beam computed tomography (CBCT) images by measuring the distance changes between screws. After verifying the stability of the mini-screws, rigid registration was performed for aligning the stable mini-screws. Then, non-rigid registration was used to establish the dense voxel-correspondence among CBCT images and calculate the displacement of each voxel belonging to the maxilla relative to the mini-screws. The displacement vectors were transformed to a standardized maxillary template to categorize the stability of the internal structures statistically. Those voxels that displaced less relative to the mini-screws were considered as the natural reference structures (NRS) for the maxilla. Test samples included another dataset of longitudinal CBCT scans. They were used to evaluate the applicability of the proposed NRS for maxillary superimposition. We assessed whether aligning the maxilla with proposed NRS is in concordance with the maxillary internal reference structures superimposition in the traditional 2D lateral view as suggested by Björk. This was quantitively assessed by comparing the mean sagittal and vertical tooth movements for both superimposition methods. Results: The stability of the mini-screws was tested on 10 pairs of pre- and post-orthodontic cone-beam computed tomography (CBCT) images (T1: 12.9 ± 0.8 yrs, T2: 14.8 ± 0.7 yrs). Both the loaded and the unloaded mini-screws were shown to be stable during orthodontic treatment, which indicates that they can be used as reference points. By analyzing the deformation map of the maxilla, we confirmed that the infraorbital rims, maxilla around the piriform foramen, the infrazygomatic crest and the hard palate (palatal vault more than 1 cm distal to incisor foramen except the palatal suture) were stable during growth. Another dataset of longitudinal CBCT scans (T1: 12.2 ± 0.63 yrs, T2: 15.2 ± 0.96 yrs) was used to assess the concordance of this approach with Björk’s ‘stable reference structures’. The movement of the maxillary first molar and central incisor showed no statistically significant difference when superimposing the test images with the proposed NRS or with the classic Björk maxillary superimposition in the lateral view. Conclusions: The infraorbital rims, maxilla around the piriform foramen, the infrazygomatic crest and the hard palate (palatal vault more than 1 cm posterior to incisal foramen except the palatal suture) were identified as stable regions in the maxilla. These stable structures can be used for maxillary superimposition in 3D and generate comparable results to Björk superimposition in the lateral view.

Segmentation of the masseter muscle (MM) on cone-beam computed tomography (CBCT) is challenging due to the lack of sufficient soft-tissue contrast. Moreover, manual segmentation is laborious and time-consuming. The purpose of this study was to propose a deep learning-based automatic approach to accurately segment the MM from CBCT under the refinement of high-quality paired computed tomography (CT). Fifty independent CBCT and 42 clinically hard-to-obtain paired CBCT and CT were manually annotated by two observers. A 3D U-shape network was carefully designed to segment the MM effectively. Manual annotations on CT were set as the ground truth. Additionally, an extra five CT and five CBCT auto-segmentation results were revised by one oral and maxillofacial anatomy expert to evaluate their clinical suitability. CBCT auto-segmentation results were comparable to the CT counterparts and significantly improved the similarity with the ground truth compared with manual annotations on CBCT. The automatic approach was more than 332 times shorter than that of a human operation. Only 0.52% of the manual revision fraction was required. This automatic model could simultaneously and accurately segment the MM structures on CBCT and CT, which can improve clinical efficiency and efficacy, and provide critical information for personalized treatment and long-term follow-up.