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Abstract Background Studies focusing on accuracy of intraoral digital models in the palatal region are scarce. The present study aimed to investigate the influence of different scanning sequences on palatal trueness and to assess deviation and distribution character of trueness in palate. Methods Overall, 35 participants accepted three types of procedures to acquire upper digital models. Indirect models digitalised from plaster models were considered as the reference. Two direct digital models were acquired using TRIOS 3 POD intraoral scanners, namely Groups Tr1 and Tr2, wherein intraoral scanning differed in terms of palatal scanning sequences. Based on a modified dental-level superimposition method, 3D measurements of trueness in palate and palatal vault region (PVR) for palatal stable regional superimposition in Groups Tr1 and Tr2, respectively, were performed. Absolute deviations were measured for trueness, while signed deviations were analysed for shape distortion. Colour-coded maps were used for quantitative analysis of deviation distribution pattern. Paired t test was used to analyse differences in palatal trueness between different scanning sequences. One-way repeated-measures analysis of variance and Bonferroni test were used to compare trueness measurements among different superimposition methods. Intraclass correlation coefficient (ICC) was used to verify reproducibility of the proposed method. Results Palatal trueness in Group Tr1 (118.59 ± 37.67 μm) was slightly less accurate than that (108.25 ± 33.83 μm) in Group Tr2 (p = 0.012 0.90. Conclusions Scanning sequences can affect palatal trueness. Palatal scanning should be initiated at the palatal side of the posterior teeth where the initial scan begins. For 3D PVR superimposition, distal boundary of the selected region should be adjusted mesially whilst referring to intraoral digital models. Trial registration The trial has been registered (registration No: R000039467, Trial ID: UMIN000034617, date of registration: 2018/10/24‘retrospectively registered’).

Purpose: To apply geometric morphometrics and multivariate statistics to evaluate changes of the face for female Chinese patients who underwent orthodontic treatment with different type of anchorage control. Methods: Forty‐six adult female patients were enrolled including 33 four first premolar extraction cases (17 patients with mini‐implants for maximum anchorage control and 16 patients without mini‐implants) and 13 non‐extraction cases with minimum treatment duration of 15 months. Spatially dense correspondence was established among all the images The pre‐and post‐treatment average faces of the two extraction groups and the non‐extraction group were generated. Partial least squares regression was used to test the statistical significance of the effects of treatment for different anchorage choice. Results: The upper and lower lips were retruded significantly after treatment in the extraction groups. In the maximum anchorage control group, the temple and cheek were depressed by approximately 1 mm, and the zygomatic regions were increased in the mid‐face. However, these changes were not statistically significant. In comparison, no statistically significant facial changes occurred in the non‐extraction group. Conclusions: The anchorage choice and the removal of four first premolar extraction influence lip shape as well as the perioral regions. However, extraction treatment does not impact the appearance of the cheeks and temples on a statistically level, as compared to orthodontic treatment without premolar extractions. Spatially dense geometric morphometric facilitates comprehensive treatment effect quantification and visualization on the full facial changes for improving orthodontic outcome evaluation. [ABSTRACT FROM AUTHOR]

Objective: The objective of the study was to explore and validate the consensus of orthodontic experts on the assessment of orthodontic treatment outcomes based on subjective and objective analysis. Materials and Methods: The research consisted of two parts: the exploration and verification of expert consensus. First, a sample of 108 cases randomly selected from six dental schools in China were evaluated by 69 orthodontic experts and measured by researchers based on post‐treatment study casts and lateral cephalograms, respectively. Then, through statistical analysis, the objective indicators significantly correlated with experts' subjective evaluations were selected, their weights were determined, and the critical values of satisfactory, acceptable and unacceptable grades were screened. Subsequently, another sample of 72 cases were evaluated by another 36 orthodontic experts, and the subjective evaluation results were compared with the objective measurement results. Results: There were six model indicators and seven cephalometric indicators being significantly correlated with the experts' subjective evaluations, including occlusal contact, overjet, midline, interproximal contact, alignment, occlusal relationship, L1/NB, ANB, SN/OP, U1/SN, LL‐EP, Cm‐Sn‐UL and Ns‐Prn‐Pos, with a cumulative R2 of 0.704. In the verification part, the correlation coefficient between the 36 experts' subjective scores and objective regression scores was 0.716 (P <.001); the correlation coefficient between the 36 experts' subjective grades and objective grades was 0.757 (P <.001). Conclusions: Orthodontic experts had good consistency in the subjective evaluation of the combined records of post‐treatment study casts and lateral cephalograms. The objective indicators selected from subjective and objective analysis had good reliability and validity and could further improve the existing occlusal indices. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Objective Quantification and visualization of the location and magnitude of facial asymmetry is important for diagnosis and treatment planning. The objective of this study was to analyze the asymmetric features of the face for skeletal Class III patients using spatially-dense geometric morphometrics. Methods Three-dimensional facial images were obtained for 86 skeletal Class III patients. About 7160 uniformly sampled quasi-landmarks were automatically identified on each face using template mapping technique. The pointwise surface-to-surface distance between original and mirror face was measured and visualized for the whole face after robust Procrustes superimposition. The degree of overall asymmetry in an individual was scored using a root-mean-squared-error. Automatic partitioning of the face was obtained, and the severity of the asymmetry compared among seven facial regions. Results Facial asymmetry was mainly located on, but not limited to, the lower two-thirds of the face in skeletal Class III patients. The lower cheek and nose asymmetry were detected to have more extensive and of a greater magnitude of asymmetry than other facial anatomical regions but with various individual variations. The overall facial asymmetry index and the regional facial asymmetry indices were higher in males and patients with chin deviation. Conclusions Soft tissue asymmetry is predominately presented in the lower-third of the face in skeletal Class III patients and with various variations on other facial anatomical regions. Morphometric techniques and computer intensive analysis have allowed sophisticated quantification and visualization of the pointwise asymmetry on the full face. [ABSTRACT FROM AUTHOR]

Objective: To characterize ethnic differences between Chinese and White-Americans between 8.5 and 17.5 years of age, with respect to transverse cephalometric characteristics and to establish transverse craniofacial normative values for Chinese adolescents. Methods: Two-hundred fifty-seven and 547 posteroanterior cephalograms were selected from 35 White-Americans and 157 Chinese with individual normal occlusions. Transverse measurements were obtained and compared between ethnicities to guide determination of normative values for Chinese adolescents. Student's t-test or one-way analysis of variance was used, as appropriate. Results: Chinese girls demonstrated significantly larger measurements than White-American girls at all ages, with the exception of nasal width. Chinese boys exhibited larger measurements than White-American boys at different ages. Chinese boys had larger measurements than girls for most measurements. These data established normative values for Chinese adolescents. Discussion: Ethnic differences existed between Chinese and White-American adolescents with respect to transverse craniofacial measurements. Transverse normative values were established for Chinese adolescents. [ABSTRACT FROM AUTHOR]

Background Growth and development might lead to anchorage loss during orthodontic treatment, such as the mesial drift of molars, the compensation characteristics of upper molars following mandibular growth, or the angulation of molars before treatment. Different anchorage reinforcement devices have been developed to prevent mechanical anchorage loss, but the anchorage loss resulting from physiological factors should also be taken into account. Objective To explore the efficacy of a new strategy to control physiologic anchorage compared with that of the conventional straight-wire appliance. Trial design Randomized controlled trial (RCT). Methods Participants of Han ethnicity were randomized into the physiologic anchorage spee-wire system (PASS) group or McLaughlin–Bennett–Trevisi (MBT™) straight-wire group by minimization random allocation. The eligibility criteria were patients with a Class I or II molar relationship, permanent dentition (11–35 years old), fixed appliances involving the extraction of at least two upper first premolars, and medium or maximum anchorage requirements. Pre-treatment and post-treatment dental casts were scanned into digital casts and measured using a blinded method. Mesial displacements of the upper first molars were considered as the primary outcome for evaluating anchorage control. Measurements were taken for subgroups based on age. Results Data from 60 participants were analysed. The baseline characteristics were not significantly different between groups. Mesial displacement of the upper first molar (in mm) was 2.96 ± 1.52 in the PASS group and 2.70 ± 1.66 in the MBT group (P = 0.521). The variation in incisor torque was −6.94 ± 6.35 degree in the PASS group and −11.76 ± 7.65 degree in the MBT group (P = 0. 010). The incisor retraction (in mm) was 4.24 ± 1.99 and 5.67 ± 2.27 in the PASS and MBT groups, respectively (P = 0.012). Adverse effects were not documented in any patient. Limitation The study was a single-centre study. Conclusions Compared with the MBT group, the PASS group without additional anchorage devices could attain well anchorage control by considering the dentoalveolar compensation of anchor teeth. Registration This RCT was registered at the Chinese Clinical Trial Registry (Chictr.org.cn) ChiCTR-TRC-13003260. [ABSTRACT FROM AUTHOR]

Objective : To characterize ethnic differences between Chinese and White-Americans between 8.5 and 17.5 years of age, with respect to transverse cephalometric characteristics and to establish transverse craniofacial normative values for Chinese adolescents. Methods : Two-hundred fifty-seven and 547 posteroanterior cephalograms were selected from 35 White-Americans and 157 Chinese with individual normal occlusions. Transverse measurements were obtained and compared between ethnicities to guide determination of normative values for Chinese adolescents. Student's t -test or one-way analysis of variance was used, as appropriate. Results : Chinese girls demonstrated significantly larger measurements than White-American girls at all ages, with the exception of nasal width. Chinese boys exhibited larger measurements than White-American boys at different ages. Chinese boys had larger measurements than girls for most measurements. These data established normative values for Chinese adolescents. Discussion : Ethnic differences existed between Chinese and White-American adolescents with respect to transverse craniofacial measurements. Transverse normative values were established for Chinese adolescents.