Introduction: Clear aligner therapy has become increasingly popular in recent years, although it has encountered several difficulties in premolar extraction treatment. These difficulties include anterior dentition, lingual tipping and extrusion. The design of the present clinical scheme usually set a tiny space between the anterior teeth before retraction in order to obtain an ideal outcome. The objective of our research was to analyze the effect of the existing spaces during retraction. Methods: Models including maxillary dentition without first premolars, maxilla, periodontal ligaments, gingiva, or aligners were constructed and imported to an ANSYS workbench. Five groups of models were created: without spaces and with 0.25, 0.50, 0.75 and 1.00 mm spaces between the anterior dentition. A 0.20 mm retraction step was applied to all the groups. Results: As the spaces between the anterior dentition increased, the bowing effect of the aligner caused by the passive forces decreased gradually. Accordingly, the degree of extrusion of the anterior dentition was alleviated significantly, while sagittal movement was reduced. However, the overall movement tended to be a bodily displacement rather than tipping. Meanwhile, maximum Von Mises stress of the periodontal ligaments (PDLs) was markedly decreased. Conclusion: These analyses indicate that spaces between the anterior dentition during anterior retraction are beneficial for decreasing the tendency for extrusion of the anterior dentition and require provision of anchorage. Appropriate spaces can be designed to lest the lingual tipping and extrusion effect of the anterior teeth while simultaneously reducing the maximum stresses on PDLs.

Circulating and tissue-resident extracellular vesicles (EVs) represent promising targets as novel theranostic biomarkers, and they emerge as important players in the maintenance of organismal homeostasis and the progression of a wide spectrum of diseases. While the current research focuses on the characterization of endogenous exosomes with the endosomal origin, microvesicles blebbing from the plasma membrane have gained increasing attention in health and sickness, which are featured by an abundance of surface molecules recapitulating the membrane signature of parent cells. Here, a reproducible procedure is presented based on differential centrifugation for extracting and characterizing EVs from the plasma and solid tissues, such as the bone. The protocol further describes subsequent profiling of surface antigens and protein cargos of EVs, which are thus traceable for their derivations and identified with components related to potential function. This method will be useful for correlative, functional, and mechanistic analysis of EVs in biological, physiological, and pathological studies.

To improve the success rate of mini-implants, some surgical guides have been developed through digital technologies to achieve three-dimensional (3D) guided mini-implants insertion. However, there is no a surgical guide which can be applied for the insertion of infrazygomatic mini-implant. In this study, we introduced a two-trajectories surgical guide and investigated the success rate of infrazygomatic mini-implants under the guidance of the template. An individualized surgical guide was fabricated based on the cone-beam computed tomography images, digital intraoral scanning images and the predesigned insertion plans. In the surgical guide group, 62 mini-implants were inserted between the maxillary first and second molars under the guidance of surgical guides (n = 62). In the historical control group, 54 mini-implants were placed by the direct manual method at the same site (n = 54). Then the mini-implant success rate in these two groups was compared. After implantation, 2 out of the 62 mini-implants fell off and a success rate of 96.8% was indicated in the surgical guide group. In the historical control group, 11 of 54 mini-implants fell off and the success rate was 79.6%. There was statistically significant difference between the success rate of two groups (P = 0.003). The two-trajectories surgical guide is advantageous for the insertion of infrazygomatic mini-implant. Both the success rate and stability of infrazygomatic mini-implant were improved significantly with the use of the guide. But further studies with enlarged sample are needed to evaluate the accuracy and stability of the mini-implant placement.

Background: The purpose of this study was to obtain measurements of the anatomical structures of the mandibular buccal shelf (MBS) using cone-beam computed tomography (CBCT) for the safe insertion of orthodontic mini-implants. Methods: The sample consisted of the CBCT records of 100 subjects. The scans were imported into a reconstruction program. Measurements were taken in the coronal plane for three different roots: the mandibular first molar distal root (6D), second molar mesial root (7 M), and second molar distal root (7D). The inferior alveolar nerve canal (IANC) was used as a reference to determine the safe insertion depth. The roots of the mandibular molars were used as a reference to determine the maximum safe insertion angle. Analysis of variance with post hoc analysis and Kruskal-Wallis H test with post hoc analysis were used for data analysis. Results: For the 6Ds, the average bone depth was 20.33 ± 3.6 mm, the average depth above the IANC plane was 9.55 ± 2.97 mm, and the average maximum safe insertion angle was 47.47 ± 18.94°. For the 7Ms, the average bone depth was 22.06 ± 2.85 mm, the average depth above the IANC plane was 10.71 ± 2.67 mm, and the average maximum safe insertion angle was 43.14 ± 15.26°. For the 7Ds, the average bone depth was 23.75 ± 2.86 mm, the average depth above the IANC plane was 12.12 ± 2.61 mm, and the average maximum safe insertion angle was 28.39 ± 10.96°. From anterior to posterior, the buccal bone depth and depth above the IANC gradually increased (P < 0.01), there was no significant difference in the maximum safe insertion angle between the 6Ds and 7Ms (P = 1.000), but the significant difference was observed between 6Ds and 7Ds, 7Ms and 7Ds (P < 0.000). Conclusions: The optimal implantation site for mini-implant in the MBS is at the buccal site corresponding to the second molar. A maximum insertion length of ≤ 12 mm and a maximum insertion angle which respects the long axial of the tooth root of ≤ 28° are recommended for the safe insertion of mini-implants in the MBS.

Undergraduate orthodontic education requires students to integrate multiple diagnostic sources and develop individualized treatment plans, yet lecture-based learning may limit opportunities for integrating theoretical knowledge with clinical practice. This study evaluated the effectiveness of a case review-based clinical learning improving academic performance and learning-related outcomes. Forty-two undergraduate orthodontic students were randomly assigned to either a case review-based learning group (experimental, n = 21) or a lecture-based learning group (control, n = 21). The experimental group engaged with complete patient cases in a stepwise, longitudinal format, linking each stage from consultation and record-taking to appliance therapy and retention with underlying theoretical knowledge. The same group of instructors delivered both teaching interventions using an identical curriculum and teaching schedule. Academic performance was assessed via orthodontic examination scores. Additional outcomes included self-reported learning interest and self-directed learning ability. Students in the experimental group achieved significantly higher orthodontic examination scores than those in the control group (95.2 ± 1.7 vs. 66.2 ± 3.5, p < 0.001). The experimental group also reported significantly higher ratings for the appropriateness of course design (9.71 ± 1.27 vs. 7.29 ± 1.31, p < 0.001) and overall satisfaction (9.05 ± 0.80 vs. 6.76 ± 1.18, p < 0.001). In addition, 9 of 10 instructor members (90%) expressed willingness to adopt the structured case-based learning approach in future skills teaching, compared with 1 of 10 (10%) for the lecture-based learning. The case-based learning was associated with improved academic performance, learning interest, and self-directed learning among undergraduate orthodontic students. Integrating complete clinical cases in a stepwise, longitudinal manner may provide a useful pedagogical approach for bridging theoretical knowledge with clinical practice in orthodontic education.