The teaching of orthognathic surgery is difficult because it is complex and emphasizes the combination of theory and practice. The traditional teaching method focuses on theoretical teaching, but due to the limitation of conditions, it is difficult for students to master the operation. In this paper, we apply the digital three-dimensional surgical simulation system combined with 3D printing in specialist training of orthognathic surgery. Digital software and 3D printing are applied in the theoretical teaching, surgical operation, summary and reflection to combine practical teaching with theoretical teaching, so as to stimulate the subjective initiative of the students. The results showed that the teaching evaluation of the experimental group [(3.89±0.84) points] was better than that of the control group [(2.91±1.21) points]. The application of digital three-dimensional surgical simulation system combined with 3D printing has achieved satisfactory results.

For patients with dento-maxillofacial deformities who receive orthodontic-orthognathic combined treatment, the conventional treatment approach is preoperative orthodontic-orthognathic surgery-postoperative orthodontics. However, with the development of techniques used in orthodontic and orthognathic treatment, the surgery-first approach (SFA), namely, orthodontic surgery-postoperative orthodontics, has been widely used currently and displays several advantages, such as improving the treatment efficiency and providing patients with more satisfaction. This review provides a brief discussion and review of SFA concerning its development, indications, advantages and disadvantages, outcomes and stability, and the application and research progress of SFA in orthodontic-orthognathic combined treatment for patients with maxillofacial deformity. The literature review results showed that compared with the conventional treatment approach, SFA has relatively strict indications, which usually include patients with skeletal class Ⅱ/Ⅲ malocclusion, skeletal open bite, and bimaxillary protrusion or patients with facial asymmetry but who require little preoperative orthodontic treatment or removal of the compensation of the dental arch, specifically as follows: ①well-aligned to mildly crowded anterior teeth, ②flat to mild curve of Spee, ③normal to mildly proclined/retroclined incisor inclination, ④acceptable arch coordination, ⑤extensive occlusal contact between the upper and lower dentition requiring at least 3 occlusal contacts. Any occlusion that may affect the outcome of surgery or final result of the overall treatment, as well as any disease that may jeopardize the healing process after surgery, is regarded as a contraindication. Furthermore, SFA has potential disadvantages, such as a possible higher incidence of complications, including unstable occlusion and malunion of bones, which still require further research to be confirmed. Most researchers believe that no significant difference occurs between the outcome and stability of the two approaches. However, currently, we still need a sufficient sample size of prospective studies to provide accurate evidence.

Objective: To generate a new classification for adult temporomandibular joint ankylosis (TMJA), which could effectively guide treatment strategies for adult TMJA patients with various clinical features. Methods: We developed a new "CD" classification system according to the preservation of the condyle (C) and the severity of dentofacial bone deformity (D). From January 2016 to April 2020, 56 TMJ patients (with 73 ankylosed joints) in our department were classified into 4 subgroups by ‘CD’ classification: condylar head preservation but no dentofacial deformities (C+D-), no condylar head preservation and no dentofacial deformities (C-D-), condylar head preservation and dentofacial deformities (C+ D+), and no condylar head preservation but dentofacial deformities (C-D+). Different strategies were used according to the clinical features of each subgroup. The clinical outcomes of these patients were analyzed. Different treatment strategies of temporomandibular joint reconstruction were adopted for different subclasses of patients and were followed. "C +": lateral arthroplasty (LAP) was used to remove the rigidity and preserve the medial residual condyle. "C-": if the ankylosing bone ball is small and the loss of ascending branch height is not obvious, arthroplasty should be performed to relieve ankylosis; however, if the ankylosing bone ball is large and the ascending branch height decreases significantly, joint reconstruction should be carried out after the ankylosis is relieved. "D +": surgical treatment of secondary dental and maxillofacial malformations at the same time or over stages. "D-": orthodontic treatment after operation to improve occlusal relationship and symptomatic treatment of oral diseases. Results: After treatment, all 73 ankylosed joints were completely released, and the average maximal interincisal opening increased from (3.6±3.2 )to (32.8 ± 5.4) mm (P<0.001), with no recurrence of ankylosis found during the 12-48 month follow-up period. Conclusion The generation and elaboration of a ‘CD’ classification system is intended to help as a TMJA reconstruction guide for adult TMJA treatment and be widely used in more hospitals.

The anterior disc displacement (ADD) leads to temporomandibular joint osteoarthritis (TMJOA) and mandibular growth retardation in adolescents. To investigate the potential functional role of fibrocartilage stem cells (FCSCs) during the process, a surgical ADD-TMJOA mouse model was established. From 1 week after model generation, ADD mice exhibited aggravated mandibular growth retardation with osteoarthritis (OA)-like joint cartilage degeneration, manifesting with impaired chondrogenic differentiation and loss of subchondral bone homeostasis. Lineage tracing using Gli1-CreER⁺; Tm^fl/-mice and Sox9-CreER⁺;Tm^fl/-mice showed that ADD interfered with the chondrogenic capacity of Gli1⁺ FCSCs as well as osteogenic differentiation of Sox9⁺ lineage, mainly in the middle zone of TMJ cartilage. Then, a surgically induced disc reposition (DR) mouse model was generated. The inhibited FCSCs capacity was significantly alleviated by DR treatment in ADD mice. And both the ADD mice and adolescent ADD patients had significantly relieved OA phenotype and improved condylar growth after DR treatment. In conclusion, ADD-TMJOA leads to impaired chondrogenic progenitor capacity and osteogenesis differentiation of FCSCs lineage, resulting in cartilage degeneration and loss of subchondral bone homeostasis, finally causing TMJ growth retardation. DR at an early stage could significantly alleviate cartilage degeneration and restore TMJ cartilage growth potential.
Animals ; Mice ; Osteogenesis ; Zinc Finger Protein GLI1 ; Fibrocartilage ; Temporomandibular Joint ; Disease Models, Animal ; Osteoarthritis ; Stem Cells ; Growth Disorders