The use of sel-ligating appliance can reduce inflammatory response to orthodontic force and keep periodontal health in orthodontic treatment.

OBJECTIVE: Orthodontics, as a common way of orthodontic treatment, is usually to maintain oral health and protect periodontal tissue. The self-ligating appliance technique, since its advent in the 1930s, have been rather popular ammong the majority of orthodontists. This study was to determine that self-ligating appliance can reduce inflammation in gingival crevicular fluid (GCF) of patients receiving orthodontic treatment and keep periodontal health. METHODS: The clinical data of 97 orthodontic patients admitted to the Department of Stomatology of Fujian Provincial Hospital, Fujian Provincial Clinical College of Fujian Medical University from March 2019 to March 2020 were analyzed retrospectively. Among them, 42 patients receiving orthodontic treatment with traditional MBT straight-wire appliance (SWA) were included in the control group (CG) and 55 patients treated with self-ligating appliance were collected as the observation group (OG). The two cohorts were compared with respect to the following aspects: curative effect, pain degree on the 1st, 2nd, 3rd, 5th and 7th day after wearing the appliance, oral related quality of life (QoL) before and after orthodontic treatment, satisfaction with the orthodontic treatment, periodontal condition, and GCF and inflammatory factor contents before, 3 months and 6 months after orthodontic treatment. RESULTS: OG had significantly higher therapeutic efficacy of orthodontic treatment than CG (P<0.05). At the initial stage of treatment, the pain degree in OG was obviously lower than that in CG (P<0.05). Compared with CG, the plaque index (PLI), sulcus bleeding index (SBI), gingival recession (GR), periodontal probing depth (PPD) and clinical attachment loss (CAL) were better in OG after orthodontic treatment, and the differences were statistically significant (P<0.05). The contents of GCF, prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α) and interleukin-1ß (IL-1ß) in OG were lower than those in CG after orthodontic treatment, with significant differences between the two groups (P<0.05). Oral related QoL and orthodontic satisfaction were higher in OG, and the differences were statistically significant (P<0.05). CONCLUSIONS: Compared with traditional SWA, the self-ligating appliance in orthodontic treatment contributes to higher efficacy and satisfaction, less local inflammatory reaction, and significantly improved periodontal condition and oral health of patients.

[Three-dimensional finite element analysis on the effect of posterior cross-bite of individual teeth on temporomandibular joint].

OBJECTIVE: To analyze the stress distribution of temporomandibular joint (TMJ) in posterior cross-bite of individual teeth and in normal occlusion during the intercuspal occlusion (ICO). METHODS: On the basis of the geometric TMJ model of normal occlusion, the TMJ finite element model of posterior cross-bite of individual teeth was reconstructed. The occlusal force and boundary conditions were applied on the model. Using three-dimensional finite element method (FEM), the stress distribution of TMJ in posterior cross-bite of individual teeth was analyzed by simulating the ICO load. RESULTS: No significant differences were found in stress distribution in various TMJ structures between posterior cross-bite of individual teeth and normal occlusion. However, the stress level was higher and the stress distribution was more inhomogeneous in posterior cross-bite of individual teeth than in normal occlusion. In the cross-bite malocclusion of individual posterior teeth, the maximum of von Mises stress was 0.792 MPa, the maximum principal stress was 0.598 MPa and the minimum principal stress was -0.744 MPa. But in normal occlusion, the maximum of von Mises stress was 0.592 MPa, the maximum principal stress was 0.395 MPa and the minimum principal stress was -0.554 MPa. CONCLUSIONS: When the ICO load was applied, the stress distribution of TMJ was more inhomogeneous and the stress level was higher in posterior cross-bite of individual teeth than in normal occlusion.

[Three-dimensional reconstruction of temporomandibular joint with CT and MRI medical image fusion technology].

OBJECTIVE: To investigate the method of the three-dimensional reconstruction of temporomandibular joint (TMJ) on the basis of CT and MRI medical image fusion technology, which establishes good foundation for a series biomechanical studies and clinical analysis. METHODS: The geometric data for the TMJ model were obtained from a young and healthy male volunteer. Twelve spherical markers were located on the regions of both TMJ and mental tubercles, where CT and MRI scans can reach. The three-dimensional geometric of the hard and soft tissues of TMJ was reconstructed by CT and MRI scans data, which was based on the registration procedures of spherical markers located on the face of the volunteer. RESULTS: The three-dimensional geometric model of TMJ was obtained, including hibateral articular disc, mandible, glenoid fossa and inferior teeth, and it had better geometric similarity. The results showed that the methods of three-dimensional reconstruction of TMJ with CT and MRI medical image fusion technology can be operated easily and promptly. The constructed model had good morphology. CONCLUSION: It is feasible to construct the three-dimensional model of TMJ on the basis of the registration procedures of spherical markers and CT-MRI medical image fusion technology. It has the advantage of simulating both hard and soft tissues reasonably. The model well expresses the shape of the TMJ.