Improved anchoring nails: design and analysis of resistance ability : Tensile test and finite element analysis (FEA) of improved anchoring nails used in temporomandibular joint (TMJ) disc anchor

Evaluation of an improved anchoring nail in temporomandibular joint disc repositioning surgery: A prospective study of 25 patients

To confirm the effectiveness and stability of an improved anchoring nail through a prospective study using clinical evaluation and magnetic resonance imaging (MRI). Patients undergoing TMJ disc reduction and fixation were followed up for 1 year.Visual analog scale (VAS) pain scores and TMJ range of motion (maximum interincisal opening, protrusive excursion, lateral excursion) data were gathered pre- and postoperatively, and patient satisfaction was recorded. Four time points were investigated: before surgery (T0), 1 month post-surgery (T1), 6 months post-surgery (T2), and 1 year post-surgery (T3). Twenty-five patients (50 joints) participated in the study. The overall success rates of the improved and traditional anchoring nails were 88% and 92%, respectively. One year post-surgery, the patients' TMJ motion improved significantly (p < 0.001), and their pain was significantly alleviated (p < 0.001). Condyle height did not change significantly within 6 months (p = 0.801), but had increased by approximately 1.35 mm (p < 0.001) at 1 year post-surgery. The MRI scans also confirmed that new bone mass growth was present 1 year post-surgery. Compared with the traditional anchoring nail, the improved anchoring nail had a similar success rate and was associated with fewer foreign body sensations and less pain. Its clinical application should be further tested in studies with longer follow-up times and larger sample sizes.

Finite elements analysis of the temporomandibular joint disc in patients with intra-articular disorders

Background

Intra-articular disorders (ID) or anterior and/or medial displacement of the temporomandibular joint disorder (TMJ) disc are the most common form of TMJ dysfunction (TMD). TMD causes changes in the friction coefficient during TMJ movement. Herein, we provided a three-dimensional (3D) finite-elements model (FEM) including the maxilla, disc, and mandible and evaluated the stress distribution with different friction coefficient.

Methods

Fourteen volunteers without TMD and 20 patients with MRI-diagnosed TMD were selected. CT and MRI data were collected to build the 3D FEA model of the mandible and TMJ disc. Stress distribution with different friction coefficient was measured.

Result

In the normal model, stress distribution on the TMJ disc was 2.07 ± 0.17, 1.49 ± 0.14, and 1.41 ± 0.14 MPa with 0.001, 0.3, and 0.4 friction coefficient, respectively. In the TMD model, stress distribution was 3.87 ± 0.15, 7.23 ± 0.22, and 7.77 ± 0.19 MPa respectively.

Conclusion

When the friction coefficient of the side with anterior displacement increased, stress on the disc, condyle and mandible of the opposite side increased. Simultaneously, stress values of the disc, condyle and mandible were higher than those of the normal lateral joint.