In vivo three-dimensional mandibular kinematics and functional point trajectories during temporomandibular activities using 3d fluoroscopy

Prediction of condylar movement envelope surface based on facial morphology

The present study aimed to predict the envelope surfaces from facial morphology. Condylar envelope surfaces for 34 healthy adults were formed and simplified as sagittal section curves. Cephalometric and maximum mandibular moving distances measurement were performed on the participants. There was no statistically significant difference (p = 0.763) between the left and right maximum lateral movements. There was a statistically significant difference in the mandibular body length between the sexes. The envelope surfaces were divided into type 1 with H_p2 ≥ 1/3 H_p1 and type 2 with H_p2 < 1/3 × H_p1. SNA and SNB for type 2 were significantly greater than those for type 1 (p < 0.001). Therefore, the participants were divided into four groups based on gender and envelope surface morphology. The curves could be fitted using the second-order Fourier function (R-square ≥0.95). Six facial parameters were selected and a matrix was used to map facial morphology to the envelope surface. Individual sagittal curves were predicted using the matrix and facial parameters, and the envelope surface was predicted using the curve and the condyle model. Deviation analysis for the predicted envelope surface using the actual envelope as a reference was carried out (root mean square = 0.9970 mm ± 0.2918 mm). This method may lay a foundation for the geometric design of artificial fossa components of temporomandibular joint replacement systems. It may improve prosthesis design without flexible tissue repair and guide the movement of the artificial joint head.

Intraoral occlusal adjustment time and volume required for CAD/CAM crowns fabricated with different virtual mounting methods (A randomized crossover trial)

OBJECTIVE

To measure the required clinical time and volume of occlusal adjustment when the maxillary cast is positioned in a virtual articulator using one of three methods: digitization of a facebow-mounted mechanical articulator (group A), virtual Bonwill triangle (group B) or a 3D face scan (group F).

MATERIALS AND METHODS

In this randomized, triple-blind, crossover trial; 11 participants were enrolled. Every participant had one molar indicated for a single crown restoration. Three crowns were designed and milled for every participant molar totaling 33 crowns. Each of the three crowns was fabricated with the participant's casts virtually mounted utilizing a different method. An impression was taken of the crown in place before occlusal adjustment. The occlusal adjustment was then performed and timed with the three crowns in the different groups. After the occlusal adjustment, an impression of the adjusted crown was taken. The pre-adjustment and post-adjustment impressions were digitally superimposed and the volume difference was measured. The Kruskal-Wallis test was used to compare the groups.

RESULTS

Group A showed the shortest mean adjustment time (3:44.59 ± 3:39.07) followed by group F (4:30.09 ± 2:01.50) and group B (4:35.30 ± 2:32.33). The mean adjustment volume for group A was (28 ± 19.1 mm³) followed by group F (30.5 ± 18.8 mm³) and group B (40.6 ± 29.5 mm³). Different virtual mounting methods had no statistically significant effect on adjustment time (P-value = 0.538) or adjustment volume (P-value = 0.490).

CONCLUSIONS

A simplified approach in virtual articulator mounting appears to be justified in the construction of a single full-coverage prosthesis. Added labor, time and cost of more elaborate virtual mounting methods seem to be counterproductive.

Four-Dimensional Determination of the Patient-Specific Centre of Rotation for Total Temporomandibular Joint Replacements: Following the Groningen Principle

For patients who suffer from severe dysfunction of the temporomandibular joint (TMJ), a total joint replacement (TJR) in the form of a prosthesis may be indicated. The position of the centre of rotation in TJRs is crucial for good postoperative oral function; however, it is not determined patient-specifically (PS) in any current TMJ-TJR. The aim of this current study was to develop a 4D-workflow to ascertain the PS mean axis of rotation, or fixed hinge, that mimics the patient’s specific physiological mouth opening. Twenty healthy adult patients were asked to volunteer for a 4D-scanning procedure. From these 4D-scanning recordings of mouth opening exercises, patient-specific centres of rotation and axes of rotation were determined using our JawAnalyser tool. The mean CR location was positioned 28 [mm] inferiorly and 5.5 [mm] posteriorly to the centre of condyle (CoC). The 95% confidence interval ranged from 22.9 to 33.7 [mm] inferior and 3.1 to 7.8 [mm] posterior to the CoC. This study succeeded in developing an accurate 4D-workflow to determine a PS mean axis of rotation that mimics the patient’s specific physiological mouth opening. Furthermore, a change in concept is necessary for all commercially available TMJ-TJR prostheses in order to comply with the PS CRs calculated by our study. In the meantime, it seems wise to stick to placing the CR 15 [mm] inferiorly to the CoC, or even beyond, towards 28 [mm] if the patient’s anatomy allows this.

Efficacy of Kinematic Parameters for Assessment of Temporomandibular Joint Function and Disfunction: A Systematic Review and Meta-Analysis

The aim of this review was to answer the following PICO question: "Do TMJ kinematic parameters (intervention and comparison) show efficacy for assessment of mandibular function (Outcome) both in asymptomatic and TMD subjects? (Population)". PubMed, Scopus, Web of Science, Embase, Central databases were searched. The inclusion criteria were (1) performed on human, (2) English only, (3) on healthy, symptomatic or surgically altered TMJ, (4) measured dynamic kinematics of mandible or TMJ (5) with six degrees of freedom. To assess the Risk of Bias, the Joanna Briggs Institute tool for non-randomised clinical studies was employed. A pairwise meta-analysis was carried out using STATA v.17.0 (Stata). The heterogeneity was estimated using the Q value and the inconsistency index. Ninety-two articles were included in qualitative synthesis, nine studies in quantitative synthesis. The condylar inclination was significantly increased in female (effect size 0.03°, 95% CI: -0.06, 0.12, p = 0.00). Maximum mouth opening (MMO) was increased significantly in female population in comparison with males (effect size 0.65 millimetres (0.36, 1.66). Incisor displacement at MMO showed higher values for control groups compared with TMD subjects (overall effect size 0.16 millimetres (-0.37, 0.69). Evidence is still needed, considering the great variety of devices and parameters used for arthrokinematics. The present study suggests standardising outcomes, design, and population of the future studies in order to obtain more reliable and repeatable values.