Determining articulation parameters using the Avantis 3D software, considering the individual hinge axis position

BACKGROUND: Axiography (condylography) is used to assess the temporomandibular joints (TMJ) function and obtain individual articulator settings. Creating a virtual patient with TMJ dysfunction and determining its individual articulation parameters considerably simplify the procedure and accelerate the diagnosis for further rehabilitation.

AIM: To assess the potential of a virtual articulation system using the Avantis 3D software for determining angular parameters of mandibular movement, considering the individual hinge axis position.

MATERIALS AND METHODS: The clinical phase of the study included 25 volunteers aged 18–30 years, without complaints of TMJ dysfunction, previous orthodontic treatment, and malocclusion.

All volunteers underwent electronic condylography (axiography) using the CADIAX Diagnostic device; the movement of mandible heads during protrusion and mediotrusion was analyzed. The individual values of sagittal condylar inclination (SCI) and Bennett angle on the left and right were obtained. The individual hinge axis was determined, and special radiopaque markers were placed on the skin in the projection of its rotation. Additional markers were placed on the lower edge of the left orbital cavity.

Using these markers, cone beam computed tomography (CBCT) was performed in all volunteers, with a 17.5×20.0 matrix size, to create a 3D project, compare CBCT findings with virtual dental models, and generate a reference plane.

Virtual occlusion measurements were obtained in terminal positions (protrusion and laterotrusion) using the Trios 3 Basic Pod intraoral scanner. The Avantis 3D software was then used to create 3D scenes based on the obtained measurements and CBCT of the skull. The mean length of each path registered for virtual articulator settings in the Avantis 3D software was approximately 3 mm. The interarticular distance used for the analysis was recalculated using the Avantis 3D software to be equal to the standard intercondylar distance of the articulator, which is 110 mm. Individual SCI and Bennett angle values were obtained for all study subjects.

The experimental phase involved phantom models installed in a fully adjustable articulator Reference SL. CBCT was performed with an installed articulator and a maxillary cast, in a zero position, with closed center locks, which was matched to the maxilla present in the CT scan, and a 3D scene was created to measure SCI and Bennett angle values. After detecting the articulator’s hinge axis, electronic measurements of movement were taken, with a predefined SCI of 20–60° (increment 5°) and Bennett angle increments of 6, 12, and 20°. The results were assessed for a path of 3 mm.

RESULTS: The mean difference between the compared determination methods of angular parameters obtained during the experimental phase of the study was 3.20±7.22° for the left SCI; 2.09±9.75° for the right SCI; 5.50±11.26° for the left Bennett angle, and 6.40±6.29° for the right Bennett angle.

The mean difference between the compared determination methods of angular parameters obtained during the clinical phase of the study was 11.80±6.86° for the left SCI; 12.10±6.08° for the right SCI; 13.0±9.89° for the left Bennett angle, and 10.70±11.48° for the right Bennett angle.

CONCLUSION: Both approaches for determining angular parameters can be recommended for use in real-world dental practice. When sophisticated, expensive equipment is not available, a virtual articulation system in the Avantis 3D software can be used as a more simple and affordable technique of measuring angular parameters.