Articulator
Articulators are devices used to simulate the movement of the TMJ . For this purpose, plaster models of the dental arches of the upper and lower jaw are mounted in occlusion in the articulator. The movement of the jaws to each other can then be simulated, which is essential for the production of dentures , partial and full dentures or splints .
Preliminary stages
The fixator and the occludator are preliminary stages of the articulator . The fixator only fixes the models in an unchangeable position to one another. It is used to view the models in the final bite position. The occludator also enables opening and closing movements (hinge movements) of the two models of the upper and lower jaw. This allows simple dental work to be performed or the models to be viewed in the context of orthodontic treatments.
Using the articulator
Depending on the setting options of the articulator, the chewing movements can be simulated more or less precisely. This enables the production of fixed dentures, such as crowns and bridges, removable dentures, such as partial or total dentures or bite splints.
Anatomical basics
The temporomandibular joint is the most versatile body joint, as it can perform both rotational movements (opening and closing movements around the joint axis) and sliding movements (advancing movements), with rotational movements also being possible during the advancing and sideways movements. The temporomandibular joints consist of a cartilage-covered joint head, a joint pit also covered with cartilage, the fiber-cartilaginous inter-joint disc, also known as the articular disc , which divides the joint into a lower and an upper chamber. It also consists of soft-tissue structures such as the ligamentous apparatus, vessels and nerves.
When the mouth is opened, the joint head slides forward and downward together with the disc, which is normally firmly connected to the joint head. The jaw joints and the masticatory muscles are active in all movements that the lower jaw performs. All of this should be imitated using an articulator.
Variants of the articulator
A distinction must be made between mean value articulators, partially adjustable articulators and full value articulators.
Average articulators
Average articulators do not offer any individual settings. After the models have been articulated , after they have been built into the articulator, they can only be moved according to mean values. They are predetermined according to the Bonwill triangle . The Bennett angle and the inclination of the condylar trajectory are predetermined according to statistical average values. The Bennett angle is the angle measured in the horizontal plane between the sagittal protrusion path and the mediotrusion path of the condyle . Its mean value is 15–20 °, that of the inclination of the condylar path is 30 °. Both are measured variables for jaw movements.
Partly adjustable articulators
With the partially adjustable articulators, one of the values, either the Bennett angle or the inclination of the condylar path, can be set individually.
Fully adjustable articulators
Fully adjustable articulators can be set according to individual patient measurements. For this purpose, special measurements on the patient are necessary for the joint-related articulation of the models. It is essential to determine the hinge axis, a connecting line between imaginary points of passage of the axis of rotation of the temporomandibular joint through the skin. The fully adjustable articulators are used to diagnose the position and movement of the opposing dental arches and to manufacture laboratory-made restorations from inlays to dentures . In both cases, the aim is to transfer the oral situation as naturally as possible.
The various models differ in the setting options, from individual adjustment of the Bennett angle, inclination of the joint path, terminal hinge axis, anterior tooth guidance. The anterior guide plate is exchangeable and thus the sliding angle can be individually adjusted. With the sideways movements of the lower jaw, the condyles are offset. A distinction is made between immediate side shift and progressive side shift .
After the upper jaw model has been articulated, the lower jaw model is mounted on the patient in accordance with the jaw relation determination (previously: bite registration).
Arcon articulators
Furthermore, a distinction is made between so-called non-arcon and arcon articulators. In the former, the structure of the device is the opposite of that of the human jaw (the condyles are mounted in the upper part of the articulator), in the latter the structure corresponds to the human anatomical features of the temporomandibular joint. However, this has no effect on the function, since the relative movement of the lower jaw to the upper jaw is the same for both technical approaches. With non-arcon articulators in the articulator joint, the sequence of movements is the opposite of the natural sequence and therefore needs getting used to.
Average value articulators are usually non-arcon devices with a condyle center distance of 10–11 centimeters (average usually 10.5 cm) and an insertable guide pin (incisal pointer) that indicates an incisal point at a distance of 10–11 centimeters from the condyle centers (see Bonwill triangle ). The chewing plane is aligned parallel to the table plane and to the upper edge of the articulator, which represents the Camper plane . The angle between the connecting line between the incisal reference point and the condylar centers on the one hand and the occlusal plane or Camper's plane on the other hand represents the Balkwill angle of 20 to 25 °. These angles are alternating angles and are therefore the same due to the parallelism of the occlusal plane and Camper's plane. When articulating, the model is aligned so that the incisal point is placed against the reference mandrel and the occlusal plane is horizontal (parallel to the table top) and the median plane of the model is perpendicular to the condylar connection line.
Individual evidence
- ↑ Charité, How does the temporomandibular joint work? ( Memento of the original from November 30, 2012 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. .
- ^ Dental prosthetics / Karlheinz Körber, 3rd edition, Thieme, 1985 Stuttgart: pp. 18, 24.
- ↑ B. Reitemeier, N. Schwenzer, M. Ehrenfeld, Introduction to Dentistry , Thieme Verlag, 2006, ISBN 3-13-139191-X .
- ↑ Terminology and nomenclature of the German Society for Functional Diagnostics and Therapy (DGFTD) and the German Society for Dental Prosthetics and Materials Science (DGzPW), V 2.0 of September 1, 2005, accessed on April 14, 2013.
- ↑ W.-D. Seeher, Worth knowing about the articulator (PDF; 276 kB) Bayerisches Zahnärztblatt, 10/2004, p. 32.
