Functional states of mandibular movements and synovial pumps of the temporomandibular joint. Is it possible to provide a biomechanically correct replacement for the TMJ?

Due to its complexity, there is currently an incomplete understanding of temporomandibular joint (TMJ) function, especially in relation to the morphological interplay of the condyle and the disc as well as the disc, the Os temporale and the lateral pterygoid muscle. This also holds true for synovial flow and synovial pumps, the existence of which we postulate and for which we present a theory of their mechanism. In view of the complexity of mandibular movements and the morphology and function of the TMJ, we need to know how precisely a reconstruction of the TMJ, if necessary, must be adapted to nature. An analysis of the morphology of the functional states of the mandible, as well as the synovial pump system, should at least provide a basis for moulding reconstructions.

Biomechanics of the mandible and growth extension.

BACKGROUND AND OBJECTIVE: One way of determining the direction of growth of the mandible is to consider the temporomandibular joint and movement of the mandible as a four-joint gear system, regarding growth then as an extension of the gear system. Our aim was to examine any correlations between the type of biomechanical growth extension and change in the maxilomandibular relation after Class II therapy. SUBJECTS AND METHODS: A total of 130 lateral cephalograms-before and after orthodontic treatment-were available from 65 adolescent class II patients with open bite or deep bite. The two lateral cephalograms from each patient were superimposed on the occlusal plane. Cephalometric values and the vertical base point deviation were determined from biomechanical analyses, together with three distances and three angles. RESULTS: No correlation between the cephalometric data and distances or angles were observed. Although there were no significant differences in the distances, we did note significant differences in all three angles (p < 0.05). CONCLUSION: If gear system extension during growth is considered, this can be interpreted as meaning that the occlusal plane of those patients with an initially open bite dropped during treatment, but that it rose in patients with an initially deep bite.

Mandible, maxilla and cervical spine--a functional unit?

The motion patterns of mandibular points were recorded in vivo in closed, free movements of the mandible parallel to the sagittal-vertical plane. The points ran along loops which were valued by their area and length. All points whose loops included the same area under regarding the sense of circulation formed a straight line. Lines belonging to different areas were parallel. When the absolute areas of the oops were plotted for particular points a hollow depression with two minima resulted. The point that showed the lowest minimum in the depression corresponded to the position of the neuromuscular mandibular axis of rotation. The points running along equal loop lengths formed elliptical lines with a minimum below the condyle. The lines of constant loop area and loop length were overlaid with lateral radiographs, to match the patterns of motion with anatomical structures. The mandibular axis of rotation lay mostly cranial anterior of the condyle whereas the point with the shortest path lay mainly below this axis point, inside the bony structures. The row of teeth in the maxilla was found to be located below the line of minimal loop lengths. The cervical spine was arranged along the depression of the minimal absolute areas.

Functional improvement of the mandibular neuromuscular guidance by orthodontic-surgical treatment.

The primary aim of the study was to reveal whether adult patients with skeletal mandibular retrognathism combined with a dental Class II relationship without craniomandibular pain show a characteristic pattern of free mandibular movements compared to patients with a Class I skeletal and dental morphology. The secondary aim was to investigate whether these characteristic structures are subject to change following combined orthodontic-surgical treatment. Free mandibular movements were measured with an ultrasound device and analyzed with computer software developed by the authors. In all patients examined, 2 maxillarily and mandibularly fixed axes were found. These axes have no direct relation to the temporomandibular joints, are positioned above and anterior to the joints and maintain a constant distance. This gear system is referred to as a neuromuscularly determined dimeric link chain. The position of the mandible is defined by the rotational angle mu and the inclination angle alpha around the axes of the dimeric link chain. This dimeric link chain of free movements of patients with Class I skeletal and dental relationship functions according to the principle of least action: The angular velocities around the 2 axes show a constant ratio within the different segments of motion, and in the mu-alpha diagrams the segments of mandibular movements are represented by straight lines, the shortest paths between 2 positions. Individual cases and statistical data show that the structure of mandibular movements of patients with skeletal mandibular retrognathism combines with a dental Class II relationship without craniomadibular pain differs significantly from that of patients with Class I alignment. Mandibular retrognathism and a Class II relationship are accompanied by marked coordination disturbances in the rotary movements around the maxillary and mandibular neuromuscular axes. Following orthodontic-surgical treatment to restore ideal alignment of the occlusal, articular, and skeletal structures, the patients showed a similar pattern in the structure of mandibular movements to that of patients with Class I sketal and dental relationships. Thus, combined orthodontic-surgical treatment leads to measurable functional hamonization not only of the skeletal and dental structures but also of the neuromuscular guidance system.