Transversal of motion of bottom jaw

At transversal motions of bottom jaw there are motions in a temporomandibular joint and in area of teeth, but different on different parties jaws. A side which contracting muscle is on is named balancing, an opposite side is named - by a worker. On a working side teeth are set against each other by of the same name hillocks, and on balancing - dissimilar, cheek bottom knolls are set against the palatal tubercles of overhead teeth. On a working side the function of mastication comes true.

Transversal motion takes place because of reduction external covered visible muscles on a balancing side. So, at motion of jaw to the right left lateral grows short wing visible muscle, at motion to the left - right. At this motion the arthral head of bottom jaw pivots on one side, going almost apeak through industry of bottom jaw. At the same time the arthral head of bottom jaw of other side together with a disk slides on the surface of arthral tubercle. If a bottom jaw moves, for example, to the right, then on left the head of her is displaced downward and forward, and on a right side an arthral head is revolved about vertical axis.

As a result of complex action of musculature both heads can simultaneously come to the fore or back, but never is so that one was advanced, and position remained other to unchanging in an arthral fossula. Therefore a mental center round which a head moves on a balancing side in actual fact is not in a head on a working side, and always is between two heads or outside heads, i.e. there is a functional but not anatomic center of rotation.

On the side of muscle, grew short, the head of bottom jaw was displaced downward, forward and a bit inward. At moving of arthral head inward direction of new way of head is formed with direction of sagittal way by the corner of Bennett, equal on the average 15 - 17 degrees. On an opposite side the head of bottom jaw is displaced outside, appearing, thus, under a corner to ​​primary position.

At transversal motions there are also changes in mutual relations between dental rows. Transversal of motion is characterized by the certain changes of occlusal contacts of teeth. As a bottom jaw is displaced both to the right or to the left, teeth describe curves intersecting under an obtuse angle. What farther from the head of bottom jaw a tooth is located, the anymore there will be a corner. The most obtuse angle appears at crossing of the curves formed by moving of central chisels. The imaginary corner formed at moving of central chisels is named a gothic corner, or corner of transversal chisel to the way.

At the same time because of moving of bottom jaw towards working side, there are changes in the mutual relations of masticatory teeth. There is closing of dissimilar hillocks on a balancing side, and on a working side is closing of the same name hillocks.

To According to And. I. Katz of closing of hillocks takes place on a working side, thus only between a cheek hillocks. In respect of other hillocks, then the cheek hillocks of bottom teeth are set on a balancing side against the palatal hillocks of overhead teeth, not closing up, and on a working side cheek hillocks close up only, between heathen hillocks, closing is not observed. To our opinion on a balancing side maybe both formation of contact between dissimilar hillocks and their absence, that depends on expressed of transversal occlusal of curves, age, effaced of hillocks, character of masticatory motions.

The excursions of bottom jaw are very difficult, as are combination of different motions. Masticatory motions have most practical interest for orthopaedic stomatology. Their knowledge can facilitate making of orthopaedic constructions.

Phases of masticatory cycle on Гизе. The recurrence of motions of bottom jaw presents Giza as a chart. The initial moment of motion is position of central occlusion. Then continuously four phases follow one by one. In the first phase a jaw goes down and comes to the fore. In the second phase there is displacement of jaw aside (transversal motion). In the third phase teeth close up on the working side of the same name hillocks, and on balancing - dissimilar. In a fourth phase teeth go back into position of central occlusion and masticatory cycle recurs. After completion of mastication a jaw is set in position of relative physiological rest.