Vertical motions of bottom jaw

There is opening and closing of mouth at vertical motions of bottom jaw, due to reduction of muscles, lift and drop a bottom jaw. Lowering of bottom jaw takes place at active reduction of jaw-subglossal, mentihyoid and front belly of biventer muscles, on condition of fixing of hyoid a musculature, that lies below her. At closing of mouth getting up of bottom jaw comes true by reduction temporal, actually chewing and medial pterygoid muscle, at the gradual weakening of muscles, drop a bottom jaw.

During opening of mouth simultaneously with the rotation of bottom jaw about axis, passing through the heads of bottom jaw in transversal direction, head of bottom jaw slide on the slope of arthral tubercle downward and forward. At the maximal opening of mouth of head set in cutting edge of arthral tubercle, thus different motions register in the different departments of joint. In an overhead department there is skidding of fibroplate together with the head of bottom jaw downward and forward. In the bottom department of joint a head is revolved in deepening of bottom surface of disk, that for her is a movable arthral fossula. At opening of mouth a to 1-1,5 cm take place only rotatory motions in the bottom department of joint. Distance between overhead and bottom chisels for the grown man at the maximal opening of mouth 4,5 is equal on the average.

At opening of mouth every tooth of bottom jaw goes down downward and, displaced back, describes a concentric curve with a general center in an arthral head. As a bottom jaw at opening of mouth goes down downward and displaced back, curves will move in space, the axis of rotation of head of bottom jaw will move simultaneously. If to divide the way passed by the head of bottom jaw, on the slope of arthral tubercle (arthral way), on separate segments, then each the curve will correspond to the segment. Thus, all way passed by some point which is situated, for example, on a chin performance, is a not correct curve, and polyline consisting of great number of curves.

Tried Гизе to define the center of rotation of bottom jaw at her vertical motion. In the different phases of her motion the center of rotation moves back.

Sagittal of motion of bottom jaw

At sagittal motions a bottom jaw moves to and fro. A forward movement comes true by bilateral reduction of the lateral pterygoid muscles fastened from one side in the fossulas of pterygoid sprouts, from other - on the front surface of head of bottom jaw, fibroplate. Motion at the front back takes place because of reduction of muscles, drop a jaw and back bunches of temporal muscles. As a result of this work of muscles, an arthral head carries out a reverse way from position of front occlusion in a state of central occlusion. Motion at the front back yet sometimes possible at motion of arthral head from the state of central occlusion back (back occlusion). This motion takes place also as a result of traction of muscles that drop a bottom jaw and horizontal bunches of temporal muscle. He is insignificant enough, maybe within the limits of a 1-2 mm and observed mainly for elderly people because of Spain of joint. In area of teeth this motion takes place as follows: bottom teeth slide after the palatal surfaces of overhead foreteeth upwards and back, and pass, thus, in initial position.

The forward movement of bottom jaw can be divided into two phases. In the first phase a fibroplate together with the head of bottom jaw slides on the surface of arthral tubercle. In the second phase, skidding of head is joined by joint motion her about own transverse axis passing through head. These motions take place simultaneously on the right and on the left. Distance which can pass head forward and downward after an arthral tubercle, 0,75 - 1см is equal. At mastication this distance makes 2-3см. A sagital arthral way is name distance which passes head of bottom jaw at the forward movement of bottom jaw.

Sagittal an arthral way is characterized by the corner of sagittal of arthral way. This corner appears at crossing of line, sagittal continues an arthral way, and prosthetic planes (occlusal). In a prosthetic plane it is necessary to understand plane passing through edges first chisels of bottom jaw and distal cheek hillocks of wisdom teeth, and at their absence - through similar hillocks the second molar. The corner of sagittal of arthral way, from data Giza, on the average is equal to 33 degrees. The sizes of this corner are individual in actual fact, because a corner is determined by inclination and degree of development of arthral tubercle, in addition, his age-related changeability takes place.

At motion of bottom jaw in a orthognathic bite foreteeth can go out forward only subject to condition, if they will rid of ceiling their overhead teeth. This motion is accompanied by skidding of bottom chisels on a palatal surface overhead to the moment of collision of cutting edges (front occlusion). Way,, about passing bottom chisels at advancement of bottom jaw forward, sagittal is named by a chisel way. At crossing of line of sagittal of chisel way a corner which is named the corner of sagittal of chisel way appears from a prosthetic plane. The size of him is individual and depends on character of ceiling, on Гизе, he is equal on the average 40 - 50 degrees(At a opistognatichesky bite he approaches 90 degrees, at a biprognaticheskom bite to 0 degrees, is absent in a direct bite).