61

Relatively often denture sore spots caused by a lingual bar are seen on the alveolar wall. One assumes this to be the result of poor workmanship and speculates on the ideal distance which should be maintained between  alveolar wall and the lingual bar.

A few comments on the subject: The sore spots never occur immediately after delivering the partial denture, but rather, at a much later date – 6 months, a year, or even later (Fig. 61). In addition, they occur much more frequently in cases where the remaining anterior dentition is smaller. One can explain this as follows:

62

When a free-end saddle is subjected to occlusal forces the denture rotates around an axis which runs from the dental rest on the same side to the end of the base on the opposite side. However, it does not suffice to consider only this aspect. One must attempt to picture the situation in three dimensions.

The closer the axis, specifically the dental rest, lies to the alveolar process, the more favorable the situation. This is due to the fact that the resulting movement along a circular path, executed by the lingual bar upon functional loading of the saddle, is determined by the  radius rest/bar with the dental rest as center of the circle (Fig. 62 + 64).

In general, no contact between lingual bar and alveolar process occurs because the circular movement of the bar follows more nearly a tangential path to the surface of the arch. Long teeth and vertical or even undercut alveolar walls are negative factors.

63

As previously mentioned, the movement of the lingual bar is less damaging when only a single saddle is subjected to a functional load. However, once a certain amount of resorption has taken place on both sides of the arch, the denture will rotate when the teeth are closed together around the transverse axis formed by connecting the most distal rests on each side of the arch.

64

This clenching motion will result in the lingual bar being moved directly toward the alveolar wall (Fig. 63 + 64).