The work of Dr. Beni Solow has shown that the axis of the mandibular ramus remains relatively parallel throughout the growing period. Instances can be found where there have been minor changes in the inclination of this axis, but in general we find that it remains parallel to its original inclination.

The gonion angle reduction, due to growth, can vary up to as much as 14° (please see Fig. 5 in Article 1 of the Schudy Chronicles). This of course will change the axis 14° as related to the mandible. However, this reduction of the gonion angle will change the inclination of the ramus axis very little or none. Quite a puzzle, eh?

Let us use an example of a growth study in which the gonion angle reduced 10°, and see how this reduction changes the anatomy of the area. See Fig. 1.

Fig 1 This shows the growth of the mandible of a male from age 10 to age 16. It shows the growth of the corpus and the bending of the gonion angle. The central axis of the ramus is difficult to accurately locate, so we used the posterior outline of the ramus as the axis.

In 1972 Bjork reported that in low angle class II division II cases, when superimposing on the mandibular implants, there is in most cases considerable resorption at the lower border of the mandible near the gonion angle. This would produce an increase in the gonion angle. Yet, these are the types of cases where there is the most reduction of the gonion angle. This is still another puzzling conundrum!! It tells us that we have much to learn about the growth of the mandible.

If we remove the mandible from the glenoid fossa and measure it out of anatomical context, the condyle and the gonion angle are free to move. However, when we measure the mandible with the condyle in the fossa, only the gonion angle is free to move. Obviously when the gonion angle is reduced 10° it must move posteriorly. But where this occurs the ramus axis is affected little or none. Same puzzle!!?

It has been reported, by Fred Schudy in 1968 and Bjork in 1972, that the anteroposterior growth of the corpus causes a reduction of the gonion angle. Apparently this only happens when there is an excessive amount of corpus growth.

Then it seems logical that when the corpus grows excessively anteroposteriorly, that the gonion angle must bend forward to contain the large mandible. This appears to be one of Nature's compensations to harmonize the anatomical complex.

In conclusion, the author realizes that this discussion has not resolved any anatomical problems. It has only pointed out the complexity of the growth of the mandible. It is hoped that there is someone out there who can better explain this anatomical puzzle.

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