A Brief Discussion of The Growth of the Human Face
While we know that the proliferation of cells is the cause of the forward movement of the hard and soft tissues of the hard and soft profiles, we will never be able to determine exactly where this cell activity is located in a given case. Since this is true, we must rely on millimeter measurement from the base (the great divide) to the periphery (the profile) to analyze the complexities of the growth in the horizontal dimension. It is not necessary to know exactly how much the zygomatic suture (for instance) moves forward from the great divide, or exactly how much the nose moves forward from the zygomatic suture. The overall measurement from the great divide to the profile is sufficient for the clinical orthodontist to correctly analyze growth and treatment results.
There have been different theories in the past, concerning the specific location of cell activity, which contributes to the forward displacement of the hard and soft tissue profiles. It has never been determined whether the nose is pushed or pulled forward.
Scott, in a discussion of facial growth and growth of the nasal cavities, at the Queen's University, Belfast, Ireland, has contributed a great deal of information concerning the forward growth of the face and nose. He states, "In the growth of the upper face, however, no satisfactory mechanism has been postulated to account for the separation of the bones of the sutures." He further states that, "It would appear more probable that separation of the adjacent bones must take place at the sutures before bone growth can take place and that this separation must be brought about by the growth of some organ like the brain or the eyeball or tissue like cartilage."
Scott also states, "Space must be made for these teeth (upper 2nd and 3rd molars) by forward migration of all erupted teeth through the alveolar bone, and the alveolar process must be enlarged by growth of the front of the face." This could be taken to mean that this growth of the septal cartilage tends to produce its own forward movement and possibly pull other structures with it. Thus, it is evident that we have much to learn about the growth of the human face.
In the vertical dimension, the total distance from the base (sella horizontal) to the periphery (the mandibular plane) is divided by a movable part-the lower jaw. This divides the total distance into separate parts, the upper and lower jaws, and simplifies measurement. This makes it possible to more accurately locate the increments of growth which cause the overall increase of the vertical dimension.
While it is not always possible to exactly locate the area of change which causes the downward movement of the palatal plane, we can exactly measure the downward movement of the upper molars. Also we can exactly measure the upward growth of the lower molars.
Thus, the vertical growth of the segments of the vertical dimension of the face can be more accurately measured than the segments of horizontal growth.
In spite of all of the uncertainties of the exact amounts of growth in the exact locations, fortunately we can exactly measure the overall vertical and horizontal growth. This is sufficient for the clinical orthodontist to accurately analyze treatment results. After all, this was the final reason for cephalometric studies from the beginning.
Bibliography
1. Scott, G.H., The Cartilage of the Nasel Septiem, British Dental Journel, July 1953
2. Scott, G.H., Analysis of Facial Growth: The Anterior an Vertical Dimensions. From the Anatomy Department, Queen University.
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