It seems that many investigators concentrate on what is wrong with our analyses instead of what is right. This kind of an attitude produces very slow progress. As an example, thirty-seven years have not brought about the use of the mechanism of jaw growth and function concept; while in the meantime not a word has been published condemning any aspect of the precept.From the standpoint of the academician it is commendable to critically study all aspects of growth in all areas of the craniofacial complex, but the intervening local changes are not important to a clinical analysis. It is the overall measurements which are important to the clinical orthodontist. We must make a distinction between the two concepts.
Vertical growth is measured from S-N to the occlusal plane plus the distance from the occlusal plane to the mandibular plane. Only the overall measurement of the mandible is important to the forward and vertical positioning of the chin. It is imperative that our profession understand this.
It is folly to harp on the inaccuracies of the S-N plane. We would estimate that only in very unusual growth would there be more than 1 mm of vertical inaccuracies of nasion, and the horizontal inaccuracies would be inconsequential. It is double folly to find fault with the inaccuracies of Frankfort when we are going to transfer the original Frankfort to subsequent films.
If the nasion inaccuracy were 1 mm vertically, then the point on the line S-N at which vertical growth is measured would be about one half of 1 mm. This would not invalidate a clinical analysis of growth and treatment. Academia must understand this.
We are sure that vertical and horizontal measurements are accurate, otherwise Creekmore in 19671, George Schudy in 19722, Isaacson in April 19773 and September 19774, and Fred Schudy in 19645 and 19776 would not have used the term "exact" to describe the relationship between vertical and horizontal growth. Why did these investigators use the term "exactly" to describe the relationship between posterior horizontal growth and the forward positioning of the chin?
It is important for all aspects of the orthodontic speciallty to understand these relationships so that we can all go forward together.
1Creekmore, T.D., Inhibition and Stimulation of Vertical Growth of the Facial Complex, Angle Orthod. 1967; 37: 285-97. Bibliography
2Schudy, George F., A Longitudinal Cephalometric Study of Post Treatment Growth: Its Implications in Orthodontic Treatment, Am. J. Of Orthod. 1974; 65:39.
3Robert J. Isaacson, D.D.S., Ph.D., Richard J. Zappel, D.D.S., M.S., Frank Worms, D.D.S., M.S.D., Richard R. Bevis, D.D.S., Ph.D., and T. Michael Speidel, D.D.S., M.S.D., The Effects of Mandibular Growth on the Dental Occlusion and Profile, Angle Orthodontist April 1977.
4Robert J. Isaacson, D.D.S., Ph.D., Richard J. Zapfel, D.D.S., M.S.D., Frank W. Worms, D.D.S., J.S.D., and Arthur G. Erdman, B.S., M.S., Ph.D., Effects of Rotational Jaw Growth on Occlusion and Profile, AJO September 1977.
5Schudy, Fred F., Vertical Growth Versus Anteroposterior Growth as Related to Function and Treatment, Angle Orthodontist Vol. 34 No.2, April 1964.
6Schudy, Fred F., Cause and Effect: As Applied to the Growth of the Jaws, p.17A, AJO-DO, VOl 109, June 1996, No. 6.
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