In 1956 I knew nothing about cephalometrics. I started studying a skull and also a skull which had all the bones separated. Lead shots were placed on all conventional landmarks and wires were placed through the canals. Then cephalometric radiograms were taken of the skull. Self teaching is the best method of learning.

When the world conference to determine the value of the cephalogram in clinical practice was held in 1957, I already had a hazy idea of the value and importance of the vertical dimension of the human face. When the results of the conference were published in book form in 1958, I could hardly wait to get my hands on it. It was read with great expectations, and to my amazement, there was not one word about the vertical dimension. Every word spoken from the floor was recorded.

By 1960 the concept was firmly fixed in my mind and I was using it in my practice. It was published in 1964 and 1965 and was designated as a classic in 1991 by the American Association of Orthodontists. This important concept, the Mechanism of Jaw Growth, was developed in a period of four years starting from scratch in post midnight hours by a lot of "blood, sweat, and tears."

Figure 1: Before and after record of a female age 12 to 15 years. The downward movement of the maxillary first molars was largely responsible for 19 mm of anterior facial height, while the lower molars were responsible for none. The orthodontist who treated this patient was aware that Class II elastics would elevate lower molars but was unaware that a cervical face bow, improperly used, would do the same thing. Treatment helped to create a vertical dysplasia of great magnitude.

Fig. 1 This is a treatment record where the cervical face bow, improperly used, caused a very severe vertical dysplasia.

The thing that prompted the study was the fact that my treatment had worsened the facial aesthetics of one of my patients, a dear friend. The patient, a female age 14, was unaware that the "gummie" smile and the muscle strain were due to poor treatment. The treatment procedures used were exactly like orthodontists all over the world were using at that time -- Class II elastics after banding all of the teeth and preparing anchorage. The same treatment procedures were being used for both hypodivergent and hyperdivergent patients. No allowance was made for different facial types. In fact this research that was being done helped to establish the importance of differential treatment according to facial type. The terms hypodivergent and hyperdivergent were established at that time.

Soon we began to notice that anterior dental height (ANS to Me) was greatly increased in many cases. Then we began to notice that lower molar height was greatly increased in many cases. Thus, we began to realize that molar height was the cause of anterior dental height. In retrospect it should have been obvious from the beginning.

Since we did not use cervical headgears, patients of my colleagues were studied. It was observed that cervical headgears, the way they were being used, always moved the teeth to which they were attached, downward markedly. (See Fig. 1) This of course had the same effect as moving the lower molars vertically by Class II elastics.

Fig. 2.

At this point we felt like we had solved the principles of jaw function. Now, the next step was to determine how a given number of mm of condylar growth functioning against a given number of mm of vertical growth of molars would affect the anteroposterior and vertical position of the chin and the rotation of the mandible.

This was when we began to study growth increments and evaluate their effect on the position of the chin and the rotation of the mandible. This was how we found that equal numbers of mm of vertical and horizontal growth cause no rotation of the mandible, and cause the chin to translate forward the exact amount of the horizontal condylar growth. Also it was found that when condylar growth exceeded vertical molar growth the mandible rotated forward; and when vertical molar growth exceeded condylar growth the mandible rotated backward. Dr. Creekmore, my associate at the time, discovered that the chin translated forward the exact amount of the horizontal condylar growth.

Inhibiting vertical growth has the same effect as causing the condyle to grow. See Fig. 2A, 2B, and 2C. The maxillary first molars were extracted at age 10 years. This was long before the maxillary 2nd molars, bicuspids and cuspids erupted into occlusal contact. The removal of the molars instantly brought about contact of the upper and lower incisors, instantly corrected the tongue thrust, also corrected the act of swallowing, and partially corrected the functional strain of the paraoral musculature.

Fig. 2. This is a treatment record where upper first molars were extracted to reduce vertical height.

The force of occlusion presumably prevented the eruption of the posterior teeth and allowed the symphysis to move upward four millimeters. Condylar growth moved the symphysis forward eight and one half millimeters.

The second molar was positioned three millimeters closer to the cranial base than the first molar which was extracted. The maxillary third molars were moved forward to take the place of the second molars. Again, these procedures permanently corrected the open bite, the tongue thrust, and the muscle strain.

For the benefit of the younger members, those metal objects on the teeth are known as "bands"?? The photo of the appliances shown are not the same patient. It is shown to demonstrate the "short" Class II elastics used to correct the malocclusion. The L-shaped elastic, attached anterior to the center of gravity of the mandible, exerts force even when the teeth are in occlusion.

At this point we felt like we understood the principles of the mechanism of jaw growth and had established principles of treatment based on this knowledge. To this day some of our leaders believe that we know nothing about cause and effect. To this day nobody has published anything that we have seen which would indicate that they have measured growth increments, except Creekmore¹, George Schudy², Isaacson^{3 & 4}, and Fred Schudy⁵. It is a mystery to me why investigators do not measure basic growth increments -- the building blocks. It is the only way that accurate knowledge and understanding of growth can be obtained.

In conclusion I would like to say that I feel very humble about what I have been able to contribute to our beloved profession.

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Bibliography

¹Creekmore, T.D., Inhibition or Stimulation of Vertical Growth of the Facial Complex, Angle Orthodontist 1967; 37: 285-97.

²Schudy, G.F., A Longitudinal Cephalometric Study of Post-Treatment Craniofacial Growth: Its Implications in Orthodontic Treatment, Am. J. 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.

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