The term paradigm has become a popular one in recent orthodontic publications. By definition, a paradigm is a body of basic knowledge from which new knowledge is generated.
In a discussion of the growth of the jaws, it is imperative that we identify the most basic elements of growth, not their effects.
All the growth analyses of which I am aware are based on the effects
of growth elements.
The strictly basic
elements of growth are the growth increments, the building blocks
. When we speak of the annual downward movement of the occlusal plane and the movement of the chin, we are speaking of the effects
of growth. We are comparing a later stage of growth to an earlier stage. What we must do is identify the increments or building blocks that produce this downward movement of occlusal plane and the change in the position of the chin. Also we must identify the relationship between these increments.
It seems obvious that we need to change the paradigm
! The correct paradigm is that the vertical and horizontal growth of mandibular condyles plus the vertical and horizontal movement of the temporomandibular joint has a causal
relationship with the vertical growth of the molar teeth; and this relationship determines the horizontal and vertical movement of the chin as well as the rotation of the mandible. All this growth activitiy has a critical
effect on the treatment of malocclusion.
As an example, if the chin moves downward 4 mm and forward 6 mm without the mandible rotating, we can calculate the growth increments that caused
this change. We know that there has been 4 mm of vertical molar growth, 4 mm of vertical condylar growth, and 2 mm of horizontal condylar growth. How do we know
this? By studying thousands
of cases we found that when vertical and condylar growth equals vertical molar growth, the mandibular plane remains parallel to its original inclination and the mandible is translated forward the exact
amount of the horizontal condylar growth. This is a mechanical and mathematical relationship, having nothing to do with biology. It has been shown graphically many times. This concept has been verified by the work of Isaacson.
In 1960, these building blocks were identified and their contribuation to facial form was pointed out. The research was published in detail in 1964 in the Angle Orthodontist.
During the intervening years, these principles have been discussed repeatedly in the publications. It has now been 32 years, and I wonder how much longer will be required before these principles will be used by investigators in the discussion of growth. To my knowledge, no one in the United States has published anything that would indicate that they have specifically measured growth increments except Creekmore, George Schudy, Isaacson and me. Creekmore's thesis was published in 1967 and Schudy's thesis was published in 1972. I would be interested in the reaction of others.