Melvin L. Moss, D.D.S., Ph.D., and Letty Salentijn, D.D.S.
New York, N. Y.
During the past decade the method of functional cranial analysis has been developed in our laboratory. The basic postulates and the experimental and clinical supporting data have been published extensively elsewhere.4-29 The orthodontic specialty recently becameaware of this analytical technique, with particular interest being expressed in the derivative concept of the functional matrix. In view of the current reappraisal of the theories of cranial bone growth by many workers (Scott30 and Enlow2), it is appropriate to indicate the contribution which the analytical method makes toward the resolution of this problem. The present review first defines the twobasic types of functional matrices (periosteal and capsular) and then demonstrates their differing and yet complementary roles as the primary morphogenetic agencies in skeletal tissue growth.
Functional cranial analysis
A brief review of basic postulates is necessary. Operationally, the head is a region within which certain functions occur. Every function is completely carried out by afunctional cranial component. Each such component, in turn, is composed of two parts: (1) a functional matrix which actually carries out the function and (2) a skeletal unit whose biomechanical role it is to protect and/or support its specific functional matrix. Abundant data demonstrate that all growth changes in the size, shape, and spatial position and, indeed, the very maintenance in being, of allskeletal units are always secondary to temporally primary changes in their specific functional matrices. To clarify this seemingly sweeping statement, it is necessary to define the terms skeletal unit and functional matrix in greater detail.
Skeletal units may be composed variably of bone, cartilage, or tendinous tissues. They are not the equivalents of the "bones" of formal, classic osteology. Whensuch a "bone" consists of a number of skeletal units, we call them microskeletal units; that is, both the maxilla and the mandible are formed of a number of such contiguous microskeletal units. When adjoining portions of a number of neighboring "bones" are united to function as a single cranial component, we term this a macroskeletal unit; the endocranial surface of the calvaria is an example.In the mandible we distinguish easily a coronoid microskeletal unit related to the functional demands of the temporalis muscle; an angular microskeletal unit related to the activity of both the masseter and medial pterygoid muscles; an alveolar unit related to the presence and position of teeth; and a basal microskeletal unit related to the inferior alveolar neurovascular triad matrix. There areother mandibular microskeletal units which have been detailed elsewhere.12,14 To a variable extent, contiguous microskeletal units are independent of each other. This implies that changes in the size, shape, or position of the coronoid process as a result of primary changes in temporalis muscle are relatively independent of such changes in other mandibular microskeletal units.
The term functionalmatrix is by no means equivalent to what is commonly understood as "soft tissues," this is, muscles, glands, nerves, vessels, fat, etc., although all of these are obviously included within the concept. Teeth are also a functional matrix, as the experience of every dentist can attest empirically. Indeed, most orthodontic therapy is based firmly on the fact that when this functional matrix grows oris moved, the related skeletal unit (the alveolar bone) responds appropriately to this morphogenetically primary demand. However, the term functional matrix is more inclusive still. There exists a further group of matrices among which the functioning spaces of the oronasopharyngeal cavities figure importantly.
Work in our laboratory increasingly indicates a fundamental difference between two...