Welisss

The primary role of functional

matrices in facial growth
Melvin 1. Moss, New York, N. P. D.D.S., Ph.D., and Letty Salentijn, D.D.S.

uring 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-“Y The orthodontic specialty recentlybecame aware of this analytical technique, with particular interest being expressed in the derivat,i\-e concept of the Jurrctionul matrix. In view of the current reappraisal of the theories of cranial bone growth by many workers (Scott3” and EnlowZA), it is appropriate to indicate the contribution which the analytical method makes toward the resolution of this problem. The present review first definesthe two basic types of functional matrices (periosteal and capsular) and then demonstrat.es their differing and yet complementary roles as the primary morphogenetic agencies in skeletal tissue growth.
Functional cranial analysis

D

A brief review of basic postulates is necessary. Operationally, the head is a region within which certain functions occur. Every function is completely carriedout by a functional cranial conaponed. 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 inbeing, of all skeletal units are always secondary to temporally primary changes in their specific functional matrices. To clarify this seemingly sweeping statement, it is necessary to define t,he terms skeletal unit and functional matrix in greater detail.
From the Department Division of of Anatomy, Oral Biology, College of School Physicians of Dental and and Surgeons, (NB-00965) of Health. OralSurgery, and Columbia University. from the National the

This study was aided, Institute of Neurological

in part, by a research grant Diseases, National Institutes

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Skeletal units may be composed variably of bone, cartilage, or tendinous tissues. They are not the equivalents of the “bones” of formal, classicosteology. When such a “bone” consists of a number of skeletal units, we call them microskeletal units; that is, both the maxilla and the mandible arc 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 cndocranial surface of the calvaria is anexample. In the mandible we distinguish easily a coronoid microskclctal unit related to the functional demands of the temporalis muscle; an angular microskelet,al 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 matrixThcrc are other mandibular microskeletal units which have been detailed elsewhcre?~ I4 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 termfunctionaZ ma,t,rix 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...