Chapter 1

Introduction and Justification

1.1 Some historical remarks

The first important publications about growth of the face appeared in England in the second half of the 18th century. The greatest contribution came from John Hunter,126 who gathered his information primarily from human skeletal material (Fig. 1-1). Hunter suggested, among other things, that the corpus of the mandible became longer by resorption of the bone on the anterior surface of the ramus and bone apposition on the posterior border. In addition, he sought to support his concepts with animal experiments. To that end he made use of the phenomenon accidentally noticed by Belchier25 that, in live animals, madder (alizarin) stains the areas where new bone is formed. Humphry123 studied the growth of the mandible by inserting metal wires in the mandibles of young pigs (Fig. 1-2). This approach previously had been used by Duhamel72 in long bones. Both vital staining and insertion of metal implants are techniques which are still used in the study of the growth of the facial skeleton.

A special method for the study of bone growth has been developed by Enlow.76 He indicated the possibility of distinguishing the areas on bone where either endosteal or periosteal apposition has occurred. Bone tissue reveals its own history. In this manner Enlow and his coworkers78 79 could give a detailed account of the remodeling processes in the mandible, the maxilla, and other bones. By working back to establish the succession in which histological changes had occurred, they were able to come to conclusions similar to those reached by other researchers such as Hunter126 and later Brash45 from the results of experiments with vital staining in animals. Their findings substantiated the theory proposed by John Hunter that bone growth does not occur interstitially, but is a mechanism of surface apposition and resorption. Above all, Enlow clearly demonstrated that through a balanced interplay between those two processes the bones maintain their proper proportions in growth.

Although research into the dried skull had provided much data on the growth of the head313 135 111 it gave no information concerning individual changes and variations. This was made possible through the introduction of longitudinal studies, wherein the same individuals were observed and measured on successive occasions.98 112 The intrinsic possibilities of the method increased considerably with the introduction of radiography, which among other things, made possible standardized pictures of the head.48 49 Not only could these be used to observe internal structures and quantify their growth, b/>