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Traditionally, the orthodontists evaluate the modifications made by the general growth of the face by superimposing "as well as possible" (best fit) the serial head-films of beginning and end of treatment on easily locatable anatomical points of the cranial base. Many authors showed that this evaluation method of the development of the facial skeleton is vague and thus generator of considerable errors of appreciation. The process of superimposition of profile head-films on stable structures of the former base of cranium rests primarily on the observation made by De Coster in 1952 on "the immutability of the basi-cranial line", confirmed histologically by Melsen in 1971. In 1972, the longitudinal studies undertaken by Björk and Skieller using metal implants on more than 200 cases highlighted the stability of certain anatomical structures within the maxilla and the mandible. The "Structural Method" of general and local superimpositions, thus developed starting from these discoveries, brought a new vision of the different facial growth patterns and allowed a greater comprehension of the effectiveness of the orthodontic techniques., (© L'Orthodontie Française, Paris, 2006.)