The guidance of eruption without extraction.

The guidance of eruption by serial extraction is a well known procedure in orthodontics. The therapeutic principle consists in diminishing the bony resistance near the erupting tooth, which will then defl ect in the direction of the extraction site. The problem which will be discussed in this paper is whether we might guide eruption without extraction. It is generally suggested that, after clinical eruption, the forces of cheeks, lips and tongue play an important role in determining the ultimate labiolingual and buccolingual tooth position. However, Scott (1961) states that, the opinion that the teeth are aligned in a state of balance between the forces of cheeks, lips and tongue is a hypothesis which requires to be substantiated by experimental evidence. He states ‘ it should, for example, be easy to design an experiment in which cheek pressure is withheld from acting on a labially displaced canine, and observe whether in such cases the tooth remained in the displaced position ’ . In my opinion, function correctors meet all requirements for an experimental device to conduct such experiments. In order to test if the position of teeth may be changed solely by eliminating cheek pressure, measurements were made from upper study models taken before and after treatment (Mosch). The casts were not selected by criteria other than narrowness in the upper jaw but all types of malocclusions were represented in this study. The sample consisted of children who were treated with function regulators alone. There was no force acting upon the premolars and molars other than the tongue. Although this work wil1 be published in detail elsewhere, provisional measuring results of 400 cases have shown that merely by withholding the cheek pressure a spontaneous widening of the dental arch could be observed with great regularity, and to an extent which coincides approximately with the norm of Pont’s index. The increase of the distance between the fi rst deciduous molars, fi rst premolars and the fi rst permanent molars in the maxilla is given in Table 1 . The mean value of the interval between the fi rst and second measurements refl ect the dates when the models were obtained. Actually, the expansion was generally achieved much earlier. These data, as a result of careful measurements,