Читать книгу Orthodontic Treatment of Impacted Teeth - Adrian Becker - Страница 20

Based on the principles set out by Grøn [13], it has been widely accepted that, under normal circumstances, a tooth erupts with a developing root and with approximately three‐quarters of its final root length. Typically, when they erupt the mandibular central incisors and first molars will have marginally less root development, whereas the mandibular canines and second molars will demonstrate slightly more root development. This is now generally accepted as a diagnostic baseline from which to evaluate the eruption of teeth in general.

Thus, where an erupted tooth shows less root development (Figure 1.7), it would be appropriate to label it as prematurely erupted. (This will usually be the consequence of the early loss of a deciduous tooth, particularly where extraction was dictated by the presence of periapical pathology, typically due to untreated caries.)

Fig. 1.7 The left mandibular premolars are prematurely erupted, with insufficient root development, due to premature extraction in a caries‐prone dentition.

Conversely, where an unerupted tooth exhibits a more completely developed root, then the eruption process of this tooth must be presumed to have been impeded. (This may have been caused by any one of several aetiological possibilities, such as a failure of resorption of the roots of a deciduous tooth, or an abnormal eruptive path, the presence of a supernumerary tooth, or dental crowding, perhaps a much‐enlarged dental follicle/dentigerous cyst, or indeed any other forms of soft tissue pathology or disturbance in the eruption mechanism of the tooth.) One should not overlook the possibility that the cause of the non‐eruption may also be a thickened post‐extraction or post‐trauma repair of the mucosa.

It is to be noted that if there is a history of very early extraction of one or two deciduous molars, we may find that there will be a substantial delay in the eruption of the premolars, indeed, even complete non‐eruption, caused by a thickened mucosa overlying the teeth. It is usually possible, for a period of a year or more, to palpate these teeth by virtue of their distinct outline being clearly visible and causing a bulging of the gum. However, eruption may not occur at all.