Does fixed retention prevent overeruption of unopposed mandibular second molars in maxillary first molar extraction cases?

Over-eruption in marsupial carnivore teeth: compensation for a constraint

Pronounced over-eruption of the canine teeth, causing the cervical enamel margin to extend beyond the alveolar bone and exposing the root, occurs with age and growth in Australian marsupial carnivores, much more than in eco-morphologically equivalent placental carnivores. Suppression of functional tooth replacement is characteristic of marsupials, where most placentals have the primitive diphyodont pattern of two generations of incisor, canine and premolar teeth. Canine and molar tooth dimensions of four species of marsupial carnivores (thylacine Thylacinus cynocephalus, Tasmanian devil Sarcophilus harrisii and two quolls Dasyurus spp.) and canine dimensions of seven eco-morphologically equivalent placental carnivore species were measured from museum specimens. Canine dimensions were measured in a time series on live wild-living individual devils and quolls. The canine teeth and to a lesser extent the molar teeth of marsupial carnivores continue to erupt through life, resulting in a net increase in tooth height and diameter, a phenomenon not evident in placental carnivores. Potential mechanisms causing over-eruption include tooth wear and gradual release of occlusal pressure as the individual grows. Over-eruption in marsupial carnivores may be a compensatory response for tooth size limits imposed by monophyodont tooth replacement, ensuring that animal's teeth are scaled to jaw size from juvenile to adulthood.

The extraction of first, second or third permanent molar teeth and its effect on the dentofacial complex

The extraction of permanent molar teeth was first introduced in 1976 as a substitution for premolar extraction in cases with mild crowding. Since then, a number of studies have investigated the effect of permanent molar extraction on dentofacial harmony. Undertaking the procedure of molar extraction is most commonly recommended in response to factors such as: gross caries, large restorations and root-filled teeth, along with its application in the management of anterior open bite and reduction in crowding in facial regions. It has been indicated, however, that before undertaking the extraction of molar teeth it is important to investigate the potential influence of the procedure on other molars, with particular consideration of their eruption path. This is due to the doubt as to the effect of the exact molar teeth extraction and their consequences. In light of this, This review was undertaken to investigate and compare the effect of first, second and the third molar teeth extraction and their subsequent dentofacial complex changes.