RESUMO
To investigate the permeability of the dental enamel of erupted and unerupted human pre-molars and its variation with depth, we determined the resistivity of successive 100-micron-thick layers. The electrical resistance of halved tooth crowns at zero Hertz, which according to Scholberg et al. (1982, 1984) is inversely related to the permeability, was measured before and after removal of successive enamel layers from the outer surface toward the dentino-enamel junction (D.E.J.). The resistivity of the successive enamel layers increased from the D.E.J. toward the outer surface in approximately the same way in erupted as well as in unerupted pre-molars, except within the outermost layer of 100 to 200 microns thickness. The resistivity of this layer in erupted pre-molars was considerably higher than that in unerupted pre-molars, which may be due to post-eruptive mineralization.
Assuntos
Permeabilidade do Esmalte Dentário , Esmalte Dentário/ultraestrutura , Permeabilidade Dentária , Dente não Erupcionado/ultraestrutura , Adolescente , Dente Pré-Molar , Criança , Esmalte Dentário/metabolismo , Esmalte Dentário/fisiologia , Dentina/fisiologia , Dentina/ultraestrutura , Condutividade Elétrica , Eletroquímica , Humanos , Erupção Dentária , Dente não Erupcionado/metabolismo , Dente não Erupcionado/fisiologiaRESUMO
Surgical exposure may be an integral part of orthodontic treatment of impacted teeth. In some cases the surgical procedure alone results in eruption and alignment of such teeth. The nature of the mechanism that starts concomitantly with the removal of covering tissues is not known. The aim of this investigation was to study factors associated with eruption as well as the eruption route of impacted and unerupted teeth following surgical exposure. The material consisted of 542 impacted teeth in 389 patients. The findings given strong support to the hypothesis that forces within surrounding tissues act upon the exposed crown in such a way as to direct it toward the area where the tissues were removed.
Assuntos
Erupção Dentária , Dente Impactado/fisiopatologia , Adolescente , Adulto , Criança , Feminino , Humanos , Masculino , Métodos , Rotação , Migração de Dente/fisiopatologia , Dente Impactado/patologia , Dente Impactado/cirurgia , Dente não Erupcionado/anatomia & histologia , Dente não Erupcionado/fisiologia , Dente não Erupcionado/cirurgiaRESUMO
(1) Third molar genesis may occur up to the age of sixteen years, although the possibility of their appearance after the age of twelve years is reduced. (2) When third molar genesis is delayed beyond the age of ten years, the possibility of all four third molars developing is reduced by about fifty percent. (3) The intraindividual variability in stage of development of third molars increase when genesis is delayed beyond ten years of age. (4) There is no significant difference in size of early and late developing third molars.
